# Biomechanical Fracture Thresholds of the Tibia and Fibula Under Axial and Multi-axial Loading: A Systematic Review

## TL;DR

This review summarizes how much force is needed to fracture the tibia and fibula under different types of loading, highlighting the importance of multi-axial forces in injury prediction.

## Contribution

The study provides a systematic synthesis of biomechanical thresholds for tibial and fibular fractures under axial and multi-axial loading conditions.

## Key findings

- Tibial fracture thresholds range from ~7.5 kN in females to 11.3 kN under combined axial and bending loads.
- Multi-axial loading reduces fracture tolerance compared to isolated axial loading.
- The fibula increases axial tolerance by approximately 10%.

## Abstract

This systematic review synthesizes evidence on biomechanical fracture thresholds of the tibia and fibula under axial and multi-axial loading. A comprehensive search of PubMed, Embase, Scopus, and the Cochrane Library identified six studies, including experimental cadaveric, computational, and material testing investigations, comprising 72 postmortem specimens and validated finite element models. Outcomes assessed included axial force, bending moments, failure load, stress distribution, and fracture patterns. Results indicate that tibial fracture thresholds range from ~7.5 kN in female specimens to 11.3 kN under combined axial and bending loads, with fibula contribution increasing axial tolerance by ~10%. Variance and confidence interval measures were not reported in the included biomechanical studies; therefore, findings are presented descriptively.

Multi-axial loading consistently reduced fracture tolerance compared with isolated axial loading, and fracture resistance was influenced by specimen gender, load duration, and biomechanical methodology. Risk of bias ranged from low to moderate across studies. These findings provide clinically relevant benchmarks for injury prediction, preclinical testing, and orthopedic device design, emphasizing the importance of multi-axial assessment in understanding lower-limb fracture mechanics.