Surgical correction of forelimb deformity in a Chihuahua using 3D CT

Abstract

OBJECTIVE: To report the use of three dimensional (3D) computed tomographic (CT) imaging, computer simulation and rapid prototype modelling to aid surgical correction of a complex antebrachial deformity in a dog. METHODS: A six-year-old, 13 kg spayed female Chihuahua crossbreed dog was presented for worsening forelimb gait and exercise intolerance. Both forelimbs had gross angular limb deformity with carpal hyper-flexion, valgus and radial procurvatum. Surgical planning from radiographs was problematic therefore CT data were used to generate 3D reconstructions of the antebrachium. Using imaging software we then quantified the nature of the deformity using a previously unreported method based on the centre of rotation of angulation as a 3D model. Computer simulated closing of the virtual wedge osteotomy was then performed as proof of concept. A stereolithographic model complete with osteotomy axes, was then created in plastic using a rapid prototyping machine. Oscillating saw guides were fabricated in polymethylmethacrylate and cold sterilised. A closing wedge osteotomy with de-rotation was performed and stabilised with a pre-contoured dynamic compression plate. At the three- and six-month follow-up examinations there was improved weight-bearing and cosmetic appearance. CONCLUSIONS: Computer assistance was valuable for locating and quantifying this antebrachial deformity and conceptualising the corrective surgery. The results of our study suggest that rapid prototyping can be used to create models and saw guides to simplify one-stage corrective osteotomies and more accurately treat angular limb deformity.