Spatial-Temporal progress of peripheral nerve regeneration within a silicone chamber: Parameters for a bioassay

The spatial-temporal progress of peripheral nerve regeneration across a 10-mmgap within a silicone chamber was examined with the light and electron microscope at 2-mm intervals. A coaxial, fibrin matrix was observed at 1 week with a proximal-distal narrowing that extended beyond the midpoint of the chamber. At 2 weeks, Schwann cells, fibroblasts, and endothelial cells had migrated into the matrix from both nerve stumps. There was a delay of 7–14 days after nerve transection and chamber implantation before regenerating axons appeared in the chamber. At 2 weeks, nonmyelinated axons were seen only in the proximal 1–5 mm of the chamber in association with Schwann cells. Axons reached the distal stump by 3 weeks and a proximal-distal gradient of myelination was observed. These observations define the parameters of a morphologic assay for regeneration in this chamber model which can be used to investigate cellular and molecular mechanisms underlying the success of peripheral nerve regeneration.     

Reorganization and orientation of regenerating nerve fibres,perineurium, and epineurium in preformed mesothelial tubes – an experimental study on the sciatic nerve of rats

Regeneration of severed peripheral nerves is unfortunately often incomplete, due to loss of nerve fibers and neuroma formation. A new approach is presented with the intention of improving the conditions for nerve repair. In the first of the two stages, a pseudosynovial tube is formed around a silicone rubber rod, surrounded by a stainless steel spiral, which was placed in the backs of rats. This tube, in the second stage, is used as a free “tube graft” to bridge gaps of about 10–12-mm lengths in the severed sciatic nerve. The tube was kept open by the metal spiral. Regenerating nerve fibers with their sprouts grew into the initially open space in the tube. A new nerve trunk was formed, comprised of closely packed myelinated and unmyelinated axons, organized into fascicles. Demonstration by electron microscopy and by EMG recording of reinnervation of foot muscles supported successful long-term results. The fascicles were delimited by perineurial and epineurial sheaths and, furthermore, showed signs of maturation. It was also demonstrated that the nerve-fiber regeneration ceased after a few weeks if there was no distal nerve inserted into the tube. The importance of optimizing the interaction between local factors and regenerating nerve fibers for reestablishment of functionally valuable motor units is discussed.     

Hand muscle pathology after long-term vibration exposure

The morphology of the abductor pollicis brevis muscle was studied in 20 patients suffering from hand-arm vibration syndrome. The main morphological changes observed were centrally located myonuclei and fibre type grouping (found in all 20 muscle biopsies), angulated muscle fibres (found in 19 biopsies), ring fibres and regenerating fibres (found in 18 biopsies) and fibrosis (found in 17 biopsies). The observed abnormalities are believed to reflect damage to both the muscle fibres and the motor nerve. The changes were related to different vibration exposure parameters. The number of fibres demonstrating centrally located nuclei correlated significantly with the cumulative vibration exposure, while the number of angulated fibres correlated significantly with the total vibration exposure time. This indicates that the vibrating tools may cause direct damage to muscle fibres as well as nerves.     

Radiographic evaluation of osseointegration and loosening of titanium implants in the MCP and PIP joints

PURPOSE: Good to excellent clinical results have been shown in the initial studies on osseointegrated metacarpophalangeal (MCP) and proximal interphalangeal (PIP) joint implants that consist of a flexible silicone spacer connected to osseointegrated titanium fixtures. A high fracture rate of the silicone spacer, however, has been reported, diminishing the value of this implant system. The purpose of this study was to evaluate the osseointegration of the titanium fixture itself in a large study group and compare patients with rheumatoid arthritis with those with osteoarthrosis as a base for further development of the implant concept. METHODS: Two hundred thirty-nine implants (27 PIP, 212 MCP) in 86 patients were retrospectively evaluated radiographically. Two hundred implants were in patients with rheumatoid arthritis. Radiographic evaluation included measuring the length and width of resorption zones around the titanium fixtures. A scoring system was used that grouped observations in 4 groups, from 0 (little or no change) to 3 (loosening). Status of the silicone spacer was also noted. RESULTS: At follow-up evaluation an average of 41 months (range, 12-103 months) after surgery, complete osseointegration was found in 450 of 478 fixtures (94%). Loosening was found in 10 proximal and 18 distal fixtures. The proximal fixtures showed loosening mainly during the first 3 years after surgery and the distal fixtures also had loosening. In the 31 MCP joint implants that were evaluated for more than 5 years, the osseointegration rate was 97%. CONCLUSIONS: Implant stem fixation with osseointegrated titanium fixtures is a valuable method that works well in rheumatoid arthritis patients. Further development will focus on a more durable constrained joint mechanism.     

The quality of drugs in private pharmacies in Lao PDR: a repeat study in 1997 and 1999

Objective: To present a repeated test of the quality of ampicillin, tetracycline, chloroquine and ASA from private pharmacies in Laos in 1997 and 1999, and to discuss the quality in relation to the National Drug Policy Programme.Method: A total of 115 of 214 licensed private pharmacies were selected in Savannakhet province, a pilot province in the Lao National Drug Policy Programme. The four drugs, if available, were collected at each pharmacy. Thirty tablets of each drug were taken from a selected container. In 1997, 366 samples were analysed and three hundred in 1999. Identity, assay (content of active component) and measurement of weight variation tests were performed. Drug quality was compared mainly according to the standards of the British and United States pharmacopoeias.Results: The percentage of substandard drugs decreased significantly from 46% to 22% between 1997 and 1999 (P < 0.001). Substandard ampicillin and tetracycline were reduced significantly from 67% to 9% and from 38% to 12%, respectively (P < 0.001). In total, 3% vs 1% contained no active ingredient, 12% vs 4% had too little or too much active ingredient, and 35% vs 14% had weight variation outside pharmacopoeial limits.Conclusion: Drug quality was improved. However, the prevalence of substandard drugs was still unacceptably high, which may result in adverse clinical effect or treatment failure for individual patients.     

What determines the costs of repair and rehabilitation of flexor tendon injuries in zone II? A multiple regression analysis of data from southern Sweden

The epidemiology and costs of repair and rehabilitation of zone II flexor tendon injuries in 135 patients from the southern part of Sweden were analysed. The little finger was most frequently injured (43%), usually with a knife (46%), and 30% of the injuries were work related. Total median costs within the health-care sector for the injuries were SEK 48,500 (1 EURO=9.23 SEK, 4/1/2002). Costs in other sectors were SEK 93,000. Active mobilization or mobilization with rubber band traction increased costs within the health-care sector (SEK 7400 or SEK 6000, respectively) but improved range of movement (5-7%). Immobilization had a higher complication rate (rupture or need for secondary procedures), which in itself increased total costs by 57%. Non-linear effects were found between age and costs within the health-care sector and the outcome.     

Sensory substitution in prosthetics

Use of arm and hand prostheses may be essential for many amputees to facilitate activities of daily life and interaction with society. A major drawback that reduces the use of prostheses, however, is the lack of sensibility. Current strategies for sensory feedback in commercially available prostheses are based on force and slip sensors in the mechanical hand for independent grasp control in an opening and closing function. Developing principles for providing conscious sensibility is discussed, including new techniques where hearing is used as substitution for sensation based on sense substitution.