Anterior cruciate ligament (ACL) revision surgery after failed double-bundle (DB) reconstruction is a challenging procedure. This study aimed to systematically review the research on ACL revision surgery following failed DB reconstruction, providing an overview on indications, surgical techniques, clinical outcomes and potential pitfalls occurring while performing this therapeutic approach.

Literature published from exception to February 2023 was searched in the Pubmed/MEDLINE, Embase and CINAHL databases. Studies in English reporting on patients who underwent ACL revision surgery after prior failed DB reconstruction were considered. Review articles and expert opinion or editorial pieces were excluded. Outcomes of interest included indications and pre-operative planning, surgical technique and associated procedures, type of revision surgery (either one- or two-stage), graft choice, clinical and functional outcomes, rate of complications, failure rate.

Overall, 4 studies met all the inclusion criteria for this review. All were published between 2007 and 2020. The search resulted in two retrospective comparative studies, one case series, and one case report. Average follow-up periods ranged from 24 to 45 months. From these studies, 66 patients (66 knees) were identified. One-stage revision surgery was performed in 64 on 66 patients (97%) with pathologic laxity following DB ACL reconstruction. Most frequently reported outcome was Lysholm score in five studies: average postoperative Lysholm score ranged from 90.5 to 91.0 while Tegner activity level ranged from 5.6 to 7.0. In 4 patients (6%) re-revision surgery was performed due to graft re-rupture.

One-stage ACL revision surgery following DB ACL reconstruction appears feasible providing satisfying outcomes and limited complications. The literature on this subject is limited and further comparative studies reporting long-term outcomes are needed, as high-level studies on this topic are still lacking.

Bone-patellar tendon-bone (BTB) is a graft material used in anterior cruciate ligament (ACL) reconstruction. We describe creating a femoral tunnel using an inside-out posteromedial (PM) portal technique during anatomic double-bundle ACL reconstruction with a hamstring graft. We hypothesized that applying this femoral tunnel creation method to the revision ACL reconstruction using BTB would enable reconstruction in 1 stage. In this technique, an anteromedial, an anterolateral, and a PM portal are created to confirm the original ACL footprint and location and direction of the bone tunnel during primary reconstruction. The surgeon then drills from the PM portal, so that the femoral tunnel opening touches the posterior proximal articular cartilage margin in the ACL footprint. Even if the opening partially overlaps with the primary tunnel, it is possible to create a new tunnel with a different direction. Finally, the BTB graft is guided from the tibial tunnel to the femoral tunnel and fixed with interference screws. Intraoperative PM arthroscopic views can confirm that the femoral tunnel has been created, avoiding overlap, and that the revision ACL has been reconstructed. This procedure may be useful for 1-stage revision ACL reconstruction for reinjury after primary ACL reconstruction by other conventional procedures.

This classic discusses the original publication 'Arthroscopic double-bundle anterior cruciate ligament reconstruction (ACL): An anatomical approach', the first detailed description of the surgical technique popularised by Dr Freddie Fu. The technique, in which the anteromedial and posterolateral bundles of the ACL are reconstructed individually using two grafts with independent bone tunnels, was designed to more closely recreate the function of the native ACL by more closely reproducing the functional anatomy. This reconstruction was biomechanically superior to single-bundle reconstruction, particularly with regards to rotational control, leading to great interest from ACL surgeons around the world. Clinical superiority was more difficult to demonstrate; however, and the technical difficulty of the procedure has limited its use. Nevertheless, the pursuit of improved patient outcomes through attention to functional anatomical detail continues. 'Recreating the functional anatomy of the intact ACL remains the cornerstone of ACL reconstruction'.

Previous studies have shown a higher prevalence of meniscal and chondral lesions at the time of revision anterior cruciate ligament reconstruction (R-ACLR) compared with primary ACLR procedures. However, studies that follow the development of meniscal and chondral status through primary and subsequent R-ACLR are scarce.

To compare the prevalence of meniscal and chondral injuries in patients undergoing primary ACLR and subsequent R-ACLR.

Case series; Level of evidence, 4.

Patients who underwent ACLR and subsequently needed R-ACLR between January 2009 and February 2018 in a single center were included. A retrospective analysis of prospectively collected data was conducted.

A total of 213 patients were included, with a mean follow-up of 59.7 months. The mean age was 22 years at primary ACLR and 26.1 years at the time of revision. The proportion of meniscal tears was higher at the time of R-ACLR compared with the time of primary reconstruction (70.0% vs 44.6%, respectively; P < .001). Similarly, the prevalence of chondral lesions was significantly higher at the time of revision versus the primary reconstruction (15.5% vs 7.0%, respectively; P = .003).

R-ACLR is associated with a higher rate of concomitant meniscal and chondral lesions than primary ACLR.

Revision of an anterior cruciate ligament (ACL) reconstruction can be performed as a one-stage or two-stage surgery. Several factors must be taken into consideration when making this choice, especially the size and position of the existing tunnels. When the tibial tunnel is semianatomic, it is difficult to make a new tunnel in the correct position without overlapping the existing tunnel. For this reason, we have developed a one-stage ACL revision surgery that uses a bone allograft plug. When it comes to choosing a reconstruction technique, we believe that combined intra-articular and extra-articular reconstruction with the iliotibial band is suitable when the hamstring tendons are not available, combined with clinical findings of translational and rotational instability. Because the existing tunnels require reorientation, a new femoral tunnel can be created by outside-in drilling to eliminate the risk of overlap, while an allograft bone plug can be used to fill the overly anterior tibial tunnel and allow us to drill the correct tibial tunnel right away. In our hands, this is a safe and effective technique, but longer follow-up is needed to validate its indications.

Preoperative tunnel widening is a frequently reported indication for performing a 2-stage revision anterior cruciate ligament reconstruction (ACLR) instead of a single-stage procedure. However, the strength of the available evidence to support a 2-stage strategy is low.

The purpose was to evaluate the clinical outcomes of a single stage-only approach to revision ACLR. It was hypothesized that this approach would be associated with significant improvements from baseline in patient-reported outcome measures (PROMs) and knee stability and that there would be no significant differences in any postoperative outcomes between patients with and without preoperative tunnel widening.

Cohort study; Level of evidence, 3.

A retrospective analysis was conducted of a large series of consecutive patients undergoing revision ACLR with a minimum follow-up of 2 years. Preoperative tunnel widening was assessed using digital radiographs. All patients underwent single-stage surgery with an outside-in technique, regardless of the degree of tunnel widening. Clinical outcomes were compared according to whether tunnel widening was present (either tunnel ≥12 mm) or not (both tunnels <12 mm).

The study included 409 patients with a mean ± SD follow-up of 69.6 ± 29.0 months. After revision ACLR, there was a significant reduction in the side-to-side anteroposterior laxity difference, from 7.7 ± 2.2 mm preoperatively to 1.2 ± 1.1 mm at 2 years (P < .001). The mean International Knee Documentation Committee (IKDC) and all subscales of the Knee injury and Osteoarthritis Outcome Score (KOOS) exceeded the thresholds for the Patient Acceptable Symptom State defined for primary ACLR. An overall 358 patients had retrievable preoperative radiographs. According to the tunnel diameter measurements, 111 patients were allocated to group A (both tunnels <12 mm) and 247 patients to group B (either/both tunnels ≥12 mm). There were no significant differences between groups with respect to anteroposterior side-to-side laxity difference, graft rupture rates, non-graft rupture related reoperations, or contralateral anterior cruciate ligament injury rates. There was also no significant difference between groups that exceeded minimal detectable change thresholds for any of the PROMs recorded (ACL-RSI [Anterior Cruciate Ligament-Return to Sports After Injury], Lysholm, Tegner, IKDC, KOOS).

A single-stage approach to revision ACLR is associated with excellent clinical results when an outside-in drilling technique is utilized. The presence of preoperative tunnel widening does not significantly influence PROMs, knee stability, graft rupture rates, or non-graft rupture related reoperation rates.

The increased prevalence of anterior cruciate ligament (ACL) reconstruction has led to an increased need for revision ACL reconstructions. Despite the growing body of literature indicating that single-stage revision ACL reconstruction can yield good outcomes, there is a lack of data for determining when and how to safely perform a single-stage revision.

To assess the outcomes, graft failure rates, and return-to-play rates of a decision-making algorithm for single-stage revision ACL reconstruction.

Case series; Level of evidence, 4.

We reviewed a consecutive series of revision ACL reconstructions performed by the senior author between September 2009 and July 2016 with minimum 2-year follow-up. All patients were assessed, and decision making was undertaken according to the algorithm. Outcomes measured were further surgery, graft rerupture, re-revision, Tegner score, and Knee injury and Osteoarthritis Outcome Score (KOOS). For the elite athlete population, return-to-play time, duration, and level of play after surgery as compared with preinjury were also determined.

During this period, 93 procedures were performed in 92 patients (40 elite athletes). Two 2-stage procedures were undertaken, leaving 91 single-stage procedures (91 patients) to form the basis for further study. At a mean 4.3 years (SD, 2.2 years) after surgery, there had been 2 re-revisions (2.2%) and 2 further instances of graft failure that had not been re-revised (total graft failure rate, 4.4%). There were 17 subsequent procedures, including 6 arthroscopic partial meniscectomies, 5 removals of prominent implants, and 1 total knee arthroplasty. The mean Tegner score was 8.02 before graft rerupture and 7.1 at follow-up. At follow-up, the mean KOOS outcomes were 79.3 for Symptoms, 88.0 for Pain, 94.2 for Activities of Daily Living, 73.6 for Sport, and 68.9 for Quality of Life. Of 40 elite athletes, 35 returned to play at a mean 11.2 months (SD, 3.6 months) after surgery.

Single-stage revision ACL reconstructions can be performed reliably in the majority of patients, with good clinical outcomes, low rerupture rates, and high-return-to play rates, even in the elite athlete population.

To evaluate the surgical methods according to the status of tunnels at the time of revision anterior cruciate ligament reconstruction (ACLR) and to evaluate clinical outcomes of revision ACLR in patients who underwent primary ACLR with the anatomic 4-tunnel double-bundle (DB) technique.

A total of 487 patients who underwent primary anatomic DB ACLR from April 2010 to July 2016 were retrospectively reviewed, and among those knees, the patients who underwent revision ACLR were included in the study. The patients with concomitant posterior cruciate ligament injuries were excluded. Forty patients (40 knees) were identified and enrolled. The surgical methods were reviewed. The range of motion, objective laxity using KT-2000, Lysholm score, Hospital for Special Surgery score, International Knee Documentation Committee subjective score, and Tegner score after revision ACLR were compared with those after primary ACLR in the same patient using paired t-test with Bonferroni correction.

The timing of reinjury after primary ACLR and mean interval between primary and revision ACLR were 18 months (range 1.5-80 months) and 24 months (range 4-82 months), respectively. Among 40 patients, 38 patients (95%) underwent 1-stage revision with the DB technique using pre-existing tunnels without compromised positioning of the grafts, and the other 2 patients (5%) underwent 2-stage revision. The postrevision range of motion, KT-2000, Lysholm score, Hospital for Special Surgery score, International Knee Documentation Committee subjective score, and Tegner score were 137 ± 7°, 2.4 ± 1.2 mm, 91.4 ± 5.8, 98.9 ± 2.2, 78.6 ± 11.5, and 5.5 ± 1.2, respectively, and did not show any differences from those after primary ACLR.

In the revision setting after primary anatomic DB ACLR, most of the cases could be managed with 1-stage revision with DB technique using pre-existing tunnels, and the objective laxity and clinical scores after revision DB ACLR were comparable with those after primary DB ACLR.

Case series, Level IV.

With the rising number of anterior cruciate ligament (ACL) reconstructions, revision ACL reconstructions are becoming increasingly common. A revision procedure may be performed to improved knee function, correct instability, and facilitate a return to normal activities. When performing a revision reconstruction, the surgeon decides between a single-stage or a two-stage revision. Two-stage revisions are rarely performed, but are particularly useful when addressing substantial tunnel-widening, active infection, and concomitant knee pathology (e.g., malalignment, other ligamentous injuries, meniscal or chondral lesions). Among these potential scenarios requiring a two-stage revision, tunnel-widening is the most common cause; the first stage involves graft removal, tunnel curettage, and bone grafting, followed by revision ACL reconstruction in the second stage. The purpose of this article is to review the preoperative planning, surgical considerations, rehabilitation, and outcomes of two-stage revision ACL reconstructions and summarize the recent literature outlining treatment results.

Bone tunnel enlargement is one of the important factors that determine whether a revision anterior cruciate ligament reconstruction (ACLR) should be performed in 1 or 2 stages. The goal of this retrospective cohort study was to compare the mid-term to long-term outcomes of 1-stage revision ACLR according to the amount of preoperative tunnel enlargement.

Between January 2002 and January 2012, 88 patients who underwent revision ACLR were enrolled. The patients were divided into 2 groups based on the tunnel diameter (group A, <12 mm; group B, ≥12 mm). Clinical scores (International Knee Documentation Committee [IKDC] subjective score, Lysholm score, and Tegner score) and knee joint stability (as measured with the anterior drawer test, Lachman test, pivot-shift test, and measurement of the side-to-side difference in anterior tibial translation on Telos stress radiographs) were evaluated preoperatively and 5 to 15 years postoperatively. The failure rate and survivorship were compared between groups A and B.

The mean time to final follow-up was 7.9 ± 2.6 years. There were 44 patients in each of the 2 groups. There were no significant differences in the postoperative IKDC subjective scores, Lysholm scores, or Tegner activity scores between the groups. However, group A showed superior results on all knee joint stability tests except for the anterior drawer test. There were 3 failures in group A (7%) and 6 in group B (14%). The overall survival rates with failure as the end point were 93.1% and 84.6%, respectively, at 15 years.

The 5 to 15-year clinical scores following revision ACLR did not differ significantly according to the preoperative amount of tunnel widening. However, the results of the postoperative Lachman and pivot-shift tests as well as the side-to-side difference in anterior tibial translation on Telos stress radiographs were significantly superior in the group with a preoperative tunnel diameter of <12 mm compared with the group with a tunnel diameter of ≥12 mm.

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

The purpose of this study was to evaluate tunnel position and width in failed primary single-bundle (SB) anterior cruciate ligament (ACL) reconstructions. It was hypothesized that both femoral and tibial bone tunnels are frequently malplaced in terms of a partially anatomic position in the setting of failed SB ACL reconstruction.

Patients with recurrent instability following isolated SB ACL reconstruction using hamstring tendon autografts, undergoing revision ACL surgery, were retrospectively included. Further inclusion criteria were age >18 years and availability of preoperative computed tomography (CT) scans and radiographs of the affected knee. Patients with multiligamentous instabilities as well as incomplete or poor radiographs were excluded. Tunnel position was evaluated according to the method described by Harner et al. and Stäubli and Rauschning. Tunnel width was determined on CT scans perpendicular to the bone tunnel axis at three different heights of each bone tunnel.

Eighty-two patients met the inclusion criteria and were considered for radiological analysis. Femoral tunnels were graded as anatomic in 60% (49 of 82) of all cases. In the remaining 40% (33/82), 27% of the tunnels were placed partially anatomic and 13% were graded as non-anatomic. Tibial tunnel placement was found to be anatomic in 54% (44/82) of all cases, partially anatomic in 45% and non-anatomic in 1% of the cases. No statistically significant difference between anatomic or partially anatomic tunnel position and tunnel diameter, neither for the femoral nor for the tibial side, was observed (n.s.).

The present study demonstrates that there is a high incidence of partially anatomic placed tunnels in failed SB ACL reconstruction. Tunnel width was not associated with tunnel position. Clinically, partially anatomic bone tunnels frequently require a staged procedure with bone grafting and subsequent ACL revision surgery. Thus, surgeons should carefully analyse tunnel position and width preoperatively to properly plan ACL revision surgery.

The purpose of this study was to compare the single-bundle (SB) and double-bundle (DB) surgical techniques for anterior cruciate ligament (ACL) reconstruction with regard to tunnel widening, isokinetic muscle strength, and clinical outcomes over an 8-year follow-up period.

This study included 31 patients with ACL injury who underwent ACL reconstruction via the SB (n = 16) or the DB (n = 15) technique. Isokinetic and concentric strength measurements of the quadriceps and hamstring muscles were conducted at postoperative 6 months and postoperative 8 years, and 3D-CT scans of the knee joints were performed on the 2nd, 3rd and 6th month, and the 8th year postoperatively. Clinical evaluations were performed at 8 years postoperatively with the International Knee Documentation Committee (IKDC), Tegner, and Lysholm knee scoring systems.

There was marked widening of the parts of the femoral tunnel close to the knee joint in both the SD and the DB groups. There was no difference between the two groups in terms of clinical results and isometric muscle strength at postoperative 8 years; however, there was a significant difference between the preoperative and 6 months postoperative clinical and strength results in both group (P < 0.05). There was no difference between the groups in IKDC score, Lysholm score, Tegner activity scale, and anterior drawer test at postoperative 8 years. On evaluation of the anteromedial bundles alone, the DB group had greater widening than the SB group.

In this study, we have found that the tunnels continue to enlarge after 6 months. However, that has no impact in patients comfort and that did not made any change in our daily routine. On the other hand, we found that the reconstruction of the double-band ligament technique is useless for non-professional athletes.

Revision ACL reconstruction is becoming more frequent because of a 10% rate of re-ruptures and insufficiencies. Currently, computed tomography (CT) represents the gold standard in detecting and measuring the tunnels of the initial ACL reconstruction. The purpose of this study was to compare measurement results of CT and thin-sliced MRI sequences, which were modified to a high soft tissue-bone contrast.

Prior to an ACL revision surgery, 16 consecutive patients had an MRI in addition to the standard CT scan. A dedicated 0.25-T Esaote G-Scan (Esaote Biomedica, Cologne, Germany) with a Turbo 3D T1 sequence was used for MRI. Tunnel diameters were measured at 11 defined points of interest. For the statistical evaluation, the Mann-Whitney U test for connected samples was used. Inter- and intraobserver reliability was additionally calculated.

All measured diameters showed significant to highly significant correlations between both diagnostic tools (r = 0.7-0.98). In addition, there was no significant difference (p > 0.5) between the two techniques. Almost all diameters showed nearly perfect intraobserver reliability (ICC 0.8-0.97). Interobserver reliability showed an ICC of 0.91/0.92 for only one diameter in MRI and CT.

Prior to ACL revision surgery, bone tunnel measurements can be done using a 3D T1-MRI sequence in low-field MRI. MRI measurements show the same accuracy as CT scans. Preoperative radiation exposure in mainly young patients could be reduced. Also the costs of an additional CT scan could be saved.

One of the principal causes for failure of anterior cruciate ligament reconstruction (ACL) is femoral tunnel mal-position. Several studies compare the position of femoral tunnels achieved with various techniques, with small series and using a quadrant assessment method.

(1) What is the incidence of anatomical positioning of the intra-articular femoral tunnel aperture in primary ACL reconstruction in a university knee surgery? (2) What are the main errors in positioning?

3D-CT scans were performed after primary ACL reconstruction in 135 consecutive cases. The intra-articular position of the femoral tunnel aperture was analyzed using the Magnussen classification.

The intra-articular tunnel position was deemed anatomical in 77%, intermediate in 20.8%, and non-anatomical in 2.2%. Among the mal-positioned tunnels, 54.8% were vertical, 29% were anteriorly positioned, and 16.1% were both.

The intra articular femoral tunnel aperture was well positioned using an outside-in technique. The main error of tunnel positioning was a tunnel too vertical.

Level III, prospective study (case series).

Revision anterior cruciate ligament reconstruction (ACLR) is becoming increasingly common as the number of primary ACLR cases continues to rise. Despite this, there are limited data on the outcomes of revision ACLR and even less information specifically addressing the differences in 1-stage revision reconstruction versus those performed in a 2-stage fashion after primary reconstruction.

To compare the outcomes, patient satisfaction, and failure rates of 1-stage versus 2-stage revision ACLR.

Cohort study; Level of evidence, 3.

All patients who underwent revision ACLR between 2010 and 2014 by a single surgeon were collected, and skeletally mature patients over the age of 17 years were included. Patients were excluded if they were skeletally immature; had a previous intra-articular infection in the ipsilateral knee; underwent a prior alignment correction procedure, cartilage repair or transplant procedure, or meniscal allograft transplantation; or had an intra-articular fracture. An ipsilateral or contralateral bone-patellar tendon-bone (BPTB) autograft was the graft of choice. A BPTB allograft was considered for patients aged ≥50 years, for any patient with an insufficient ipsilateral or contralateral patellar tendon, or for those who chose not to have the contralateral patellar tendon graft harvested. Patients completed a subjective questionnaire preoperatively and at a minimum of 2 years postoperatively. Magnetic resonance imaging and computed tomography of all knees were performed preoperatively to assess for associated injuries and to evaluate the ACLR tunnel size and location. Patients with malpositioned tunnels that would critically overlap with an anatomically placed tunnel or those with tunnels ≥14 mm in size underwent bone grafting.

A total of 88 patients met the inclusion criteria for this study. There were 39 patients in the 1-stage revision surgery group (19 male, 20 female) and 49 patients in the 2-stage revision surgery group who underwent tunnel bone grafting first (27 male, 22 female). In both groups, the 12-item Short Form Health Survey (SF-12) Physical Component Summary, Western Ontario and McMaster Universities Arthritis Index, Lysholm, and Tegner activity scale scores significantly improved from preoperatively to postoperatively. There was no significant difference in the SF-12 Mental Component Summary score before and after surgery in either group. Furthermore, there was no significant difference in failure rates or other demographic data between the groups. We observed 4 failures in the 1-stage reconstruction group (10.3%) and 3 failures in the 2-stage reconstruction group (6.1%).

In this study, objective outcomes and subjective patient scores and satisfaction were not significantly different between 1-stage and 2-stage revision ACLRs. Both groups had significantly improved objective outcomes and patient subjective outcomes without notable differences in failure rates. Further longitudinal studies comparing 1-stage and 2-stage revision ACLRs over a longer time frame are recommended.

The purpose of this study is to assess the results of revision anterior cruciate ligament (ACL) reconstruction after the failure of primary ACL double bundle reconstruction (ACL-DBR).

Twenty-two knees in 22 patients (group R) that underwent ACL revision surgery using bone-patellar tendon-bone (BTB) autograft after the failure of primary ACL-DBR were included in this study. Intraoperative findings and postoperative knee laxity and clinical outcomes in group R were assessed. Forty-four knees in 44 patients that were age- and gender- matched with group R and underwent primary ACL reconstruction using BTB autograft were used as a control group (group P).

The incidence of medial meniscus and cartilage injury in group R was significantly higher than those in group P (p < 0.05). At final follow-up, median Lysholm score was 90.5 (64-100) in group R and 94 (59-100) in group P, respectively. Fourteen patients (63.6%) in group R and 31 patients (70.5%) in group P were able to return to previously-played sports, respectively. There were no significant differences in KT-1000 outcomes (2.0 mm in group R and 1.4 mm in group P) or pivot shift test between the two groups. The rate of subsequent ACL injury was similar in both groups.

Revision ACL reconstruction using BTB autograft after failed primary ACL-DBR provided almost compatible postoperative clinical outcomes and knee stability with primary ACL reconstruction using BTB autograft, while the incidence of medial meniscus and cartilage injury at revision surgery was higher.

Retrospective comparative study, Level III.

Although double-bundle anterior cruciate ligament (ACL) reconstruction has theoretical benefits such as more accurate reproduction of ACL anatomy, it is technically more demanding surgery. This report describes the case of a one stage revision single-bundle ACL reconstruction after primary double-bundle ACL reconstruction. A professional dancer had an ACL previously reconstructed with a double-bundle technique, but the femoral tunnels were malpositioned resulting in residual laxity and rotational instability. The previous femoral tunnel positions were vertical and widened. The previous vertical tunnels were filled with impacted bone graft and a revision single-bundle ACL reconstruction was performed via the new femoral tunnel with a 2 O'clock position between the previous two tunnels. After 10 months of postoperative rehabilitation, the patient returned to professional dancing with sound bony union and without any residual instability.

Studies comparing single- and double-bundle anterior cruciate ligament (ACL) reconstructions often include a combined analysis of anatomic and non-anatomic techniques. The purpose of this study was to compare the revision rates between single- and double-bundle ACL reconstructions in the Swedish National Knee Ligament Register with regard to surgical variables as determined by the anatomic ACL reconstruction scoring checklist (AARSC).

Patients from the Swedish National Knee Ligament Register who underwent either single- or double-bundle ACL reconstruction with hamstring tendon autograft during the period 2007-2014 were included. The follow-up period started with primary ACL reconstruction, and the outcome measure was set as revision surgery. An online questionnaire based on the items of the AARSC was used to determine the surgical technique implemented in the single-bundle procedures. These were organized into subgroups based on surgical variables, and the revision rates were compared with the double-bundle ACL reconstruction. Hazard ratios (HR) with 95% confidence interval (CI) was calculated and adjusted for confounders by Cox regression.

A total of 22,460 patients were included in the study, of which 21,846 were single-bundle and 614 were double-bundle ACL reconstruction. Double-bundle ACL reconstruction had a revision frequency of 2.0% (n = 12) and single-bundle 3.2% (n = 689). Single-bundle reconstruction had an increased risk of revision surgery compared with double-bundle [adjusted HR 1.98 (95% CI 1.12-3.51), p = 0.019]. The subgroup analysis showed a significantly increased risk of revision surgery in patients undergoing single-bundle with anatomic technique using transportal drilling [adjusted HR 2.51 (95% CI 1.39-4.54), p = 0.002] compared with double-bundle ACL reconstruction. Utilizing a more complete anatomic technique according to the AARSC lowered the hazard rate considerably when transportal drilling was performed but still resulted in significantly increased risk of revision surgery compared with double-bundle ACL reconstruction [adjusted HR 1.87 (95% CI 1.04-3.38), p = 0.037].

Double-bundle ACL reconstruction is associated with a lower risk of revision surgery than single-bundle ACL reconstruction. Single-bundle procedures performed using transportal femoral drilling technique had significantly higher risk of revision surgery compared with double-bundle. However, a reference reconstruction with transportal drilling defined as a more complete anatomic reconstruction reduces the risk of revision surgery considerably.

III.

Anatomic femoral tunnel placement in anterior cruciate ligament (ACL) reconstruction is considered to be a key to good primary stability of the knee. There is still no consensus on whether a centrally placed single bundle in the anatomical femoral footprint can compare with anatomic double-bundle (DB) reconstruction.

The purpose of this study was to determine knee kinematics after single-bundle ACL reconstruction via the medial portal technique using 2 different femoral tunnel positions and to compare results with those of the anatomic DB technique. The hypotheses were that (1) single-bundle reconstruction using the medial portal technique with a centrally placed femoral tunnel relative to the native footprint (SB-central technique) would more closely restore intact knee kinematics compared with the same reconstruction technique with an eccentric femoral tunnel drilled in the anteromedial bundle footprint (SB-AM technique) and (2) DB reconstruction would result in superior kinematics compared with the SB-central technique.

Controlled laboratory study.

Knee kinematics was examined in 10 fresh-frozen human cadaveric knees using a robotic/universal force-moment sensor system. Kinematics in simulated pivot-shift and 134-N anterior tibial loading tests were determined in different conditions within the same specimen: (1) intact ACL, (2) deficient ACL, (3) SB-AM, (4) SB-central, and (5) DB.

All reconstruction techniques significantly reduced anterior tibial translation (ATT) compared with a deficient ACL at 0°, 15°, 30°, 60°, and 90° in the anterior tibial loading test (P < .01, repeated-measures analysis of variance) and at 0°, 15°, and 30° in the simulated pivot-shift test (P < .001). There were no significant differences in the SB-central group and the DB group compared with the intact ACL. Reconstruction in the SB-AM group resulted in significantly increased ATT compared with the intact ACL in near-to-extension angles in both tests (0°, 15°, and 30°; P < .01). SB-central and DB reconstructions both resulted in significantly reduced ATT, in some tests at ≤30°, compared with SB-AM reconstruction (P < .05). No significant differences between the SB-central and DB groups were found (P > .05).

The SB-central technique restored intact knee kinematics more closely than did SB-AM reconstruction at time zero. There were no differences in knee kinematics between the DB and SB-central techniques.

Anatomic single-bundle ACL reconstruction provides similar knee kinematics as anatomic double-bundle reconstruction.

Using intra-operative findings and clinical results, including return to play (RTP) at the pre-injury level, this study investigated the causes of primary graft failure after revision anterior cruciate ligament (ACL) reconstruction with bone-patellar-tendon-bone (BPTB) autografts.

A total of 54 patients were followed for a mean of 38.2 ± 10.2 months post-surgery. Subjective and objective results were evaluated using single assessment numeric evaluation (SANE) scores, Lachman tests, KT-2000 arthrometer results, and pivot-shift tests. The change in each patient's Tegner activity scale and RTP at the pre-injury level were also evaluated.

Inappropriate positioning of the tunnels was the most important reason (54%) for primary graft failure. After revision surgery, anterior knee stability was significantly improved (1.2 (mean) ± 1.2 (SD)mm vs 4.5(mean) ± 1.9 (SD)mm; P < 0.01). Two (4%) patients sustained revision graft ruptures while two (4%) sustained contralateral knee ACL tears. The rate of RTP at the pre-injury level was 67% (36 patients), and mean SANE scores at the time of RTP were higher than before surgery (74.8 ± 13.8 points vs 24.1 ± 16.4; P<0.001). The average time from primary graft failure to revision surgery was shorter (12.2 (mean) ± 4.0 (SD) vs 37.6 (mean) ± 8.8 (SD)months; P < 0.01) and the ratio of major cartilage injury was lower (39% vs 83%; P < 0.05) in the RTP group than that in the non-RTP group.

The time from primary graft failure to revision surgery and the extent of the cartilage injury are major factors in RTP after revision ACL reconstructions.

Revision anterior cruciate ligament (ACL) reconstruction requires a precise evaluation of previous tunnel locations and diameters. Enlargement of the tunnels, despite not usually affecting primary reconstruction outcomes, plays an important role in revision ACL management. Three dimensional (3D) computed tomography (CT) models are reported to be the most accurate method for identifying the tunnel position and possible conflicts with a revision tunnel placement. However, the ability of 3D CT to measure the tunnel size is still not proven. The goal of this study was to evaluate the ability of measuring the size of the bone tunnels in ACL reconstructed knees with 3D CT compared to the traditional two dimensional (2D) CT method.

Twenty-four patients had CT scans performed immediately following ACL reconstruction surgery. Their femoral tunnels size were measured by a standard 2D CT measurement and then compared with three novel 3D CT measuring methods: the best transverse section method, the best fit cylinder method and the wall thickness method. The drill size used during surgery was used as a control measure for the tunnel width. Intra-class correlation coefficients were obtained.

The intra-class correlation coefficient and respective 95% confidence interval range (ICC [95%CI]) for the three methods compared with the drill sizes were 0.899 [0.811-0.947] for the best transverse section method, 0.745 [0.553-0.862] for the best fit cylinder method, -0.004 [-0.081 to -0.12] for the wall thickness method and 0.922 [0.713-0.97] for the 2D CT method. The mean differences compared to the drill size were 0.02 mm for the best fit transverse section method, 0.01 mm for the best fit cylinder diameter method, 3.34 mm for the wall thickness method and 0.29 mm for the 2D CT method. The intra-rater agreement (ICC [95%CI]) was excellent for the best transverse section method 0.999 [0.998-0.999] and the 2D CT method 0.969 [0.941-0.984].

The 3D best transverse section method presented a high correlation to the drill sizes and high intra-rater agreement, and was the best method for ACL tunnel evaluation in a 3D CT based model.