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CASE REPORT article

Front. Pediatr.

Sec. Pediatric Orthopedics

Volume 13 - 2025 | doi: 10.3389/fped.2025.1631106

This article is part of the Research TopicBeyond Standardization in Knee Surgery: Time to Think PersonalizedView all 5 articles

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

Provisionally accepted
Maxime  PillouxMaxime Pilloux1Victor  AyeVictor Aye1Dimitri  FaselDimitri Fasel1Elio  ParisElio Paris1Giacomo  De MarcoGiacomo De Marco2Oscar  VazquezOscar Vazquez2Christina  SteigerChristina Steiger2Romain  DayerRomain Dayer2Sana  BoudabbousSana Boudabbous3Dimitri  CeroniDimitri Ceroni2*
  • 1Faculty of Medicine, University of Geneva, Geneva, Switzerland
  • 2Paediatric Orthopaedics Unit, Paediatric Surgery Service, Geneva University Hospitals, Geneva, Switzerland
  • 3Radiology Department, Geneva University Hospitals, Geneva, Switzerland

The final, formatted version of the article will be published soon.

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.

Keywords: persistent knee flexion1, congenital aplasia2, quadriceps3, pediatric4, hexapod circular frame5

Received: 19 May 2025; Accepted: 30 Sep 2025.

Copyright: © 2025 Pilloux, Aye, Fasel, Paris, De Marco, Vazquez, Steiger, Dayer, Boudabbous and Ceroni. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) or licensor are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Dimitri Ceroni, dimitri.ceroni@hcuge.ch

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