R hip had nontraumatic symptomatic osteonecrosis and we monitored them prospectively. The minimum followup was 5 years (mean, 8.3 years; range, 5-16 years). At the latest followup, 31 hips (38%) were symptomatic and 26 hips (32%) had collapsed. The mean interval between diagnosis and collapse was 4.1 years. We observed no correlation between femoral head collapse and patients' age, gender, weight, presumed cause of osteonecrosis, or length of followup. With combined factors, only extent of large necrotic lesion (hazard ratio, 4.06; 95% confidence interval, 1.29-12.77) and location of Type C2 necrotic lesion (hazard ratio, 6.35; 95% confidence interval, 1.18-34.11) predicted collapse. Level of Evidence: Level I, prognostic study. See the Guidelines for Authors for a complete description of levels of evidence....

Retard the collapse. We conducted a two-year prospective, randomized, open-label, multicenter study to determine whether zoledronate prevents the collapse and reduces the need for total hip arthroplasty. Methods: We randomly assigned patients who had Steinberg stage-I or II nontraumatic osteonecrosis of the femoral head with a necrotic area of ≥30% to either the zoledronate group or the control group. Patients in the zoledronate group received 5 mg of zoledronate intravenously per year for two years, while patients in the control group did not receive this medication. The primary efficacy outcome was the survival rate in terms of the occurrence of collapse (≥2 mm). The patients were observed for a minimum of two years after enrollment. Results: A total of 110 patients (110 hips) underwent randomization; fifty-five patients were assigned to the zoledronate group and fifty-five, to the control group. During the two-year follow-up, twenty-nine femoral heads in the zoledronate group and twenty-two in the control group collapsed (p > 0.05). Nineteen hips in the zoledronate group and twenty in the control group underwent total hip arthroplasty (p > 0.05). Conclusions: Zoledronate for Steinberg stage-I or II osteonecrosis of the femoral head, with a medium to large necrotic area, did not prevent the collapse of the femoral head or reduce the need for total hip arthroplasty. Level of Evidence: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence....

The reported incidence of avascular necrosis after femoral neck fracture fixation varies widely, and there is no consensus regarding its risk factors. We evaluated the incidence of avascular necrosis of the femoral head with the use of contemporary techniques for femoral neck fracture fixation. We then sought to determine what potential risk factors influenced the development of avascular necrosis. Between 1990 and 2005, one hundred sixty-three intracapsular femoral neck fractures in 163 patients were treated with internal fixation at our level-I trauma center. All patients were monitored until conversion to total hip arthroplasty or for a minimum of 2 years postoperatively. Ten patients (10 hips) died and 7 patients (7 hips) were lost to follow-up. The remaining 146 patients (146 hips) had a mean 5.2 years of follow-up (range, 3 months to 17 years). The incidence of avascular necrosis was 25.3% (37 hips). The average time to diagnosis of avascular necrosis was 18.8 months (range, 3–47 months). Patient sex, age, interval from injury to surgery, and mechanism of injury were statistically not associated with the development of avascular necrosis. The quality of fracture reduction, adequacy of fixation, degree of displacement, and comminution of the posterior cortex were significantly associated. After we controlled for patient and radiographic characteristics, multivariate analyses indicated that the important predictors for avascular necrosis are poor reduction (odds ratio=13.889) and initial displacement of the fracture (odds ratio=4.693).

Min BW, et al. Hip Pelvis. 2016 Mar;28(1):15-23. http://dx.doi.org/10.5371/hp.2016.28.1.15

Lee KJ, et al. Clin Orthop Surg. 2009 Sep;1(3):155-160. http://dx.doi.org/10.4055/cios.2009.1.3.155