Radiographic evidence of bone changes around intraosseous transcutaneous amputation prosthesis: an 11-year retrospective cohort study

Introduction - Percutaneous Osseointegrated Implants (POIs) influence the load transfer path to the host bone. In turn, mechano-regulatory processes (strain adaptive bone remodeling) drive periprosthetic bone changes that influence implant stability and fixation outcome. These bone changes have not yet been reported for the Intraosseous Transcutaneous Amputation Prosthesis (ITAP) clinical trial.

Objectives - This study will first standardize the zoning and reporting of periprosthetic bone change in POI radiographs. Second, it will retrospectively measure periprosthetic bone change from radiographs of 12 participants with an ITAP up to 11 years. Finally, the results will be qualitatively compared with those from participants with different POI designs.

Materials and Methods - Twenty participants with unilateral transfemoral amputations received an ITAP in a 2-center UK clinical trial in either 2008/09 or 2013/14. Participant radiographs from one center were available (n = 12) over 11 years and have been collated and processed in a repeatable way. Transverse plane periprosthetic bone change measurements at 3 equidistant points along the implant stem were measured in AP and ML.

Results - Total median bone growth in AP was double that in ML (57.6 mm and 31.12 mm, respectively). Median lateral and posterior bone change (1.44 mm and 1.09 mm) was greater than median medial and anterior (0.83 mm and −0.005 mm) bone changes, respectively. The greatest change in radial bone growth was observed distally and the least proximally.

Conclusions - Bone changes were similar to other collared pressfit POIs in the literature. We demonstrate the influence of stem design and mechano-regulatory remodeling in stable fixation; however, additional influences on periprosthetic bone change were inferred from the results and further investigations are necessary.

Clinical Relevance - To identify ITAP design features and fixations that minimize endosteal resorption, thus promoting implant stability and contributing to clinical guidelines for rehabilitation and future design and fixation choices.