3D-printed peek exo-endoprosthesis for limb salvage in dogs and cats.

Exo-endoprostheses are gradually gaining popularity in veterinary medicine. This study reports the clinical evolution of four patients -one feline and three canines- treated with a novel exo-endoprosthesis system. In all cases, distal limb amputation was performed due to various pathologies -type IIB open fracture, grade 1 chondrosarcoma, ectrodactyly and traumatic partial amputation-, followed by implantation of a custom-designed endomedullary component inserted into the residual bone during same surgical procedure. The interval before exoprosthesis attachment ranged from 2 to 5 months postoperatively, depending on patient-specific factors such as epithelial down-growth or external limitations. Different exoprosthesis designs and versions were developed and 3D-printed according to anatomical region of amputation. Surgical technique, postoperative outcome, limb function, and radiographic findings were described for each case. Upon initial attachment, all animals readily accepted exoprosthesis, with no instances of implant failure or fracture during use. Osseous growth with this inner part was consistent and robust across cases. Surgeries were free of intraoperative complications and postoperative pain. However, long-term use was limited by instability at exo-endoprosthesis interface, which prevented consistent weight-bearing and definitive prosthesis adoption. Postoperative complications included excessive skin overgrowth in patients 2 and 4, and delayed healing in patient 3. Key issues were suboptimal postoperative care and delays in iterative exoprosthesis adjustments. Clinical progress of this system was discussed and compared with analogous designs in human medicine. Internal part implantation of exo-endoprosthesis to distal limb of small animals is feasible and can result in favourable functional outcomes if dermal integration issue can be adequately addressed.