Clinical and Surgical Insights on Bilateral Total Knee Arthroplasty in Ochronotic Arthropathy: A Case-based Review.

Introduction: Ochronotic arthropathy (OcA) is a consequence of alkaptonuria, a rare systemic-inherited metabolic disorder leading to accumulation of homogentisic acid in articular cartilage and subsequent early degeneration of the joints. Only few cases of OcA managed with bilateral total knee arthroplasty (TKA) has been described in the literature so far. We aim to discuss surgical pearls, pitfalls, and clinical outcome of OcA of knees managed with simultaneous bilateral TKA. Case Presentation: The patient was a 52-year-old female presented to outpatient facility with severe bilateral knee pain and difficult ambulation. After clinical and radiological diagnosis of osteoarthritis, she was posted for bilateral TKA. During arthrotomy, blackening of articular cartilage, quadriceps and patellar tendon, and synovium was noted. Subchondral bone was free of pigmentation though, seemed osteopenic while taking bone cuts. Right knee was implanted with cruciate retaining components with ultracongruent insert; while on the left side, posterior stabilized components were used. Diagnosis of ochronosis was made retrospectively with characteristic subtle pigmentation of nails, palms, pinnae, and urine homogentisic levels. Two years follow-up of the patient remained satisfactory without any major complications. Conclusion: OcA may present with intra-operative surprise to the surgeon if not anticipated preoperatively. Simultaneous bilateral TKA is safe and effective treatment for end-stage arthritis. However, it is difficult to diagnose it preoperatively; a high clinical suspicion leads to meticulous assessment and counseling regarding potential anesthetic concerns, choice of implant, and possible intra-operative and post-operative complications reported sporadically though.