The Journal of Bone and Joint Surgery

Image Quiz

Part 2: Treatment Alternatives for Osteonecrosis of the Femoral Head
(continued)

Fig. 1-a

Fig. 1-b

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Figures 1-a and 1-b show a preoperative plain radiograph and a T1-weighted magnetic resonance imaging scan of a small to medium-sized lesion, which would be appropriately treated with core decompression. In Figure 1-a (the plain radiograph), the femoral head appears normal, without evidence of collapse. However, Figure 1-b (the MRI) reveals a small osteonecrotic lesion (with < 30% involvement of the femoral head) and also confirms the absence of subchondral collapse.

Fig. 2
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Bone-Grafting: Bone-grafting, with either vascularized or nonvascularized grafts, is indicated for large lesions (those with a combined necrotic angle of ³ 200˚ on plain radiographs and > 30% involvement of the femoral head on magnetic resonance imaging scans). It is also indicated when early collapse has occurred (indicated by a head depression of < 2 mm) in the presence of intact femoral head cartilage. The combined necrotic angle is derived by measuring the sector of involvement on both anteroposterior and lateral plain radiographs of the femoral head and adding these two angles together¹. (Fig. 2).