Current concepts on osteonecrosis of the femoral head

Abstract

It is estimated that 20000 to 30000 new patients are diagnosed with osteonecrosis annually accounting for approximately 10% of the 250000 total hip arthroplasties done annually in the United States. The lack of level 1 evidence in the literature makes it difficult to identify optimal treatment protocols to manage patients with pre-collapse avascular necrosis of the femoral head, and early intervention prior to collapse is critical to successful outcomes in joint preserving procedures. There have been a variety of traumatic and atraumatic factors that have been identified as risk factors for osteonecrosis, but the etiology and pathogenesis still remains unclear. Current osteonecrosis diagnosis is dependent upon plain anteroposterior and frog-leg lateral radiographs of the hip, followed by magnetic resonance imaging (MRI). Generally, the first radiographic changes seen by radiograph will be cystic and sclerotic changes in the femoral head. Although the diagnosis may be made by radiograph, plain radiographs are generally insufficient for early diagnosis, therefore MRI is considered the most accurate benchmark. Treatment options include pharmacologic agents such as bisphosphonates and statins, biophysical treatments, as well as joint-preserving and joint-replacing surgeries. the surgical treatment of osteonecrosis of the femoral head can be divided into two major branches: femoral head sparing procedures (FHSP) and femoral head replacement procedures (FHRP). In general, FHSP are indicated at pre-collapse stages with minimal symptoms whereas FHRP are preferred at post-collapse symptomatic stages. It is difficult to know whether any treatment modality changes the natural history of core decompression since the true natural history of core decompression has not been delineated.

Keywords: Conservative treatment; Core decompression; Femoral head; Osteonecrosis; Stem cells; Total hip arthroplasty.

Figure 1

Mechanisms of osteonecrosis.

Figure 2

Left hip anteriorposterior and cross leg lateral X-rays showing (arrows) the crescent sing.

Figure 3

Bilateral osteonecrosis of the femoral head with flattening of the surface and early sings of osteoarthritis.

Figure 4

Magnetic resonance imaging of the left hip showing extensive avascular necrosis of the femoral head with collapse and a large area of devitalized bone demonstrating fibrocystic change. There is associated severe arthrosis of the left hip joint with a moderate effusion, synovitis and debris and a marked bone marrow edema pattern on both sides of the joint.

Figure 5

Core decompression of the left femoral head. Preoperative magnetic resonance imaging, above (coronal and axial views) and fluoroscopic imaging during the procedure below.

Figure 6

Right femoral head osteonecrosis. Flattening of femoral head progression in 24 mo ending up in a right total hip replacement.

Figure 7

Bilateral total hip replacement in a patient with bilateral hip osteonecrosis of the femoral head.

Figure 8

Algorithm for the management and treatment of patients with osteonecrosis of the femoral head. RF: Risk factors; ONFH: Osteonecrosis of the femoral head; FH: Femoral head; MRI: Magnetic resonance imaging; FHCD: Femoral head core decompression; NVBG: Non vascularized bone graft; BA: Biologic agents; VBG: Vascularized bone graft; OA: Osteoarthritis; THA: Total hip arthroplasty.