Biomechanical investigation of impact induced rib fractures of a porcine infant surrogate model.
This study investigated the structural, biomechanical and fractographic features of rib fractures in a piglet model, to test the hypothesis that fist impact, apart from thoracic squeezing, may result in lateral costal fractures as observed in abused infants. A mechanical fist with an accelerometer was constructed and fixed to a custom jig. Twenty stillborn piglets in the supine position were impacted on the thoracic cage. The resultant force versus time curves from the accelerometer data showed a number of steps indicative of rib fracture. The correlation between impact force and number of fractures was statistically significant (Pearson׳s r=0.528). Of the fractures visualized, 15 completely pierced the parietal pleura of the thoracic wall, and 5 had butterfly fracture patterning. Scanning electron microscopy showed complete bone fractures, at the zone of impact, were normal to the axis of the ribs. Incomplete vertical fractures, with bifurcation, occurred on the periphery of the contact zone. This work suggests the mechanism of rib failure during a fist impact is typical of the transverse fracture pattern in the anterolateral region associated with cases of non-accidental rib injury. The impact events investigated have a velocity of ~2-3m/s, approximately 2×10(4) times faster than previous quasi-static axial and bending tests. While squeezing the infantile may induce buckle fractures in the anterior as well as posterior region of the highly flexible bones, a fist punch impact event may result in anterolateral transverse fractures. Hence, these findings suggest that the presence of anterolateral rib fractures may result from impact rather than manual compression.
Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
William B
WB
Blackburne
Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
J Neil
JN
Waddell
Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand; Bio-Clinical Sciences, Faculty of Dentistry, University of Kuwait, Kuwait. Electronic address: michael.swain@HSC.edu.kw.
Michael V
MV
Swain
Center of Mechanical Technology and Automation, University of Aveiro, Portugal.
Ricardo J
RJ
Alves de Sousa
Sir John Walsh Research Institute, University of Otago, Dunedin, New Zealand.
Jules A
JA
Kieser
D000818:Animals; D001696:Biomechanical Phenomena; D006801:Humans; D007223:Infant; D008855:Microscopy, Electron, Scanning; D000070602:Rib Cage / Q000293:injuries*; D012253:Rib Fractures; D012272:Ribs / Q000473:pathology; D013552:Swine
Biomechanics; Fracture; Impact; Infant; Porcine; Rib