Computer-assisted surgical navigation was designed to reduce the rates of acetabular component malpositioning, a common cause for revision following primary total hip arthroplasty (THA). We compared intraoperative measures such as radiation exposure, radiographic acetabular cup placement, and outcomes of patients who underwent a THA using computer-assisted surgical navigation with augmented reality (AR) compared to those who underwent traditional manual THA with fluoroscopic assistance (FA).

We retrospectively reviewed 115 hips who underwent primary direct anterior THAs using the intraoperative AR surgical navigation system between 3/30/2021 and 12/30/2022. These were compared to a matched cohort of 115 primary THAs performed with FA through a direct anterior approach during the same time period. Patients were matched based on age, gender, American Society of Anesthesiologists score (ASA), and BMI. Goal inclination and anteversion were set to 42° (°) and 22°, respectively.

THA with AR patients had decreased intraoperative radiation exposure (mean 2.0 versus 3.2 mGy, p < 0.001) and radiation time (mean 0.2 versus 0.4 min, p < 0.001). Deviation from the preoperative plan was similar between AR and FA for both radiographic inclination and anteversion. There was no difference in the operative time, estimated blood loss, or reoperations, all of which were for infection (1.7 versus 0.0 %, p = 0.5).

AR surgical navigation in primary THA has similar radiographic, operative and clinical results as THA with intraoperative FA. However, AR surgical navigation is associated with decreased intraoperative fluoroscopic radiation and time. Further research is needed to evaluate accuracy of acetabular component positioning and complications.

This study evaluates how a computed tomography-based mixed-reality (MR) navigation system impacts acetabular component orientation compared to freehand positioning in total hip arthroplasty.

A series of 79 patients who underwent total hip arthroplasty utilizing a computed tomography-based MR navigation system were reviewed. The surgeon initially placed the acetabular cup freehand, attempting to achieve the preoperative plan, and this initial intraoperative orientation was recorded. The cup was then adjusted to the planned position. The difference between freehand and planned tilt-adjusted operative anteversion (OA) and inclination (OI) determined the navigation tool's impact.

The mean preoperative planned OA was 30.1 ± 2.0 (range: 25, 35) degrees, and the mean freehand intraoperative OA was 30.2 ± 9.1 (range: 4, 57) degrees (P = .885), requiring a mean adjustment of 6.8 ± 5.1 (range: 0, 23) degrees. Freehand OA was corrected at least 5 degrees in 54.4% (43/79) of cases. The mean preoperative planned OI was 40.8 ± 0.6 (range: 39, 42) degrees, and the mean freehand intraoperative OI was 37.8 ± 6.6 (range: 18, 53) degrees (P < .001), requiring a mean adjustment of 5.7 ± 4.5 (range: 0, 22) degrees to achieve. Freehand OI was corrected at least 5 degrees in 43.0% (34/79) of cases.

Freehand acetabular component positioning in the lateral position is variable when attempting to execute patient-specific numerical cup orientation targets. Use of this navigation tool led the surgeon to correct more than 5 degrees in both OA and OI in roughly half of the hips.

Enabling technology, such as computer navigation and robotics, provides more precise implant position, which allows surgeons the ability for personalized alignment in total hip arthroplasty (THA). To date, THA implant position studies have focused on dislocation rates, rather than on patient-reported outcome measures (PROMs). This study evaluated the impact of the THA component position on clinically significant differences in PROMs.

A total of 1,682 consecutive primary THAs were retrospectively reviewed. Acetabular and femoral component position as well as femoral offset and leg length discrepancy (LLD) were measured on all preoperative and postoperative radiographs. Modern PROM scores were evaluated. Minimal clinically important difference (MCID), substantial clinical benefit (SCB), and patient-acceptable symptom state (PASS) values were assessed for applicable PROMs. Univariate and multivariate statistical analyses were performed with P < 0.05 as significant. The mean clinical follow-up was 21.9 months (range, one to 128).

In multivariate analysis, the acetabular component position closer to the native hip center of rotation was associated with a greater probability of achieving the Hip disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS JR), MCID, SCB, and PASS thresholds (P ≤ 0.008). An increase in postoperative femoral offset was associated with achieving the MCID for the University of California Los Angeles (UCLA) activity level and patients being 'very satisfied or satisfied' (P ≤ 0.004). The mean postoperative LLD was 3.8 mm (range, 24.5 mm short to 36.6 mm long); however, postoperative LLD was NOT a predictor of PROMs (P ≥ 0.167) with statistical power ≥ 87%.

Study results demonstrated that replicating the native center of rotation and optimizing femoral offset was associated with clinically relevant improvements in PROMs. Interestingly, in this large cohort, leg-length inequality was not associated with PROMs. Further research is warranted on THA component position, including spino-pelvic parameters and PROMs.

Instability after total hip arthroplasty (THA) remains a challenging problem. Component revision or bearing exchange can be successful; however, constraints may be necessary. This study evaluated the results of revision THA for instability that required constrained liners (CL) to determine whether revising or retaining the acetabular component is preferred.

This single-surgeon, retrospective study included 50 consecutive patients who required CL during acetabular revision for instability. Indications for constraint included the absence of functioning abductors and failed previous CL or dual mobility. A CL was used in existing cups if the cup position was deemed acceptable with a reasonable impingement-free arc of motion. If unacceptable, it was revised, or, if the internal diameter allowed, a CL was cemented into the existing cup in a "face changing" (FC) position to minimize impingement. All patients had a minimum 2-year follow-up. Recurrent instability occurred in 15 of 50 patients overall (30%). Results were analyzed based on if the cup/liner position was changed: Group 1 - Cup revision, or cemented CL with "face change" (n=28); Group 2 - CL implanted into existing cup without FC (n=22).

Group 1 had recurrent instability in four of 28 (14%), while Group 2 had instability in 11 of 22 (50%) (P=0.012). Cemented liners with FC failed in four of 16 cases. Cup revision had the lowest rate of recurrent instability (0 of 12) versus 15 of 38 (39%) when the cup was retained (P= 0.01).

This study demonstrated significantly lower rates of recurrent instability when CLs can be positioned to minimize impingement, either by revising the cup or cementing the liner independent of the existing cup: a so-called "face-change." Cup revision demonstrated the lowest rate of recurrent instability with predictable osteointegration at the mean 4-year follow-up.

Prosthetic impingement after total hip arthroplasty (THA) has been associated with instability and may be a cause of accelerated polyethylene wear and pain. Previous retrieval studies report a high prevalence of impingement in acetabular liners. Robotic technology has the potential to reduce THA instability as it enables technical precision and optimizes implant positioning. However, whether robotics can improve impingement prevalence is unknown. Thus, the objectives of this study were to: (1) determine the prevalence and severity of acetabular liner impingement with robotic navigation; and (2) compare impingement prevalence with a control cohort of manually placed THA liners.

There were 18 robotic-assisted liners and 11 non-robotic controls scored for the presence and severity of impingement. Radiographic measurements of acetabular inclination and anteversion were assessed using prerevision standing radiographs. Femoral head size (36 being the most common), length of implantation, revision indication, age, gender, and body mass index were recorded.

Of the robotic liners, 61% showed impingement, while 45% of the non-robotic liners showed impingement (P = 0.14). The robotic group demonstrated a lower variance of inclination (robotic: 41.7° ± 3.9, control: 42.8° ± 7.1, P = 0.64) and lower anteversion variance (robotic: 22.8° ± 2.8, control: 20.8° ± 7.9, P = 0.43), but mean values did not differ between the groups. Impingement presence and severity were not related to head size, length of implantation, or other demographic variables.

This study suggests that the use of robotic-assisted technology employing modern-day implants with larger diameter heads does not reduce the prevalence or severity of prosthetic impingement in retrieved acetabular liners from revision THA.

This study aimed to explore whether total hip arthroplasty (THA) aided by full-process robotics was effective in patients undergoing developmental dysplasia of the hip (DDH).

Totally 112 patients were enrolled and classified into robotic-assisted group (n = 56) and the conventional group (n = 56). In addition, retrospective analysis was used for comparing the difference in therapeutic efficacy.

A total of 112 patients received THA, and were followed up for (12.78 ± 0.76) months on average, with no occurrence of associated complications. For patients in robot-assisted group, their abduction and anteversion angles of acetabular cup placement were in the safe zone, while those in 8 patients of the conventional group were outside the safe zone. Compared to the conventional group, the robot-assisted group had higher postoperative Harris Hip Score and FJS, whereas lower VAS score.

Robot-assisted THA is advantageous in terms of both intraoperative precision and postoperative effect on the treatment of patients with DDH.

Total hip arthroplasty (THA) has been among the most successful procedures in medicine, but the preferred approach and use of enhancing technologies are evolving. This study was conducted to define current THA practice (surgical approach and use of enhancing technologies) among early-career and more experienced surgeons. A secondary goal of this study was to identify differences in 6-month Patient-Reported Outcome Measurement Information System (PROMIS) pain interference or function scores and early complications.

In 2022 and 2023, 35,068 THAs were submitted to the American Board of Orthopaedic Surgery by candidates for the part II oral certification examination (14,993) and by Diplomates as part of the recertification process (20,075). The average patient age was 66 years, and 54% of patients were women. Baseline and 6-month PROMIS pain interference and function surveys were obtained from 2,019 patients in the Part II group. Postoperative complications were reported by the candidates or diplomates for all patients.

Part II candidate surgical approach was direct anterior (DA) (69%), posterior (26%), direct lateral (2%), and other (2%). For recertification candidates, the surgical approach was DA (43%), posterior (43%), direct lateral (6%), and other (7%). Robotics or navigation was utilized in 18 and 15%, respectively. There were equivalent improvements in the PROMIS function in all groups. The surgeon-reported significant surgical complications were higher in part II candidates (8.4%) than in candidates undergoing recertification (2.7%, P < 0.001), with bone fracture the most common in each group (part II: 2.3%; recertification at 0.6%).

The part II candidates are more likely to utilize the DA approach compared to recertification candidates. The Part II candidates report higher rates of postoperative complications. However, there was no difference in the rate of surgeon-reported surgical complications or fractures based on surgical approach. Robotics and navigation are utilized in less than 20% of THA cases. The PROMs improved equally in all THA groups.

Different methods can help to optimise sagittal cup orientation in total hip arthroplasty (THA) based on individual spinopelvic characteristics. This study aimed to: (1) assess how often combined sagittal index (CSI) and hip-spine-classification targets were achieved post THA; (2) compare anteversion/inclination between cups in-/outside optimal CSI zone; and (3) determine association with outcome.

This is a multicentre, prospective, case-cohort study of 435 primary THA for osteoarthritis (53% females; age: 65 ± 12 years; follow-up: 2.4 ± 0.6 years) (58% lateral, 29% anterior, 13% posterior approach). No robotics or dual-mobility were used. Patients underwent spinopelvic radiographs to measure parameters including lumbar lordosis (LL), sacral slope (SS), pelvic tilt (PT), pelvic incidence (PI), pelvic femoral angle (PFA), and ante-inclination (AI) on lateral spinopelvic radiographs. Unbalanced spine was defined as PI - LL ⩾ 10° (PI: pelvic incidence; LL: lumbar lordosis), stiffness as ∆LL < 20°. Optimal cup orientation was based on CSI targets: 205-245° for balanced spine (n = 327), or 215-235° for unbalanced spine (n = 108), hip-spine classification targets (±5°), and conventional inclination/anteversion (40/20° ± 10°) target. Patient-reported outcome was measured using Oxford Hip Score (OHS).

CSI targets were achieved in 60% (n = 261/435), whilst 44% had cup position within hip-spine classification targets (n = 125/284). Anteversion was higher among cups within CSI targets (26° ± 8° vs. 22° ± 10°; p < 0.001). Overall dislocation rate was 0.9% (n = 4/435), without difference whether CSI targets were achieved (0.4% vs. 1.7%; p = 0.178). Postoperative OHS was better among those within CSI targets (42 ± 8 vs. 40 ± 9; p = 0.003) or within hip-spine-classification targets (p = 0.028), but not according to conventional orientation (p = 0.384).

Awareness of adverse spinopelvic characteristics and using sagittal characteristics (especially CSI) can help surgeons to achieve optimal cup orientation, improving outcome and reducing dislocation risk post-THA.

Maintaining appropriate soft tissue tension is essential in total hip arthroplasty (THA). Surgeons generally achieve this by altering the neck length. However, experimenting with different neck lengths is time-consuming, as it requires repeated hip dislocations. To address this, we have used a new extensible trial neck device that allows for easy adjustment of neck length during surgery. This device can help surgeons avoid the need for repeated hip dislocations to determine the correct neck size. The objective of this research was to investigate whether this device could help shorten operative times and decrease surgical invasion for patients.

Patients undergoing THA were randomly separated into two groups. The first group used the extensible trial neck during trial reduction after the stem and cup were placed (group M), while the second group used a conventional trial neck (group C). Operative time, blood loss, number of additional dislocations needed during the operation, and C-reactive protein (CRP) and creatine phosphokinase (CPK) levels after the operation were compared.

Operative time was significantly shorter and the number of additional dislocations required to choose the final neck size was significantly lower in group M compared with group C. No significant difference in blood loss was observed. CRP and CPK levels days 3 and 7 after surgery decreased in group M compared with group C.

The extensible trial neck was useful for THA by greatly reducing operative time and stress on the patient. [Orthopedics. 2025;48(2):e88-e93.].

Spinopelvic characteristics change after THA. Whether this change varies between approaches, is of interest for pre-op cup orientation planning. The aims of this study were to (1) Characterize changes in standing PT amongst patients with hip osteoarthritis treated with THA; (2) Test whether certain patient-related factors may predict PT change; and (3) Assess the association between surgical approach and PT change.

This was a prospective, two-center, radiographic outcome study including 424 hips, consisting of anterior approach for 171 (40.3%) hips, lateral approach for 181 hips (42.7%) and posterior approach for 72 hips (17.0%). Spinopelvic characteristics were determined from lateral radiographs (before and one year after THA). Parameters of interest included: Pelvic tilt (PT), lumbar lordosis, sacral slope, pelvic incidence. PT change of more than 7 ° was considered clinically relevant.

Pelvic tilt increased by 2 ° from 15.1 ° (± 8.9) to 17.1 ° (± 9.7) after THA (p < 0.001). 19 hips (4.5%) experienced a relevant PT decrease, 337 (79.5%) had no clinically significant change in pelvic tilt, and 68 (16.0%) showed a moderate increase. Age, female sex and preoperative spinopelvic parameters including PT, SS and PI were predictive of PT change more than 7 °. PT increased most with lateral approach (2.9 ± 6.2) and least with anterior approach (1.1 ± 6.2, p = 0.024).

Preoperative PT is the best predictor for PT change. PT is generally normalizing after THA and patients with low PT due to hip flexion contractures tend to increase PT after THA, few patients with high PT will decrease after THA. Anterior approach with capsulectomy was associated with the least change in PT post-THA. However, the approach-specific changes, although statistically significant, were too small to be considered during clinical practice, therefore no approach-specific prediction of PT change needs to be considered during preoperative planning for primary THA.

As the number of patients undergoing both total hip arthroplasty (THA) and lumbar spinal fusion rises, clinicians must gain a stronger understanding of the biomechanical and clinical associations between these two procedures. This study compared single versus multilevel spinal fusion on spinopelvic parameters, clinical outcomes, and THA dislocation rates in patients with existing THAs.

Patients with an existing THA undergoing elective spinal fusion were retrospectively identified at a single academic center. Cohorts were stratified by fusion construct length (single or multilevel) and outcomes were followed at least 1 year after surgery.

A total of 392 patients (260 single level, 132 multilevel) were included. Patients who underwent multilevel fusion had less improvement in ∆ visual analogue scale (VAS) Back Scores at 1 year (-1.00 vs. -2.50, P = 0.039), greater hospital length of stay (5.00 vs. 3.00 days, P < 0.001), and lower rates of discharge home (48.5% vs. 81.4%, P < 0.001). They had higher dislocation (4.55% vs. 0.38%, P = 0.007), spinal revision (25.8% vs. 13.5%, P = 0.004), and 90-day readmission rates (12.1% vs. 3.46%, P = 0.002). Radiographically, patients with multilevel constructs had lower preoperative (40.4° vs. 49.1°, P < 0.001), postoperative (43.4° vs. 48.6°, P = 0.004), and 1-year lumbar lordosis (44.4° vs. 50.5°, P = 0.028) and higher postoperative mean anteversion (24.2° vs. 21.0°, P = 0.017). Single-level fusion was an independent predictor for lower VAS leg scores (odds ratio [OR] = -2.57, P = 0.011), fewer readmissions (OR = -0.13, P = 0.001), and fewer complications (OR = -0.25, P < 0.001). Male sex independently predicted increased spinal revisions (OR = 0.13, P = 0.026).

Patients with prior THA undergoing multilevel fusions experienced more dislocations, higher spinal revisions, less frequent discharge home, longer hospital length of stays, and higher 90-day readmission rates. They had less improvement in ∆VAS Back Scores at 1 year, lower lumbar lordosis, and greater anteversion. Patients with existing THA undergoing multilevel fusion have more abnormal spinal sagittal balance and higher risk of dislocation despite higher baseline and postoperative acetabular anteversion.

A systematic literature review and meta- analysis.

To extract and combine the available literature focused on normal and abnormal biomechanical principles of spine-pelvis-hip complex and to sum up the data in the application of THA both in the setting with and without spinal disorders.

An extensive search and analysis of the articles was done by 3 authors independently in 7 platforms based on PRISMA and MOOSE guidelines. Selection criteria 1. Articles that assessed spinopelvic parameters (SS, SPT, PI, and acetabular cup orientation) in patients undergoing THA, Articles that assessed balance in spinopelvic complex after THA, Randomized control studies, Systematic literature reviews, Meta-analyses, Clinical trials / original research studies, Review articles and Articles after 2015 were included. Cochrane's GRADE method was used to define the level of evidence. 2.Participants: Patients who underwent THA only (in asymptomatic spine), those who had ankylosing spondylitis and underwent THA and those who underwent THA with prior spinal arthrodesis. 3.Study parameters: Ante Inclination (AI), sacral slope (SS), pelvic Incidence (PI) and spinopelvic tilt (SPT) in both positions of standing and sitting. ΔAI, ΔSS and ΔSPT. Data were collected and analyzed, the means of the study parameters with SD were calculated and a meta-analysis is performed to evaluate the pooled means with optimal value range.

From 218 abstracts extracted and after eligibility assessment and exclusion, 4 articles involving 439 patients were enrolled. The mean SS in standing and sitting calculated were 35.53±10.52 and 33.13±12.38. The mean of AI and SPT in standing /sitting positions are 29.7±12.29/34.69±12.96 (n = 242) and 19.56±8.9/21.22±12.53 (n=439) respectively. The ΔAI, ΔSS, and ΔSPT were 4.99,2.4 and 1.66 respectively.

There is a proportionate change between the spinopelvic tilt and the acetabular orientation in postural variations. Evaluation of spine, pelvis and hip becomes more critical in identifying these changes and thereby prompting the acetabular cup position in the functional safe zone.

Use of jumbo femoral heads (≥ 40 mm) in total hip arthroplasty decreases postoperative dislocation; however, may leave patients more susceptible to groin pain. Limited data exist for the effect of jumbo femoral heads and acetabular cup position on modern patient-reported outcome measures (PROMs). This study evaluated the effect of jumbo femoral heads and acetabular cup position on PROMs after primary total hip arthroplasty.

A total of 328 consecutive primary THAs of a single implant system with various femoral head sizes (36% ≥ 40 mm) were retrospectively reviewed. Acetabular cup inclination and anteversion were radiographically measured. Demographics, comorbidities, and implant sizes were documented. Prospectively collected University of California Los Angeles Activity Level, Hip Disability and Osteoarthritis Outcome Score for Joint Replacement (HOOS JR), and satisfaction were evaluated. The mean follow-up was 1.2 years (range, one to five). A P-value of 0.05 was considered statistically significant.

Femoral head size was not associated with University of California Los AngelesActivity Level scores at any time point (P ≥ 0.209). Independent of patient sex, the mean HOOS JR score was significantly higher in the ≥ 40 mm femoral head group compared to the < 40 mm head group at 4 months although not reaching a clinically significant threshold (mean difference 4.4, 95% CI [confidence interval]: 0.5 to 8.3, P = 0.027); however, mean scores at the latest follow-up were not different (P = 0.956). The HOOS JR scores ≥ 90 and being "very satisfied or satisfied" were associated with a wide range and several combinations of acetabular cup inclination and anteversion. A total of 88.9% of patients reported being "very satisfied or satisfied" at the latest follow-up.

Patients achieved comparable PROMs regardless of femoral head size, suggesting large femoral heads may not leave patients susceptible to groin pain in addition to reducing the risk of postoperative dislocation. Excellent patient outcomes correlated with wide ranges of acetabular cup positions.

III.

Proper positioning of a total hip arthroplasty (THA) plays a crucial role in the success and long-term survivorship of the implant. Cup positioning within the Lewinnek Safe Zone (LSZ) does not, however, avoid implant dislocation. Thus, the concept of a functional cup position has been introduced. The purpose of this study was to assess the discrepancy between LSZ and the acetabular cup position suggested by the patient's specific functional planning. The hypothesis was that a mismatch does exist.

One hundred consecutive patients with primary hip osteoarthritis undergoing primary THA with a personalized functional preoperative planning and patient-specific cup implantation system were enrolled. Anatomical and spino-pelvic functional parameters were recorded and, for each patient, a "safe cup orientation" was suggested. The suggested functional safe zone was compared to the LSZ.

The mean suggested inclination was 39° ± 3° (range 32°-45°). The mean suggested anteversion was 21° ± 3° (range 12°-28°). The patient's functional acetabular inclination (AI) corresponded to the LSZ in one of the 100 patients, whereas the acetabular anteversion (AV) was outside the LSZ in 8 of the 100 patients. The mean pelvic tilt while standing and sitting were 0.5° ± 7° (range 21°-45°) and -6° ± 16.7° (range -63°-33°), respectively. The mean pelvic incidence was 52° ± 9.7° (range 33°-83°).

When a functional patient's specific preoperative planning is performed, the LZS does not correspond to the patient's functional safe zone in about 8% of patients. The concept of a universal safe zone should be revisited, and a functional personalized safe zone may have to be more widely considered.

Robotic-assisted total hip arthroplasty (THA) through the posterior approach is indicated in cases of symptomatic hip arthritis. The goal of the procedure is to relieve pain and restore function while minimizing postoperative complications such as dislocation. Dislocation often occurs despite traditionally well placed components1,2. The hip-spine relationship can be a causative factor in postoperative instability, particularly in patients with altered spinopelvic kinematics as a result of spinal fusions or degenerative spine disease, in whom component placement based on anatomic landmarks may lead to functional malpositioning3,4. Therefore, we present our technique for robotic-assisted THA through the posterior approach, which incorporates patient-specific spinopelvic kinematic data to maximize impingement-free range of motion and minimize the risk of dislocation.

Preoperative computed tomography (CT) scans are obtained in order to generate a 3D model of the patient's unique hip anatomy. Lateral lumbar radiographs with the patient in the sitting and standing positions are also obtained preoperatively. The sacral slope is measured in each position, imported into the robotic software, and utilized to aid in positioning the components for optimal leg length, offset, and stability of the hip replacement based on the patient's unique spino-kinematic profile. The procedure begins with 3 partially threaded pins being driven into the ipsilateral iliac crest about 2 cm posterior to the anterior superior iliac spine. The robotic pelvic array is fastened to the pins. A standard posterior approach to the hip is utilized. Skin and subcutaneous tissues are dissected down to the iliotibial band and gluteus maximus fascia. The fascia is longitudinally incised, and a small metallic pin is malleted into the distal aspect of the greater trochanter. Initial leg length and offset values are captured. The short external rotators and posterior hip capsule are elevated. The hip is dislocated, and a neck resection is made at a level determined preoperatively with use of the robotic software. The acetabulum is exposed, and osseous registration is carried out to establish a relationship between the 3D model built with use of the robotic software and the patient's anatomy in vivo. The acetabulum is single-reamed, and the final cup is impacted in the desired position. The proximal femur is broached with increasingly sized broaches until rotational and axial stability has been achieved. A trial femoral neck and head are attached to the final broach, and the hip is reduced. Posterior and anterior hip stability are assessed, and leg length and offset are rechecked via the robotic system. Once the surgeon is satisfied, the hip is dislocated, the broach is removed, and the final femoral stem and head are manually implanted. The hip is then reduced for the final time. Closure is performed according to surgeon preference.

Surgical alternatives include THA with use of manual instrumentation or navigation through other approaches to the hip, including the direct anterior, anterolateral, and direct lateral approaches5-7. Nonoperative alternatives include physical therapy, the use of nonsteroidal anti-inflammatory pain medication, and intra-articular corticosteroid injections8.

Robotic-assisted THA is particularly advantageous in patients with abnormal spinopelvic kinematics who require precise and specific component positioning to optimize hip stability9-11. In these patients, manually placing components relative to anatomic landmarks may lead to functional malpositioning and ultimately dislocation. Additionally, cases in which there is an anticipated difficulty in acetabular exposure or preparation because of a large body habitus or large pannus, retained acetabular hardware, or severe acetabular wear or dysplasia may benefit from the use of this technique9.

Patients who undergo robotic-assisted THA through the posterior approach should expect excellent clinical outcomes in addition to low rates of complication and revision12. Robotic-assisted THA has been shown to lower the risk of dislocation compared with manual techniques10,11. In a study by Bendich et al., a robotic-assisted THA cohort had a 0.3 odds ratio of reoperation for dislocation compared with a manual THA cohort10.

Stable array pins are critical in order to obtain accurate leg length and offset measurements intraoperatively.When registering the acetabulum via the robotic software, aim for maximum spread of captured points to ensure accuracy of cup placement.In large-statured patients or patients with a particularly stiff hip, in whom anterior femoral retraction is difficult, disconnect the reamer from the robotic arm and place it into the acetabulum by hand before reconnecting it to the robotic arm. Remove the anterior acetabular retractor and set the reaming orientation to 50° of inclination and 10° of anteversion. Final cup position is kept in the desired orientation.Remember that the robotic-assistance device is just a surgical tool, and the quality of its output relies on the quality of its input. If there is concern for an error in component placement, intraoperative radiographs should be obtained.

THA = total hip arthroplastyCT = computed tomographyDVT = deep vein thrombosisIT = iliotibial.

Pelvic incidence - lumbar lordosis (PI-LL) mismatch is often considered when assessing spinopelvic alignment in the sagittal plane. The mismatch is conventionally obtained by measuring 2 separate angles on lateral spinopelvic radiographs. This study describes a simplified approach for assessing spinopelvic mobility and measuring the PI-LL mismatch through the evaluation of the L1-spinopelvis angle (L1SP).

96 standing lateral radiographs were obtained from consecutive patients presenting for total hip arthroplasty between November 2020 and July 2021. 3 operators were recruited to annotate landmarks on digital radiographs. Correlation analysis and error analysis were applied. Measurement reproducibility was assessed using intraclass correlation coefficient (ICC).

The correlation coefficients of the 3 variables were respectively 0.87 for PI, 0.94 for LL, and 0.96 for L1SP. The normalised root mean square error between the 2 measurement sets was 9.96% for PI, 5.97% for LL, and 4.41% for L1SP. The absolute error was 3.49° ± 4.63° for PI, 3.23° ± 3.78° for LL, 2.68° ± 3.19° for PI-LL conventional, and 2.35° ± 2.88° for PI-LL via L1SP, respectively. In terms of reproducibility, measurement of L1SP outperformed that of PI and LL (ICC = 0.97 versus 0.83 and 0.93, respectively).

The simplified L1SP method, through the measurement of a single angle, produced similar measurements to the conventional PI-LL method. The measurement repeatability between operators was improved using the L1SP method. From a clinical practice perspective, both methods are equivalent. The new method is readily reproducible using commercially available PACS software during preoperative templating.

Surgeons increasingly recognize the importance of patient-specific considerations in determining ideal cup alignments. In addition, various surgical navigation systems have been reported to improve cup placement accuracy during total hip arthroplasty (THA). Recently, a novel computed tomography (CT)-based planning and mixed-reality (MR) guidance system was developed to enable patient-specific 3-dimensional planning of the ideal cup position and further improve intraoperative achievement of the planned orientation.

This is retrospective, observational study of 40 patients (40 hips) who underwent MR-guided THA. Patient-specific CT-based surgical planning with definition of target operative anteversion and inclination of the acetabular cup in relation to the anterior pelvic plane was performed. 3D holograms of the cup and cup impactor in the selected target position were created and exported. Intraoperatively, automatic holographic registration was performed using a smart tool-based linked-paired-point matching method. Patient-specific content was displayed on a head-mounted display, and the acetabular component was inserted by matching the spatial position of the cup impactor with the hologram of the cup impactor in the target position. Postoperatively, patients underwent biplane simultaneous imaging for measurement of achieved cup alignment using a validated measurement method.

Mean planned operative anteversion and inclination angles were 28.4° ± 1.6° (95% confidence interval [CI], 27.9°-28.8°) and 39.9° ± 0.3° (95% CI, 39.8°-40.0°), respectively. The mean absolute target error between preoperative target operative anteversion and the achieved operative anteversion was 0.7° ± 1.1° (95% CI, 0.3°-1.0°; range, 0°-4°). The mean absolute target error between preoperative target operative inclination and the achieved operative inclination was 1.1° ± 1.2° (95% CI, 0.7°-1.4°; range, 0°-4°).

Acetabular component positioning using a mixed reality guidance system during THA was highly accurate and well within the accuracy reported for other navigation systems.

Level III. See Instructions for Authors for a complete description of levels of evidence.

Accurate component placement plays a critical role in the outcome of total hip arthroplasty (THA). Robotic-assisted THA (R-THA) has emerged as an option to optimize this aspect compared to the conventional manual THA (C-THA). The aim of this meta-analysis was to analyze the studies comparing R-THA and C-THA. The hypothesis was that the use of robotic technology could improve component positioning, but this advantage may not translate into clinically relevant benefits.

The literature search was conducted on three databases (PubMed, Cochrane Library, and Web of Science) in January 2024. The screening process and analysis were conducted separately by two independent observers according to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines. The inclusion criteria were comparative studies, English language, no time limitation, and focusing on the comparison of R-THA and C-THA. Among the 1,883 articles retrieved, 38 studies (10,055 patients) were included. The meta-analysis covered radiological outcomes, clinical outcomes, perioperative parameters, complications, and revisions. The quality of each article was assessed using the "Downs and Black's checklist for measuring quality".

Robotic THA provided superior radiological results compared to C-THA in terms of acetabular cup placement within the Lewinnek safe zone (P < 0.01) and horizontal change of the rotation center (P = 0.03). No statistically significant difference was obtained in terms of clinical scores between the two approaches, including Harris Hip Score, Western Ontario and McMaster Universities Arthritis Index, Forgotten Joint Score, and Merle d'Aubigné Hip Score. Robotic THA showed longer operative time (P < 0.01), but lower complication rates (P = 0.04). No difference was obtained in terms of intraoperative blood loss and revision rates.

The results of this meta-analysis suggest that R-THA can provide more accurate cup placement and better restoration of the native hip anatomy while reducing complication rates compared to C-THA. However, these benefits did not translate into clinical differences in terms of patient-reported outcomes between the two approaches, and R-THA required longer operative time. While the overall results suggest some benefits with the robotic technology, future studies should investigate if further technical improvements will translate into clinically relevant benefits for patients undergoing THA.

Robot-assisted instrumentation during total hip arthroplasty (THA) has the potential to improve acetabular cup positioning. This study aimed to evaluate the precision of robotic-arm-assisted THA (rTHA) and assess whether the system can provide accurate cup positioning comparable to conventional THA (cTHA).

A single-center prospective cohort study consisting of 151 patients who underwent THA (108 rTHA and 43 cTHA). The robotically assisted system was used to match the postoperative computed tomography (CT) image of the pelvis with the planned and intraoperative anatomical landmarks. The cTHA cohort underwent hip replacement using the standard manual procedure, with acetabular component locations assessed during and after surgery.

The rTHA cohort was significantly younger, but no other significant differences were found between the two cohorts in preoperative baseline data. In rTHA cohort, the planned inclination (40.0 ± 0.3°) closely matched the intraoperative (40.2 ± 2.7°; p = 0.54) and postoperative (40.7 ± 4.0°; p = 0.07) measurements. However, anteversion showed a significant increase from planned (19.4 ± 1.5°) to postoperative CT scan (28.7 ± 7.0°; p < 0.001). There was evidence of proportional bias in the measurements (p < 0.001). In the cTHA cohort, the mean inclination (43.1 ± 5.1°) did not show any significant change between the preoperative plans and postoperative assessments (p = 0.12); however, there was a remarkable change in the mean anteversion (17.6 ± 6.4°) between postoperative measurements and the preoperative plans (p < 0.001). The average anteversion in the preoperative plans did not differ remarkably between the rTHA and cTHA cohorts. However, the average inclination was substantially different between the two cohorts (p < 0.001). Both groups had no significant differences in the proportion of cups outside the referenced safe zones.

The results suggest that while robotic-assisted guidance ensures consistent cup inclination, there may be more variability in achieving the planned anteversion, which warrants further investigation into the factors influencing postoperative changes in acetabular orientation.

Although sagittal alignment is known to influence pelvic position, few studies accurately identify the relationship between sagittal alignment and acetabular orientation. We hypothesized that postoperative PT should be correlated with acetabular change in native hips after surgical correction of adult spinal deformity. The objective of this study was therefore to describe the correlation between the change in pelvic tilt and the change in acetabular orientation two years after surgical correction of adult spinal deformity.

Based on a retrospective study of a prospective mono center database, 127 acetabuli out of sixty-nine patients were analyzed preoperatively and at two years postoperatively of surgical management of sagittal imbalance by posterior arthrodesis extended to the pelvis. The analysis was based on bi-planar EOS radiographs with 3D reconstructions of the pelvis and spine using SterEOS 3D software. The following specific parameters were analyzed: sacral slope, pelvic tilt, lumbar lordosis, SVA, acetabulum tilt (AT), anteversion (AA) (orientation of the acetabulum in the axial plane), abduction (AAbd) (orientation of the acetabulum in the frontal plane), inclination (AI) (orientation of the acetabulum in the sagittal plane), and anterior acetabulum coverage (ACA). A Pearson correlation was performed between the pre-and postoperative change in acetabular parameters (right and left) and pelvic parameters. Linear regressions were performed to identify the most relevant pelvic and spinal parameters. A subgroup analysis was performed to identify a difference between distal sacral and distal ilium fixations.

All measured acetabular parameters were significantly different two years after surgery. Changes in AT (p = 0.03), AI (p = 0.03) and ACA (p = 0.05) were significantly greater in the ilium fixation group. Postoperative PT reduction was strongly correlated with the decrease of AT and AA ( = 0.61 and = 0.57, p < 0.001), it was also correlated with the increase of AI and ACA and the decrease of AAbd. The entire cohort linear regression analysis revealed that a 1 ° decrease in PT resulted in a 0.4 ° decrease in AA and a 0.6 ° decrease in AT (R2 = 0.45 and = 0.38).

Our study highlights the significant influence of the change in sagittal alignment on acetabular orientation in standing position. This correlation explains the increased risk of anterior hip impingement, the change in acetabular load distribution that might lead to early hip osteoarthritis, and the overall change in the subjects' gait pattern.

IV.

As the use of robotics in total hip arthroplasty (THA) continues to gain popularity, differences in clinical outcomes when compared to manual techniques have remained unclear. This study aimed to compare postoperative complications between patients undergoing robotic-assisted techniques and manual THA for primary osteoarthritis at 90 days, 1 year, and 2 years.

Using an all-payer national database, we identified 405,048 patients who underwent either robotic-assisted or manual THA for primary osteoarthritis. A propensity match was performed for age, sex, a comorbidity index, chronic kidney disease, obesity, and diabetes, resulting in 7652 patients in each cohort. We assessed postoperative outcomes, including surgical site infections, pulmonary emboli, venous thromboemboli, wound complications, dislocations, aseptic revisions, periprosthetic joint infections, and periprosthetic fractures. We completed bivariate analyses via chi-square tests to assess categorical variables. We utilized student's t-tests to compare continuous variables, including ages and comorbidities. Odds ratios (ORs) were calculated for complications using 95% confidence intervals (CIs).

The robotic-assisted cohort had lower rates of dislocation at 90 days (0.93 vs 1.41%, OR 0.65, 95% CI 0.48-0.88, P = .007), 1 year (1.32 vs 1.92%, OR 0.68, 95% CI 0.53-0.88, P = .004), and 2 years (1.66 vs 2.1%, OR 0.79, 95% CI 0.62-0.99, P = .049). Total surgical complications were significantly lower in the robotic-assisted cohort at 1 year (5.29 vs 6.16%, OR 0.85, 95% CI 0.74-0.98, P = .0205), but were similar at 90 days and 2 years. At 90 days, the rates of medical complications, including surgical site infections, pulmonary emboli, venous thromboemboli, and wound complications, were similar (all P > .05). The rates of periprosthetic joint infections, aseptic revision, periprosthetic fractures, and aseptic loosening were similar at all time points (all P > .05).

Patients who underwent robotic-assisted THA had lower rates of dislocation at 90 days, 1 year, and 2 years. This finding supports the use of robotic assistance in THA, though further research is needed to confirm and strengthen these findings.

The long-term effectiveness of total hip arthroplasty (THA) largely depends on the accuracy of acetabular prosthesis placement. To improve the accuracy of acetabular prosthesis placement, we utilized a new surgical navigation system: visual treatment solution (VTS). The purpose of this study was to verify the efficacy and safety of this system in assisting THA.

This was a prospective, multicenter, randomized controlled trial. One hundred and twenty-four patients undergoing primary THAs were included. The experimental group underwent VTS-assisted THA, and the control group underwent traditional surgical techniques. The main efficacy evaluation indicators were the proportion of anteversion and inclination angles in the Lewinnek safe zone, and secondary evaluation indicators included operation time, Western Ontario and McMaster University Osteoarthritis index (WOMAC) score, Harris score, short-form-36 (SF-36) score, and hip dislocation rate. Statistical analysis was performed mainly by t-test and chi-square test.

The proportion of both anteversion and inclination angles in the safe zone was 93.1% in the experimental group and 50.9% in the control group; the difference was significant (p < 0.01). The average operation time was 112.5 min in the experimental group and 92.6 min in the control group; the difference was significant (p < 0.01). There were no significant differences in WOMAC score, Harris score, or SF-36 score between the experimental and control groups at 3 months after the operation (p > 0.05). The dislocation rate was 0% in the experimental group and 1.6% in the control group; the difference was not significant (p > 0.05).

VTS-assisted THA can significantly improve the accuracy of acetabular prosthesis placement. However, there were no differences in short-term clinical outcomes or dislocation rates between the two groups.

Recent studies have proposed optimizing the position of the acetabular component based on spinal deformity and stiffness classification to avoid mechanical complication after total hip arthroplasty (THA). The aim of this study was to characterize the dynamic changes in cup alignment post-THA based on the spinopelvic classification and to evaluate the efficacy of cup placement of preventing dislocation.

This prospective study included a total of 169 consecutive patients awaiting THA who were classified into four groups based on spinal deformity (pelvic incidence minus lumbar lordosis) and spinal stiffness (change in sacral slope from the standing to seated positions). The cups were aligned based on the group with fluoroscopy. Additionally, postoperative radiographic inclination (RI), radiographic anteversion (RA) in standard anteroposterior radiograph, and lateral anteinclination (AI) in sitting and standing positions were measured. The cumulative incidence of dislocation was evaluated at a follow-up two years post-THA.

RA was significantly greater in the group with normal spine alignment and stiff spine than in other groups (P = 0.0006), and AI in the sitting position was lower than in other groups (P = 0.012). Standing AI did not significantly differ between the groups. One posterior dislocation occurred during the study period (0.6%).

AI in the sitting position was lower in patients with normal spinal alignment and stiff spine despite larger RA in the standard anteroposterior radiographs. Consequently, with more anteversion in the normal spinal alignment and stiff spine group, spinopelvic parameters can help guide cup placement to prevent short-term dislocation post-THA.

Malposition of the acetabular component during total hip arthroplasty (THA) is a leading cause of complications and need for revision. Robotic-assisted THA purports to improve accuracy of component positioning with many reports demonstrating over 92% of components within 10° of inclination and anteversion compared to intraoperative system output. This study aimed to evaluate the intraoperative accuracy output of acetabular cup position values using a handheld miniaturized portable navigation system (Naviswiss, AG) compared to postoperative computed tomography (CT) scans.

A total of 108 direct anterior approach THA surgeries using the intraoperative navigation device were performed over a 6-month period. Intraoperative device output for measured acetabular component inclination and anteversion were recorded and compared with values derived from postoperative CT scans.

Postoperative CT analysis of acetabular component positioning demonstrated 97.22% and 94.44% were within 5° of intraoperative inclination and anteversion, respectively, compared to intraoperative values from the navigation unit. No CT demonstrated an absolute inclination or anteversion measurement difference more than 8° from the intraoperative navigation unit value. Overall, 92.59% of components were within 5° and 100% were within 8° for both inclination and anteversion compared to postoperative CT measurements.

This handheld portable navigation system yielded highly accurate intraoperative component positioning values confirmed by postoperative CT scans during direct anterior THA, possibly superior to reported robotic-assisted THA values. These smaller, portable, and more accessible intraoperative units may provide surgeons improved accuracy and availability in a number of surgical settings for use in THA.

This study aims to investigate the preferences of orthopedics and traumatology specialists in evaluating the spinopelvic relationship in primary total hip arthroplasty (THA) in Türkiye.

Members of the Turkish Orthopedics and Traumatology Association (n=2485) were invited to fill out the questionnaire. The survey was created using Google Forms and distributed to participants via WhatsApp and Gmail by sharing the link. A total of 205 orthopedic surgeons responded and completed the questionnaire. The survey included 13 questions about the duration of their experience, the number of THA and spinal instrumentation procedures they performed, the dislocation rates they encountered after surgery, and the radiological assessments they performed for the spinopelvic relationship.

Sixty-three percent of the participants evaluated spinopelvic parameters in patients undergoing THA. Forty-seven percent of surgeons state that in their daily practice, they determine the angle of the acetabular component according to whether the spinal deformity is rigid, flexible, balanced, or unstable. While 88% of the participants stated the rate of encountering dislocation after primary THA as less than 2%, 12% of the participants stated it as more than 2%. It was observed that 40% of the surgeons with a prosthetic dislocation rate of more than 2% evaluated the spinopelvic relationship, while 67% of the surgeons with a dislocation rate of less than 2% evaluated the spinopelvic relationship.

Approximately half of the orthopedic surgeons in Türkiye plan component placement in primary THA cases by considering the spinopelvic relationship. In order to increase awareness about the spinopelvic relationship, it would be beneficial to give more space to this subject in training programs and conferences.

N/A.

The growing adoption of robotic-assistance during total hip arthroplasty (THA) has provided novel means through which a patient's anatomy and dynamic spinopelvic relationship can be incorporated into surgical planning. However, the impact of enhanced technologies on intraoperative decision-making and changes to component positioning has not yet been described.

A multicentre, prospective study included 105 patients (52% women) patients who underwent robotic-assisted THA with the integration of software that incorporates a patient's pelvic tilt (PT) and virtual range-of-motion (VROM) for impingement modeling. The primary outcome of the study was the percentage of patients who underwent changes to the preoperative plan for cup position after incorporating the data from the software.

Utilising the intraoperative VROM information, the preoperative plan for cup position was changed from the default (40° inclination and 20° anteversion) in 82/105 (78%) cases. When stratifying by spinopelvic mobility, 64% were considered normal (change ⩾ 10° and ⩽30°), 27% were stiff (change < 10°), and 9% were hypermobile (change > 30°). For all cohorts, the majority of cases (78%) deviated from the 40° inclination and 20° version target. When evaluating the proportion of cases within the Lewinnek and Callanan safe zones based on spinopelvic mobility, 19% of cases within the normal group were planned outside of both zones compared to 39% of stiff cases and 10% of hypermobile cases.

Utilising the latest version of robotic-assisted THA software, the preoperative plan for cup position was changed in the vast majority (78%) of patients, causing substantial deviations from traditional, generic cup targets.

Precise positioning of the acetabular component during total hip replacement is the key to achieving optimal implant function and ensuring long-term patient comfort. However, different anatomical variations, degenerative changes, dysplasia, and other diseases make it difficult. In this study, we discuss a method based on the three-dimensional direction of the transverse ligament, predicting native acetabular anteversion with higher accuracy.

Angular positions of the acetabulum and direction of the transverse ligament were automatically calculated from routine computed tomography data of 270 patients using a registration algorithm. The relationship between acetabular angles and ligament direction and their relationship with sex, age, and pelvic tilt were sought. These relationships were then modelled using multilinear regression.

Including the direction of the transverse ligament in the sagittal and transverse planes as a regressor in the multilinear model explained the variation in acetabular anteversion (R2 = 0.76 for men, R2 = 0.63 for women; standard deviation in prediction: men, 3.92° and women, 4.00°).

The results indicate that the ligament was suitable as a guidance structure almost insensitive to the ligament in the sagittal and transverse planes must be considered. Estimation based on the direction in only 1 plane was not sufficiently accurate. The operative acetabular inclination was not correlated with the direction of the ligament. The correlations were higher in men than in women.

The aim was to investigate the effect of surgeon handedness on acetabular cup positioning, functional outcomes, and dislocation incidence during primary THA.

A systematic review was conducted according to the PRISMA guidelines. Studies published in English were searched in three databases (PubMed, Embase, and Scopus). A dominant side is a right-handed (RHD) or left-handed (LHD) surgeon who operates on the right or left hip, respectively. The opposite is considered to be the non-dominant side. We used odds ratios for dichotomous data and mean differences for continuous data, with 95% confidence intervals for quantitative data synthesis. Heterogeneity was assessed using the I² test, with outcomes graphically represented in a forest plot and a p-value of < 0.05 considered statistically significant; analyses were performed using Review Manager 5.4 (RevMan 5.4.1). >.

Four observational studies were included out of 98 articles. Ten experienced surgeons participated (8 RHD and 2 LHD) and operated on 822 patients (1484 hips), divided equally between dominant and non-dominant sides, and the posterolateral approach was utilized in 80.9% of THAs. RHD surgeons operated on 1404 (94.6%) THAs. The pooled synthesis for inclination indicated no significant difference between either side [MD: 0.10 (95% CI -2.10 to 2.30, P = 0.93, I² = 91%)]. While the difference was significant for anteversion [MD: -2.37 (95% CI -3.82 to -0.93, P = 0.001, I² = 31%)]. The functional outcome was better on the dominant side [MD: 1.44 (95% CI 0.41 to 2.48, P = 0.006, I² = 0%)], and the dislocation incidence was significantly higher on the non-dominant side [OR: 0.45 (95% CI 0.25 to 0.81, P = 0.008, I² = 0%)].

Surgeon handedness and whether operating on the dominant or non-dominant side could affect the acetabular cup positioning and outcomes during primary THAs, even in the hands of high-volume surgeons.

This study aims to assess the impact of repairing the hip joint capsule during posterior-lateral approach total hip arthroplasty (THA) on postoperative hip joint function and late dislocation incidence.

A retrospective cohort study included 413 patients, divided into experimental (hip joint capsule repair, n = 204) and control (hip joint capsule excision, n = 209) groups. Patients were followed for five years, evaluating postoperative hip range of motion (ROM), dislocation rate, VAS and HHS scores, inflammatory and coagulation markers, hospitalization, blood loss, and body composition. Statistical analysis included the Student's t-test, Chi-square test, and logistic regression for dislocation risk factors.

Joint capsule repair improved postoperative hip flexion and extension within six months and at two years postoperatively, internal and external rotation within three months, and abduction and adduction throughout the entire follow-up period (P < 0.05). Capsular repair also reduced early and late dislocation rates (P < 0.05). Significant differences in HHS and VAS scores, inflammatory and coagulation indicators, hospitalization, blood loss, and body composition were noted (P < 0.05). Multivariate logistic regression indicated hip joint repair, rheumatoid arthritis, epilepsy, and sarcopenia as dislocation risk factors (P < 0.05).

Capsular repair during posterior-lateral THA improves postoperative hip function and mobility while reducing dislocation rates, blood loss, pain, inflammation, and economic burden. Patients with rheumatoid arthritis, epilepsy, or sarcopenia require individualized planning and enhanced postoperative care to minimize complications.

Every degree of change in pelvic tilt (PT) leads to a 0.7° change in anteversion and a 0.3° change in inclination. This study aimed to determine the significance of contralateral hip arthritis on changes in PT using preoperative and postoperative anteroposterior radiographs.

There were 193 primary total hip arthroplasties done by 2 surgeons at a single academic tertiary referral center reviewed between September 2021 and January 2023. PT was calculated as Tilt = -(ln[(B/A) × (1/0.483)]) / 0.051. Value A is the distance from the base of the SI joint to the superior margin of the obturator foramen; value B is the height of the obturator foramen. After exclusions, contralateral hips were identified as being normal (n = 75), arthritic (n = 39) (Tönnis grade 3/4), replaced (n = 34), or having undergone simultaneous bilateral total hip arthroplasty (n = 5) on postoperative films. Difference in PT was measured between preoperative and postoperative films taken 1-3 months after surgery. Analyses for statistical significance were calculated using t-tests and one-way analysis of variance.

Average change in PT in patients with normal contralateral hips was -5.2° with an absolute mean difference of 7.6°, -1.5° for arthritic contralateral hips with an absolute mean difference of 5.0°, -1.6° for replaced contralateral hips with a mean absolute difference of 4.3°, and 2.2° for bilateral hips with a mean absolute difference of 2.6° (P < .01).

Differences in postoperative PT changes between healthy, arthritic, and replaced contralateral hip study groups were significant. Changes in preoperative to postoperative tilt may have implications for optimal cup placement.

Various computer-assisted surgical systems claim to improve the accuracy of cup placement in total hip arthroplasties after assessing spinopelvic mobility to prevent prosthetic impingement. However, no study has yet analyzed the extent of the patient-specific cup anteversion safe zones.

We hypothesized that most patients have a safe zone >10 °, except those with abnormal spinopelvic mobility, who have a much narrower safe zone.

We simulated the risks of prosthetic impingement using the planned cup anteversion. The consecutive cohort included 341 patients who underwent total hip arthroplasty. Our primary endpoint was the patient-specific impingement-free zone for cup anteversion, which was then divided into four subgroups: 0 °, 1 ° to 5 °, 6 ° to 10 °, and >10 °. This data was then secondarily analyzed for abnormal spinopelvic mobility (the difference in the spinopelvic tilt [ΔSPT] from a standing to a flexed seated position >20 °).

The mean anteversion safe zone was 22.8 ° with 82.4% (281/341) of patients with a zone strictly >10 °. The mean safe zone was 8.9 ° (+/- 9 °) in patients with an ΔSPT ≥20 ° (18.2%), with 37.1% of these patients having a zone of 0 °, 16.13% a zone between 1 ° and 5 °, 8.06% a zone between 6 ° and 10 ° and 38.71% a zone >10 °. The mean safe zone was 25.9 ° (+/- 9 °) in patients with an ΔSPT <20 ° (81.8%), and the proportion of cases in each zone was 2.51%, 1.08%, 4.3%, and 92.11%, respectively (p < 0.001).

The safe zone for anteversion appears to be fairly wide in most patients. However, identifying patients at risk of abnormal spinopelvic mobility seems necessary to identify the two-thirds of patients with a narrow safe zone.

IV; retrospective study.

Background and Objectives: Navigation systems are designed to enhance surgical precision, improving patient outcomes and reducing the risk of implant misplacement. In this study, we have evaluated a novel orthopedic surgical platform that utilizes CT imaging with AI-based algorithms to automate several critical aspects of total hip arthroplasty. It contains three modules-preoperative planning, navigation during surgery, and follow-up analysis. The primary objective of the current study was to evaluate the precision of the navigation tool in cup placement, i.e., whether the information displayed for navigation correctly reflected the actual position of the implant. Materials and Methods: Surgery outcomes of 15 inter-rater measurements on human cadavers and 18 surgeries on patients who underwent total hip replacement using the navigation tool were analyzed. Results: In the inter-rater assessment, the mean errors were -0.31 ± 1.42° for anteversion, 1.06 ± 1.73° for inclination, and -0.94 ± 1.76 mm for cup position depth. In patients' surgeries, the mean errors were -0.07 ± 2.72° for anteversion, -0.2 ± 0.86° for inclination, and 0.28 ± 0.78 mm for cup depth. Conclusions: The navigation tool offers intra-operative guidance on notable precision in cup placement, thereby effectively mitigating the risk of cup malpositioning outside the patient-specific safe zone.

In total hip arthroplasty (THA), the positioning of components holds critical importance for factors such as joint stability, polyethylene liner wear, and range of motion. This meta-analysis aimed to compare the effects of intraoperative fluoroscopy (IF) versus no use of IF on component positioning and the restoration of patient anatomy during THA.

We conducted our systematic review following the recommendations outlined in the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. The literature search was performed from the inception of medical databases up to August 2023. PubMed, Embase, Web of Science, Cochrane Controlled Trials Register, Cochrane Library, Highwire, Wanfang, China National Knowledge Infrastructure (CNKI), China Biology Medicine Disc (CBM), and China Science and Technology Journal (CSTD) databases were systematically searched to identify relevant studies comparing IF versus no IF during primary THA.

Thirteen studies involving 2195 patients (2207 hips) were incorporated in the Analysis. No statistically significant differences were observed between the groups in terms of acetabular cup inclination angle (ACIA, P = .9), ACIA within the safe zone rate (P = .87), acetabular cup anteversion angle (ACAA, P = .42), ACAA within the safe zone rate (P = .35), combined safe zone rate (P = .30), limb length difference (LLD, P = .13), dislocation rate (P = .76), and infection rate (P = .97). In comparison to the no fluoroscopy group, the IF group exhibited prolonged operation time (P < .00001) and reduced femoral component offset difference (FCOD, P = .03).

IF did not demonstrate improvements in acetabular cup placement, limb length difference, or dislocation occurrence. Nonetheless, IF showed a significant enhancement in restoring femoral offset. It is noteworthy that surgeons operating in facilities with lower patient volumes may observe more pronounced benefits from IF.

Primary total hip arthroplasty (THA) is a procedure performed in the United States for a variety of indications, with operation rates slated to increase over 275 % by 2040 when compared to 2014 (Thilak et al., 2015). Dual-mobility (DM) implants have gained popularity in the United States since gaining approval in the early 2010s (Heckmann et al., 2020). It has been well reported that DM implants decrease the risk of dislocation after primary and revision THA (Vielpeau et al., 2011; Donovan et al., 2022; Heifner et al., 2023; Foissey et al., 2023; Schmidt et al., 2020; Neri et al., 2019).

We present the case of a 33-year-old male with a suspected ankylosing spondylitis (AS) diagnosis and bilateral bony ankylosis of the hips who underwent staged THA with modular dual-mobility (MDM) implants. At one year post-operatively, the patient is walking without the use of an assistive device and reports a VAS pain score of 0 at rest and 2 with activity and HHS of 90.

Implant selection is important in this patient population due to the increased risk of dislocation. Contemporary reports reveal MDM implants have demonstrated a substantial reduction in dislocation risk compared to fixed-bearing implants in patients with a high risk of dislocation. We opted to place the acetabular component inside the safe zone to improve stability and use the dual-mobility prosthesis to achieve our desired range of motion.

The improved stability of DM implants allows for a greater range of acetabular positions in patients who have a highly unpredictable functional outcome at the time of surgery. Our preliminary results contribute to the growing list of indications for MDM total hip arthroplasty.

Patients undergoing primary total hip arthroplasty (THA) who have spinal deformity and a stiff spine are the highest-risk group for instability. Despite the increasing use of dual-mobility cups and large femoral heads, dislocation remains a major complication after THA. Preoperative planning becomes a critical aspect of ensuring precise component positioning within a safe zone. The purpose of this study was to investigate dislocation rates over a 9-year period.

A retrospective review of 4,731 THAs performed by 3 orthopaedic surgeons between January 2014 and March 2023 was performed. Spinopelvic measurements were conducted to determine the hip-spine classification group for each patient. Only patients classified as 2B (pelvic incidence-lumbar lordosis > 10° and Δsacral slope < 10°) were eligible. Both absolute and relative dislocation frequencies were then analyzed using time-series analysis techniques and Fisher's exact tests.

A total of 281 hip-spine 2B patients undergoing primary THA were eligible for analysis (57% women; mean age, range: 66 years, 23 to 87; mean body mass index, range: 28, 16 to 45). The overall dislocation rate was 4.3%. Use of femoral head sizes ≥ 40 mm increased from 4% in 2014 to 2019 to 37% in 2020 to 2023 (P < .001), while the use of dual-mobility cups decreased from 100% in 2014 to 2019 to 37% in 2020 to 2023 (P < .001). Acetabular component planning was changed from the supine plane to the standing plane in February 2020. Those changes in surgical practice were notably correlated with a significant decrease in dislocation rates from 6.8% in 2014 to 2019 to 1.5% in 2020 to 2023 (P = .03).

Our study demonstrates that the introduction of advanced preoperative THA planning to the standing plane, coupled with precise intraoperative technology for implant placement, can significantly reduce the risk of instability in high-risk THA patients. Notably, we observed a significant decrease in dislocation rates, which aligned with the shift in surgical practice.

IV.

Optimal position of total hip arthroplasty (THA) components is critical for joint mechanics and stability. Acetabular component positioning during supine surgery in direct anterior approach (DAA) THA may be different in the standing position postoperatively, which traditional fluoroscopy is unable to predict. A novel 3-dimensional (3D) image analysis technology (IAT) that uses artificial intelligence to measure the tilt and rotation of the pelvis has enabled prediction of component positioning from supine to standing. The purpose of this study was to compare intraoperative fluoroscopy, non-3D-IAT, and 3D-IAT with postoperative standing radiographs to assess the accuracy of component positioning.

From 2022 to 2023, 30 consecutive patients (86.6% women, mean age 59 [range, 55 to 67]) undergoing primary DAA THA with the use of the 3D-IAT were identified. A separate cohort of 148 patients from 2020 to 2021 (85% women, mean age 65 [range, 55 to 69]) who underwent DAA THA with non-3D-IAT was used for comparison. Leg length discrepancy (LLD), cup anteversion, and inclination were manually measured on intraoperative fluoroscopic images and digitally measured using IAT. Follow-up evaluation occurred at 1 month with standing pelvis radiographs measured using Ein Bild Röntgen Analyze-Cup software. Measurements were compared via Wilcoxon signed rank tests where P ≤ .05 indicates significantly different measurements.

Median LLD, inclination, and anteversion measurements via non-3D-IAT and fluoroscopy were significantly different compared to postoperative standing radiographs (P < .001). The 3D-IAT more accurately predicted LLD, abduction, and anteversion, with values not significantly different from postoperative standing measurements (P = .23, P = .93, and P = .36, respectively).

The use of the 3D-IAT during DAA THA allowed for the more accurate prediction of acetabular component position in the standing position postoperatively.

Pelvis tilting in sagittal plane influences the acetabular cup position. Majority of total hip arthroplasty (THA) are performed in lateral decubitus surgical position. This study is to assess whether there is any difference in sacral slope between standing and lateral decubitus position and influence of this variation in planning acetabular cup anteversion.

This is a prospective study including 50 patients operated between January 2020 to March 2022. Preoperative radiograph included lumbosacral spine lateral X-ray in standing, supine and lateral decubitus positions to calculate the sacral slope for assessment of anterior or posterior pelvic tilting. In our study, we determined the position of the acetabular cup based on changes in sacral slope between standing and lateral decubitus postures. For patients whose sacral slope increased from lateral decubitus to standing, we implanted the acetabular component with a higher degree of anteversion. Conversely, for patients with reverse phenomenon, the cup was inserted at lower anteversion.

Twenty-four patients (48.0%) had increase in sacral slope from lateral decubitus to standing whereas 26 patients (52.0%) had decrease in sacral slope. There was linear correlation between difference in preoperative sacral slope and postoperative cross table lateral cup anteversion. Harris hip scores improved from 40.78 to 85.43. There was no subluxation or dislocation in any patient at minimum 2-year follow-up.

Individualized acetabular cup placement is important for better functional outcome in THA. Evaluation of pelvic tilting in lateral decubitus position is necessary for better positioning of acetabular cup and avoid postoperative complications.

The transverse acetabular ligament (TAL) can be a useful and reproducible landmark in the orientation of the acetabular cup in total hip arthroplasty (THA). Its role in guiding cup orientation when aiming to implant in a functional anteversion orientation is unclear. The aim of this study was to assess the relationship between the TAL and the planned acetabular cup anteversion when implanted in a function orientation.

In a retrospective study the anteversion of the TAL in the contralateral un-replaced hip was measured in CT scans of patients undergoing THA and compared to the functional cup anteversion using the patient-specific spinopelvic parameters. Comparative measurements of the native acetabular version were made from the superior rim to the inferior rim and at 10 mm intervals between the 2, all in reference to the anterior pelvic plane.

96 hips were measured. The mean TAL anteversion angle was 17.2° ± 4.5°. The mean planned acetabular cup anteversion angle was 26.3° ± 4.7°. Pearson's correlation coefficient of this measurement with the TAL was -0.03 (p = 0.769). There was a significant difference between the planned acetabular cup anteversion and the measurement of the TAL (p < 0.0001).

If cups are implanted parallel to the TAL, almost 80% will be >5° different to targeted functional cup version. It should be aimed to implant cups with more anteversion than the TAL indicates.

Precise implant positioning, tailored to individual spinopelvic biomechanics and phenotype, is paramount for stability in total hip arthroplasty (THA). Despite a few studies on instability prediction, there is a notable gap in research utilizing artificial intelligence (AI). The objective of our pilot study was to evaluate the feasibility of developing an AI algorithm tailored to individual spinopelvic mechanics and patient phenotype for predicting impingement.

This international, multicentre prospective cohort study across two centres encompassed 157 adults undergoing primary robotic arm-assisted THA. Impingement during specific flexion and extension stances was identified using the virtual range of motion (ROM) tool of the robotic software. The primary AI model, the Light Gradient-Boosting Machine (LGBM), used tabular data to predict impingement presence, direction (flexion or extension), and type. A secondary model integrating tabular data with plain anteroposterior pelvis radiographs was evaluated to assess for any potential enhancement in prediction accuracy.

We identified nine predictors from an analysis of baseline spinopelvic characteristics and surgical planning parameters. Using fivefold cross-validation, the LGBM achieved 70.2% impingement prediction accuracy. With impingement data, the LGBM estimated direction with 85% accuracy, while the support vector machine (SVM) determined impingement type with 72.9% accuracy. After integrating imaging data with a multilayer perceptron (tabular) and a convolutional neural network (radiograph), the LGBM's prediction was 68.1%. Both combined and LGBM-only had similar impingement direction prediction rates (around 84.5%).

This study is a pioneering effort in leveraging AI for impingement prediction in THA, utilizing a comprehensive, real-world clinical dataset. Our machine-learning algorithm demonstrated promising accuracy in predicting impingement, its type, and direction. While the addition of imaging data to our deep-learning algorithm did not boost accuracy, the potential for refined annotations, such as landmark markings, offers avenues for future enhancement. Prior to clinical integration, external validation and larger-scale testing of this algorithm are essential.

Modular acetabular components for total hip arthroplasty (THA) provide intraoperative flexibility; however, polyethylene liner dissociation may occur. This study aimed to examine the incidence and causes of liner dissociation associated with a specific acetabular component design at a single centre.

A retrospective analysis of 7027 patients who underwent primary THA was performed to identify isolated liner dislocations. Patient demographics, clinical presentations, surgical and implant details, and both radiographic and computed tomography (CT) findings were analysed. Patients with liner dislocation were matched to a control group via 2:1 propensity score matching, and a logistic regression analysis was employed to identify associated risk factors.

A total of 32 patients (0.45%) experienced liner dislocation at a mean 71.47 ± 60.10 months post surgery. Significant factors contributing to dislocations included the use of a conventional compared with a highly crosslinked polyethylene component (p = 0.049) and screw fixation (p = 0.028). Radiographic and CT analysis highlighted the importance of proper component orientation, revealing that patients experiencing dislocations demonstrated significantly lower acetabular cup anteversion angles (p = 0.001) compared with the control group. Impingement and malposition, identified in 41% and 47% of the cases, respectively, further underscored the multifactorial nature of dislocation risks.

While the overall rate of polyethylene liner dislocation was low, the findings of this study highlight the importance of appropriate cup placement to decrease the risk of dissociation. It further substantiates the influence of impingement and malposition in liner displacement, with increased mechanical stress exerted on the locking mechanism under adverse conditions and the potential risk increase due to screw placement.

Spinopelvic pathology increases the risk for instability following total hip arthroplasty (THA), yet few studies have evaluated how pathology varies with age or sex. The aims of this study were: 1) to report differences in spinopelvic parameters with advancing age and between the sexes; and 2) to determine variation in the prevalence of THA instability risk factors with advancing age.

A multicentre database with preoperative imaging for 15,830 THA patients was reviewed. Spinopelvic parameter measurements were made by experienced engineers, including anterior pelvic plane tilt (APPT), spinopelvic tilt (SPT), sacral slope (SS), lumbar lordosis (LL), and pelvic incidence (PI). Lumbar flexion (LF), sagittal spinal deformity, and hip user index (HUI) were calculated using parameter measurements.

With advancing age, patients demonstrate increased posterior APPT, decreased standing LL, decreased LF, higher pelvic incidence minus lumbar lordosis (PI-LL) mismatch, higher prevalence of abnormal spinopelvic mobility, and higher HUI percentage. With each decade, APPT progressed posteriorly 2.1°, LF declined 6.0°, PI-LL mismatch increased 2.9°, and spinopelvic mobility increased 3.8°. Significant differences were found between the sexes for APPT, SPT, SS, LL, and LF, but were not felt to be clinically relevant.

With advancing age, spinopelvic biomechanics demonstrate decreased spinal mobility and increased pelvic/hip mobility. Surgeons should consider the higher prevalence of instability risk factors in elderly patients and anticipate changes evolving in spinopelvic biomechanics for young patients.

Anterior approach surgeons who utilize intraoperative fluoroscopy often try to match a preoperative radiograph as a reference for intraoperative cup position. Every degree of inaccuracy in tilt leads to a roughly 0.7° change in anteversion. This study aimed to determine how closely pelvic tilt (PT) is approximated intraoperatively when compared to preoperative anteroposterior (AP) radiographs.

This was a retrospective review of 193 primary THA's done by 2 surgeons at an academic tertiary referral center between September 2021-January 2023. There were 24 patients excluded for distorted anatomy, post-traumatic arthritis, insufficient x-rays, or a sacroiliac joint that could not be visualized on film. Data collected included age and BMI. PT was calculated using the formula, Tilt = -(ln((B/A) x (1/0.483)))/0.051. Value A is the distance from the base of the SI joint to the superior margin of the obturator foramen; value B is the height of the obturator foramen.

Mean preoperative PT was 0.2° versus intraoperative PT was 3.4° (p < 0.001). Mean absolute difference was 6.5°. 48% of patients (n = 81) had an absolute difference less than 5°, 31% (n = 52) between 5° and 10°, 14% (n = 24) between 10° and 15°, and 7% (n = 12) greater than 15°. There was no correlation between BMI or age and PT discrepancy.

Of the patients, 21% had a discrepancy of 10° or greater between their preoperative radiographs and intraoperative fluoroscopic images. Surgeons should be aware of potential errors in cup positioning and be particularly diligent in high-risk cases.