Tim Sparrow, Noel Fitzpatrick, J Wesmania, G. Blunn
Introduction: Partial resurfacing of the humeral head has been reported in humans to treat humeral osteochondritis dissecans. The aim is to describe a custom-made humeral resurfacing prosthesis for treatment of severe humeral head osteochondritis disse-cans in a dog. Case report: A seven-month-old female entire St. Bernard dog was presented with a 10 week history of severe left thoracic limb lameness. Radiography, arthroscopy and magnetic resonance imaging confirmed an extensive osteochondritis dissecans lesion affecting the caudal, medial and central regions of the humeral head. A prosthesis designed from computed tomography (CT) images was manufactured in polished stainless steel alloy with a hydroxyapatite coated base and central finned humeral stem for cementless insertion. A standard caudal approach to the shoulder was used to place the prosthesis following reaming of the caudal humeral head. Results: Radiography and CT imaging revealed appropriate topographical placement on the humerus. Force plate analysis demonstrated initial reduction in ground reaction force at six weeks, followed by gradual improvement at three months. There was no radiographic evidence of implant loosening and the range of shoulder joint motion was comparable to the contralateral joint at three months; these findings were maintained to final follow-up at 24 months. Clinical significance: Placement of a humeral head resurfacing prosthesis was an effective technique for the management of severe osteochondritis dissecans-related shoulder lameness. To the authors’ knowledge, this is the first report of the clinical use of shoulder hemiarthroplasty in a dog.