Femoral Neck Fracture with Misdiagnosis of Osteonecrosis of the Femoral Head: A Two-Case Report.

We report two rare cases of femoral neck fracture resulting from osteonecrosis of the femoral head (ONFH) that was undiagnosed at the patients' initial visits. The patient in the first case had sequential bilateral displaced femoral neck fractures. Because no osteonecrosis of the femoral head was visible on X-ray film and the data of liver function tests were normal, ONFH was not diagnosed. In addition, because the patient was a 55-year-old man with normal everyday functioning, closed reduction with cannulated screws was performed at both visits. Nine months later, he came to our outpatient department with bilateral hip pain; X-rays revealed nonunion and implant failure at both hips. The patient subsequently underwent bilateral total hip arthroplasty (THA) and had a satisfactory outcome at his 4-year follow-up. The patient in the second case had a left displaced femoral neck fracture after trivial trauma two months prior. ONFH was not diagnosed upon examination of X-ray findings. The patient was 52 years old with liver cirrhosis and had bipolar hemiarthroplasty performed because of a chronic displaced fracture and poor general condition. After 2 years, she began to have right hip pain. X-rays revealed massive necrosis and sclerosis of the femoral head. Computed tomography scans for ONFH staging revealed impending fracture lines at the subcapital site of the patient's previous left femoral neck fracture. Right THA was then performed, and the outcome was satisfactory.