Limb Lengthening Library
Paley Classification of Complications
A widely used framework for categorizing adverse events in limb lengthening
Category 1 — Problems
Difficulties that resolve without surgery
A difficulty that arises during distraction or fixation and is fully resolved by the end of treatment without an operation.
Classification rule: The course and resolution determine the category. A diagnosis alone does not.
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Category 2 — Obstacles
Resolved by an operative intervention
A difficulty that arises during distraction or fixation, requires an operation to resolve, and is resolved by the end of treatment.
Classification rule: The need for surgery separates an obstacle from a problem, provided the issue is resolved by treatment end.
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Category 3 — Complications
Intraoperative injury or unresolved difficulty
This category includes local or systemic intraoperative or perioperative complications, and difficulties that remain unresolved at the end of treatment or occur afterward.
Severity is separate: Paley also distinguished minor and major complications according to their effect on treatment goals and residual impact.
Why this matters: Authors sometimes report the three Paley categories separately and sometimes combine them under a broad adverse-event total. Before comparing percentages, check the denominator, treatment end point, category definitions, event-versus-patient counting, follow-up, and whether unresolved sequelae are reported.
Based on: Paley D. Problems, Obstacles, and Complications of Limb Lengthening by the Ilizarov Technique. Clin Orthop Relat Res. 1990;250:81–104.
Later studies do not always apply the terms consistently; read each paper's methods before comparing results.
Educational reference only. Not medical advice. This reporting framework does not determine how urgently a symptom should be assessed.