Management of a Massive Solitary Femoral Condyle Bone Cyst at the Site of Knee Osteoarthritis with a Synthetic Bone Graft and Primary Robotic-assisted Cementless Total Knee Arthroplasty: A Case Report

INTRODUCTION: Subarticular cystic lesions, also known as geodes, present a challenge in the management of patients undergoing primary total knee arthroplasty (TKA). Although multiple treatment options are available for addressing these lesions, uncertainty persists regarding the optimal approach. CASE REPORT: A 58-year-old man with a history of rheumatoid arthritis presented with several years of left knee pain. Evaluation showed severe left knee degenerative osteoarthritis complicated by the presence of a large lateral femoral condyle cyst. After failing conservative management, a robotic-assisted cementless cruciate-retaining TKA was indicated. The large bone cyst was managed with augmentation using synthetic bone grafting. 1 year postoperatively, he showed excellent clinical outcomes and radiographic evidence of osteointegration. CONCLUSION: This case highlights the value of robotic-assisted technology to plan and execute bone grafting of a large femoral cystic lesion while performing TKA with primary components. A computed tomography-imaged robotic TKA offers the potential benefit of screening bone cysts and thus planning a surgical approach in which bone preservation can be maximized.