Arthroscopic Management of Avascular Necrosis

In light of observed difficulty with current imaging modalities in the accurate staging of AVN, the authors favor arthroscopic evaluation as an adjunct to traditional imaging modalities. Arthroscopic or direct visualization is required for accurate evaluation and staging, especially in stage IV disease that has proven to have widely variable assessments using the Marcus,¹³ Ficat,³ and Steinberg¹⁴ classification systems.Early and accurate diagnosis is essential to the long-term survival of the joint while minimizing the potential morbidity to the patient. The revision rate of total joint arthroplasty after AVN of the hip has been shown to be higher than that of the normal population.^{40, 41 and 42} It is important to make every attempt to preserve the native femoral head and cartilage. Successful operative treatment of AVN requires that the patient be appropriately staged. Marcus,¹³ Ficat,³ and Steinberg¹⁴ each proposed radiologic classification systems using methods available at the time to optimize patient selection for operative intervention. None of those classification systems use the powerful diagnostic potential of arthroscopy and direct visualization of the femoral head.More accurate staging with arthroscopy may enable more successful application of salvage techniques such as free vascularized fibular grafting (FVFG)²⁰ in mid- to late-stage disease. Current radiographic techniques such as plain radiographs and MRI have shown a reduced ability to accurately assess the condition of the weight-bearing cartilage surface or degree of its collapse. Recent studies by Urbaniak and colleagues,^{23 and 43} showed increased long-term survivability in patients without evidence of collapse at the time of attempted salvage by FVFG. In early reports²⁰ of 103 patients receiving FVFG for AVN of the femoral head, there was a significant difference in the survivability of FVFG in stage IV versus stage V hips. The stage V hips showed a higher survival at 68% versus 57% for stage IV hips. This was attributed to patient bias and a younger patient population. Accurate staging with arthroscopy may have permitted more accurate classification of these patients. Undetected chondral collapse and delamination of the femoral head present at time of grafting in the radiographic stage IV hips could certainly account for variation in results within this group. This reinforces the need for accurate knowledge of the presence and degree of cartilage collapse to appropriately select these patients for the FVFG or one of the other salvage procedures.Hip arthroscopy offers a direct, minimally invasive technique to accurately classify patients with later-stage disease that may or may not benefit from FVFG,²⁰ core decompression with or without grafting,²¹ autologous bone marrow transplantation,²² nonvascularized bone grafting,²⁴ or other resurfacing procedures.⁴⁴ MRI is probably the most useful screening tool for early detection and evaluation of AVN. It is useful in determining the size, quality, and location of the infarct, which may have prognostic value.^{14, 45 and 46} However, several studies have shown the inability of MRI to accurately evaluate the articular cartilage of the femoral head and acetabulum.^{17 and 18} Improvements in MRI and future diagnostic technologies may make arthroscopic evaluation of the articular cartilage unnecessary. Presently, hip arthroscopy using the techniques described earlier can give the surgeon the most accurate assessment tool for proper staging, selection of appropriate patients for advanced salvage procedures, and assist in the management of this difficult condition.