Neurophysiological studies of autogenous sural nerve grafts

Anatomical variations in the cutaneous innervation on the dorsum of the foot

Generally among the branches of common peroneal nerve, the superficial peroneal nerve provides cutaneous innervation to major part of the dorsum of the foot whereas the deep peroneal nerve innervates the skin over the first interdigital cleft region. The sural and saphenous nerves supplies the smaller lateral and medial margins of the dorsum respectively. The present study has been taken to classify the patterns of innervations of the nerves on the dorsum of the foot in South Indian population. A total of 40 formalin fixed lower limbs from 20 adult cadavers (15 males, 5 females) aged between 35 to 60 years were dissected and the branching patterns of nerves on the dorsum of the foot were noted and specimens were photographed. Gross anatomical variations were noted in the branching pattern of superficial peroneal, deep peroneal and sural nerve on the dorsum of foot. Results obtained in our study were classified into four groups. The cutaneous nerves are at risk of iatrogenic injuries during surgeries involving ankle, open reduction and internal fixation of fracture, arthroscopy etc. Knowledge of such anatomical variations of the nerves provides information to clinicians to avoid injury to them in real clinical situations.

Median and ulnar nerve injuries: a meta-analysis of predictors of motor and sensory recovery after modern microsurgical nerve repair

BACKGROUND

The aim of this study was to quantify variables that influence outcome after median and ulnar nerve transection injuries. The authors present a meta-analysis based on individual patient data on motor and sensory recovery after microsurgical nerve repair.

METHODS

From 130 studies found after literature review, 23 articles were ultimately included, giving individual data for 623 median or ulnar nerve injuries. The variables age, sex, nerve, site of injury, type of repair, use of grafts, delay between injury and repair, follow-up period, and outcome were extracted. Satisfactory motor recovery was defined as British Medical Research Council motor scale grade 4 and 5, and satisfactory sensory recovery was defined as British Medical Research Council grade 3+ and 4. For motor and sensory recovery, complete data were available for 281 and 380 nerve injuries, respectively.

RESULTS

Motor and sensory recovery were significantly associated (Spearman r = 0.62, p < 0.001). Multivariate logistic regression analysis showed that age (< 16 years versus > 40 years: odds ratio, 4.3; 95 percent confidence interval, 1.6 to 11.2), site (proximal versus distal: odds ratio, 0.46; 95 percent confidence interval, 0.20 to 1.10), and delay (per month: odds ratio, 0.94; 95 percent confidence interval, 0.90 to 0.98) were significant predictors of successful motor recovery. In ulnar nerve injuries, the chance of motor recovery was 71 percent lower than in median nerve injuries (odds ratio, 0.29; 95 percent confidence interval, 0.15 to 0.55). For sensory recovery, age (odds ratio, 27.0; 95 percent confidence interval, 9.4 to 77.6) and delay (per month: odds ratio, 0.92; 95 percent confidence interval, 0.87 to 0.98) were found to be significant predictors.

CONCLUSIONS

In this individual patient data meta-analysis, age, site, injured nerve, and delay significantly influenced prognosis after microsurgical repair of median and ulnar nerve injuries.

Regeneration of Peripheral Nerve Gaps with a Polyglycolic Acid-Collagen Tube

OBJECTIVE:

The aim of this study was to report by means of objective methods on the effectiveness of a nerve reconstruction procedure using a bioresorbable tube in two patients. Our previous successes in regenerating canine peripheral nerves across long distances (80-mm gaps) using a bioabsorbable tube have led us to investigate the value of such a tube for the treatment of human patients with chronic nerve injuries.

METHODS:

The device was made from a cylindrically woven polyglycolic acid tube filled with a collagen sponge. It was designed to be resorbed after nerve regeneration. Peripheral sensory nerve defects in two patients with neuroma and pain were reconstructed using this tube. Patient 1 (a 62-year-old man) had a 20-mm defect of the proper digital nerve, and Patient 2 (a 56-year-old woman) had a 65-mm defect of the superficial peroneal nerve.

RESULTS:

After surgery, both patients recovered from the unpleasant sensations and intolerable pain. In Patient 1, functional recovery was objectively identified at 2 months, and conduction velocity of the nerve recovered to 49.1 m/s. In Patient 2, conduction velocity of the nerve was determined to be 16.9 m/s at 5 months. Current perception threshold testing indicated that sensory nerve function had been recovered by 65 days after surgery.

CONCLUSION:

This work represents the first precise clinical evaluation, performed under objective evaluation criteria, of sensory recovery achieved using a nerve tube, suggesting that the use of a polyglycolic acid-collagen tube has the potential to become a viable alternative to conventional autografting for the repair of peripheral nerve defects.

The harvest and clinical application of the superficial peroneal sensory nerve for grafting motor and sensory nerve defects

Potential donor nerves for autografting are finite and usually limited to cutaneous nerves of the extremities. The superficial peroneal nerve is the major lateral branch of the common peroneal nerve that innervates the peroneus longus and brevis muscles and provides sensation to the lateral aspect of the lower leg and the dorsal foot. It has generally been overlooked as a potential donor of nerve autografts. Cadaver dissections were performed on 10 fresh lower extremity specimens to investigate the anatomic characteristics of the superficial peroneal nerve and to refine a harvesting technique for the nerve. Thirty-one patients underwent nerve grafting of 39 upper and lower extremity nerves using the superficial peroneal donor. There were nine median nerves, four ulnar nerves, two radial nerves, two brachial plexus lesions, 16 digital nerves, and six lower extremity nerves grafted. The superficial peroneal nerve provided a consistently long donor, comparable in length to the sural nerve. The anatomic pattern is consistent, the patient positioning is simple, the surgical harvesting technique is straightforward, and the donor defect is acceptable. The superficial peroneal nerve provides a safe and valuable donor nerve, particularly in cases where multiple or very long nerve grafts are required.

Evaluation of clinical, electrophysiologic, and computed tomographic parameters in replanted hands

OBJECTIVE

To compare clinical, electrophysiologic, and computed tomography (CT) imaging correlates of reinnervation in replanted limbs.

DESIGN

Patients were assessed between 8 and 194 months after replantation of completely severed hands.

SETTING

University hospital, departments for neurology and for plastic and reconstructive surgery.

PARTICIPANTS

Thirteen patients, 10 with total and 3 with subtotal type V amputation, whose hands had been reattached.

INTERVENTIONS

Clinical assessment of function of hand and finger muscles; electromyographic tests of sensory nerve action potentials (SNAPs) of median, ulnar, and radial nerves; and compound motor action potentials (CMAPs) of abductor pollicis brevis, first dorsal interosseus, and abductor digiti minimi muscles. CT assessment of motor unit action potentials. Measurements of both replanted and normal hands.

MAIN OUTCOME MEASURES

Medical Research Council scale of force; sensory functions of anatomic areas of nerves; SNAP and CMAP amplitudes; CT area, mean absorption, standard deviation (SD) from mean absorption, and root mean square SD of absorption.

RESULTS

Correlates of reinnervation were evidenced by all methods, except by surface recordings of SNAPs, which could not be elicited even in hands with good sensory function. CMAP amplitudes were the electrophysiologic parameter that correlated best with the clinical restoration. Of the CT measures, the cross-sectional area was the most useful parameter for the detection of denervation, but no CT parameter was sufficiently sensitive to detect reinnervation. In cases with good functional recovery, CMAP amplitudes were superior to clinical rating in showing incomplete reinnervation.

CONCLUSION

The combination of clinical and electrophysiologic methods supplied sufficient data for a reliable evaluation of reinnervation. Usually, CT parameters did not add useful information.

Conduction study of digital nerve function recovery following toe-to-digit transplantation and a comparison with digit-to-digit replantation

Recovery of digital nerve function following toe-to-digit transplantation was studied by nerve conduction in 16 patients, and a comparison was made with digit-to-digit replantation in 7 patients. For toe transplantation and digit replantation, the mean interval between injury and surgery was 7 months and 8 h, respectively, while the mean interval between surgery and study was 39 months and 25 months, respectively. Sensory nerve action potentials (NAPs) from digital nerve stimulation were recorded at the wrist and the elbow, whereas mixed NAPs from median nerve stimulation at the wrist were recorded at the elbow. Sensory NAPs from stimulation of the transplanted toe were detectable in 14 patients and showed reduced amplitude, prolonged latency, and slowed conduction velocity. There was retrograde amplitude reduction in the median nerve and in the proximal segment of the digital nerve. Sensory NAPs from the replanted digit were not different from those of the normal digit, nor was a retrograde effect observed. The present data indicate that digital nerve function recovery was incomplete in toe transplantation and nearly complete in digit replantation. The reasons for the differences in recovery following two types of nerve repair are discussed.

Group fascicular vein grafts with interposition of nerve slices for long ulnar nerve defects: report of three cases

Group fascicular vein grafts with interposition of nerve slices were designed for reconstruction of three ulnar nerves with defects of 2.5-4.5 cm. The veins were taken from superficial veins in the forearm and reversed to bridge the fascicles in both stumps. Normal nerve slices were sectioned from fascicles in the proximal stump and inserted inside the corresponding vein conduits. Postoperatively, the Tinel's sign was detected across the vein conduits, and electromyography showed reinnervation of intrinsic muscles of the hands. Follow-up for more than 2 years revealed motor recovery to M4 and sensory recovery to S3-S4 in these three cases. This technique may be a promising alternative to group fascicular nerve grafting for long defects in peripheral nerve trunks.

Sensory recovery after median nerve grafting

Fourteen patients were evaluated prospectively after median nerve grafts. Twelve male and two female patients with a mean age of 41 years were included. Mean time since surgery was 4 years. Detailed sensory evaluations were completed. Statistical evaluation analyzed relationships between object identification, sensory tests, and graft length. According to the S-0 to S-4 grading system, 11 patients were considered to be S-3+ or greater. Recovery of moving two-point discrimination of 2 to 3 mm. was achieved by 50% of the patients. Strong correlations were found between object identification and static two-point discrimination, moving two-point discrimination, and graft length. Cutaneous pressure threshold and vibration threshold correlated weakly with object identification.

Electrophysiological studies of various graft lengths and lesion lengths in repair of nerve gaps in primates

Electrophysiological studies were used to evaluate neurological recovery in 14 rhesus monkeys with different nerve lesion lengths and graft lengths. After exposure of both sciatic nerves in each animal, baseline evoked nerve action potentials, muscle action potentials, and muscle strength values were determined for the posterior tibial nerves. Each nerve was then crushed over a measured distance. Three weeks later, the crushed segments were resected and the defects repaired with sural nerve grafts. In seven animals, 20-mm resection sites were repaired by 4 x 20-mm grafts in one leg and by 4 x 40-mm grafts contralaterally. In the other seven animals, the lengths of resection sites were 10 mm in one leg and 30 mm contralaterally; both nerve defects in these animals were repaired by 4 x 30-mm grafts. Electrophysiological studies were repeated at one interval of either 4, 7, or 12 months after repair. Postoperative electrophysiological values were compared to baseline values and described by the mean values and by percent recovery. Muscle strength recovery was significantly better in limbs with short lesions. In animals with identical lesion lengths, lesions repaired with shorter grafts (the same length as the defect) did significantly worse than did lesions repaired with longer grafts. This may suggest that any degree of tension at the graft repair site has a deleterious effect on functional nerve regeneration. Nevertheless, it was generally found that nerve lesion length had the greatest negative effect on functional nerve regeneration.

Human cutaneous mechanoreceptors during regeneration: physiology and interpretation

Percutaneous microneurography was used to record activity from single cutaneous afferents reinnervating the glabrous skin of the hand. Recordings were obtained from 6 months to 10 years after complete transsection of the median and/or ulnar nerves with subsequent repair. Transitional properties in the discharge behavior and receptive field characteristics of regenerating afferents were detected during the early stages of regeneration, when axonal maturation was still in progress; these may contribute to the slow time course of sensory recovery. Properties of reinnervated receptors long after nerve repair, when regeneration can be considered complete, indicated a correlation between electrophysiological findings and the final state of clinical recovery. The insights into the neural basis of sensory deficits provided by single-unit microneurography are not yielded by conventional study of the compound action potentials. This technique reveals new information about the pathophysiological nature of peripheral nerve injury and leads to a reinterpretation of clinical deficits.

Sensory electroneurographic parameters and clinical recovery of sensibility in sutured human nerves

A total of 37 patients with traumatic transection of median or ulnar nerves at the wrist (total 41 nerves) were examined clinically and electrophysiologically 4-59 months after primary or secondary suture or grafting. There was a significant increase of cumulative amplitude with the time after suture, whereas maximum sensory nerve conduction velocity and maximum amplitude of nerve action potentials did not reveal such a correlation. The recovery of two-point discrimination, vibration threshold and sensibility scored according to the scale of Nicholson and Seddon were also not related to the passage of time after operation. Though there were significant correlations between cumulative amplitude and both two-point discrimination and recovery of sensibility, electrophysiological parameters were shown to be inadequate predictors of clinical recovery.

Electrophysiological evaluation of cross-face nerve graft in treatment of facial palsy

A cross-face autogenous single graft was performed in eight patients with facial palsy. Several electrophysiological techniques have been used in a follow-up study of one to three years' duration. Clinical results are extremely disappointing. The only recovery observed could not be ascribed to the graft. The investigations and the motor unit count in the facial muscles led to the conclusion that the surgical technique employed is a failure. The orbicularis oculi muscle in particular has no chance whatsoever of being satisfactorily reinnervated. Various reasons for this poor recovery are analysed: too small a number of properly grafted axons, syncinesis, muscle degeneration and poor myelination. These observations nevertheless suggest some experimental fields which may lead to improvements in the technique to a point where it may become clinically useful.

Light- and electron microscopic findings in the distal end of human cross-face sural nerve grafts

In five patients with long-standing facial palsy we have tried to improve the possibility of elevating the angle of the mouth by bringing regenerating axons from the facial nerve on the normal side through a sural nerve graft to a transplanted free muscle in the paralyzed cheek. In order to expect clinical improvement a sufficient number of axons must grow into and through the sural nerve graft, neuromuscular contacts must be formed, and the transplanted muscle must be vascularized and survive. In order to find out if axons had regenerated, light- and electronmicroscopic examinations of a biopsy from the tip of the sural nerve graft were carried out at the time of muscle transplantation. All the cases showed a very large number of unmyelinated axons located within the fascicles of the sural nerve graft. A considerable fraction of myelinated axons were, however, present particularly in biopsies removed 12-13 months after the nerve operation. There was also a marked increase in endoneurial collagen and at the very tip a neuroma was present. This investigation thus shows that regeneration of a substantial number of axons had occurred and that they had reached the zone which was surgically sutured to the transplanted muscle. One essential requirement for reinnervation of the transplanted muscle therefore exists in these patients, but the clinical outcome has not yet been evaluated due to the short follow-up period.

Median and ulnar nerve transections treated with microsurgical interfascicular cable grafting with autogenous sural nerve

Interfascicular nerve grafting was used in 37 median and 26 ulnar nerves, all completely transected. In a follow-up period of 2.5 to 5 years, useful motor recovery (M3 or higher) was achieved in 84% of median nerve lesions; in ulnar nerve lesions, useful motor recovery (M2+ or higher) was achieved in 73%. Sensory recovery with some return of two-point discrimination sense was found in 63% of low median and 50% of low ulnar nerve lesions. In the median nerve group, results for patients younger than 20 years of age were significantly better than in older patients. Neurophysiological investigations gave evidence for nerve regrowth through the grafts in all but one patient, although the loss of axons was probably considerable if the amplitudes of sensory potentials were used as a parameter. Grafts of 2.5 to 5 cm in length gave better results than longer grafts, and results for the distal median nerve lesions were superior to those for the distal ulnar nerve lesions. Use of interfascicular nerve grafting techniques for nerve gaps greater than 2.5 cm is recommended.

Nerve conduction, tactile sensibility, and the electromyogram after suture or compression of peripheral nerve: a longitudinal study in man

In three patients sequential studies were performed of sensory and motor conduction after complete section and suture of the median nerve at the wrist and in one patient after partial section of the nerve. The sensory potential evoked by stimuli to digits III and I and recorded proximal to the suture line at the wrist appeared after a delay of three to four months, corresponding to a growth rate of 1.5-2.0 mm per day. From early in the course of regeneration the sensory potential was dispersed in 40 components. In the adult patient the cumulative amplitude increased for two years slowly and thereafter at a two times faster rate. Amplitude and tactile sensibility were normal after 40 months, but the sensory potential was still five times more dispersed than normal. The overall increase in the amplitude of the sensory potentials in children aged 10 and 12 years was three times faster than in adults. In the adults and in the children the maximum sensory conduction velocity was 10-25% of normal. It then increased at 3% per month during the first two years, and thereafter 10 times slower. Forty months after suture in the adults and 13-19 months after suture in the children the conduction velocity had reached 65-75% of normal. The pattern of discrete electrical activity during voluntary effort and the prolonged duration of motor unit potentials indicate persistent enlargement of the reinnervated motor units by peripheral sprouting. The sensory potential recovered five times faster after a compressive nerve lesion than after section and suture as seen in another patient with an affection of the ulnar nerve at the elbow. Normal tactile sensibility was attained 10 times faster than after section and suture. Maximum sensory and motor condution velocity recovered within one year from 60-70% to 80-90% of normal.