Multiple hereditary exostosis and hedgehog signaling: implications for novel therapies

Total hip and knee arthroplasty in patients with hereditary multiple exostoses

To the authors' knowledge, few reports have been published in the English literature of using total knee arthroplasty and total hip arthroplasty for the treatment of hereditary multiple exostoses. This article describes 2 patients with hereditary multiple exostoses, 1 treated with total hip arthroplasty and 1 treated with total knee arthroplasty. Bony deformities make arthroplasty uniquely challenging in patients undergoing total hip or knee arthroplasty. An expanded metaphysis of the proximal femur, coxa valga deformity, and the presence of hardware from previous reconstructive surgeries can make total hip arthroplasty technically difficult. Substantial bony deformity of the distal femur, valgus deformity of the knee, and sizing issues that necessitate custom implants can make total knee arthroplasty difficult. The most common bony deformities in hereditary multiple exostoses are short stature, limb-length discrepancy, valgus deformity at the knee and ankle, and asymmetry of the pectoral and pelvic girdles. Most reported surgical treatments for patients with hereditary multiple exostoses focus on the pediatric population or the management of malignant transformation of exostoses. Studies that specifically address the conditions associated with knee deformities focus on extra-articular deformity correction rather than arthroplasty.When arthroplasty is necessary in this patient population, an understanding of the commonly occurring deformities can help with preoperative planning and surgical management. All painful lesions must be evaluated for malignant transformation. Bone scans can be useful during workup. All specimens should be sent for pathologic evaluation. Such patients are challenging because of the distorted hip anatomy and valgus knee deformity. The current 2 cases illustrate specific challenges that can be anticipated and underscore key principles for arthroplasty in the management of hereditary multiple exostoses.