Aims. Uncemented mobile bearing designs in medial unicompartmental knee arthroplasty (UKA) have seen an increase over the last decade. However, there are a lack of large-scale studies comparing survivorship of these specific designs to commonly used cemented mobile and fixed bearing designs. The aim of this study was to evaluate the survivorship of these designs. Methods. A total of 21,610 medial UKAs from 2007 to 2018 were selected from the Dutch Arthroplasty Register. Multivariate Cox regression analyses were used to compare uncemented mobile bearings with cemented mobile and fixed bearings. Adjustments were made for patient and surgical factors, with their interactions being considered. Reasons and type of revision in the first two years after surgery were assessed. Results. In hospitals performing less than 100 cases per year, cemented mobile bearings reported comparable adjusted risks of revision as uncemented mobile bearings. However, in hospitals performing more than 100 cases per year, the adjusted risk of revision was higher for cemented mobile bearings compared to uncemented mobile bearings (hazard ratio 1.78 (95% confidence interval 1.34 to 2.35)). The adjusted risk of revision between cemented fixed bearing and uncemented mobile bearing was comparable, independent of annual hospital volume. In addition, 12.3% of uncemented mobile bearing, 20.3% of cemented mobile bearing, and 41.5% of uncemented fixed bearing revisions were for tibial component loosening. The figures for instability were 23.6%, 14.5% and 11.7%, respectively, and for periprosthetic fractures were 10.0%, 2.8%, and 3.5%. Bearing exchange was the type of revision in 40% of uncemented mobile bearing, 24.3% of cemented mobile bearing, and 5.3% cemented fixed bearing revisions. Conclusion. The findings of this study demonstrated improved survival with use of uncemented compared to cemented mobile bearings in medial UKA, only in those hospitals performing more than 100 cases per year. Cemented fixed bearings reported comparable survival results as uncemented mobile bearings, regardless of the annual hospital volume. The high rates of instability, periprosthetic fractures, and bearing exchange in uncemented mobile bearings emphasize the need for further research. Cite this article: Bone Joint J 2021;103-B(7):1261–1269

Aims

Despite the increasing numbers of ankle arthroplasties, there are limited studies on their survival and comparisons between different implants. The primary aim of this study was to determine the failure rates of primary ankle arthroplasties commonly used in the UK.

We have updated our previous randomised controlled trial comparing release of chromium (Cr) and cobalt (Co) ions and included levels of titanium (Ti) ions. We have compared the findings from 28 mm metal-on-metal total hip replacement, performed using titanium CLS/Spotorno femoral components and titanium AlloFit acetabular components with Metasul bearings, with Durom hip resurfacing using a Metasul articulation or bearing and a titanium plasma-sprayed coating for fixation of the acetabular component. Although significantly higher blood ion levels of Cr and Co were observed at three months in the resurfaced group than in total hip replacement, no significant difference was found at two years post-operatively for Cr, 1.58 μg/L and 1.62 μg/L respectively (p = 0.819) and for Co, 0.67 μg/L and 0.94 μg/L respectively (p = 0.207). A steady state was reached at one year in the resurfaced group and after three months in the total hip replacement group. Interestingly, Ti, which is not part of the bearing surfaces with its release resulting from metal corrosion, had significantly elevated ion levels after implantation in both groups. The hip resurfacing group had significantly higher Ti levels than the total hip replacement group for all periods of follow-up. At two years the mean blood levels of Ti ions were 1.87 μg/L in hip resurfacing and and 1.30 μg/L in total hip replacement (p = 0.001). The study confirms even with different bearing diameters and clearances, hip replacement and 28 mm metal-on-metal total hip replacement produced similar Cr and Co metal ion levels in this randomised controlled trial study design, but apart from wear on bearing surfaces, passive corrosion of exposed metallic surfaces is a factor which influences ion concentrations. Ti plasma spray coating the acetabular components for hip resurfacing produces significantly higher release of Ti than Ti grit-blasted surfaces in total hip replacement

Aims. The purpose of this study is to examine six types of bearing surfaces implanted at a single institution over three decades to determine whether the reasons for revision vary among the groups and how long it takes to identify differences in survival. Methods. We considered six cohorts that included a total of 1,707 primary hips done between 1982 and 2010. These included 223 conventional polyethylene sterilized with γ irradiation in air (CPE-GA), 114 conventional polyethylene sterilized with gas plasma (CPE-GP), 116 crosslinked polyethylene (XLPE), 1,083 metal-on-metal (MOM), 90 ceramic-on-ceramic (COC), and 81 surface arthroplasties (SAs). With the exception of the COC, all other groups used cobalt-chromium (CoCr) femoral heads. The mean follow-up was 10 (0.008 to 35) years. Descriptive statistics with revisions per 100 component years (re/100 yr) and survival analysis with revision for any reason as the endpoint were used to compare bearing surfaces. Results. XLPE liners demonstrated a lower cumulative incidence of revision at 15 years compared to the CPE-GA and CPE-GP groups owing to the absence of wear-related revisions (4% for XLPE vs 18%, p = 0.02, and 15%, p = 0.003, respectively). Revisions for adverse local tissue reactions occurred exclusively among the MOM (0.8 re/100 year) and SA groups (0.1 re/100 year). The revision rate for instability was lower among hips with 36 mm and larger head sizes compared to smaller head sizes (0.2% vs 2%, p < 0.001). Conclusion. The introduction of XLPE has eliminated wear-related revisions through 15-year follow-up compared to CPE-GP and CPE-GA. Dislocation incidence has been reduced with the introduction of larger diameter heads but remains a persistent concern. The potential for adverse local tissue reactions with MOM requires continued follow-up. Cite this article: Bone Joint J 2020;102-B(7 Supple B):105–111

Aims. Ceramic-on-ceramic (CoC) bearings in total hip arthroplasty (THA) are commonly used, but concerns exist regarding ceramic fracture. This study aims to report the risk of revision for fracture of modern CoC bearings and identify factors that might influence this risk, using data from the National Joint Registry (NJR) for England, Wales, Northern Ireland and the Isle of Man. Patients and Methods. We analysed data on 223 362 bearings from 111 681 primary CoC THAs and 182 linked revisions for bearing fracture recorded in the NJR. We used implant codes to identify ceramic bearing composition and generated Kaplan-Meier estimates for implant survivorship. Logistic regression analyses were performed for implant size and patient specific variables to determine any associated risks for revision. Results. A total of 222 852 bearings (99.8%) were CeramTec Biolox products. Revisions for fracture were linked to seven of 79 442 (0.009%) Biolox Delta heads, 38 of 31 982 (0.119%) Biolox Forte heads, 101 of 80 170 (0.126%) Biolox Delta liners and 35 of 31 258 (0.112%) Biolox Forte liners. Regression analysis of implant size revealed smaller heads had significantly higher odds of fracture (chi-squared 68.0, p < 0.001). The highest fracture risk was observed in the 28 mm Biolox Forte subgroup (0.382%). There were no fractures in the 40 mm head group for either ceramic type. Liner thickness was not predictive of fracture (p = 0.67). Body mass index (BMI) was independently associated with revision for both head fractures (odds ratio (OR) 1.09 per unit increase, p = 0.031) and liner fractures (OR 1.06 per unit increase, p = 0.006). . Conclusions. We report the largest independent study of CoC bearing fractures to date. The risk of revision for CoC bearing fracture is very low but previous studies have underestimated this risk. There is good evidence that the latest generation of ceramic has greatly reduced the odds of head fracture but not of liner fracture. Small head size and high patient BMI are associated with an increased risk of ceramic bearing fracture. Cite this article: Bone Joint J 2017;99-B:1012–19

Aims. Periprosthetic joint infection (PJI) is a serious complication of total hip arthroplasty (THA). Different bearing surface materials have different surface properties and it has been suggested that the choice of bearing surface may influence the risk of PJI after THA. The objective of this meta-analysis was to compare the rate of PJI between metal-on-polyethylene (MoP), ceramic-on-polyethylene (CoP), and ceramic-on-ceramic (CoC) bearings. Patients and Methods. Electronic databases (Medline, Embase, Cochrane library, Web of Science, and Cumulative Index of Nursing and Allied Health Literature) were searched for comparative randomized and observational studies that reported the incidence of PJI for different bearing surfaces. Two investigators independently reviewed studies for eligibility, evaluated risk of bias, and performed data extraction. Meta-analysis was performed using the Mantel–Haenzel method and random-effects model in accordance with methods of the Cochrane group. Results. Our search strategy revealed 2272 studies, of which 17 met the inclusion criteria and were analyzed. These comprised 11 randomized controlled trials and six observational studies. The overall quality of included studies was high but the observational studies were at high risk of bias due to inadequate adjustment for confounding factors. The overall cumulative incidence of PJI across all studies was 0.78% (1514/193 378). For each bearing combination, the overall incidence was as follows: MoP 0.85% (1353/158 430); CoP 0.38% (67/17 489); and CoC 0.53% (94/17 459). The meta-analysis showed no significant difference between the three bearing combinations in terms of risk of PJI. Conclusion. On the basis of the clinical studies available, there is no evidence that bearing choice influences the risk of PJI. Future research, including basic science studies and large, adequately controlled registry studies, may be helpful in determining whether implant materials play a role in determining the risk of PJI following arthroplasty surgery. Cite this article: Bone Joint J 2018;100-B:134–42

Aims. To establish our early clinical results of a new total knee arthroplasty (TKA) tibial component introduced in 2013 and compare it to other designs in use at our hospital during the same period. Methods. This is a retrospective study of 166 (154 patients) consecutive cemented, fixed bearing, posterior-stabilized (PS) TKAs (ATTUNE) at one hospital performed by five surgeons. These were compared with a reference cohort of 511 knees (470 patients) of other designs (seven manufacturers) performed at the same hospital by the same surgeons. There were no significant differences in age, sex, BMI, or follow-up times between the two cohorts. The primary outcome was revision performed or pending. Results. In total, 19 (11.5%) ATTUNE study TKAs have been revised at a mean 30.3 months (SD 15), and loosening of the tibial component was seen in 17 of these (90%). Revision is pending in 12 (7%) knees. There was no difference between the 31 knees revised or with revision pending and the remaining 135 study knees in terms of patient characteristics, type of bone cement (p = 0.988), or individual surgeon (p = 0.550). In the reference cohort, there were significantly fewer knees revised (n = 13, 2.6%) and with revision pending (n = 8, 1.5%) (both p < 0.001), and only two had loosening of the tibial component as the reason for revision. Conclusion. This new TKA design had an unexpectedly high early rate of revision compared with our reference cohort of TKAs. Debonding of the tibial component was the most common reason for failure. Additional longer-term follow-up studies of this specific component and techniques for implantation are warranted. The version of the ATTUNE tibial component implanted in this study has undergone modifications by the manufacturer. Cite this article: Bone Joint J 2021;103-B(6 Supple A):137–144

We reviewed the literature on the currently available choices of bearing surface in total hip replacement (THR). We present a detailed description of the properties of articulating surfaces review the understanding of the advantages and disadvantages of existing bearing couples. Recent technological developments in the field of polyethylene and ceramics have altered the risk of fracture and the rate of wear, although the use of metal-on-metal bearings has largely fallen out of favour, owing to concerns about reactions to metal debris. As expected, all bearing surface combinations have advantages and disadvantages. A patient-based approach is recommended, balancing the risks of different options against an individual’s functional demands. Cite this article: Bone Joint J 2014;96-B:147–56

Aims . The primary aim of this independent prospective randomised trial was to compare serum metal ion levels for ceramic-on-metal (CoM) and metal-on-metal (MoM) bearing surfaces in total hip arthroplasty (THA). Our one-year results demonstrated elevation in metal ion levels above baseline with no significant difference between the CoM and MoM groups. This paper reviews the five-year data. Patients and Methods. The implants used in each patient differed only in respect to the type of femoral head (ceramic or metal). At five-year follow-up of the 83 enrolled patients, data from 67 (36 CoM, 31 MoM) was available for comparison. Results. The mean serum cobalt (Co) and chromium (Cr) ion levels remained above baseline in both groups (CoM: Co 1.16 μg/l (0.41 to 14.67), Cr 1.05 μg/l (0.16 to 12.58); MoM: Co 2.93 μg/l (0.35 to 30.29), Cr 1.85 μg/l (0.36 to 17.00)) but the increase was significantly less in the CoM cohort (Co difference p = 0.001, Cr difference p = 0.002). These medium-term results, coupled with lower revision rates from national joint registries, suggest that the performance of CoM THA may be superior to that of MoM. . Conclusion. While both bearing combinations have since been withdrawn these results provide useful information for planning clinical surveillance of CoM THAs and warrants continued monitoring. Cite this article: Bone Joint J 2017;99-B:1298–1303

Aims. We wished to investigate the influence of metal debris exposure on the subsequent immune response and resulting soft-tissue injury following metal-on-metal (MoM) hip arthroplasty. Some reports have suggested that debris generated from the head-neck taper junction is more destructive than equivalent doses from metal bearing surfaces. . Patients and Methods. We investigated the influence of the source and volume of metal debris on chromium (Cr) and cobalt (Co) concentrations in corresponding blood and hip synovial fluid samples and the observed agglomerated particle sizes in excised tissues using multiple regression analysis of prospectively collected data. A total of 199 explanted MoM hips (177 patients; 132 hips female) were analysed to determine rates of volumetric wear at the bearing surfaces and taper junctions. . Results. The statistical modelling suggested that a greater source contribution of metal debris from the taper junction was associated with smaller aggregated particle sizes in the local tissues and a relative reduction of Cr ion concentrations in the corresponding synovial fluid and blood samples. Metal debris generated from taper junctions appears to be of a different morphology, composition and therefore, potentially, immunogenicity to that generated from bearing surfaces. Conclusion. The differences in debris arising from the taper and the articulating surfaces may provide some understanding of the increased incidence of soft-tissue reactions reported in patients implanted with MoM total hip arthroplasties compared with patients with hip resurfacings. Cite this article: Bone Joint J 2016;98-B:925–33

Aims

Patients with femoral neck fractures (FNFs) treated with total hip arthroplasty (THA) have an almost ten-fold increased risk of dislocation compared to patients undergoing elective THA. The surgical approach influences the risk of dislocation. To date, the influence of differing head sizes and dual-mobility components (DMCs) on the risk of dislocation has not been well studied.

The aim of this study was to evaluate the risk factors for dislocation of the bearing after a mobile-bearing Oxford medial unicompartmental knee replacement (UKR) and to test the hypothesis that surgical factors, as measured from post-operative radiographs, are associated with its dislocation. From a total of 480 UKRs performed between 2001 and 2012, in 391 patients with a mean age of 66.5 years (45 to 82) (316 female, 75 male), we identified 17 UKRs where bearing dislocation occurred. The post-operative radiological measurements of the 17 UKRs and 51 matched controls were analysed using conditional logistic regression analysis. The post-operative radiological measurements included post-operative change in limb alignment, the position of the femoral and tibial components, the resection depth of the proximal tibia, and the femoral component-posterior condyle classification. We concluded that a post-operative decrease in the posterior tibial slope relative to the pre-operative value was the only significant determinant of dislocation of the bearing after medial Oxford UKR (odds ratio 1.881; 95% confidence interval 1.272 to 2.779). A post-operative posterior tibial slope < 8.45° and a difference between the pre-operative and post-operative posterior tibial slope of > 2.19° may increase the risk of dislocation. Cite this article: Bone Joint J 2014; 96-B:914–22

Dislocation is a common reason for revision following total hip replacement. This study investigated the relationship between the bearing surface and the risk of revision due to dislocation. It was based on 110 239 primary total hip replacements with a diagnosis of osteoarthritis collected by the Australian Orthopaedic Association National Joint Replacement Registry between September 1999 and December 2007. A total of 862 (0.78%) were revised because of dislocation. Ceramic-on-ceramic bearing surfaces had a lower risk of requiring revision due to dislocation than did metal-on-polyethylene and ceramic-on-polyethylene surfaces, with a follow-up of up to seven years. However, ceramic-on-ceramic implants were more likely to have larger prosthetic heads and to have been implanted in younger patients. The size of the head of the femoral component and age are known to be independent predictors of dislocation. Therefore, the outcomes were stratified by the size of the head and age. There is a significantly higher rate of revision for dislocation in ceramic-on-ceramic bearing surfaces than in metal-on-polyethylene implants when smaller sizes (≤ 28 mm) of the head were used in younger patients (< 65 years) (hazard ratio = 1.53, p = 0.041) and also with larger (> 28 mm) and in older patients (≥ 65 years) (hazard ratio = 1.73, p = 0.016)

A number of studies have reported satisfactory results from the isolated revision of an acetabular component. However, many of these studies reported only the short- to intermediate-term results of heterogeneous bearing surfaces in a mixed age group. We present our experience of using a ceramic-on-ceramic (CoC) bearing for isolated revision of an uncemented acetabular component in 166 patients (187 hips) who were under the age of 50 years at the time of revision. There were 78 men and 88 women with a mean age of 47.4 years (28 to 49). The most common reason for revision was polyethylene wear and acetabular osteolysis in 123 hips (66%), followed by aseptic loosening in 49 hips (26%). . We report the clinical and radiological outcome, complication rate, and survivorship of this group. The mean duration of follow-up was 15.6 years (11 to 19). . The mean pre-operative Harris hip score was 33 points (1 to 58), and improved to a mean of 88 points (51 to 100) at follow-up. The mean pre-operative total Western Ontario and McMaster Universities Osteoarthritis Index score was 63.2 (43 to 91) and improved to 19.8 points (9 to 61) post-operatively. Overall, 153 of 166 patients (92%) were satisfied with their outcome. Kaplan–Meier survivorship analysis, with revision or radiological evidence of implant failure (13 patients, 8%) as end-points, was 92% at 15 years (95% confidence interval 0.89 to 0.97). . Isolated revision of a cementless acetabular component using a CoC bearing gives good results in patients under 50 years of age. Cite this article: Bone Joint J 2015;97-B:1197–1203

Polyethylene particulate wear debris continues to be implicated in the aetiology of aseptic loosening following knee arthroplasty. The Oxford unicompartmental knee arthroplasty employs a spherical femoral component and a fully congruous meniscal bearing to increase contact area and theoretically reduce the potential for polyethylene wear. This study measures the in vivo ten-year linear wear of the device, using a roentgenstereophotogrammetric technique. In this in vivo study, seven medial Oxford unicompartmental prostheses, which had been implanted ten years previously were studied. Stereo pairs of radiographs were acquired for each patient and the films were analysed using a roentgen stereophotogrammetric analysis calibration and a computer-aided design model silhouette-fitting technique. Penetration of the femoral component into the original volume of the bearing was our estimate of linear wear. In addition, eight control patients were examined less than three weeks post-insertion of an Oxford prosthesis, where no wear would be expected. The control group showed no measured wear and suggested a system accuracy of 0.1 mm. At ten years, the mean linear wear rate was 0.02 mm/year. The results from this in vivo study confirm that the device has low ten-year linear wear in clinical practice. This may offer the device a survival advantage in the long term

1 . A preliminary report is presented of a clinical trial to compare the results of early and late weight bearing in randomly selected patients of comparable age groups whose displaced femoral neck fractures were treated by internal fixation with a sliding nail-plate. 2. When 124 patients were assessed at three months and 107 at six months after operation there was no significant difference between those who started unguarded weight bearing two weeks after operation and those who avoided weight bearing for three months. 3. Early weight bearing appears to have no harmful effect on the early post-operative stability of this fracture when a sliding nail-plate is used for fixation. 4. Further information is necessary before any conclusion can be reached about the effect of early weight bearing on the ultimate fate of the fracture and of the femoral head. For this reason, and also to increase the numbers of patients in the series, the trial is continuing and the patients are being followed up for a three-year period

In a double-blinded randomised controlled trial, 83 patients with primary osteoarthritis of the hip received either a ceramic-on-metal (CoM) or metal-on-metal (MoM) total hip replacement (THR). The implants differed only in the bearing surfaces used. The serum levels of cobalt and chromium and functional outcome scores were compared pre-operatively and at six and 12 months post-operatively. Data were available for 41 CoM and 36 MoM THRs (four patients were lost to follow-up, two received incorrect implants). The baseline characteristics of both cohorts were similar. Femoral head size measured 36 mm in all but two patients who had 28 mm heads. The mean serum cobalt and chromium levels increased in both groups, with no difference noted between groups at six months (cobalt p = 0.67, chromium p = 0.87) and 12 months (cobalt p = 0.76, chromium p = 0.76) post-operatively. Similarly, the mean Oxford hip scores, Western Ontario and McMaster Universities Osteoarthritis index and University of California, Los Angeles activity scores showed comparable improvement at 12 months. Our findings indicate that CoM and MoM couplings are associated with an equivalent increase in serum cobalt and chromium levels, and comparable functional outcome scores at six and 12-months follow-up.

The ideal bearing surface for young patients undergoing total hip replacement (THR) remains controversial. We report the five-year results of a randomised controlled trial comparing the clinical and radiological outcomes of 102 THRs in 91 patients who were <  65 years of age. These patients were randomised to receive a cobalt–chrome on ultra-high-molecular-weight polyethylene, cobalt–chrome on highly cross-linked polyethylene, or a ceramic-on-ceramic bearing. In all, 97 hip replacements in 87 patients were available for review at five years. Two hips had been revised, one for infection and one for peri-prosthetic fracture. At the final follow-up there were no significant differences between the groups for the mean Western Ontario and McMaster Universities osteoarthritis index (pain, p = 0.543; function, p = 0.10; stiffness, p = 0.99), Short Form-12 (physical component, p = 0.878; mental component, p = 0.818) or Harris hip scores (p = 0.22). Radiological outcomes revealed no significant wear in the ceramic group. Comparison of standard and highly cross-linked polyethylene, however, revealed an almost threefold difference in the mean annual linear wear rates (0.151 mm/year versus 0.059 mm/year, respectively) (p < 0.001)

We performed 114 consecutive primary total hip arthroplasties with a cementless expansion acetabular component in 101 patients for advanced osteonecrosis of the femoral head. The mean age of the patients at surgery was 51 years (36 to 62) and the mean length of follow-up was 110 months (84 to 129). The mean pre-operative Harris hip score of 47 points improved to 93 points at final follow-up. The polyethylene liner was exchanged in two hips during this period and one broken acetabular component was revised. The mean linear wear rate of polyethylene was 0.07 mm/year and peri-acetabular osteolysis was seen in two hips (1.9%). Kaplan-Meier analysis indicated that the survival of the acetabular component without revision was 97.8% (95% confidence interval 0.956 to 1.000) at ten years. Our study has shown that the results of THA with a cementless expansion acetabular component and an alumina-polyethylene bearing surface are good

After a unicompartmental Oxford knee replacement, a clear lateral radiographic view of the components may be obtained without the shadow of prosthetic components in the other compartment. Radiographs of 20 knees were studied; with the patient supine and the muscles relaxed, views with the knee at full extension and 90 degrees of flexion were obtained and the movement of the meniscal bearings over this range of flexion was measured. The bearings were found to move backwards on the tibia through an average distance of 4.4 mm (range 0.0 to 13.5 mm) in the medial compartment and 6.0 mm (range 1.6 to 13.0 mm) in the lateral compartment. These movements were in the same direction as that observed in cadaver specimens but smaller in magnitude. At 90 degrees of flexion, radiographs were obtained with the tibia twisted manually to the limits of medial and lateral rotation. The average movement of the bearings between these extremes was found to be 6.6 mm in the medial compartment and 5.1 mm in the lateral; their movements on the tibia were in opposite directions in the two compartments. Bearing movement was still present in knees examined five years after operation

When the Oxford unicompartmental meniscal bearing arthroplasty is used in the lateral compartment of the knee, 10% of the bearings dislocate. A radiological review was carried out to establish if dislocation was related to surgical technique. The postoperative radiographs of 46 lateral unicompartmental arthroplasties were analysed. Five variables which related to the position and alignment of the components were measured. Dislocations occurred in six knees. Only one of the five variables, the proximal tibial varus angle, had a statistically significant relationship to dislocation. This variable quantifies the height of the lateral joint line. The mean proximal tibial varus angle for knees the bearings of which had dislocated was 9° and for those which had not it was 5°. In both groups it was greater than would be expected in the normal knee (3°). Our study suggests that a high proximal tibial varus angle is associated with dislocation. The surgical technique should be modified to account for this, with care being taken to avoid damage to or over-distraction of the lateral soft tissues

We have developed a CT-based navigation system using infrared light-emitting diode markers and an optical camera. We used this system to perform cementless total hip replacement using a ceramic-on-ceramic bearing couple in 53 patients (60 hips) between 1998 and 2001. We reviewed 52 patients (59 hips) at a mean of six years (5 to 8) postoperatively. The mid-term results of total hip replacement using navigation were compared with those of 91 patients (111 hips) who underwent this procedure using the same implants, during the same period, without navigation. There were no significant differences in age, gender, diagnosis, height, weight, body mass index, or pre-operative clinical score between the two groups. The operation time was significantly longer where navigation was used, but there was no significant difference in blood loss or navigation-related complications. With navigation, the acetabular components were placed within the safe zone defined by Lewinnek, while without, 31 of the 111 components were placed outside this zone. There was no significant difference in the Merle d’Aubigne and Postel hip score at the final follow-up. However, hips treated without navigation had a higher rate of dislocation. Revision was performed in two cases undertaken without navigation, one for aseptic acetabular loosening and one for fracture of a ceramic liner, both of which showed evidence of neck impingement on the liner. A further five cases undertaken without navigation showed erosion of the posterior aspect of the neck of the femoral component on the lateral radiographs. These seven impingement-related mechanical problems correlated with malorientation of the acetabular component. There were no such mechanical problems in the navigated group. We conclude that CT-based navigation increased the precision of orientation of the acetabular component and control of limb length in total hip replacement, without navigation-related complications. It also reduced the rate of dislocation and mechanical problems related to impingement

At the time of publication sixty-three additional patients have been fitted with the patellar tendon bearing prosthesis. Twenty of these were new amputees, and forty-three were old amputees who had previously worn a conventional limb. Of this group, nine were considered failures. The contra-indications for fitting now include: 1) coincident knee derangement such as cruciate or collateral ligament laxity (the trauma that causes the amputation often produces knee injuries as well; in this event the side irons of the conventional prosthesis help to support the knee); 2) scars in the popliteal fossa, such as those produced by exploration of the popliteal vessels; 3) marked variation in stump size such as in rapidly growing children or obese people; and 4) labourers obliged to work on rough ground, which places additional strain on the knee

Metal-on-metal (MOM) is a commonly used bearing notable for its ‘suction fit’ when lubricated. In this study, we examined the capacity for MOM bearings to protect against dislocation after total hip replacement (THR). We undertook a clinical investigation to compare the rate of dislocation of MOM bearings with those of ceramic-on-polyethylene (COP) bearings and found that one MOM bearing dislocated in a series of 109 hips (0.9%) compared with nine of 145 hips (6.2%) in the COP group (p = 0.02). We also performed an in vitro investigation comparing the peak forces generated during forced separation of the two bearings of the same dimensions at velocities from 1 to 50 cm/s. This revealed that the MOM bearing generated significant resistance to separation at all velocities (maximum mean 24 N), whereas the COP did not (maximum mean 1.9 N, p < 0.001). We conclude that MOM bearings are more stable to dislocation than COP bearings as a result of the interfacial forces provided by a thin, lubricating fluid

Aims

We sought to establish whether an oxidised zirconium (OxZr) femoral component causes less loss of polyethylene volume than a cobalt alloy (CoCr) femoral component in total knee arthroplasty.

Noise generation has been reported with ceramic-on-ceramic articulations in total hip replacement (THR). This study evaluated 208 consecutive Delta Motion THRs at a mean follow-up of 21 months (12 to 35). There were 141 women and 67 men with a mean age of 59 years (22 to 84). Patients were reviewed clinically and radiologically, and the incidence of noise was determined using a newly described assessment method. Noise production was examined against range of movement, ligamentous laxity, patient-reported outcome scores, activity level and orientation of the acetabular component. There were 143 silent hips (69%), 22 (11%) with noises other than squeaking, 17 (8%) with unreproducible squeaking and 26 (13%) with reproducible squeaking. Hips with reproducible squeaking had a greater mean range of movement (p < 0.001) and mean ligament laxity (p = 0.004), smaller median head size (p = 0.01) and decreased mean acetabular component inclination (p = 0.02) and anteversion angle (p = 0.02) compared with the other groups. There was no relationship between squeaking and age (p = 0.13), height (p = 0.263), weight (p = 0.333), body mass index (p = 0.643), gender (p = 0.07) or patient outcome score (p = 0.422). There were no revisions during follow-up. Despite the surprisingly high incidence of squeaking, all patients remain satisfied with their hip replacement.

Cite this article: Bone Joint J 2013;95-B:160–5.

Aims. The optimal bearing surface design for medial unicompartmental knee arthroplasty (UKA) remains controversial. The aim of this study was to compare outcomes of fixed-bearing (FB) and mobile-bearing (MB) UKAs from a single high-volume institution. Methods. Prospectively collected data were reviewed for all primary cemented medial UKAs performed by seven surgeons from January 2006 to December 2022. A total of 2,999 UKAs were identified, including 2,315 FB and 684 MB cases. The primary outcome measure was implant survival. Secondary outcomes included 90-day and cumulative complications, reoperations, component revisions, conversion arthroplasties, range of motion, and patient-reported outcome measures. Overall mean age at surgery was 65.7 years (32.9 to 94.3), 53.1% (1,593/2,999) of UKAs were implanted in female patients, and demographics between groups were similar (p > 0.05). The mean follow-up for all UKAs was 3.7 years (0.0 to 15.6). Results. Using revision for any reason as an endpoint, five-year survival for FB UKAs was 97.2% (95% CI 96.4 to 98.1) compared to 96.0% for MB (95% CI 94.1 to 97.9; p = 0.008). The FB group experienced fewer component revisions (14/2,315, 0.6% vs 12/684, 1.8%; p < 0.001) and conversion arthroplasties (38/2315, 1.6% vs 24/684, 3.5%; p < 0.001). A greater number of MB UKAs underwent revision due to osteoarthritis progression (FB = 21/2,315, 0.9% vs MB = 16/684, 2.3%; p = 0.003). In the MB group, 12 (1.8%) subjects experienced bearing dislocations which required revision surgery. There were 15 early periprosthetic tibia fractures (0.6%) in the FB group compared to 0 for MB (p = 0.035). Conclusion. In similar patient populations, FB UKAs demonstrated slightly higher survival than a commonly used MB design. Adverse event profiles differed by bearing type, with an increased risk of bearing dislocation and OA progression with MB designs, and early periprosthetic tibia fractures for FB designs. Cite this article: Bone Joint J 2024;106-B(9):916–923

Aims. Metal and ceramic humeral head bearing surfaces are available choices in anatomical shoulder arthroplasties. Wear studies have shown superior performance of ceramic heads, however comparison of clinical outcomes according to bearing surface in total shoulder arthroplasty (TSA) and hemiarthroplasty (HA) is limited. This study aimed to compare the rates of revision and reoperation following metal and ceramic humeral head TSA and HA using data from the National Joint Registry (NJR), which collects data from England, Wales, Northern Ireland, Isle of Man and the States of Guernsey. Methods. NJR shoulder arthroplasty records were linked to Hospital Episode Statistics and the National Mortality Register. TSA and HA performed for osteoarthritis (OA) in patients with an intact rotator cuff were included. Metal and ceramic humeral head prostheses were matched within separate TSA and HA groups using propensity scores based on 12 and 11 characteristics, respectively. The primary outcome was time to first revision and the secondary outcome was non-revision reoperation. Results. A total of 4,799 TSAs (3,578 metal, 1,221 ceramic) and 1,363 HAs (1,020 metal, 343 ceramic) were included. The rate of revision was higher for metal compared with ceramic TSA, hazard ratio (HR) 3.31 (95% confidence interval (CI) 1.67 to 6.58). At eight years, prosthesis survival for ceramic TSA was 98.7% (95% CI 97.3 to 99.4) compared with 96.4% (95% CI 95.2 to 97.3) for metal TSA. The majority of revision TSAs were for cuff insufficiency or instability/dislocation. There was no significant difference in the revision rate for ceramic compared with metal head HA (HR 1.33 (95% CI 0.76 to 2.34)). For ceramic HA, eight-year prosthetic survival was 92.8% (95% CI 86.9 to 96.1), compared with 91.6% (95% CI 89.3 to 93.5) for metal HA. The majority of revision HAs were for cuff failure. Conclusion. The rate of all-cause revision was higher following metal compared with ceramic humeral head TSA in patients with OA and an intact rotator cuff. There was no difference in the revision rate for HA according to bearing surface. Cite this article: Bone Joint J 2024;106-B(5):482–491

Aims. There is little information in the literature about the use of dual-mobility (DM) bearings in preventing re-dislocation in revision total hip arthroplasty (THA). The aim of this study was to compare the use of DM bearings, standard bearings, and constrained liners in revision THA for recurrent dislocation, and to identify risk factors for re-dislocation. Methods. We reviewed 86 consecutive revision THAs performed for dislocation between August 2012 and July 2019. A total of 38 revisions (44.2%) involved a DM bearing, while 39 (45.3%) and nine (10.5%) involved a standard bearing and a constrained liner, respectively. Rates of re-dislocation, re-revision for dislocation, and overall re-revision were compared. Radiographs were assessed for the positioning of the acetabular component, the restoration of the centre of rotation, leg length, and offset. Risk factors for re-dislocation were determined by Cox regression analysis. The modified Harris Hip Scores (mHHSs) were recorded. The mean age of the patients at the time of revision was 70 years (43 to 88); 54 were female (62.8%). The mean follow-up was 5.0 years (2.0 to 8.75). Results. DM bearings were used significantly more frequently in elderly patients (p = 0.003) and in hips with abductor deficiency (p < 0.001). The re-dislocation rate was 13.2% for DM bearings compared with 17.9% for standard bearings, and 22.2% for constrained liners (p = 0.432). Re-revision-free survival for DM bearings was 84% (95% confidence interval (CI) 0.77 to 0.91) compared with 74% (95% CI 0.67 to 0.81) for standard articulations, and 67% (95% CI 0.51 to 0.82) for constrained liners (p = 0.361). Younger age (hazard ratio (HR) 0.92 (95% CI 0.85 to 0.99); p = 0.031), lower comorbidity (HR 0.44 (95% CI 0.20 to 0.95); p = 0.037), smaller heads (HR 0.80 (95% CI 0.64 to 0.99); p = 0.046), and retention of the acetabular component (HR 8.26 (95% CI 1.37 to 49.96); p = 0.022) were significantly associated with re-dislocation. All DM bearings which re-dislocated were in patients with abductor muscle deficiency (HR 48.34 (95% CI 0.03 to 7,737.98); p = 0.303). The radiological analysis did not reveal a significant relationship between restoration of the geometry of the hip and re-dislocation. The mean mHHSs significantly improved from 43 points (0 to 88) to 67 points (20 to 91; p < 0.001) at the final follow-up, with no differences between the types of bearing. Conclusion. We found that the use of DM bearings reduced the rates of re-dislocation and re-revision in revision THA for recurrent dislocation, but did not guarantee stability. Abductor deficiency is an important predictor of persistent instability. Cite this article: Bone Joint J 2024;106-B(5 Supple B):89–97

Aims. Unicompartmental knee arthroplasty (UKA) has higher revision rates than total knee arthroplasty (TKA). As revision of UKA may be less technically demanding than revision TKA, UKA patients with poor functional outcomes may be more likely to be offered revision than TKA patients with similar outcomes. The aim of this study was to compare clinical thresholds for revisions between TKA and UKA using revision incidence and patient-reported outcomes, in a large, matched cohort at early, mid-, and late-term follow-up. Methods. Analyses were performed on propensity score-matched patient cohorts of TKAs and UKAs (2:1) registered in the New Zealand Joint Registry between 1 January 1999 and 31 December 2019 with an Oxford Knee Score (OKS) response at six months (n, TKA: 16,774; UKA: 8,387), five years (TKA: 6,718; UKA: 3,359), or ten years (TKA: 3,486; UKA: 1,743). Associations between OKS and revision within two years following the score were examined. Thresholds were compared using receiver operating characteristic analysis. Reasons for aseptic revision were compared using cumulative incidence with competing risk. Results. Fewer TKA patients with ‘poor’ outcomes (≤ 25) subsequently underwent revision compared with UKA at six months (5.1% vs 19.6%; p < 0.001), five years (4.3% vs 12.5%; p < 0.001), and ten years (6.4% vs 15.0%; p = 0.024). Compared with TKA, the relative risk for UKA was 2.5-times higher for ‘unknown’ reasons, bearing dislocations, and disease progression. Conclusion. Compared with TKA, more UKA patients with poor outcomes underwent revision from early to long-term follow-up, and were more likely to undergo revision for ‘unknown’ reasons, which suggest a lower clinical threshold for UKA. For UKA, revision risk was higher for bearing dislocations and disease progression. There is supporting evidence that the higher revision UKA rates are associated with lower clinical thresholds for revision and additional modes of failure. Cite this article: Bone Joint J 2023;105-B(3):269–276

Aims. Total knee arthroplasty (TKA) with a highly congruent condylar-stabilized (CS) articulation may be advantageous due to increased stability versus cruciate-retaining (CR) designs, while mitigating the limitations of a posterior-stabilized construct. The aim was to assess ten-year implant survival and functional outcomes of a cemented single-radius TKA with a CS insert, performed without posterior cruciate ligament sacrifice. Methods. This retrospective cohort study included consecutive patients undergoing TKA at a specialist centre in the UK between November 2010 and December 2012. Data were collected using a bespoke electronic database and cross-referenced with national arthroplasty audit data, with variables including: preoperative characteristics, intraoperative factors, complications, and mortality status. Patient-reported outcome measures (PROMs) were collected by a specialist research team at ten years post-surgery. There were 536 TKAs, of which 308/536 (57.5%) were in female patients. The mean age was 69.0 years (95% CI 45.0 to 88.0), the mean BMI was 32.2 kg/m. 2. (95% CI 18.9 to 50.2), and 387/536 (72.2%) survived to ten years. There were four revisions (0.7%): two deep infections (requiring debridement and implant retention), one aseptic loosening, and one haemosiderosis. Results. Kaplan-Meier analysis demonstrated no difference in implant survival according to sex, age, or obesity status. Ten-year PROMs were available for 196/387 (50.6%) surviving patients and were excellent: mean Oxford Knee Score 34.4 (95% CI 32.7 to 36.1); mean Forgotten Joint Score (FJS) 51.2 (95% CI 16.1 to 86.3); mean EuroQol five-dimension five-level questionnaire score 69.9 (95% CI 46.8 to 93.0); 141/196 (71.9%) achieved the 22-point FJS patient-acceptable symptom state (PASS); and 156/196 (79.6%) were “very satisfied or satisfied”. Conclusion. This is the only large study reporting ten-year implant survival and functional outcomes of TKA using a cemented single-radius design and with a CS tibial bearing construct. The findings of excellent implant survival, safety, and functional outcomes indicate that this combination is a safe and effective option in routine TKA. Further investigation of this single-radius design TKA with CS tibial bearings with well-matched patient study groups will allow further insight into the performance of these implants. Cite this article: Bone Joint J 2024;106-B(8):808–816

Aims. Oxidized zirconium (OxZi) and highly cross-linked polyethylene (HXLPE) were developed to minimize wear and risk of osteolysis in total hip arthroplasty (THA). However, retrieval studies have shown that scratched femoral heads may lead to runaway wear, and few reports of long-term results have been published. The purpose of this investigation is to report minimum ten-year wear rates and clinical outcomes of THA with OxZi femoral heads on HXLPE, and to compare them with a retrospective control group of cobalt chrome (CoCr) or ceramic heads on HXLPE. Methods. From 2003 to 2006, 108 THAs were performed on 96 patients using an OxZi head with a HXLPE liner with minimum ten-year follow-up. Harris Hip Scores (HHS) were collected preoperatively and at the most recent follow-up (mean 13.3 years). Linear and volumetric liner wear was measured on radiographs of 85 hips with a minimum ten-year follow-up (mean 14.5 years). This was compared to a retrospective control group of 45 THAs using ceramic or CoCr heads from October 1999 to February 2005, with a minimum of ten years’ follow-up. Results. Average HHS improved from 50.8 to 91.9 and 51.0 to 89.8 in the OxZi group and control group, respectively (p = 0.644), with no osteolysis in either group. Linear and volumetric wear rates in the OxZi group averaged 0.03 mm/year and 3.46 mm. 3. /year, respectively. There was no statistically significant difference in HHS scores, nor in linear or volumetric wear rate between the groups, and no revision for any indication. Conclusion. The radiological and clinical outcomes, and survivorship of THA with OxZi femoral heads and HXLPE liners, were excellent, and comparable to CoCr or ceramic heads at minimum ten-year follow-up. Wear rates are below what would be expected for development of osteolysis. OxZi-HXLPE is a durable bearing couple with excellent long-term outcomes. Cite this article: Bone Joint J 2024;106-B(3 Supple A):38–43

Aims. The Birmingham Hip Resurfacing (BHR) was introduced in 1997 to address the needs of young active patients using a historically proven large-diameter metal-on-metal (MoM) bearing. A single designer surgeon’s consecutive series of 130 patients (144 hips) was previously reported at five and ten years, reporting three and ten failures, respectively. The aim of this study was to extend the follow-up of this original cohort at 25 years. Methods. The study extends the reporting on the first consecutive 144 resurfacing procedures in 130 patients for all indications. All operations were undertaken between August 1997 and May 1998. The mean age at operation was 52.1 years (SD 9.93; 17 to 76), and included 37 female patients (28.5%). Failure was defined as revision of either component for any reason. Kaplan-Meier survival analysis was performed. Routine follow-up with serum metal ion levels, radiographs, and Oxford Hip Scores (OHSs) was undertaken. Results. Overall implant survival was 83.50% (95% confidence interval (CI) 0.79 to 0.90) at 25 years, and the number at risk was 79. Survival in male patients at 25 years was 89.5% (95% CI 0.83 to 0.96) compared to 66.9% for female patients (95% CI 0.51 to 0.83). Ten additional failures occurred in the period of ten to 25 years. These involved an adverse reaction to metal debris in four patients, a periprosthetic femoral neck fracture affecting five patients, and aseptic loosening in one patient. The median chromium levels were 49.50 nmol/l (interquartile range (IQR) 34 to 70), and the median cobalt serum levels were 42 nmol/l (IQR 24.50 to 71.25). The median OHS at last follow-up was 35 (IQR 10 to 48). During the 25-year study period, 29 patients died. Patient survival at 25 years was 75.10% (95% CI 0.67 to 0.83). Conclusion. This study demonstrates that MoM hip resurfacing using the BHR provides a durable alternative to total hip arthroplasty (THA), particularly in younger male patients with osteoarthritis wishing to maintain a high level of function. These results compare favourably to the best results for THAs. Cite this article: Bone Joint J 2024;106-B(6):540–547

Aims. To report mid- to long-term results of Oxford mobile bearing domed lateral unicompartmental knee arthroplasty (UKA), and determine the effect of potential contraindications on outcome. Methods. A total of 325 consecutive domed lateral UKAs undertaken for the recommended indications were included, and their functional and survival outcomes were assessed. The effects of age, weight, activity, and the presence of full-thickness erosions of cartilage in the patellofemoral joint on outcome were evaluated. Results. Median follow-up was seven years (3 to 14), and mean age at surgery was 65 years (39 to 90). Median Oxford Knee Score (OKS) was 43 (interquartile range (IQR) 37 to 47), with 260 (80%) achieving a good or excellent score (OKS > 34). Revisions occurred in 34 (10%); 14 (4%) were for dislocation, of which 12 had no recurrence following insertion of a new bearing, and 12 (4%) were revised for medial osteoarthritis (OA). Ten-year survival was 85% (95% confidence interval (CI) 79 to 90, at risk 72). Age, weight, activity, and patellofemoral erosions did not have a significant effect on the clinical outcome or survival. Conclusion. Domed lateral UKA provides a good alternative to total knee arthroplasty (TKA) in the management of lateral compartment OA. Although dislocation is relatively easy to treat successfully, the dislocation rate of 4% is high. It is recommended that the stability of the bearing is assessed intraoperatively. If the bearing can easily be displaced, the fixed rather than the mobile bearing version of the Oxford lateral tibial component should be inserted instead. Younger age, heavier weight, high activity, and patellofemoral erosions did not detrimentally affect outcome, so should not be considered contraindications. Cite this article: Bone Joint J 2020;102-B(8):1033–1040

Aims. The rate of dislocation when traditional single bearing implants are used in revision total hip arthroplasty (THA) has been reported to be between 8% and 10%. The use of dual mobility bearings can reduce this risk to between 0.5% and 2%. Dual mobility bearings are more expensive, and it is not clear if the additional clinical benefits constitute value for money for the payers. We aimed to estimate the cost-effectiveness of dual mobility compared with single bearings for patients undergoing revision THA. Methods. We developed a Markov model to estimate the expected cost and benefits of dual mobility compared with single bearing implants in patients undergoing revision THA. The rates of revision and further revision were calculated from the National Joint Registry of England and Wales, while rates of transition from one health state to another were estimated from the literature, and the data were stratified by sex and age. Implant and healthcare costs were estimated from local procurement prices and national tariffs. Quality-adjusted life-years (QALYs) were calculated using published utility estimates for patients undergoing THA. Results. At a minimum five-year follow-up, the use of dual mobility was cost-effective with an estimated incremental cost-effectiveness ratio (ICER) of between £3,006 and £18,745/QALY for patients aged < 55 years and between 64 and 75 years, respectively. For those aged > 75 years dual mobility was only cost-effective if the timeline was beyond seven years. The use of dual mobility bearings was cost-saving for patients aged < 75 years and cost-effective for those aged > 75 years if the time horizon was beyond ten years. Conclusion. The use of dual mobility bearings is cost-effective compared with single bearings in patients undergoing revision THA. The younger the patient is, the more likely it is that a dual mobility bearing can be more cost-effective and even cost-saving. The results are affected by the time horizon and cost of bearings for those aged > 75 years. For patients aged > 75 years, the surgeon must decide whether the use of a dual mobility bearing is a viable economic and clinical option. Cite this article: Bone Joint J 2020;102-B(9):1128–1135

Aims. The first aim of this study was to evaluate whether preoperative renal function is associated with postoperative changes in whole blood levels of metal ions in patients who have undergone a Birmingham Hip Resurfacing (BHR) arthroplasty with a metal-on-metal bearing. The second aim was to evaluate whether exposure to increased cobalt (Co) and chromium (Cr) levels for ten years adversely affected renal function. Methods. As part of a multicentre, prospective post-approval study, whole blood samples were sent to a single specialized laboratory to determine Co and Cr levels, and the estimated glomerular filtration rate (eGFR). The study included patients with 117 unrevised unilateral BHRs. There were 36 females (31%). The mean age of the patients at the time of surgery of 51.3 years (SD 6.5), and they all had preoperative one-, four-, five-, and ten-year laboratory data. The mean follow-up was 10.1 years (SD 0.2). Results. Median Co levels at one year postoperatively increased significantly compared with the preoperative values, by a factor of 9.7, from 0.13 to 1.26 ppb (p < 0.001), and the median Cr levels increased significantly by a factor of 2.5, from 0.60 to 1.50 ppb (p < 0.001). Lower preoperative eGFRs were associated with significantly larger increases in Co at one year compared with the preoperative levels (ρ = -0.26; p = 0.005), but there was no relationship between preoperative eGFRs and changes in Cr at one year (ρ = -0.13; p = 0.153). Metal levels remained relatively constant with the passage of time, with a median ten-year value of 1.12 ppb for Co and 1.29 ppb for Cr. There was no significant relationship between the Co and Cr levels at ten-year follow-up and the change in eGFR from the preoperative level to that at ten years (ρ = -0.02; p = 0.827 for Co; ρ = -0.008; p = 0.933 for Cr). Conclusion. Although patients with lower preoperative eGFRs tended to have larger increases in Co levels at one year, increased metal levels for patients who underwent unilateral BHR did not adversely affect renal function during the first ten postoperative years. Cite this article: Bone Joint J 2024;106-B(3 Supple A):44–50

Aims. Isolated acetabular liner exchange with a highly crosslinked polyethylene (HXLPE) component is an option to address polyethylene wear and osteolysis following total hip arthroplasty (THA) in the presence of a well-fixed acetabular shell. The liner can be fixed either with the original locking mechanism or by being cemented within the acetabular component. Whether the method used for fixation of the HXLPE liner has any bearing on the long-term outcomes is still unclear. Methods. Data were retrieved for all patients who underwent isolated acetabular component liner exchange surgery with a HXLPE component in our institute between August 2000 and January 2015. Patients were classified according to the fixation method used (original locking mechanism (n = 36) or cemented (n = 50)). Survival and revision rates were compared. A total of 86 revisions were performed and the mean duration of follow-up was 13 years. Results. A total of 20 patients (23.3%) had complications, with dislocation alone being the most common (8.1%; 7/86). Ten patients (11.6%) required re-revision surgery. Cementing the HXLPE liner (8.0%; 4/50) had a higher incidence of re-revision due to acetabular component liner-related complications than using the original locking mechanism (0%; 0/36; p = 0.082). Fixation using the original locking mechanism was associated with re-revision due to acetabular component loosening (8.3%; 3/36), compared to cementing (0%; 0/50; p = 0.038). Overall estimated mean survival was 19.2 years. There was no significant difference in the re-revision rate between the original locking mechanism (11.1%; 4/36) and cementing (12.0%; 6/50; p = 0.899). Using Kaplan-Meier survival analysis, the revision-free survival of HXLPE fixed with the original locking mechanism and cementing was 94.1% and 93.2%, respectively, at ten years, and 84.7% and 81.3%, respectively, at 20 years (p = 0.840). Conclusion. The re-revision rate and the revision-free survival following acetabular component liner exchange revision surgery using the HXLPE liner were not influenced by the fixation technique used. Both techniques were associated with good survival at a mean follow-up of 13 years. Careful patient selection is necessary for isolated acetabular component liner exchange revision surgery in order to achieve the best outcomes. Cite this article: Bone Joint J 2024;106-B(5 Supple B):59–65

Aims. The primary objective of this study was to compare migration of the cemented ATTUNE fixed bearing cruciate retaining tibial component with the cemented Press-Fit Condylar (PFC)-sigma fixed bearing cruciate retaining tibial component. The secondary objectives included comparing clinical and radiological outcomes and Patient Reported Outcome Measures (PROMs). Methods. A single blinded randomized, non-inferiority study was conducted including 74 patients. Radiostereometry examinations were made after weight bearing, but before hospital discharge, and at three, six, 12, and 24 months postoperatively. PROMS were collected preoperatively and at three, six, 12, and 24 months postoperatively. Radiographs for measuring radiolucencies were collected at two weeks and two years postoperatively. Results. The overall migration (mean maximum total point motion (MPTM)) at two years was comparable: mean 1.13 mm (95% confidence interval (CI), 0.97 to 1.30) for the ATTUNE and 1.16 mm (95% CI, 0.99 to 1.35) for the PFC-sigma. At two years, the mean backward tilting was -0.43° (95% CI, -0.65 to -0.21) for the ATTUNE and 0.08° (95% CI -0.16 to 0.31), for the PFC-sigma. Overall migration between the first and second postoperative year was negligible for both components. The clinical outcomes and PROMs improved compared with preoperative scores and were not different between groups. Radiolucencies at the implant-cement interface were mainly seen below the medial baseplate: 17% in the ATTUNE and 3% in the PFC-sigma at two weeks, and at two years 42% and 9% respectively (p = 0.001). Conclusion. In the first two postoperative years the initial version of the ATTUNE tibial component was not inferior with respect to overall migration, although it showed relatively more backwards tilting and radiolucent lines at the implant-cement interface than the PFC-sigma. The version of the ATTUNE tibial component examined in this study has subsequently undergone modification by the manufacturer. Level of Evidence: 1 (randomized controlled clinical trial). Cite this article: Bone Joint J 2020;102-B(9):1158–1166

Aims. The STRYDE nail is an evolution of the PRECICE Intramedullary Limb Lengthening System, with unique features regarding its composition. It is designed for load bearing throughout treatment in order to improve patient experience and outcomes and allow for simultaneous bilateral lower limb lengthening. The literature published to date is limited regarding outcomes and potential problems. We report on our early experience and raise awareness for the potential of adverse effects from this device. Methods. This is a retrospective review of prospective data collected on all patients treated in our institution using this implant. We report the demographics, nail accuracy, reliability, consolidation index, and cases where concerning clinical and radiological findings were encountered. There were 14 STRYDE nails implanted in nine patients (three male and six female) between June 2019 and September 2020. Mean age at surgery was 33 years (14 to 65). Five patients underwent bilateral lengthening (two femoral and three tibial) and four patients unilateral femoral lengthening for multiple aetiologies. Results. At the time of reporting, eight patients (13 implants) had completed lengthening. Osteolysis and periosteal reaction at the junction of the telescopic nail was evident in nine implants. Five patients experienced localized pain and swelling. Macroscopic appearances following retrieval were consistent with corrosion at the telescopic junction. Tissue histology was consistent with effects of focal metallic wear debris. Conclusion. From our early experience with this implant we have found the process of lengthening to be accurate and reliable with good regenerate formation and consolidation. Proposed advantages of early load bearing and the ability for bilateral lengthening are promising. We have, however, encountered concerning clinical and radiological findings in several patients. We have elected to discontinue its use to allow further investigation into the retrieved implants and patient outcomes from users internationally. Cite this article: Bone Joint J 2021;103-B(6):1168–1172

Aims. Wear of the polyethylene (PE) tibial insert of total knee arthroplasty (TKA) increases the risk of revision surgery with a significant cost burden on the healthcare system. This study quantifies wear performance of tibial inserts in a large and diverse series of retrieved TKAs to evaluate the effect of factors related to the patient, knee design, and bearing material on tibial insert wear performance. Methods. An institutional review board-approved retrieval archive was surveyed for modular PE tibial inserts over a range of in vivo duration (mean 58 months (0 to 290)). Five knee designs, totalling 1,585 devices, were studied. Insert wear was estimated from measured thickness change using a previously published method. Linear regression statistical analyses were used to test association of 12 patient and implant design variables with calculated wear rate. Results. Five patient-specific variables and seven implant-specific variables were evaluated for significant association with lower insert wear rate. Six were significant when controlling for other factors: greater patient age, female sex, shorter duration in vivo, polished tray, highly cross-linked PE (HXLPE), and constrained knee design. Conclusion. This study confirmed that knee wear rate increased with duration in vivo. Older patients and females had significantly lower wear rates. Polished modular tibial tray surfaces, HXLPE, and constrained TKA designs were device design factors associated with significantly reduced wear rate. Cite this article: Bone Joint J 2021;103-B(11):1695–1701

Aims. Proximal femoral endoprosthetic replacements (PFEPRs) are the most common reconstruction option for osseous defects following primary and metastatic tumour resection. This study aimed to compare the rate of implant failure between PFEPRs with monopolar and bipolar hemiarthroplasties and acetabular arthroplasties, and determine the optimum articulation for revision PFEPRs. Methods. This is a retrospective review of 233 patients who underwent PFEPR. The mean age was 54.7 years (SD 18.2), and 99 (42.5%) were male. There were 90 patients with primary bone tumours (38.6%), 122 with metastatic bone disease (52.4%), and 21 with haematological malignancy (9.0%). A total of 128 patients had monopolar (54.9%), 74 had bipolar hemiarthroplasty heads (31.8%), and 31 underwent acetabular arthroplasty (13.3%). Results. At a mean 74.4 months follow-up, the overall revision rate was 15.0%. Primary malignancy (p < 0.001) and age < 50 years (p < 0.001) were risk factors for revision. The risks of death and implant failure were similar in patients with primary disease (p = 0.872), but the risk of death was significantly greater for patients who had metastatic bone disease (p < 0.001). Acetabular-related implant failures comprised 74.3% of revisions; however, no difference between hemiarthroplasty or arthroplasty groups (p = 0.209), or between monopolar or bipolar hemiarthroplasties (p = 0.307), was observed. There was greater radiological wear in patients with longer follow-up and primary bone malignancy. Re-revision rates following a revision PFEPR was 34.3%, with dual-mobility bearings having the lowest rate of instability and re-revision (15.4%). Conclusion. Hemiarthroplasty and arthroplasty PFEPRs carry the same risk of revision in the medium term, and is primarily due to acetabular complications. There is no difference in revision rates or erosion between monopolar and bipolar hemiarthroplasties. The main causes of failure were acetabular wear in the hemiarthroplasty group and instability in the arthroplasty group. These risks should be balanced and patient prognosis considered when contemplating the bearing choice. Dual-mobility, constrained bearings, or large diameter heads (> 32 mm) are recommended in all revision PFEPRs. Cite this article: Bone Joint J 2021;103-B(10):1633–1640

Aims. This study compared the cobalt and chromium serum ion concentration of patients treated with two different metal-on-metal (MoM) hinged total knee arthroplasty (TKA) systems, as well as a titanium nitride (TiN)-coated variant. Methods. A total of 63 patients (65 implants) were treated using either a MoM-coated (n = 29) or TiN-coated (n = 7) hinged TKA (GenuX mobile bearing, MUTARS; Implantcast, Germany) versus the BPKS (Brehm, Germany) hinged TKA (n = 27), in which the weight placed on the MoM hinge is diffused through a polyethylene (PE) inlay, reducing the direct load on the MoM hinge. Serum cobalt and chromium ion concentrations were assessed after minimum follow-up of 12 months, as well as functional outcome and quality of life. Results. No differences in mean age (69 years, 40 to 86), mean age adapted Charlson Comorbidity Index (3.1 (SD 1.4)), mean BMI (29.2 kg/m. 2. (SD 5.8)), or number of other implants were observed between groups. Significant improvements in outcome scores and pain levels were achieved for all groups, and there was no difference in quality of life (12-Item Short-Form Health Survey questionnaire (SF-12)). Mean cobalt and chromium ion levels were significantly higher for the GenuX versus the BPKS hinged TKA (GenuX vs BPKS: cobalt: 16.3 vs 9.4 µg/l; chromium: 9.5 vs 5.2 µg/l). The TiN-coated implants did not appear to confer improvement in the metal ion levels. Metal ion concentrations above 7 µg/l were detected in 81%(29/36) of GenuX patients versus 41% (11/27) in the BPKS group. No GenuX patients had normal levels under 2 µg/l, versus 22% of BPKS patients. No significant reduction in outcome scores was observed regardless of the metal ion levels, whereas higher work-related activity was correlated with higher chromium concentrations. Conclusion. Hinged TKA, using MoM hinges, resulted in critically high cobalt and chromium ion concentrations. The BPKS hinged TKA showed significantly lower metal ion concentrations compared with the GenuX TKA. No benefits were observed using TiN coating. The different weightbearing mechanics might influence the wear of the component materials. Higher workloads and physical activity could influence chromium levels. Cite this article: Bone Joint J 2022;104-B(3):376–385

Aims. This is a multicentre, non-inventor, prospective observational study of 503 INFINITY fixed bearing total ankle arthroplasties (TAAs). We report our early experience, complications, and radiological and functional outcomes. Methods. Patients were recruited from 11 specialist centres between June 2016 and November 2019. Demographic, radiological, and functional outcome data (Ankle Osteoarthritis Scale, Manchester Oxford Questionnaire, and EuroQol five-dimension five-level score) were collected preoperatively, at six months, one year, and two years. The Canadian Orthopaedic Foot and Ankle Society (COFAS) grading system was used to stratify deformity. Early and late complications and reoperations were recorded as adverse events. Radiographs were assessed for lucencies, cysts, and/or subsidence. Results. In all, 500 patients reached six-month follow-up, 420 reached one-year follow-up, and 188 reached two-year follow-up. The mean age was 67.8 years (23.9 to 88.5). A total of 38 patients (7.5%) presented with inflammatory arthritis. A total of 101 (20.0%) of implantations used patient-specific instrumentation; 167 patients (33.1%) underwent an additional procedure at the time of surgery. A total of seven patients died of unrelated causes, two withdrew, and one was lost to follow-up. The mean follow-up was 16.2 months (6 to 36). There was a significant improvement from baseline across all functional outcome scores at six months, one, and two years. There was no significant difference in outcomes with the use of patient-specific instrumentation, type of arthritis, or COFAS type. Five (1.0%) implants were revised. The overall complication rate was 8.8%. The non-revision reoperation rate was 1.4%. The 30-day readmission rate was 1.2% and the one-year mortality 0.74%. Conclusion. The early experience and complications reported in this study support the current use of the INFINITY TAA as a safe and effective implant in the treatment of end-stage ankle arthritis. Cite this article: Bone Joint J 2021;103-B(7):1270–1276

Aims. Modular dual mobility (MDM) acetabular components are often used with the aim of reducing the risk of dislocation in revision total hip arthroplasty (THA). There is, however, little information in the literature about its use in this context. The aim of this study, therefore, was to evaluate the outcomes in a cohort of patients in whom MDM components were used at revision THA, with a mean follow-up of more than five years. Methods. Using the database of a single academic centre, 126 revision THAs in 117 patients using a single design of an MDM acetabular component were retrospectively reviewed. A total of 94 revision THAs in 88 patients with a mean follow-up of 5.5 years were included in the study. Survivorship was analyzed with the endpoints of dislocation, reoperation for dislocation, acetabular revision for aseptic loosening, and acetabular revision for any reason. The secondary endpoints were surgical complications and the radiological outcome. Results. The overall rate of dislocation was 11%, with a six-year survival of 91%. Reoperation for dislocation was performed in seven patients (7%), with a six-year survival of 94%. The dislocations were early (at a mean of 33 days) in six patients, and late (at a mean of 4.3 years) in four patients. There were three intraprosthetic dissociations. An outer head diameter of ≥ 48 mm was associated with a lower risk of dislocation (p = 0.013). Lumbrosacral fusion was associated with increased dislocation (p = 0.004). Four revision THAs (4%) were further revised for aseptic acetabular loosening, and severe bone loss (Paprosky III) at the time of the initial revision was significantly associated with further revision for aseptic acetabular loosening (p = 0.008). Fourteen acetabular components (15%) were re-revised for infection, and a pre-revision diagnosis of reimplantation after periprosthetic joint infection (PJI) was associated with subsequent PJI (p < 0.001). Two THAs had visible metallic changes on the backside of the cobalt chromium liner. Conclusion. When using this MDM component in revision THA, at a mean follow-up of 5.5 years, there was a higher rate of dislocation (11%) than previously reported. The size of the outer bearing was related to the risk of dislocation. There was a low rate of aseptic acetabular loosening. Longer follow-up of this MDM component and evaluation of other designs are warranted. Cite this article: Bone Joint J 2021;103-B(7 Supple B):66–72

Aims. The aim of this independent multicentre study was to assess the mid-term results of mobile bearing unicondylar knee arthroplasty (UKA) for isolated lateral osteoarthritis of the knee joint. Patients and Methods. We retrospectively evaluated 363 consecutive, lateral UKAs (346 patients) performed using the Oxford domed lateral prosthesis undertaken in three high-volume knee arthroplasty centres between 2006 and 2014. Mean age of the patients at surgery was 65 years (36 to 88) with a mean final follow-up of 37 months (12 to 93). Results. A total of 36 (10.5%) patients underwent revision surgery, giving a survival rate of 90.1% at three years (95% confidence intervals (CI) 86.1 to 93.1; number at risk: 155) and 85.0% at five years (95% CI 77.9 to 89.9; number at risk: 43). Dislocation of the mobile bearing occurred in 18 patients (5.6%) at three years (95% CI 1.0 to 16.4; number at risk: 154) and in 20 patients (8.5%) at five years (95% CI 1.0 to 27.0; number at risk: 42). There were no significant differences in the dislocation rate between the participating centres or the surgeons. We were not able to identify an effect of each surgeon’s learning curve on the dislocation rate of the mobile bearing. The clinical outcome in patients without revision surgery at final follow-up was good to excellent, with a mean Oxford knee score of 40.3 (95% CI 39.4 to 41.2), a mean Tegner activity score of 3.2 (95% CI 3.1 to 3.3) and a mean University of California, Los Angeles score of 5.7 (95% CI 5.5 to 5.9). Conclusion. Our data, which consists of a high number of patients treated with mobile bearing UKA in the lateral compartment, indicates a high revision rate of 15% at five years with dislocation of the mobile bearing being the main reason for implant failure. Despite the good functional and clinical results and the high patient satisfaction in our study group, we therefore discontinued using mobile-bearing lateral UKA in favour of a fixed-bearing component. Cite this article: Bone Joint J 2018;100-B:42–9

Aims. Highly cross-linked polyethylene (HXLPE) has greatly improved the durability of total hip arthroplasty (THA) in young patients because of its improved wear characteristics. Few studies have followed this population into the second decade, and therefore the purpose of this investigation was to evaluate the clinical outcome for THA patients 50 years of age and younger at a minimum of 15 years postoperatively. The second purpose was to evaluate the radiological findings secondary to wear or mechanical failure of the implant. Methods. Between October 1999 and December 2005, 105 THAs were performed in 95 patients (53 female, 42 male) aged 50 years and younger (mean 42 years (20 to 50)). There were 87 patients (96 hips) that were followed for a minimum of 15 years (mean 17.3 years (15 to 21)) for analysis. Posterior approach was used with cementless fixation with a median head size of 28 mm. HXLPE was the acetabular bearing for all hips. Radiographs were evaluated for polyethylene wear, radiolucent lines, and osteolysis. Results. Clinical outcomes showed significant improvement of mean Harris Hip Scores from 52.8 (SD 13.5) preoperatively to 94.8 (SD 7.6) postoperatively. One hip was revised for recurrent instability, and there were no infections. No hips were revised for mechanical loosening or osteolysis. Mean polyethylene linear wear was 0.04 mm/year and volumetric wear was 6.22 mm. 3. /year, with no significant differences between head size or material. Osteolysis was not present in any of the hips. Conclusion. The use of HXLPE in THA for patients aged 50 years and younger has performed exceptionally well without evidence of significant wear causing mechanical loosening or necessitating revision. The radiolucent lines of the acetabular component must be followed to determine the prognostic significance. This investigation represents the longest clinical follow-up of a large, consecutive cohort of patients aged 50 years or younger with THA using HXLPE. This long-term analysis found negligible polyethylene wear, no incidence of aseptic loosening, and excellent clinical outcomes at and beyond 15 years of follow-up. Cite this article: Bone Joint J 2021;103-B(7 Supple B):78–83

Aims. Modern total knee arthroplasty (TKA) prostheses are designed to restore near normal kinematics including high flexion. Kneeling is a high flexion, kinematically demanding activity after TKA. The debate about design choice has not yet been informed by six-degrees-of-freedom in vivo kinematics. This prospective randomized clinical trial compared kneeling kinematics in three TKA designs. Methods. In total, 68 patients were randomized to either a posterior stabilized (PS-FB), cruciate-retaining (CR-FB), or rotating platform (CR-RP) design. Of these patients, 64 completed a minimum one year follow-up. Patients completed full-flexion kneeling while being imaged using single-plane fluoroscopy. Kinematics were calculated by registering the 3D implant models onto 2D-dynamic fluoroscopic images and exported for analysis. Results. CR-FB designs had significantly lower maximal flexion (mean 116° (SD 2.1°)) compared to CR-RP (123° (SD 1.6°)) and PS-FB (125° (SD 2.1°)). The PS-FB design displayed a more posteriorly positioned femur throughout flexion. Furthermore, the CR-RP femur was more externally rotated throughout kneeling. Finally, individual patient kinematics showed high degrees of variability within all designs. Conclusion. The increased maximal flexion found in the PS-FB and CR-RP designs were likely achieved in different ways. The PS-FB design uses a cam-post to hold the femur more posteriorly preventing posterior impingement. The external rotation within the CR-RP design was surprising and hasn’t previously been reported. It is likely due to the polyethylene bearing being decoupled from flexion. The findings of this study provide insights into the function of different knee arthroplasty designs in the context during deep kneeling and provide clinicians with a more kinematically informed choice for implant selection and may allow improved management of patients' functional expectations. Cite this article: Bone Joint J 2021;103-B(1):105–112

Aims. Instability continues to be a troublesome complication after total hip arthroplasty (THA). Patient-related risk factors associated with a higher dislocation risk include the preoperative diagnosis, an age of 75 years or older, high body mass index (BMI), a history of alcohol abuse, and neurodegenerative diseases. The goal of this study was to assess the dislocation rate, radiographic outcomes, and complications of patients stratified as high-risk for dislocation who received a dual mobility (DM) bearing in a primary THA at a minimum follow-up of two years. Materials and Methods. We performed a retrospective review of a consecutive series of DM THA performed between 2010 and 2014 at our institution (Hospital for Special Surgery, New York, New York) by a single, high-volume orthopaedic surgeon employing a single prosthesis design (Anatomic Dual Mobility (ADM) Stryker, Mahwah, New Jersey). Patient medical records and radiographs were reviewed to confirm the type of implant used, to identify any preoperative risk factors for dislocation, and any complications. Radiographic analysis was performed to assess for signs of osteolysis or remodelling of the acetabulum. Results. There were 151 patients who met the classification of high-risk according to the inclusion criteria and received DM THA during the study period. Mean age was 82 years old (73 to 95) and 114 patients (77.5%) were female. Mean follow-up was 3.6 years (1.9 to 6.1), with five patients lost to follow-up and one patient who died (for a reason unrelated to the index procedure). One patient (0.66%) sustained an intraprosthetic dislocation; there were no other dislocations. Conclusion. At mid-term follow-up, the use of a DM bearing for primary THA in patients at high risk of dislocation provided a stable reconstruction option with excellent radiographic results. Longer follow-up is needed to confirm the durability of these reconstructions