Stable fixation of an osseointegated implant system for above-the-knee amputees

Abstract

Background and purpose Rehabilitation of patients with transfemoral amputations is particularly difficult due to problems in using standard socket prostheses. We wanted to assess long-term fixation of the osseointegrated implant system (OPRA) using radiostereometric analysis (RSA) and periprosthetic bone remodeling.Methods 51 patients with transfemoral amputations (55 implants) were enrolled in an RSA study. RSA and plain radiographs were scheduled at 6 months and at 1, 2, 5, 7, and 10 years after surgery. RSA films were analyzed using UmRSA software. Plain radiographs were graded for bone resorption, cancellization, cortical thinning, and trabecular streaming or buttressing in specifically defined zones around the implant.Results At 5 years, the median (SE) migration of the implant was –0.02 (0.06) mm distally. The rotational movement was 0.42 (0.32) degrees around the longitudinal axis. There was no statistically significant difference in median rotation or migration at any follow-up time. Cancellization of the cortex (plain radiographic grading) appeared in at least 1 zone in over half of the patients at 2 years. However, the prevalence of cancellization had decreased by the 5-year follow-up.Interpretation The RSA analysis for the OPRA system indicated stable fixation of the implant. The periprosthetic bone remodeling showed similarities with changes seen around uncemented hip stems. The OPRA system is a new and promising approach for addressing the challenges faced by patients with transfemoral amputations.

New method of fixation of in-bone implanted prosthesis

“…This effect, called stress shielding, increases the porosity of the cortical bone that hosts the implant, relative to the ipsilateral bone [15]. The outcomes of stress shielding are reduction in hosting bone strength [16–17] and cortical thinning in the distal zones, which increases with time [18]. The weaking and thinning increase the risk of failure, especially among young patients who are involved in more active locomotion [19–20].…”

Two‐stage implantation of the skin‐ and bone‐integrated pylon seeded with autologous fibroblasts induced into osteoblast differentiation for direct skeletal attachment of limb prostheses

“…The duration of the postoperative period was less than one year and that did not allow for evaluation of the dynamics of the hosting bone thinning observed in 57 . The authors plan to address these limitations in their future work.…”

Clinical outcome of osseointegrated prostheses for lower extremity amputations

“…Nebergall et al 23 evaluated proximal-distal migration of the OPRA prosthesis with radio stereometric analysis (RSA) and found this to be 0.17 mm on average. Rotation of the prosthesis around the longitudinal axis was on average 0.38 degrees.…”

“…15,17,18 Loosening occurred in 2--6% of patients. 15,18,20,23 Between 8--67% of patients required at least one more surgical procedure after the initial two-staged implantation of the prosthesis. 14--17,21,24,25 Explant of the prosthesis had to be performed in 3--20% of patients.…”