Osteonectosis, Corticosteroid Use and Crohn’s Disease: Evidence-Based Medicine Versus Civil Law

In 1986, a 22-year-old man brought a malpractice action against his physician because he had developed avascular necrosis of both femoral heads. The physician had prescribed prednisone to control the patient’s Crohn’s disease. Five experts (one in clinical pharmacology, one in orthopedics and three in gastroenterology) testified. The clinical pharmacologist stated that prednisone caused the osteonecrosis, citing the Compendium of Pharmaceuticals and Specialties (1), which lists osteonecrosis as an adverse effect of prednisone use. Three gastroenterologists provided a contrary opinion; they had never encountered nor read any reports concerning a link between prednisone and hip necrosis. Neither side referred to any specific, peer-reviewed study to support their respective positions. All testified based on anecdotal evidence. The judge, on a balance of probability, ruled that prednisone probably did cause the hip necrosis (2). An appeal to the Supreme Court was denied. The court reached its conclusion based on the evidence presented. In general, the obligation of the court is to weigh the evidence and decide on the basis of a balance of probabilities. In the final decision, one position must carry the day. In this case (2), the court preferred the evidence submitted by the plaintiff rather than that of the gastroenterologists. A precedent was set. Subsequent cases (3,4) had similar splits in evidence; orthopedic evidence implicated prednisone as a risk factor for osteonecrosis, while gastroenterological testimony denied such a link. As recently as February 1999, the courts deemed that hip necrosis was caused by the wrongful use of prednisone (5). However, no specific study has ever presented evidence. Based on the earlier, judicially ‘accepted’ and ‘proven’ link between prednisone and hip necrosis, plus one publication that identified prednisone as a risk factor (6), the judge ruled that the hip disease was caused by prednisone, stating that “There is no question in this case that the defendant (physician) was aware that the high level, long term use of prednisone would put a patient at risk of developing avascular necrosis of the major bone”(5). Precedent had been set by the 1988 judgement (2), at least in Canada. In subsequent cases, the expert medical testimony suggesting a possible link between osteonecrosis and prednisone use, plus a history of court rulings on the association, have resulted in courts choosing to not re-evaluate their position. The judicial test is not high (50.1%). Osteonecrosis (aseptic necrosis or avascular necrosis) is characterized by the death of all cellular elements of bone under the cartilage, leading to collapse and fragmentation of the overlying articular cartilage (7). The result is joint degeneration and arthritis. The blood supply to certain bony sites, particularly the femoral head, has a limited collateral circulation. Four mechanisms may be responsible for interrupting this tenuous vascular supply: mechanical disruption from trauma or minor events such as fatigue fractures; thrombosis and embolism from circulating fat or abnormal red blood cells (eg, sickle cell disease); arterial damage from vasculitis or from high pressure within the bone matrix due to excessive packing with fat or cellular elements; and venous occlusion. Once considered an uncommon complication of femoral neck fractures, osteonecrosis is now frequently recognized, accounting for over 10% of total hip replacements.