Patient specific implants for amputation prostheses: Design, manufacture and analysis

Abstract

<jats:title>Summary</jats:title><jats:p>Objectives: To design, manufacture and analyze custom implants with functional gradation in macrostructure for attachment of amputation prostheses.</jats:p><jats:p>Methods: The external shape of the implant was designed by extracting geometrical data of canine cadavers from computed tomography (CT) scans to suit the bone cavity. Three generations of implant designs were developed and were optimized with the help of fit/fill and mechanical performance of implant-cadaver bone assembly using CT analysis and compression testing, respectively. A final optimized, custom Ti6Al4V alloy amputation implant, with approximately 25% porosity in the proximal region and approximaltely zero percent porosity in the distal region, was fabricated using Laser Engineered Net Shaping (LENS™) – a laser based additive manufacturing technology.</jats:p><jats:p>Results: The proposed design changes in the second generation designs, in terms of refining thresholds, increased the average fill of the bone cavity from 58% to 83%. Addition of a flange between the stem and the head in the second generation designs resulted in more than a seven-fold increase in the compressive load carrying capacity of the assembly. Application of LENS™ in the fabrication of present custom fit Ti6Al4V alloy implants enabled incorporation of 20 to 30% porosity in the proximal region and one to two percent residual porosity in the distal portion of the implant.</jats:p><jats:p>Clinical significance: Patient specific prostheses having direct connection to the skeletal structure can potentially aid in problems related to load transfer and proprioception in amputees. Furthermore, application of LENS™ in the fabrication of custom implants can be faster to incorporate site specific porosity and gradients for improving long-term stability.</jats:p>

Design features of implants for direct skeletal attachment of limb prostheses

“…It has been shown that the roughness of the metal surface increases cell apposition . Microroughened and nanosurface superimposed featured implants improved osteogenesis and the inflammatory/immune responses …”

Clinical outcome and complications of thoracic and pelvic limb stump and socket prostheses

“…These techniques are not limited to neoplasia management (13)(14)(15). Potential reported advantages of osseointegrated implants include improved comfort, no delay in load transfer, improved proprioception, and avoidance of stump socket interface problems that are commonly encountered in stump socket prostheses (15,16). However complications including fracture, infection, skin breakdown, and aseptic loosening are all reported.…”

Test of Designing and Manufacturing a Polyether Ether Ketone Endoprosthesis for Canine Extremities by 3D Printing

“…Due to its insertion in the medullary cavity of long bones, all the disadvantages of a socket prosthesis are avoided. Besides, better proprioception, no delay in load transfer, comfort, and energetic efficiency all have been described (Fitzpatrick et al, 2011;DeVasConCellos et al, 2012;Pitkin, 2013;Phillips et al, 2017). Exo-endoprosthesis complications have been reported, such as device failure, aseptic loss, marsupialization or skin breakdown, avulsion, and infection (Drygas et al, 2008;Fitzpatrick et al, 2011;DeVasConCellos et al, 2012;Golachowski et al, 2019).…”

“…Besides, better proprioception, no delay in load transfer, comfort, and energetic efficiency all have been described (Fitzpatrick et al, 2011;DeVasConCellos et al, 2012;Pitkin, 2013;Phillips et al, 2017). Exo-endoprosthesis complications have been reported, such as device failure, aseptic loss, marsupialization or skin breakdown, avulsion, and infection (Drygas et al, 2008;Fitzpatrick et al, 2011;DeVasConCellos et al, 2012;Golachowski et al, 2019). There are published clinical reports for exo-endoprosthesis for different animal species (Drygas et al, 2008;Fitzpatrick et al, 2011;Golachowski et al, 2019) or experimental models (Hall, 1976;Pitkin, 2013;Farrell et al, 2014).…”

“…All of the reported animal exo-endoprostheses used different metal alloys as the main material (Drygas et al, 2008;Fitzpatrick et al, 2011;DeVasConCellos et al, 2012;Farrell et al, 2014;Golachowski et al, 2019). Two of these are fabricated by additive manufacturing for metal materials using direct metal laser sintering technology (DMLS) (DeVasConCellos et al, 2012;Golachowski et al, 2019).…”