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

Objectives. Acetabular component orientation in total hip arthroplasty (THA) influences results. Intra-operatively, the natural arthritic acetabulum is often used as a reference to position the acetabular component. Detailed information regarding its orientation is therefore essential. The aim of this study was to identify the acetabular inclination and anteversion in arthritic hips. Methods. Acetabular inclination and anteversion in 65 symptomatic arthritic hips requiring THA were measured using a computer navigation system. All patients were Caucasian with primary osteoarthritis (29 men, 36 women). The mean age was 68 years (SD 8). Mean inclination was 50.5° (SD 7.8) in men and 52.1° (SD 6.7) in women. Mean anteversion was 8.3° (SD 8.7) in men and 14.4° (SD 11.6) in women. . Results. The difference between men and women in terms of anteversion was significant (p = 0.022). In 75% of hips, the natural orientation was outside the safe zone described by Lewinnek et al (anteversion 15° ± 10°; inclination 40° ± 10°). Conclusion. When using the natural acetabular orientation to guide component placement, it is important to be aware of the differences between men and women, and that in up to 75% of hips natural orientation may be out of what many consider to be a safe zone. Cite this article: Bone Joint Res 2015;4:6–10

Aims. Arthroplasty skills need to be acquired safely during training, yet operative experience is increasingly hard to acquire by trainees. Virtual reality (VR) training using headsets and motion-tracked controllers can simulate complex open procedures in a fully immersive operating theatre. The present study aimed to determine if trainees trained using VR perform better than those using conventional preparation for performing total hip arthroplasty (THA). Patients and Methods. A total of 24 surgical trainees (seven female, 17 male; mean age 29 years (28 to 31)) volunteered to participate in this observer-blinded 1:1 randomized controlled trial. They had no prior experience of anterior approach THA. Of these 24 trainees, 12 completed a six-week VR training programme in a simulation laboratory, while the other 12 received only conventional preparatory materials for learning THA. All trainees then performed a cadaveric THA, assessed independently by two hip surgeons. The primary outcome was technical and non-technical surgical performance measured by a THA-specific procedure-based assessment (PBA). Secondary outcomes were step completion measured by a task-specific checklist, error in acetabular component orientation, and procedure duration. Results. VR-trained surgeons performed at a higher level than controls, with a median PBA of Level 3a (procedure performed with minimal guidance or intervention) versus Level 2a (guidance required for most/all of the procedure or part performed). VR-trained surgeons completed 33% more key steps than controls (mean 22 (. sd. 3) vs 12 (. sd. 3)), were 12° more accurate in component orientation (mean error 4° (. sd. 6°) vs 16° (. sd. 17°)), and were 18% faster (mean 42 minutes (. sd. 7) vs 51 minutes (. sd. 9)). Conclusion. Procedural knowledge and psychomotor skills for THA learned in VR were transferred to cadaveric performance. Basic preparatory materials had limited value for trainees learning a new technique. VR training advanced trainees further up the learning curve, enabling highly precise component orientation and more efficient surgery. VR could augment traditional surgical training to improve how surgeons learn complex open procedures. Cite this article: Bone Joint J 2019;101-B:1585–1592

Bioengineering reasons for increased wear and failure of metal-on-metal (MoM) bearings in hip prostheses have been described. Low wear occurs in MoM hips when the centre of the femoral head is concentric with the centre of the acetabular component and the implants are correctly positioned. Translational or rotational malpositioning of the components can lead to the contact-patch of the femoral component being displaced to the rim of the acetabular component, resulting in a ten- to 100-fold increase in wear and metal ion levels. This may cause adverse tissue reactions, loosening of components and failure of the prosthesis

Aims. It has been suggested that cemented fixation of total hip arthroplasty (THA) is associated with an increased peri-operative mortality compared with cementless THA. Our aim was to investigate this through a nationwide matched cohort study adjusting for age, comorbidity, and socioeconomic background. Patients and Methods. A total of 178 784 patients with osteoarthritis who underwent either cemented or cementless THA from the Swedish Hip Arthroplasty Register were matched with 862 294 controls from the general population. Information about the causes of death, comorbidities, and socioeconomic background was obtained. Mortality within the first 90 days after the operation was the primary outcome measure. Results. Patients who underwent cemented THA had an increased risk of death during the first 14 days compared with the controls (hazard ratio (HR) 1.3, confidence interval (CI) 1.11 to 1.44), corresponding to an absolute increase in risk of five deaths per 10 000 observations. No such early increase of risk was seen in those who underwent cementless THA. Between days 15 and 29 the risk of mortality was decreased for those with cemented THA (HR 0.7, CI 0.62 to 0.87). Between days 30 and 90 all patients undergoing THA, irrespective of the mode of fixation, had a lower risk of death than controls. Patients selected for cementless fixation were younger, healthier and had a higher level of education and income than those selected for cemented THA. A supplementary analysis of 16 556 hybrid THAs indicated that cementation of the femoral component was associated with a slight increase in mortality up to 15 days, whereas no such increase in mortality was seen in those with a cemented acetabular component combined with a cementless femoral component. Conclusion. This nationwide matched cohort study indicates that patients receiving cemented THA have a minimally increased relative risk of early mortality that is reversed from day 15 and thereafter. The absolute increase in risk is very small. Our findings lend support to the idea that cementation of the femoral component is more dangerous than cementation of the acetabular component. Cite this article: Bone Joint J 2017;99-B:37–43

Pre-operative planning for total hip replacement (THR) is challenging in hips with severe acetabular deformities, including those with a hypoplastic acetabulum or severe defects and in the presence of arthrodesis or ankylosis. We evaluated whether a Rapid Prototype (RP) model, which is a life-sized reproduction based on three-dimensional CT scans, can determine the feasibility of THR and provide information about the size and position of the acetabular component in severe acetabular deformities. THR was planned using an RP model in 21 complex hips in five men (five hips) and 16 women (16 hips) with a mean age of 47.7 years (24 to 70) at operation. An acetabular component was implanted successfully and THR completed in all hips. The acetabular component used was within 2 mm of the predicted size in 17 hips (80.9%). All of the acetabular components and femoral stems had radiological evidence of bone ingrowth and stability at the final follow-up, without any detectable wear or peri-prosthetic osteolysis. The RP model allowed a simulated procedure pre-operatively and was helpful in determining the feasibility of THR pre-operatively, and to decide on implant type, size and position in complex THRs. Cite this article: Bone Joint J 2013;95-B:1458–63

We report the results at a mean of 24.3 years (20 to 32) of 61 previously reported consecutive total hip replacements carried out on 44 patients with severe congenital hip disease, performed with reconstruction of the acetabulum with an impaction grafting technique known as cotyloplasty. The mean age of the patients at operation was 46.7 years (23 to 68) and all were women. The patients were followed post-operatively for a mean of 24.3 years (20 to 32), using the Merle d’Aubigné and Postel scoring system as modified by Charnley, and with serial radiographs. At the time of the latest follow-up, 28 acetabular components had been revised because of aseptic loosening at a mean of 15.9 years (6 to 26), and one at 40 days after surgery because of repeated dislocations. The overall survival rate for aseptic failure of the acetabular component at ten years was 93.1% (95% confidence interval (CI) 86.5 to 96.7) when 53 hips were at risk, and at 23 years was 56.1% (95% CI 49.4 to 62.8), when 22 hips remained at risk. These long-term results are considered satisfactory for the reconstruction of an acetabulum presenting with inadequate bone stock and circumferential segmental defects. Cite this article: Bone Joint J 2013;95-B:887–92

In this prospective study we studied the effect of the inclination angle of the acetabular component on polyethylene wear and component migration in cemented acetabular sockets using radiostereometric analysis. A total of 120 patients received either a cemented Reflection All-Poly ultra-high-molecular-weight polyethylene or a cemented Reflection All-Poly highly cross-linked polyethylene acetabular component, combined with either cobalt–chrome or Oxinium femoral heads. Femoral head penetration and migration of the acetabular component were assessed with repeated radiostereometric analysis for two years. The inclination angle was measured on a standard post-operative anteroposterior pelvic radiograph. Linear regression analysis was used to determine the relationship between the inclination angle and femoral head penetration and migration of the acetabular component. We found no relationship between the inclination angle and penetration of the femoral head at two years’ follow-up (p = 0.9). Similarly, our data failed to reveal any statistically significant correlation between inclination angle and migration of these cemented acetabular components (p = 0.07 to p = 0.9)

Aims. The use of trabecular metal (TM) shells supported by augments has provided good mid-term results after revision total hip arthroplasty (THA) in patients with a bony defect of the acetabulum. The aim of this study was to assess the long-term implant survivorship and radiological and clinical outcomes after acetabular revision using this technique. Patients and Methods. Between 2006 and 2010, 60 patients (62 hips) underwent acetabular revision using a combination of a TM shell and augment. A total of 51 patients (53 hips) had complete follow-up at a minimum of seven years and were included in the study. Of these patients, 15 were men (29.4%) and 36 were women (70.6%). Their mean age at the time of revision THA was 64.6 years (28 to 85). Three patients (5.2%) had a Paprosky IIA defect, 13 (24.5%) had a type IIB defect, six (11.3%) had a type IIC defect, 22 (41.5%) had a type IIIA defect, and nine (17%) had a type IIIB defect. Five patients (9.4%) also had pelvic discontinuity. Results. The overall survival of the acetabular component at a mean of ten years postoperatively was 92.5%. Three hips (5.6%) required further revision due to aseptic loosening, and one (1.9%) required revision for infection. Three hips with aseptic loosening failed, due to insufficient screw fixation of the shell in two and pelvic discontinuity in one. The mean Harris Hip Score improved significantly from 55 (35 to 68) preoperatively to 81 points (68 to 99) at the latest follow-up (p < 0.001). Conclusion. The reconstruction of acetabular defects with TM shells and augments showed excellent long-term results. Supplementary screw fixation of the shell should be performed in every patient. Alternative techniques should be considered to address pelvic disconinuity. Cite this article: Bone Joint J 2019;101-B:311–316

Objective. This study compared the primary stability of two commercially available acetabular components from the same manufacturer, which differ only in geometry; a hemispherical and a peripherally enhanced design (peripheral self-locking (PSL)). The objective was to determine whether altered geometry resulted in better primary stability. Methods. Acetabular components were seated with 0.8 mm to 2 mm interference fits in reamed polyethylene bone substrate of two different densities (0.22 g/cm. 3. and 0.45 g/cm. 3. ). The primary stability of each component design was investigated by measuring the peak failure load during uniaxial pull-out and tangential lever-out tests. Results. There was no statistically significant difference in seating force (p = 0.104) or primary stability (pull-out p = 0.171, lever-out p = 0.087) of the two components in the low-density substrate. Similarly, in the high-density substrate, there was no statistically significant difference in the peak pull-out force (p = 0.154) or lever-out moment (p = 0.574) between the designs. However, the PSL component required a significantly higher seating force than the hemispherical cup in the high-density bone analogue (p = 0.006). Conclusions. Higher seating forces associated with the PSL design may result in inadequate seating and increased risk of component malpositioning or acetabular fracture in the intra-operative setting in high-density bone stock. Our results, if translated clinically, suggest that a purely hemispherical geometry may have an advantage over a peripherally enhanced geometry in high density bone stock. Cite this article: Bone Joint Res 2013;2:264–9

The inherent challenges of total hip replacement (THR) in children include the choice of implant for the often atypical anatomical morphology, its fixation to an immature growing skeleton and the bearing surface employed to achieve a successful long-term result. We report the medium-term results of 52 consecutive uncemented THRs undertaken in 35 paediatric patients with juvenile idiopathic arthritis. The mean age at the time of surgery was 14.4 years (10 to 16). The median follow-up was 10.5 years (6 to 15). During the study period 13 THRs underwent revision surgery. With revision as an endpoint, subgroup analysis revealed 100% survival of the 23 ceramic-on-ceramic THRs and 55% (16 of 29) of the metal- or ceramic-on-polyethylene. This resulted in 94% (95% CI 77.8 to 98.4) survivorship of the femoral component and 62% (95% CI 41.0 to 78.0) of the acetabular component. Revision of the acetabular component for wear and osteolysis were the most common reasons for failure accounting for 11 of the 13 revisions. The success seen in patients with a ceramic-on-ceramic articulation seems to indicate that this implant strategy has the potential to make a major difference to the long-term outcome in this difficult group of patients

We studied a consecutive series of 285 uncemented total hip replacements in 260 patients using the Taperloc femoral component and the T-Tap acetabular component. The outcome of every hip was determined in both living and deceased patients. A complete clinical and radiological follow-up was obtained for 209 hips in 188 living patients, followed for a mean of 14.5 years (10 to 18.9). They were divided into two groups, obese and non-obese, as determined by their body mass index. There were 100 total hip replacements in 89 patients in the obese cohort (body mass index ≥ 30 kg/m. 2. ), and 109 in 99 non-obese (body mass index < 30 kg/m. 2. ) patients. A subgroup analysis of 31 patients of normal weight (body mass index 20 kg/m. 2. to 25 kg/m. 2. ) (33 hips) and 26 morbidly obese patients (body mass index ≥ 35 kg/m. 2. ) (30 hips) was also carried out. In the obese group five femoral components (5%) were revised and one (1%) was loose by radiological criteria. Femoral cortical osteolysis was seen in eight hips (8%). The acetabular component was revised in 57 hips (57%) and a further 17 (17%) were loose. The mean Harris hip score improved from 52 (30 to 66) pre-operatively to 89 (49 to 100) at final follow-up. Peri-operative complications occurred in seven patients (7%). In the non-obese group six (6%) femoral components were revised and one (1%) was loose. Femoral cortical osteolysis occurred in six hips (6%). The acetabular component was revised in 72 hips (66%) and a further 18 (17%) were loose. The mean Harris hip score increased from 53 (25 to 73) prior to surgery to 89 (53 to 100) at the time of each patient’s final follow-up radiograph. No statistically significant difference was identified between the obese and non-obese patients with regards to clinical and radiological outcome or complications. The subgroup analysis of patients of normal weight and those who were morbidly obese showed no statistically significant difference in the rate of revision of either component. Our findings suggest there is no evidence to support withholding total hip replacement from obese patients with arthritic hips on the grounds that their outcome will be less satisfactory than those who are not obese

The Articular Surface Replacement (ASR) hip resurfacing arthroplasty has a failure rate of 12.0% at five years, compared with 4.3% for the Birmingham Hip Resurfacing (BHR). We analysed 66 ASR and 64 BHR explanted metal-on-metal hip replacements with the aim of understanding their mechanisms of failure. We measured the linear wear rates of the acetabular and femoral components and analysed the clinical cause of failure, pre-revision blood metal ion levels and orientation of the acetabular component. There was no significant difference in metal ion levels (chromium, p = 0.82; cobalt, p = 0.40) or head wear rate (p = 0.14) between the two groups. The ASR had a significantly increased rate of wear of the acetabular component (p = 0.03) and a significantly increased occurrence of edge loading (p < 0.005), which can be attributed to differences in design between the ASR and BHR. The effects of differences in design on the in vivo wear rates are discussed: these may provide an explanation as to why the ASR is more sensitive to suboptimal positioning than the BHR

The purpose of this study was to define immediate post-operative ‘quality’ in total hip replacements and to study prospectively the occurrence of failure based on these definitions of quality. The evaluation and assessment of failure were based on ten radiological and clinical criteria. The cumulative summation (CUSUM) test was used to study 200 procedures over a one-year period. Technical criteria defined failure in 17 cases (8.5%), those related to the femoral component in nine (4.5%), the acetabular component in 32 (16%) and those relating to discharge from hospital in five (2.5%). Overall, the procedure was considered to have failed in 57 of the 200 total hip replacements (28.5%). The use of a new design of acetabular component was associated with more failures. For the CUSUM test, the level of adequate performance was set at a rate of failure of 20% and the level of inadequate performance set at a failure rate of 40%; no alarm was raised by the test, indicating that there was no evidence of inadequate performance. The use of a continuous monitoring statistical method is useful to ensure that the quality of total hip replacement is maintained, especially as newer implants are introduced

Aims. The routine use of dual-mobility (DM) acetabular components in total hip arthroplasty (THA) may not be cost-effective, but an increasing number of patients undergoing THA have a coexisting spinal disorder, which increases the risk of postoperative instability, and these patients may benefit from DM articulations. This study seeks to examine the cost-effectiveness of DM components as an alternative to standard articulations in these patients. Patients and Methods. A decision analysis model was used to evaluate the cost-effectiveness of using DM components in patients who would be at high risk for dislocation within one year of THA. Direct and indirect costs of dislocation, incremental costs of using DM components, quality-adjusted life-year (QALY) values, and the probabilities of dislocation were derived from published data. The incremental cost-effectiveness ratio (ICER) was established with a willingness-to-pay threshold of $100 000/QALY. Sensitivity analysis was used to examine the impact of variation. Results. In the base case, patients with a spinal deformity were modelled to have an 8% probability of dislocation following primary THA based on published clinical ranges. Sensitivity analysis revealed that, at its current average price ($1000), DM is cost-effective if it reduces the probability of dislocation to 0.9%. The threshold cost at which DM ceased being cost-effective was $1180, while the ICER associated with a DM THA was $71 000 per QALY. Conclusion. These results indicate that under specific clinical and economic thresholds, DM components are a cost-effective form of treatment for patients with spinal deformity who are at high risk of dislocation after THA. Cite this article: Bone Joint J 2018;100-B:1297–1302

Aims. We investigated the long-term performance of the Tripolar Trident acetabular component used for recurrent dislocation in revision total hip arthroplasty. We assessed: 1) rate of re-dislocation; 2) incidence of complications requiring re-operation; and 3) Western Ontario and McMaster Universities osteoarthritis index (WOMAC) pain and functional scores. Patients and Methods. We retrospectively identified 111 patients who had 113 revision tripolar constrained liners between 1994 and 2008. All patients had undergone revision hip arthroplasty before the constrained liner was used: 13 after the first revision, 17 after the second, 38 after the third, and 45 after more than three revisions. A total of 75 hips (73 patients) were treated with Tripolar liners due to recurrent instability with abductor deficiency, In addition, six patients had associated cerebral palsy, four had poliomyelitis, two had multiple sclerosis, two had spina bifida, two had spondyloepiphyseal dysplasia, one had previous reversal of an arthrodesis, and 21 had proximal femoral replacements. The mean age of patients at time of Tripolar insertions was 72 years (53 to 89); there were 69 female patients (two bilateral) and 42 male patients. All patients were followed up for a mean of 15 years (10 to 24). Overall, 55 patients (57 hips) died between April 2011 and February 2018, at a mean of 167 months (122 to 217) following their tripolar liner implantation. We extracted demographics, implant data, rate of dislocations, and incidence of other complications. Results. At ten years, the Kaplan–Meier survivorship for dislocation was 95.6% (95% confidence interval (CI) 90 to 98), with 101 patients at risk. At 20 years, the survivorship for dislocation was 90.6% (95% CI 81.0 to 95.5), with one patient at risk. Eight patients (7.2%) had a dislocation of their constrained liners. At ten years, the survival to any event was 89.4% (95% CI 82 to 93.8), with 96 patients at risk. At 20 years, the survival to any event was 82.5% (95% CI 71.9 to 89.3), with one patient at risk. Five hips (4.4%) had deep infection. Two patients (1.8%) developed dissociated constraining rings with pain but without dislocation, which required re-operation. Two patients (1.8%) had periprosthetic femoral fractures, without dislocation, that were treated by revision stems along with exchange of the well-functioning constrained liners. Conclusion. Constrained tripolar liners used at revision hip arthroplasty provided favourable results in the long term for treatment of recurrent dislocation and for patients at high risk of dislocation. Cite this article: Bone Joint J 2019;101-B(6 Supple B):123–126

We have reviewed 42 patients who had revision of metal-on-metal resurfacing procedures, mostly because of problems with the acetabular component. The revisions were carried out a mean of 26.2 months (1 to 76) after the initial operation and most of the patients (30) were female. Malpositioning of the acetabular component resulted in 27 revisions, mostly because of excessive abduction (mean 69.9°; 56° to 98°) or insufficient or excessive anteversion. Seven patients had more than one reason for revision. The mean increase in the diameter of the component was 1.8 mm (0 to 4) when exchange was needed. Malpositioning of the components was associated with metallosis and a high level of serum ions. The results of revision of the femoral component to a component with a modular head were excellent, but four patients had dislocation after revision and four required a further revision

The aim of this prospective randomised study was to compare the clinical and radiological results of a cemented all-polyethylene Ultima acetabular component with those of a cementless porous-coated acetabular component (PFC) following total hip replacement (THR). A total of 287 patients received either a polyethylene acetabular component (group A) or a cobalt–chromium porous-coated component (group B) with an identical cemented femoral component and 28 mm cobalt-chromium head, thus making it the largest study of its type. Patients were evaluated radiologically and clinically using the Harris hip score (HHS). Group A comprised 183 patients (73 male, 110 female) with a mean age of 71.3 years (55 to 89). Group B comprised 104 patients (48 male, 56 female) with a mean age of 69.8 years (56 to 89). A total of 16 patients (13 in Group A, three in Group B) did not have post-operative data for analysis. The mean follow-up in group A was 7.52 years (0.4 to 15.0) and in Group B 7.87 years (0.5 to 14.0). At final follow-up the mean HHS was similar between groups A and B (74.5 (25 to 100) and 78.0 (37 to 100), respectively; p = 0.068). The total number of revisions for any cause was 28, 17 of which were in group A and 11 in group B. The ten-year survivorship was 86.8% (95% confidence interval (CI) 78.4 to 92.1) and 89.2% (95% CI 78.3 to 94.8) for groups A and B, respectively (log-rank p-value = 0.938). A total of 20 cemented and two cementless acetabular components had evidence of acetabular radiolucencies or acetabular component migration at last follow-up (p = 0.001). These results indicate that patients with a cemented all-polyethylene and cementless porous-coated polyethylene lined acetabular component have similar long-term clinical outcomes

Aims. The aim of this study was to evaluate the accuracy of implant placement when using robotic assistance during total hip arthroplasty (THA). Patients and Methods. A total of 20 patients underwent a planned THA using preoperative CT scans and robotic-assisted software. There were nine men and 11 women (n = 20 hips) with a mean age of 60.8 years (. sd. 6.0). Pelvic and femoral bone models were constructed by segmenting both preoperative and postoperative CT scan images. The preoperative anatomical landmarks using the robotic-assisted system were matched to the postoperative 3D reconstructions of the pelvis. Acetabular and femoral component positions as measured intraoperatively and postoperatively were evaluated and compared. Results. The system reported accurate values for reconstruction of the hip when compared to those measured postoperatively using CT. The mean deviation from the executed overall hip length and offset were 1.6 mm (. sd. 2.9) and 0.5 mm (. sd. 3.0), respectively. Mean combined anteversion was similar and correlated between intraoperative measurements and postoperative CT measurements (32.5°, . sd. 5.9° versus 32.2°, . sd. 6.4°; respectively; R. 2. = 0.65; p < 0.001). There was a significant correlation between mean intraoperative (40.4°, . sd. 2.1°) acetabular component inclination and mean measured postoperative inclination (40.12°, . sd. 3.0°, R. 2. = 0.62; p < 0.001). There was a significant correlation between mean intraoperative version (23.2°, . sd. 2.3°), and postoperatively measured version (23.0°, . sd. 2.4°; R. 2. = 0.76; p < 0.001). Preoperative and postoperative femoral component anteversion were significantly correlated with one another (R. 2. = 0.64; p < 0.001). Three patients had CT scan measurements that differed substantially from the intraoperative robotic measurements when evaluating stem anteversion. Conclusion. This is the first study to evaluate the success of hip reconstruction overall using robotic-assisted THA. The overall hip reconstruction obtained in the operating theatre using robotic assistance accurately correlated with the postoperative component position assessed independently using CT based 3D modelling. Clinical correlation during surgery should continue to be practiced and compared with observed intraoperative robotic values. Cite this article: Bone Joint J 2018;100-B:1303–9

There have been comparatively few studies of the incidence of osteolysis and the survival of hybrid and cementless total hip replacements (THRs) in patients younger than 50 years of age. We prospectively reviewed 78 patients (109 hips) with a hybrid THR having a mean age of 43.4 years (21 to 50) and 79 patients (110 hips) with a cementless THR with a mean age of 46.8 years (21 to 49). The patients were evaluated clinically using the Harris hip score, the Western Ontario and McMaster Universities (WOMAC) osteoarthritis score and the University of California, Los Angeles (UCLA) activity score. Radiographs and CT scans were assessed for loosening and osteolysis. The mean follow-up was for 18.4 years (16 to 19) in both groups. The mean post-operative Harris hip scores (91 points versus 90 points), the mean WOMAC scores (11 points versus 13 points) and UCLA activity scores (6.9 points versus 7.1 points) were similar in both groups. The revision rates of the acetabular component (13% versus 16%) and the femoral component (3% versus 4%), and the survival of the acetabular component (87% versus 84%) and the femoral component (97% versus 96%) were similar in both groups. Although the long-term fixation of the acetabular metallic shell and the cemented and cementless femoral components was outstanding, wear and peri-acetabular osteolysis constitute the major challenges of THR in young patients