Risk factors for loosening of cementless threaded femoral implants in canine total hip arthroplasty

Abstract

To determine the incidence and potential risk factors of femoral implant loosening in the canine Helica® total hip replacement (THR) system. Sixteen dogs with a Helica THR were included. Medical records were reviewed for signalment and size of implants. Stem angle, stem collar to lateral cortex distance, tip to cortex distance, stem collar to lateral cortex distance at a stem angle of 150°, lever arm distance, and the distance on the diaphysis measurements were calculated from the one year postoperative radiographs. Three ratios were determined from these measurements to take into account the size of the femur in relation to the size of the implant. Femoral implant loosening was identified by radiographic and clinical signs, and confirmed at the time of surgical explantation. Differences in the successful and femoral stem failure groups were compared using either a students t-test or a Mann Whitney test. Significance was set at p <0.003. Six of the 16 dogs had loosening of the femoral prostheses within one year post-implantation. One dog had evidence of a septic cause for loosening. No significant risk factors could be identified in this group of dogs with Helica stem loosening. Helica femoral stem loosening was a common complication within one year post-implantation in this group of dogs. No risk factors were identified to potentially decrease the incidence of loosening. Therefore, due to this unacceptably high complication rate, the authors do not recommend this model of the Helica THR.