For a successful total hip arthroplasty (THA) it is essential that components are properly sized and positioned within the patient. This project’s focus was to develop a m ore efficient way for determ ining sizing, positioning and range of m otion for Encore M edical’s m odular hip com ponents for a THA. The ultimate goal was to replicate each individual patient’s anatomy to make THA more accurate and efficient w ith hopes of extending the average life of a hip replacement. To do this, an algorithm was developed to be used once acetabular and stem components were implanted. Upon the digitization of specific points on these components the algorithm predicted optimal neck length, neck angle, index position/anteversion o f the femoral neck components and the resulting range of motion.

Validation tests using ideal inputs proved that the algorithm accurately predicted component sizing and range of m otion given ideal inputs. For further validation, a sim ulation of the hip joint was created using a sawbone pelvis and a series o f tracks that sim ulated three degrees of motion:​ flexion/extension, adduction/abduction, and internal/external rotation. Several tests were run using different sizes and orientations of Encore’s modular hip components. Predictions for neck length, neck angle, index position/anteversion, and range of motion were compared to the know n component sizes and values recorded using the tracks.

Results for predicting neck length, neck angle and index position/anteversion yielded standard deviations ranging from 0.10-1.20 mm, 1.82-6.27 degrees, and 0.62-4.80 degrees, respectively. Range of motion results generated a greater range o f variability with standard deviation for the m easured values ranging from 1.01-16.25 degrees, and calculated ranging from 0.96-11.94 degrees. Encore’s components were sized with only 3mm difference between the lengths, 4mm difference between neck angle, and at times only 1 degree of difference in anteversion. It was concluded that the current testing m ethods and m easurem ent devices used did not produce accurate enough results to prove this m ethod reliable for replacing current m ethods used for sizing and positioning in the operating room. It is recom m ended that further testing be done with cadaveric models to fully sim ulate this m ethod during a THA and compare it to the accuracy of current methods being used.