Bridging of nerve gaps after injury is a major problem in peripheral nerve regeneration. Considering the potential application of a bio-artificial nerve guide material, polycaprolactone (PCL)/chitosan nanofibrous scaffolds was designed and evaluated in vitro using rat Schwann cells (RT4-D6P2T) for nerve tissue engineering. PCL, chitosan, and PCL/chitosan nanofibers with average fiber diameters of 630, 450, and 190 nm, respectively, were fabricated using an electrospinning process. The surface chemistry of the fabricated nanofibers was determined using Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. Simple blending of PCL with chitosan proved an easy and efficient method for fabricating PCL/chitosan nanofibrous scaffolds, whose surface characteristics proved more hydrophilic than PCL nanofibers. Evaluation of mechanical properties showed that the Young's modulus and strain at break of the electrospun PCL/chitosan nanofibers were better than those of the chitosan nanofibers. Results of cell proliferation studies on nanofibrous scaffolds using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium assay showed 48% more cell proliferation on PCL/chitosan scaffolds than on PCL scaffolds after 8 days of culture. PCL/chitosan scaffolds showed better cell proliferation than PCL scaffolds and maintained their characteristic cell morphology, with spreading bipolar elongations to the nanofibrous substrates. This electrospun nanofibrous matrix thus proved of specific interest in tissue engineering for peripheral nerve regeneration.

A novel nanofibrous construct for promoting peripheral nerve repair was fabricated and tested in a rat sciatic nerve defect model. The conduit is made out of bilayered nanofibrous membranes with the nanofibers longitudinally aligned in the lumen and randomly oriented on the outer surface. The intra-luminal guidance channel is made out of aligned nanofibrous yarns. In addition, biomolecules such as laminin and nerve growth factor were incorporated in the nanofibrous nerve construct to determine their efficacy in in vivo nerve regeneration. Muscle reinnervation, withdrawal reflex latency, histological, axon density and electrophysiology tests were carried out to compare the efficacy of nanofibrous constructs with an autograft. Our study showed mixed results when comparing the artificial constructs with an autograft. In some cases, the nanofibrous conduit with aligned nanofibrous yarn as an intra-luminal guidance channel performs better than the autograft in muscle reinnervation and withdrawal reflex latency tests. However, the axon density count is highest in the autograft at mid-graft. Functional recovery was improved with the use of the nerve construct which suggested that this nerve implant has the potential for clinical usage in reconstructing peripheral nerve defects.

Nanotechnology is an area receiving increasing attention as progress is made towards tailoring the morphology of polymeric biomaterial for a variety of applications. In the present study an attempt was made to electrospin poly(L-lactide-co-glycolide) biodegradable polymer nanofibres. In this process, polymer fibres with diameters down to the nanometre range are formed by subjecting a fluid jet to a high electric field. The nanofibres were collected on to a rotating Teflon mandrel and fabricated to tubes or conduits, to function as nerve guidance channels. The feasibility of in vivo nerve regeneration was investigated through several of these conduits. The biological performance of the conduits were examined in the rat sciatic nerve model with a 10 mm gap length. After implantation of the nanofibre nerve guidance conduit to the right sciatic nerve of the rat, there was no inflammatory response. One month after implantation five out of eleven rats showed successful nerve regeneration. None of the implanted tubes showed tube breakage. The nanofibre nerve guidance conduits were flexible, permeable and showed no swelling. Thus, these new poly(L-lactide-co-glycolide) nanofibre conduits can be effective aids for nerve regeneration and repair. Improvements could be done by impregnating nerve growth factors or Schwann cells and may lead to clinical applications.

Therapeutic, IV.

This article describes the authors' experience with the submental flap over the past 10 years. A brief review of the key points and some refinements in the operative technique are discussed. The results concern 31 patients with a mean age of 57 years. All flaps were pedicled except two. One case of composite flap with bone was used. The mean size of the flap was 11.8 x 5.5 cm, and the mean postoperative stay was 11.1 days. Complications encountered were one case of temporary palsy of the marginal mandibular branch of the facial nerve, one hematoma at the recipient site, and two cases of partial flap loss. Color and texture match were good. The authors believe this flap to have great clinical potential and to be a worthwhile addition to the existing surgical armamentarium.

Most standard textbooks of hand surgery quote the prevalence of absence of palmaris longus at around 15%. However, this figure varies considerably in reports from different ethnic groups. We studied 329 Chinese men and women and found palmaris longus to be absent unilaterally in 3.3%, and bilaterally in 1.2%, with an overall prevalence of absence of 4.6%. There was no significant difference in its absence with regard to the body side or the sex. Our literature review revealed a low prevalence of absence in Asian, Black and Native American populations and a much higher prevalence of absence in Caucasian populations. It is clear that a standard prevalence of absence of the palmaris longus cannot be applied to all populations.

Free tissue transfer has become the most important means of limb salvage treatment after severe trauma. This one-step procedure shortens healing and hospitalization time and minimizes the danger of infection. However, very few studies have considered the use of free tissue transfer for the reconstruction of traumatic limb injuries in children. This study reports 22 such cases treated in the authors' unit between 1993 and 2000 (17 boys and 5 girls; mean age, 8.9 years; age range, 18 months-15 years; 16 lower and 6 upper limbs). All flaps were indicated for repair of acute traumatic defects (20-500 cm2). Five different flaps were used: 12 scapular, 4 latissimus dorsi, 4 serratus anterior, 1 groin, and 1 temporalis fascia. All were successful, except for partial necrosis with the free groin flap. Three flaps requiring reexploration for venous insufficiency had a successful outcome. The microsurgical success rate in this pediatric population is very high, and the state and size of the donor site and recipient vessels have caused no problems. No long-term complications have been noted (mean follow-up, 3.8 years).

The treatment of infected exposed implants which have been used for internal fixation usually involves debridement and removal of the implant. This can result in an unstable fracture or spinal column. Muscle flaps may be used to salvage these implants since they provide soft-tissue cover and fresh vascularity. However, there have been few reports concerning their use and these have concentrated on the eradication of the infection and successful soft-tissue cover as the endpoint. There is no information on the factors which may influence the successful salvage of the implant using muscle flaps. We studied the results and factors affecting outcome in nine pedicled muscle flaps used in the treatment of exposed metal internal fixation with salvage of the implant as the primary endpoint. This was achieved in four cases. Factors predicting success were age < 30 years, the absence of comorbid conditions and a favourable microbiological profile. The growth of multiple organisms, a history of smoking and the presence of methicillin-resistant Staphylococcus aureus on wound cultures indicated a poor outcome. The use of antibiotic beads, vacuum-assisted closure and dressing, the surgical site, the type of flap performed and the time from primary surgery to flap cover were not predictive of outcome.