a new adJuStaBle Pinch deSigned for Producing cruSh nerVe inJurieS in the Sciatic nerVe of ratS

Much of the accrued knowledge on physiology, pathology, degeneration, treatment and regeneration of peripheral nerves have resulted from experimental studies on small animals1-5, particularly on rats, whose spontaneous regeneration speed favors short-term studies. The sciatic nerve of rats is a reliable model for studying different kinds of injuries and treatment methods, with crushing injuries being one of the preferred types, because it causes rupture of nervous fibers without rupturing most of the nerve’s supporting structures6,7, enabling an easier regeneration after injury.8-13 Although experimental crushing injuries on rats’ sciatic nerve with different purposes and objectives are well disseminated, there is no definitive standard concerning almost all parameters associated to the mechanism of injury, starting from the instrument or device employed. Described mechanisms range from applying external compression with a tourniquete14, to a direct nerve approach and the application of some kind of crushing instrument, such as microsurgical or watchmaker pinches8 or even sutures with surgical wires15 and some types of machines.7,9,16 In a series of previous studies, the authors hereof used a universal assay machine9,10,12 or a dead-load machine17, always with predetermined and controlled loads throughout the time established for producing it. Despite of the reliability of the results achieved with both machines, its use itself is relatively difficult, because an anesthetized animal with exposed sciatic nerve must be taken there and adapted on the accessories enabling its use in order to manipulate such a small anatomical structure. The universal assay machine has the additional disadvantage of gradually reducing the applied load, with crushed nerve accommodation, requiring continuous adjustments in order to keep it at the planned levels. The dead-load machine solves this problem17, but it is a robust instrument. After using both kinds of machines, the authors of the present study envisaged the possibility of obtaining the same results with a much simpler and user-friendly device, which is an adjustable crush-maker pinch for in loco use, without the need of transferring and adapting the animals as happened with previously employed machines. The pinch was designed and built with a mechanism activated by an adjustable tension spring, its calibration being made with a load cell.