Mid-term results of short versus conventional cementless femoral stems in patients with bilateral osteonecrosis of the femoral head.

Background: This study aimed to compare the clinical and radiographic mid-term results between short and conventional stems.

Methods: Patients with bilateral osteonecrosis of the femoral head (ONFH) who had undergone bilateral staged THAs using short stem in one hip and conventional stem in the contralateral hip were included. The Harris Hip Score (HHS), thigh pain, patient's joint perception (PJP) and patients' preferred hip were recorded. Using x-ray, osseointegration and stress shielding were analyzed and compared between stems.

Results: There were 35 cases (70 hips) with the mean age of 46.3 years (25-63), and the mean follow-up was 75.1 months (60-108). HHS was significantly improved in both short and conventional groups (p < 0.001). There was mild thigh pain in 2 cases (5.7%) of the short stem group and 6 cases (17.1%) of the conventional group. With regard to the PJP, we found slightly more natural joint feeling in the short stem group. Of the patients' preferred hip, 11 cases (31.4%) preferred short stem hip and 6 cases (17.1%) preferred conventional stem hip. The short stem group showed osseointegration mainly in the proximal part. The conventional stem group showed osseointegration mainly in the distal part. We found stress shielding grade 1 in 31 cases (88.6%) and grade 2 in 3 cases (8.6%) in the conventional stem group, whereas only grade 1 in 34 cases (97.1%) in the short stem group.

Conclusions: The clinical results were promising in both short and conventional stems; however, short stem showed less thigh pain, slightly more natural joint feeling (PJP) and more patients' preferred hip. The short stem provided more favorable results for proximal load transfer and slightly less stress shielding.