Less-invasive stabilization of rib fractures by intramedullary fixation: a biomechanical evaluation.
BACKGROUND
This study evaluated intramedullary fixation of rib fractures with Kirschner wires and novel ribs splints. We hypothesized that rib splints can provide equivalent fixation strength while avoiding complications associated with Kirschner wires, namely wire migration and cutout.


METHODS
The durability, strength, and failure modes of rib fracture fixation with Kirschner wires and rib splints were evaluated in 22 paired human ribs. First, intact ribs were loaded to failure to determine their strength. After fracture fixation with Kirschner wires and rib splints, fixation constructs were dynamically loaded to 360,000 cycles at five times the respiratory load to determine their durability. Finally, constructs were loaded to failure to determine residual strength and failure modes.


RESULTS
All constructs sustained dynamic loading without failure. Dynamic loading caused three times more subsidence in Kirschner wire constructs (1.2 mm +/- 1.4 mm) than in rib splint constructs (0.4 mm +/- 0.2 mm, p = 0.09). After dynamic loading, rib splint constructs remained 48% stronger than Kirschner wire constructs (p = 0.001). Five of 11 Kirschner wire constructs failed catastrophically by cutting through the medial cortex, leading to complete loss of stability and wire migration through the lateral cortex. The remaining six constructs failed by wire bending. Rib splint constructs failed by development of fracture lines along the superior and interior cortices. No splint construct failed catastrophically, and all splint constructs retained functional reduction and fixation.


CONCLUSIONS
Because of their superior strength and absence of catastrophic failure mode, rib splints can serve as an attractive alternative to Kirschner wires for intramedullary stabilization of rib fractures, especially in the case of posterior rib fractures where access for plating is limited.
Bottlang
Michael
M
Biomechanics Laboratory, Legacy Research and Technology Center, Portland, Oregon 97232, USA. mbottlan@lhs.org
Helzel
Inga
I
Long
William
W
Fitzpatrick
Daniel
D
Madey
Steven
S
D000368:Aged; D001696:Biomechanical Phenomena; D001864:Bone Wires / Q000009:adverse effects / Q000592:standards; D004548:Elasticity; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005260:Female; D005548:Foreign-Body Migration / Q000209:etiology; D005594:Fracture Fixation, Intramedullary / Q000009:adverse effects / Q000295:instrumentation* / Q000379:methods; D017102:Fracture Healing; D006801:Humans; D008297:Male; D008422:Materials Testing; D012253:Rib Fractures / Q000601:surgery*; D012399:Rotation; D013165:Splints / Q000009:adverse effects / Q000592:standards; D013718:Tensile Strength; D016474:Weight-Bearing