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Biomedical subjects

S E Mackinnon

Publications and source records attributed to S E Mackinnon.

At least 163 records · Page 9Linked to original sources

Evaluation of digital prostheses.

Fifty-one digital prostheses were made for 33 patients between 1986 and 1988. A questionnaire was developed to assess the patients' satisfaction with these prostheses and was administered 6 months and 3 years after the prostheses were made. The majority of patients requested prostheses for esthetic reasons. While they reported satisfaction with the appearance of the prostheses, at 3 years 36% of the patients no longer continue to use the prostheses.

Adult↗

Intraneural anatomy of the median nerve provides "third web space" donor nerve graft.

To determine the feasibility of using the fascicular group to the third web space as a source of nerve graft material for bridging of median nerve gaps, a study of the intraneural anatomy of the median nerve was carried out in 23 fresh cadaver specimens. The pattern of plexus formation between the third web-space group and the remainder of the median nerve was determined. The average length of the third web-space fascicular group that could be separated from the median nerve proper prior to plexus intermingling was 24.5 cm. Cross-sectional areas of the graft and the remaining nerve were 4.43 mm2 and 13.76 mm2, respectively. The number of nerve fibers in the third web-space group was 4,847 and in the remaining median nerve, 13,486. Between February, 1989 and October, 1991, this technique has been used on 11 patients to provide donor nerve material for nerve gaps of 3 to 6 cm in the median nerve.

Adolescent↗

A technique for the treatment of neuroma in-continuity.

A surgical technique for the management of a neuroma in-continuity, in which motor function is preserved and sensory function is reconstructed with nerve grafting, is presented. Tedious and potentially damaging dissection within the neuroma in-continuity is avoided. The functioning motor fascicles are identified proximal and distal to the injury site with electrical nerve stimulation eliciting muscle contraction. These motor fascicles are preserved. The electrically silent and nonfunctioning sensory fascicles are divided proximal and distal to the neuroma and reconstructed with autogenous nerve grafts. These nerve grafts bypass the functioning motor portion of the neuroma in-continuity.

Adult↗

Verification of the pressure provocative test in carpal tunnel syndrome.

Three provocative tests (pressure, Phalen's test, and Tinel's sign) were studied in 30 patients with carpal tunnel syndrome and 30 control subjects. The pressure provocative test had a sensitivity of 100%. In contrast, Phalen's test was 88% sensitive and Tinel's sign only 67% sensitive. The pressure provocative test is a sensitive indicator of median nerve compression at the wrist with a faster reaction time than Phalen's test (mean time of 9 seconds vs 30 seconds). It is an appropriate provocative test in patients with stiff or painful wrists when wrist flexion is restricted.

Adult↗

Clinical application of peripheral nerve transplantation.

Surgical reconstruction of extensive peripheral nerve injuries frequently exhausts the patient's own source of expendable autogenous nerve grafts. Nerve allografts would offer a limitless supply of graft material. A 23-cm, 10-cable sciatic nerve allograft was performed in an 8-year-old boy in September of 1988. The patient was managed with Cyclosporin A for 2 years. Forty-four months after the transplant surgery and 19 months after the cessation of Cyclosporin A therapy, the patient has evidence of nerve regeneration across the allograft with recovery of functional sensibility in his foot. In the selected patient with an otherwise irreparable nerve injury, consideration can be given to the use of a nerve allograft.

Child↗

The peripheral nerve allograft in the primate immunosuppressed with Cyclosporin A: I. Histologic and electrophysiologic assessment.

Nerve regeneration across peripheral nerve allografts and control autografts in primates immunosuppressed with Cyclosporin A was quantitatively evaluated by electrophysiologic and histologic methods. Twelve cynomolgus monkeys received 3-cm autografts and allografts in contralateral ulnar nerves. They were immunosuppressed with Cyclosporin A at 25 mg/kg per day or placebo vehicle. Morphometric analysis of nerve graft and distal nerve segments was assessed at 1 year after engraftment. Quantitative electrophysiologic studies were performed percutaneously at 6 and 12 months, and compound action potentials were measured directly across the nerve grafts at 1 year. Excellent regeneration was seen across autografts and allografts in Cyclosporin A-treated and placebo-treated recipients.

Action Potentials↗

The peripheral nerve allograft in the primate immunosuppressed with Cyclosporin A: II. Functional evaluation of reinnervated muscle.

Isometric contractile function was evaluated in primates receiving peripheral nerve allografts and autografts. Twelve adult male cynomolgus monkeys received both sural nerve allografts and autografts to the ulnar nerve in opposite forearms. Half the animals received Cyclosporin A (CsA) immunosuppression (25 mg/kg per day); the remaining animals received placebo. One year following nerve engraftment, isometric contractile muscle function was evaluated in reinnervated abductor digiti quinti and intact abductor pollicis brevis muscles. Maximal twitch tension (Pt), tetanic tension (P(o)), time to peak tension (tpt), rate of rise of twitch tension (DP/dt), and muscle fatigue were evaluated at optimal muscle length (L(o)). All reinnervated muscles distal to nerve autografts and allografts in both Cyclosporin A-immunosuppressed and placebo-treated animals generated equivalent maximal twitch tension, tetanic tension, and time to peak tension, with no significant difference between groups (p > 0.05 by ANOVA). There was a tendency toward increased muscle fatiguability in Cyclosporin A-treated animals (p > 0.05). However, the rate of rise of twitch tension was significantly faster in the reinnervated and intact muscles of Cyclosporin A-treated primates (p < 0.05). Evidence of excellent functional reinnervation across nerve allografts and autografts similar to that seen in histologic and electrophysiologic studies was noted. Cyclosporin A immunosuppression did not significantly enhance recovery of muscle function distal to nerve allografts in this model.

Animals↗

Double and multiple "crush" syndromes. Double and multiple entrapment neuropathies.

The double crush hypothesis suggests that serial constraints to axoplasmic flow, each of which is insufficient to cause changes in function by itself, can be additive in causing ultimate dysfunction of the nerve. Careful clinical examination will be required to localize the significant levels of nerve compression. Frequently, patients will be asymptomatic in the nonprovoked position. A comparison of neurological testing "at rest" and then subsequent to provocation of the patient's symptoms may be the only mechanism by which the surgeon will be able to quantity an abnormality that corresponds to the patient's symptoms. Surgical intervention, especially when the etiologic factor is work-related, is always postponed until maximum job modification has been carried out. Surgical management of these patients without a significant change in the patient's work habits that provoked the compression neuropathies in the first instance will frequently be associated with a recurrence of symptoms when the work is resumed.

Chronic Disease↗

Strain differences in autotomy in rats undergoing sciatic nerve transection or repair.

The degree of self-mutilation (autotomy) following sciatic nerve injury was assessed in 6 rat strains. Experimental groups included sciatic nerve transection with and without repair and crush lesions. The degree of autotomy was measured using a standard grading system. There were statistically significant differences between the strains in the transected group in terms of both degree of autotomy and the time of onset of its appearance. The repair group showed a shorter mean time of onset, lower maximal scores, and lower percentage of affected animals. Autotomy was absent in the nerve crush group and in all Lewis rats. In experimental studies when the status of the foot is critical (e.g., to evaluate functional walking patterns) Lewis rats appear to be the most appropriate strain to utilize. These results suggest that there are definite strain differences in the degree of autotomy following nerve transection or repair.

Animals↗

Walking track analysis: a long-term assessment of peripheral nerve recovery.

Functional recovery following sciatic, tibial, and peroneal nerve injury was assessed over a 1-year period using walking track analysis in the rat. Internal neurolysis did not affect nerve function. Crush injury induced a temporary, but complete, loss of function that recovered to control levels by 4 weeks. Nerve transection resulted in complete loss of function without any evidence of recovery. After nerve repair, functional recovery occurred, reaching near-optimal recovery by 12 weeks. The degree of functional recovery varied with the specific nerve involved. The sciatic nerve recovered 41 percent of function, whereas the tibial nerve recovered 54 percent of function. The peroneal nerve exhibited the highest degree of recovery, achieving functional levels similar to control values. Assessment of neural regeneration using walking track analysis appears to be a valuable addition to the traditional methods of histology and electrophysiology.

Analysis of Variance↗

Selective reinnervation: a comparison of recovery following microsuture and conduit nerve repair.

Selective reinnervation was studied by comparing the regeneration across a conventional neurorraphy versus a conduit nerve repair. Lewis rats underwent right sciatic nerve transection followed by one of four different nerve repairs (n = 8/group). In groups I and II a conventional neurorraphy was performed and in groups III and IV the proximal and distal stumps were coapted by use of a silicone conduit with an interstump gap of 5 mm. The proximal and distal stumps in groups I and III were aligned anatomically correct and the proximal stump was rotated 180 degrees in groups II and IV (i.e. proximal peroneal nerve opposite the distal tibial nerve and the proximal tibial nerve opposite the distal peroneal nerve). By 14 weeks, there was an equivalent, but incomplete return in sciatic function index (SFI) in groups I, III, and IV as measured by walking track analysis. However, the SFI became unmeasurable by 6 weeks in all group II animals. At 14 weeks, the percent innervation of the tibialis anterior and medial gastronemius muscles by the peroneal and tibial nerves respectively was estimated by selective compound muscle action potential amplitude recordings. When fascicular alignment was reversed, there was greater tibial (P = 0.02) and lesser peroneal (P = 0.005) innervation of the gastrocnemius muscle in the conduit (group IV) versus the neurorraphy (group II) group. This suggests that the gastrocnemius muscle may be selectively reinnervated by the tibial nerve. However, there was no evidence of selective reinnervation of the tibialis anterior muscle. Despite these differences, the functional recovery in both conduit repair groups (III and IV) was equivalent to a correctly aligned microsuture repair (group I) and superior to that in the incorrectly aligned microsuture repair (group II).

Action Potentials↗

Inter- and intraobserver reliability of walking-track analysis used to assess sciatic nerve function in rats.

The inter- and intraobserver reliability of the walking-track analysis of sciatic nerve function in the rat was assessed. Twenty-five walking tracks were assessed on three different occasions by four observers. Whereas the interobserver reliability was found to be excellent (r = 0.92), the intraobserver reliability was only satisfactory (r = 0.53 to r = 0.76). Walking-track analysis provides a noninvasive technique to assess function recovery in the rat, with excellent intraobserver reliability demonstrated. The lower intraobserver reliability suggests limitations to this new measurement technique.

Animals↗

Changes in nerve fiber numbers distal to a nerve repair in the rat sciatic nerve model.

Changes in nerve fiber numbers distal to a nerve repair in the sciatic nerve of 48 rats were evaluated over a 1- to 24-month period. The results of the morphometric evaluation in the sciatic nerve distal to the nerve repair demonstrated an increase in nerve fiber counts as early as 1 month following the nerve repair. The number of nerve fibers in the distal nerve was greatest at 3 months and did not return to normal levels until 24 months. The results of this study will influence the timing of experimental studies in which nerve fiber counts are critical for evaluation, and provides a better understanding of the clinical events occurring following nerve repair.

Animals↗

Internal neurolysis fails to improve the results of primary carpal tunnel decompression.

This prospective, randomized study compares two treatment methods in patients with primary carpal tunnel syndrome. Decompression of the transverse carpal ligament was done in thirty-two hands (thirty patients) and decompression of the transverse carpal ligament with the addition of an internal neurolysis of the median nerve was done in thirty-one hands (twenty-nine patients). Relief of symptoms was described in eighty-eight percent of the patients with carpal ligament release and eighty-one percent of patients with carpal ligament release plus internal neurolysis. Improvement in hand sensibility testing, in thenar muscle strength, and atrophy was noted in both treatment groups with no statistical difference between groups. The addition of an internal neurolysis to division of the transverse carpal ligament does not add significant improvement in the sensory or motor outcome of patients with primary carpal tunnel syndrome.

Carpal Tunnel Syndrome↗

Results of posterior tibial nerve grafting at the ankle.

The results of interfascicular interposition nerve grafting for posterior tibial nerve deficit at the ankle are reported for eight patients. The sural nerve was the donor nerve in all cases. Mean age at injury was 36.3 years (range 22 to 50 years). Mean postoperative follow-up is 5.0 years (range 2.25 to 8.0 years). In five of the patients, the primary indication for nerve grafting was pain or numbness in degree sufficient to consider amputation. Mean graft length was 9.8 cm (range 4 to 18 cm). After grafting, all eight patients ambulate without assistive devices and are productively employed or have resumed pre-injury household activities. All patients received postoperative sensory re-education. Sensory recovery has been to S4 level in two, to S3+ in four, and to S3 in two. There have been no foot ulcerations. It is concluded that grafting the posterior tibial nerve is indicated for the treatment of pain and recovery of sensation in carefully selected patients, and is capable of predictability restoring at least some touch sensibility.

Adult↗