The role of hip arthroscopy in the evaluation of avascular necrosis

This prospective study evaluated the correlation between plain radiographs, magnetic resonance imaging (MRI), and diagnostic arthroscopy in the stagin g of avascular necrosis of the femoral head. Fifty-two hips in 46 patients were prospectively staged using radiographic and MRI staging systems. Patie nts subsequently underwent hip arthroscopy to visualize the articular surfa ce prior to considering salvage of the femoral head and debride delaminated osteochondral fragments. Weighted Kappa analysis revealed only moderate co rrelation between MRI and plain radiographs (k=.11), MRI and arthroscopy (k =.21), and plain radiographs and arthroscopy (k=.19). Six (46%) of 13 patie nts with a radiographically apparent subchondral fracture demonstrated coll apse of the articular surface at arthroscopy. Four (24%) of 17 hips with >2 mm of collapse of the femoral head on plain radiographs demonstrated fragm entation of the osteochondral surface of the femoral head at arthroscopy. I n 5 patients with flattening of the femoral head, 3 patients had delaminati on of both the femoral and acetabular surfaces. In regard to labral patholo gy, 5 of 22 post-collapse hips also had large bucket handle tears of the la brum. Arthroscopy of the hip revealed osteochondral degeneration that was n ot detected by plain radiographs or MRI in 36% of post-collapse femoral hea ds.