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Diagnosis, treatment multifactorial for osteonecrosis of the adult femoral head
Chief Medical Editor Douglas W. Jackson, MD, asks Brian J. McGrory, MD, 4 Questions about this troubling and hard-to-diagnose condition.
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Early osteonecrosis of the adult femoral head can be an elusive problem to diagnose. It should be considered in the differential diagnosis of nontraumatic presentations of groin pain and in those patients with increased risk factors. But most us without a subspecialty interest in the hip see this problem infrequently in our clinical practices.
In the 4 Questions interview this month, I asked Brian J. McGrory, MD, to sort through the major issues. He provides an excellent and very practical update.
Douglas W. Jackson, MD
Chief Medical Editor
Douglas W. Jackson, MD: What are commonly thought to be the causes and etiologic factors that result in osteonecrosis of the femoral head (ONFH) in adults?
Brian J. McGrory, MD: There are many direct and associated factors that can predispose a patient to ONFH. Established traumatic etiologies include hip dislocation and femoral neck fracture (although ONFH does not occur in all cases.) Direct nontraumatic causes include radiation and dysbaric osteonecrosis (Caisson disease). The most common nontraumatic associated risk factors are alcoholism and high-dose corticosteroid use (greater than 2 g of prednisone or its equivalent in 2 to 3 months). Coagulation disorders, genetic polymorphisms (variations in the human genome) and many chronic diseases also fall into the category of nontraumatic risk factors, but are less commonly diagnosed. A reported 20% of cases of ONFH appear to be idiopathic in origin with no associated risk factors.
Jackson: How do you evaluate femoral head osteonecrosis to arrive at the desired treatment?
McGrory: The early stages of ONFH are not visible on radiographs. A thorough physical examination and the judicious use of magnetic resonance imaging (MRI), however, can help identify the initial onset of ONFH. Young patients presenting with atraumatic groin pain and a history of one or more of the aforementioned risk factors should be considered carefully for the onset of ONFH. Most experts believe that early diagnosis is vital if the patient is to benefit from conservative treatment. It should be noted that ONFH might be found bilaterally in up to 80% of patients. Therefore, both hips should be carefully examined.
Images: McGrory BJ |
Standard anteroposterior and frog (Lowenstein) lateral radiographs should be obtained as part of a patient’s work-up. It may be difficult to delineate very small areas of ONFH on plain radiographs; however, the presence of the so-called ‘crescent sign’ (caused by the discrepancy in densities of the femoral head due to subchondral bone collapse) is the hallmark of ONFH (Figure 1, page 5). Earlier stages may also present with radiographic sclerosis. The size of the lesion should be noted. When ONFH is suspected but not obvious on plain radiographs, MRI should be obtained. Typical findings include a crescentic signal change with a well- defined and distinct border. MRI should also be considered to evaluate the contralateral hip of patients with known ONFH on one side.
There have been a number of classification systems developed for ONFH, but the Steinberg Classification is considered to be one of the most useful. This classification grades the severity and extent of the involvement, both of which are thought to affect prognosis. The Steinberg stage, presence or lack of symptoms, and patient age may be used to define appropriate treatment.
Jackson: What are the common treatments? Is there a role for core decompression and/or grafting for these patients?
McGrory: Current ONFH treatment recommendations are controversial. Both nonsurgical and surgical treatment options have been used with differing levels of success. Nonsurgical treatment is often advocated for small, asymptomatic precollapse lesions, or for patients who cannot tolerate a surgical procedure. American Association of Hip and Knee Surgeons (AAHKS) physicians rarely offered statins (3% of those surveyed), anticoagualants (6%) or biphosphonates (10%) to treat or prevent ONFH.
Surgical interventions for ONFH either attempt to preserve the femoral head (in the early stages) or replace or resurface the proximal femur or hip joint (in the late stage disease). Temporizing techniques are used for intermediate disease. Core decompression (Figures 2a and 2b) has mixed results but in a meta-analysis study, Castro and Barrack showed that the success of core decompression was significantly higher than nonsurgical management of early stage disease. AAHKS surgeons commonly choose core decompression for symptomatic Steinberg stage IB and IIB disease (prior to crescent sign visibility). Some surgeons also offer this approach for asymptomatic early stage disease when lesions are of moderate or large size.
Bone grafting can be used in conjunction with core decompression or as a treatment option in its own right. Both vascularized and nonvascularized fibula grafts have been employed, but surgeons now tend to prefer vascularized grafts. Encouraging results have been obtained in select patient groups and surgeons offer this procedure to younger patients with earlier stage disease. Vascularized bone grafting is a resource intensive procedure and is preformed at relatively few centers in the United States. Osteotomies and hip arthrodesis are less commonly offered by hip surgeons but may be useful in very specific patient populations. These procedures are offered more commonly in later stage disease than decompression or bone grafting.
Jackson: What type of arthroplasty is offered and when?
McGrory: Total hip arthroplasty (THA) remains the treatment of choice among US hip and knee surgeons for Steinberg stage IIIB and more advanced ONFH, when pain, stiffness, and disability cannot be controlled by nonsurgical means. Traditional and resurfacing hemiarthroplasty and resurfacing total hip replacement are not offered as frequently and appear to have less reliable results than THA. There is, however, a recent enthusiasm among some investigators who anticipate that with improvements in techniques and biomaterials, that the results of resurfacing options will be better.
Studies with long-term follow-up have unfortunately shown less positive results for the outcome of THA when performed for ONFH compared with osteoarthritis patients. Surgical treatment options continue to evolve and more contemporary biomaterials and techniques will hopefully improve results and thus make THA in patients with advanced ONFH more acceptable, even for younger patients.
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In a core decompression: Note the high entry of the drill to avoid cortical bone stress riser, and minimize risk of postoperative fracture (2a). A postoperative radiograph shows results (2b). | |
For more information:
- Brian McGrory, MD, Chair, Evidence Based Medicine Committee, American Association of Hip and Knee Surgeons, can be reached at Orthopaedic Associates of Portland, 33 Sewall St., Portland, ME 04104; 207-828-2100; e-mail: mjri@yahoo.com.
Reference:
- Castro FPJ, Barrack RL. Core decompression and conservative treatment for avascular necrosis of the femoral head: a meta-analysis. Am J Orthop. 2000;29-3:187-194.