Revision surgery with Ridgestop and 3D-printed guides for grade IV canine medial patellar luxation.

A 4-year-old, 3.9 kg spayed female bichon frise presented with persistent lameness following primary medial patellar luxation (MPL) surgery, including tibial tuberosity transposition, trochleoplasty and lateral imbrication. The physical examination indicated a grade IV MPL. Preoperative CT-based 3D reconstructions revealed varus deformity of the distal femur, valgus deformity of the proximal tibia, internal rotation of the tibial tuberosity and bilateral moderate degenerative changes of the coxofemoral joints, with concurrent grade IV medial patellar luxation. The patient underwent revision surgery with distal femoral osteotomy (DFO), proximal tibial osteotomy (PTO) and Ridgestop placement to augment the medial trochlear ridge. To ensure precise intraoperative alignment, preoperative planning utilised virtual 3D planning and 3D printing to fabricate customised osteotomy surgical guides for both DFO and PTO. Postoperative follow-up revealed no further luxation, with stable weight-bearing ambulation. Radiographic analysis confirmed proper limb alignment and Ridgestop implant placement. Ridgestop could offer an effective treatment option for dogs with recurrent patellar luxation when combined with corrective osteotomy.