Cryofibrinogen levels are increased in non-traumatic osteonecrosis: a new pathogenic clue to osteonecrosis?

OBJECTIVE To determine whether levels of cryofibrinogen are increased in non-traumatic osteonecrosis (ON) and could correlate with disease staging. METHODS We prospectively analysed cryofibrinogen levels by immunofixation electrophoresis in 50 patients with non-traumatic ON, 50 healthy volunteers and 8 patients with traumatic ON. Staging of disease involving the femoral heads and the size of necrotic lesions were assessed by the Association Research Circulation Osseous (ARCO) classification system. RESULTS Mean cryofibrinogen levels in patients with non-traumatic ON were significantly increased relative to healthy controls and to patients with traumatic ON (222.1 ± 20.6, 59.9 ± 5.6 and 52.3 ± 14.9 mg/dl, respectively, P < 0.001). In the non-traumatic ON group, mean cryofibrinogen levels were significantly increased in patients with multifocal ON compared with patients with mono/bifocal ON (276.5 ± 56.5 and 149.3 ± 15.4 mg/dl, respectively, P = 0.03). There were no significant differences in cryofibrinogen levels observed with respect to the size of the necrotic lesions involving the femoral heads. Moreover, cryofibrinogen levels in patients with ON of the femoral heads classified according to the stage of disease were not significantly different between patients with stage 1/2 and patients with stage 3 ON (179.2 ± 31.3 vs 204.1 ± 29.0 mg/dl, respectively; P = 0.813). CONCLUSION Cryofibrinogen levels are increased in non-traumatic ON and, more importantly, in multifocal ON. The fact that cryofibrinogen levels are not correlated with the size of lesions and the stage of disease could imply systemic rather than local involvement characterizing the pathogenesis of ON.