Cemented polished tapered femoral stems (PTS) made of cobalt-chrome alloy (CoCr) are a known risk factor for periprosthetic fracture (PPF). The mechanical differences between CoCr-PTS and stainless-steel (SUS) PTS were investigated. CoCr stems having the same shape and surface roughness as the SUS Exeter^® stem were manufactured and dynamic loading tests were performed on three each. Stem subsidence and the compressive force at the bone-cement interface were recorded. Tantalum balls were injected into the cement, and their movement was tracked to indicate cement movement. Stem motions in the cement were greater for the CoCr stems than for the SUS stems. In addition, although we found a significant positive correlation between stem subsidence and compressive force in all stems, CoCr stems generated a compressive force over three times higher than SUS stems at the bone-cement interface with the same stem subsidence (p < 0.01). The final stem subsidence amount and final force were greater in the CoCr group (p < 0.01), and the ratio of tantalum ball vertical distance to stem subsidence was significantly smaller for CoCr than for SUS (p < 0.01). CoCr stems appear to move more easily in cement than SUS stems, which might contribute to the increased occurrence of PPF with the use of CoCr-PTS.

Cemented femoral component design including its mechanical behavior in total hip arthroplasty (THA) has influenced the occurrence of postoperative periprosthetic femoral fracture (PPFF). The main aim of this study was to investigate the influence of the calcar collar and surface finish in the cemented femoral component on the risk of PPFF.

This retrospective review was undertaken of 1082 primary THAs in 912 patients using cemented femoral components followed for a minimum of five years (mean, 9.4 years; range, 5-24 years). The incidence of PPFF, patients' demographics and surgical details were evaluated. Kaplan-Meier survivorship analysis was performed for four different outcomes: any PPFF, revision of the femoral component for PPFF, aseptic loosening, and for any reason.

The overall incidence of PPFFs was 1.0% (n = 11): 1.4% (n = 10) in the collarless polished (CLP) group, none in the collared polished (CP) group and 0.6% (n = 1) in the collared non-polished (CNP) group (p > 0.05). Kaplan-Meier survival analysis for the femoral component at 12 years with PPFF as the end point was 97.4% (95% confidence interval [CI], 94.9 to 99.8) in the collarless group and 99.7% (95% CI, 99.1 to 100) in the collared group (p = 0.048). With revision of the femoral component for aseptic loosening as the end point, survivorship was 100.0% in the CLP and CP groups, and 98.1% (95% CI, 95.9 to 100) in the CNP group (CLP vs CP, p > 0.999; CLP vs CNP, p = 0.001; CP vs CNP, p = 0.112).

This study demonstrated that the calcar collar in the cemented femoral component could play an important role to reduce the incidence of PPFF. The surface finish in the cemented femoral components influenced the incidence of femoral component revision for aseptic loosening over 5-12 years. Surgeons should consider not only the geometry and the mechanical function of the femoral components based on different design philosophies, but also potential complications associated with different designs that may require revision arthroplasty.

The purpose of this prospective matched paired study is to compare the in vivo migration patterns using Ein Bild Roentgen Analyze femoral component of shortened vs standard-length stems cemented line-to-line in primary total hip arthroplasty (THA) at 2-year follow-up.

We prospectively included the first 50 consecutive primary cemented THAs in 50 patients using a 12% shortened stem (AmisK group) of which design was derived from the original Charnley-Kerboull (CK) femoral components. These 50 patients were matched paired to 50 patients from a historical series of patients who underwent primary THAs using standard-length CK stems (CK group) with available long-term results, including Ein Bild Roentgen Analyze femoral component data at 2-year follow-up.

Body mass index was significantly higher (P = .007) in the AmisK vs the CK group. At the 2-year follow-up, the mean subsidence was 0.65 mm (0-1.40) in the AmisK group vs 0.68 mm (0.07-1.43) in the CK group (P = .73). When using a 1.5-mm threshold, none of the stems in either group was considered to have subsided. Femoral cortical thickening in zones 3 and 5 occurred in 6 of the 50 hips (12%) in the AmisK group vs 20 (40%) of the 50 hips in the CK group (P = .003).

Our study showed that a shortened highly polished double-tapered stem cemented line-to-line provided similar results including minimal subsidence as its standard-length counterpart, with significantly less distal femoral cortical thickening. However, longer term survival analysis still needs to be determined.

Sometimes the slightest changes in implant design can lead to failure, even for a validated prosthesis. A minimally invasive cementless model, the SL-PLUS MIA™, in which the lateral shoulder is eliminated, was developed from the Zweymüller SL-PLUS™ implant. After satisfactory in-vitro tests, it required in-vivo assessment to ensure that bone fixation is good. We therefore conducted a prospective randomized study comparing the two versions of the Zweymüller femoral stem, with the aim of (1) comparing bone fixation up to 2 years' follow-up on EBRA-FCA radiography; and (2) assessing any difference in clinical or radiographic performance.

Primary stability assessed on EBRA-FCA does not significantly differ between the SL-PLUS MIA™ and SL-PLUS™ implants.

A single-center multi-surgeon prospective randomized study included 80 patients (79 were operated on) between April 2009 and October 2012, with a mean 6 years' follow-up. Radiographic assessment used the EBRA-FCA application up to 2 years' follow-up; clinical assessment, with a minimum 5 years' follow-up, was performed by a single observer, using the Harris and Oxford-12 scores. The two groups, SL-PLUS™ (n=38) and SL-PLUS MIA™ (n=41), were comparable in gender, age, indications, body-mass index and preoperative functional status.

At a minimum 2 years' follow-up, 24 SL-PLUS™ and 27 SL-PLUS MIA™ implants were analyzed on EBRA-FCA. Mean migration was respectively -0.3mm±0.8 [range, -1.6 to 1.3] and -0.5mm±0.7 [range, -2.2 to 0.5] (p=0.21). There was likewise no significant difference in varus tilt. The number of ectopic ossifications did not differ, despite the absence of shoulder: 7 with SL-PLUS™ (23%), and 10 with SL-PLUS MIA™ (32%), without clinical impact. Oxford score improved from 43±6.8 to 19±7 at 5 years' follow-up with SL-PLUS ™ and from 44±8.8 to 20±7.4 with SL-PLUS MIA™: i.e., no significant inter-group difference. Likewise, Harris score at 2 years' follow-up did not differ: 91.6±8.7 and 89.7±10.2, respectively. Implant survival did not differ: SL-PLUS MIA™, 41/41 (100%); SL-PLUS™, 36/38 (94.7%) (p=0.13).

There was no significant difference in fixation quality between the SL-PLUS™ and SL-PLUS MIA™ implants. Elimination of the shoulder did not jeopardize primary or secondary fixation, but neither did it reduce the rate of ossification. The modified Zweymüller implant appeared risk-free at 6 years' follow-up.

II, low-power prospective randomized study.

The current trend is toward shorter hip stems. While there is a general agreement on the need for a cement mantle thicker than 2 mm, some surgeons prefer line-to-line cementation, where the mantle has only the thickness provided by the cement-bone interdigitation. The aim of this study was to assess if a relatively short, polished hip stem designed for a standard cementation can also be cemented line-to-line without increasing the risk of long-term loosening. Composite femurs with specific open-cell foam to allow cement-bone interdigitation were used. A validated in-vitro biomechanical cyclic test replicating long-term physiological loading was applied to femurs where the same stem was implanted with the Standard-mantle (optimal stem size) and Line-to-line (same rasp, one-size larger stem). Implant-bone motions were measured during the test. Inducible micromotions never exceeded 10 μm for both implant types (differences statistically not-significant). Permanent migrations ranged 50-300 μm for both implant types (differences statistically not-significant). While in the standard-mantle specimens there was a pronounced trend toward stabilization, line-to-line had less tendency to stabilize. The cement cracks were observed after the test by means of dye penetrants: The line-to-line specimens included the same cracks of the standard-mantle (but in the line-to-line specimens they were longer), and some additional cracks. The micromotions and cement damage were consistent with those observed in-vitro and clinically for stable stems, confirming that none of the specimens became dramatically loose. However, it seems that for this relatively short polished stem, standard-mantle cementation is preferable, as it results in less micromotion and less cement cracking. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2736-2744, 2018.

Matt and polished femoral stems have been historically grouped together in registry assessment of the outcome of cemented femoral stems in total hip arthroplasty. This is despite differences in the mode of fixation and biomechanics of loading. The aims of this study are to compare the survivorship of polished tapered stems with matt finished cemented stems.

Data on primary total hip arthroplasty undertaken for a diagnosis of osteoarthritis from September 1999 to December 2014 were included from a National Joint Registry. Revision rates of the 2 different types of femoral components were compared.

There were 96,315 cemented femoral stems included, of which 82,972 were polished tapered and 13,343 matt finish. The cumulative percent revision at 14 years of polished stems was 3.6% (3.0-4.2) compared to 4.9% (4.1-5.7) for matt finish stems. Polished tapered stems had a significantly lower revision rate of femoral revision (hazard ratio 0.56, P < .001). This difference is evident in patients aged <75, and becomes apparent in the mid-term and continues to increase with time. Aseptic loosening accounts for 75% of revisions of matt finish stems compared to 20% for polished tapered stems.

Although both polished and matt finish stems have excellent early to mid-term results, the long-term survivorship of polished stems is significantly better, with aseptic loosening becoming an issue with matt finish stems. In the future reports of cement fixation for femoral stems may benefit from separate analysis of polished and matt finish.

It is not known, whether outcome reporting in trials of total joint arthroplasty in the recent years is adequate or not. Our objective was to assess whether outcomes reported in total joint replacement (TJR) trials fulfil the Outcome Measures in Rheumatology (OMERACT) Filter 2.0.

We systematically reviewed all TJR trials in adults, published in English in 2008 or 2013. Searches were conducted in the Cochrane Central Register of Controlled Trials, MEDLINE, and EMBASE. Two authors independently applied the inclusion criteria for the studies, and any disagreement was resolved with a third review author. All outcome measures were abstracted using a pre-piloted standardised data extraction form and assessed for whether they mapped to one of the three OMERACT Filter 2.0 core areas: pathophysiological, life impact, and death.

From 1635 trials identified, we included 70 trials (30 in 2008 and 40 in 2013) meeting the eligibility criteria. Twenty-two (31%) trials reported the three essential OMERACT core areas. Among the 27 hip replacement surgery trials and 39 knee replacement surgery trials included, 11 hip (41%) and nine knee (23%) trials reported all three essential OMERACT core areas. The most common outcome domains/measures were pain (20/27, 74%) and function (23/27, 85%) in hip trials and pain (26/39, 67%) and function (27/39, 69%) in knee trials. Results were similar for shoulder and hand joint replacement trials.

We identified significant gaps in the measurement of OMERACT core outcome areas in TJR trials, despite the majority reporting outcome domains of pain and function. An international consensus of key stakeholders is needed to develop a core domain set for reporting of TJR trials.

PROSPERO CRD42014009216.

Previously published literature assessing the reporting of outcome measures used in joint replacement randomized controlled trials (RCT) has revealed disappointing results. It remains unknown whether international initiatives have led to any improvement in the quality of reporting and/or a reduction in the heterogeneity of outcome measures used. Our objective was to systematically assess and compare primary outcome measures and the risk of bias in joint replacement RCT published in 2008 and 2013.

We searched MEDLINE, EMBASE, and CENTRAL for RCT investigating adult patients undergoing joint replacement surgery. Two authors independently identified eligible trials, extracted data, and assessed risk of bias using the Cochrane tool.

Seventy RCT (30 in 2008, 40 in 2013) met the eligibility criteria. There was no significant difference in the number of trials judged to be at low overall risk of bias (n = 6, 20%) in 2008 compared with 2013 [6 (15%); chi-square = 0.302, p = 0.75]. Significantly more trials published in 2008 did not specify a primary outcome measure (n = 25, 83%) compared with 18 trials (45%) in 2013 (chi-square = 10.6316, p = 0.001). When specified, there was significant heterogeneity in the measures used to assess primary outcomes.

While less than a quarter of trials published in both 2008 and 2013 were judged to be at low overall risk of bias, significantly more trials published in 2013 specified a primary outcome. Although this might represent a temporal trend toward improvement, the overall frequency of primary outcome reporting and the wide heterogeneity in primary outcomes reported remain suboptimal.

There are 2 basic principles in cemented stem fixation: shape-closed and force-closed. We investigated 2 shape-closed straight stems, the Müller (MSS) and the Virtec (VSS), which differ only in geometrical cross section, to determine whether the difference in stem shape would affect the radiological results or long-term survival.

We included 711 hips (in 646 patients) that were operated on between July 1996 and July 2003. Patients randomly received either an MSS (n = 356) or a VSS (n = 355) and were followed prospectively. Radiographs taken at a follow-up of > 10 years were analyzed for osteolysis. Kaplan-Meier (KM) survival analysis was performed using various endpoints. We also performed Cox regression analysis to identify risk factors for aseptic loosening and osteolysis of the stem.

After 10 years, KM survival with "revision of any component for any reason" was 92% (95% CI: 88-95) for the MSS and 95% (CI: 92-97) for the VSS (p = 0.1). With "revision for aseptic loosening of the stem" as the endpoint, KM survival was 96% (CI: 9-98) for the MSS and 98% (CI: 97-100) for the VSS (p = 0.2). Cox regression showed that none of the risk factors analyzed were independent regarding aseptic loosening of the stem or regarding osteolysis.

The MSS and the VSS showed excellent survival for aseptic loosening after 10 years. For the 2 different stem designs, we did not find any independent risk factors for aseptic loosening or development of osteolysis.

Total hip replacement (THR) involves the replacement of a damaged hip joint with an artificial hip prosthesis. Resurfacing arthroplasty (RS) involves replacement of the joint surface of the femoral head with a metal surface covering.

To undertake clinical effectiveness and cost-effectiveness analysis of different types of THR and RS for the treatment of pain and disability in people with end-stage arthritis of the hip, in particular to compare the clinical effectiveness and cost-effectiveness of (1) different types of primary THR and RS for people in whom both procedures are suitable and (2) different types of primary THR for people who are not suitable for hip RS.

Electronic databases including MEDLINE, EMBASE, The Cochrane Library, Current Controlled Trials and UK Clinical Research Network (UKCRN) Portfolio Database were searched in December 2012, with searches limited to publications from 2008 and sample sizes of ≥ 100 participants. Reference lists and websites of manufacturers and professional organisations were also screened.

Systematic reviews of the literature were undertaken to appraise the clinical effectiveness and cost-effectiveness of different types of THR and RS for people with end-stage arthritis of the hip. Included randomised controlled trials (RCTs) and systematic reviews were data extracted and risk of bias and methodological quality were independently assessed by two reviewers using the Cochrane Collaboration risk of bias tool and the Assessment of Multiple Systematic Reviews (AMSTAR) tool. A Markov multistate model was developed for the economic evaluation of the technologies. Sensitivity analyses stratified by sex and controlled for age were carried out to assess the robustness of the results.

A total of 2469 records were screened of which 37 were included, representing 16 RCTs and eight systematic reviews. The mean post-THR Harris Hip Score measured at different follow-up times (from 6 months to 10 years) did not differ between THR groups, including between cross-linked polyethylene and traditional polyethylene cup liners (pooled mean difference 2.29, 95% confidence interval -0.88 to 5.45). Five systematic reviews reported evidence on different types of THR (cemented vs. cementless cup fixation and implant articulation materials) but these reviews were inconclusive. Eleven cost-effectiveness studies were included; four provided relevant cost and utility data for the model. Thirty registry studies were included, with no studies reporting better implant survival for RS than for all types of THR. For all analyses, mean costs for RS were higher than those for THR and mean quality-adjusted life-years (QALYs) were lower. The incremental cost-effectiveness ratio for RS was dominated by THR, that is, THR was cheaper and more effective than RS (for a lifetime horizon in the base-case analysis, the incremental cost of RS was £11,284 and the incremental QALYs were -0.0879). For all age and sex groups RS remained clearly dominated by THR. Cost-effectiveness acceptability curves showed that, for all patients, THR was almost 100% cost-effective at any willingness-to-pay level. There were age and sex differences in the populations with different types of THR and variations in revision rates (from 1.6% to 3.5% at 9 years). For the base-case analysis, for all age and sex groups and a lifetime horizon, mean costs for category E (cemented components with a polyethylene-on-ceramic articulation) were slightly lower and mean QALYs for category E were slightly higher than those for all other THR categories in both deterministic and probabilistic analyses. Hence, category E dominated the other four categories. Sensitivity analysis using an age- and sex-adjusted log-normal model demonstrated that, over a lifetime horizon and at a willingness-to-pay threshold of £20,000 per QALY, categories A and E were equally likely (50%) to be cost-effective.

A large proportion of the included studies were inconclusive because of poor reporting, missing data, inconsistent results and/or great uncertainty in the treatment effect estimates. This warrants cautious interpretation of the findings. The evidence on complications was scarce, which may be because of the absence or rarity of these events or because of under-reporting. The poor reporting meant that it was not possible to explore contextual factors that might have influenced study results and also reduced the applicability of the findings to routine clinical practice in the UK. The scope of the review was limited to evidence published in English in 2008 or later, which could be interpreted as a weakness; however, systematic reviews would provide summary evidence for studies published before 2008.

Compared with THR, revision rates for RS were higher, mean costs for RS were higher and mean QALYs gained were lower; RS was dominated by THR. Similar results were obtained in the deterministic and probabilistic analyses and for all age and sex groups THR was almost 100% cost-effective at any willingness-to-pay level. Revision rates for all types of THR were low. Category A THR (cemented components with a polyethylene-on-metal articulation) was more cost-effective for older age groups. However, across all age-sex groups combined, the mean cost for category E THR (cemented components with a polyethylene-on-ceramic articulation) was slightly lower and the mean QALYs gained were slightly higher. Category E therefore dominated the other four categories. Certain types of THR appeared to confer some benefit, including larger femoral head sizes, use of a cemented cup, use of a cross-linked polyethylene cup liner and a ceramic-on-ceramic as opposed to a metal-on-polyethylene articulation. Further RCTs with long-term follow-up are needed.

This study is registered as PROSPERO CRD42013003924.

The National Institute for Health Research Health Technology Assessment programme.

The optimal design for a cemented femoral stem remains a matter of debate. Over time, the shape, surface finish and collar have all been modified in various ways. A clear consensus has not yet emerged regarding the relative merits of even the most basic design features of the stem. We undertook a prospective randomised trial comparing surface finish and the effect of a collar on cemented femoral component subsidence, survivorship and clinical function.

One hundred and sixty three primary total hip replacement patients were recruited prospectively and randomised to one of four groups to receive a cemented femoral stem with either a matt or polished finish, and with or without a collar.

At two years, although there was a trend for increased subsidence in the matt collarless group, this was not statistically significant (p = 0.18). At a mean of 10.1 years follow-up, WOMAC scores for the surviving implants were good, (Range of means 89-93) without significant differences. Using revision or radiographic loosening as the endpoint, survivorship of the entire cohort was 93 % at 11 yrs, (CI 87-97 %). There were no significant differences in survivorship between the two groups with polished stems or the two groups with matt stems. A comparison of the two collarless stems demonstrated a statistically significant difference in survivorship between polished (100 %) and matt (88 %) finishes (p = 0.02).

In the presence of a collar, surface finish did not significantly affect survivorship or function. Between the two collarless groups a polished surface conferred an improved survivorship.

The Evora chromium-cobalt alloy dual mobility socket claims to display a large articulation tribology different from that of stainless steel models, limiting the risk of intraprosthetic dislocation and wear. The present study reports a minimum of 10years' follow-up in a multicenter prospective series of 200 sockets previously reported on at 5years.

The use of chromium-cobalt in dual mobility sockets provides a low rate of failure at 10years, especially as regards to osteolysis and intraprosthetic dislocation.

Two hundred hydroxyapatite-coated molded chromium-cobalt sockets without titanium interface were implanted without cement in 194 patients with a mean age of 70 years (range, 32-91 years). Clinical results were assessed on Postel Merle d'Aubigné and Harris scores, plain radiographs and survival analysis.

At a mean 11 years' follow-up (10-13 years), 56 patients had died and 31 were lost to follow-up. Four underwent surgical revision (3 femoral components, and 1 socket for migration at 9 years with complete disappearance of the hydroxyapatite). A total of 109 implants were analyzable in 107 patients with a mean age of 81 years (55-93 years). At follow-up, the mean Harris score was 90 (75-96) and the PMA score 16.3 (14-18). There were no cases of loosening (except for the case reoperated on at 9 years) and no acetabular radiolucency or cysts. There were 2 cases of non-evolutive femoral radiolucency and 10 of femoral granuloma, involving head size > 22 mm (P<0.0001) and a cemented titanium stem (P=0.004) as risk factors. There were no dislocations in the large or small articulation. Ten-year survival was 99% (95% CI: 97.3%-100%) with socket revision as censorship criterion.

The absence of dislocation in both small and large articulations confirmed the efficacy of the dual mobility concept and suggested an advantage for chromium-cobalt sockets in reducing the rate of intraprosthetic dislocation and preventing blockage of the large articulation by a better performance in the friction couple. Granulomas were associated with wear in cemented titanium stems and with heads greater than 22 mm in diameter. Ten-year survival was 99% (censorship criterion: revision for socket failure); there was, however, one case of socket loosening with disappearance of the hydroxyapatite, indicating that surveillance should be continued in this cohort.

To present the 18 year survival and the clinical and radiological outcomes of the Müller straight stem, cemented, total hip arthroplasty (THA).

Between 1989 and 2007, 176 primary total hip arthroplasties in 164 consecutive patients were performed in our institution by the senior author. All patients received a Müller cemented straight stem and a cemented polyethylene liner. The mean age of the patients was 62 years (45-78). The diagnosis was primary osteoarthritis in 151 hips, dysplasia of the hip in 12 and subcapital fracture of the femur in 13. Following discharge, serial follow-up consisted of clinical evaluation based on the Harris Hip Score and radiological assessment. The survival of the prosthesis using revision for any reason as an end-point was calculated by Kaplan-Meier analysis.

Twenty-four (15%) patients died during the follow-up study, 6 (4%) patients were lost, while the remaining 134 patients (141 hips) were followed-up for a mean of 10 years (3-18 years). HSS score at the latest follow-up revealed that 84 hips (59.5%) had excellent results, 30 (22.2%) good, 11 (7.8%) fair and 9 (6.3%) poor. There were 3 acetabular revisions due to aseptic loosening. Six (4.2%) stems were diagnosed as having radiographic definitive loosening; however, only 1 was revised. 30% of the surviving stems showed no radiological changes of radiolucency, while 70% showed some changes. Survival of the prosthesis for any reason was 96% at 10 years and 81% at 18 years.

The 18 year survival of the Müller straight stem, cemented THA is comparable to those of other successful cemented systems.

The dual mobility cup introduced in France by Gilles Bousquet has been used in total hip replacement in high-risk patients. This device acts as a large ball implant and significantly reduces the risk of dislocation following hip arthroplasty. Published French literature has focused on low rates of dislocation and long-term follow-up similar to the low-friction arthroplasty.

We retrospectively reviewed a continuous series of 105 cases of dual mobility cup Quattro (Groupe Lépine, Genay, France) implanted from 2000 to 2002. Selection of the patients requiring a primary hip replacement depended on risk criteria such as age, hip disease and activity score. The dual mobility cup was associated with a modular cemented femoral component and a 22.2-mm stainless steel head.

One dislocation occurred one month after the index surgery requiring no revision surgery. According to the Kaplan-Meier method, survival probability was 95.0% (95% confidence interval 81.5-98.8) at ten years of follow-up.

Based on clinical outcome and patient assessment we conclude that the dual mobility cup is a reliable option to decrease dislocation risk without increasing polyethylene wear.

Background and purpose Even small differences in design variables for the femoral stem may influence the outcome of a hip arthroplasty. We performed a risk factor analysis for aseptic loosening of 4 different versions of cemented Müller-type straight stems with special emphasis on design modifications (2 shapes, MSS or SL, and 2 materials, CoNiCrMo (Co) or Ti-6Al-7Nb (Ti)). Methods We investigated 828 total hip replacements, which were followed prospectively in our in-house register. All stems were operated in the same setup, using Sulfix-6 bone cement and a second-generation cementing technique. Demographic and design-specific risk factors were analyzed using an adjusted Cox regression model. Results The 4 versions showed marked differences in 15-year stem survival with aseptic loosening as the endpoint: 94% (95% CI: 89-99) for MSS Co, 83% (CI: 75-91) for SL Co, 81% (CI: 76-87) for MSS Ti and 63% (CI: 56-71) for SL Ti. Cox regression analysis showed a relative risk (RR) for aseptic loosening of 3 (CI: 2-5) for stems made of Ti and of 2 (CI: 1-2) for the SL design. The RR for aseptic stem loosening increased to 8 (CI: 4-15) when comparing the most and the least successful designs (MSS Co and SL Ti). Interpretation Cemented Müller-type straight stems should be MSS-shaped and made of a material with high flexural strength (e.g. cobalt-chrome). The surface finish should be polished (Ra < 0.4 µm). These technical aspects combined with modern cementing techniques would improve the survival of Müller-type straight stems. This may be true for all types of cemented stems.

The clinical outcomes and radiological findings for cemented titanium stems remain controversial. In 2004, we produced a straight-collared double-tapered stem made from a titanium alloy with a smooth surface for cemented total hip arthroplasty. In this study, we retrospectively examined the mid-term outcomes of this stem.

We retrospectively reviewed 61 hips that had undergone primary cemented total hip arthroplasty with a collared smooth double-tapered titanium alloy femoral stem, after a minimum of 5 years (mean 6.1, range 5.0-7.3). Patients were evaluated preoperatively and postoperatively with the Merle d'Aubigné and Postel hip score. Radiographic examination was performed for evaluation of the cementing technique, the alignment of the stem, subsidence within the cement mantle, radiolucent lines at the cement-bone or cement-stem interface, cortical hypertrophy, and calcar resorption.

The clinical evaluation by the Merle d'Aubigné and Postel hip score was improved from 9.4 ± 1.9 preoperatively to 15.9 ± 1.6 at the time of final follow-up. The overall survival rate was 100% at 7 years, when radiological loosening or revision for any reasons was used as the endpoint. Five stems subsided less than 1 mm vertically. Nonprogressive radiolucence at the cement-bone interface occurred in six hips, without osteolysis. Cortical hypertrophy was observed in five hips and second-degree calcar resorption in 11 hips.

Our results in this study show good outcomes for cemented, collared, smooth, double-tapered titanium alloy femoral stems at a minimum follow-up of 5 years.

The aim of this study was to obtain detailed long-term data on the cement-bone interface in patients with cemented stems, implanted using the constrained fixation technique. A total of eight stems were removed together with adjacent bone during post-mortem examinations of patients with well-functioning prostheses. Specimens were cut at four defined levels, contact radiographs were obtained for each level, and slices were prepared for histological analysis. Clinical data, clinical radiographs, contact radiographs and histological samples were examined for signs of loosening and remodelling. The mean radiological follow-up was 9.6 years and all stems were well-fixed, based on clinical and radiological criteria. Contact radiographs revealed an incomplete cement mantle but a complete filling of the medullary canal for all implants. Various amounts of polyethylene particles were evident at the cement-bone interface of seven stems, with no accompanying inflammatory reaction. Cortical atrophy and the formation of an 'inner cortex' were confirmed in six of eight stems by contact radiographs and histology, but were only visible on two clinical radiographs. Our results confirm that a complete cement mantle is not essential for the survival of Müller straight stems into the mid term, and support our hypothesis that no benefit to long-term survival can be expected from modern cementing techniques.

We have evaluated the in vivo migration patterns of 164 primary consecutive Charnley-Kerboull total hip replacements which were undertaken in 155 patients. The femoral preparation included removal of diaphyseal cancellous bone to obtain primary rotational stability of the stem before line-to-line cementing. We used the Ein Bild Roentgen Analyse femoral component method to assess the subsidence of the femoral component. At a mean of 17.3 years (15.1 to 18.3) 73 patients were still alive and had not been revised, eight had been revised, 66 had died and eight had been lost to follow-up. The mean subsidence of the entire series was 0.63 mm (0.0 to 1.94). When using a 1.5 mm threshold, only four stems were considered to have subsided. Our study showed that, in most cases, a highly polished double-tapered stem cemented line-to-line does not subside at least up to 18 years after implantation.

The original forged Müller straight stem (CoNiCr) has shown excellent ten- to 15-year results. We undertook a long-term survival analysis with special emphasis on radiological changes within a 20-year period of follow-up. In all, 165 primary total hip replacements, undertaken between July 1984 and June 1987 were followed prospectively. Clinical follow-up included a standardised clinical examination, and radiological assessment was based on a standardised anteroposterior radiograph of the pelvis, which was studied for the presence of osteolysis, debonding and cortical atrophy. Survival of the stem with revision for any reason was 81% (95% confidence interval (CI), 76 to 86) at 20 years and for aseptic loosening 87% (95% CI, 82 to 90). At the 20-year follow-up, 15 of the surviving 36 stems showed no radiological changes. Debonding (p = 0.005), osteolysis (p = 0.003) and linear polyethylene wear (p = 0.016) were associated with aseptic loosening, whereas cortical atrophy was not associated with failure (p = 0.008). The 20-year results of the Müller straight stem are comparable to those of other successful cemented systems with similar follow-up. Radiological changes are frequently observed, but with a low incidence of progression, and rarely result in revision. Cortical atrophy appears to be an effect of ageing and not a sign of loosening of the femoral component.

The main reason for revision of Charnley type total hip arthroplasty is socket loosening related to high polyethylene wear and periacetabular osteolysis. In these situations, the monobloc cemented stem is frequently not loosened and it is not clear whether the femoral component can be retained during the revision procedure. The aim of this study was to evaluate surface and sphericity damage to the femoral head of a prospective and consecutive series of revision total hip arthroplasties during which the cemented monobloc femoral component has been systematically revised.

We performed 22 revisions of both components of Charnley type cemented total hip arthroplasties. In all cases, the 22.2 mm head of the monobloc femoral component was made of 316 L stainless steel. The international standard for such femoral heads includes an average surface roughness (Ra) of 0.05 microm, a total roughness (Rt) value of 0.5 microm and a sphericity of +/-5 microm. The mean age of the patients at the time of the index arthroplasty was 51.3 years. The average time to revision was 14.8 years (seven to 25 years). The reasons for revision included isolated socket loosening (12), extensive periacetabular osteolysis without socket loosening (two), recurrent dislocation associated with socket loosening (one), sepsis without implant loosening (one), loosening of both components (one), and isolated loosening of the femoral component (five). Hence, 15 of the 22 (68.2%) femoral components could theoretically have been retained. The surface roughness of the femoral heads was evaluated using a contact-type profilometer. For each head, the apex and two zones, either macroscopically scratched or with loss of the mirror finish, were analyzed. Moreover, the sphericity of the heads was measured using a spherometer.

The stem explanted after recurrent dislocation was analyzed separately as the femoral head had major scratches. The mean Ra and Rt of the series at the apex was 0.029 and 0.876 microm, respectively. The mean Ra and Rt of the series for the macroscopically damaged areas was 0.05 microm and 1.540 microm, respectively. The mean sphericity of the series was 7.2 microm. Hence among the 22 explanted stems, 10 femoral heads (45.4%) had Ra or Rt apex and 18 (81.8%) Ra or Rt scratched area values beyond ISO standards, respectively. Sphericity was greater than +/-5mm for 13 of the 22 femoral heads (59.1%). With the numbers available, the age at the time of the index arthroplasty, the BMI, the time and the reason for revision were not significantly associated with the degree of femoral head damage for both roughness and sphericity parameters.

Retaining the femoral component during revision of the total hip arthroplasty including a monobloc femoral component is theoretically an interesting alternative. However, femoral head surface damage occurring in vivo would have lead us to retain severely scratched heads in over 80% of the hips, and heads with abnormal roughness and sphericity values in over 90% of the hips. Bases upon our results, we recommend systematically revising the femoral component during revision THA including a monobloc stem, irrespective of the reason for revision.