Radiographic Evaluation of Early Periprosthetic Femoral Bone Contrast and Prosthetic Stem Alignment after Uncemented and Cemented Total Hip Replacement in Dogs

Objective: To radiographically evaluate periprosthetic femoral bone contrast and assess alignment of the prosthetic stem after uncemented and cemented total hip replacement (THR). Study Design: Prospective clinical study. Animals: Dogs (n = 15). Methods: Dogs were classified into uncemented (n = 8) and cemented (n = 7) THR groups. Radiographs were analyzed using image processing software to evaluate femoral bone contrast (gray scale value, GV) for each and combined modified Gruen zone(s) immediately and 4 months after THR. Modified Gruen zones were classified into 5 zones to analyze retrospectively the regional radiographic GV of the femur around uncemented and cemented prosthetic stem. Alignment of prosthetic stem was assessed immediately and 4 months postoperatively. Variables were compared by use of 2-tailed t-test, with P <.05 considered significant. Results: Zone 1 showed significant decrease in the mean bone GV 4 months after uncemented THR. No differences in zones 1-5 after 4 months of cemented THR. Combined zones showed significant decrease in overall mean bone GV 4 months after uncemented THR. No changes were observed 4 months after cemented THR. Number of limbs with varus-aligned femoral stem markedly increased after 4 months of uncemented THR. Conclusions: Regional bone contrast and prosthetic stem alignment vary with the design of THR. © 2011 by The American College of Veterinary Surgeons.