Percutaneous osseointegrated prostheses for amputees: Limb compensation in a 12-month ovine model

Abstract

Percutaneous osseointegrated prostheses are being investigated as an alternative strategy to attach prosthetic limbs to patients. Although the use of these implants has shown to be promising in clinical trials, the ability to maintain a skin seal around an osseointegrated implant interface is a major challenge to prevent superficial and deep periprosthetic infections. The specific aim of this study was to establish a translational load-bearing ovine model to assess postoperative limb compensation and gait symmetry following a percutaneous osseointegrated implant. We tested the following hypotheses: (1) the animals would return to pre-amputation limb loads within 12-months; (2) the animals would return to a symmetrical gait pattern (stride length and time in stance) within 12-months. The results demonstrated that one month following surgery, the sheep loaded their amputated limb to a mean value of nearly 80% of their pre-amputation loading condition; by 12-months, this mean had dropped to approximately 74%. There was no statistical differences between the symmetry of the amputated forelimb and the contralateral forelimb at any time point for the animals stride length or the time spent in the stance phase of their gait cycle. Thus, the data showed that while the animals maintained symmetric gait patterns, they did not return to full weight-bearing after 12-months. The results of this study showed that a large animal load-bearing model had a symmetric gait and was weight bearing for up to 12 months. While the current investigation utilizes an ovine model, the data show that osseointegrated implant technology with postoperative follow-up can help our human patients return to symmetric gait and maintain an active lifestyle, leading to an improvement in their quality of life following amputation.

Figure 1

Photograph of the percutaneous, osseointegrated implant used in the study showing the bone implant region, ribbed region, porous coated region, titanium adapter, and exoprosthesis.

Figure 2

(Left) Photograph of a sheep standing on the pressure mat within the enclosure. (Right) Output of the pressure sensing mat showing the Right Hindlimb (RH), Left Hindlimb (LH), Right Forelimb (RF), and Left Forelimb (LF).

Figure 3

Percent of preoperative PVF Distribution for the right (amputated) forelimb showing the amputated limb was loaded less after surgery for all time points, obtaining a value nearly 74% of the preamputation value.

Figure 4

Percent of preoperative PVF Distribution for the left forelimb, left hindlimb, and right hindlimb at 12-months postop, demonstrating that the three untreated limbs had a higher PVF Distribution following surgery to compensate for the decreased load on the right forelimb.