Complex angular and torsional deformities (distal femoral malunions) Preoperative planning using stereolithography and surgical correction with locking plate fixation in four dogs

Objective: To describe the surgical technique of complex distal femoral deformity correction with the aid of stereolithography apparatus (SLA) biomodels, stabilized with locking plate fixation. Methods: Full-size replica epoxy bone biomodels of the affected femurs (4 dogs/5 limbs) were used as templates for surgical planning. A rehearsal procedure was performed on the biomodels aided by a guide wire technique and stabilized with locking plate fixation. Surgery performed in all dogs was guided by the rehearsal procedure. All pre-contoured implants were subsequently used in the definitive surgical procedure with minimal modification. Results: All dogs had markedly improved, with near normal functional outcomes; all but one had a mild persistent lameness at the final in-hospital follow-up examination (mean: 54.4 weeks; range: 24-113 weeks after surgery). All femurs healed without complications (mean: 34 weeks, median: 12 weeks; range: 8-12 weeks for closing osteotomies, and 26-113 weeks for opening wedge osteotomies). Long-term follow-up examination (mean: 28.6 months; range: 5-42 months) revealed all but one owner to be highly satisfied with the outcome. Complications were observed in two dogs: prolonged tibiotarsal joint decreased flexion that resolved with physical therapy. In one of these dogs, iatrogenic transection of the long digital extensor tendon was repaired, and the other had a peroneal nerve neurapraxia. Clinical significance: Stereolithography apparatus biomodels and rehearsal surgery simplified the definitive surgical corrections of complex femoral malunions and resulted in good functional outcomes.