Nilton Mazzer

Directly applied low intensity direct electric current enhances peripheral nerve regeneration in rats.

The influence of direct electric stimulation on nerve regeneration was studied in a model of crush injury of the sciatic nerve of rats. Forty-three rats were used and distributed in four groups according to the procedure: (1) intact nerve, inactive circuit; (2) crush injury, inactive circuit; (3) intact nerve, active circuit; (4) crush injury, active circuit. The low intensity continuous current circuit (1 microA) was implanted in the lumbar region, the anode being fixed to the muscles proximally and the cathode below the nerve distally to the lesion site. The Sciatic Functional Index (SFI) was evaluated at weekly intervals for 3 weeks, the sciatic nerve being resected on the 21st day for histologic and morphometric studies. The SFI progressively improved and the average fiber nerve density recovered to a nearly normal value in Group 2 and increased in Group 4 compared with the control groups (1 and 3), but this was accompanied by a decreased average fiber nerve diameter. Both number and diameter of inter and intra-fascicular blood vessels increased in the stimulated nerves. We conclude that low intensity direct electric stimulation enhances nerve regeneration following a controlled nerve crush injury and increases blood supply by increasing number and diameter of vasa nervorum.

Can therapeutic ultrasound influence the regeneration of peripheral nerves

An experimental study of the influence of the therapeutic ultrasound on the regeneration of the sciatic nerve submitted to a controlled crush injury was carried out in rats. Twenty female Wistar rats weighing 250 g on average were used and divided into two groups of 10 animals each, respectively, submitted to: (1) crush injury followed by ultrasound irradiation and (2) crush injury only. Under general anaesthesia the sciatic nerve was exposed on the right thigh and crushed with a device especially developed and built for this purpose, with a 15,000g constant load for 10 min, affecting a 5mm-long segment of the nerve proximal to its bifurcation. Pulsed ultrasound irradiation (1:5, 1 MHz, 0.4 W/cm(2), 2 min duration) was started the day after the operation and repeated for 10 consecutive days. The sciatic functional index (SFI) was evaluated at weekly intervals up to the third week, when the animal was killed for histologic and nerve fiber density studies of the sciatic nerve carried out on the lesion site and on the segments immediately proximal and distal to it. The SFI progressively improved for both treated and untreated nerves but in a more marked and significant way for the treated nerves (73 and 55%, respectively). Nerve fiber density did no return to normal in either case but was significantly higher in the treated nerves, with predominance of small diameter thin myelin sheath fibers typical of nerve regeneration in the treated nerves, as opposed to large diameter thin myelin sheath fibers in the untreated nerves. The authors conclude that low intensity therapeutic ultrasound enhances nerve regeneration, as demonstrated with significance on the 21st postoperative day.

Is the Sciatic Functional Index always reliable and reproducible

The Sciatic Functional Index (SFI) is a quite useful tool for the evaluation of functional recovery of the sciatic nerve of rats in a number of experimental injuries and treatments. Although it is an objective method, it depends on the examiners ability to adequately recognize and mark the previously established footprint key points, which is an entirely subjective step, thus potentially interfering with the calculations according to the mathematical formulae proposed by different authors. Thus, an interpersonal evaluation of the reproducibility of an SFI computer-aided method was carried out here to study data variability. A severe crush injury was produced on a 5 mm-long segment of the right sciatic nerve of 20 Wistar rats (a 5000 g load directly applied for 10 min) and the SFI was measured by four different examiners (an experienced one and three newcomers) preoperatively and at weekly intervals from the 1st to the 8th postoperative week. Three measurements were made for each print and the average was calculated and used for statistical analysis. The results showed that interpersonal correlation was high (0.82) in the 3rd, 4th, 5th, 7th and 8th weeks, with an unexpected but significant (p<0.01) drop in the 6th week. There was virtually no interpersonal correlation (correlation index close to 0) on the 1st and 2nd weeks, a period during which the variability between animals and examiners (p=0.24 and 0.32, respectively) was similar, certainly due to a poor definition of the footprints. The authors conclude that the SFI method studied here is only reliable from the 3rd week on after a severe lesion of the sciatic nerve of rats.

Morphologic and morphometric evaluation of experimental acute crush injuries of the sciatic nerve of rats

In order to qualify and quantify nerve fiber lesion following an acute crush injury, a morphologic and morphometric study was carried out in 25 Wistar rats divided into five groups of five animals each according to the crushing load applied, i.e., 500, 1,000, 5,000, 10,000, and 15,000 g. The injury was produced under general anesthesia on a 5mm-long intermediate segment of the right sciatic nerve for 10 min using a dead-weight machine. The animals were killed with an excessive dose of anesthetics 72 h later and submitted to perfusion with a fixing solution through the abdominal aorta immediately after death. Both the right and left sciatic nerves were removed and prepared for histologic and morphometric examinations; 5 microm-thick sections stained with 1% Toluidine blue were examined under a light microscope equipped with a video camera linked to a computer loaded with a graphic program (KS 400). The morphometric studies included measuring total number of fibers, fiber density, fiber diameter, myelin fiber area, axon diameter, axon area and G ratio. The results showed that damage to the nerve fibers began to appear as early as with the 500 g load and was similar in all groups despite the load applied, increasing with the 10,000 and 15,000 g loads, although the external supporting tissues and small diameter fibers were preserved. The predominant type of lesion produced was axonotmesis.

The end-to-side peripheral nerve repair. Functional and morphometric study using the peroneal nerve of rats.

Morphologic and functional recovery following an end-to-side repair was studied comparatively with conventional end-to-end repair in a model of peroneal nerve lesion in rats. Twenty-eight rats were used and divided into four groups according to the reparative procedure following nerve division: (1) nerve stumps buried into neighboring muscles (n = 8); (2) conventional end-to-end repair (n = 7); (3) end-to-side repair onto the tibial nerve (n = 8); (4) sham operation (n = 5). The sciatic functional index (SFI) was evaluated at weekly intervals for 8 weeks, the peroneal nerve being resected on the 56th day for histologic and morphometric studies. The SFI progressively improved in Groups 2 (-16.9) and 3 (-22.7), although it did not reach normal values (around -8). The average nerve fiber density increased to normal values in both Groups 2 and 3, although accompanied by a marked decrease of average minimal and maximal nerve fiber diameter, myelin sheath area and G quotient. The differences between Groups 2 and 3 or Groups 2 and 4 were not significant. We conclude that, although resulting in significant morphologic and functional recovery, end-to-side repair is not as efficient as the conventional end-to-end nerve repair. However, end-to-side repair has a potential for application in selected cases in humans.

Mechanical Strengths of Tendon Sutures An in vitro comparative study of six techniques

A comparative study of six tendon suturing techniques (1. Modified Kessler + simple epitendinous running suture; 2. Modified Kessler + Halsted epitendinous suture; 3. “Six strand” suture; 4. “Interlocking” suture; 5. “Cross stitch” suture; 6. simple epitendinous running suture) was carried out by evaluating strength in relation to the beginning of separation between the tendon stumps, a 3 mm separation and rupture in porcine flexor tendons. The technique most resistant to initial separation was the modified Kessler + Halsted epitendinous suture followed by the “Six strand” suture. The “Six strand” suture was the most resistant to the 3 mm separation and rupture followed by the modified Kessler + Halsted epitendinous suture. Despite the greater resistance to rupture of the “Six strand” technique, we conclude that modified Kessler + Halsted epitendinous suture showed the best overall performance and was easier to use.

The Posterior Interosseous Forearm Island Flap for Skin Defects in the Hand and Elbow A Prospective Study of 51 Cases

The authors’ experience of 51 posterior interosseous forearm island flaps is presented. Its main indications were inadequate scar or scar contraction and complex trauma with gross skin loss, either acute or postprimary. The flap healed uneventfully in 45 cases (88%), but in six it was partially or subtotally lost due to necrosis. Late complications included hair growth in the first web and palm, flap redundancy and hypertrophic scar at the donor site. The posterior interosseous island flap produces excellent skin coverage but is difficult to raise and tends to develop oedema and occasionally necrosis.

A Laserterapia de baixa intensidade acelera a regeneração de nervos periféricos

There are evidences that laser therapy may stimulate nerve regeneration and this hypothesis was tested in rats. A controlled crush injury was produced on the sciatic nerve of 20 Wistar rats, half of which submitted to effective Ga-As laser irradiation and the other half to simulated irradiation for 10 consecutive days beginning on the first postoperative day. Results were evaluated at three weeks postoperatively by measuring the sciatic functional index (SFI) at weekly intervals and the total number of nerve fibers and nerve fiber density of the sciatic nerve at three weeks (p<0.05). The SFI progressively improved for both irradiated and control nerves (69% and 45%, respectively) with a significant difference between them at two weeks (p=0.04). Nerve fiber density increased for the irradiated nerves and decreased for the control nerves, with significant differences between them (p=0.001). Low intensity therapeutic ultrasound accelerates nerve regeneration, as demonstrated with significance on the 21st postoperative day.

Os efeitos do ultra-som terapêutico nas lesões por esmagamento do nervo ciático de ratos: análise funcional da marcha

Background: The effects of therapeutic ultrasound irradiation on peripheral nerve regeneration are not well known, particularly regarding functional recovery. However, in rats, footprint evaluation is a well-systematized method for measuring the Sciatic Functional Index (SFI), showing close correlation with morphological regeneration of damaged sciatic nerves. Objective: To analyze the influence of therapeutic ultrasound on sciatic nerve regeneration in rats subjected to controlled crushing. Method: 20 Wistar rats (mean body weight: 300 g) were divided into two experimental groups: 1) crushing only (n=10); 2) crushing followed by ultrasound irradiation (n=10). Under general anesthesia, a 5-mm segment of sciatic nerve proximal to its bifurcation in the right thigh was exposed and crushed with constant loading of 15 kg for 10 minutes, using a specially-built device. Low-intensity pulsed ultrasound irradiation (1:5, 0.4 W/cm2, 1 MHz, 2 minutes) was started on the first postoperative day and administered for ten consecutive days. Footprints were obtained weekly (postoperative weeks 13) using a specially-designed walkway, and evaluated using specifically-developed software, according to a previously-tested method, with automatic SFI calculation. Results: The SFI progressively increased in both groups: Group 2, from 101 in the first week to 59.21 (second) and 26.68 (third), i.e. 73% improvement overall; Group 1, from 98.2 (first) to 79.5 (second) and 44 (third), i.e. 55% improvement overall. The differences between the groups were significant for the second and third weeks (p=0.02 and p=0.002, respectively). Conclusion: Low-intensity therapeutic ultrasound accelerates the regeneration of crushed sciatic nerves in rats, as demonstrated by its functional recovery.

Efeitos do ultra-som pulsado de baixa intensidade sobre a cicatrização por segunda intenção de lesões cutâneas totais em ratos

We evaluated the effects of low-power pulsed ultrasound on skin injury healing at dorsal region of rats. Sixty male rats were used (Wistar, mean weight: 300 g) divided into two groups, namely: 1) simulated irradiation; 2) effective irradiation (basic rate of 1.5MHz, pulse cycle rate of 1KHz, pulse width of 200 µs, power of 30mW/cm2 -SATA, 10 minutes of application in alternate days). These were further divided into subgroups, according to the time of injury assessment, as 3, 7, and 14 days, and healing was assessed by planimetrical and histomorphometrical analysis. A significant increase (p<0.05) of the healing area was seen for Group 2 (141.88±18.50 mm2) compared to Group 1 (117.38±15.14 mm2), at the 14th day. There was a significant reduction of the number of inflammatory cells (p<0.05), associated to an increment of angiogenesis for Group 2 (2196.56 cel/mm2±234.93) in comparison to Group 1 (2611.68 cel/mm²±423.82), at the 3rd day. No significant differences were seen in collagen formation, or on dermis and epidermis area between groups. It was concluded that low-power pulsed ultrasound does not cause any deleterious effects and can moderately stimulate skin second-intention healing in experimental environments, showing a potential to clinical use in human beings.