by Harlan C. Amstutz, M.D.

Introduction

Surgical Technique

Discussion

Conclusions

References

Introduction

The treatment of osteonecrosis of the femoral head remains a challenging problem because of youth, bilateral involvement and often systemic illness with persistence of the underlying disease or risk factors. The treatment options for Ficat Stage I and II osteonecrosis (Ficat and Arlet 1980) include conservative management, core decompression and bone grafting. Once segmental collapse has occurred (Ficat Stage III) the results with core decompression have been poor either with (Boettcher et al. 1970, Bonfiglio and Voke 1968, Dunn and Grow 1974, Phemister 1949) or without (Tooke et al. 1988) bone grafting. Intertrochanteric osteotomies, especially with large necrotic lesions, have produced variable results (Ganz and Buchler 1983, Scher and Jakim 1993, Wagner and Zeiler 1981). Although Sugioka (1984, 1992) has reported success with the transtrochanteric rotational osteotomy, others have not reported equivalent outcomes (Eyb and Kotz 1987, Tooke et al. 1987, Grigoris et al. 1996). The results of these procedures, at best, are variable and inconsistent. Experience is limited with free vascularized fibular grafting (Fujimaki and Yamauchi 1983, Yoo et al. 1992) and the results are more variable once collapse has occurred (Urbaniak JR et al. 1995). Once the necrosis has progressed to Stage IV, good results after any of the above options become even less predictable.

The durability of total hip arthroplasty for patients with osteonecrosis has been less satisfactory than in other diagnostic groups. Moreover, in young and active patients any prosthetic replacement is unlikely to equal the longevity of the patient and revision surgery will be necessary. The failure rates have consistently been higher than with other etiologies using cemented systems and cementless prosthesis have been associated with high incidence of thigh pain and fibrous fixation and more recently high incidence of osteolysis due to particulate debris.

The initiation of our precision-fit surface hemiarthroplasty experience began in 1980 because we were disappointed with results of full surface replacement (THARIES) as well as total hip replacement in young patients with osteonecrosis. Because the acetabulum is relatively normal in stage III osteonecrosis, the concept of hemiarthroplasty is appealing in order to defer total hip arthroplasty. Conventional stemmed hemiarthroplasty may fulfill this goal, but this procedure resects the femoral head and part of the neck and violates the femoral canal, and revision may be completed by removing the stem whereas precision fit surface hemiarthroplasty maximizes tissue conservation. By preserving proximal femoral bone, and optimizes cartilage durability by optimizing contact of the hemispherical bearing to the acetabular cartilage and facilitates revision surgery.

The original technique included the machining of three custom made components in 1 mm increments to allow for flexibility in sizing at surgery. The components were made of titanium alloy with inner diameters corresponding to the existing THARIES so that instrumentation could be utilized (Amstutz et al. 1977).