What happens to femoral neck bone mineral density after hip resurfacing surgery?

The outcome and survival of metal-on-metal hip resurfacing in patients aged less than 50 years

Aims

The aim of this study was to report the implant survival and patient-reported outcome measures (PROMs) in a consecutive series of patients aged less than 50 years at the time of arthroplasty using the Birmingham Hip Resurfacing system (BHR), with a minimum follow-up of ten years.

Patients and Methods

A total of 226 patients with osteoarthritis of the hip, who underwent BHR and presented to a single surgeon, were included in the study. Survival of the implant was confirmed by cross-checking with the Australian Orthopaedic Association National Joint Replacement Registry. Kaplan–Meier survival curves with 95% confidence intervals (CIs) were constructed. Pre- and postoperative PROMs were compared with t-tests, and postoperative scores were compared using anchor analysis with age and gender matched normative data.

Results

At median follow-up of 12 years (interquartile range (IQR) 10 to 13), six BHRs were revised, with a cumulative rate of survival of 96.8% (95% confidence interval (CI) 94.2 to 99.4) at 15 years, and with a significantly lower (p = 0.019) cumulative rate of revision than the national average for the same device at ten years. Most revisions (n = 4) were undertaken early, less than three years postoperatively, and occurred in women. Patient-reported general health (Veteran’s Rand-36), disease state (Western Ontario and McMaster Universities Osteoarthritis Index), function (modified Harris Hip Score) and level of activity (Tegner activity score) maintained significant (p < 0.01 for each) improvements beyond ten years postoperatively and were equal to, or exceeded, age- and gender-matched normative data in more than 80% of the patients.

Conclusion

Longer term PROMs after BHR, from a single surgeon, for patients aged less than 50 years remain under-reported. We found that the outcome after a BHR, at a minimum of ten years postoperatively, remained satisfactory, particularly for self-reported hip function.

Hip prostheses in young adults. Surface prostheses and short-stem prostheses

The poor results obtained in young patients when using a conventional prosthesis led to the resurgence of hip resurfacing to find less invasive implants for the bone. Young patients present a demand for additional activity, which makes them a serious challenge for the survival of implants. In addition, new information technologies contribute decisively to the preference for non-cemented prostheses. Maintaining quality of life, preserving the bone and soft tissues, as well as achieving a very stable implant, are the goals of every hip orthopaedic surgeon for these patients. The results in research point to the use of smaller prostheses, which use the metaphyseal zone more and less the diaphyseal zone, and hence the large number of the abovementioned short stem prostheses. Both models are principally indicated in the young adult. Their revision should be a more simple operation, but this is only true for hip resurfacing, not for short stems.

Quantitating the effect of prosthesis design on femoral remodeling using high-resolution region-free densitometric analysis (DXA-RFA)

Dual energy X-ray absorptiometry (DXA) is the reference standard method used to study bone mineral density (BMD) after total hip arthroplasty (THA). However, the subtle, spatially complex changes in bone mass due to strain-adaptive bone remodeling relevant to different prosthesis designs are not readily resolved using conventional DXA analysis. DXA region free analysis (DXA RFA) is a novel computational image analysis technique that provides a high-resolution quantitation of periprosthetic BMD. Here, we applied the technique to quantitate the magnitude and areal size of periprosthetic BMD changes using scans acquired during two previous randomized clinical trials (2004 to 2009); one comparing three cemented prosthesis design geometries, and the other comparing a hip resurfacing versus a conventional cementless prosthesis. DXA RFA resolved subtle differences in magnitude and area of bone remodeling between prosthesis designs not previously identified in conventional DXA analyses. A mean bone loss of 10.3%, 12.1%, and 11.1% occurred for the three cemented prostheses within a bone area fraction of 14.8%, 14.4%, and 6.2%, mostly within the lesser trochanter (p < 0.001). For the cementless prosthesis, a diffuse pattern of bone loss (-14.3%) was observed at the shaft of femur in a small area fraction of 0.6% versus no significant bone loss for the hip resurfacing prosthesis (p < 0.001). BMD increases were observed consistently at the greater trochanter for all prostheses except the hip-resurfacing prosthesis, where BMD increase was widespread across the metaphysis (p < 0.001). DXA RFA provides high-resolution insights into the effect of prosthesis design on the local strain environment in bone. © 2017 The Authors Journal of Orthopaedic Research published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 35:2203-2210, 2017.

Femoral neck remodelling after hip resurfacing surgery: a radiological study

BACKGROUND

Narrowing of the femoral neck under the femoral component of the hip resurfacing has been noted previously and has raised concern. In this study we examined the X-rays of patients following Birmingham hip resurfacing surgery at 6-years follow-up.

METHODS

Bony changes proximally and distally were measured. Fifty-two patients were available for evaluation.

RESULTS

There were 40 (76.9%) men and 12 (23.1%) women, with a mean age of 52 years (25-64). The unoperated contralateral femoral neck was measured as a control. We found femoral neck narrowing proximally in 82.7% of patients and distally in 26.9% and on the contralateral side in 54.5%. The average narrowing was 3.6%. Widening was observed proximally in 17.3% and distally in 73.1% and on the contralateral side in 45.5%. The average widening was 3.9%. Four of the 52 patients had proximal narrowing exceeding 10% of the femoral neck diameter, and one of the 52 patients had inferior narrowing exceeding 10%.

CONCLUSION

Gender, body mass index, component size and age did not affect remodelling. We conclude that the observed findings are likely to be a manifestation of a generalized remodelling response in the femoral neck rather than a localized and isolated narrowing at the junction of the component and the femoral neck.

Metal-on-metal hip resurfacing in patients aged 65 or older

There is little information regarding the clinical performance of hip resurfacing arthroplasty (HRA) in older patients. Eighty-seven patients (99 hips) aged 65 years or older received HRA while a control group of 52 patients (64 hips) received a primary THA. The average age was 69.2 years for the HRA group and 71.9 years for the THA group. Follow-up ranged from 2 to 13 years. UCLA walking, function and activity scores and SF-12 scores were higher in the HRA group. At 10 years, the Kaplan-Meier overall survivorship rates were 96.7% for the HRA group and 91.2% for the THA group (p = 0.3174). We suggest considering hip resurfacing for patients 65 or older in centres where there is expertise in performing this procedure.

Changes in bone mineral density of the acetabulum, femoral neck and femoral shaft, after hip resurfacing and total hip replacement

It is accepted that resurfacing hip replacement preserves the bone mineral density (BMD) of the femur better than total hip replacement (THR). However, no studies have investigated any possible difference on the acetabular side.

Between April 2007 and March 2009, 39 patients were randomised into two groups to receive either a resurfacing or a THR and were followed for two years. One patient’s resurfacing subsequently failed, leaving 19 patients in each group.

Resurfaced replacements maintained proximal femoral BMD and, compared with THR, had an increased bone mineral density in Gruen zones 2, 3, 6, and particularly zone 7, with a gain of 7.5% (95% confidence interval (CI) 2.6 to 12.5) compared with a loss of 14.6% (95% CI 7.6 to 21.6). Resurfacing replacements maintained the BMD of the medial femoral neck and increased that in the lateral zones between 12.8% (95% CI 4.3 to 21.4) and 25.9% (95% CI 7.1 to 44.6).

On the acetabular side, BMD was similar in every zone at each point in time. The mean BMD of all acetabular regions in the resurfaced group was reduced to 96.2% (95% CI 93.7 to 98.6) and for the total hip replacement group to 97.6% (95% CI 93.7 to 101.5) (p = 0.4863). A mean total loss of 3.7% (95% CI 1.0 to 6.5) and 4.9% (95% CI 0.8 to 9.0) of BMD was found above the acetabular component in W1 and 10.2% (95% CI 0.9 to 19.4) and 9.1% (95% CI 3.8 to 14.4) medial to the implant in W2 for resurfaced replacements and THRs respectively. Resurfacing resulted in a mean loss of BMD of 6.7% (95% CI 0.7 to 12.7) in W3 but the BMD inferior to the acetabular component was maintained in both groups.

These results suggest that the ability of a resurfacing hip replacement to preserve BMD only applies to the femoral side.

Early complications of hip resurfacing

There has been a rapid increase in the number of hip resurfacing procedures for the treatment of symptomatic osteoarthritis over the last decade. We examine our early complications associated with this procedure. Eight hundred forty consecutive hip resurfacing procedures by 1 surgeon using 1 prosthesis were assessed. The complications seen within the first 12-month postoperative period were analyzed. Specific patient selection criteria were used. Complications such as loosening, femoral neck notching, femoral neck fracture, deep vein thrombosis, stress fracture, nerve palsy, and infection were noted. Complications linked with loosening were categorized to either the femoral or acetabular component. A total of 86 early complications were observed in the 840 resurfacings. Twenty-three (2.7%) required operative intervention, and 10 (1.2%) were converted to stemmed hip arthroplasties. Of these 86 complications, the most common complication was deep vein thrombosis, 19 instances (2.26% occurrence in 840), followed by femoral neck fracture, 11 (1.31%); infection, 10 (1.19%); femoral notching, 10 (1.19%); transient nerve palsy, 8 (0.95%); acetabular loosening, 6 (0.71%); hematoma, 5 (0.60%); and stress fracture, 4 (0.48%). The fractures occurred mostly in patients older than 60 years.