We have evaluated the difference in the migration patterns over two years of two cementless stems in a randomised, controlled trial using radiostereophotogrammetric analysis (RSA). The implants studied were the Furlong HAC stem, which has good long-term results and the Furlong Active stem, which is a modified version of the former designed to minimise stress concentrations between the implant and bone, and thus to improve fixation. A total of 23 Furlong HAC and 20 Furlong Active stems were implanted in 43 patients. RSA examinations were carried out immediately post-operatively and at six, 12 and 24 months post-operatively. The subsidence during the first year in the Furlong HAC stem, was approximately one-third that of the Furlong Active stem, the measured mean subsidence of the femoral head at six months being 0.27 mm (95% confidence interval (CI) 0.03 to 0.51) and 0.99 mm (95% CI 0.38 to 1.60), respectively (p = 0.03). One Active stem continued to subside during the second year. All hips, regardless of the type of stem were clinically successful as judged by the Oxford hip score and a derived pain score without any distinction between the two types of stem. The initial stability of the Furlong Active stem was not as good as the established stem which might compromise osseo-integration to the detriment of long-term success. The changes in the geometry of the stem, to minimise stress have affected the attainment of initial stability

Introduction Mobile-bearing total ankle arthroplasty has gained more interest in recent years. Clinical results show favourable but varying results, with survival rates between 70% and 90% at 10-year follow-up. Design-specific differences in early migration patterns might explain differences in result and possible modes of failure. Methods Prospective study of a cementless mobile-bearing total ankle arthroplasty by radiostereometric analysis (RSA). Fifteen total ankle arthroplasties were performed in patients with rheumatoid arthritis. The American Orthopaedic Foot and Ankle Society ankle score and radiostereometric radiographs were evaluated at regular intervals throughout the follow-up period: immediately postoperatively, 6 weeks postoperatively, 3 months, 6 months, and 12 months postoperatively and yearly thereafter. Results The postoperative clinical results improved. We observed increased migration of the tibial component during the first 3 months, but this stabilized by the 6-months followup. The mean lateral-medial migration was 0.8 mm, distal-proximal migration was 0.9 mm, and posteroanterior migration was −0.5 mm. The latter implicated that the total resultant migration was in anterior and valgus tilting of this tibial component. This resulted in a main mode of migration proximal, anterior and valgus tilting of the tibial component. Discussion This pilot study showed initial migration of this mobile-bearing ankle prosthesis into upward anterior and valgus tilting. However, migration stabilized at 6 months postoperatively. We think the surgical technique (anterior cortical window for placement) and the method of tibial fixation likely explain this migration

Introduction and Aims: Recently, concerns have emerged regarding the high stiffness of acetabular components inserted with alumina ceramic liners, which might potentially cause early migration and loosening. This study was designed to investigate in-vivo the migration pattern of these constructs. Method: Fifty patients (50 hips) operated on using the same surgical technique and the same prosthesis were randomised in two groups. The study group of hips was treated with an alumina ceramic liner, the control group of hips received a polyethylene liner. An alumina femoral head with a diameter of 28mm was used in all hips. Radiostereometric analysis (RSA) was performed to assess migration using serial follow-up radiographs. Results: The median pre-operative Harris hip score (HHS) was rated 48.9 points in the alumina group, and 47.7 points in the polyethylene group. At the two-year follow-up, the median HHS of the alumina group was rated 94.1 points, and was rated 93.7 points in the polyethylene group. There were no clinical or radiological signs of aseptic loosening. RSA of the alumina group of cups showed a median axial displacement of 0.026 mm (SD 0.35mm). The median axial displacement of the polyethylene group was 0.047 mm (SD 0.26 mm) (p=0.9). The median tilting of the cup was 0.21 degrees (SD 0.54 degrees) in the alumina group, and 0.35 degrees (SD 0.71 degrees) in the polyethylene group (p=0.12). Conclusion: At an average of two years post-operatively, the cups inserted with an alumina ceramic liner appeared stable, RSA showed low rates of non-progressive migration. Results did not differ from those observed using the same cup inserted with a polyethylene liner

Introduction. Modern cementless press fit stems rely on early fixation and stability for osteointegration and longterm success with early migration increasing the risk of failure. The Ein Bild Roentegen Analyse Femoral Component Analysis (EBRA-FCA) methods allow accurate measurement of femoral stem subsidence without the need for Tantalum markers. The degree of subsidence of femoral stems in the first two years has been shown to be highly predictive of failure when using the cut off value of 1.5 mm. We aimed to measure the early migration pattern of a titanium alloy, tapered, plasma and hydroxyapatite coated femoral stem and any factors associated with subsidence. Methods. Between January 2005-June 2007, 387 Accolade cementless femoral stems (Stryker, Allendale NJ) were implanted at our institution. Seventy-seven had a minimum of two years post operative follow up and a complete set of pre and postoperative radiographs for analysis. Our group inlcuded 45 females with a mean age of 71.4 years, and 32 males with a mean age of 68.5 years. The primary diagnosis was degenerative osteoarthritis in 71 patients, avascular necrosis in two, and post fracture in four patients. The average BMI was 27.1. We measured the canal index to assess bone quality and the canal calcar index to assess the proximal femoral morphology. Immediate postoperative radiographs were assessed for canal fill of the prosthesis and implantation varus/valgus angles. The EBRA-FCA software was used to obtain migration curves for each stem. Results. The mean follow up was 29.3months (24–48). The mean canal index was 0.55 (0.36–0.68) with a mean canal calcar index of 0.54 (0.39–0.79). The average canal fill index at the midpoint of the stem was <0.8 in 37 stems and >80 in 40 stems. The average subsidence at 24 months was 2 mm and this had risen to 2.4 mm by 36 months postoperatively. When analysed using a Kaplan Meier curve using 1.5 mm as an end point we found a survivorship of 63.4% (52.3–74.5) at 24 months and this had worsened to 41.6% (26.6–56.5) by 36 months. Multivariate and univariate regression analysis of measured variables did not reveal any significant hazard for any factor other than the larger stem sizes doing worse. Discussion. Although several cementless tapered stem designs have had an excellent track record, our migration analysis of the Accolade stem is somewhat concerning. Thirty three percent of stems had reached the 1.5 mm subsidence point by two years. This is of concern as work has previously shown this to predict failure of stems with aseptic loosening at ten years with an accuracy of 79%. If these stems go on to fail at the predicted rate this would represent an unacceptably high level of failure. Our data raises serious concerns about the overall clinical performance of this stem design due to poor initial stability and integration

Aseptic loosening is the most frequent cause of implant failure in total hip arthroplasty (THA). Additionally, failure rate was still found by some authors to be increased in patients with osteonecrosis of the femoral head (ON-FH). It is well evidenced that low initial fixation and early migration precedes and predicts long-term failure rate of both, the acetabular and femoral component in THA. This independent, double-blind, randomized, controlled study was primarily designed to evaluate whether a single infusion of 4 mg of zoledronic acid is sufficient to prevent implant migration determined by the EBRA-digital method. Fifty patients were consecutively enrolled between July 2002 and March 2005 to receive either 4 mg zoledronic acid (ZOL) or saline solution (CTR) one day after THA (Zweymüller system, cementless). Plain radiographs were performed postoperatively and all parameters were evaluated at each follow-up meeting interval at 7 weeks, 6 months, 1 year, and yearly thereafter during a median follow-up period of 2.8 years (2 years minimum). In CTR, subsidence increased up to −1.2 mm ± 0.6 SD at 2 years in CTR (P< 0.001). Less, but a near curve-linear shaped migration pattern was found for the ace-tabular component, with an averaged medialization of 0.6 mm ± 1.0 SD and a cranialization of 0.6 mm ± 0.8 SD at 2 years (P< 0.05, Friedman ANOVA) at 2 years. In ZOL, a significant reduction in bone turnover markers was accompanied by a complete prevention of cup migration in both, the transverse and vertical direction (P< 0.05, ANOVA), while there was only a trend to a decreased subsidence in stems. The study provides useful data which are promising and support the suggestions that bisphosphonates may offer significant opportunities to reduce and prevent implant migration of THA, thus increasing long-term durability of THA especially in selected high-risk patients

Purpose: We aimed to measure the early migration pattern of a titanium alloy, tapered, plasma and hydroxyapatite coated femoral stem and any factors associated with subsidence. Method: Between January 2005–June 2007, 387 Accolade cementless femoral stems (Stryker, Allendale NJ) were implanted at our institution. Seventy-seven had a minimum of two years post operative follow up and a complete set of pre and postoperative radiographs for analysis. Our group inlcuded 45 females with a mean age of 71.4 years, and 32 males with a mean age of 68.5 years. The primary diagnosis was degenerative osteoarthritis in 71 patients, avascular necrosis in two, and post fracture in four patients. The average BMI was 27.1. We measured the canal index to assess bone quality and the canal calcar index to assess the proximal femoral morphology. Immediate postoperative radiographs were assessed for canal fill of the prosthesis and implantation varus/valgus angles. The EBRA-FCA software was used to obtain migration curves for each stem. Best fit curve of subsidence over time was calculated and the data was analysed using a Kaplan Meier survivorship with 1.5 mm of subsidence as an endpoint. We then performed a multivariate and univariate regression analysis for predictors of subsidence. Results: The mean follow up was 29.3months (24–48). The mean canal index was 0.55 (0.36–0.68) with a mean canal calcar index of 0.54 (0.39–0.79). The average canal fill index at the midpoint of the stem was 80 in 40 stems. A total of 414 radiographs were analysed for the EBRA measurements. Of these 21 (5%) were discarded by the software as they did not meet the criteria for comparability. This led to the exclusion of seven patients, leaving the final study group of 77. All remaining patients had a minimum of four radiographs with an average of 4.6 for analysis. The average subsidence at 24 months was 2 mm and this had risen to 2.4 mm by 36 months postoperatively. When analysed using a Kaplan Meier curve using 1.5 mm as an end point we found a survivorship of 63.4% (52.3–74.5) at 24 months and this had worsened to 41.6% (26.6–56.5) by 36 months. Multivariate and univariate regression analysis of measured variables did not reveal any significant hazard for any factor other than the larger stem sizes doing worse. Conclusion: Although several cementless tapered stem designs have had an excellent track record, our migration analysis of the Accolade stem is somewhat concerning. Thirty three percent of stems had reached the 1.5 mm subsidence point by two years. This is of concern as work has previously shown this to predict failure of stems with aseptic loosening at ten years with an accuracy of 79%. If these stems go on to fail at the predicted rate this would represent an unacceptably high level of failure. Our data raises serious concerns about the overall clinical performance of this stem design due to poor initial stability and integration

Aims. Highly polished stems with force-closed design have shown satisfactory clinical results despite being related to relatively high early migration. It has been suggested that the minimal thickness of cement mantles surrounding the femoral stem should be 2 mm to 4 mm to avoid aseptic loosening. The line-to-line cementing technique of the femoral stem, designed to achieve stem press-fit, challenges this opinion. We compared the migration of a highly polished stem with force-closed design by standard and line-to-line cementing to investigate whether differences in early migration of the stems occur in a clinical study. Methods. In this single-blind, randomized controlled, clinical radiostereometric analysis (RSA) study, the migration pattern of the cemented Corail hip stem was compared between line-to-line and standard cementing in 48 arthroplasties. The primary outcome measure was femoral stem migration in terms of rotation and translation around and along with the X-, Y-, and Z- axes measured using model-based RSA at three, 12, and 24 months. A linear mixed-effects model was used for statistical analysis. Results. Results from mixed model analyses revealed a lower mean retroversion for line-to-line (0.72° (95% confidence interval (CI) 0.38° to 1.07°; p < 0.001), but no significant differences in subsidence between the techniques (-0.15 mm (95% CI -0.53 to 0.227; p = 0.429) at 24 months. Radiolucent lines measuring < 2 mm wide were found in three and five arthroplasties cemented by the standard and line-to-line method, respectively. Conclusion. The cemented Corail stem with a force-closed design seems to settle earlier and better with the line-to-line cementing method, although for subsidence the difference was not significant. However, the lower rate of migration into retroversion may reduce the wear and cement deformation, contributing to good long-term fixation and implant survival. Cite this article: Bone Joint J 2022;104-B(1):19–26

Introduction: The use of screw fixation for cementless porous-coated acetabular components for primary total hip arthroplasty (THA) remains controversial. Aim of this study was to evaluate initial acetabular implant stability and late acetabular implant migration with screw fixation of the acetabular component in order to answer the question whether screws are necessary for the fixation of the acetabular component in cementless primary THA.

Methods: In a prospective study, 102 patients (107 hips) were available for follow up after primary THA using a cementless, porous-coated acetabular component. Patients were followed up at 6 and 12 weeks, 6 and 12 months and annually thereafter to an average of 2.6 ± 1.7 years. A total of 428 standardized radiographs were analyzed by the Einzel-Bild-Röntgen-Analyse (EBRA)-digital method. Additionally, the Harris Hip Score (HHS, 0–100) was assessed at the latest follow-up.

Results: 101 (94.4 %) implants did not show significant migration of more than 1 mm of the acetabular component. Six (5.6%) implants showed a migration of more than 1 mm: in 3 cases (2.8%), migration was progressive during follow-up and led to a revision surgery due to aseptic loosening. In 3 cases, migration came to a halt and cups were claimed stable. Individuals without cup migration had an average HHS of 78.4 ± 22.9, whereas patients who showed a cup migration of > 1 mm had 53.3 ± 24.2. Statistical analysis did not reveal preoperative patterns that would identify future migration.

Discussion: and Conclusion: Our findings show that the use of screw fixation for cementless porous-coated acetabular components for primary THA does not prevent cup migration.

Aims. The Exeter short stem was designed for patients with Dorr type A femora and short-term results are promising. The aim of this study was to evaluate the minimum five-year stem migration pattern of Exeter short stems in comparison with Exeter standard stems. Methods. In this case-control study, 25 patients (22 female) at mean age of 78 years (70 to 89) received cemented Exeter short stem (case group). Cases were selected based on Dorr type A femora and matched first by Dorr type A and then age to a control cohort of 21 patients (11 female) at mean age of 74 years (70 to 89) who received with cemented Exeter standard stems (control group). Preoperatively, all patients had primary hip osteoarthritis and no osteoporosis as confirmed by dual X-ray absorptiometry scanning. Patients were followed with radiostereometry for evaluation of stem migration (primary endpoint), evaluation of cement quality, and Oxford Hip Score. Measurements were taken preoperatively, and at three, 12, and 24 months and a minimum five-year follow-up. Results. At three months, subsidence of the short stem -0.87 mm (95% confidence interval (CI) -1.07 to -0.67) was lower compared to the standard stem -1.59 mm (95% CI -1.82 to -1.36; p < 0.001). Both stems continued a similar pattern of subsidence until five-year follow-up. At five-year follow-up, the short stem had subsided mean -1.67 mm (95% CI -1.98 to -1.36) compared to mean -2.67 mm (95% CI -3.03 to -2.32) for the standard stem (p < 0.001). Subsidence was not influenced by preoperative bone quality (osteopenia vs normal) or cement mantle thickness. Conclusion. The standard Exeter stem had more early subsidence compared with the short Exeter stem in patients with Dorr type A femora, but thereafter a similar migration pattern of subsidence until minimum five years follow-up. Both the standard and the short Exeter stems subside. The standard stem subsides more compared to the short stem in Dorr type A femurs. Subsidence of the Exeter stems was not affected by cement mantle thickness. Cite this article: Bone Jt Open 2023;4(7):507–515

Aims. The objective of this study was to compare the two-year migration pattern and clinical outcomes of a total knee arthroplasty (TKA) with an asymmetrical tibial design (Persona PS) and a well-proven TKA with a symmetrical tibial design (NexGen LPS). Methods. A randomized controlled radiostereometric analysis (RSA) trial was conducted including 75 cemented posterior-stabilized TKAs. Implant migration was measured with RSA. Maximum total point motion (MTPM), translations, rotations, clinical outcomes, and patient-reported outcome measures (PROMs) were assessed at one week postoperatively and at three, six, 12, and 24 months postoperatively. Results. A linear mixed-effect model using RSA data of 31 asymmetrical and 38 symmetrical TKAs did not show a difference in mean MTPM migration pattern of the tibial or femoral components. Mean tibial component MTPM at two years postoperative of the asymmetrical TKA design was 0.93 mm and 1.00 mm for the symmetrical design. For the femoral component these values were 1.04 mm and 1.14 mm, respectively. No significant differences were observed in other migration parameters or in clinical and PROM measurements. Conclusion. The TKA design with an asymmetrical tibial component has comparable component migration with the proven TKA with a symmetrical tibial component. This suggests the risk of long-term aseptic loosening of the two designs is comparable. Cite this article: Bone Joint J 2021;103-B(5):855–863

Aims. Short, bone-conserving femoral components are increasingly used in total hip arthroplasty (THA). They are expected to allow tissue-conserving implantation and to render future revision surgery more straightforward but the long-term data on such components is limited. One such component is the global tissue-sparing (GTS) stem. Following the model for stepwise introduction of new orthopaedic implants, we evaluated early implant fixation and clinical outcome of this novel short-stem THA and compared it to that of a component with established good long-term clinical outcome. Methods. In total, 50 consecutive patients ≤ 70 years old with end-stage symptomatic osteo-arthritis were randomized to receive THA with the GTS stem or the conventional Taperloc stem using the anterior supine intermuscular approach by two experienced hip surgeons in two hospitals in the Netherlands. Primary outcome was implant migration. Patients were followed using routine clinical examination, patient reported outcome using Harris Hip Score (HHS), Hip Disability And Osteoarthritis Outcome Score (HOOS), EuroQol five-dimension questionnaire (EQ5D), and Roentgen Stereophotogrammetric Analysis (RSA) at three, six, 12, and 24 months. This study evaluated the two-year follow-up results. Results. In addition to the initial migration pattern of distal migration (subsidence, Y-translation) and retroversion (Y-rotation) also exhibited by the Taperloc stem, the GTS stem showed an initial migration pattern of varization (X-translation combined with Z-rotation) and posterior translation (Z-translation). However, all components stabilized aside from one Taperloc stem which became loose secondary to malposition and was later revised. Clinical outcomes and complications were not statistically significantly different with the numbers available. Conclusion. A substantially different and more extensive initial migration pattern was seen for the GTS stem compared to the Taperloc stem. Although implant stabilization was achieved, excellent long-term survival similar to that of the Taperloc stem should not be inferred. Especially in the absence of clinically proven relevant improvement, widespread usage should be postponed until long-term safety has been established. Cite this article: Bone Joint J 2020;102-B(6):699–708

Aims. Femoral bone preparation using compaction technique has been shown to preserve bone and improve implant fixation in animal models. No long-term clinical outcomes are available. There are no significant long-term differences between compaction and broaching techniques for primary total hip arthroplasty (THA) in terms of migration, clinical, and radiological outcomes. Methods. A total of 28 patients received one-stage bilateral primary THA with cementless femoral stems (56 hips). They were randomized to compaction on one femur and broaching on the contralateral femur. Overall, 13 patients were lost to the ten-year follow-up leaving 30 hips to be evaluated in terms of stem migration (using radiostereometry), radiological changes, Harris Hip Score, Oxford Hip Score, and complications. Results. Over a mean follow-up period of 10.6 years, the mean stem subsidence was similar between groups, with a mean of -1.20 mm (95% confidence interval (CI) -2.28 to -0.12) in the broaching group and a mean of -0.73 mm (95% CI -1.65 to 0.20) in the compaction group (p = 0.07). The long-term migration patterns of all stems were similar. The clinical and radiological outcomes were similar between groups. There were two intraoperative fractures in the compaction group that were fixed with cable wire and healed without complications. No stems were revised. Conclusion. Similar stem subsidence and radiological and clinical outcomes were identified after the use of compaction and broaching techniques of the femur at long-term follow-up. Only the compaction group had intraoperative periprosthetic femur fractures, but there were no long-term consequences of these. Cite this article: Bone Jt Open 2021;2(12):1035–1042

Aims. Stemless humeral implants have been developed to overcome stem-related complications in total shoulder arthroplasty (TSA). However, stemless implant designs may hypothetically result in less stable initial fixation, potentially affecting long-term survival. The aim of this study is to investigate early fixation and migration patterns of the stemless humeral component of the Simpliciti Shoulder System and to evaluate clinical outcomes. Methods. In this prospective cohort study, radiostereometric analysis (RSA) radiographs were obtained in 24 patients at one day, six weeks, six months, one year, and two years postoperatively. Migration was calculated using model-based RSA. Clinical outcomes were evaluated using the visual analogue scale (VAS), the Oxford Shoulder Score (OSS), the Constant-Murley Score (CMS), and the Disabilities of the Arm, Shoulder and Hand (DASH) score. Results. At two years, median translation along the x-, y-, and z-axis was -0.12 mm (interquartile range (IQR) -0.18 to 0.02), -0.17 mm (IQR -0.27 to -0.09), and 0.09 mm (IQR 0.02 to 0.31). Median rotation around the x-, y-, and z-axis was 0.12° (IQR -0.50 to 0.57), -0.98° (IQR -1.83 to 1.23), and 0.09° (IQR -0.76 to 0.30). Overall, 20 prostheses stabilized within 12 months postoperatively. Four prostheses showed continuous migration between 12 and 24 months. At two-year follow-up, with the exception of one revised prosthesis, all clinical scores improved significantly (median VAS difference at rest: -3.0 (IQR -1.5 to -6.0); OSS 22.0 (IQR 15.0 to 25.0); CMS 29.5 (IQR 15.0 to 35.75); and DASH -30.0 (IQR -20.6 to -41.67) (all p < 0.001)) with the exception of one revised prosthesis. Conclusion. In conclusion, we found that 20 out of 24 implants stabilized within 12 months postoperatively. The significance of continuous migration in four implants is unclear and future research on the predictive value of early migration for future loosening in TSA is required. Clinical results revealed a clinically relevant improvement. Cite this article: Bone Joint J 2022;104-B(1):76–82

Aims. Medial pivot (MP) total knee arthroplasties (TKAs) were designed to mimic native knee kinematics with their deep medial congruent fitting of the tibia to the femur almost like a ball-on-socket, and a flat lateral part. GMK Sphere is a novel MP implant. Our primary aim was to study the migration pattern of the tibial tray of this TKA. Methods. A total of 31 patients were recruited to this single-group radiostereometric analysis (RSA) study and received a medial pivot GMK Sphere TKA. The distributions of male patients versus female patients and right versus left knees were 21:10 and 17:14, respectively. Mean BMI was 29 kg/m. 2. (95% confidence interval (CI) 27 to 30) and mean age at surgery was 63 years (95% CI 61 to 66). Maximum total point motions (MTPMs), medial, proximal, and anterior translations and transversal, internal, and varus rotations were calculated at three, 12, and 24 months. Patient-reported outcome measure data were also retrieved. Results. MTPMs at three, 12, and 24 months were 1.0 mm (95% CI 0.8 to 1.2), 1.3 mm (95% CI 0.9 to 1.7), and 1.4 mm (0.8 to 2.0), respectively. The Forgotten Joint Score was 79 (95% CI 39 to 95) and Knee Injury and Osteoarthritis Outcome Score obtained at two years was 94 (95% CI 81 to 100), 86 (95% CI 75 to 93), 94 (95% CI 88 to 100), 69 (95% CI 48 to 88), and 81 (95% CI59 to 100) for Pain, Symptoms, Activities of Daily Living, Sport & Recreation, and Quality of Life, respectively. Conclusion. In conclusion, we found that the mean increase in MTPM was lower than 0.2 mm between 12 and 24 months and thus apparently stable. Yet the GMK Sphere had higher migration at one and two years than anticipated. Based on current RSA data, we therefore cannot conclude on the long-term performance of the implant, pending further assessment. Cite this article: Bone Jt Open 2021;2(9):737–744

Cementless stem designs in total hip arthroplasty differ in relation to geometry and area of fixation. We utilised radiostereometric analysis (RSA) to evaluate the 2-year migration of a novel, short, proximally coated femoral stem. 30 participants undergoing primary total hip replacement for any cause (rheumatoid or inflammatory arthritis, osteoarthritis) were prospectively recruited in this study. Osteoporotic patients and cases of suspected infection were excluded. All patients received a short blade stem, proximally coated with a reduced lateral shoulder and narrow triple taper geometry to minimise bone removal. RSA radiographs were performed post-operatively and at 6 weeks, 6 months, 1- and 2 years. The Harris Hip Score (HHS), Oxford Hip Score (OHS) and EQ-5D were collected at baseline and at 2 years post-operatively. The stability of implants and complications were captured during each follow-up visit. A total of 14 female and 16 male patients were recruited with a mean age of 64.8 (range 47 to 75). At two years the mean subsidence of the stem was 0.34 mm (SD 0.62) and the total migration 0.74 mm (SD 0.60). The mean medial translation at two years was 0.059 (0.24) and the mean anterior translation 0.12 (0.59) respectively. Baseline PROM scores improved significantly at 2-years from pre-operatively (median and interquartile range): HHS from 33 (18.25) to 92 (19), EQ5D from 0.5 (0.35) to 0.94 (0.17), OHS from 21 (18.25) to 42 (4.25). P-value for all comparisons was <0.001. 2-year follow up data revealed no complications. There were no stem revisions in study participants and no heterotopic ossifications were identified on radiographs. 2-year migration results of a cementless, short blade, proximally coated tapered femoral stem using RSA, showed the stem exhibits a predictable migration pattern and achieves initial stability. This is highly likely to translate to mid and long-term stability, which needs to be corroborated by long-term outcome studies. Furthermore, participants demonstrated excellent clinical, patient reported and radiological outcomes after 2 years of follow up to support expansion in the use of this prosthesis

Aims. Radiostereometric analysis (RSA) studies of vitamin E-doped, highly crosslinked polyethylene (VEPE) liners show low head penetration rates in cementless acetabular components. There is, however, currently no data on cemented VEPE acetabular components in total hip arthroplasty (THA). The aim of this study was to evaluate the safety of a new cemented VEPE component, compared with a conventional polyethylene (PE) component regarding migration, head penetration, and clinical results. Patients and Methods. We enrolled 42 patients (21 male, 21 female) with osteoarthritis and a mean age of 67 years (. sd. 5), in a double-blinded, noninferiority, randomized controlled trial. The subjects were randomized in a 1:1 ratio to receive a reverse hybrid THA with a cemented component of either argon-gas gamma-sterilized PE component (controls) or VEPE, with identical geometry. The primary endpoint was proximal implant migration of the component at two years postoperatively measured with RSA. Secondary endpoints included total migration of the component, penetration of the femoral head into the component, and patient-reported outcome measurements. Results. In total, 19 control implants and 18 implants in the VEPE group were analyzed for the primary endpoint. We found a continuous proximal migration of the component in the VEPE group that was significantly higher with a difference at two years of a mean 0.21 mm (95% confidence interval (CI) 0.05 to 0.37; p = 0.013). The total migration was also significantly higher in the VEPE group, but femoral head penetration was lower. We found no difference in clinical outcomes between the groups. Conclusion. At two years, this cemented VEPE component, although having a low head penetration and excellent clinical results, failed to meet noninferiority compared with the conventional implant by a proximal migration above the proposed safety threshold of RSA. The early proximal migration pattern of the VEPE component is a reason for continued monitoring, although a specific threshold for proximal migration and risk for later failure cannot be defined and needs further study. Cite this article: Bone Joint J 2019;101-B:1192–1198

Aims. The optimal method of tibial component fixation remains uncertain in total knee arthroplasty (TKA). Hydroxyapatite coatings have been applied to improve bone ingrowth in uncemented designs, but may only coat the directly accessible surface. As peri-apatite (PA) is solution deposited, this may increase the coverage of the implant surface and thereby fixation. We assessed the tibial component fixation of uncemented PA-coated TKAs versus cemented TKAs. Patients and Methods. Patients were randomised to PA-coated or cemented TKAs. In 60 patients (30 in each group), radiostereometric analysis of tibial component migration was evaluated as the primary outcome at baseline, three months post-operatively and at one, two and five years. A linear mixed-effects model was used to analyse the repeated measurements. Results. After five years of follow-up, one (cemented) component was revised due to ligament instability. Overall, uncemented PA-coated tibial components migrated significantly more (p = 0.003), with the mean maximum total point motion (MTPM) at five years being 0.62 mm (95% confidence intervals (CI) 0.49 to 0.76) for cemented tibial components and 0.97 mm (95% CI 0.81 to 1.15) for PA-coated tibial components in TKA. However, between three months and five years the cemented TKAs migrated significantly more (p = 0.02), displaying a MTPM of 0.27 mm (95% CI, 0.19 to 0.36) versus 0.13 mm (95% CI, 0.01 to 0.25) for PA-coated tibial components. One implant in each group was considered at risk for aseptic loosening due to continuous migration after five years of follow-up, albeit with different migration patterns for each group (i.e. higher initial migration but diminishing over time for the PA-coated component versus gradually increasing migration for the cemented component). Conclusion. The tibial components of PA-coated TKAs showed more overall migration compared with the tibial components of cemented TKAs. However, post hoc analysis showed that this difference was caused by higher migration of PA-coated components in the first three months, after which a stable migration pattern was observed. Clinically, there was no significant difference in outcome between the groups. Cite this article: Bone Joint J 2017;99-B:1467–76

Purpose: The purpose of this prospective blinded randomized control trial was to compare the stem migration of two cemented stem designs using radiostereometric analysis (RSA). This was essentially a safety study in which our hypothesis was that the newer design (CPCS, Smith and Nephew Inc) would demonstrate similar micro-motion to the well-established Exeter (Stryker) design. Method: Thirty patients were consented and enrolled into a blinded RCT in which 15 patients received a dedicated RSA CPCS stem and 15 patients received a RSA Exeter stem. Both stems are collarless tapered polished cemented stems, the only difference being a slight lateral to medial taper with the CPCS design. Outcome measures were compared (Hip Society Score, WOMAC, SF-12). RSA analysis was conducted immediately postoperatively, at 6 weeks, 3 months, 6 months, 1 year and 2 years. Results: No difference was found in any of the outcome measures pre-operatively or postoperatively. At 2 years, stem subsidence for the CPCS stem was approximately half that seen for the Exeter stem (0.565±0.189mm and 0.981±0.209mm respectively, p< 0.0001). In contrast, posterior (internal) rotation of the CPCS was approximately twice that of the Exeter stem (1.496±1.215° and 0.716±0.818° respectively, p=0.221). Other migration patterns were no different between stems. Conclusion: As expected with this stem design, both stems showed some axial and rotational migration within the cement mantle. The subtle differences in design may explain the differences in migration patterns. Our data suggests that the newer CPCS design should perform well over the long-term

Purpose: Porous metal technology may have significant impacts on implant fixation and long-term survival due to their high co-efficient of friction and similarity to trabecular bone in morphology and mechanical behaviour. While promising, the in vivo mechanical behaviour and micromotion at the interface has not previously been reported on. We report on the 2-year results of an RCT using radiosterometric analysis (RSA) to asses a porous metal (PM) monoblock tibial component. Method: Patients undergoing TKA were randomized to receive a either the PM (n=34) or the cemented tibial component (n=33). A standardized protocol was used for intra and post-operative factors. RSA exams were obtained postoperatively within 4 days of surgery and at 6, 12 and 24 months. One patient was excluded due to an intraoperative complication, and four others were lost to follow-up due to poor bead visibility or morbidity. Standard subjective outcome measures were applied. Results: There were no revisions in either group. The PM group exhibited two distinct migration patterns. One group stabilized immediately with similar migration to the cemented cases (0.38 vs. 0.46 p=0.4). A subset of 6 PM cases demonstrated significantly higher initial migration (mean=2.01mm, p< 0.01) but appeared stable at 2 years. In addition, 3 of the 6 high migration cases manifested independent bead subsidence. This was determined to be due to PM plate deformation. Two cemented cases were considered at risk for early failure due to aseptic loosening because of RSA migration pattern. There were no differences between groups in the subjective health outcome measures. Conclusion: A subset of PM components demonstrated high early migration followed by stabilization. It appears that some of these PM components deformed under load, most often in the posteromedial corner, perhaps as a result of malalignment or ligament imbalance. The implications of this finding are yet to be determined

This was a safety study where the hypothesis was that the newer-design CPCS femoral stem would demonstrate similar early clinical results and micromovement to the well-established Exeter stem. Both are collarless, tapered, polished cemented stems, the only difference being a slight lateral to medial taper with the CPCS stem. A total of 34 patients were enrolled in a single-blinded randomised controlled trial in which 17 patients received a dedicated radiostereometric CPCS stem and 17 a radiostereometric Exeter stem. No difference was found in any of the outcome measures pre-operatively or post-operatively between groups. At two years, the mean subsidence for the CPCS stem was nearly half that seen for the Exeter stem (0.77 mm (−0.943 to 1.77) and 1.25 mm (0.719 to 1.625), respectively; p = 0.032). In contrast, the mean internal rotation of the CPCS stem was approximately twice that of the Exeter (1.61° (−1.07° to 4.33°) and 0.59° (0.97° to 1.64°), respectively; p = 0.048). Other migration patterns were not significantly different between the stems. The subtle differences in designs may explain the different patterns of migration. Comparable migration with the Exeter stem suggests that the CPCS design will perform well in the long term