Abstract
Patients with hereditary multiple exostosis develop several benign osseocartilaginous bulge lesions throughout the body. A 62-year-old woman presented for evaluation of worsening left knee valgus deformity, and left knee pain. She had been diagnosed with hereditary multiple exostosis at the age of 12 years. Radiographic evaluation of the left knee revealed exostoses that caused continuous bulges from cortical bone at the metaphyseal regions of the femur and tibia as well as extra-articular deformity. We used patient-specific instrumentation to indicate the direction of the stem into curved metaphyseal bone regions and then corrected the patient's left knee deformity by performing total knee arthroplasty with titanium-constrained prostheses. Soft tissue release was performed with only complete iliotibial band release at a minimum, and stability was obtained.