Universal long bone defect classification: step by step from diagnosis to treatment strategy and outcome assessment. Part 1: diaphyseal defects

This article presents the Universal Long Bone Defect Classification (ULBDC), developed for the standardized description of bone defects, selection of treatment strategy, and assessment of reconstructive outcomes. The current paper focuses on the part of the classification dedicated to diaphyseal defects. The system is based on AO/OTA principles and uses an alphanumeric hierarchical code reflecting localization (bone and segment) and defect morphology (type, group, subgroup, specification) according to the principle “from simple to complex.” To ensure standardized reporting, a unified terminology is proposed to provide precise morphological assessment of bone defects. The following terms are introduced: anticipated bone defect (BDa), cortical bone defect (BDc), and segmental bone defect (BDs). The classification is based on key morphological parameters, including bone integrity (Bi) and defect dimensions (length and width) relative to bone diameter (Bd). For segmental defects, particular attention is paid to shortening (Sh) and diastasis (D). Three types of diaphyseal defects are described: Type A — defects with preserved bone integrity (cortical and anticipated defects), Type B — non-segmental defects (cortical defects with disrupted bone integrity), and Type C — segmental bone defects. The hierarchical structure reflects increasing reconstructive complexity and prognostic severity. The possibility of transforming more complex defects into less complex ones through specific surgical strategies is demonstrated, highlighting the algorithmic value of the system. The ULBDC standardizes terminology, facilitates professional communication, and provides a foundation for the harmonization of clinical research. Despite its relative complexity, the classification demonstrates high reproducibility and practical relevance.