Clinical nerve reconstruction with a bioabsorbable polyglycolic acid tube

Microneurosurgical techniques to reconstruct nerve gaps with nerve grafts frequently fail to achieve excellent functional results and create donor-site morbidity. In the present study, 15 patients had gaps of 0.5 to 3.0 cm (mean 1.7 cm) in digital nerves reconstructed by one surgeon with a bioabsorbable polyglycolic acid (PGA) tube. A final evaluation of sensibility was done by a second surgeon at a mean postoperative interval of 22.4 months (range 11 to 32 months). These were all secondary reconstructions. The evaluation included a digital nerve block with local anesthetic for the intact (not reconstructed) digital nerve. Excellent functional sensation (moving two-point discrimination less than or equal to 3 mm and/or static two-point discrimination less than or equal to 6 mm) was present in 33 percent and good functional sensation (moving two-point discrimination of 4 to 7 mm and/or static two-point discrimination of 7 to 15 mm) in 53 percent of the digital nerve reconstructions. One patient with poor sensory recovery and one with no recovery were judged as functional failures (14 percent). Absence of pain at the site of reconstruction was judged by the patient to be excellent in 40 percent, good in 33 percent, and poor in 27 percent. We conclude that reconstruction of nerve gaps of up to 3.0 cm with a bioabsorbable PGA tube gives clinical results at least comparable to the classic nerve graft technique while avoiding donor-site morbidity.     

Human pressure perception values for constant and moving one- and two-point discrimination.

Despite the need to evaluate sensibility for accurate diagnosis and the need to record the degree of sensation achieved in the postoperative period, the clinician has been without the ability to measure human pressure perception accurately. Traditionally, the Semmes-Weinstein monofilaments were used to measure the static one-point discrimination threshold. A new sensory testing instrument, the Pressure-Specifying Sensory Device, was used to obtain normative data from the index and little finger of the dominant hand in 35 people ranging in age from 16 to 83 with no known neurologic impairment. Pressure perceptions for static one- and two-point discrimination (s1PD, s2PD) and moving one- and two-point discrimination (m1PD, m2PD) were recorded. The mean values (+/- SD) were 0.13 +/- 0.06, 0.24 +/- 0.12, 0.22 +/- 0.10, and 0.26 +/- 0.13 gm/mm2 for s1PD, s2PD, m1PD, and m2PD, respectively, on the index finger and 0.07 +/- 0.05, 0.16 +/- 0.12, 0.17 +/- 0.07, and 0.21 +/- 0.14 gm/mm2 for s1PD, s2PD, m1PD, and m2PD, respectively, for the little finger. The little finger was significantly more sensitive than the index finger (p less than 0.001). There was no significant change in pressure perception with increasing age.     

Two-point discrimination distances in the normal hand and forearm: application to various methods of fingertip reconstruction.

Two-point discrimination in the hand and forearm is best during the third decade of life. In the fingertips, the ulnar digits are more discriminating than the radial digits. Males and females have equal two-point discrimination during each age decade. Fingertips are twice as discriminating as the thenar and hypothenar areas, and the thenar and hypothenar areas are twice as discriminating as the volar side of the wrist; the wrist is twice as discriminating as the forearm. The Kleinert and Kutler flaps demonstrated the best two-point discrimination among the repaired fingertips.     

Laterality and sex differences in tactile detection and two-point thresholds modified by body surface area and body fat ratio

Tactile detection and two-point discrimination tests are commonly used in neurological examinations. However, questions remain about the influence of both body and patient characteristics on test thresholds. The left side of the body has sometimes been reported more tactilely sensitive than the right, and females are said to be more sensitive than males. We measured tactile detection and two-point discrimination thresholds on the finger, palm, and forehead of a large sample of young adults (N?=?171), examining laterality and sex differences, and the effects of body surface area (BSA) and body fat ratio (BFR). In tactile detection, there were no effects of laterality, BSA, or BFR, although females had lower thresholds than males. In two-point discrimination, there was an effect of laterality, with lower thresholds on the left side. This probably reflects hemispheric spatial processing differences. A significant BFR effect implies that subcutaneous fat affects skin deformation, but there were no effects of sex or BSA. The two-point discrimination findings differ in several respects from recent findings using grating orientation discriminations. A small positive correlation between the tasks, falling far short of test–retest reliabilities, indicates that they use largely disjoint but partially overlapping processes.     

Somatosensory Abnormalities for Painful and Innocuous Stimuli at the Back and at a Site Distinct from the Region of Pain in Chronic Back Pain Patients

Chronic low back pain (CLBP) was shown to be associated with pathophysiological changes at several levels of the sensorimotor system. Changes in sensory thresholds have been reported but complete profiles of Quantitative Sensory Testing (QST) were only rarely obtained in CLBP patients. The aim of the present study was to investigate comprehensive QST profiles in CLBP at the painful site (back) and at a site distinct from their painful region (hand) and to compare these data with similar data in healthy controls. We found increased detection thresholds in CLBP patients compared to healthy controls for all innocuous stimuli at the back and extraterritorial to the painful region at the hand. Additionally, CLBP patients showed decreased pain thresholds at both sites. Importantly, there was no interaction between the investigated site and group, i.e. thresholds were changed both at the affected body site and for the site distinct from the painful region (hand). Our results demonstrate severe, widespread changes in somatosensory sensitivity in CLBP patients. These widespread changes point to alterations at higher levels of the neuraxis or/and to a vulnerability to nociceptive plasticity in CLBP patients.     

Laterality and sex differences in tactile detection and two-point thresholds modified by body surface area and body fat ratio

Tactile detection and two-point discrimination tests are commonly used in neurological examinations. However, questions remain about the influence of both body and patient characteristics on test thresholds. The left side of the body has sometimes been reported more tactilely sensitive than the right, and females are said to be more sensitive than males. We measured tactile detection and two-point discrimination thresholds on the finger, palm, and forehead of a large sample of young adults (N=171), examining laterality and sex differences, and the effects of body surface area (BSA) and body fat ratio (BFR). In tactile detection, there were no effects of laterality, BSA, or BFR, although females had lower thresholds than males. In two-point discrimination, there was an effect of laterality, with lower thresholds on the left side. This probably reflects hemispheric spatial processing differences. A significant BFR effect implies that subcutaneous fat affects skin deformation, but there were no effects of sex or BSA. The two-point discrimination findings differ in several respects from recent findings using grating orientation discriminations. A small positive correlation between the tasks, falling far short of test-retest reliabilities, indicates that they use largely disjoint but partially overlapping processes.     

Simultaneous multiple toe transfers in hand reconstruction

Our experience with simultaneous transfer of two or more toe units to the same hand where multiple digits were missing is presented. Forty-six toes from 38 feet were transferred to reconstruct 19 hands in 19 patients. The transfers consisted of 7 combined second and third toe units and 32 single toes. Three patients had a primary and 16 patients had a secondary reconstruction. There was one complete and one partial failure. The two-point discrimination ranged from 6 mm to protective sensation. Total active movement averaged 57 degrees in the thumb and 127, 93, 71, and 68 degrees, respectively, in the fingers reconstructed at middle phalanx, proximal phalanx, metacarpophalangeal joint, and metacarpal head. Pulp-to-pulp pinch averaged 2.4 kg in patients who had thumbs reconstructed and averaged 3.0 kg in patients who had normal thumbs. There was no cold intolerance, and no significantly disabled foot occurred except one with scissoring deformity. Simultaneous multiple toe transfer in hand reconstruction is feasible without increased complications both in primary and secondary wound conditions. It is time-effective and cost-effective.     

Autogenous vein graft repair of digital nerve defects in the finger: a retrospective clinical study

Twenty-two digital nerve repairs were performed in the finger using autogenous vein grafts. Eighty-two percent of the repairs were available for follow-up. Results of sensibility return were assessed using moving two-point discrimination, Semmes-Weinstein monofilaments, and vibratory testing. Two-point discrimination averaged 4.6 mm for 11 acute digital nerve repairs using vein conduits 1 to 3 cm in length. Delayed digital nerve repair with vein conduits yielded poor results. Semmes-Weinstein values demonstrated comparable levels of return of slowly adapting fiber/receptors to the quickly adapting fiber/receptors, as evidenced by moving two-point discrimination tests. Vibratory sensibility was present in all. A review of previous experiences with end-to-end digital neurorrhaphies and digital nerve grafting suggests that repair of 1- to 3-cm gaps in digital nerves with segments of autologous vein grafts appears to give comparable results to nerve grafting. Further laboratory and clinical research is necessary to better define the role of interpositional vein conduits for repair of peripheral nerves.     

Stimulus features relevant to the perception of sharpness and mechanically evoked cutaneous pain

Mechanical probes of various sizes and shapes were used to determine thresholds for the perception of pressure, sharpness, and pain on the human finger. As force increased, perception changed from dull pressure to sharp pressure to sharp pain. With the smallest probe (0.01 mm2), sharpness threshold was very close to pressure threshold. As probe size increased, sharpness and pain threshold expressed in terms of force) increased in proportion to probe circumference (not probe area), whereas pressure threshold increased relatively little. Pain and sharpness thresholds also increased as probe angle became obtuse. There was a statistically significant increase in both thresholds with a probe angle change of 15 degrees. Thus, both size and shape are necessary to describe a mechanical stimulus adequately, and pressure (force/area) is not a sufficient metric for pain studies. Thresholds varied at different skin sites on the finger. The dorsal surface had lower thresholds than the volar surface, but the difference between the two areas was not always statistically significant. The compliance of the skin (e.g., the amount of indentation produced by a given force) exhibited no relation to sharpness or pain threshold, whether considered within subjects at various skin sites, or across subjects at the same skin site. Comparison of the perceptual thresholds with the thresholds for nociceptors determined in electrophysiological studies indicates that the sensation of nonpainful sharpness is likely to be mediated by nociceptors. Furthermore, considerably more than threshold activation of nociceptors is necessary for normal pain perception.     

A randomized prospective study of polyglycolic acid conduits for digital nerve reconstruction in humans

This article reports the first randomized prospective multicenter evaluation of a bioabsorbable conduit for nerve repair. The study enrolled 98 subjects with 136 nerve transections in the hand and prospectively randomized the repair to two groups: standard repair, either end-to-end or with a nerve graft, or repair using a polyglycolic acid conduit. Two-point discrimination was measured by a blinded observer at 3, 6, 9, and 12 months after repair. There were 56 nerves repaired in the control group and 46 nerves repaired with a conduit available for follow-up. Three patients had a partial conduit extrusion as a result of loss of the initially crushed skin flap. The overall results showed no significant difference between the two groups as a whole. In the control group, excellent results were obtained in 43 percent of repairs, good results in 43 percent, and poor results in 14 percent. In those nerves repaired with a conduit, excellent results were obtained in 44 percent, good results in 30 percent, and poor results in 26 percent (p = 0.46). When the sensory recovery was examined with regard to length of nerve gap, however, nerves with gaps of 4 mm or less had better sensation when repaired with a conduit; the mean moving two-point discrimination was 3.7 +/- 1.4 mm for polyglycolic acid tube repair and 6.1 +/- 3.3 mm for end-to-end repairs (p = 0.03). All injured nerves with deficits of 8 mm or greater were reconstructed with either a nerve graft or a conduit. This subgroup also demonstrated a significant difference in favor of the polyglycolic acid tube. The mean moving two-point discrimination for the conduit was 6.8 +/- 3.8 mm, with excellent results obtained in 7 of 17 nerves, whereas the mean moving two-point discrimination for the graft repair was 12.9 +/- 2.4 mm, with excellent results obtained in none of the eight nerves (p < 0.001 and p = 0.06, respectively). This investigation demonstrates improved sensation when a conduit repair is used for nerve gaps of 4 mm or less, compared with end-to-end repair of digital nerves. Polyglycolic acid conduit repair also produces results superior to those of a nerve graft for larger nerve gaps and eliminates the donor-site morbidity associated with nerve-graft harvesting.     

Quantitation of breast sensibility following reduction mammaplasty: a comparison of inferior and medial pedicle techniques

The preservation of sensitivity within the nipple-areola complex is of paramount importance to patients presenting for reconstructive and aesthetic breast procedures. Previous attempts to measure sensation in the breast before and after surgery have relied primarily on the Semmes-Weinstein monofilament test, which is an imprecise study that measures the logarithm of force necessary to bend a series of six to 20 filaments. Within the last 10 years, various authors have published normative pressure threshold data for the breast that have varied by a magnitude of greater than 10-fold. Recently, precise anatomic studies have been performed that have elucidated the innervation of the nipple-areola complex medially and laterally from cutaneous branches of the intercostal nerves. Despite this knowledge, no quantitative sensibility studies have yet been performed that compare postoperative sensation when medially versus laterally innervated pedicles have been used in reduction mammaplasty. The present study is the first to use computer-assisted neurosensory testing to generate normal breast sensation data and to compare sensory outcomes between the inferior and the medial pedicle techniques of reduction mammaplasty.A total of 34 patients were divided into four groups and underwent breast sensory testing (67 breasts total) using the Pressure-Specified Sensory Device, a computer-assisted force transducer that measures static and moving one and two-point discrimination. Sensation in the nipple and in the four quadrants of the areola was measured. Groups I and II were composed of 17 unoperated controls with breast sizes ranging from 34A to 36C (group I; 18 breasts) and 36DD to 46EE (group II; 16 breasts) who presented to a general plastic surgery clinic. Groups III and IV were composed of 17 patients who underwent either medial or inferior pedicle reduction mammaplasty between July of 1997 and March of 1999. Pressure thresholds in the most sensitive breasts were as low as 0.3 g/mm2, a marked contrast to data from previous studies using Semmes-Weinstein monofilaments documenting the lowest recordable pressure threshold as greater than 2 g/mm2. Several findings from previous studies using Semmes-Weinstein monofilament testing were confirmed in unoperated controls, including an inverse relationship between sensitivity and breast size, superior nipple sensitivity when compared with the areola, and significant interpatient variability with respect to static and moving two-point discrimination among women matched according to age and breast size. When comparing medial with inferior pedicle reduction mammaplasty patients, it was found that despite significantly greater reductions using the medial pedicle technique (mean of 1.7 kg versus 1.1 kg of breast tissue removed), there were no significant differences in postoperative sensory outcomes in the sample size of 17 patients. Furthermore, within each group of patients undergoing either the medial or inferior pedicle technique, the amount of breast tissue removed did not correlate with postoperative sensory outcomes.Computer-assisted quantitative neurosensory testing is a highly accurate technique for measuring sensibility. The use of this technology demonstrates a 10-fold difference in measurable sensory thresholds in normal patients from preexisting data using Semmes-Weinstein monofilaments. Advances in measurement methods have allowed the authors to compare postoperative sensory outcomes reliably using two popular techniques of reduction mammaplasty.     

Haptic discrimination of size and texture in squirrel monkeys ( Saimiri sciureus )

The present study analyzed haptic abilities of four squirrel monkeys. Using a two-alternative forced-choice procedure, stimuli were presented in a visually opaque box, allowing unrestrained test subjects to grab through a small opening and touch the discriminanda. Difference thresholds were determined by a modified method of limits. In the first experiment we determined size difference thresholds for the discrimination of circular cylinders using standard stimuli differing in diameter from 10 mm to 35 mm. In the second experiment a texture difference threshold was obtained for the discrimination of grooved surfaces (groove width 2-7 mm).The squirrel monkeys achieved a mean size difference threshold of 8% stimulus difference. The linear increase of absolute thresholds as a function of the starting stimulus size showed that haptic size discriminations in squirrel monkeys correspond to Weber's law. Three of the animals achieved a texture difference of 10% stimulus difference, while one monkey showed a distinctively lower haptic acuity. An analysis of the exploratory behavior points to a subject-related difference in the significance of cutaneous and kinesthetic information during size discriminations. Whereas differences in the animals' exploratory behavior did not correlate with the size difference threshold a subject achieved, different thresholds for texture discrimination can be explained by the different exploratory procedures the monkeys used to touch grooved surfaces. The low difference thresholds determined for the squirrel monkeys in the present study point to the significance of unrestrained test conditions for the assessment of the haptic capacity of a species.     

Haptic discrimination of size and texture in squirrel monkeys (Saimiri sciureus)

The present study analyzed haptic abilities of four squirrel monkeys. Using a two-alternative forced-choice procedure, stimuli were presented in a visually opaque box, allowing unrestrained test subjects to grab through a small opening and touch the discriminanda. Difference thresholds were determined by a modified method of limits. In the first experiment we determined size difference thresholds for the discrimination of circular cylinders using standard stimuli differing in diameter from 10 mm to 35 mm. In the second experiment a texture difference threshold was obtained for the discrimination of grooved surfaces (groove width 2-7 mm). The squirrel monkeys achieved a mean size difference threshold of 8% stimulus difference. The linear increase of absolute thresholds as a function of the starting stimulus size showed that haptic size discriminations in squirrel monkeys correspond to Weber's law. Three of the animals achieved a texture difference of 10% stimulus difference, while one monkey showed a distinctively lower haptic acuity. An analysis of the exploratory behavior points to a subject-related difference in the significance of cutaneous and kinesthetic information during size discriminations. Whereas differences in the animals' exploratory behavior did not correlate with the size difference threshold a subject achieved, different thresholds for texture discrimination can be explained by the different exploratory procedures the monkeys used to touch grooved surfaces. The low difference thresholds determined for the squirrel monkeys in the present study point to the significance of unrestrained test conditions for the assessment of the haptic capacity of a species.     

Influence of surface anesthesia on the pressure pain threshold measured with different-sized probes

Transcutaneous pressure with pressure probes of arbitrary diameters have been commonly used for measuring the threshold and magnitude of muscle pain, yet this procedure lacks scientific validation. To examine the valid probe dimensions, we conducted physiological experiments using 34 human subjects. Pin-prick pain, pressure pain threshold (PPT) to pressure probes of various diameters, heat pain threshold, and electrical pain threshold of deep tissues were measured before and after application of surface lidocaine anesthesia to the skin surface over the brachioradial muscle in a double-blinded manner. The anesthesia neither affected PPT with larger probes (diameters: 1.6 and 15?mm) nor increased electric pain threshold of deep structures, whereas it diminished pain count in pin-prick test and PPT with a 1.0?mm diameter probe, suggesting that mechanical pain thresholds measured with 1.6 and 15?mm probes reflect the pain threshold of deep tissues, possibly muscle. Pain thresholds to heat did not change after application of the anesthesia. These results suggest that larger pressure probes can give a better estimation of muscular pain threshold.     

Influence of surface anesthesia on the pressure pain threshold measured with different-sized probes

Transcutaneous pressure with pressure probes of arbitrary diameters have been commonly used for measuring the threshold and magnitude of muscle pain, yet this procedure lacks scientific validation. To examine the valid probe dimensions, we conducted physiological experiments using 34 human subjects. Pin-prick pain, pressure pain threshold (PPT) to pressure probes of various diameters, heat pain threshold, and electrical pain threshold of deep tissues were measured before and after application of surface lidocaine anesthesia to the skin surface over the brachioradial muscle in a double-blinded manner. The anesthesia neither affected PPT with larger probes (diameters: 1.6 and 15 mm) nor increased electric pain threshold of deep structures, whereas it diminished pain count in pin-prick test and PPT with a 1.0 mm diameter probe, suggesting that mechanical pain thresholds measured with 1.6 and 15 mm probes reflect the pain threshold of deep tissues, possibly muscle. Pain thresholds to heat did not change after application of the anesthesia. These results suggest that larger pressure probes can give a better estimation of muscular pain threshold.     

Ethnic-specific BMI and waist circumference thresholds

BMI and waist circumference (WC) are used to identify individuals with elevated obesity-related health risks. The current thresholds were derived largely in populations of European origin. This study determined optimal BMI and WC thresholds for the identification of cardiometabolic risk among white and African-American (AA) adults. The sample included 2096 white women, 1789 AA women, 1948 white men, and 643 AA men aged 18-64 years. Elevated cardiometabolic risk was defined as ≥2 risk factors (blood pressure ≥ 130/85 mm Hg; glucose ≥100 mg/dl; triglycerides ≥150 mg/dl; high-density lipoprotein-cholesterol <40 mg/dl (men) or <50 mg/dl (women)). Receiver Operating Characteristic (ROC) curves were used to identify optimal BMI and WC thresholds in each sex-by-ethnicity group. The optimal BMI thresholds were 30 kg/m2 in white women, 32.9 kg/m2 in AA women, 29.1 kg/m2 white men, and 30.4 kg/m2 in AA men, whereas optimal WC thresholds were 91.9 cm in white women, 96.8 cm in AA women, 99.4 in white men, and 99.1 cm in AA men. The sensitivities at the optimal thresholds ranged from 63.5 to 68.5% for BMI and 68.4 to 71.0% for WC and the specificities ranged from 64.2 to 68.8% for BMI and from 68.5 to 71.0% for WC, respectively. In general, the optimal BMI and WC thresholds approximated currently used thresholds in men and in white women. There are no apparent ethnic differences in men; however, in AA women the optimal BMI and WC values are ~3 kg/m2 and 5 cm higher than in white women.     

Determination of hand surface area by sex and body shape using alginate

Hand surface area (HSA) has been utilized for burned skin area estimation in burn therapy, heat exchange in thermal physiology, exposure assessment in occupational toxicology, and the development of manual equipment/ protective gloves in ergonomics. The purpose of this study was to determine the hand surface area to the total body surface area (BSA) and derive a formula for estimating HSA. Thirty-four Korean males (20-60 years old; 158.5-187.5 cm in height; 48.5-103.1 kg in body weight) and thirty-one Korean females (20-63 years old; 140.6-173.1 cm; 36.8-106.1 kg) participated as subjects. The HSA and BSA of 65 subjects were directly measured using alginate. The measurements showed 1) the surface area of the hand had a mean of 448 (371-540) cm(2) for males, and 392 (297-482) cm(2) for females. 2) The hand as a percentage of the total body surface area for males and females was 2.5% and 2.4% respectively, showing no significant difference. 3) The hand as a percentage of BSA by body shape was 2.5% for the lean group and 2.3% for overweight people (p=0.001). 4) When estimating the surface area of a hand, formulae based on hand length or hand circumference were more valid than formulae based on height and body weight. We obtained the following formula for estimating HSA: Estimated HSA(cm(2))=1.219 Hand length(cm) x Hand circumference(cm).     

1．06μm激光致皮肤痛觉效应的研究

目的：研究1．06μm激光所致人手背皮肤的痛觉效应。方法：以输出波长为1．06μm的脉冲Nd：YAG激光照射人手背皮肤,记录每次刺激激光的能量以及受试者的反应。采用加权概率单位算法计算诱发痛觉概率为50％时对应的激光剂量ED50,即为痛觉阈值。改变光斑大小和脉冲宽度,测定三种不同刺激条件下的痛觉阈值,并探索温度对激光所致痛觉效应的影响。结果：当皮肤温度约为30℃,分别使用光斑直径1．20mm、脉冲宽度85μs,光斑直径1．20mm、脉冲宽度20ns和光斑直径2．56mm、脉冲宽度20ns的激光刺激时,痛觉阈值分别为394mJ／mm^2、36．4mJ／mm^2和8．92mJ／mm^2。在第一种刺激条件下,当皮肤温度为25℃时,剂量为383mJ／mm^2的激光诱发痛觉的概率为16．7％;当皮肤温度为39℃时,剂量为361mJ／mm^2的激光诱发痛觉的概率为56．7％。结论：1．06“m激光所致痛觉的阈值随脉冲宽度的减小、光斑面积的增大和皮肤表面温度的增加而减小。     

Sensory reconstruction of the fingertip using the bilaterally innervated sensory cross-finger flap

The authors present a series of 15 patients with large soft-tissue defects of the fingertips as a prospective, nonrandomized study. In all cases, reconstruction was achieved using a bilaterally innervated sensory cross-finger flap. This sensory fasciocutaneous flap relies on the dorsal branch of the proper digital nerves, which branch off at the level of the head of the proximal phalanx; sensory supply to the dorsal skin of the middle phalanx is thus ensured. The reconstructive procedure consists of two steps. First, the contralateral dorsal branch of the proper digital nerve is elevated with the flap at proximal interphalangeal joint level. Microsurgical coaptation is performed to the proximal nerve stump of the injured fingertip. After 3 weeks, when the pedicle is dissected, the second nerve is dissected and coapted. Clinical results were evaluated after 12 months. Because the regenerative distance is only 1.5 to 2.5 cm, good sensory regeneration should be expected. In nine of 16 flaps, sensory quality of S2+ (Highet) was present in the flap after 3 weeks. After 12 months, two-point discrimination was present in all patients, the values ranging between 2 and 6 mm (for two-point discrimination), with an average of 3.6 mm. The rate of complications was low. With acceptable additional operative action, a good functional result can be achieved. The indications of this method are discussed in comparison with other methods of fingertip reconstruction.