Removal of the well-fixed hip resurfacing acetabular component: a simple, bone preserving technique

Removal of the acetabular component of a hip resurfacing prosthesis is occasionally necessary for infection, malposition, metal sensitivity, wear, or as a necessary part of a femoral revision. Extraction of a well-fixed acetabular component can be technically demanding as it is often extremely well integrated into host bone and can result in catastrophic bone loss or fracture. We present an undescribed, simple technique that enables use of the Explant system (Zimmer, Warsaw, Ind) to remove the component with minimal bone loss and reduce fracture risk. Bone stock is therefore preserved for subsequent cup reimplantation.     

Birmingham hip resurfacing: the prevalence of failure

Despite the increasing interest and subsequent published literature on hip resurfacing arthroplasty, little is known about the prevalence of its complications and in particular the less common modes of failure. The aim of this study was to identify the prevalence of failure of hip resurfacing arthroplasty and to analyse the reasons for it. From a multi-surgeon series (141 surgeons) of 5000 Birmingham hip resurfacings we have analysed the modes, prevalence, gender differences and times to failure of any hip requiring revision. To date 182 hips have been revised (3.6%). The most common cause for revision was a fracture of the neck of the femur (54 hips, prevalence 1.1%), followed by loosening of the acetabular component (32 hips, 0.6%), collapse of the femoral head/avascular necrosis (30 hips, 0.6%), loosening of the femoral component (19 hips, 0.4%), infection (17 hips, 0.3%), pain with aseptic lymphocytic vascular and associated lesions (ALVAL)/metallosis (15 hips, 0.3%), loosening of both components (five hips, 0.1%), dislocation (five hips, 0.1%) and malposition of the acetabular component (three hips, 0.1%). In two cases the cause of failure was unknown. Comparing men with women, we found the prevalence of revision to be significantly higher in women (women = 5.7%; men = 2.6%, p < 0.001). When analysing the individual modes of failure women had significantly more revisions for loosening of the acetabular component, dislocation, infection and pain/ALVAL/metallosis (p < 0.001, p = 0.004, p = 0.008, p = 0.01 respectively). The mean time to failure was 2.9 years (0.003 to 11.0) for all causes, with revision for fracture of the neck of the femur occurring earlier than other causes (mean 1.5 years, 0.02 to 11.0). There was a significantly shorter time to failure in men (mean 2.1 years, 0.4 to 8.7) compared with women (mean 3.6 years, 0.003 to 11.0) (p < 0.001).     

The ten-year survival of the Birmingham hip resurfacing: an independent series

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.     

Biomechanics of the Birmingham hip resurfacing arthroplasty

The effects of the method of fixation and interface conditions on the biomechanics of the femoral component of the Birmingham hip resurfacing arthroplasty were examined using a highly detailed three-dimensional computer model of the hip. Stresses and strains in the proximal femur were compared for the natural femur and for the femur resurfaced with the Birmingham hip resurfacing. A comparison of cemented versus uncemented fixation showed no advantage of either with regard to bone loading. When the Birmingham hip resurfacing femoral component was fixed to bone, proximal femoral stresses and strains were non-physiological. Bone resorption was predicted in the inferomedial and superolateral bone within the Birmingham hip resurfacing shell. Resorption was limited to the superolateral region when the stem was not fixed. The increased bone strain observed adjacent to the distal stem should stimulate an increase in bone density at that location. The remodelling of bone seen during revision of failed Birmingham hip resurfacing implants appears to be consistent with the predictions of our finite element analysis.     

Clinical and functional outcome of the Birmingham hip resurfacing

The Birmingham hip resurfacing (BHR) arthroplasty has shown good medium-term results in the centres that have been involved in its development. A retrospective cohort study analyzing the clinical and functional outcome of 297 metal-on-metal BHR arthroplasties at an independent hospital was performed. At medium-term follow-up, 4 patients had died, 8 patients were lost to follow-up (2.7%), and 6 hips (2.0%) had undergone revision surgery. The mean Harris hip score (HHS) increased from 56.2 preoperatively to 96.4 at follow-up. The BHR resulted in a very high postoperative HHS and enabled active patients to return to work and engage in sports. With an acceptable revision rate of 2.0% and an overall survival rate of 97.1% at five years, our results were similar to those of the designer centers.     

Birmingham hip resurfacing: a minimum follow-up of ten years

We report the survival, radiological and functional outcomes of a single surgeon series of his first 144 consecutive Birmingham hip resurfacing procedures (130 patients) at a minimum of ten years. There were ten revisions during this time. Although no patients were lost to follow-up some did not complete the scoring assessment or undergo radiological assessment at ten years. The ten-year survival for male patients was 98.0% (95% confidence interval 95.2 to 100). The ten-year survival for the total cohort with aseptic revision as the endpoint was 95.5% (95% confidence interval 91.8 to 99.0) and including revisions for sepsis was 93.5% (95% confidence interval 89.2 to 97.6). The median modified Oxford hip score at ten years was 4.2% (interquartile range 0 to 19) and the median University of California, Los Angeles score was 7.0 (interquartile range 5.0 to 8.0). This study confirms the midterm reports that metal-on-metal hip resurfacing using the Birmingham Hip provides a durable alternative to total hip replacement, particularly in younger male patients wishing to maintain a high level of function, with low risk of revision for at least ten years.     

Internal fixation of an intertrochanteric femoral fracture after Birmingham hip resurfacing arthroplasty

The Birmingham hip system is one of the most popular designs for hip resurfacing. Fractures associated with the Birmingham Hip Resurfacing (BHR) are mostly subcapital fractures. Other traumatic periprosthetic fractures are rarely reported. We report an intertrochanteric fracture which occurred after a Birmingham hip resurfacing. The fracture was treated with a reversed distal femoral locking plate, with a very satisfying clinical and radiological result.     

Comparison of offset in Birmingham hip resurfacing and hybrid total hip arthroplasty

Hip resurfacing is being performed more frequently in the United Kingdom. The possible benefits include more accurate restoration of leg length, femoral offset and femoral anteversion than occurs after total hip arthroplasty (THA). We compared anteroposterior radiographs from 26 patients who had undergone hybrid THA (uncemented cup/cemented stem), with 28 who had undergone Birmingham Hip Resurfacing arthroplasty (BHR). We measured the femoral offset, femoral length, acetabular offset and acetabular height with reference to the normal contralateral hip. The data were analysed by paired t-tests. There was a significant reduction in femoral offset (p = 0.0004) and increase in length (p = 0.001) in the BHR group. In the THA group, there was a significant reduction in acetabular offset (p = 0.0003), but femoral offset and overall hip length were restored accurately. We conclude that hip resurfacing does not restore hip mechanics as accurately as THA.     

Bone density of the femoral neck following Birmingham hip resurfacing

Background Resurfacing is a popular alternative to a standard hip replacement in young arthritic patients. Despite bone preservation around the femoral component, there is little information regarding the bone quality.

Patients and methods 32 patients underwent consecutive Birmingham hip resurfacing. The bone density of the femoral neck was measured preoperatively and then at 6 weeks, 3 months, 1 year, and 2 years. The femoral neck was divided into regions of interest. Results were available for 27 hips in 26 patients.

Results The overall femoral neck bone density showed a trend towards a decrease at 6 weeks and 3 months but returned to the preoperative level at 1 year, and was maintained at 2 years. The combined superior regions of the neck showed a statistically significant decrease in bone density at 6 weeks and 3 months. This returned to preoperative levels at 1 year and was maintained at 2 years.

Interpretation Bone density appears to decrease at 6 weeks and 3 months, suggesting that care is necessary until bone density begins to recover.     

Two-stage exchange for infected resurfacing arthroplasty: use of a novel cement spacer technique

Infection after total hip arthroplasty is a devastating complication. A 2-stage reimplantation with antibiotic-impregnated interval spacer is typically recommended. We present a case of infected resurfacing hip arthroplasty treated with a novel cement spacer technique. The aim was to avoid the introduction of the infection into the femoral medullary canal with the use of a conventional stemmed antibiotic cement spacer. Reimplantation was accomplished routinely, and the patient remains infection-free at 9 months.     

Birmingham hip resurfacing at a mean of ten years: results from an independent centre

We report the findings of an independent review of 230 consecutive Birmingham hip resurfacings (BHRs) in 213 patients (230 hips) at a mean follow-up of 10.4 years (9.6 to 11.7). A total of 11 hips underwent revision; six patients (six hips) died from unrelated causes; and 13 patients (16 hips) were lost to follow-up. The survival rate for the whole cohort was 94.5% (95% confidence interval (CI) 90.1 to 96.9). The survival rate in women was 89.1% (95% CI 79.2 to 94.4) and in men was 97.5% (95% CI 92.4 to 99.2). Women were 1.4 times more likely to suffer failure than men. For each millimetre increase in component size there was a 19% lower chance of a failure. The mean Oxford hip score was 45.0 (median 47.0, 28 to 48); mean University of California, Los Angeles activity score was 7.4 (median 8.0, 3 to 9); mean patient satisfaction score was 1.4 (median 1.0, 0 to 9). A total of eight hips had lysis in the femoral neck and two hips had acetabular lysis. One hip had progressive radiological changes around the peg of the femoral component. There was no evidence of progressive neck narrowing between five and ten years. Our results confirm that BHR provides good functional outcome and durability for men, at a mean follow-up of ten years. We are now reluctant to undertake hip resurfacing in women with this implant.     

Retaining well-fixed cementless stem in the treatment of infected hip arthroplasty

Background and purpose Two-stage reconstruction, reimplantation after removal of an infected prosthesis, has been considered to be the gold standard for treatment of infected hip arthroplasty. However, during the removal of a well-fixed femoral stem, the proximal femur can be damaged and a sequestrum can be formed, which might lead to chronic osteomyelitis and difficulty in reimplantation. We wanted to determine whether infection after hip arthroplasty can be treated without removal of a well-fixed stem.

Methods We treated 19 patients who had an infection after hip replacement, but a well-fixed cementless stem, with 2-stage reconstruction. At the first stage, we removed the acetabular cup, the liner and the head, but not the stem. We then implanted a cup of cement spacer. After control of infection, we reimplanted the acetabular component and head.

Results 2 patients did not undergo second-stage reconstruction because they were satisfied with the pain relief and the activity that they had with the cement-spacer implantation. The remaining 17 patients underwent the second-stage of the reconstruction using cementless arthroplasty. At a mean follow-up time of 4 (2–8) years, 15 of the patients had no recurrence of infection, with satisfactory clinical and radiographic outcome.

Interpretation This second-stage reconstruction after retention of the stem could be an alternative treatment option for periprosthetic infection with a well-fixed stem.     

Ten-year experience using an articulating antibiotic cement hip spacer for the treatment of chronically infected total hip

Infection is a devastating complication after total-hip arthroplasty. Between June 1991 and December 2001, 42 patients were treated at our center for chronically infected total-hip arthroplasty using a 2-stage articulating antibiotic hip spacer technique. Of the 27 patients available for review, 26 (94%) remain clinically free of infection at an average 76 months (range, 28-148 months) postoperatively. Twenty-two (81%) patients had a positive identification of the infecting organism. All patients received a minimum of 6 weeks of intravenous antibiotics and the Harris Hip Scores improved from 53 (range, 36-68) to 92 (range, 81-99) postoperatively. Advantages of this technique include improved patient function, maintenance of bone stock and soft tissue tension, thus simplifying reimplantation.     

A medium-term comparison of hybrid hip replacement and Birmingham hip resurfacing in active young patients

We compared the medium-term clinical and radiological results of hybrid total hip replacement (THR) with metal-on-metal Birmingham hip resurfacing (BHR) in two groups of 54 young patients matched for age, gender, body mass index and pre-operative levels of activity. The clinical outcome was assessed by the University of California, Los Angeles (UCLA) activity score, the Oxford Hip Score (OHS) and the EuroQol scores. Radiologically, all hips were assessed for migration and osteolysis, the hybrid THRs for polyethylene wear and the BHRs for a pedestal sign. The mean follow-up of the patients with a hybrid THR was ten years and for those with a BHR, nine years. Four patients with a hybrid THR and one with a BHR had died. In each group five were lost to follow-up. The revision rate of the hybrid THRs was 16.7% (9 of 54) and of the BHRs 9.3% (5 of 54) (p = 0.195). Radiographs of a further eight hybrid THRs demonstrated wear and osteolysis, and they await revision (p = 0.008). Of the unrevised BHRs 90% had radiological changes, of which approximately 50% had progressed over the previous four years. All hybrid THRs demonstrated linear polyethylene wear with a mean of 1.24 mm (0.06 to 3.03). The BHRs recorded superior OHS (p = 0.013), UCLA (p = 0.008), and EuroQol visual analogue scores (p = 0.009). After nine years, patients with BHRs remained more active and had a lower rate of revision than those with hybrid THRs. Both groups demonstrated progressive radiological changes at medium-term follow-up.     

The nonoperative management of periprosthetic fractures associated with the Birmingham hip resurfacing procedure

We reviewed the outcome of 7 patients sustaining undisplaced femoral neck periprosthetic fractures associated with the Birmingham hip resurfacing procedure. All fractures presented within 4 months of initial surgery. All fractures were treated conservatively with a period of nonweight bearing. The 7 patients were assessed clinically and radiologically at a minimum of 16 months postfracture. All fractures had fully united. There was no evidence of impaired function or abnormal radiological findings after this conservative treatment strategy in 6 patients. One patient had marked femoral neck narrowing but no functional impairment.