Measuring the Impact of Femoral Head Size on Dislocation Rates Following Total Hip Arthroplasty

PURPOSE The purpose of this study was to evaluate if the femoral head's size has an impact on dislocation rates following total hip arthroplasty (THA). MATERIALS AND METHODS Five hundreds forty-three THA performed using a posterolateral approach in our hospital and followed up more than 6 months were included in this study. We evaluated dislocation rates based on the size of femoral head (28 mm vs. over 32 mm) and further investigated the dislocation rates classified into primary and revision surgery. Patient-related and surgical factors were reviewed to evaluate risk factors impacting dislocation rates. RESULTS Dislocation occurred in 9.6% of cases (n=52; 32 males and 20 females). Of this dislocation group, 36 were treated with femoral heads 28 mm in diameter (9.8% of all patients treated with 28 mm femoral heads) and 16 were treated with femoral heads 32 mm and over (9.1% of all patients treated with femoral heads of at least 32 mm). The percentages of patients experiencing dislocation were not significantly different among the two groups (i.e., 28 mm vs. ≥32 mm). However, after revision surgery, the dislocation rate in the 28-mm group was significantly higher than the ≥32-mm group (P<0.05). In a case-control study comparing dislocation and non-dislocation groups, the risk of dislocation was 6 times higher in patients with habitual alcohol intake, and 9.2 times higher in patients with a neuropsychiatric disorder (P<0.05). CONCLUSION Patient factors are considered to have a more significant impact on dislocation rates following THA than the size of femoral head.