Concepts of peripheral nerve repair

The role of undifferentiated adipose-derived stem cells in peripheral nerve repair

Peripheral nerve injuries impose significant health and economic consequences, yet no surgical repair can deliver a complete recovery of sensory or motor function. Traditional methods of repair are less than ideal: direct coaptation can only be performed when tension-free repair is possible, and transplantation of nerve autograft can cause donor-site morbidity and neuroma formation. Cell-based therapy delivered via nerve conduits has thus been explored as an alternative method of nerve repair in recent years. Stem cells are promising sources of the regenerative core material in a nerve conduit because stem cells are multipotent in function, abundant in supply, and more accessible than the myelinating Schwann cells. Among different types of stem cells, undifferentiated adipose-derived stem cell (uASC), which can be processed from adipose tissue in less than two hours, is a promising yet underexplored cell type. Studies of uASC have emerged in the past decade and have shown that autologous uASCs are non-immunogenic, easy to access, abundant in supply, and efficacious at promoting nerve regeneration. Two theories have been proposed as the primary regenerative mechanisms of uASC: in situ trans-differentiation towards Schwann cells, and secretion of trophic and anti-inflammatory factors. Future studies need to fully elucidate the mechanisms, side effects, and efficacy of uASC-based nerve regeneration so that uASCs can be utilized in clinical settings.

Clinical outcomes of carpal tunnel release in patients 65 and older

PURPOSE

Some hand surgeons have encountered an attitude among referring physicians as well as patients that carpal tunnel release (CTR) is less effective and more morbid in older patients. The purpose of this study was to determine the efficacy of CTR in patients aged 65 and older.

METHODS

Patients 65 years of age or older with carpal tunnel syndrome for whom release was indicated were studied prospectively. All patients had a limited palmar incision CTR and a standardized postoperative rehabilitation protocol. The patients' subjective and objective signs and symptoms were measured before surgery and at 6 months after surgery. Scar tenderness and patient satisfaction also were recorded. The Michigan Hand Outcome Questionnaire was used to determine overall hand function, activities of daily living, work performance, pain, aesthetics, and satisfaction with hand function.

RESULTS

Seventy-five patients (105 hands) were enrolled; 6-month follow-up data were available on 92 hands on 66 patients. The mean age was 74 +/- 6 years. By patient report, paresthesias, numbness, day pain, night pain, and nocturnal numbness each decreased significantly from severe or very severe to mild or none. All but 2 of the Tinel's signs and one of the Phalen's signs became negative. The mean 2-point discrimination improved from 6.4 +/- 1.3 mm to 4.9 +/- 1.1 mm. Grip and pinch strength increased by 0.9 +/- 7.4 kgf and 0.6 +/- 2.5 kgf, respectively. The Michigan Hand Outcome Questionnaire confirmed a significant improvement in overall hand function, activities of daily living, pain, and satisfaction with hand function. Overall 83% of patients were either very or completely satisfied with their results.

CONCLUSIONS

Patients 65 years of age or older objectively benefit and have improved clinical outcomes after CTR. Age alone should not be a contraindication to CTR.

Evaluation of biocompatibility of polypyrrole in vitro and in vivo

In this study, the biocompatibility of the electrically conductive polymer polypyrrole (PPy) with nerve tissue was evaluated in vitro and in vivo. The extraction solution of PPy powder, which was synthesized chemically, was tested for acute toxicity, subacute toxicity, pyretogen, quantitative measure of cell viability, hemolysis, allergen, and micronuclei. The PPy membrane was synthesized electrochemically on the indium tin oxide conductive borosilicate glass. The dorsal root ganglia from 1-3-day-old Sprague-Dawley rats were cultured above PPy membrane and observed by light or scanning electron microscopy. The PPy-silicone tube (PPy membrane on the inner surface of the silicone tube) also synthesized electrochemically was used to bridge across 10-mm sciatic nerve gap in rats. Twenty-four weeks after the operation to rats, the regenerated tissues were observed by electrophysiological and histological techniques. PPy extraction solution showed no evidence of acute and subacute toxicity, pyretogen, hemolysis, allergen, and mutagenesis, and the Schwann cells from the PPy extraction solution group showed better survival rate and proliferation rate as compared with the saline solution control group. The migration of the Schwann cells and the neurite extension from dorsal root ganglia on the surface of PPy membrane-coated glass was better than those of bare glass. There was only lightly inflammation during 6 months of the postoperation, when the PPy-silicone tube bridged across the gap of the transected sciatic nerve. The regeneration of nerve tissue in the PPy-silicone tube was slightly better than that in the plain silicone tube by means of electrophysiological and histological examination. The results of this study indicate that PPy has a good biocompatibility with rat peripheral nerve tissue and that PPy might be a candidate material for bridging the peripheral nerve gap.

Traction injury of common peroneal nerve associated with multiple ligamentous rupture of the knee: a case report

We report on a case of a 19-year-old male student who sustained a hyperextension injury to his left knee while playing rugby, which resulted in a traction injury of the common peroneal nerve and multiple ligamentous injuries at the knee joint. The damaged part of the common peroneal nerve was resected, and an end-to-end suture was performed, because the gap between the nerve ends was small enough to allow closure with little mobilization. Now, 2.5 years after the surgery, the patient shows remarkable recovery. This result suggests that end-to-end suture is an ideal procedure for nerve traction injury, if the nerve ends can be closed without tension, without excessive flexion of the adjacent joint.

Endoscopic technique for harvesting the intercostal nerve as a nerve graft: a feasibility preliminary study in cadavers

Endoscopic surgical procedures in plastic surgery have been applied in numerous aesthetic and reconstructive surgical techniques. The use of the endoscopic video-assisted technique in peripheral nerve surgery is one of the most recent advances in reconstructive surgery. In this preliminary report, the seventh intercostal nerve, in fresh human cadavers, was harvested with the aid of endoscopy through a single 2-cm transverse incision. The anatomy of the intercostal nerve and the endoscopic surgical technique are described in this report. Multiple intercostal nerve grafts of adequate size, number, and length could be harvested, with less donor site morbidity, and used for future reconstruction of the injured peripheral nerve. The advantages of using an endoscopic technique to harvest the intercostal nerve include a magnified, clear, and illuminated visualization; a better remote access incision site; and an atraumatic technique, which may be proven particularly applicable in clinical procedures in patients who are prone to hypertrophic scars such as in women and children.

Comparison of nerve regeneration through different types of neural prostheses

Rat sciatic nerve regeneration through three synthetic neural prostheses was compared with regeneration through nerve allografts. The synthetic prostheses were either nonpermeable nonabsorbable (Silastic), permeable absorbable (polyglactin mesh), or permeable nonabsorbable (polypropylene mesh). Animals were evaluated at 10, 24, and 90 days. Functional analysis of nerve regeneration was performed by noninvasive methods: electromyography and walking tracks. Nerve tissue was examined with routine histologic and immunofluorescent techniques. A compressive neuropathy developed with the use of the Silastic implant. A neutrophilic inflammatory infiltrate was consistently associated with implantation of the polyglactin mesh. A strong connective tissue response was noted around the polypropylene mesh. Early recovery of nerve function was seen with the Silastic implants, however, overall nerve function was best in the nerve allograft and polypropylene mesh groups. Polyglactin implantation increases the local inflammatory response and should not be used for nerve anastomoses. If Silastic entubulation is used, it should be removed between 24 and 90 days.

Rapid immunoperoxidase staining of axons for frozen section diagnosis of nerve biopsy specimens

A new method of freezing and embedding a nerve biopsy specimen and staining it with the immunoperoxidase technique for neurofilaments was developed to overcome the difficulties normally encountered in the assessment of tiny portions of nerve. The method clearly shows the architecture of the nerve, the exact number and size of all axons present, and the degree of fibrosis present. The entire procedure may be accomplished in 20 minutes.