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Area and shape changes of the carpal tunnel in response to tunnel pressure.

ABSTRACT: Carpal tunnel mechanics is relevant to our understanding of median nerve compression in the tunnel. The compliant characteristics of the tunnel strongly influence its mechanical environment. We investigated the distensibility of the carpal tunnel in response to tunnel pressure. A custom balloon device was designed to apply controlled pressure. Tunnel cross sections were obtained using magnetic resonance imaging to derive the relationship between carpal tunnel pressure and morphological parameters at the hook of hamate. The results showed that the cross-sectional area (CSA) at the level of the hook of hamate increased, on average, by 9.2% and 14.8% at 100 and 200?mmHg, respectively. The increased CSA was attained by a shape change of the cross section, displaying increased circularity. The increase in CSA was mainly attributable to the increase of area in the carpal arch region formed by the transverse carpal ligament. The narrowing of the carpal arch width was associated with an increase in the carpal arch. We concluded that the carpal tunnel is compliant to accommodate physiological variations of the carpal tunnel pressure, and that the increase in tunnel CSA is achieved by increasing the circularity of the cross section.

SUBMITTER: Li ZM

PROVIDER: S-EPMC3170497 | biostudies-literature | 2011 Dec

REPOSITORIES: biostudies-literature

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Area and shape changes of the carpal tunnel in response to tunnel pressure.

Li Zong-Ming ZM Masters Tamara L TL Mondello Tracy A TA

Journal of orthopaedic research : official publication of the Orthopaedic Research Society 20110523 12

Carpal tunnel mechanics is relevant to our understanding of median nerve compression in the tunnel. The compliant characteristics of the tunnel strongly influence its mechanical environment. We investigated the distensibility of the carpal tunnel in response to tunnel pressure. A custom balloon device was designed to apply controlled pressure. Tunnel cross sections were obtained using magnetic resonance imaging to derive the relationship between carpal tunnel pressure and morphological parameter ...[more]

PMID: 21608024

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Project description:Background:Owing to the compressive nature of the neuropathy, patients with carpal tunnel syndrome (CTS) have prolonged distal motor latency (DML), sensory nerve latency (SNL), median nerve swelling and restricted median nerve mobility. The purpose of this study was to noninvasively augment carpal tunnel space using radioulnar wrist compression (RWC) and evaluate its effects on median nerve pathological properties in patients with CTS. It was hypothesized that the RWC intervention would reduce the median nerve DML, SNL and cross-sectional area (CSA) and enhance longitudinal median nerve mobility in patients. with CTS. Methods:Eleven patients diagnosed with CTS participated in this study. A portable RWC intervention splint was developed to apply 10 N of compressive force across the wrist. Three daily sessions of RWC were performed over 4 weeks of intervention (15 min per session, 45 min per day, 7 days per week). Each 15-min session consisted of three 5-min blocks of RWC, with a 1-min rest in between consecutive blocks. Patients were evaluated at Week 0 (baseline), Week 2 (mid-intervention) and Week 4 (end of intervention). DML and SNL of the median nerve were evaluated using established nerve conduction study techniques. Median nerve CSA at the distal wrist crease was obtained by ultrasound imaging. Median nerve motion associated with finger flexion/extension was captured by dynamic ultrasound imaging and quantified using a speckle cross-correlation algorithm. Finger flexion/extension was recorded using an electrogoniometer. The slope of the regressed linear equation of median nerve displacement as a function of finger flexion angle was used to quantify nerve mobility. Results:Patients with CTS showed significantly decreased DML (p = 0.048) and median nerve CSA (p < 0.001) and increased nerve mobility (p < 0.001) at mid-intervention compared to baseline. However, DML, CSA and mobility of the median nerve did not differ significantly between Weeks 2 and 4 (p = 0.574, 1.00 and 0.139, respectively). Median nerve SNL was not significantly affected throughout the 4-week intervention (p = 0.330 for Week 0 vs. 2; p = 1.00 for Week 2 vs. 4). Conclusion:This study revealed that RWC intervention with 10-N force applied to the wrist in the radioulnar direction could restore impaired neurophysiological and biomechanical functions of the median nerve. The beneficial effects of RWC intervention for the median nerve were in evidence after a relatively short period of two weeks. These functional improvements could be explained by intermittent decompression of the median nerve via RWC-induced augmentation of the carpal arch. The translational potential of this article:Biomechanically manipulating the carpal tunnel by RWC decompresses the median nerve and has the potential to become an alternative treatment for CTS.

Project description:BackgroundLimited evidence informs whether pre-operative values of two-point discrimination (2PD) in patients with carpal tunnel syndrome predict response to surgery.Questions/purposesThe primary aim of this study was to determine the predictive value of pre-operative 2PD scores on outcomes following carpal tunnel release (CTR). In particular, we sought to evaluate whether a clinically relevant 2PD threshold exists that can predict symptomatic response after surgery.MethodsPatients who underwent CTR between 2014 and 2018 were retrospectively reviewed. Static 2PD scores in each digit, as well as Quick Disabilities of the Arm, Shoulder, and Hand (QuickDASH) and Levine-Katz scores, were collected from pre- and post-operative records. Pearson correlation coefficients assessed the relationship between pre-operative 2PD, early post-operative 2PD, and patient-reported outcome scores. Poor 2PD was defined as 2PD greater than 10 mm.ResultsEighty-nine hands in 73 patients with a mean follow-up of 1.8 years were analyzed. Mean pre- and post-operative 2PD was 7.2 mm and 6.4 mm, respectively, in the most affected digit when measurable. Twenty patients had poor 2PD scores pre-operatively and 14 post-operatively. There was a positive correlation between pre- and early post-operative 2PD scores but no correlation between pre-operative 2PD score and final post-operative functional scores. Only 30% of patients with poor pre-operative 2PD scores demonstrated improvement, compared with 69% of patients with measurable 2PD.ConclusionWe found that greater pre-operative 2PD scores predicted greater early post-operative 2PD scores but did not lead to worse functional outcome scores post-operatively. Patients with poor pre-operative 2PD scores were likely to demonstrate improvement in functional outcomes scores, while having less reliable improvement in 2PD after CTR. Patients with poor 2PD should be counseled that improvement of tactile perception is less predictable.

Project description:BackgroundAt present, the most commonly used diagnostic method of carpal tunnel syndrome (CTS) is based on clinical manifestations and electrophysiology, but the electrophysiology is not cheap, invasive, and lacks the presentation of peripheral nerve conditions, which is exactly the advantage of ultrasound (US). The purpose of this study was to evaluate the accuracy and effectiveness of US in the diagnosis of CTS by calculating the cross-sectional area (CSA) at the carpal tunnel and proximally at the level of the pronator quadratus muscle., and to find an appropriate index that can be used to achieve the diagnosis in a more cost-effective manner.MethodsForty-three wrists from 35 symptomatic CTS patients and 23 wrists from 18 asymptomatic volunteers were evaluated. Diagnosis in the CTS group was based on the American Academy of Neurology clinical diagnostic criteria. The ultrasonic probe was placed at the carpal tunnel and the distal 1/3 of the pronator muscle respectively, and the carpal tunnel cross-sectional area (CSAC) and the proximal cross-sectional area (CSAP) was calculated, with a further calculation of their difference (ΔCSA) and ratio (R-CSA).ResultsThere was a significant difference between the 2 groups regarding mean ± standard deviation (SD) of CSAC, CSAP, ΔCSA, and R-CSA (P<0.01). The cutoff value of 12.14 mm2 for CSAC had a sensitivity and specificity of 90.7% and 100%, respectively; the cutoff value of 1.235 mm2 for R-CSA had a sensitivity and specificity of 97.67% and 95.65%, respectively; and the cutoff value of 2.035 mm2 for ΔCSA had a sensitivity and specificity of 100% and 100%, respectively. Therefore, US was found to be an effective method for the diagnosis of CTS. Receiver operating characteristic curve (ROC) analysis of all patients showed area under the curve (AUC) was 0.9778 for CSAC, 0.9949 for R-CSA and 1.000 for ΔCSA.ConclusionsUS can provide reference values for the diagnosis of CTS. CSAC, ΔCSA, and R-CSA can be used for CTS diagnosis and evaluation. The ROC curve analysis showed that among the 3 values, ΔCSA was the most useful in the diagnosis of patients with CTS. ΔCSA is considered a valid diagnostic value for CTS, as its threshold of 2.04 mm2 showed the highest sensitivity and specificity.

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Area and shape changes of the carpal tunnel in response to tunnel pressure.

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Area and shape changes of the carpal tunnel in response to tunnel pressure.

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