Comparison of cortical and cancellous bone remodeling of the pelvis after press-fit cup total hip arthroplasty dependent on patient and prosthesis-specific characteristics: a computed tomography-assisted osteodensitometry study in vivo

Abstract

Even though periprosthetic bone loss is common after total hip arthroplasty, there is no scientific evidence whether it compromises the survival of the prosthesis. Using quantitative computed tomography-assisted osteodensitometry, we determined the pattern of periacetabular bone density (BD) changes of two different press-fit cups (54 hips) 10 days, 1 year and 3 years post-operatively. We measured cortical and cancellous BD at three points of time and evaluated the effects of patient-specific characteristics [age, gender, body mass index (BMI)], clinical function, and BD at index operation. Cancellous BD decreased in all periacetabular regions by up to -52% (p≤0.001). In contrast, cortical BD above the dome of the cup remained constant while at the level of the cup it decreased by up to -17% (p≤0.001). Older patients had significantly lower cortical (ventral and dorsal) and cancellous (cranial) BD values, obese patients had a higher cortical BD ventral, and patients with excellent clinical results had a higher cancellous BD ventral and dorsal to the cup. Changes in BD suggest high stress shielding of retroacetabular cancellous bone, while load is transmitted to cortical bone above the dome of the cup. Patient-specific characteristics were shown to affect BD, but long-term analysis is needed to show whether these effects are of clinical importance.