Total Knee Replacement for Varus Deformity in Osteoarthritis of Knee with Multiple Hereditary Exostoses - A Rare Case Report.

Abstract

Introduction: Multiple hereditary exostosis (MHE) is a genetic condition inherited in an autosomal dominant manner, resulting from point mutations in exostosin genes. Knee deformities, such as genu valgus, are common in individuals with MHE, often localized to the proximal tibial metaphysis, and occasionally involving the femur. Osteochondromas at the knee can lead to an oblique joint line orientation, contributing to earlier onset arthritis. Increased angulation may also lead to lateral patella subluxation and patellofemoral complaints, necessitating earlier interventions compared to the general population. While total knee arthroplasty (TKA) for osteoarthritis in MHE with varus deformity is rarely reported in the literature, we present a case of a high body mass index (BMI) female with MHE and varus knee deformity successfully treated with TKA using a standard posterior stabilized implant, without additional constraints or extensive releases.

Case report: A 54-year-old Indian woman, homemaker presented to the clinic due to progressive left knee pain and varus deformity. Her BMI was 40. With no significant family history . The surgery was performed using a tourniquet. Using standard instrumentation for conventional TKA . The angle of bone resection was determined preoperatively through manual radiographic templating. The sizing of femoral component was done precariously since the anatomy of distal femur was altered with no prominent anterolateral ridge and an anterior referencing system was done to avoid notching. Tibial rotational alignment was based on anatomic landmarks. Patellofemoral tracking was excellent and did not require lateral retinacular release.

Conclusion: Careful attention to technical aspects, selection of implants and the unique anatomy involved, is crucial in planning this procedure. Ensuring proper balance of the ligaments tented by the osteochondromas and meticulous sizing of the femur are essential for favorable functional outcomes in such cases.