# Applying a hexapod circular frame to gradually correct persistent knee flexion due to congenital aplasia of the quadriceps—a case report and review of the literature

## TL;DR

A 10-year-old girl with a rare condition causing severe knee flexion was treated using a hexapod circular frame, significantly improving her mobility and gait.

## Contribution

This case demonstrates the successful use of a hexapod circular frame to correct a previously irreversible knee deformity due to quadriceps aplasia.

## Key findings

- Hexapod circular frames enabled safe and controlled correction of a severe knee flexion deformity.
- The treatment improved the patient's gait and functional mobility significantly.
- Combining patellar mobilization and hamstring tendon transfer with the frame enhanced the correction outcome.

## Abstract

Congenital aplasia or hypoplasia of the quadriceps muscle are rare conditions that significantly impair the extension of the knee joint, resulting in a sustained flexion deformity. These conditions alter overall gait quality, impede daily activities and require effective, timely intervention. Surgical techniques for correction have been described, including soft-tissue release, guided growth, tendon transfer and external fixators. Among the external fixators available, hexapod circular frames are probably the most effective because they enable the precise, progressive correction of complex multiaxial deformities. We present the case of a 10-year-old girl with quadriceps aplasia and a severe flexion contracture of the knee. Surgical treatment involved the mobilisation of the patella, a transfer of hamstring tendons and the application of a hexapod circular frame to control the correction of the flexion deformity. This case study provides a glimpse into the use of hexapod circular frames to remediate severe knee flexion deformities that were previously believed to be irreversible due to the patient's quadriceps muscle aplasia. Safe, controlled aplasia correction greatly improves children's gait and functional ability to move around, making it an invaluable technique for managing difficult congenital knee problems.