Is intrathoracic rib plate fixation advantageous over extrathoracic plating? A biomechanical cadaveric study.

BACKGROUND: The high morbidity following surgical interventions on the chest wall because of large incisions often prevents surgeons from operative rib fracture treatment. Minimally invasive approaches to the intrathoracic side of the rib could allow for smaller incisions with lower morbidity while maintaining stability of fixation. The aim of this study was to explore the biomechanical competence of intrathoracic versus extrathoracic plating in a human cadaveric rib fracture model and investigate the effect of plating using two versus three screws per fracture fragment. METHODS: Twenty pairs of fresh-frozen human cadaveric ribs from elderly female donors aged 82.4 ± 7.8 years were used. First, the stiffness of each native rib was calculated via nondestructive (2 N-5 N) biomechanical testing under two loading conditions: ramped two-point bending and combined ramped tensile bending with torsional loading. Second, the ribs were fractured under three-point bending with their intrathoracic side put under tensile stress. Third, specimens were assigned to four groups (n = 10) for either intrathoracic or extrathoracic plating with two or three screws per fragment. Following instrumentation, all ribs were dynamically tested over 400,000 cycles under combined sinusoidal tensile bending with torsional loading (2 N-5 N at 3 Hz). Finally, all specimens were destructively tested under ramped two-point bending. RESULTS: Following instrumentation and cyclic testing, significantly higher construct stiffness was observed for intrathoracic vs. extrathoracic plating under anatomical loading conditions (p ≤ 0.03). No significant differences were detected for implant subsidence after plating with two or three screws per fragment (p ≥ 0.20). CONCLUSION: This study demonstrates significantly higher construct stiffness following intrathoracic over extrathoracic plating, thus indicating superior plate support of the former. In the clinical context, using only two instead of three screws per fragment not only could maintain stability of fixation but also decrease surgery time and costs, and allow for smaller incisions with lower morbidity. LEVEL OF EVIDENCE: Therapeutic/Care Management; Level V.