Osteonecrosis and Bone Marrow Edema Syndrome

Osteonecrosis (ON) of the hip, also called avascular necrosis (AVN) and transient osteoporosis of the hip (TOH), and bone marrow edema syndrome (BMES) are causes of hip pain in middle-aged patients who show evidence of bone marrow edema. Although some literature has suggested that BMES may be a reversible form of ON rather than a disease entity of its own, no definitive documentation is available to support this theory. The current general consensus is that BMES is a unique disease entity. In fact, a recent study of 155 BMES hips demonstrated no progression to ON in any of the patients after 1- to 10-year follow-up. In contrast to ON, BMES is a transient, but painful, condition of the hip that is limited to marrow changes without associated joint space narrowing and arthritic changes. Because of the low incidence of BMES, few reports have described large series, making it difficult to further elucidate the pathophysiology of this disease. It was originally defined by Curtiss and Kincaid in 1959 as a syndrome of transient demineralization of the hip in the third trimester of pregnancy. It has since been found to occur more frequently in young and middle-aged men. In contrast to the extremely low incidence of BMES, ON is a more common condition that has existed for millennia; evidence of the disease has been found in Egyptian mummies. ON is defined by compromise of bone blood circulation that leads to ischemic death of subchondral bone in the femoral head. The hallmark that separates these two entities is that most patients who are diagnosed with ON progress to advanced stages of the disease with femoral head collapse and painful arthritis that require total hip arthroplasty (THA) in contrast to the usual self-limited nature of BMES ( Fig. 33.1 ).

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This macro-photomicrograph of a hip specimen demonstrates the subchondral fracture that corresponds with the “crescent sign” seen on radiographs in advanced-stage osteonecrosis. Patients who reach this stage of disease invariably require reconstructive total joint surgery. Because this degree of joint destruction does not occur in patients who have bone marrow edema syndrome, it is important that surgeons are able to distinguish these disease entities and provide appropriate treatment.

Differentiation of ON and BMES is complicated by various terms that have been used to describe these two diseases. Ultimately, it is important for orthopaedic surgeons to understand this terminology so that they can properly use the current literature in their diagnoses, decision-making, and surgical management. Some of the descriptions that have been used are based on the underlying pathogenesis or the clinical nature of the disease, but others are outdated and are no longer commonly used. Lequesne and associates were the first to characterize the syndrome of transient demineralization of the hip as transient osteoporosis. The usefulness of transient osteoporosis of the hip as a clinical term supplanted use of the original terminology of transient demineralization of the hip . In general, many investigators consider BMES and transient osteoporosis of the hip as the same disease. Because of its similarity to other transient clinical entities at other sites in the body, it is now included in the umbrella of diseases commonly referred to as bone marrow edema syndromes . In cases of bone marrow edema characterized by concurrent or subsequent involvement of additional anatomic sites other than the primary hip, the overall syndrome may be referred to as regional migratory osteoporosis. Although it remains unclear whether regional migratory osteoporosis is the same entity as is seen in cases of isolated BMES that have no other sites of involvement, many clinician experts consider regional migratory osteoporosis to be a variant of BMES.

Other authors initially postulated that BMES was a form of reflex sympathetic dystrophy (now called complex regional pain syndrome, type 2 ), but this theory has largely fallen out of favor. Also, as previously noted, some authors have proposed that BMES may be a nonprogressive, reversible form of ON. Regardless of the proposed pathophysiology, BMES remains the most commonly used term to describe this disease. In the case of ON, the terminology has been less variable. Initially, avascular necrosis was commonly used. This term was an accurate descriptor of this disease for cases with a known traumatic origin in which the vascular supply to the femoral head was directly compromised. However, this terminology was deemed inaccurate in its use when describing lesions in individuals who had associated risk factors such as corticosteroid use, systemic lupus erythematosus (SLE), or Gaucher disease, in which bone marrow displacement and increased compartment pressure were considered to be the likely pathogenetic mechanisms. Osteonecrosis has subsequently become the preferred term. Although ON can be grouped with other diseases that cause bone marrow edema, it is typically studied as a distinct entity.

Part of the difficulty in differentiating ON from BMES may be that patients with these diseases can present with seemingly nonspecific groin pain and equivocal findings on physical and radiologic examination. Nevertheless, some progress has been made in understanding the underlying origins of these conditions and in examining the outcomes of various surgical and nonsurgical treatments. The present work will serve as a review of current knowledge about these conditions to assist clinicians in their management. This chapter begins by discussing the differences in epidemiology, risk factors, and pathophysiology, as well as clinical and diagnostic features that can be used to distinguish these two diseases, while providing some of the arguments that have been put forth against this taxonomy. The second part of the chapter reviews various treatment options available for each condition and provides a discussion of their rationale and indications, along with a summary of results obtained when various techniques were used.