EQUINE VETERINARY EDUCATION Equine vet. Educ. (2022) 34 (11) 565 doi: 10.1111/eve.13594_1


Case Report


Accessory carpal bone fracture repair by means of computer- assisted orthopaedic surgery in a Warmblood stallion


M. de Preux†, E. van der Vekens‡, J. Racine†, D. Sangiorgio§, M. D. Klopfenstein Bregger†, H. P. Br€


unisholz† and C. Koch†


†Swiss Institute of Equine Medicine (ISME), Department of Clinical Veterinary Medicine, Vetsuisse-Faculty, University of Bern, and Agroscope, Bern, Switzerland; ‡Division of Clinical Radiology, Department of Clinical Veterinary Medicine, Vetsuisse-Faculty, University of Bern, Bern, Switzerland; and §Pferdeklinik Moosweid, Obfelden, Switzerland *Corresponding author email: christoph.koch@vetsuisse.unibe.ch


Keywords: horse; accessory carpal bone; computer-assistedorthopaedicsurgery; fracture; lag screwrepair;minimally invasive surgery


Summary A 10-year-old, 595 kg Irish Warmblood stallion used for showjumping was presented with a marked right forelimb lameness at walk (Fig 1). The horse sustained a dorsal plane fracture of the accessory carpal bone (ACB) when falling with both carpi in flexion. The fracture was repaired under general anaesthesia by means of computer-assisted orthopaedic surgery (CAOS) using one 4.5 mm and one 3.5 mm cortex screws placed in lag fashion. A mobile cone-beam CT unit (O- arm, Medtronic Navigation) coupled with a surgical navigation system (StealthStationS7, Medtronic Navigation) was used for 3D imaging. Corridors for both cortex screws were planned perpendicular to the fracture line with the navigation software. In a second CAOS procedure performed 6 weeks later, a dorsoproximal fragment of the ACB was removed after further proximal displacement had become apparent. To effectively carry out a CAOS procedure with intraoperative real-time surgical navigation, a fibreglass cast to immobilise the carpus in extension was placed for both surgical procedures. The cast provided an artificial extension of the ACB and allowed the patient tracker to be placed distant from the surgical site whilst still achieving a satisfactory surgical accuracy in implant placement. Furthermore, it protected the fracture from further displacement or comminution during induction and the fracture repair from early failure during the recovery phase of general anaesthesia. One year after surgery, the horse had returned to full athletic activity. Neither the antebrachiocarpal


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Fig 2: Lateromedial projections of the right carpus made one year after the surgery, showing progressive fracture healing (arrows). The main fracture line is only slightly visible on the last control radiograph. Mild osteophyte formation (arrowheads) is present at the dorsal and palmar aspects of the antebrachiocarpal joint.


joint nor the carpal sheath was distended. Control radiographs and standing cone-beam computed tomography showed complete osseous union of the fracture and osteophyte formation on the caudal aspect of the radius and the proximal border of the ACB (Fig 2). This is the first detailed description of a surgical repair of an ACB fracture by means of CAOS in a horse, illustrating how CAOS opens new perspectives for the repair of ACB fractures as it offers so-far unmatched real-time intra- operative orientation and millimetre-scale accuracy for precise drilling through minimally invasive approaches.


Key points


• The capacity for adequate intra-operative image guidance and the degree of fragment displacement are important when considering internal fixation for the surgical repair of dorsal plane ACB fractures.


• CAOS provides adequate surgical accuracy for successful implant insertion in the accessory carpal bone and potentially other small cuboidal bones of the equine carpus and tarsus.


Fig 1: Lateromedial radiograph of the right carpus showing a comminuted fracture (arrowheads) in the dorsal third of the accessory carpal bone, with minimal palmar displacement. An additional thin radiolucent line (arrow) is present in the proximal fourth of the dorsal fragment.


• When using optical tracking systems for computer- assisted surgery involving the ACB, a fibreglass cast that immobilises the carpus in extension allows placing the patient tracker distant from the surgical site while maintaining adequate surgical accuracy.


© 2021 The Authors. Equine Veterinary Education published by John Wiley & Sons Ltd on behalf of EVJ Ltd.


This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.

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