Total hip arthroplasty is one of the most successful and cost effective procedures in orthopedics. The purpose of this study is to investigate force transmission through the sacroiliac joint as a possible source of post-operative pain after total hip arthroplasty through the following three questions: Does the ipsilateral sacroiliac joint, contralateral sacroiliac joint, or pubic symphysis experience more force during placement? Does the larger mallet used to seat the implant generate a higher force? Does the specimen's bone density or BMI alter force transmission?Methods:
A solid design acetabular component was impacted into five human cadaver pelves with intact soft tissues. The pressure at both sacroiliac joints and the pubic symphysis was measured during cup placement. This same procedure was replicated using an existing pelvis finite element model to use for comparison.Findings:
The location of the peak force for each hammer strike was found to be specimen specific. The finite model results indicated the ipsilateral sacroiliac joint had the highest pressure and strain followed by the pubic symphysis over the course of the full simulation. The heft of the mallet and bone mineral density did not predict force values or locations. The largest median force was generated in extremely obese specimens.Interpretation:
Contrary to previous ideas, it is highly unlikely that forces experienced at the pelvic joints are large enough to contribute post-operative pain during impaction of an acetabular component. These results indicate more force is conveyed to the pubic symphysis compared to the sacroiliac joints.