Anti-rotation pins for the compress implant do not increase risk of mechanical failure or impair osseointegration

Background: The use of compliant fixation for endoprosthetic implants is gaining popularity. Previous work has shown that anti-rotation pins improve rotational stability at the bone-implant interface, but there is concern that these pins lead to increased risk of mechanical failure. We asked: (I) are anti-rotation pins used with the Compress implant associated with mechanical failure? (II) Are anti-rotation pins associated with less effective osseointegration? Methods: We performed retrospective review of cases using a Compress implant from 2004-2016. Mechanical failure rates and bone growth at the bone-implant interface were compared between pin and no-pin cohorts. Regression models were used to examine patient and surgical factors associated with mechanical failure. Results: Anti-rotation pins were not associated with mechanical failure (P=1.0, odds ratio 1.17, 95% confidence interval: 0.12-15.40). Anti-rotation pins were not associated with impaired osseointegration at any time point (P=1.0 at 3-6 months, P=0.33 at 6-9 months, P=0.34 at 9-12 months, P=0.40 at 12-24 months, P=0.28 at 24-48 months, P=1.0 at >48 months). No patient or surgical variables were predictors of mechanical failure. Conclusions: Anti-rotation pins were not associated with mechanical failure or impaired osseointegration.