Stage-IV Medial Femoral Condyle Osteochondritis Dissecans Treated with Unicompartmental Arthroplasty and Trabecular Metal Augmentation.

Abstract

First described by Ahlback et al. in 1968, spontaneous osteonecrosis of the knee (SPONK) occurs most commonly in elderly females with a sudden onset, but without a known precipitating event1. SPONK is described as a distinct entity, bearing no relation to the more common causes of osteonecrosis around the knee, including corticosteroid use, alcohol abuse, coagulopathy, and trauma. Its etiology is unknown but may be attributed to a local microcirculatory vascular disturbance or to subclinical microfractures that weaken the subchondral bone and eventually cause osteoarticular collapse2. Clinical onset of SPONK is often abrupt, characterized by medial condylar tenderness, synovitis, effusion, and pain. Localized intense radiotracer uptake on a three-phase bone scan is suggestive of an osteonecrotic lesion3. Koshino4 recommended nonoperative management for Ahlback stage-I and II lesions. For stage-III, IV, and V lesions, various treatment options exist. These include arthroscopy with debridement and microfracture, osteoarticular transfer system procedure, high tibial osteotomy, and prosthetic arthroplasty2. Nonarthroplasty options have had mixed results4-6. Both total and unicompartmental knee arthroplasty (UKA) have had good results for focal osteonecrotic lesions, particularly of the medial femoral condyle7-12. However, there is scant information on the treatment of very large lesions, which are associated with a poorer prognosis. Reports do not specify the lesion volume or location for which a UKA is suitable and safe to perform. Invariably, residual defects may be filled with cement or bone graft. If appropriate fixation cannot be achieved, then total knee arthroplasty is required. For large lesions, bone cement may not provide adequate stability. Trabecular Metal (Zimmer, Warsaw, Indiana) augments are commonly used in revision total knee replacement13. Short and midterm follow-up show excellent clinical results with their use, including reliable …