The Load-Displacement Characteristics of Neonatal Rat Cranial Sutures

Abstract

Objective

Recently several centers have attempted to distract the craniofacial skeleton in infants with craniosynostosis. To effectively achieve this goal, we must first understand the normal sutural response to tensile forces. The objective of this study was to determine the load-displacement characteristics 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 harvested bone-suture-bone construct was standardized to 4 mm. The specimens, kept moist, were mounted fresh and distracted at 10 μm/sec until rupture using a Vitrodyne V1000 universal tester. Standard load-displacement curves were constructed. The stiffness, defined as tensile force/change in suture length, and the ultimate stress, defined as tensile force at suture rupture/cross sectional area, were calculated.

Results

These sutures demonstrated classical viscoelastic behavior. During the elastic phase, they elongated approximately 1 μm for every 1 g of force (10⁴ N/m). The ultimate tensile stress was approximately 4 MN/m². The estimated mean elastic modulus was 10 megapascals. The posterior frontal sutures were significantly less stiff than the other two sutures (Kruskal-Wallis 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 behavior of neonatal cranial sutures in a mammalian system.