Ambulatory activities maintain cortical bone after total hip arthroplasty.
Because periprosthetic bone loss impacts revision total hip arthroplasties and subsequent patient recovery, it is important to understand the consequences of stress shielding. We characterized bone loss attributed to stress shielding by investigating the influence of patient activity and demographics on reductions in cortical bone cross-sectional area, bone mineral density, and bone mineral content. Cortical bone shape, bone mineral content, and bone mineral density were measured in implanted and contralateral nonimplanted cadaveric femurs. Geometric measurements of transverse cross sections were measured with imaging software. Dual energy x-ray absorptiometry measured bone mineral content and bone mineral density. Patient activity was estimated by the mechanical usage score. The mechanical usage score was comprised of the ambulatory components of the Harris hip score. Regression analysis revealed a lower mechanical usage score and patient weight correlated with greater bone loss. Age, implant size, and time in situ did not correlate to bone loss. The implanted femurs were reduced in cross-sectional area and rigidity, and expanded endosteally and periosteally. Principal axis location did not change. Bone loss was more likely to occur uniformly than to change cortical bone distribution. Bone loss was minimized in patients with higher activity levels.
Rosenbaum
Teri G
TG
Bone and Joint Research Lab (151F), SLC VA Health Care System, 500 Foothill Boulevard, Salt Lake City, UT 84148, USA.
Bloebaum
Roy D
RD
Ashrafi
Shadi
S
Lester
D Kevin
DK
D019644:Arthroplasty, Replacement, Hip; D015519:Bone Density; D005260:Female; D005269:Femur / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D008297:Male; D011184:Postoperative Period; D016138:Walking