Novel classification of tibial hemimelia and reconstruction-guiding principles

Tibial hemimelia is an extremely rare congenital limb deficiency characterized by variable tibial absence, knee instability, and ankle deformity. Existing classification systems rely primarily on static radiographic morphology and provide limited guidance for surgical decision-making, particularly regarding limb reconstruction versus amputation. Determinants of limb salvage especially the integrity of the quadriceps extensor mechanism and knee stability are not systematically incorporated into current classifications. This study proposes a novel classification designed to integrate anatomical findings with biomechanical and surgical considerations. Our aim is to propose a descriptive classification integrating radiographic anatomy with extensor mechanism assessment and reconstruction-oriented surgical planning.

A retrospective cohort study was conducted including 566 patients with tibial hemimelia managed with a limb-reconstruction strategy between 1990 and 2020. Patients were classified according to a new framework based on five domains: tibial morphology, quadriceps mechanism integrity, knee stability and active extension, ankle stability and distal support, and expected evolution during growth. Based on these criteria, patients were categorized into five types (I-V), each linked to a defined reconstructive strategy involving centralization procedures, tibio-fibular synostosis, or staged Ilizarov-based deformity correction and lengthening. Primary outcomes included limb preservation, achievement of a plantigrade or braceable foot, and ambulation.

Among the 566 patients, distribution across types was: Type I (240), Type II (160), Type III (20), Type IV (130), and Type V (16). Severe deficiencies (Types I-II) represented the majority of cases. Reconstruction strategies tailored to type enabled limb salvage in the vast majority of patients, with most achieving plantigrade alignment and ambulation with or without orthotic support. Patients with preserved quadriceps function (Types IV-V) generally required fewer reconstructive stages and ambulation was achievable in a substantial proportion of patients following staged reconstruction. Complications typical of limb reconstruction-such as pin-site infection, joint stiffness, and regenerate issues-were observed but were largely manageable within staged treatment protocols. Parental satisfaction with limb preservation and mobility was consistently high.

The purpose of this paper was not to evaluate reconstructive outcomes, but to establish a reproducible classification framework. This study introduces a classification of tibial hemimelia that prioritizes quadriceps mechanism integrity and joint stability. Applied to one of the largest reported cohorts of tibial hemimelia patients, the system provides a practical surgical decision-making framework linking deformity patterns to specific reconstructive strategies. By shifting the emphasis from static radiographic description to dynamic assessment, the proposed classification facilitates rational limb-salvage planning and supports the feasibility of reconstruction even in severe forms of tibial deficiency.