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Objectives and questions: Osteonecrosis of the femoral head (OFH) is more common among those who had a history of COVID-19 virus. Considering the young age and high-performance demand, a total hip arthroplasty (THA) with a short femoral stem could be a suitable solution. The aim of this study is to compare subsidence, anterior femoral pain and osteointegration of short and standard femoral stems, in patients diagnosed with OFH.

Material and methods: We have prospectively followed two groups of patients, aged 21 to 65 years, who underwent THA for OFH for minimum 2-year follow-up, with a short or standard cementless femoral stem (case-control ratio 1:3). Patients with previous trauma, infection or metabolic disease were excluded. Clinical and radiographic assessments were scheduled at 45 days, 3 months, 6 months, and annually thereafter. The evaluation included Harris Hip Score, Roles and Maudsley Score, stem subsidence, leg length discrepancy, femoral and acetabular signs of osteointegration and heterotopic ossification. The Mann-Whitney test was used to analyse differences between non-parametric variables. Continuous variables were analysed with Student's t-test and dichotomous variables with Fisher Exact test.

Results: Short stem group (17 hips) and standard stem group (51) were followed for mean 2.2 years, with mean age of 41.8± 8.6 years and 43.2±8.0 years, respectively. All the femoral stems were well osseointegrated at the last follow-up, showing no femoral radiolucency nor periprosthetic osteolysis nor loosening in either groups. Two hips in the control group had a 2 mm subsidence at 3-month follow-up with no clinical symptoms. Leg length discrepancy was 5±3 mm in short stem group and 6±2 mm in standard stem group. Clinically, postoperative Harris Hip Score was 92±3.7 points in the short stem group and 92±3.5 points in the standard stem group. Patient satisfaction was excellent for all the patients, but 4 patients in the control group scored good.

Discussion and conclusions: Using short cementless femoral stem in patients diagnosed with OFH is showing similar results to those receiving the standard stem, at short term follow-up. Further analysis could be possible increasing the follow-up and including more patients.