Development of a Percutaneous Prosthesis for Transfemoral Amputees, the Utah Experience

Skin breakdown, infections, discomfort from scarring or heterotopic bone, and frequent adjustments due to residual limb volume changes limit the success of socket suspension technology for transfemoral (TF) amputees. These challenges prohibit many amputees from comfortably wearing their prosthesis or from being able to perform many activities. European and Australian programs have been implanting percutaneous osseointegrated (OI) devices in amputees for over two decades as an alternative means of artificial limb suspension that maintain a secure connection without the complications associated with socket technology. Reported risks of OI implants include mechanical failure, aseptic loosening and infection rates of 30-55% [1]. No OI device has received full Premarket Approval by the FDA for clinical use within the United States. For the past ten years our research team has performed preclinical tests to design a new OI device, the Percutaneous Osseointegrated Prosthesis (POP), aiming to limit infection and provide a mechanically stable implant that allows for rapid return to ambulation [2]. The FDA approved an Early Feasibility Study (EFS) of the POP device that is currently being conducted. DJO Surgical is the device manufacturer of record.

METHODS:This study was IRB and FDA approved. Ten TF amputees underwent a two-stage surgery protocol: Stage 1 surgeries to implant an endoprosthetic stem within the residual bone, and Stage 2 to attach a percutaneous post to the stem after a minimum of 5 weeks.  Participants completed bone, skin, function and psychological assessments at 5, 12, 24, 36 and 52 weeks after Stage 2 surgery.

RESULTS: Ten male amputees, mean age = 48.7 (min 32; max 67) and mean time since amputation of 10.5 years (min 1.5; max 19), received the POP device. Implants were successfully placed with no intraoperative fractures or other surgical complications. All patients were successfully fitted with their prosthetic limb within 24 hours of Stage 2 surgery and were able to immediately load the limb as tolerated under supervision. All progressed to ambulation with an assisted device within 14 days of Stage 2 with no post-operative fractures.

A reduction in the average prosthesis don and doff times of 91.4% and 70.8%, respectively, was observed at 5 weeks. 80% progressed to independent ambulation by the 5-week follow-up. Two device removals occurred: one early loosening at 5 weeks and the other due to a periprosthetic fracture following trauma at 7 months. One perioperative and two superficial infections (9 & 10 months) were resolved with antibiotic treatments. 70% have completed the 12-month follow-up period to date. 

Clinical results to-date have demonstrated low preliminary infection rates, maintenance of distal cortical bone, improved functional outcomes, periprosthetic bone density increases, and improved patient reported outcomes following a staged operative approach and accelerated weight-bearing compared to other existing OI techniques. The remaining patient completes 1-year follow-up in April 2018.

1. Branemark R, et al. A novel osseointegrated percutaneous prosthetic system for the treatment of patients with transfemoral amputation. Bone Joint J 2014;96-B:106-13
2. Jeyapalina S, et al. Cortical bone response to the presence of load-bearing percutaneous osseointegrated prostheses. Anat Rec (Hoboken) 2012;295:1437-45.