Removal of acetabular bone in resurfacing arthroplasty of the hip

Comparison of Radiographic and Pathologic Diagnosis of Osteonecrosis of the Femoral Head

OBJECTIVE. The purpose of this study was to assess the utility of radiography in diagnosing osteonecrosis of the femoral head with pathologic examination as the reference standard. MATERIALS AND METHODS. Radiography and pathology reports of 253 consecutive femoral head resections were reviewed. A subset of 128 cases in which the diagnosis of osteonecrosis was made or suggested radiographically or pathologically were reviewed to evaluate for factors that might influence correlation. A total of 23 patients in this subset had also undergone MRI, and those reports and images were reviewed. RESULTS. There was 93.9% agreement between radiography and pathologic examination overall (κ = 0.67). When grade 3 osteoarthritis was present, 95.0% agreement was found, but because of the large number of patients with severe osteoarthritis, the kappa value decreased to 0.51. In the subset of cases in which osteonecrosis was diagnosed or suspected, radiologic-pathologic correlation decreased as osteoarthritis grade increased, and the diagnostic uncertainty for both evaluation methods increased. One patient without osteoarthritis had osteonecrosis diagnosed in both hips at radiography and MRI, but osteonecrosis was absent at pathologic examination. CONCLUSION. Radiography depicts osteonecrosis in most patients who have osteonecrosis and subsequently undergo femoral head resection. False-positive and false-negative radiographic findings occur, however. Diagnosis is most difficult in patients with advanced osteoarthritis or subchondral fractures. The number of patients who underwent MRI was not sufficient for evaluation of the accuracy of MRI.

Correlation between groin pain and cup design of hip-resurfacing implants: a prospective study

PURPOSE

Cup design has been incriminated as the source of groin pain after hip resurfacing but has not been well described; thus, it was assessed in a prospective study looking at three implant types.

METHODS

A group-match was done between three groups of hip resurfacing devices according to age, sex, body mass index, activity level, osteoarthritis aetiology and pre-operative scores.

RESULTS

The global groin pain rate was 5.7 % at six months and 2.7 % at last follow-up. Groin pain rate was significantly different between the three groups (p = 0.004) and had a strong influence on the subjective results (p = 0.04). No groin pain emerged between six months and last follow-up. No clinical differences were noted in Harris hip score and Merle d'Aubigné-Postel score at last follow-up. However, the Oxford hip score and Devane activity score were significantly lower for cups with macrostructures.

CONCLUSION

The low groin pain rate in this prospective cohort was probably secondary to the specific surgical technique used and seems to be correlated with cup design. Macrostructures on the external part of the cup could be significantly harmful.

Femoral component positioning in hip resurfacing with and without navigation

Early failures after hip resurfacing often are the result of technical errors in placing the femoral component. We asked whether image-free computer navigation decreased the number of outliers compared with the conventional nonnavigated technique. We retrospectively compared 51 consecutive hip resurfacings performed using image-free computer navigation with 88 consecutive hip resurfacings performed without navigation. Patient demographics were similar. There were no differences in the average native femoral neck-shaft angles, planned stem-shaft angles, or postoperative stem-shaft angles. However, when the postoperative stem-shaft angle was compared with the planned stem-shaft angle, there were 33 patients (38%) in the nonnavigated group with a deviation greater than 5 degrees in contrast to none in the navigated group. Notching was present in four patients in the nonnavigated group and none in the navigated group. The average operative time was 111 minutes for the navigated group and 105 minutes for the nonnavigated group. Image-free navigation decreased the number of patients with potentially undesirable implant placements.

LEVEL OF EVIDENCE

Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.

Is patient selection important for hip resurfacing?

The optimal implant option for hip arthroplasty in the young, active patient remains controversial. There has been renewed interest for metal-on-metal hip resurfacing due to improved design and manufacturing of implants, better materials, enhanced implant fixation, theoretical advantages over conventional total hip arthroplasty, and recent Food and Drug Administration approval of two devices. Recent studies indicate satisfactory short- and midterm clinical results (1- to 10-year followup) with low complication rates, but there is a learning curve associated with this procedure, a more extensive surgical approach is necessary, and long-term results have yet to be determined. Proper patient selection may help avoid complications and improve patient outcomes. Patient selection criteria in the literature appear based predominantly on theoretical considerations without any consensus on stratifying patient risk. The most commonly reported complications encountered with hip resurfacing include femoral neck fracture, acetabular component loosening, metal hypersensitivity, dislocation, and nerve injury. At the time of clinical evaluation, patient age; gender; diagnosis; bone density, quality, and morphology; activity level; leg lengths; renal function; and metal hypersensitivity are important factors when considering a patient for hip resurfacing. Based on our review, we believe the best candidates for hip resurfacing are men under age 65 with osteoarthritis and relatively normal bony morphology.

LEVEL OF EVIDENCE

Level V, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence.