An animal model to evaluate skin–implant–bone integration and gait with a prosthesis directly attached to the residual limb

Abstract

Background Despite the number of advantages of bone-anchored prostheses, their use in patients is limited due to the lack of complete skin-implant integration. The objective of the present study was to develop an animal model that would permit both detailed investigations of gait with a bone-anchored limb prosthesis and histological analysis of the skin-implant-bone interface after physiological loading of the implant during standing and walking. Methods Full-body mechanics of walking in two cats was recorded and analyzed before and after implantation of a percutaneous porous titanium pylon into the right tibia and attachment of a prosthesis. The rehabilitation procedures included initial limb casting, progressively increasing loading of implant, and standing and locomotor training. Detailed histological analysis of bone and skin ingrowth into implant was performed at the end of the study. Findings The two animals adopted the bone-anchored prosthesis for standing and locomotion, although loads on the prosthetic limb during walking decreased by 22% and 62%, respectively, 4 months after implantation. The animals shifted body weight to the contralateral side and increased propulsion forces by the contralateral hindlimb. Histological analysis of the limb implants demonstrated bone and skin ingrowth. Interpretation The developed animal model to study prosthetic gait and tissue integration with the implant demonstrated that porous titanium implants may permit bone and skin integration and prosthetic gait with a prosthesis. Future studies with this model will help optimize the implant and prosthesis properties.

Kinetics of individual limbs during level and slope walking with a unilateral transtibial bone-anchored prosthesis in the cat

“…Full descriptions of the surgical and rehabilitative procedures, prosthesis and implant design, and data acquisition have been published previously (Farrell et al, 2014a) and only briefly described here. All experimental procedures were in agreement with the US Public Health Service Policy on Humane Care and Use of Laboratory Animals and were approved by the Institutional Animal Care and Use Committees at both Georgia Institute of Technology and St. Joseph’s Translational Research Institute (now known as T3 Labs).…”

“…The subjects were four adult purpose-bred cats (baseline mass range 3.0–3.2 kg, Table 1) from our ongoing translational study on integration of the titanium porous Skin- and Bone-Integrated Pylon (SBIP; Poly-Orth International; Sharon MA, USA) with the residual limb (Farrell et al, 2014a; Jarrell et al, 2016, 2017). The cats were trained (~2 h a day, 5 days a week for 3–4 weeks) to walk along an enclosed walkway with 3 embedded force platforms (Bertec Corporation, Columbus OH, USA).…”

“…The SBIP material specification has a uniquely selected combination of four critical parameters: particle size, pore size, porosity and volume fraction (Pitkin and Raykhtsaum, 2012). This allows for deep ingrowth of the hosting tissues of bone and skin in combination with implant durability and resistance to fatigue (Farrell et al, 2014a,b; Pitkin et al, 2009). …”

“…For example, ongoing animal studies on transcutaneous porous titanium bone implants (Farrell et al, 2014a,b; Fitzpatrick et al, 2011; Pitkin et al, 2009; Shelton et al, 2011) have aimed to reduce skin infection in individuals with bone-anchored lower limb prostheses (Branemark et al, 2014; Drygas et al, 2008; Tillander et al, 2010; Tsikandylakis et al, 2014), and ultimately to improve biomechanics of prosthetic locomotion. It is much less common, however, to translate successful developments in human biomechanics, orthopedic and prosthetic research to veterinary medicine to treat animals with limb loss.…”

“…Although few case report studies have suggested that quadrupedal animals might utilize a unilateral distal bone-anchored prosthesis for walking (Farrell et al, 2014a; Fitzpatrick et al, 2011), no studies have been published that rigorously document whether quadrupedal animals systematically utilize unilateral transtibial prostheses during locomotion and how prosthetic locomotion is performed. The use of the prosthetic limb during quadrupedal locomotion might depend on which limb is missing (forelimb versus hindlimb) and on loading demands on the prosthetic limb.…”