When more is more: Utilizing finite element analysis to assess chest wall injury stability after surgical stabilization of all rib fractures versus only a portion of the rib fractures.

BACKGROUND

Surgical stabilization of rib fractures (SSRF) continues to gain acceptance. Controversary exists around the number of rib fractures needing stabilization. We sought to analyze chest wall stability (CWS) after SSRF using finite element analysis (FEA) modeling in various rib fracture patterns, hypothesizing not stabilizing all fractures leaves the chest wall unstable.

METHODS

FEA thoracic model development was described previously. Two fracture patterns with three case scenarios each were defined for right ribs 4 to 9. Fracture Pattern 1; Case 1-all 6 ribs with lateral fractures and no stabilization; Case 2-all six fractures stabilized; Case 3-only fractures 5 to 7 were stabilized. Fracture Pattern 2; Case 4-all six ribs fractured in a flail pattern (anterior-lateral and posterior-lateral) and no stabilization; Case 5-all 12 fractures stabilized; Case 6-only six anterior-lateral fractures were stabilized. Three assessment criteria were used to quantify thoracic motion: normalized mean absolute error (NMAE), normalized root mean square error (NRMSE), and normalized interfragmentary motion (NIFM).

RESULTS

Fracture Pattern 1: Case 1-NMAE and NRMSE analysis demonstrated significant loss of CWS up to 50% with left axial rotation; Case 2-CWS almost completely returned to nonfractured state; Case 3-CWS loss up to 37%. Fracture Pattern 2: Case 4-up to 49% of CWS lost with right axial rotation; Case 5-less than 3% CWS lost; Case 6-over 40% CWS lost. For both fracture patterns, when stabilizing all fractures, NIFM decreased by 95%. In Case 3, NIFM decreased by 56% and in Case 6, NIFM increased by 1% at the non-stabilized fracture line.

CONCLUSION

Stabilizing all rib fractures significantly improves CWS. Not stabilizing both fractures of a flail segment worsens motion at the non-stabilized fractures.

LEVEL OF EVIDENCE: Therapeutic/Care Management; Level IV.