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Biomedical subjects

S E Mackinnon

Publications and source records attributed to S E Mackinnon.

At least 199 records · Page 11Linked to original sources
PubMed1988

Comparison of regeneration across a vascularized versus conventional nerve graft: case report.

A histological and functional comparison of regeneration across a vascularized and conventional nerve graft was carried out in a clinical case. The two branches of the medial antebrachial cutaneous nerve were used to neurotize the median nerve at the wrist. The superficial branch of the radial nerve (vascularized nerve graft) and a conventional sural nerve graft were used as the interposition grafts between the two branches of the medial antebrachial cutaneous nerve and the median nerve. This nerve grafting procedure was carried out in two stages. The proximal neurorrhaphy was carried out 7 months prior to the distal nerve repair. Biopsies were taken from the distal portions of the vascularized radial sensory nerve and the conventional sural nerve at the time of the second procedure. Histological evaluation demonstrated superior regeneration across the vascularized nerve graft. Subjectively, the patient described better sensory recovery in the territory innervated by the vascularized nerve graft. Sensory testing in the two territories demonstrated better sensibility in the territory innervated by the vascularized nerve graft.

Adult↗
PubMed1988

Complications of soft tissue expansion.

This paper presents a critical review of the results of tissue expansion in our clinical experience. Seventy-six expansions performed in 66 patients between 1981 and August 1986 are included in the study. Complications necessitating some revision in the original treatment plan were documented in 39% of cases. However, sufficient tissue was usually generated to complete the proposed reconstruction without compromising the final results. The complications of tissue expansion are further analysed in relation to their anatomical distribution, time of onset and ultimate consequences. Causative factors are identified and preventative measures are introduced.

Adolescent↗
PubMed1988

A comparison of nerve regeneration across a sural nerve graft and a vascularized pseudosheath.

Nerve regeneration across a vascularized pseudosheath and a sural nerve graft was compared in a primate model using histologic and electrophysiologic parameters for regeneration. At 12 months, regeneration was noted across both the vascularized pseudosheath and the sural nerve graft. Although histologic and electrophysiologic properties of the regenerated nerve were significantly different from the normal ulnar nerve, the quality of regeneration noted between experimental groups was similar.

Animals↗
PubMed1988

Evaluation of microsurgical internal neurolysis in a primate median nerve model of chronic nerve compression.

This study evaluates the effect of internal neurolysis on a chronically compressed primate median nerve as compared with a simple decompression procedure. In 11 adult, cynomologous monkeys, the median nerve in the carpal tunnel was banded with a silicone tube. After 6 months of nerve compression (mild to moderate compression in our model) in eight monkeys, a microneurosurgical internal neurolysis was carried out on the median nerve of one hand and a simple decompression (removal of band) was carried out on the median nerve of the other hand. Histologic, morphologic, and electrophysiologic evaluation was carried out 6 months later. Six control animals were similarly evaluated after 0, 6, and 12 months of nerve compression. The degree of compression produced was not severe in that it did not cause Wallerian degeneration. Histologic and electrophysiologic improvement was produced in both treatment groups over the two chronically compressed groups (6 and 12 months of compression). While internal neurolysis did not cause intraneural scarring or nerve fiber damage as compared with simple decompression alone, there was no difference noted between the effects of these two treatment methods on the chronically compressed nerve.

Animals↗
PubMed1988

Human ulnar neuropathy at the elbow: clinical, electrical, and morphometric correlations.

This study explored and compared clinical, electrodiagnostic, and morphometric observations on bilateral ulnar nerves obtained at necropsy in a patient with severe bilateral ulnar compression neuropathy at the elbow. There was excellent correlation among all three evaluation techniques. On the patient's more symptomatic side, there was significant slowing of conduction velocity across the elbow, with sensory conduction unobtainable in the little finger. Morphometric results demonstrated loss of myelin, decreased nerve fiber diameter, and reduction in percent of neural tissue present in the compressed elbow segment of the ulnar nerve.

Aged↗
PubMed1988

Susceptibility of the diabetic nerve to chronic compression.

This study tested the hypothesis that the peripheral nerve in the presence of diabetes is more susceptible to chronic nerve compression than it is in the nondiabetic rat. A 1-cm length of sciatic nerve was subjected to chronic compression by banding with a Silastic tube in normal and in streptozotocin-induced diabetic rats. After six months of banding, both the amplitude and conduction velocity of the diabetic banded sciatic nerve were significantly reduced (p less than 0.001) in comparison with the nondiabetic banded rats. These results suggest that in the presence of hyperglycemia, the peripheral nerve is more susceptible to chronic compression.

Animals↗
PubMed1988

Anatomic investigations of nerves at the wrist: I. Orientation of the motor fascicle of the median nerve in the carpal tunnel.

The orientation of the motor fascicle of the median nerve in the carpal tunnel was investigated in dissections of 50 hands. Topographically, the motor branch was located on the radial-volar aspect of the median nerve in 60% of the hands, the central-volar aspect in 22%, and between these two locations in the remaining 18%. In 56% of the hands, the motor branch passed through a separate distinct fascial tunnel before entering the thenar muscles. Awareness of these patterns will facilitate appropriate surgical management of thenar muscle weakness or wasting associated with the carpal tunnel syndrome.

Humans↗
PubMed1988

Anatomic investigations of nerves at the wrist: II. Incidence of fibrous arch overlying motor branch of ulnar nerve.

The incidence of fibrous arch overlying the motor branch of the ulnar nerve as it passes beneath the origin of the hypothenar muscles in Guyon's canal was investigated in dissections of 50 hands. Forty percent of the hands had a fibrous edge to the flexor digiti minimi muscle. The fibrous edge was a mean of 2 mm in width (range, 1-6 mm). Awareness of this fibrous arch will facilitate appropriate surgical management of ulnar-innervated intrinsic muscle weakness or wasting associated with ulnar compression at the wrist.

Fibrosis↗
PubMed1988

An assessment of the effects of internal neurolysis on a chronically compressed rat sciatic nerve.

Chronically compressed nerves were treated with three surgical modalities. Simple decompression was compared to internal neurolysis with and without the addition of extrafascicular steroid. Electrophysiologic, histologic, and morphometric assessments were performed. Compressed control nerves demonstrated changes compatible with severe nerve compression (Wallerian degeneration). With simple decompression, improvement in histologic and electrophysiologic parameters occurred. When internal neurolysis was added to the decompression, further improvement in histologic and electrophysiologic parameters was noted. There was no added improvement with the addition of steroids.

Animals↗
PubMed1988

The peripheral nerve allograft: a dose-response curve in the rat immunosuppressed with cyclosporin A.

The potential use of peripheral nerve allografts would significantly improve the reconstructive potential for patients with major peripheral nerve deficits. This study evaluated the response of the nerve allograft recipient treated with varying dosages of cyclosporin A (CsA) to determine the minimal effective dosage necessary to prevent nerve graft rejection. Lewis rats (RT1l) were the recipients of syngeneic nerve grafts from identical Lewis donors or allogeneic nerve grafts from ACI (RT1a) donors. Nerve grafts were inlaid next to the intact sciatic nerve of the recipient. The immunologic responsiveness of the recipient animal's lymphocytes to a donor-specific antigenic challenge was assessed by the mixed lymphocyte reaction (MLR). In addition, nerve grafts were evaluated histologically. Animals were monitored for cyclosporin A toxicity. It was found that cyclosporin A (5 mg/kg per day) was effective in rendering the recipient animals unresponsive by mixed lymphocyte reaction at 10, 20, and 40 days after engraftment. This dosage was similarly effective in preventing histologic changes characteristic of nerve allograft rejection. This dosage regimen was nontoxic to the animals. Our study ascertained a minimal nontoxic dosage of cyclosporin A that effectively prevented nerve allograft rejection across a major histocompatibility disparity in rats.

Animals↗
PubMed1988

An alternative to the classical nerve graft for the management of the short nerve gap.

Reconstruction of a short nerve gap by a nerve graft produces donor-site scarring, loss of donor nerve function, and neuroma formation. This study compared the regeneration achieved after 1 year in 16 monkeys across a 3-cm upper arm ulnar nerve gap with a bioabsorbable polyglycolic acid nerve conduit with the regeneration achieved with a classical interfascicular interpositional sural nerve graft. The results demonstrated electrophysiologic and histologic evidence of neural regeneration across the gaps in all experimental groups. The bioabsorbable nerve conduit groups and the sural nerve graft group had mean fiber diameters, amplitudes, and conduction velocities each significantly less than those of normal control ulnar nerves. There was, however, no significant difference between any of the experimental groups. Electromyography demonstrated recovery of 19 of the 28 (68 percent) intrinsic muscles studied. These results demonstrate that the primate peripheral nerve can regenerate across short nerve gaps when guided by an appropriate nerve conduit, suggesting that a single-stage biodegradable polyglycolic acid conduit may be used as an alternative to a short interfascicular nerve graft.

Anastomosis, Surgical↗
PubMed1988

The peripheral nerve allograft: an assessment of regeneration across nerve allografts in rats immunosuppressed with cyclosporin A.

Lewis rats (RT1(1] were the recipients of 3-cm nerve grafts from syngeneic Lewis donors or allogeneic ACI (RT1a) donors. Microneurosurgical repair of the nerve graft to the transected sciatic nerve of the recipient animal was performed with 10-0 epineurial sutures. Recipients were randomly allocated to cyclosporin A (CsA) immunosuppressed or untreated groups. Cyclosporin A was administered in the minimal effective dosage to prevent nerve allograft rejection across this major histocompatibility disparity (5 mg/kg per day). Nerve regeneration across the nerve grafts was assessed by sciatic function index (SFI) and toe spread index (TSI) determinations serially and by electrophysiologic, histologic, and morphologic assessments 14 weeks after engraftment. Sciatic nerve regeneration across allogeneic nerve grafts in cyclosporin A immunosuppressed recipients was significantly superior compared to the untreated controls (p less than 0.008) and not significantly different from that across the syngeneic control animals.

Animals↗