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Susan E. Mackinnon

✓ The successful recovery of sensibility across a long peripheral nerve allograft in a 12-year-old boy who sustained a severe posterior tibial nerve injury is reported. The historical clinical experience with nerve allotransplantation is also reviewed. It is concluded that in the carefully selected patient with severe nerve injury, consideration for nerve allotransplantation can be given.

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Susan E. Mackinnon, Brandon Roque and Thomas H. Tung

✓The purpose of this study is to report a surgical technique of nerve transfer to restore radial nerve function after a complete palsy due to a proximal injury to the radial nerve. The authors report the case of a patient who underwent direct nerve transfer of redundant or expendable motor branches of the median nerve in the proximal forearm to the extensor carpi radialis brevis and the posterior interosseous branches of the radial nerve. Assessment included degree of recovery of wrist and finger extension, and median nerve function including pinch and grip strength.

Clinical evidence of reinnervation was noted at 6 months postoperatively. The follow-up period was 18 months. Recovery of finger and wrist extension was almost complete with Grade 4/5 strength. Pinch and grip strength were improved postoperatively. No motor or sensory deficits related to the median nerve were noted, and the patient is very satisfied with her degree of functional restoration.

Transfer of redundant synergistic motor branches of the median nerve can successfully reinnervate the finger and wrist extensor muscles to restore radial nerve function. This median to radial nerve transfer offers an alternative to nerve repair, graft, or tendon transfer for the treatment of radial nerve palsy.

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Susan E. Mackinnon, Andrew Yee and Wilson Z. Ray

Spinal cord injury (SCI) remains a significant public health problem. Despite advances in understanding of the pathophysiological processes of acute and chronic SCI, corresponding advances in translational applications have lagged behind. Nerve transfers using an expendable nearby motor nerve to reinnervate a denervated nerve have resulted in more rapid and improved functional recovery than traditional nerve graft reconstructions following a peripheral nerve injury. The authors present a single case of restoration of some hand function following a complete cervical SCI utilizing nerve transfers.

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Rory K. J. Murphy, Wilson Z. Ray and Susan E. Mackinnon

Complete loss of median nerve motor function is a rare but devastating injury. Loss of median motor hand function and upper-extremity pronation can significantly impact a patient's ability to perform many activities of daily living independently. The authors report the long-term follow-up in a case of median nerve motor fiber transection that occurred during an arthroscopic elbow procedure, which was then treated with multiple nerve transfers. Motor reconstruction used the nerves to the supinator and extensor carpi radialis brevis to transfer to the anterior interosseous nerve and pronator. Sensory sensation was restored using the lateral antebrachial cutaneous (LABC) nerve to transfer to a portion of the sensory component of the median nerve, and a second cable of LABC nerve as a direct median nerve sensory graft. The patient ultimately recovered near normal motor function of the median nerve, but had persistent pain symptoms 4 years postinjury.

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Justin M. Brown, Manish N. Shah and Susan E. Mackinnon

Peripheral nerve injuries can result in devastating numbness and paralysis. Surgical repair strategies have historically focused on restoring the original anatomy with interposition grafts. Distal nerve transfers are becoming a more common strategy in the repair of nerve deficits as these interventions can restore function in months as opposed to more than a year with nerve grafts. The changes that take place over time in the cell body, distal nerve, and target organ after axotomy can compromise the results of traditional graft placement and may at times be better addressed with the use of distal nerve transfers. A carefully devised nerve transfer offers restoration of function with minimal (if any) detectable deficits at the donor site. A new understanding of cortical plasticity along with patient reeducation allow for good return of strength and function after nerve transfer.

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Aaron G. Grand, Terence M. Myckatyn, Susan E. Mackinnon and Daniel A. Hunter

Object. The purpose of this study was to combine the immunosuppressive and neuroregenerative effects of tacrolimus (FK506) with cold preservation of peripheral nerve allografts to maximize axonal regeneration across short peripheral nerve gaps.

Methods. Ninety-six male C3H mice were randomized to six groups, which were composed of animals with isografts (Group 1, positive control), allografts (Group 2, negative control), allografts treated with subtherapeutic doses of FK506 without and with cold preservation (Groups 3 and 4), and allografts treated with therapeutic doses of FK506 without and with cold preservation (Groups 5 and 6). Results were determined using walking-track data and histomorphometric measurements.

Three weeks postoperatively, animals treated with therapeutic doses of FK506 after receiving cold-preserved allografts demonstrated accelerated functional recovery relative to all other groups. In addition, histomorphometric parameters in these animals (1257 ± 847 total axons, 6.7 ± 3.3% nerve tissue, 11.8 ± 6.5% neural debris, 8844 ± 4325 fibers/mm2 nerve density, and 2.53 ± 0.25 µm fiber width) were the same as or better than in all other groups. The parameters of percent nerve tissue (p < 0.016), nerve density (p < 0.038), and percent neural debris (p < 0.01) were statistically significantly better than those in all other groups, including Group 1 (isograft, positive control).

Conclusions. The combination of FK506 treatment with cold preservation of nerve allografts resulted in functional and histomorphometric recovery superior to that with either modality alone.

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Michael J. Franco, Benjamin Z. Phillips, Gopal R. Lalchandani and Susan E. Mackinnon

OBJECTIVE

The authors of this study sought to determine the outcomes of patients undergoing superficial peroneal nerve (SPN) release to treat lower-extremity pain and describe consistent anatomical landmarks to direct surgical planning.

METHODS

This retrospective cohort study examined 54 patients with pain in the SPN distribution who were treated with decompression between 2011 and 2014. Patients rated pain and the effect of pain on quality of life (QOL) on the visual analog scale (VAS) from 0 to 10. Scores were then converted to percentages. Linear regression analysis was performed to assess the impact of the preoperative effect of pain on QOL, age, body mass index (BMI), and preoperative duration of pain on the postoperative effect of pain on QOL. Measurements were made intraoperatively in 13 patients to determine the landmarks for identifying the SPN.

RESULTS

A higher BMI was a negative predictor for improvement in the effect of pain on QOL. A decrease in pain compared with the initial level of pain suggested a nonlinear relationship between these variables. A minority of patients (7 of 16) with a preoperative pain VAS score ≤ 60 reported less pain after surgery. A large majority (30 of 36 patients) of those with a preoperative pain VAS score > 60 reported improvement. Intraoperative measurements demonstrated that the SPN was consistently found to be 5 ± 1.1, 5 ± 1.1, and 6 ± 1.2 cm lateral to the tibia at 10, 15, and 20 cm proximal to the lateral malleolus, respectively.

CONCLUSIONS

A majority of patients with a preoperative pain VAS score > 60 showed a decrease in postoperative pain. A higher BMI was associated with less improvement in the effect of pain on QOL. This information can be useful when counseling patients on treatment options. Based on the intraoperative data, the authors found that the SPN can be located at reliable points in reference to the tibia and lateral malleolus.

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Rahul K. Nath, Susan E. Mackinnon, John N. Jensen and William C. Parks

✓ The authors studied the spatial expression and regulation of messenger RNA for the a 1 subunit of collagen type I in crushed rat sciatic nerve to provide a basis for future therapeutic manipulation.

Sciatic nerves in 20 male or female adult Lewis rats were crushed for 60 seconds; the unharmed contralateral sciatic nerves served as controls. Twenty-one days after injury the experimental animals were killed and their tissue was harvested. The spatial expression of collagen type I was determined by using in situ hybridization techniques. Quantification of fibroblast number and total signal was performed through computerized morphometry. Collagen upregulation was evident in epineurial and perineurial layers, with the epineurium displaying higher activity. The cells responsible for procollagen type I production were fibroblasts. No activity was seen in the endoneurium.

Morphometric findings indicated that collagen upregulation in the epineurium and perineurium occurred at both pretranscriptional and posttranslational levels when compared to controls; a paired t-test analysis confirmed statistical significance for all comparisons between injured and control tissues.

Epineurial fibroblasts are responsible for the collagen production associated with crushed peripheral nerve injury in the rat. Regulation occurs pretranscriptionally as well as posttranslationally. It is interesting to speculate that the delivery of agents directed against collagen production (such as neutralizing antibodies to growth factors) into epineurial tissues proximate to the time and location of clinical nerve injury might mitigate later deleterious effects of excess collagen production in axonal regeneration.

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Wilson Z. Ray, Chester K. Yarbrough, Andrew Yee and Susan E. Mackinnon

The surgical management of lower brachial plexus injuries remains a challenging problem. Although nerve transfers have improved clinical outcomes following brachial plexus injuries, the majority of work has focused on upper trunk injuries. Complete lower plexus injuries often lack suitable donors for either nerve or tendon transfers. The authors describe their experience with isolated lower trunk injuries utilizing the nerve to the brachialis to reinnervate the anterior interosseous nerve.

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Nicholas M. Barbaro