An in vitro mechanical and histological study of acute stretching on rabbit tibial nerve

Abstract

Peripheral nerves are often mechanically stretched in association with trauma to extremities, resulting in varying degrees of impairment of nerve function. However, little is known about the biomechanical properties of peripheral nerves and limits of stretching that the nerve may undergo before structural changes occur. Also, the injury pattern of nerves under stretching is poorly understood. In the present study, fresh rabbit tibial nerves (n = 18) were harvested. Nine nerves were stretched to failure in an INSTRON materials testing machine at a rate of 1 cm/min (strain rate of 0.5%/s). Load-deformation and stress-strain curves were determined. Histological examination by light microscopy of the stretched nerves as well as six normal control nerves and three clamped nonstretched control nerves was performed. The results show that the rabbit tibial nerves have an in situ strain of 11.0 +/- 1.5% and exhibit a nonlinear stress-strain relationship. After 20% strain, the curve becomes linear up to failure. The ultimate strain and tensile strength of the nerves were 38.5 +/- 2.0% and 11.7 +/- 0.7 MPa, respectively. At failure, the load dropped suddenly, but the specimens remained grossly intact. Histological analysis of the stretched nerves showed multiple ruptures of perineurial sheaths when compared to controls.

Repair of peripheral nerve defect with direct gradual lengthening of the proximal nerve stump in rats

“…It has been reported that the peripheral nerve's perineurium appears to tolerate distraction force mainly during nerve lengthening and that peripheral nerve viscoelasticity is maintained as long as the perineurium remains. 18,19 In our study, the length between the ring and the marking suture as well as the overlapping length of both nerve stumps was significantly increased in proportion to the distraction period. However, the lengthened amount was less than the distraction amount.…”

“…In physiological conditions, the peripheral nerve trunk usually becomes slightly slack. 18 Thus, many of the distractions were required to overcome such slack in the nerve trunk. After completion of the 20-day distraction, the distance between the ring and the marking suture significantly increased to 12.1 AE 0.8 mm from the initial 1 mm.…”

Mechanical properties of acellular peripheral nerve

“…Under similar experimental conditions, it was found that fresh rabbit tibial nerve had an ultimate stress of 11700 Ϯ 700 kPa and an ultimate strain of 0.385 Ϯ 0.020 [17]. Another experiment documented an ultimate strain of 0.557 [18].…”

Is the lateral jack-knife position responsible for cases of transient neurapraxia?

“…12,18 Peripheral nerve mechanical failure occurs at 27% increase in length. 24 Decrease in blood flow causing patching ischemia and/or tear of the intraneural connecting tissue causing hemorrhage and/or necrosis are considered the pathophysiology behind the symptoms. Continuous high levels of compression or elongation could lead to an increase of the intraneural venous pressure, which produces endoneural edema.…”