Impact magnitudes applied by surgeons and their importance when applying the femoral head onto the Morse taper for total hip arthroplasty

This study was designed to test whether the number of impacts, the experience of the surgeon or impact force made significant difference in pull off forces. The forces applied by 10 orthopaedic surgeons (five residents and five attending staff) to impact the femoral head onto the trunnion of a femoral component were recorded. The resultant forces were then divided into four energy levels and compared to determine if the number of impacts would make a difference in pull off strength. No significant differences existed between the resident versus attending groups in magnitude of force applied. Through ANOVA testing, it was found that at each of the energy levels, multiple blows demonstrated a significant pull off strength difference compared to a single blow. Increased pull off force was also noted when the magnitude of force of the applied blows was increased. We recommend at least two firm, axially aligned blows to impact the femoral head onto the trunnion intra-operatively.