The patient’s history, physical, and imaging were consistent with a diagnosis of osteonecrosis of the right femoral head with an atypical pain presentation. The patient’s major risk factor for osteonecrosis of the hip was the prior use of steroids. Sclerosis of the femoral head without subchondral collapse on plain films, along with marrow edema on MRI, was consistent with Ficat/Steinberg stage II osteonecrosis.

Early diagnosis of osteonecrosis of the femoral head is important to improve treatment outcomes. Patients most commonly present with deep groin pain or ipsilateral buttock pain. The patients often complain of a constant dull aching in the hip that may increase in intensity with activity or ambulation. On physical examination, range of motion may be variable. Patients may present with normal range of motion or with minimal loss of internal rotation secondary to inflammation of the joint. These findings suggest that the hip has not collapsed. A significant loss of internal rotation suggests collapse of the femoral head. A definitive diagnosis of osteonecrosis is usually made with MRI. On plain radiographs sclerosis of the femoral head is suggestive of osteonecrosis. Radiographic progression of the disease usually involves the presence of a crescent sign or frank collapse of the femoral head. The frog lateral view is the optimal view to determine the presence of a crescent sign or collapse of the femoral head. Over time the femoral head may flatten, and finally the joint space narrows and advanced degenerative changes develop. MRI is highly sensitive and specific for diagnosing osteonecrosis. T1-weighted images demonstrate a low signal intensity region representing the necrotic area. The corresponding T2-weighted images show high signal intensity because the osteonecrotic region may be surrounded by bone marrow edema. In a hip that has not collapsed, the prognosis is determined by the extent of involvement of the weight-bearing surface of the femoral head and the overall involvement of the femoral head, which can be estimated on the MRI.

Treatment of osteonecrosis of the femoral head is dependent on the severity at the time of diagnosis. Nonsurgical management has a very limited role, except in the follow-up of small and asymptomatic lesions. Biophysical and pharmacologic treatments including extracorporeal shock wave and bisphosphonates may have some role in osteonecrosis prior to collapse, although strong evidence is lacking. In a randomized controlled trial evaluating zoledronate, a bisphosphonate, patients were randomized to receive 5 mg of zoledronate or a placebo annually. The rate of total hip arthroplasty in the zoledronate group was 19 of 55 patients (35%) and in the control group was 20 of 55 (36%) at 2-year follow-up. Further randomized studies are still needed to determine if pharmacologic treatment is beneficial in early-stage disease (pre-collapse hip).

Surgical management is dependent on whether collapse of the femoral head has occurred. Prior to femoral head collapse, core decompression has been shown to be a successful treatment option. Core decompression may be performed in a number of different ways including a core tract alone, multiple small core tracts, or core decompression with bone grafting with a nonvascularized or vascularized graft or local bone grafting. Nonvascularized grafts include concentrated stem cells, demineralized bone matrix, fibular allograft, tibial allograft, and bone morphogenetic protein. Vascularized grafts are typically done with the fibula, but iliac crest grafts have also been utilized. Vascularized bone grafting, which provides both structural support and osteogenic bone graft, has also shown good long-term outcomes in patients with early-stage disease without femoral head collapse. Although these grafts have shown promise, randomized controlled trials are needed to determine if true benefits exist.

Tantalum rod insertion after decompression has not been compared in randomized trials to core decompression alone, and prospective studies have shown poor results with failure rates as high as 15% at 1 year. Tantalum rods are thought to promote bone ingrowth; however, a histopathologic analysis found that on explant of tantalum rods after 1 year, there was minimal bone ingrowth in the osteonecrotic region. A randomized controlled trial compared patients who received core decompression and tantalum rod insertion. The intervention group received a tantalum rod and targeted intra-arterial peripheral blood stem cells treated with granulocyte colony-stimulating factor (G-CSF). There were lower rates of conversion to total hip arthroplasty at the 3-year follow-up in the combination therapy group. Finally, prior to femoral head collapse, rotational osteotomies aim to transpose the osteonecrotic area from a weight-bearing to non-weight-bearing surface. Rotational osteotomies can be successful in patients with a combined necrotic angle <200° and with careful planning. However, these are technically difficult procedures. No randomized studies have been performed evaluating rotational osteotomies, and more evidence is needed to determine efficacy. Once femoral head collapse is present, or in patients with large osteonecrotic lesions, hip resurfacing arthroplasty and total hip arthroplasty are the two available treatments. Advantages of hip resurfacing arthroplasty are preservation of femoral bone stock, low dislocation rate, and rapid recovery from surgery. Disadvantages include a lack of modularity compared to THA, risk of periprosthetic fracture, and increased metal ion levels. Total hip arthroplasty is the most reliable treatment to achieve pain relief and function. Multiple studies with long-term follow-up have found high implant survival rates as well as high functional outcome scores.

This 29-year-old gentleman with bilateral femoral head osteonecrosis is now 30 months status post right hip core decompression with concentrated stem cells. He is doing well and has no pain in his groin or buttock. There is still some sclerosis in his right femoral head, but no evidence of collapse (Fig. 8.3).

Although numerous risk factors for osteonecrosis of the femoral head have been identified, including corticosteroid use, alcohol, trauma, and hypercoagulable states, the etiology of the disease is still unclear (Table 8.1) [2]. Ischemia of the femoral head through vascular disruption, constriction, or thrombosis and direct cellular toxicity likely play a role, although neither completely explains the pathogenesis of the disease [3]. A multifactorial process is certainly at play, and although risk factors have been identified, these also cannot predict who will develop the disease [4]. Surgical management is generally the recommended treatment, although nonoperative management has been studied. Bisphosphonates have been assessed as a possible treatment to prevent femoral head collapse. The hypothesis for the use of bisphosphonates is that by inhibiting osteoclast activity, and thereby blocking bone resorption, more bone formation may occur, which theoretically creates structural support in the weakened necrotic area. Chen et al. performed a multicenter randomized controlled trial comparing 65 hips (52 patients) with pre-collapse (45 hips) as well as subchondral collapse (20 hips) osteonecrosis [5]. Patients were randomized to receive either 70 mg oral alendronate or placebo weekly for 104 weeks. At 2-year follow-up, 4 (12.5%) hips in the alendronate group and 5 (15.2%) hips in the placebo group underwent THA. Lai et al. also evaluated alendronate in a randomized controlled trial of patients with pre-collapse (30 hips) and subchondral collapse (24 hips) osteonecrosis [6]. Patients were randomized to receive either 70 mg oral alendronate (29 hips) or placebo (25 hips) weekly for 25 weeks. At 2-year follow-up, one hip (3.4%) in the alendronate group and 16 hips (65%) in the control group had undergone THA (P < 0.001). Lee et al. performed a prospective randomized study (110 patients) to assess the efficacy of zoledronate for the management of medium to large osteonecrotic areas (>30%) without femoral head collapse [7]. Patients received either intravenous zoledronate (55 patients) or placebo (55 patients) and were followed for 2 years. The rate of total hip arthroplasty in the zoledronate group was 19 of 55 patients (35%) and in the control group was 20 of 55 (36%) at 2-year follow-up (P = 0.796). Zoledronate alone was also not effective in reducing the rate of collapse (P = 0.251).

Enoxaparin is another pharmacologic agent that has been investigated and is thought to improve blood flow to the femoral head. Glueck et al. prospectively compared 25 hips in 16 patients with thrombophilic disorders and pre-collapse femoral head osteonecrosis [8]. Nineteen of 20 hips with primary osteonecrosis did not progress radiographically at 2-year follow-up. These results suggest a potential role for etiologic-based treatment modalities. Appropriately powered randomized trials need to be performed to assess the efficacy of pharmacologic treatment alone or in combination with core decompression with bone grafting.

Core decompression is the most widely used surgical treatment to manage osteonecrosis of the femoral head without collapse and has shown promising results. A systematic review by Marker et al. found that in the last two decades 70% of patients treated with core decompression did not require additional surgery [9]. Core decompression is often supplemented with bone graft, stem cells, or biologic adjuvants to provide structural support of the osteonecrotic lesion and to promote bone formation and repair. However, this treatment regimen has not been rigorously assessed in multicenter randomized trials. Israelite et al. performed core decompression with bone grafting in 276 hips (193 patients) with a minimum 2-year follow-up [10]. In this retrospective study, the authors found that 104 hips (38%) required THA and that in patients with pre-collapse disease and small lesions, only 14% required THA. Lieberman et al. evaluated 17 hips (15 patients) treated with core decompression and the allogeneic, antigen-extracted, autolyzed cortical bone from fibular allografts combined with human bone morphogenetic protein and noncollagenous proteins. At an average follow-up of 53 months, they found that 14 hips (86%) did not have radiographic progression of osteonecrosis or conversion to THA [11]. Hernigou et al. reviewed 189 hips (116 patients) with early-stage disease treated with core decompression and autologous iliac crest bone marrow grafting [12]. The authors found that at 5-year follow-up, the total hip arthroplasty rate was 6% in patients without femoral head collapse, compared to 57% in those with femoral head collapse. In patients with early-stage disease, 103 of 136 hips (76%) did not have radiographic progression of disease, and Harris hip scores rose 17 points postoperatively. Although augmentation of core decompression with osteogenic graft or adjuvants has shown promising results, no randomized trials have been performed and are needed to determine efficacy. Lieberman et al. also recently performed a systematic review looking at operative treatment of femoral head osteonecrosis [13]. The size of the osteonecrotic lesion was found to be an important predictor of failure, and the authors found failure rates ranging from 14% to 25% after core decompression with or without grafting in patients with small lesions. Additionally, the failure rate dropped to 4.5% in cases with lesions occupying <30% of the medial weight-bearing surface. Randomized trials are needed to determine the optimal method for core decompression and whether or not biologic adjuvants improve the results.

Vascularized bone grafting can also be combined with core decompression with long-term hip survival rates between 60% and 89%, depending on the size of the necrotic region [14, 15]. Plakseychuk et al. compared vascularized to nonvascularized fibular autograft in 220 hips and found a 7-year survival rate in early-stage disease of 86% in the vascularized cohort compared to 30% in the nonvascularized group [16]. Yoo et al. reported on 14-year survival in 124 hips and found only 11% underwent total hip arthroplasty [14]. Vascularized fibular grafting has also been studied in the femoral heads that have collapsed without signs of arthrosis. Berend et al. reviewed 188 patients (224 hips) with an average follow-up of 5 years and found a conversion to total hip arthroplasty of 35% [17]. Although these results seem promising, vascularized fibular grafting is technically demanding due to the required microsurgery and is also associated with donor-site morbidity. Randomized trials are needed to determine if vascularized fibular grafts are superior to core decompression.