Patient specific, synthetic, partial unipolar resurfacing of a large talar osteochondritis dissecans lesion in a dog.

Objective: To describe the application and early outcome of a custom-made unipolar partial tarsal replacement in a dog with an extensive medial talar ridge OCD.

Animal: A 7-month-old, 25 kg male Rhodesian Ridgeback with progressive left hindlimb lameness (grade III-IV/IV) and diagnosis of talar OCD.

Methods: The dog presented with progressive lameness attributed to extensive medial talar ridge OCD. Due to the severity of the lesion, a resurfacing procedure was chosen. Based on CT data, a bi-layered resurfacing implant consisting of a titanium socket and a polycarbonate urethane bearing surface was constructed. For intraoperative guidance, a set of matching drill guides were 3D-printed, along with some models of the affected talus, to allow for dry-lab training. Surgical implantation using a medial malleolar osteotomy to approach the lesion was without complications. Orthopedic follow-up examinations were conducted at 10 days, 4 weeks, 6 weeks, 6 months and 12 months. Radiographic examinations were included at the 6-week, 6-month, and 12-month follow-ups.

Results: Function improved considerably during the follow-up period with a lameness grade of 0-I/IV at the 12-month follow-up. ROM differed by 15° in flexion compared to the contralateral side, while there was no difference in extension. Moderate periarticular fibrosis was present at 12 months. Implant positioning was unchanged at follow-up-radiographic examination and there was only mild progression of osteoarthritis (OA).

Conclusion: Patient specific instrumentation - guided tarsal OCD resurfacing with a synthetic patient-specific implant may be an effective treatment option.