Aims. For many designs of total knee arthroplasty (TKA) it remains unclear whether cemented or uncemented fixation provides optimal long-term survival. The main limitation in most studies is a retrospective or non-comparative study design. The same is true for comparative trials looking only at the survival rate as extensive sample sizes are needed to detect true differences in fixation and durability. Studies using radiostereometric analysis (RSA) techniques have shown to be highly predictive in detecting late occurring aseptic loosening at an early stage. To investigate the difference in predicted long-term survival between cemented, uncemented, and hybrid fixation of TKA, we performed a randomized controlled trial using RSA. Methods. A total of 105 patients were randomized into three groups (cemented, uncemented, and hybrid fixation of the ACS Mobile Bearing (ACS MB) knee system, implantcast). RSA examinations were performed on the first day after surgery and at scheduled follow-up visits at three months, six months, one year, and two years postoperatively. Patient-reported outcome measures (PROMs) were obtained preoperatively and after two years follow-up. Patients and follow-up investigators were blinded for the result of randomization. Results. RSA secondary stabilization did not show a significant difference between the three types of fixation. A maximum total point motion of less than 0.2 mm in the second postoperative year was shown in each group, which suggests stabilization of the implant. At 24 months after surgery, PROMs significantly improved compared to baseline in all treatment groups. No significant difference was observed between the three groups. Conclusion. Secondary stabilization measurements in this study demonstrated no significant difference between the groups. In all groups migration stabilized after initial settling of the implant. For this implant the long-term outcome is not expected to be influenced by the type of fixation to the bone. Cite this article: Bone Joint J 2021;103-B(1):98–104

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. Radiostereometric analysis (RSA) is considered the gold standard for in vivo migration analysis, but CT-based alternatives show comparable results in the shoulder and hip. We have previously validated a CT-based migration analysis method (CTMA) in a knee phantom compared to RSA. In this study, we validated the method in patients undergoing total knee arthroplasty (TKA). Our primary outcome measure was the difference in maximum total point motion (MTPM) between the differing methods. Methods. A total of 31 patients were prospectively studied having undergone an uncemented medial pivot knee TKA. Migrations were measured up to 12 months with marker-based and model-based RSA, and CT-RSA. Results. Mean precision data for MTPM were 0.27 mm (SD 0.09) for marker-based RSA, 0.37 mm (SD 0.26) for model-based RSA, and 0.25 mm (SD 0.11) for CTMA. CTMA was as precise as both RSA methods (p = 0.845 and p = 0.156). At three months, MTPM showed a mean of 0.66 mm (95% CI 0.52 to 0.81) for marker-based RSA, 0.79 (95% CI 0.64 to 0.94) for model-based RSA, and 0.59 (95% CI 0.47 to 0.72) for CTMA. There was no difference between CTMA and marker-based RSA (p = 0.400), but CTMA showed lower migration than model-based RSA (p = 0.019). At 12 months, MTPM was 1.03 (95% CI 0.79 to 1.26) for marker-based RSA, 1.02 (95% CI 0.79 to 1.25) for model-based RSA, and 0.71 (95% CI 0.48 to 0.94) for CTMA. MTPM for CTMA was lower than both RSA methods (p < 0.001). Differences between migration increased between the methods from three to 12 months. Mean effective radiation doses per examination were 0.016 mSv (RSA) and 0.069 mSv (CT). Imaging time for performing RSA radiographs was 17 minutes 26 seconds (SD 7 mins 9 sec) and 4 minutes 24 seconds (SD 2 mins 3 sec) for CT. Conclusion. No difference in precision was found between CTMA and marker- or model-based RSA, but CTMA shows lower migration values of the tibial component at 12 months. CTMA can be used with low effective radiation doses, and CT image acquisition is faster to perform than RSA methods and may be suitable for use in ordinary clinical settings. Cite this article: Bone Joint J 2025;107-B(2):173–180

Aims. Reverse shoulder arthroplasty (RSA) has become the most common type of shoulder arthroplasty used in the UK, and a better understanding of the outcomes after revision of a failed RSA is needed. The aim of this study was to review the current evidence systematically to determine patient-reported outcome measures and the rates of re-revision and complications for patients undergoing revision of a RSA. Methods. MEDLINE, Embase, CENTRAL, and the Cochrane Database of Systematic Reviews were searched. Studies involving adult patients who underwent revision of a primary RSA for any indication were included. Those who underwent a RSA for failure of a total shoulder arthroplasty or hemiarthroplasty were excluded. Pre- and postoperative shoulder scores were evaluated in a random effects meta-analysis to determine the mean difference. The rates of re-revision and complications were also calculated. Results. The initial search elicited 3,166 results and, following removal of duplicates and screening, 13 studies with a total of 1,042 RSAs were identified. An increase in shoulder scores pre- to postoperatively was reported in all the studies. Following revision of a RSA to a further RSA, there was a significant increase in the American Shoulder and Elbow Surgeons Score (mean difference 20.78 (95% CI 8.16 to 33.40); p = 0.001). A re-revision rate at final follow-up ranging from 9% to 32%, a one-year re-revision rate of 14%, and a five-year re-revision rate of 23% were reported. The complication rate in all the studies was between 18.5% and 36%, with a total incidence of 29%. Conclusion. This is the largest systematic review of the outcomes following revision of a RSA. We found an improvement in functional outcomes after revision surgery, but the rates of re-revision and complications are high and warrant consideration when planning a revision procedure. Cite this article: Bone Joint J 2024;106-B(11):1293–1300

Aims. Optimal glenoid positioning in reverse shoulder arthroplasty (RSA) is crucial to provide impingement-free range of motion (ROM). Lateralization and inclination correction are not yet systematically used. Using planning software, we simulated the most used glenoid implant positions. The primary goal was to determine the configuration that delivers the best theoretical impingement-free ROM. Methods. With the use of a 3D planning software (Blueprint) for RSA, 41 shoulders in 41 consecutive patients (17 males and 24 females; means age 73 years (SD 7)) undergoing RSA were planned. For the same anteroposterior positioning and retroversion of the glenoid implant, four different glenoid baseplate configurations were used on each shoulder to compare ROM: 1) no correction of the RSA angle and no lateralization (C-L-); 2) correction of the RSA angle with medialization by inferior reaming (C+M+); 3) correction of the RSA angle without lateralization by superior compensation (C+L-); and 4) correction of the RSA angle and additional lateralization (C+L+). The same humeral inlay implant and positioning were used on the humeral side for the four different glenoid configurations with a 3 mm symmetric 135° inclined polyethylene liner. Results. The configuration with lateralization and correction of the RSA angle (C+L+) led to better ROM in flexion, extension, adduction, and external rotation (p ≤ 0.001). Only internal rotation was not significantly different between groups (p = 0.388). The configuration where correction of the inclination was done by medialization (C+M+) led to the worst ROM in adduction, extension, abduction, flexion, and external rotation of the shoulder. Conclusion. Our software study shows that, when using a 135° inlay reversed humeral implant, correcting glenoid inclination (RSA angle 0°) and lateralizing the glenoid component by using an angled bony or metallic augment of 8 to 10 mm provides optimal impingement-free ROM. Cite this article: Bone Jt Open 2024;5(10):851–857

Aims. Conflicting clinical results are reported for the ATTUNE Total Knee Arthroplasty (TKA). This randomized controlled trial (RCT) evaluated five-year follow-up results comparing cemented ATTUNE and PFC-Sigma cruciate retaining TKAs, analyzing component migration as measured by radiostereometric analysis (RSA), clinical outcomes, patient-reported outcome measures (PROMs), and radiological outcomes. Methods. A total of 74 primary TKAs were included in this single-blind RCT. RSA examinations were performed, and PROMs and clinical outcomes were collected immediate postoperatively, and at three, six, 12, 24, and 60 months’ follow-up. Radiolucent lines (RLLs) were measured in standard anteroposterior radiographs at six weeks, and 12 and 60 months postoperatively. Results. At five-year follow-up, RSA data from 61 patients were available and the mean maximum total point motion (MTPM) of the femoral components were: ATTUNE: 0.96 mm (95% confidence interval (CI) 0.79 to 1.14) and PFC-Sigma 1.37 mm (95% CI 1.18 to 1.59) (p < 0.001). The PFC-Sigma femoral component migrated more in the first postoperative year, but stabilized thereafter. MPTM of the tibial components were comparable at five-year follow-up: ATTUNE 1.12 mm (95% CI 0.95 to 1.31) and PFC-Sigma 1.25 mm (95% CI 1.07 to 1.44) (p = 0.438). RLL at the medial tibial implant-cement interface remained more prevalent for the ATTUNE at five-year follow-up compared to the PFC-Sigma (20% vs 3%). RLL did not progress over time, and varied between patients at different timepoints for both TKA systems. Clinical outcomes and PROMs improved compared with preoperative scores, and were not different between groups. Conclusion. MTPM migration at five-year follow-up of the femoral and tibial component of the ATTUNE were similar and as low as that of the PFC-Sigma. MTPM migration of both knee implants did not significantly change from one year post-surgery, indicating stable fixation. Long-term ATTUNE performance may be expected to be comparable to the clinically well-performing PFC-Sigma. We have not found evidence of increased tibial component migration as measured by RSA to support concerns about cement debonding and a higher risk of aseptic loosening with the ATTUNE TKA. Cite this article: Bone Joint J 2023;105-B(11):1168–1176

Aims. The aim of this study was to report long-term clinical outcomes of a modern convertible metal-backed glenoid (MBG) in total shoulder arthroplasty (TSA). Methods. After a minimum of 15 years, a previously studied cohort of 35 patients who received a modern convertible MBG during the period 1996 to 2005 was contacted for clinical and radiological follow-up. At last follow-up, patients were evaluated radiologically and clinically according to the Constant Score, Simple Shoulder Test, and visual analogue scale for pain. Complications and revisions were recorded, and survival analysis was performed. Results. At the last follow-up, 20 patients were contacted. Of these, 15 patients had experienced at least one complication, and ten underwent revision surgery. The mean time to revision was 13.8 years (7 to 20). Cuff failure was the most common complication. Conversion to reverse shoulder arthroplasty, while maintaining the baseplate, was possible in five cases, with good results. In patients in whom the baseplate was removed, revision was performed significantly later (18.4 vs 11.1 years; p = 0.016). The general revision-free survival was 73% (95% CI 49.5 to 87.3) at 15 years and 38% (95% CI 11.8% to 64.3%) at 20 years, while MBG revision-free survival was 96.0% (95% CI 74.8% to 99.4%) at 15 years and 54% (95% CI 16.2% to 80.8%) at 20 years. Clinical scores showed a negative trend over time, although not statistically significant. Radiologically, polyethylene wear was observed in all cases and was complete in 12 out of 19 cases, and five glenoids were ‘at risk’ for loosening. Conclusion. At long-term follow-up, convertible MBG-TSA revealed a high rate of complications and revision surgery, mainly due to soft-tissue failure and polyethylene wear occurring with time. Prompt conversion to RSA maintaining the baseplate provided good results and a low complication rate. Radiological follow-up at about ten years is strictly recommended and, if metal-to-metal contact is observed, conversion to RSA is advisable. These results emphasize the need for continued research into improving TSA outcomes, especially in cases of MBG usage. Cite this article: Bone Jt Open 2025;6(1):82–92

Aims. This study aimed to assess the impact of using the metal-augmented glenoid baseplate (AGB) on improving clinical and radiological outcomes, as well as reducing complications, in patients with superior glenoid wear undergoing reverse shoulder arthroplasty (RSA). Methods. From January 2016 to June 2021, out of 235 patients who underwent primary RSA, 24 received a superior-AGB after off-axis reaming (Group A). Subsequently, we conducted propensity score matching in a 1:3 ratio, considering sex, age, follow-up duration, and glenoid wear (superior-inclination and retroversion), and selected 72 well-balanced matched patients who received a standard glenoid baseplate (STB) after eccentric reaming (Group B). Superior-inclination, retroversion, and lateral humeral offset (LHO) were measured to assess preoperative glenoid wear and postoperative correction, as well as to identify any complications. Clinical outcomes were measured at each outpatient visit before and after surgery. Results. There were no significant differences in demographic data and preoperative characteristics between the two groups. Both groups showed significant improvements in patient-reported outcome measures (visual analogue scale for pain, visual analogue scale for function, American Shoulder and Elbow Surgeons, Constant, and Simple Shoulder Test scores) from preoperative to final assessment (p < 0.001). However, AGB showed no additional benefit. Notably, within range of motion, Group B showed significant postoperative decrease in both external rotation and internal rotation, unlike Group A (p = 0.028 and 0.003, respectively). Both groups demonstrated a significant correction of superior-inclination after surgery, while patients in Group B exhibited a significant decrease in LHO postoperatively (p = 0.001). Regarding complications, Group A experienced more acromial stress fractures (3 cases; 12.5%), whereas Group B had a higher occurrence of scapular notching (24 cases; 33.3%) (p = 0.008). Conclusion. Both eccentric reaming with STB and off-axis reaming with AGB are effective methods for addressing superior glenoid wear in RSA, leading to improved clinical outcomes. However, it is important to be aware of the potential risks associated with eccentric reaming, which include excessive bone loss leading to reduced rotation and scapular notching. Cite this article: Bone Joint J 2024;106-B(3):268–276

Aims. The aim of this study was to compare the clinical and radiological outcomes of reverse shoulder arthroplasty (RSA) using small and standard baseplates in Asian patients, and to investigate the impact of a mismatch in the sizes of the glenoid and the baseplate on the outcomes. Methods. This was retrospective analysis of 50 and 33 RSAs using a standard (33.8 mm, ST group) and a small (29.5 mm, SM group) baseplate of the Equinoxe reverse shoulder system, which were undertaken between January 2017 and March 2021. Radiological evaluations included the size of the glenoid, the β-angle, the inclination of the glenoid component, inferior overhang, scapular notching, the location of the central cage in the baseplate within the vault and the mismatch in size between the glenoid and baseplate. Clinical evaluations included the range of motion (ROM) and functional scores. In subgroup analysis, comparisons were performed between those in whom the vault of the glenoid was perforated (VP group) and those in whom it was not perforated (VNP group). Results. Perforation of the vault of the glenoid (p = 0.018) and size mismatch in height (p < 0.001) and width (p = 0.013) were significantly more frequent in the ST group than in the SM group. There was no significant difference in the clinical scores and ROM in the two groups, two years postoperatively (all p > 0.05). In subgroup analysis, the VP group had significantly less inferior overhang (p = 0.009), more scapular notching (p = 0.018), and more size mismatch in height (p < 0.001) and width (p = 0.025) than the VNP group. Conclusion. In Asian patients with a small glenoid, using a 29.5 mm small baseplate at the time of RSA was more effective in reducing size mismatch between the glenoid and the baseplate, decreasing the incidence of perforation of the glenoid vault, and achieving optimal positioning of the baseplate compared with the use of a 33.8 mm standard baseplate. However, longer follow-up is required to assess the impact of these findings on the clinical outcomes. Cite this article: Bone Joint J 2023;105-B(11):1189–1195

Aims. The aim of this study was to compare a bicruciate-retaining (BCR) total knee arthroplasty (TKA) with a posterior cruciate-retaining (CR) TKA design in terms of kinematics, measured using fluoroscopy and stability as micromotion using radiostereometric analysis (RSA). Methods. A total of 40 patients with end-stage osteoarthritis were included in this randomized controlled trial. All patients performed a step-up and lunge task in front of a monoplane fluoroscope one year postoperatively. Femorotibial contact point (CP) locations were determined at every flexion angle and compared between the groups. RSA images were taken at baseline, six weeks, three, six, 12, and 24 months postoperatively. Clinical and functional outcomes were compared postoperatively for two years. Results. The BCR-TKA demonstrated a kinematic pattern comparable to the natural knee’s screw-home mechanism in the step-up task. In the lunge task, the medial CP of the BCR-TKA was more anterior in the early flexion phase, while laterally the CP was more posterior during the entire movement cycle. The BCR-TKA group showed higher tibial migration. No differences were found for the clinical and functional outcomes. Conclusion. The BCR-TKA shows a different kinematic pattern in early flexion/late extension compared to the CR-TKA. The difference between both implants is mostly visible in the flexion phase in which the anterior cruciate ligament is effective; however, both designs fail to fully replicate the motion of a natural knee. The higher migration of the BCR-TKA was concerning and highlights the importance of longer follow-up. Cite this article: Bone Joint J 2023;105-B(1):35–46

Aims. Favourable short-term outcomes have been reported following latissimus dorsi tendon transfer for patients with an irreparable subscapularis (SSC) tendon tear. The aim of this study was to investigate the long-term outcomes of this transfer in these patients. Methods. This was a retrospective study involving 30 patients with an irreparable SSC tear and those with a SSC tear combined with a reparable supraspinatus tear, who underwent a latissimus dorsi tendon transfer. Clinical scores and active range of motion (aROM), SSC-specific physical examination and the rate of return to work were assessed. Radiological assessment included recording the acromiohumeral distance (AHD), the Hamada grade of cuff tear arthropathy and the integrity of the transferred tendon. Statistical analysis compared preoperative, short-term (two years), and final follow-up at a mean of 8.7 years (7 to 10). Results. There were significant improvements in clinical scores, in the range and strength of internal rotation and aROM compared with the preoperative values in the 26 patients (87%) who were available for long-term follow-up. These improvements were maintained between short- and long-term follow-ups. Although there was a decreased mean AHD of 7.3 mm (SD 1.5) and an increased mean Hamada grade of 1.7 (SD 0.5) at final follow-up, the rate of progression of cuff tear arthropathy remained low-grade. Comparison between the isolated SSC and combined SSC and reparable supraspinatus tear groups showed no significant differences. At final follow-up, one patient (3.8%) had undergone revision surgery to a reverse shoulder arthroplasty (RSA). No neurological complications were associated with the procedure. Conclusion. Latissimus dorsi transfer for an irreparable SSC tendon tear resulted in a significant clinical improvement, particularly in pain, range and strength of internal rotation and aROM, which were maintained over a mean of 8.7 years following surgery. Given that this was a long-term outcome study, there was a low-grade progression in the rate of cuff tear arthropathy. Thus, the long-term clinical efficacy of latissimus dorsi tendon transfer in patients with irreparable SSC was confirmed as a joint-preserving procedure for these patients, suggesting it as an effective alternative to RSA in young, active patients without degenerative changes of the glenohumeral joint. Cite this article: Bone Joint J 2024;106-B(9):957–963

Aims. Both the femoral and tibial component are usually cemented at revision total knee arthroplasty (rTKA), while stems can be added with either cemented or press-fit (hybrid) fixation. The aim of this study was to compare the long-term stability of rTKA with cemented and press-fitted stems, using radiostereometric analysis (RSA). Methods. This is a follow-up of a randomized controlled trial, initially involving 32 patients, of whom 19 (nine cemented, ten hybrid) were available for follow-up ten years postoperatively, when further RSA measurements were made. Micromotion of the femoral and tibial components was assessed using model-based RSA software (RSAcore). The clinical outcome was evaluated using the Knee Society Score (KSS), the Knee injury and Osteoarthritis Outcome Score (KOOS), and visual analogue scale (pain and satisfaction). Results. The median total femoral translation and rotation at ten years were 0.39 mm (interquartile range (IQR) 0.20 to 0.54) and 0.59° (IQR 0.46° to 0.73°) for the cemented group and 0.70 mm (IQR 0.15 to 0.77) and 0.78° (IQR 0.47° to 1.43°) for the hybrid group. For the tibial components this was 0.38 mm (IQR 0.33 to 0.85) and 0.98° (IQR 0.38° to 1.34°) for the cemented group and 0.42 mm (IQR 0.30 to 0.52) and 0.72° (IQR 0.62° to 0.82°) for the hybrid group. None of these values were significantly different between the two groups and there were no significant differences between the clinical scores in the two groups at this time. There was only one re-revision, in the hybrid group, for infection and not for aseptic loosening. Conclusion. These results show good long-term fixation with no difference in micromotion and clinical outcome between fully cemented and hybrid fixation in rTKA, which builds on earlier short- to mid-term results. The patients all had type I or II osseous defects, which may in part explain the good results. Cite this article: Bone Joint J 2022;104-B(7):875–883

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

Objectives. The accuracy and precision of two new methods of model-based radiostereometric analysis (RSA) were hypothesised to be superior to a plain radiograph method in the assessment of polyethylene (PE) wear. Methods. A phantom device was constructed to simulate three-dimensional (3D) PE wear. Images were obtained consecutively for each simulated wear position for each modality. Three commercially available packages were evaluated: model-based RSA using laser-scanned cup models (MB-RSA), model-based RSA using computer-generated elementary geometrical shape models (EGS-RSA), and PolyWare. Precision (95% repeatability limits) and accuracy (Root Mean Square Errors) for two-dimensional (2D) and 3D wear measurements were assessed. Results. The precision for 2D wear measures was 0.078 mm, 0.102 mm, and 0.076 mm for EGS-RSA, MB-RSA, and PolyWare, respectively. For the 3D wear measures the precision was 0.185 mm, 0.189 mm, and 0.244 mm for EGS-RSA, MB-RSA, and PolyWare respectively. Repeatability was similar for all methods within the same dimension, when compared between 2D and 3D (all p > 0.28). For the 2D RSA methods, accuracy was below 0.055 mm and at least 0.335 mm for PolyWare. For 3D measurements, accuracy was 0.1 mm, 0.2 mm, and 0.3 mm for EGS-RSA, MB-RSA and PolyWare respectively. PolyWare was less accurate compared with RSA methods (p = 0.036). No difference was observed between the RSA methods (p = 0.10). Conclusions. For all methods, precision and accuracy were better in 2D, with RSA methods being superior in accuracy. Although less accurate and precise, 3D RSA defines the clinically relevant wear pattern (multidirectional). PolyWare is a good and low-cost alternative to RSA, despite being less accurate and requiring a larger sample size

We studied the knees of 11 volunteers using RSA during a step-up exercise requiring extension while weight-bearing from 50° to 0°. The findings on weight-bearing flexion with and without external rotation of the tibia based on MRI were confirmed

Aims

The aim of this study was to compare the migration of the femoral component, five years postoperatively, between patients with a highly cross-linked polyethylene (HXLPE) insert and those with a conventional polyethylene (PE) insert in an uncemented Triathlon fixed insert cruciate-retaining total knee arthroplasty (TKA). Secondary aims included clinical outcomes and patient-reported outcome measures (PROMs). We have previously reported the migration and outcome of the tibial components in these patients.

The Exeter femoral stem is a double-tapered highly polished collarless cemented implant with good long-term clinical results. In order to determine why the stem functions well we have undertaken a long-term radiostereometric analysis (RSA) study. A total of 20 patients undergoing primary Exeter total hip replacement for osteoarthritis using the Hardinge approach were recruited and followed with RSA for ten years. The stems progressively subsided and internally rotated with posterior head migration. The mean subsidence was 0.7 mm (95% confidence interval (CI) 0.5 to 0.9) at two years and 1.3 mm (95% CI 1.0 to 1.6) at ten years. The mean posterior migration of the head was 0.7 mm (95% CI 0.5 to 0.9) at two years and 1.2 mm (95% CI 1.0 to 1.4) at ten years. There was no significant cement restrictor migration. The Exeter stem continues to subside slowly into the cement mantle in the long term. This appears to compress the cement and the cement bone interface, contributing to secure fixation in the long term. Cite this article: Bone Joint J 2013;95-B:605–8