Transient osteoporosis of the hip: long-term outcomes in men and nonpregnant women

Background Transient osteoporosis of the hip (TOH) is a rare disease of unknown etiology, affecting middle-aged men, women in the third trimester of pregnancy, and rarely children, adolescents and nonpregnant women. Presenting symptoms are sudden hip pain and limp, initially with unremarkable radiographs and blood tests. Methods Forty-eight patients (54 hips) with sudden hip pain were examined. All had radiographs, technetium bone scan and MRI. Increased uptake on bone scan and bone edema in the femoral head and neck on MRI were found in all patients. Five patients diagnosed with other disease processes were excluded from the study. The remaining (37 men, 6 nonpregnant women; 49 hips) were diagnosed with TOH. All had repeated clinical and MRI investigations until resolution of symptoms. Twenty-six patients had bone density measurements (DEXA) of both hips and spine. Mean follow-up was 43 months (range, 12-106 months). Results Spontaneous resolution of symptoms occurred in all patients, and all were asymptomatic at final follow-up, although one patient had minor restriction of flexion. Despite the presence of crescent lines on initial MRI in 14 patients, none progressed to osteonecrosis, and crescent lines were not apparent on follow-up MRI. Excellent correlation was found between radiographic bone edema resolution and clinical improvement. DEXA measurements revealed nine men with abnormal bone density despite their relatively young ages. Conclusion TOH is a benign disease, does not progress to osteonecrosis, and should be treated conservatively. Crescent lines may initially appear on MRI only to resolve spontaneously. Other diagnoses should be investigated if pain and bone edema persist.