Loading conditions during femoral preparation for THA procedures: Mechanical effects of broach holder offset.

BACKGROUND: The objective of this study was to compare the cumulative loading needed to seat the planned stem size between straight and offset broach handles. We hypothesized that the cumulative loading is higher when using the offset broach handle, whose force vector is not truly in the axis of the recipient femoral shaft. Thus, the increased stresses applied to the femur intraoperatively could contribute to increased risk of perioperative fracture.

METHODS: For each broach insertion and for each of our 20 femurs specimens, the mean force, maximum force and cumulative force were recorded. The number of strikes was also collected. Thus, the primary outcomes were the cumulative force, mean force, maximum force and the number of strikes made by the surgeon until the planned broach size was fully seated. A subgroup analysis was done based on the morphology of the intramedullary canal (Dorr classification). An inter-rater analysis was also done to remove the surgeon effect on the femoral preparation.

RESULTS: Using an offset broach handle required significantly more strikes to insert the broaches into the femurs until the planned size was seated (p = 0.049). No significant differences were observed between the two broach handle types in the maximum force, mean force, or cumulative force.

CONCLUSION: This biomechanics study showed that use of an offset broach handle requires significantly more strikes and repeated impacts than use of a more conventional straight broach handle. While there was no significant difference in terms of forces applied between the two strategies, if the surgeon wants to have the same operating time for both techniques, he/she will be required to apply larger forces at each strike to achieve the same advancement of the broach in the femur.

REGISTRATION: Authorization of the Minister of Education and Research No. DC-2008-137.