Evaluación biomecánica y análisis de clavo intramedular telescópico de fémur reutilizado en niño con acondroplasia

Introduction

Telescopic intramedullary nails (TIMN) have represented a significant advancement in limb lengthening procedures. However, their elongation capacity is limited to 5 cm in the bones of patients with achondroplasia. Consequently, techniques involving TIMN reutilization have been developed. This reuse presents mechanical and safety challenges due to material fatigue and repetitive loading, which may compromise the structural integrity of the implant. This study evaluates the biomechanical performance and potential damage of a reused TIMN.

Methods

An experimental analysis was conducted on a TIMN removed after 2 5 cm lengthening procedures in a patient with achondroplasia. The nail was measured and assessed following non-destructive deconstruction, material analysis, 3 D modeling through reverse engineering, and finite element analysis to assess its behavior under different loading conditions.

Results

Mechanical and chemical damage was identified, compromising the nail's integrity. The aged Ti6Al4V alloy was validated for its resistance to complex loads. The 3 D modeling showed that the gear mechanism effectively converted rotational movement into translational motion. The finite element analysis revealed that the safety factor reached its critical limit at angles of 2.44 and 2.25°, showing that the nail was nearing its resistance limit. The stem and guide were identified as critical components.

Conclusions

TIMN reutilization must be performed with caution due to potential material fatigue. This study provides a foundation for redesigning these implants to improve their capacity to withstand prolonged loading cycles.