A high radiographic inclination angle (RI) contributes to accelerated wear and has been associated with dislocation after total hip arthroplasty (THA). With freehand positioning of the acetabular component there is a lack of accuracy, with a trend towards a high radiographic inclination angle. The aim of this study was to investigate whether the use of a digital protractor to measure the operative inclination angle (OI) could improve the positioning of the acetabular component in relation to a ‘safe zone’. . We measured the radiographic inclination angles of 200 consecutive uncemented primary THAs. In the first 100 the component was introduced freehand and in the second 100 a digital protractor was used to measure the operative inclination angle. . The mean difference between the operative and the radiographic inclination angles (∆RI–OI) in the second cohort was 12.3° (3.8° to 19.8°). There was a strong correlation between the circumference of the hip and ∆RI–OI. The number of RI outliers was significantly reduced in the protractor group (p = 0.002). Adjusting the OI, using a digital protractor and taking into account the circumference of the patient’s hip, improves the RI significantly (p < 0.001) and does not require additional operating time. Cite this article: Bone Joint J 2015; 97-B:603–610

Aims. Existing literature indicates that inferiorly inclined glenoid baseplates following reverse total shoulder arthroplasty (RSA) produce better outcomes compared to superiorly inclined baseplates. We aim to compare clinical outcomes for RSAs with superiorly and neutrally/inferiorly inclined lateralized glenospheres. Methods. We retrospectively reviewed 154 consecutive patients undergoing RSA between July 2015 and July 2017 by one single-fellowship trained surgeon (AJ). Two raters (KAM and MVS) independently measured glenoid inclination in preoperative and minimum two year follow-up radiographs (anteroposterior/Grashey) using the RSA angle. Inclination was then compared to patient-reported outcomes, range of motion (ROM), and independently assessed degree of scapular notching and staging of heterotopic ossification at two year follow-up. Results. Median postoperative inclination for each group was found to be -3.6° (interquartile range (IQR) -2.1 to -6.9) and 6.0° (3.2° to 10.1°) for the neutrally/inferiorly and superiorly inclined cohorts, respectively. Preoperative inclination was highly associated with postoperative inclination (p = 0.004). When comparing superiorly and neutrally/inferiorly inclined glenospheres, there were no differences in heterotopic ossification (p = 0.606), scapular notching (p = 0.367), American Shoulder and Elbow Surgeons score (p = 0.419), Single Assessment Numeric Evaluation (p = 0.417), Visual Analogue Scale (VAS) pain score (p = 0.290), forward elevation (p = 0.161), external rotation (p = 0.537), or internal rotation (p = 0.656). Conclusion. Compared to neutral and inferior inclination, up to 6° ± 3° of superior glenoid baseplate inclination on a lateralized RSA design produces no differences in postoperative ROM or patient-reported outcomes, and produces similar levels of scapular notching and heterotopic ossification. Additionally, the degree of preoperative inclination represents an important factor in surgical decision-making as it is strongly associated with postoperative inclination. It is important to note that the findings of this study are only reflective of lateralized RSA prostheses. Cite this article: Bone Joint J 2021;103-B(2):360–365

Aims. The aims of this study were to identify means to quantify coronal plane displacement associated with distal radius fractures (DRFs), and to understand their relationship to radial inclination (RI). Methods. From posteroanterior digital radiographs of healed DRFs in 398 female patients aged 70 years or older, and 32 unfractured control wrists, the relationships of RI, quantifiably, to four linear measurements made perpendicular to reference distal radial shaft (DRS) and ulnar shaft (DUS) axes were analyzed: 1) DRS to radial aspect of ulnar head (DRS-U); 2) DUS to volar-ulnar corner of distal radius (DUS-R); 3) DRS to proximal capitate (DRS-PC); and 4) DRS to DUS (interaxis distance, IAD); and, qualitatively, to the distal ulnar fracture, and its intersection with the DUS axis. Results. In the study (fracture) and control groups, respectively, the mean values were: RI, 17.2° (SD 7.2°; -7° to 35°) and 25.6° (SD 2.6°; 21° to 30°); DRS-U, 13.5 mm (SD 1.7; 4.9 to 20.8) and 15.3 mm (SD 0.72; 13.8 to 16.3); DUS-R, 13.4 mm (SD 2.1; 4.8 to 18.5) and 12.0 mm (SD 0.99; 9.7 to 13.9); DRS-PC (positive value radial to DRS, negative value ulnar), 0.14 mm (SD 5.4; -10.9 to 22.7) and -6.1 mm (SD 1.6; -10.6 to -2.3); and IAD, 25.3 mm (SD 2.5; 17.6 to 31.1) and 27.1 mm (SD 1.5; 24.5 to 31.0). All means were significantly different between the study and control groups. RI correlated strongly with DRS-PC. Ulnar styloid fracture intersection with the DUS axis, reflective of ulnar translation of both radial and ulnar shafts, was associated with significantly lower RI. Conclusion. After DRF, the relationship of the proximal capitate to the DRS axis in the coronal plane correlates with the final radial inclination. Additionally, ulnar styloid intersection with the DUS axis is associated with even lower radial inclination. DRF reduction should seek to restore the normal coronal relationship of both radial and ulnar shafts to their distal counterparts. Cite this article: Bone Joint J 2023;105-B(6):688–695

Aims. The aims of this study were: firstly, to investigate the influence of the thickness of cartilage at the sigmoid notch on the inclination of the distal radioulnar joint (DRUJ), and secondly, to compare the sensitivity and specificity of MRI with plain radiographs for the assessment of the inclination of the articular surface of the DRUJ in the coronal plane. . Patients and Methods. Contemporaneous MRI images and radiographs of 100 wrists from 98 asymptomatic patients (mean age 43 years, (16 to 67); 52 male, 53%) with no history of a fracture involving the wrist or surgery to the wrist, were reviewed. The thickness of the cartilage at the sigmoid notch, inclination of the DRUJ and Tolat Type of each DRUJ were determined. . Results. The assessment using MRI scans and cortical bone correlated well with radiographs, with a kappa value of 0.83. The mean difference between the inclination using the cortex and cartilage on MRI scans was 12°, leading to a change of Tolat type of inclination in 66% of wrists. No reverse oblique (Type 3) inclinations were found when using the cartilage to assess inclination. . Conclusion . These data revealed that when measuring the inclination of the DRUJ using cartilage, reverse oblique inclinations might not exist. The data suggest that performing an ulna shortening osteotomy might be reasonable even in distal radioulnar joints where the plain radiographic appearance suggests an unfavourable reverse oblique inclination in the coronal plane. We recommend using MRI to validate radiographs in those that appear to be reverse oblique (Tolat Type 3), as the true inclination might be different, thereby removing one possible contraindication to ulnar shortening. Cite this article: Bone Joint J 2017;99-B:369–75

The angle of inclination of the acetabular component in total hip replacement is a recognised contributing factor in dislocation and early wear. During non-navigated surgery, insertion of the acetabular component has traditionally been performed at an angle of 45° relative to the sagittal plane as judged by the surgeon’s eye, the operative inclination. Typically, the method used to assess inclination is the measurement made on the postoperative anteroposterior radiograph, the radiological inclination. The aim of this study was to measure the intra-operative angle of inclination of the acetabular component on 60 consecutive patients in the lateral decubitus position when using a posterior approach during total hip replacement. This was achieved by taking intra-operative photographs of the acetabular inserter, representing the acetabular axis, and a horizontal reference. The results were compared with the post-operative radiological inclination. The mean post-operative radiological inclination was 13° greater than the photographed operative inclination, which was unexpectedly high. It appears that in the lateral decubitus position with a posterior approach, the uppermost hemipelvis adducts, thus reducing the apparent operative inclination. Surgeons using the posterior approach in lateral decubitus need to aim for a lower operative inclination than when operating with the patient supine in order to achieve an acceptable radiological inclination

Our aim was to compare the degree of patellar descent and alteration in angle of the inclination of the tibial plateau in lateral closing-wedge and medial opening-wedge high tibial osteotomy (HTO) in 51 consecutive patients with osteoarthritis of the medial compartment and varus malalignment. Patellar height was measured by the Insall-Salvati (IS) and the Blackburne-Peel (BP) ratios. The tibial inclination was determined by the Moore-Harvey (MH) method. Multivariate linear regression analysis was used to determine the influence of the type of HTO (closing vs opening wedge) on the post-operative patellar height or tibial inclination. The intra- and interobserver variability of these methods was determined before operation and at follow-up at one year. After an opening-wedge HTO the patellar height was significantly more decreased (mean post-operative difference: IS = 0.15; 95% confidence interval (CI) 0.06 to 0.23; BP = 0.11; 95% CI 0.05 to 0.18) compared with a closing-wedge HTO. The angle of tibial inclination differed significantly (mean post-operative difference MH = −6.40°; 95% CI −8.74 to −4.02) between the two HTO techniques, increasing after opening-wedge HTO and decreasing after closing-wedge HTO. There was no clinically-relevant difference in the intra- and interobserver variability of measurements of patellar height either before or after HTO

We examined the relationships between the serum levels of chromium and cobalt ions and the inclination angle of the acetabular component and the level of activity in 214 patients implanted with a metal-on-metal resurfacing hip replacement. Each patient had a single resurfacing and no other metal in their body. All serum measurements were performed at a minimum of one year after operation. The inclination of the acetabular component was considered to be steep if the abduction angle was greater than 55°. There were significantly higher levels of metal ions in patients with steeply-inclined components (p = 0.002 for chromium, p = 0.003 for cobalt), but no correlation was found between the level of activity and the concentration of metal ions. A highly significant (p < 0.001) correlation with the arc of cover was found. Arcs of cover of less than 10 mm were correlated with a greater risk of high concentrations of serum metal ions. The arc of coverage was also related to the design of the component and to size as well as to the abduction angle of the acetabular component. Steeply-inclined acetabular components, with abduction angles greater than 55°, combined with a small size of component are likely to give rise to higher serum levels of cobalt and chromium ions. This is probably due to a greater risk of edge-loading

We have analysed retrospectively the relationship between the axial parameters of alignment of the lower limb and the recurrence of varus deformity after high tibial osteotomy. We studied 29 patients (37 knees) with a mean age at surgery of 66 years. The mean follow-up was for 7.4 years (5 to 10.5). Recurrence of varus deformity was defined as an increase in the femorotibial angle of 3° or more, compared with that obtained six months after the operation. There were four patients (four knees) with recurrence of varus deformity. They had a greater varus inclination of the distal femur than those without varus recurrence. An association between varus inclination of the distal femur and horizontal obliquity of the joint surface was observed. Excessive obliquity prevents the shift of weight-bearing to the lateral compartment, and may cause a recurrence of varus deformity after high tibial osteotomy

Aims

Several radiological methods of measuring anteversion of the acetabular component after total hip arthroplasty (THA) have been described. These are limited by low reproducibility, are less accurate than CT 3D reconstruction, and are cumbersome to use. These methods also partly rely on the identification of obscured radiological borders of the component. We propose two novel methods, the Area and Orthogonal methods, which have been designed to maximize use of readily identifiable points while maintaining the same trigonometric principles.

Aims. The aims of this study were to determine if an increasing serum cobalt (Co) and/or chromium (Cr) concentration is correlated with a decreasing Harris Hip Score (HHS) and Hip disability and Osteoarthritis Outcome Score (HOOS) in patients who received the Articular Surface Replacement (ASR) hip resurfacing arthroplasty (HRA), and to evaluate the ten-year revision rate and show if sex, inclination angle, and Co level influenced the revision rate. Methods. A total of 62 patients with an ASR-HRA were included and monitored yearly postoperatively. At follow-up, serum Co and Cr levels were measured and the HHS and the HOOS were scored. In addition, preoperative patient and implant variables and the need for revision surgery were recorded. We used a linear mixed model to relate the serum Co and Cr levels to different patient-reported outcome measures (PROMs). For the survival analyses we used the Kaplan-Meier and Cox regression model. Results. We found that an increase of one part per billion (ppb) in serum Co and Cr levels correlated significantly with worsening of the HHS in the following year. This significant correlation was also true for the HOOS-Pain and HOOS-quality of life sub scores. The overall ten-year survival rate in our cohort was 65% (95% confidence interval (CI) 52.5 to 77.6). Cox regression analysis showed a significant hazard ratio (HR) of 1.08 (95% CI 1.01 to 1.15; p = 0.028) for serum Co level. No significance was found with sex or inclination angle. Conclusion. This study shows that increasing serum Co and Cr levels measured in patients with an ASR-HRA are predictive for deterioration in HHS and HOOS subscales in the following year. Increasing serum Co and Cr should forewarn both surgeon and patient that there is a heightened risk of failure. Continued and regular review of patients with an ASR-HRA implant by measurement of serum Co/Cr levels and PROMs remains essential. Cite this article: Bone Joint J 2023;105-B(7):775–782

Aims. There has been limited literature regarding outcomes of acetabular rim syndrome (ARS) with persistent acetabular os in the setting of acetabular dysplasia. The purpose of this study was to characterize a cohort of adolescent and young adult patients with ARS with persistent os and compare their radiological and clinical outcomes to patients with acetabular dysplasia without an os. Methods. We reviewed a prospective database of patients undergoing periacetabular osteotomy (PAO) for symptomatic acetabular dysplasia between January 1999 and December 2021 to identify hips with preoperative os acetabuli, defined as a closed triradiate cartilage but persistence of a superolateral os acetabulum. A total of 14 hips in 12 patients with persistent os acetabuli (ARS cohort) were compared to 50 randomly selected ‘control’ hips without persistent os acetabuli. Preoperative and postoperative radiographs were measured for markers of dysplasia: lateral centre-edge angle, anterior centre-edge angle, acetabular inclination, and migration index. Union of the os was determined in patients with ≥ six months’ follow-up. Patient-reported outcome measures (PROMs) included the University of California, Los Angeles (UCLA) activity score and modified Harris Hip Score (mHHS, maximum score 80) completed at one year postoperatively. Results. There was no significant difference between the ARS and control cohorts with regard to sex distribution (p = 0.270), age at surgery (p = 0.186), or BMI (p = 0.442). Preoperatively, the ARS cohort had more severe dysplasia, including lower lateral centre-edge angle (-9.3° (SD 12.5°) vs 7.6° (SD 10.7°); p < 0.001) and greater acetabular inclination (33.9° (SD 8.2°) vs 21.8° (SD 8.7°); p < 0.001). Postoperatively, 6/13 (46%) hips with ≥ six months of radiological follow up demonstrated union of the os. There was no difference between the ARS and control cohorts at one year in UCLA score (9.1 (SD 1.5) vs 8.2 (SD 1.9); p = 0.167) or mHHS (73.4 (SD 9.5) vs 69.9 (SD 8.8); p = 0.312). Conclusion. ARS with persistent acetabular os may occur in more severe dysplasia. Union occurs in 50% cases following corrective PAO. Cite this article: Bone Joint J 2024;106-B(12):1393–1398

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. Achieving accurate implant positioning and restoring native hip biomechanics are key surgeon-controlled technical objectives in total hip arthroplasty (THA). The primary objective of this study was to compare the reproducibility of the planned preoperative centre of hip rotation (COR) in patients undergoing robotic arm-assisted THA versus conventional THA. Methods. This prospective randomized controlled trial (RCT) included 60 patients with symptomatic hip osteoarthritis undergoing conventional THA (CO THA) versus robotic arm-assisted THA (RO THA). Patients in both arms underwent pre- and postoperative CT scans, and a patient-specific plan was created using the robotic software. The COR, combined offset, acetabular orientation, and leg length discrepancy were measured on the pre- and postoperative CT scanogram at six weeks following surgery. Results. There were no significant differences for any of the baseline characteristics including spinopelvic mobility. The absolute error for achieving the planned horizontal COR was median 1.4 mm (interquartile range (IQR) 0.87 to 3.42) in RO THA versus 4.3 mm (IQR 3 to 6.8; p < 0.001); vertical COR mean 0.91 mm (SD 0.73) in RO THA versus 2.3 mm (SD 1.3; p < 0.001); and combined offset median 2 mm (IQR 0.97 to 5.45) in RO THA versus 3.9 mm (IQR 2 to 7.9; p = 0.019). Improved accuracy was observed with RO THA in achieving the desired acetabular component positioning (root mean square error for anteversion and inclination was 2.6 and 1.3 vs 8.9 and 5.3, repectively) and leg length (mean 0.6 mm vs 1.4 mm; p < 0.001). Patient-reported outcome measures were comparable between the two groups at baseline and one year. Participants in the RO THA group needed fewer physiotherapy sessions postoperatively (median six (IQR 4.5 to 8) vs eight (IQR 6 to 11; p = 0.005). Conclusion. This RCT suggested that robotic-arm assistance in THA was associated with improved accuracy in restoring the native COR, better preservation of the combined offset, leg length correction, and superior accuracy in achieving the desired acetabular component positioning. Further evaluation through long-term and registry data is necessary to assess whether these findings translate into improved implant survival and functional outcomes. Cite this article: Bone Joint J 2024;106-B(4):324–335

Aims. Femoral component anteversion is an important factor in the success of total hip arthroplasty (THA). This retrospective study aimed to investigate the accuracy of femoral component anteversion with the Mako THA system and software using the Exeter cemented femoral component, compared to the Accolade II cementless femoral component. Methods. We reviewed the data of 30 hips from 24 patients who underwent THA using the posterior approach with Exeter femoral components, and 30 hips from 24 patients with Accolade II components. Both groups did not differ significantly in age, sex, BMI, bone quality, or disease. Two weeks postoperatively, CT images were obtained to measure acetabular and femoral component anteversion. Results. The mean difference in femoral component anteversion between intraoperative and postoperative CT measurements (system accuracy of component anteversion) was 0.8° (SD 1.8°) in the Exeter group and 2.1° (SD 2.3°) in the Accolade II group, respectively (p = 0.020). The mean difference in anteversion between the plan and the postoperative CT measurements (clinical accuracy of femoral component anteversion) was 1.2° (SD 3.6°) in the Exeter group, and 4.2° (SD 3.9°) in the Accolade II group (p = 0.003). No significant differences were found in acetabular component inclination and anteversion; however, the clinical accuracy of combined anteversion was significantly better in the Exeter group (0.6° (SD 3.9°)) than the Accolade II group (3.6° (SD 4.1°)). Conclusion. The Mako THA system and software helps surgeons control the femoral component anteversion to achieve the target angle of insertion. The Exeter femoral component, inserted using Mako THA system, showed greater precision for femoral component and combined component anteversion than the Accolade II component. Cite this article: Bone Joint J 2024;106-B(3 Supple A):104–109

Aims. The aim of this study was to examine the implant accuracy of custom-made partial pelvis replacements (PPRs) in revision total hip arthroplasty (rTHA). Custom-made implants offer an option to achieve a reconstruction in cases with severe acetabular bone loss. By analyzing implant deviation in CT and radiograph imaging and correlating early clinical complications, we aimed to optimize the usage of custom-made implants. Methods. A consecutive series of 45 (2014 to 2019) PPRs for Paprosky III defects at rTHA were analyzed comparing the preoperative planning CT scans used to manufacture the implants with postoperative CT scans and radiographs. The anteversion (AV), inclination (IC), deviation from the preoperatively planned implant position, and deviation of the centre of rotation (COR) were explored. Early postoperative complications were recorded, and factors for malpositioning were sought. The mean follow-up was 30 months (SD 19; 6 to 74), with four patients lost to follow-up. Results. Mean CT defined discrepancy (Δ) between planned and achieved AV and IC was 4.5° (SD 3°; 0° to 12°) and 4° (SD 3.5°; 1° to 12°), respectively. Malpositioning (Δ > 10°) occurred in five hips (10.6%). Native COR reconstruction was planned in 42 cases (93%), and the mean 3D deviation vector was 15.5 mm (SD 8.5; 4 to 35). There was no significant influence in malpositioning found for femoral stem retention, surgical approach, or fixation method. Conclusion. At short-term follow-up, we found that PPR offers a viable solution for rTHA in cases with massive acetabular bone loss, as highly accurate positioning can be accomplished with meticulous planning, achieving anatomical reconstruction. Accuracy of achieved placement contributed to reduced complications with no injury to vital structures by screw fixation. Cite this article: Bone Joint J 2022;104-B(10):1110–1117

Aims. Accurate placement of the acetabular component is essential in total hip arthroplasty (THA). The purpose of this study was to determine if the ability to achieve inclination of the acetabular component within the ‘safe-zone’ of 30° to 50° could be improved with the use of an inclinometer. Patients and Methods. We reviewed 167 primary THAs performed by a single surgeon over a period of 14 months. Procedures were performed at two institutions: an inpatient hospital, where an inclinometer was used (inclinometer group); and an ambulatory centre, where an inclinometer was not used as it could not be adequately sterilized (control group). We excluded 47 patients with a body mass index (BMI) of > 40 kg/m. 2. , age of > 68 years, or a surgical indication other than osteoarthritis whose treatment could not be undertaken in the ambulatory centre. There were thus 120 patients in the study, 68 in the inclinometer group and 52 in the control group. The inclination angles of the acetabular component were measured from de-identified plain radiographs by two blinded investigators who were not involved in the surgery. The effect of the use of the inclinometer on the inclination angle was determined using multivariate regression analysis. Results. The mean inclination angle for the THAs in the inclinometer group was 42.9° (95% confidence interval (CI) 41.7° to 44.0°; range 29.0° to 63.8°) and 46.5° (95% CI 45.2° to 47.7°; range 32.8° to 63.2°) in the control group (p < 0.001). Regression analysis identified a 9.1% difference in inclination due to the use of an inclinometer (p < 0.001), and THAs performed without the inclinometer were three times more likely to result in inclination angles of > 50° (odds ratio (OR) 2.8, p = 0.036). The correlation coefficient for the interobserver reliability of the measurement of the two investigators was 0.95 (95% CI 0.93 to 0.97). Conclusion. The use of a simple inclinometer resulted in a significant reduction in the number of outliers compared with a freehand technique. Cite this article: Bone Joint J 2018;100-B:862–6

Aims. The hypothesis of this study was that thigh circumference, distinct from body mass index (BMI), may be associated with the positioning of components when undertaking total hip arthroplasty (THA) using the direct anterior approach (DAA), and that an increased circumference might increase the technical difficulty. Patients and Methods. We performed a retrospective review of prospectively collected data involving 155 consecutive THAs among 148 patients undertaken using the DAA at an academic medical centre by a single fellowship-trained surgeon. Preoperatively, thigh circumference was measured at 10 cm, 20 cm, and 30 cm distal to the anterior superior iliac spine, in quartiles. Two blinded reviewers assessed the inclination and anteversion of the acetabular component, radiological leg-length discrepancy, and femoral offset. The radiological outcomes were considered as continuous and binary outcome variables based on Lewinnek’s ‘safe zone’. Results. Similar trends were seen in all three thigh circumference groups. In multivariable analyses, patients in the largest 20 cm thigh circumference quartile (59 cm to 78 cm) had inclination angles that were a mean of 5.96° larger (95% confidence interval (CI) 2.99° to 8.93°; p < 0.001) and anteversion angles that were a mean of 2.92° larger (95% CI 0.47° to 5.37°; p = 0.020) than the smallest quartile. No significant differences were noted in leg-length discrepancy or offset. Conclusion. There was an associated increase in inclination and anteversion as thigh circumference increased, with no change in the risk of malpositioning the components. THA can be performed using the DAA in patients with large thigh circumference without the risk of malpositioning the acetabular component. Cite this article: Bone Joint J 2019;101-B:529–535

Aims. The aim of this study was to determine whether there is a difference in the rate of wear between acetabular components positioned within and outside the ‘safe zones’ of anteversion and inclination angle. Patients and Methods. We reviewed 100 hips in 94 patients who had undergone primary total hip arthroplasty (THA) at least ten years previously. Patients all had the same type of acetabular component with a bearing couple which consisted of a 28 mm cobalt-chromium head on a highly crosslinked polyethylene (HXLPE) liner. A supine radiostereometric analysis (RSA) examination was carried out which acquired anteroposterior (AP) and lateral paired images. Acetabular component anteversion and inclination angles were measured as well as total femoral head penetration, which was divided by the length of implantation to determine the rate of polyethylene wear. Results. The mean anteversion angle was 19.4° (-15.2° to 48°, . sd. 11.4°), the mean inclination angle 43.4° (27.3° to 60.5°, . sd. 6.6°), and the mean wear rate 0.055 mm/year (. sd. 0.060). Exactly half of the hips were positioned inside the ‘safe zone’. There was no difference (median difference, 0.012 mm/year; p = 0.091) in the rate of wear between acetabular components located within or outside the ‘safe zone’. When compared to acetabular components located inside the ‘safe zone’, the wear rate was no different for acetabular components that only achieved the target anteversion angle (median difference, 0.012 mm/year; p = 0.138), target inclination angle (median difference, 0.013 mm/year; p = 0.354), or neither target (median difference, 0.012 mm/year; p = 0.322). Conclusion. Placing the acetabular component within or outside the ‘safe zone’ did not alter the wear rate of HXLPE at long-term follow-up to a level that risked osteolysis. HXLPE appears to be a forgiving bearing material in terms of articular surface wear, but care must still be taken to position the acetabular component correctly so that the implant is stable. Cite this article: Bone Joint J 2018;100-B:891-7

Aims. The aim of this study was to evaluate the performance of first-generation annealed highly cross-linked polyethylene (HXLPE) in cementless total hip arthroplasty (THA). Methods. We retrospectively evaluated 29 patients (35 hips) who underwent THA between December 2000 and February 2002. The survival rate was estimated using the Kaplan-Meier method. Hip joint function was evaluated using the Japanese Orthopaedic Association (JOA) score. Two-dimensional polyethylene wear was estimated using Martell’s Hip Analysis Suite. We calculated the wear rates between years 1 and 5, 5 and 10, 10 and 15, and 15 and final follow-up. Results. The mean follow-up period was 19.1 years (SD 0.6; 17.3 to 20.1). The 19-year overall survival rate with the end point of all-cause revision was 97.0% (95% confidence interval (CI) 91 to 100). The mean JOA score improved from 43.2 (SD 10.6; 30 to 76) before surgery to 90.2 (SD 6.4; 76 to 98) at the final follow-up (p < 0.001). There was no osteolysis or loosening of the acetabular or femoral components. The overall steady-state wear rate was 0.013 mm/year (SD 0.012). There was no hip with a steady-state wear rate of > 0.1 mm/year. There was no significant difference in wear rates for each period. We found no significant correlation between the wear rate and age, body weight, BMI, or cup inclination. Conclusion. First-generation annealed HXLPE shows excellent wear resistance and no acceleration of wear for approximately 20 years, with low all-cause revision rates. Cite this article: Bone Joint J 2022;104-B(2):200–205

Aims. Head-taper corrosion is a cause of failure in total hip arthroplasty (THA). Recent reports have described an increasing number of V40 taper failures with adverse local tissue reaction (ALTR). However, the real incidence of V40 taper damage and its cause remain unknown. The aim of this study was to evaluate the long-term incidence of ALTR in a consecutive series of THAs using a V40 taper and identify potentially related factors. Methods. Between January 2006 and June 2007, a total of 121 patients underwent THA using either an uncemented (Accolade I, made of Ti. 12. Mo. 6. Zr. 2. Fe; Stryker, USA) or a cemented (ABG II, made of cobalt-chrome-molybdenum (CoCrMo); Stryker) femoral component, both with a V40 taper (Stryker). Uncemented acetabular components (Trident; Stryker) with crosslinked polyethylene liners and CoCr femoral heads of 36 mm diameter were used in all patients. At a mean folllow-up of 10.8 years (SD 1.1), 94 patients (79%) were eligible for follow-up (six patients had already undergone a revision, 15 had died, and six were lost to follow-up). A total of 85 THAs in 80 patients (mean age 61 years (24 to 75); 47 (56%) were female) underwent clinical and radiological evaluation, including the measurement of whole blood levels of cobalt and chrome. Metal artifact reduction sequence MRI scans of the hip were performed in 71 patients. Results. A total of 20 ALTRs were identified on MRI, with an incidence of 26%. Patients with ALTR had significantly higher median Co levels compared with those without ALTR (2.96 μg/l (interquartile range (IQR) 1.35 to 4.98) vs 1.44 μg/l (IQR 0.79 to 2.5); p = 0.019). Radiological evidence of osteolysis was also significantly associated with ALTR (p = 0.014). Median Cr levels were not significantly higher in those with ALTR compared with those without one (0.97 μg/l (IQR 0.72 to 1.9) v 0.67 μg/l (IQR 0.5 to 1.19; p = 0.080). BMI, sex, age, type of femoral component, head length, the inclination of the acetabular component, and heterotopic ossification formation showed no significant relationship with ALTR. Conclusion. Due to the high incidence of local ALTR in our cohort after more than ten years postoperatively, we recommend regular follow-up investigation even in asymptomatic patients with V40 taper and metal heads. As cobalt levels correlate with ALTR occurrence, routine metal ion screening and consecutive MRI investigation upon elevation could be discussed. Cite this article: Bone Joint J 2022;104-B(7):852–858