End-to-side nerve repair in a large animal model: how does it compare with conventional methods of nerve repair?

A large animal (sheep) model was used to compare nerve axon regeneration and return of muscle function after a median-to-ulnar nerve end-to-side neurorrhaphy technique with conventional, clinically established, methods of nerve repair and untreated controls. Three groups of sheep were allocated to end-to-side repair (12 animals), a conventional method of nerve repair (18 animals), or a control group (eight animals). After a year nerve repairs were assessed electrophysiologically and histologically, and the muscles supplied by the repaired nerves were assessed physiologically. There were no significant differences in the outcomes of nerve repair between different conventional techniques. Half of the end-to-side nerve repairs supported nerve regeneration. The functional outcomes of the end-to-side repairs were inferior to conventional techniques which were, in turn, inferior to controls. End-to-side neurorrhaphy supported nerve regeneration, but the reliability of this technique is called into question and its use as a clinical tool can only be recommended as a salvage procedure.

Endovascular treatment of a giant aneurysm of the maxillary artery.

Aneurysms of the maxillary artery are rare and the majority of the literature refers to false aneurysms. We report the first case of what we believe to be a spontaneous true maxillary artery aneurysm and its endovascular management.

Subintimal angioplasty of a crural vessel via an antegrade popliteal artery puncture.

Percutaneous retrograde puncture of the popliteal artery is a well-described technique and offers an alternative site for access to the peripheral vascular system. Antegrade popliteal artery puncture has only been described once in the literature. We present a case of subintimal angioplasty of a crural vessel occlusion using an antegrade popliteal approach. This report highlights that if other access is not possible due to unfavourable anatomy this approach is a technically feasible option.

Treatment of chronic mesenteric ischemia by subintimal angioplasty of an occluded superior mesenteric artery.

INTRODUCTION: Subintimal angioplasty is an established technique for the recanalisation of occluded vessels. It has been applied extensively to the peripheral arterial system but not the mesenteric vessels in mesenteric angina. REPORT: We report the first described case of recanalisation of a mesenteric vessel. The vessel has remained patent for five years with good symptomatic relief. DISCUSSION: Subintimal angioplasty could represent an alternative treatment to major surgery for occlusive disease of the mesenteric vessels.

The use of ciliary neurotrophic factor to promote recovery after peripheral nerve injury by delivering it at the site of the cell body.

Despite a body of evidence showing that various neurotrophic factors support the survival of nerve cells and stimulate axonal outgrowth, doubt remains about their optimal site of application as well as the more compelling question of what clinical benefit, if any, they would confer. Ciliary neurotrophic factor (CNTF) supports the survival of motorneurons in vitro and in vivo. Direct delivery of CNTF to the cell bodies may help reduce the side effects and overcome the problem of rapid systemic clearance. The aim of this study was to establish whether nerve regeneration may be improved upon by the controlled addition of a specific humoral neurotrophic substance (CNTF) at the level of the cell body. Three groups of five adult sheep were used. The first group acted as normal controls. In the second and third groups, the median nerve was divided and repaired using an epineurial suture technique. In the second group, CNTF was supplied into the CSF at the level of C6 by an implanted osmotic pump. In the third group physiological saline was placed in the osmotic pump. The animals underwent comprehensive electrophysiological and isometric tension experiments at six months. All of the animals had reduced electrophysiological, morphometric and isometric tension indices after surgery compared to normal. The CNTF group had better results than the saline group in the following; (1) area and amplitude of the muscle action potential (2) the percentage of tetanus and muscle mass preserved after repair. These differences were only statistically significant for amplitude of the muscle action potential. No statistical difference was found in the morphological indices (fibre diameter, axon diameter, myelin thickness and internodal length) between the CNTF and saline groups. CNTF does not confer a functional benefit when applied at the level of the cell body.

Dipstick screening for urinary tract infection before arthroplasty: a safe alternative to laboratory testing?

We performed a prospective study on 247 consecutive patients attending our arthroplasty pre-admission clinic over six months, to compare the accuracy of dipstick urinalysis with the standard microbiological test for excluding urinary tract infection. There were 22 positive culture results and 43 positive dipstick results, with 16 true positives and 198 true negatives. Sensitivity was 72.7%, lower then the 88.0% figure for specificity. The positive predictive value was 37.2%, and the negative predictive value was 97.1%. Dipstick urinalysis is ideally suited to the busy pre-admission setting and would have resulted in a 90% reduction in the number of samples sent for laboratory analysis. In view of these results, we have changed our working practise from performing cultures to dipstick urinalysis on all patients prior to arthroplasty.

Assessment of the method and timing of repair of a brachial plexus traction injury in an animal model for obstetric brachial plexus palsy.

A Sunderland type IV traction injury to the C6 root of adult sheep or newborn lamb brachial plexus was used as a model for obstetric traction injury to the C5 root in humans. In one experimental cohort the injury was created and repaired using interfascicular nerve autografts or coaxially aligned freeze-thawed skeletal muscle autografts in a group of adult sheep and in a group of newborn lambs. In a second cohort a similar injury was created and repaired either immediately or after a delay of 30 days, using either interfascicular nerve autografts or coaxially aligned freeze-thawed skeletal muscle autografts in four groups of six newborn lambs. In all cases both functional and morphometric indices of nerve regeneration were poorer in the injured and repaired nerves than in normal nerves. In lambs the method of repair made no difference and no significant differences were found for any of the indices of nerve function or morphology. In sheep the use of muscle grafts was associated with a poorer outcome than the use of nerve autografts. Where a delay of 30 days had elapsed between injury and repair, the results using nerve autografts were not significantly different. Where freeze-thawed muscle autografts had been used, the maturation of the regenerated nerve fibres after delay was significantly poorer than after immediate repair. The electrophysiological variables CV(max) and jitter, which may be applied clinically, were found to be good discriminators of recovery in all of the animals and in respect of all procedures.

Obstetric brachial plexus palsy: a comparison of the degree of recovery after repair of a C6 ventral root avulsion in newborn and adult sheep.

The C6 motor rootlets were avulsed from the spinal cord in six newborn lambs to simulate a birth lesion of the upper root of the brachial plexus. Six 1-year-old sheep were used for comparison, and treated in a similar manner. The injury was repaired immediately in each group using an autologous coaxial freeze-thawed skeletal muscle graft. The animals were allowed to recover for 1 year after the surgery. The C6 root was then examined electrophysiologically and morphologically. The results were compared with those obtained from a group of untreated intact 1-year-old sheep. The fibre and axon diameters and myelin sheath thickness were significantly different in the group repaired as lambs when compared with the group repaired at the age of 1 year. There was also a significantly increased maximum conduction velocity and a greater range of conduction velocities within the nerve in the lambs. Central motor latency was significantly slower in the sheep than in the lambs. These findings would suggest a greater potential for recovery in the lambs after brachial plexus root avulsion injuries.

The use of conventional and invaginated autologous vein grafts for nerve repair by means of entubulation.

Nerve repair by entubulation has re-emerged recently as a possible means of enhancing the microenvironment at the site of repair by inclusion within the tube of various trophic factors. To this end, a modification of the vein-graft technique has been used by turning it inside out before repair, to expose the adventitial surface to the regenerating axons. A comparative study of standard vein grafting versus the inside-out technique was carried out in two equal-sized groups of inbred Lewis rats. Jugular vein isografts were derived from litter mates. The sciatic nerve was transected and repaired by entubulation using the standard vein graft in one group and the inside-out graft in the other group. Morpho-metric and electrophysiological assessment were carried out 3 months after repair. When the animals were assessed it was found that both the standard-vein-graft group and the inside-out group exhibited a reduction in all of the morphometric and electrophysiological variables when compared to normal nerves. The mean axon diameter, fibre diameter and myelin sheath thickness were, however, found to be greater in the group that underwent the inside-out repair. The superior morphometric results seen in the inside-out group were not matched by improved electrophysiological performance. It is concluded that the use of the inside-out technique confers no functional benefit over standard vein grafting.

Obstetric brachial plexus palsy: a large animal model for traction injury and its repair. Part 1: age of the recipient.

A Sunderland type IV traction injury to the C6 root of the sheep or lamb brachial plexus was used as a model for obstetric traction injury to the C5 root in humans. The injury was created and immediately repaired using interfascicular nerve autografts in a group of adult sheep and a group of newborn lambs. The animals were examined using electrophysiological and morphometric techniques 1 year after operation. It was found that the recovery of neuromuscular function was superior in the lambs. The implication is that nerves in newborn animals have a better potential for regeneration than that seen in older individuals. This is discussed with reference to the management of obstetric brachial plexus palsy.

Biodegradable controlled release glass in the repair of peripheral nerve injuries.

The experiments in this paper were concerned with the recovery of function and ease of application of an entubulation technique using a biodegradable, controlled release glass tube (CRG) for the repair of a transected peripheral nerve. The peroneal nerves of 15 New Zealand White rabbits were repaired with either a CRG tube filled with freeze-thawed muscle, or a conventional freeze thawed muscle graft (FTMG). These were compared with controls in which a CRG was used to enclose the cut ends of a nerve separated by a 1 cm gap. Electrophysiological and morphometric assessment was carried out 6 months after repair. No statistical difference was found in any test between the FTMG and the CRG tube filled with freeze thawed muscle. The CRG tube and 1 cm gap produced inferior levels of recovery of function when compared with the other two repair groups.

Peripheral nerve reconstruction using freeze-thawed muscle grafts: a comparison with group fascicular nerve grafts in a large animal model.

There is evidence to suggest that the 'freeze-thawed muscle graft' may function as an alternative to established methods of nerve reconstruction. Using a large animal model we compared this method with group fascicular nerve grafting in peripheral nerve reconstruction. We excised a 3 cm segment of right median nerve in 10 anaesthetized sheep. The resulting gaps were repaired with either group fascicular cable grafts (GFCGs) or freeze-thawed muscle grafts (FTMGs). After six months the right (grafted) and left (control) median nerves of each sheep were exposed and assessed for nerve blood flow, nerve conduction velocity and morphological indices of recovery. Nerve blood flow was reduced by 40% in those repaired with FTMGs. All the repaired nerves contained a population of significantly smaller nerve fibres and displayed a reduced peak nerve conduction velocity. Those repaired with FTMGs (mean velocity 30.96 m/s) had a peak velocity significantly faster than the GFCG group (mean 13.16 m/s). This study shows that peripheral nerve reconstruction with freeze-thawed muscle grafts compares well with repair using nerve grafts.

An electrophysiological and morphological comparison of the microwave muscle graft and the freeze-thawed muscle graft.

The purpose of this study was to assess the feasibility of using a microwave oven to produce denatured muscle grafts for the repair of 1 cm deficits in the rabbit peroneal nerve. Recovery of function was assessed after 6 months by electrophysiological and histological examination of the peroneal nerve and target muscles. The results were compared to normal rabbits and to a group whose nerves were repaired with freeze-thawed muscle grafts (FTMG). The results of this study showed that heating muscle in a microwave oven does produce a graft which may be used as an alternative to the FTMG. However, the technical difficulties in preparing a microwave muscle graft make the use of this technique in the clinical setting unlikely.

Neuropathological findings after intracerebral implantation of microdialysis catheters.

The neuropathological and immunocytochemical changes in the sheep forebrain following 7 days of microdialysis, using a catheter approved for human use, are described. There was no behavioural dysfunction and light microscopy revealed mild astrogliosis and patchy macrophage infiltration immediately adjacent to the catheter track. The surrounding neuropil was normal. There was one small subcortical haemorrhage (10 x 1.5 mm). These findings are similar to those following microdialysis in rodents and suggest that the risk of significant damage to the human brain is low, that neuropathological changes in the brain around the catheter should not interfere with local brain metabolism, and that the catheter should be affixed in such a way as to minimize movement-induced damage to the brain.

A comparison of the neuromuscular and cardiovascular effects of vecuronium, atracurium and mivacurium in sheep.

Neuromuscular and cardiovascular effects of vecuronium, atracurium and mivacurium were compared in 45 sheep. The onset and duration of neuromuscular block produced with loading doses of vecuronium (25 microg kg(-1)), atracurium (500 microg kg(-1)) and mivacurium (200 microg kg(-1)) and maintained with incremental doses (7, 170 and 70 microg kg(-1), respectively) were monitored using train-of-four stimulation of the n. facialis-m. levator nasolabialis unit. The electrocardiogram, heart rate and arterial blood pressure were recorded during onset of neuromuscular blockade. Mean loading dose onset times for atracurium (98 seconds) and mivacurium (86 seconds) were significantly shorter than vecuronium (203 seconds). Vecuronium produced significantly longer block (40 minutes) than atracurium (28 minutes) and mivacurium (15 minutes). There was no evidence of drug cumulation with atracurium or mivacurium. Cardiac dysrrhythmias were not observed in any group. Atracurium and mivacurium produced intermediate- and short-duration neuromuscular blockade, respectively. Vecuronium produced a prolonged effect after a slow onset.

A comparison of edrophonium and neostigmine for the reversal of mivacurium-induced neuromuscular blockade in sheep.

The rate of reversal of neuromuscular block was compared in 36 sheep receiving either edrophonium (500 microg kg(-1)) and atropine (80 microg kg(-1)), neostigmine (50 microg kg(-1)) and atropine (80 microg kg(-1)) or saline (10 ml), using the train of four count (TO4C) recorded at n. facialis-m. levator nasolabialis. Neuromuscular block was produced with mivacurium (200 microg kg(-1)) followed later by a single incremental dose of 70 microg kg(-1). Antagonists or saline were given when spontaneous recovery from the incremental dose (TO4C = 1) had begun. The TO4C increased from 1 to 4 in all animals, in all treatment groups within 10 minutes of reversal. The TO4C was 4 in all animals five minutes after edrophonium, and seven minutes after neostigmine; differences were not statistically significant. The TO4C was significantly higher with edrophonium two and three minutes after antagonism compared with saline. The data show that spontaneous recovery from mivacurium is rapid in sheep, although reversal is accelerated by anticholinesterase drugs.

Immediate and delayed nerve repair using freeze-thawed muscle autografts in complex nerve injuries. Associated arterial injury.

Five sheep underwent repair of the median nerve along with the establishment and repair of a brachial artery defect adjacent to the site of nerve injury. The defect in the brachial artery was of similar length to the nerve defect and lay in parallel with it. It was repaired using a reversed vein autograft harvested from one of the superficial veins of the arm. A further five sheep underwent similar treatment with the repair of the nerve delayed for 30 days after the establishment of the complicating vascular injury. Six months after the nerve repair, each group of sheep was assessed using electrophysiological and morphometric methods in order to establish objective indices of nerve recovery and regeneration. These results were compared with those from other sheep which had undergone nerve repair both immediate and delayed with no complicating injury and groups in which the complicating injury consisted of a cavity, fibrosis and haematoma. It was found that delay in the nerve repair and the presence of a complicating arterial injury, both separately and additively, contributed to a poorer outcome in recovery of nerve function and maturation. The effect of an arterial injury, in both of these respects, was to produce a worse outcome than the presence of a cavity with fibrosis and haematoma.

Immediate and delayed nerve repair using freeze-thawed muscle allografts. Associated long-bone fracture.

Six sheep underwent repair of the median nerve in the forearm using freeze-thawed muscle autografts, along with the establishment and repair of a "fracture" adjacent to the site of nerve injury. The "fracture" was created by making a transverse osteotomy of the radius. It was repaired using an 8-hole dynamic compression plate. A further six sheep underwent similar treatment with the repair of the nerve delayed for 30 days after the establishment of the long-bone injury. Six months after the nerve repair, each group of sheep was assessed using electrophysiological and morphometric methods in order to establish objective indices of nerve recovery and regeneration. It was found that delay of the nerve repair and the presence of a complicating long-bone injury, both separately and additively, contributed to a poorer outcome in recovery of nerve function and maturation.

Changes in muscle cytoarchitecture after peripheral nerve injury and repair. A quantitative and qualitative study.

The aim of this study was to assess the changes which occurred in the rat in target muscles after the injury and repair of a specific peripheral nerve, using several clinically-appropriate surgical techniques. There were alterations in the size, shape, morphology and cytochemical architecture of the fibres of the target muscles. These changes were marked when transection and repair of the nerve was compared with the less-severe crush injury. The method of repair did not correlate significantly with the occurrence of changes in muscle cytoarchitecture. The results suggest that the extent of cell loss and the changes in muscle fibre architecture were influenced by the type of injury, rather than by the method of repair.

In vitro nerve repair--in vivo. The reconstruction of peripheral nerves by entubulation with biodegradeable glass tubes--a preliminary report.

Biodegradeable "controlled release" inorganic polymer glass tubes can be manufactured to fit the dimensions of any nerve and their rate of solubility can be adjusted to encompass the time taken for nerve regeneration. They have been used in a number of biological applications. The facial nerve was repaired in a group of five sheep by entubulation with biodegradeable glass tubes. The sheep were assessed 10 months after repair and compared with a similar sized group of normal sheep. It was found that while there was a reduction in the peak velocity of conduction in the repaired nerves and in the range of conduction velocities, the minimum conduction velocity was within normal limits. There was a diminution in all of the measured variables of nerve morphometry but in no case did this reach statistical significance. These findings are consistent with the view that regeneration of the nerves had taken place to a degree at least as effective as that seen in nerves of a similar size repaired by conventional means.