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Intradiscal injection of chymopapain for the treatment of sciatica due to disc herniation has been used for more than 25 years, but is still under debate. We review the indications, complications, and clinical results, and discuss the tissue effects of chymopapain. The results following surgical disc removal versus chymopapain injection indicate that surgery with removal of the disc hernia through a small laminotomy remains the documented treatment of choice for patients with proven disc herniation and sciatica in whom conservative treatment has failed.

Surgical treatment of peripheral nerve lesions associated with intraneural fibrosis is sometimes extended to include internal neurolysis. This procedure is performed in order to release the individual nerve fascicles from interfascicular scar tissue which is believed to constrict nerve fibres and thereby interfere with their function and regenerative capacity. However, an internal neurolysis per se implies a significant trauma to the nerve and may induce microvascular damage and formation of new intraneural scar tissue. Considering this, such a procedure appears justified only when the preoperative intraneural fibrosis is more severe than the scarring which might be induced by the surgical procedure as such. In order to evaluate the tissue reactions following internal neurolysis an experimental investigation was carried out: internal neurolysis was performed on normal rabbit tibial nerve. After varying postoperative periods up to 6 months specimens of nerves were analysed. Reactive changes of connective tissue and myelin sheath lesions, indicating nerve fibre damage, were investigated in histological sections studied by light microscopy. Barrier function of perineurial membrane and endoneurial vessels was investigated by fluorescent microscopic tracing of locally applied or intravenously injected albumin labelled with Evans' blue. The results indicate that an experimental internal neurolysis per se may induce fibrosis in all layers of the nerve and may cause some nerve fibre damage. However, the barrier function of the perineurium and the endoneurial vessels seems to be generally well preserved. The findings are discussed in relation to indications for internal neurolysis.

Experimental compression lesions of peripheral nerves were induced by applying pressure direct to exposed rabbit nerve trunks. A specifically designed compression chamber was used, enabling application of graded pressures (50--600 mmHg) to the nerves for various periods of time (15 min to 6 hours). After releasing the pressure, analyses were performed concerning the intraneural microvascular permeability and the barrier function of the perineurium. The method used was fluorescence microscopic tracing of intravenously injected or locally applied albumin labelled with Evans blue. The results indicate that a slight trauma to a nerve (e.g. 50 mmHg during 2 hours) induced an epineurial oedema by increasing the permeability of the epineurial vessels, which were more susceptible to compression trauma than the endoneurial vessels. Compression at higher pressure levels or of prolonged duration caused injury also to the endoneurial vessels, leading to intrafascicular oedema formation, which generally was most prominent at the edges of the compressed nerve segment. The perineurial barrier was remarkably resistant to compression trauma. Possible pathophysiological effects of various degrees of post-traumatic intraneural oedema formation are discussed.

1. Stretching of the tibial nerve cut 2 centimetres above the ankle has been the subject of an experimental study in rabbits. 2. The effects on intraneural microcirculation, on vascular permeability, and on the barrier function of the perineurium have been analysed with the aim of determining the extent to which a divided nerve can be stretched without interfering with the process of repair. 3. The results obtained may prove valuable for understanding basic mechanisms and for establishing certain important limitations when end-to-end suture of a nerve trunk is performed under some degree of tension in man.

Endoneurial fluid pressure measurements were made in the interstitial space of rat L5 dorsal root ganglia and in the corresponding sciatic nerves. Endoneurial fluid pressure was always higher in the ganglia than in the paired distal nerve. This proximodistal gradient in endoneurial fluid pressure may be the driving force responsible for the proximodistal convection of endoneurial fluid.

Compression injuries of spinal nerve roots are very common. However, the basic pathophysiology of these conditions is not fully understood. In this study a model is presented for experimental graded compression of the nerve roots of the pig cauda equina, including a technique for vital microscopic studies on the microcirculation flow of the intrinsic vessels of the nerve roots during compression. With this model critical pressure levels for compression-induced occlusion of the arterioles, capillaries, and venules of the intrinsic vasculature of the nerve roots were determined. The study showed that the average minimum pressure in the inflated balloon required to stop the flow in the arterioles was 127 mm Hg (SD = 18, n = 11), in the capillaries 40 mm Hg (SD = 6, n = 12), and in the venules 30 mm Hg (SD = 10, n = 12). The average mean arterial pressure (MAP) was 150 mm Hg (SD = 14, n = 12). There was a statistically significant correlation (p greater than 0.001) between the MAP and the pressure required to stop the flow in the arterioles (r = 0.83, n = 14), but no correlation between MAP and capillary (r = 0.09 NS, n = 20) or venular (r = -0.28 NS, n = 34) occlusion pressure. After the nerve roots had been compressed at 50 or 200 mm Hg for 10 min or 2 h, the recirculation started immediately. There was a hyperemia during the first 10 min, with a dilatation of the vessels, particularly the venules. In nerve roots exposed to compression for 2 h at either 50 or 200 mm Hg, an intraneural edema developed.(ABSTRACT TRUNCATED AT 250 WORDS)

Edema formation in spinal nerve roots of the pig cauda equina was studied following experimental compression at various pressure levels, durations, and rates of onset, using a fluorescence microscopic technique. The time-pressure thresholds for the occurrence of edema in the nerve roots were: following rapid onset of compression (0.05-0.1 seconds), 2 minutes at both 50 mm Hg and 200 mm Hg, and following slow onset of compression (the pressure was slowly increased during 15-20 seconds), 2 hours at 50 mm Hg and 2 minutes at 200 mm Hg. Generally, the edema formation was more pronounced after rapid than after slow onset of compression. The data in this study also indicate that intraneural edema might be more easily formed in nerve roots than in peripheral nerves after compression injury.

Collagenase was injected into the ears of rabbits and the cheek-pouches of hamsters. The acute and long-term microvascular effects were studied by vital microscopy and microangiography. The enzyme was injected at three different concentrations: 120 units/ml, 600 units/ml and 3,000 units/ml. The medium (600 units/ml) and high (3,000 units/ml) concentrations induced effects on the microcirculation such as blood flow impairment and microbleedings. The magnitude of these effects was related to the concentration of the enzyme. Generally, these microvascular effects were of low magnitude as compared with other substances tested using the same experimental models.

Longitudinal and radial tissue-fluid pressure distributions were determined beneath and adjacent to wide (12 and 18 cm) pneumatic tourniquet cuffs placed on intact human cadaveric arms and legs, respectively. Tissue fluid pressures exhibited relatively broad maxima at midcuff, and in most cases showed no differences at the various depths studied. Limb circumference was not a determining factor in the transmission of pressure to deeper tissue. We also investigated the effect of four cuff sizes (4.5, 8, 12, and 18 cm) on eliminating blood flow to the lower legs of normal subjects. The cuff pressure required to eliminate blood flow decreased as cuff width increased; thigh circumference was a determining factor in the pressure required to eliminate blood flow while using the smaller cuffs, but not while using the 18-cm cuff. Thus, wide cuffs transmit a greater percentage of the applied tourniquet pressure to deeper tissues than conventional cuffs; accordingly, lower cuff pressures are required, which may minimize soft-tissue damage during extremity surgery.