Aims

The aim of this study was to radiologically evaluate the quality of cement mantle and alignment achieved with a polished tapered cemented femoral stem inserted through the anterior approach and compared with the posterior approach.

Aims

This study of patients with osteoarthritis (OA) of the hip aimed to: 1) characterize the contribution of the hip, spinopelvic complex, and lumbar spine when moving from the standing to the sitting position; 2) assess whether abnormal spinopelvic mobility is associated with worse symptoms; and 3) identify whether spinopelvic mobility can be predicted from static anatomical radiological parameters.

Aims

Cardiac magnetic resonance (CMR) was used to assess whether cardiac function or tissue composition was affected in patients with well-functioning metal-on-metal hip resurfacing arthroplasties (MoMHRA) when compared with a group of controls, and to assess if metal ion levels correlated with any of the functional or structural parameters studied.

Aims

This study aims to: determine the difference in pelvic position that occurs between surgery and radiographic, supine, postoperative assessment; examine how the difference in pelvic position influences subsequent component orientation; and establish whether differences in pelvic position, and thereafter component orientation, exist between total hip arthroplasties (THAs) performed in the supine versus the lateral decubitus positions.

Aims

Advocates of debridement, antibiotics and implant retention (DAIR) in hip periprosthetic joint infection (PJI) argue that a procedure not disturbing a sound prosthesis-bone interface is likely to lead to better survival and functional outcome compared with revision. This case-control study aims were to compare outcome of DAIRs for infected primary total hip arthroplasty (THA) with outcomes following primary THA and two-stage revision of infected primary THAs.

Objectives

A possible solution for the management of proximal femoral bone loss is a modular femoral endoprosthesis (EPR). Although the outcome of EPRs in tumour surgery has been well described, the outcome of their use in revision hip surgery has received less attention. The aim of this study was to describe the outcome of using EPR for non-neoplastic indications.

We assessed the orientation of the acetabular component in 1070 primary total hip arthroplasties with hard-on-soft, small diameter bearings, aiming to determine the size and site of the target zone that optimises outcome. Outcome measures included complications, dislocations, revisions and ΔOHS (the difference between the Oxford Hip Scores pre-operatively and five years post-operatively). A wide scatter of orientation was observed (2sd 15°). Placing the component within Lewinnek’s zone was not associated withimproved outcome. Of the different zone sizes tested (± 5°, ± 10° and ± 15°), only ± 15° was associated with a decreased rate of dislocation. The dislocation rate with acetabular components inside an inclination/anteversion zone of 40°/15° ± 15° was four times lower than those outside. The only zone size associated with statistically significant and clinically important improvement in OHS was ± 5°. The best outcomes (ΔOHS > 26) were achieved with a 45°/25° ± 5° zone.

This study demonstrated that with traditional technology surgeons can only reliably achieve a target zone of ±15°. As the optimal zone to diminish the risk of dislocation is also ±15°, surgeons should be able to achieve this. This is the first study to demonstrate that optimal orientation of the acetabular component improves the functional outcome. However, the target zone is small (± 5°) and cannot, with current technology, be consistently achieved.

Cite this article: Bone Joint J 2015;97-B:164–72.

There is great variability in acetabular component orientation following hip replacement. The aims of this study were to compare the component orientation at impaction with the orientation measured on post-operative radiographs and identify factors that influence the difference between the two. A total of 67 hip replacements (52 total hip replacements and 15 hip resurfacings) were prospectively studied. Intra-operatively, the orientation of the acetabular component after impaction relative to the operating table was measured using a validated stereo-photogrammetry protocol. Post-operatively, the radiographic orientation was measured; the mean inclination/anteversion was 43° (sd 6°)/ 19° (sd 7°). A simulated radiographic orientation was calculated based on how the orientation would have appeared had an on-table radiograph been taken intra-operatively. The mean difference between radiographic and intra-operative inclination/anteversion was 5° (sd 5°)/ -8° (sd 8°). The mean difference between simulated radiographic and intra-operative inclination/anteversion, which quantifies the effect of the different way acetabular orientation is measured, was 3°/-6° (sd 2°). The mean difference between radiographic and simulated radiographic orientation inclination/anteversion, which is a manifestation of the change in pelvic position between component impaction and radiograph, was 1°/-2° (sd 7°).

This study demonstrated that in order to achieve a specific radiographic orientation target, surgeons should implant the acetabular component 5° less inclined and 8° more anteverted than their target. Great variability (2 sd about ± 15°) in the post-operative radiographic cup orientation was seen. The two equally contributing causes for this are variability in the orientation at which the cup is implanted, and the change in pelvic position between impaction and post-operative radiograph.

Cite this article: Bone Joint J 2014;96-B:1290–7

The orientation of the acetabular component is influenced not only by the orientation at which the surgeon implants the component, but also the orientation of the pelvis at the time of implantation. Hence, the orientation of the pelvis at set-up and its movement during the operation, are important. During 67 hip replacements, using a validated photogrammetric technique, we measured how three surgeons orientated the patient’s pelvis, how much the pelvis moved during surgery, and what effect these had on the final orientation of the acetabular component. Pelvic orientation at set-up, varied widely (mean (± 2, standard deviation (sd))): tilt 8° (2sd ±32), obliquity –4° (2sd ±12), rotation –8° (2sd ±14). Significant differences in pelvic positioning were detected between surgeons (p < 0.001). The mean angular movement of the pelvis between set-up and component implantation was 9° (sd 6). Factors influencing pelvic movement included surgeon, approach (posterior >  lateral), procedure (hip resurfacing > total hip replacement) and type of support (p < 0.001). Although, on average, surgeons achieved their desired acetabular component orientation, there was considerable variability (2sd ±16) in component orientation. We conclude that inconsistency in positioning the patient at set-up and movement of the pelvis during the operation account for much of the variation in acetabular component orientation. Improved methods of positioning and holding the pelvis are required.

Cite this article: Bone Joint J 2014; 96-B:876–83.

Recent events have highlighted the importance of implant design for survival and wear-related complications following metal-on-metal hip resurfacing arthroplasty. The mid-term survival of the most widely used implant, the Birmingham Hip Resurfacing (BHR), has been described by its designers. The aim of this study was to report the ten-year survival and patient-reported functional outcome of the BHR from an independent centre.

In this cohort of 554 patients (646 BHRs) with a mean age of 51.9 years (16.5 to 81.5) followed for a mean of eight years (1 to 12), the survival and patient-reported functional outcome depended on gender and the size of the implant. In female hips (n = 267) the ten-year survival was 74% (95% confidence interval (CI) 83 to 91), the ten-year revision rate for pseudotumour was 7%, the mean Oxford hip score (OHS) was 43 (sd 8) and the mean UCLA activity score was 6.4 (sd 2). In male hips (n = 379) the ten-year survival was 95% (95% CI 92.0 to 97.4), the ten-year revision rate for pseudotumour was 1.7%, the mean OHS was 45 (sd 6) and the mean UCLA score was 7.6 (sd 2). In the most demanding subgroup, comprising male patients aged < 50 years treated for primary osteoarthritis, the survival was 99% (95% CI 97 to 100).

This study supports the ongoing use of resurfacing in young active men, who are a subgroup of patients who tend to have problems with conventional THR. In contrast, the results in women have been poor and we do not recommend metal-on-metal resurfacing in women. Continuous follow-up is recommended because of the increasing incidence of pseudotumour with the passage of time.

Pseudotumour is a rare but important complication of metal-on-metal hip resurfacing that occurs much more commonly in women than in men. We examined the relationship between head-neck ratio (HNR) and pseudotumour formation in 18 resurfaced hips (18 patients) revised for pseudotumour and 42 asymptomatic control resurfaced hips (42 patients).

Patients in whom pseudotumour formation had occurred had higher pre-operative HNR than the control patients (mean 1.37 (sd 0.10) vs mean 1.30 (sd 0.08) p = 0.001). At operation the patients with pseudotumours had a greater reduction in the size of their femoral heads (p = 0.035) and subsequently had greater neck narrowing (mean 10.1% (sd 7.2) vs mean 3.8% (sd 3.2) p < 0.001). No female patient with a pre-operative HNR ≤ 1.3 developed a pseudotumour.

We suggest that reducing the size of the femoral head, made possible by a high pre-operative HNR, increases the risk of impingement and edge loading, and may contribute to high wear and pseudotumour formation. As the incidence of pseudotumour is low in men, it appears safe to perform resurfacing in men. However, this study suggests that it is also reasonable to resurface in women with a pre-operative HNR ≤ 1.3.

Pseudotumours are a rare complication of hip resurfacing. They are thought to be a response to metal debris which may be caused by edge loading due to poor orientation of the acetabular component. Our aim was to determine the optimal acetabular orientation to minimise the risk of pseudotumour formation.

We matched 31 hip resurfacings revised for pseudotumour formation with 58 controls who had a satisfactory outcome from this procedure. The radiographic inclination and anteversion angles of the acetabular component were measured on anteroposterior radiographs of the pelvis using Einzel-Bild-Roentgen-Analyse software. The mean inclination angle (47°, 10° to 81°) and anteversion angle (14°, 4° to 34°) of the pseudotumour cases were the same (p = 0.8, p = 0.2) as the controls, 46° (29° to 60°) and 16° (4° to 30°) respectively, but the variation was greater. Assuming an accuracy of implantation of ± 10° about a target position, the optimal radiographic position was found to be approximately 45° of inclination and 20° of anteversion. The incidence of pseudotumours inside the zone was four times lower (p = 0.007) than outside the zone.

In order to minimise the risk of pseudotumour formation we recommend that surgeons implant the acetabular component at an inclination of 45° (± 10) and anteversion of 20° (± 10) on post-operative radiographs. Because of differences between the radiographic and the operative angles, this may be best achieved by aiming for an inclination of 40° and an anteversion of 25°.