Pilot study on the use of an off-the-shelf 3D-printed titanium acetabular rim extension implant for treating canine hip dysplasia

Hip dysplasia (HD) is one of the most prevalent orthopedic issues in dogs. Generic shelf implants are 3D-printed devices designed to address HD in dogs of varying sizes and hip laxity scores. This pilot study evaluated the feasibility and effectiveness of generic shelf implants in six dogs diagnosed with bilateral HD. Each dog underwent bilateral hip surgery in a single session followed by a 12-month monitoring period.

Post-operative CT scans revealed increased femoral head coverage in all 12 hips, resulting in reversed hip laxity. However, implants exhibited positional deviations from optimal congruency for 5.1 ± 1.7 mm. Mild to moderate osteoarthritis (OA) progression was observed during the lead times and post-operatively. Although force plate analysis showed no significant changes, functional outcomes improved, as demonstrated by reduced owner questionnaire scores at 12 months post-surgery. Post-operative internal rotation and abduction angles were reduced compared to pre-operative values, suggesting potential impingement due to implant positioning. Complications were observed in one dog (two hips). Another dog died nine months post-surgery due to unrelated causes. Post-mortem histology and micro-CT analysis of these hip joints revealed localized cartilage depletion around the implant's rim extension area. However, no lameness or hip discomfort was reported by the owner before the dog's death.

The generic shelf implant effectively enhances hip stability and alleviates pain-related behaviors by improving femoral head coverage. Suboptimal placement was associated with reduced range of motion and OA progression in this study. Refinements to the implant design and adjusting sizing protocols to better match acetabular morphology are necessary.