Management of the chronic irreducible patellar dislocation in total knee arthroplasty.

Neglected dislocation of the patella with gonarthrosis, genu valgum, flexion, and external rotation deformity is rarely encountered. Experience with five total knee arthroplasties in three patients with chronic patellar dislocation and gonarthrosis is reported. All knees had a modified proximal patellar realignment and arthroplasty with a constrained prosthesis. Preoperative Hospital for Special Surgery knee scores averaged 55. Average follow-up period was 40 months. At latest follow-up examination, the average Hospital for Special Surgery knee score was 83, the Knee Society knee score was 95, and the functional score averaged 50. There was one complication: a full-thickness lateral skin necrosis requiring flap coverage. The patellar score was zero in all knees. Four knees had mild quadriceps weakness. Three knees rated as excellent and two as good on both The Hospital for Special Surgery and Knee Society rating systems. Radiographic analysis revealed no radiolucent lines or osteolysis. The patellas were centralized in the trochlear groove in all patients. Patellar height averaged 14 mm (range, 12-17 mm). In conclusion, satisfactory results were obtained by restoring axial alignment with a constrained implant and realigning the patella with an extensive proximal realignment.