Ambulatory activities maintain cortical bone after total hip arthroplasty

Area of Science:

• Orthopedics
• Biomechanical Engineering
• Bone Physiology

Background:

• Periprosthetic bone loss, a complication of revision total hip arthroplasty (THA), affects patient recovery.
• Stress shielding, caused by load redistribution away from the bone by the implant, is a primary driver of this bone loss.

Purpose of the Study:

• To investigate the influence of patient activity and demographics on bone loss attributed to stress shielding.
• To characterize reductions in cortical bone cross-sectional area, bone mineral density (BMD), and bone mineral content (BMC) in response to stress shielding.

Main Methods:

• Cortical bone shape, BMC, and BMD were measured in implanted and contralateral nonimplanted cadaveric femurs.
• Geometric measurements were performed using imaging software, and BMC/BMD were assessed via dual-energy x-ray absorptiometry.
• Patient activity was quantified using a mechanical usage score derived from the Harris hip score.

Main Results:

• Lower mechanical usage scores and patient weight correlated significantly with greater periprosthetic bone loss.
• Age, implant size, and duration of implant in situ did not show a correlation with bone loss.
• Implanted femurs exhibited reduced cross-sectional area and rigidity, with uniform bone loss rather than altered distribution.

Conclusions:

• Higher patient activity levels, indicated by a higher mechanical usage score, minimize stress shielding-induced bone loss.
• Understanding the relationship between activity and bone loss is crucial for managing revision THA outcomes and improving patient recovery.