The load-displacement characteristics of neonatal rat cranial sutures

Objective: Recently several centers have attempted to distract the craniofa cial skeleton in infants with craniosynostosis. To effectively achieve this goal, we must first understand the normal sutural response to tensile forc es. The objective of this study was to determine the load-displacement char acteristics of neonatal rat sutures. Methods. Thirty cranial sutures were harvested from 1-week-old Wistar rats (10 each coronal, posterior frontal, and sagittal). The width of the harves ted bone-suture-bone construct was standardized to 4 mm. The specimens, kep t moist, were mounted fresh and distracted at 10 mum/sec until rupture usin g a Vitrodyne V1000 universal tester. Standard load-displacement curves wer e constructed. The stiffness, defined as tensile force/change in suture len gth, and the ultimate stress, defined as tensile force at suture rupture/cr oss sectional area, were calculated. Results These sutures demonstrated classical viscoelastic behavior, During the elastic phase, they elongated approximately 1 mum for every 1 g of forc e (10(4) N/m), The ultimate tensile stress was approximately 4 MN/m(2). The estimated mean elastic modulus was 10 megapascals. The posterior frontal s utures were significantly less stiff than the other two sutures (Kruskal-Wa llis nonparametric analysis of variance, p = .0023), The difference in the ultimate stress was also significant (p = .0201). Conclusions: This study provides data regarding the basic mechanical behavi or of neonatal cranial sutures in a mammalian system.