Short stem survival after osteonecrosis of the femoral head

Short stems were developed as a bone-conserving alternative especially for the young hip arthroplasty patient. Patients suffering from osteonecrosis of the femoral head are frequently younger than primary arthritis patients. The outcome of short stems in these patients remains unclear. The aim of our study was to compare mid-term survival of short stems after osteonecrosis of the femoral head (ONFH) and primary arthritis.

Data on short stem implantations over a 10-year period were collected. Demographic data and X-ray measurements before and after surgery were recorded. Indication for operation was determined from medical records and X-rays. Patients were asked by post about any revision. Reason for revision was identified by analysis of operation protocols. Short stem revision rates were analyzed using Kaplan-Meier charts, comparing 212 ONFH patients (231 operations) and 1284 primary arthritis patients (1455 operations).

Follow-up time averaged 5.3 and 6 years and was complete for 92% (ONFH) and 94% (primary arthritis) of the patients. ONFH patients were significantly younger (53 years vs. 59 years, p < 0.001) and more frequently male (55 vs. 42%, p < 0.001). The total revision rate did not differ between the two groups (8 years: 4.2 vs. 5.6%, p = ns). A trend towards more stem revisions was detected for ONFH patients (3 vs. 1.8%, p = ns). The aseptic stem loosening rate was significantly elevated for osteonecrosis patients (8 years: 2.6 vs. 0.7%, p = 0.013).

Our study showed elevated short stem loosening rates after ONFH. Similar results are published for classic cementless stems. The question of which stem is best for the young osteonecrosis patient cannot be answered yet. Consecutive studies directly comparing loosening rates of short and classic cementless stems in young osteonecrosis patients are required.