Abstract
INTRODUCTION:
Recent trends in total hip arthroplasty (THA) have resulted in the use of larger acetabular components to achieve larger femoral head sizes to reduce dislocation, and improve range of motion and stability. Such practices can result in significant acetabular bone loss at the time of index THA, increasing risk of anterior/posterior wall compromise, reducing component coverage, component fixation, ingrowth surface and bone stock for future revision surgery. We report here on the effects of increasing acetabular reaming on component coverage and bone loss in a radiographic CT scan based computer model system.
METHODS:
A total of 74 normal cadaveric pelves with nonarthritic hip joints underwent thin slice CT scan followed by upload of these scans into the FDA approved radiographic analysis software. Utilizing this software package, baseline three-dimensional calculations of femoral head size and acetabular size were obtained. The software was used to produce a CT scan based model that would simulate reaming and placement of acetabular components in these pelves that were 125, 133 and 150% the size of the native femoral head. Calculations were made of cross sectional area bone loss from anterior/posterior columns, and loss of component coverage with increasing size.
RESULTS:
Use of acetabular components that were 125, 133 and 150% the size of the native femoral head led to a average loss of 23, 27% and 33% loss of cross-sectional acetabular bone and an average 7, 16 and 27% loss of acetabular component coverage.
CONCLUSION:
The CT scan/computer based model described here demonstrates that acetabular preparation and use of large components simply to gain larger femoral head size can result in significant bone loss and reduced component coverage. Operating hip surgeons attempting to utilize such large components must take great caution when attempting to maximize acetabular component size.
