Objective— To determine the effect of femur positioning and femoral implant placement on the radiographic assessment of total hip femoral implants in dogs.
Study design— Cadaveric study.
Animals— Five canine femurs.
Methods— Five canine femurs were fitted with total hip implants, in predetermined locations, postmortem. Each femur was moved through a defined range of motion and radiographed at specific intervals. Radiographs were then digitized, and implant position was measured using previously described methods. Regression analysis was conducted to determine whether varied femoral position resulted in a consistent (linear) pattern of change in the value of each particular measurement.
Results— Change in the position of the femur relative to the film cassette caused significant variation in the perceived position of the implant. The placement of the implant within the femur determined which measurements were affected and to what degree.
Conclusions— The information obtained from standard clinical radiographs and conventional methods of quantitative analysis does not consistently provide an accurate assessment of the placement of the femoral implant within the femoral canal. Such data cannot be used to correlate implant position with implant failure.