RESUMEN
BACKGROUND: Direct and quantitative measurement of median nerve strain within the carpal tunnel has been difficult because of the technical limitations associated with conventional devices. We used capacitive sensors (C-stretch), which are thin and flexible, to measure the median nerve strain within the carpal tunnel. METHODS: We used 12 fresh frozen upper extremity specimens. The transverse carpal ligament was left in situ, and we attached the sensor to the palmar surface of the median nerve to measure the nerve strain at 60 degrees of wrist extension. The sensor measured the median nerve strain at both the carpal tunnel site and the proximal to the carpal tunnel site before and after the carpal tunnel release. The amount of nerve excursion during wrist extension was also measured with the length change of the attached suture by a digital caliper. FINDINGS: The mean median nerve strain within the carpal tunnel [8.07% (95 %CI:7.17-8.97)] was significantly higher than that proximal to the carpal tunnel [5.21% (95 %CI:4.46-5.97)] at the wrist extension. There was no significant difference of the mean nerve excursion within and proximal to the carpal tunnel. The mean nerve strain and excursion were unaffected by carpal tunnel release. INTERPRETATION: These results indicated that wrist extension position might lead to increased strain on the median nerve within the carpal tunnel compared with at the proximal to the carpal tunnel. We believe that the current study might provide new information and help us understand the pathogenesis of carpal tunnel syndrome.
Asunto(s)
Síndrome del Túnel Carpiano , Nervio Mediano , Humanos , Muñeca , Síndrome del Túnel Carpiano/cirugía , Ligamentos Articulares/cirugía , CadáverRESUMEN
BACKGROUND: Manual evaluation is an important method for assessing ankle instability, but it is not quantitative. Capacitance-type sensors can be used to measure the distance on the basis of the capacitance value. We applied the sensor to the noninvasive device for measuring ankle instability and showed its utility. METHODS: First, 5 ankles embalmed by Thiel's method were used in an experiment using a cadaver. The capacitance-type sensor was fixed alongside the anterior talofibular ligament (ATFL) of a specially made brace, and the anterior drawer test was performed. The test had been performed for the intact ankle, with the ATFL transected and with both the ATFL and calcaneofibular ligament (CFL) transected. The anterior drawer distance was calculated by the sensor. Intra- and interinvestigator reliability were also analyzed.Next, as a clinical study, a brace with a sensor was fitted to 22 ankles of 20 patients with a history of ankle sprain. An anterior drawer test at a load of 150 N was conducted using a Telos stress device. The anterior drawer distances measured by the sensor and based on radiographic images were then compared. RESULTS: The mean anterior drawer distances were 3.7 ± 1.0 mm for the intact cadavers, 6.1 ± 1.6 mm with the ATFL transected (P < .001), and 7.9 ± 1.8 mm with the ATFL and CFL transected (P < .001). The intrainvestigator intraclass correlation coefficients (ICCs) were 0.862 to 0.939, and the interinvestigator ICC was 0.815. In the experiments on patients, the mean anterior drawer distance measured by the sensor was 2.9 ± 0.9 mm, and it was 2.7 ± 0.9 mm for the radiographic images. The correlation coefficient between the sensor and the radiographic images was 0.843. CONCLUSION: We quantitatively evaluated anterior drawer laxity using a capacitance-type sensor and found it had high reproducibility and strongly correlated with stress radiography measurements in patients with ankle instability. Capacitance-type sensors can be used for the safe, simple, and accurate evaluation of ankle instability.