3D-Printed Dorsal Acetabular Rim Implants: A Game-Changing Treatment for Hip Dysplasia in Dogs?

Abstract

Objective: Canine hip dysplasia (HD) is a common orthopedic disorder characterized by joint laxity leading to secondary osteoarthritis (OA). Existing surgical treatments have limitations, prompting the development of alternative strategies. The acetabular rim extension implant is a novel technique designed to increase femoral head coverage and improve joint stability without pelvic osteotomy, thereby facilitating faster recovery and reducing morbidity. The patient-specific implant is fabricated from titanium using three-dimensional (3D) printing based on preoperative computed tomography (CT). To eliminate the need for preoperative CT, an off-the-shelf (generic shelf) implant was also developed. This thesis comprises three sequential study phases evaluating first-generation patient-specific implant (ACE-X), second-generation patient-specific implant (3DHIP), and generic shelf acetabular rim extension implants. Methods: Client-owned dogs older than six months with clinical and radiographic evidence of HD were included. Patient-specific implants were designed based on preoperative CT in Phase I (ACE-X) and Phase II (3DHIP). In Phase III, the size of generic shelf implant was selected on the preoperative radiograph. Dogs were followed for a minimum of 12 months. Radiographic outcomes were monitored via radiographs and/or CT. Clinical assessments were evaluated during clinical visits or with owner questionnaires. Long-term ACE-X outcomes were assessed via structured owner questionnaires. Results: Phase I included 34 dogs (61 hips) treated with ACE-X. Immediate improvements in hip stability and coverage were observed, with significant reductions in owner-reported pain by 6 weeks, continuing through 12 months. Force plate data showed no significant change. Complications occurred in 14.8% of hips. OA progression continued, with osteophytes increasing by 1.0 ± 1.2 mm at 12 months. Phase II included 25 dogs (50 hips) treated with 3DHIP. Hip stability improved immediately, with subluxation angle decreasing from 16° to −2°, reduction angle from 30° to 2°, and laxity index from 0.6 to 0.4. Median preoperative lead time (41 days) was shorter than for ACE-X (74 days). Osteophyte progression at 12 months (0.8 ± 1.0 mm) was slightly lower than after ACE-X. Clinical scores improved progressively. Force plate values decreased at 6 weeks but returned to baseline by 3–6 months. Complications occurred in 12% of hips. Long-term ACE-X follow-up included 20 dogs; 95% of owners reported satisfaction, and 85% reported absence of lameness. Phase III included 6 dogs (12 hips). Clinical and radiographic outcomes were comparable to patient-specific implants, with effective reduction of hip subluxation and decreased pain scores. However, implant placement deviated from the plan by 5.1 ± 1.7 mm. Complications occurred in one dog (20%). Histology in one unrelated death revealed localized cartilage depletion adjacent to the implant rim. Conclusion: Both patient-specific and off-the-shelf acetabular rim extension implants significantly reduced hip laxity and improved pain-related scores while permitting rapid recovery and single-session bilateral surgery. Complication rates were low for patient-specific implants and moderate for the generic design. Although OA progression persisted, overall clinical outcomes were favorable. The patient-specific implant demonstrates strong translational potential for treating HD in young adults, whereas the generic shelf design requires further refinement before broader application.