Introduction: 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.
Materials and methods: 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.
Results: 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.
Conclusion: We recommend at least two firm, axially aligned blows to impact the femoral head onto the trunnion intra-operatively.