H. Millesi

The gliding apparatus of peripheral nerve and its clinical significance

Every nerve must have the capacity to adapt to different positions by passive movement relative to the surrounding tissue. This capacity is provided by a gliding apparatus around the nerve trunk. There is another level of gliding provided by the interfascicular epineurium which allows the fascicles to glide against one another. The clinical significance of the gliding apparatus in the context of external and internal neurolysis and nerve repair is discussed. An explanation is offered for the occurrence of the so-called meander-like deformity of fascicles, seen in nerve entrapment syndromes.

PROGRESS IN PERIPHERAL NERVE RECONSTRUCTION

The development of peripheral nerve surgery over the past 15 years has been fascinating to watch. Significant improvements have been achieved by the wide application of techniques which were developed before this period. New approaches may revolutionize the tactics of nerve repair in the near future.RésuméLe développement de la chirurgie des nerfs périphériques depuis 15 ans est fascinant. Des progrès importants ont été accomplis grâce à la large application des techniques qui avaient été développées avant cette période. Une nouvelle approche va probablement révolutionner les techniques de réparation des nerfs dans un proche avenir.ResumenEl desarrollo de la cirugía del nervio periférico en el curso de los Últimos años es fascinante. Se ha logrado un avance significativo mediante la vasta aplicación de técnicas desarrolladas con anterioridad. Nuevos enfoques pueden revolucionar las tácticas de reparación de nervios en el futuro inmediato.

Mechanical properties of peripheral nerves.

Peripheral nerve trunks are viscoelastic tissues with unique mechanical characteristics. Tensile strength, which includes elastic limit and mechanical failure, concerns surgeons. This study shows that measurements of the load necessary to achieve certain elongations on specimens outside the body do not correspond with in situ measurements. The necessary load is influenced by the presence or absence of branches and by the amount of fibrosis. Because of transverse contraction, elongation beyond a certain limit substantially decreases intrafascicular volume, leading to increased intrafascicular pressure. Stress relaxation is effective only if the nerve repair site is maintained under constant tension. Its beneficial effect disappears after 10 minutes if the repaired nerve is returned to a relaxed state. Therefore, tension at the repair site should be minimized.

Biomechanical Properties of Elastase Treated Palmar Aponeuroses

Human palmar aponeurosis was treated with elastase in the presence or absence of soybean trypsin inhibitor. The removal of elastic fibers was complete as proved by electron microscopy. Cyclic loading was performed at a constant strain rate. Residual strain was measured and the stiffness and the fraction of dissipated energy of strain energy was calculated and compared to that of untreated samples of palmar aponeurosis. Residual strain and dissipated energy showed a dramatic increase after enzyme treatment, both in presence and absence of soybean trypsin inhibitor. Stiffness, on the other hand was reduced. The remaining collagen fibers show a more viscous behavior. Our results support the hypothesis that the elastin fibers are responsible for the elastic recovery, observed on specimens of untreated palmar aponeurosis.

Biomechanical Properties of Normal Tendons, Normal Palmar Aponeuroses and Palmar Aponeuroses from Patients with Dupuytren's Disease Subjected to Elastase and Chondroitinase Treatment

Normal tendons, normal palmar aponeuroses and specimens from patients with Dupuytrens disease, namely apparently normal palmar aponeuroses and contracture bands were subjected to elastase and chondroitinase ABC digestion. Maximum Youngs modulus, normalized hysteresis loop and residual elongation were determined before and after enzyme treatment. In normal tendons, normal and apparently normal palmar aponeuroses both normalized hysteresis loop and residual elongation increased significantly after elastase treatment, whereas the stiffness decreased. Normalized hysteresis loop and residual elongation display changes corresponding to the amount of digested elastin. The increased viscosity of untreated contracture bands containing less elastin, as compared to normal palmar aponeurosis, was not affected by elastase. Obviously, the elastic fibers in normal shape and distribution are responsible for maintaining an elastic status with a low viscous stress component. With the exception of contracture bands chondroitinase ABC caused a minor increase of residual elongation and as opposed to elastase a decrease of normalized hysteresis loop indicating an increased mobility of the tissue fibers.