J Korean Neurosurg Soc.  2013 Sep;54(3):232-235. 10.3340/jkns.2013.54.3.232.

Quantitative Evaluation of Median Nerve Motor Function in Carpal Tunnel Syndrome Using Load Cell : Correlation with Clinical, Electrodiagnostic, and Ultrasonographic Findings

• Kim DH
• Park SB
• Lee SH
• Son YJ
• Chung GS
• Yang HJ

• KMID: 2190903
• DOI: http://doi.org/10.3340/jkns.2013.54.3.232

Abstract

OBJECTIVE
Major complaints of carpal tunnel syndrome (CTS) are sensory components. However, motor deficit also impedes functional status of hand. Contrary to evaluation of sensory function, the objective, quantitative evaluation of median nerve motor function is not easy. The motor function of median was evaluated quantitatively using load cell and its correlation with findings of electrodiagnostic study (EDS) was evaluated.
METHODS
Objective motor function of median nerve was evaluated by load cell and personal computer-based measurement system. All of the measurement was done in patients diagnosed as having idiopathic CTS by clinical features and EDS findings. The strength of thumb abduction and index finger flexion was measured in each hand three times, and the average value was used to calculate thumb index ratio (TIR). The correlation of TIR with clinical, EDS, and ultrasonographic findings were evaluated.
RESULTS
The TIR was evaluated in 67 patients (119 hands). There were 14 males and 53 females, mean age were 57.6 years (range 28 to 81). The higher preoperative nerve conductive studies grade of the patients, the lower TIR was observed [p<0.001, analysis of variance (ANOVA)]. TIR of cases with thenar atrophy were significantly lower than those without (p<0.001, t-test). TIR were significantly lower in patients with severe median nerve swelling in ultrasonography (p=0.042, ANOVA).
CONCLUSION
Measurements of median nerve motor function using load cell is a valuable evaluation tool in CTS. It might be helpful in detecting subclinical motor dysfunction before muscle atrophy develops.

Keyword

Carpal tunnel syndrome; Thumb abduction strength; Load cell; Electrodiagnostic study; Ultrasonography

MeSH Terms

Atrophy
Carpal Tunnel Syndrome*
Evaluation Studies as Topic*
Female
Fingers
Hand
Humans
Male
Median Nerve*
Muscular Atrophy
Sensation
Thumb
Ultrasonography

Figure

• 

  Fig. 1 Device and program for measuring thumb abduction strength. The device (A) is composed of base plate with velcro strap, load cell mounted on adjustable arm. The screen capture (B) shows graphic output of measured muscle strength in kilogram force.

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  Fig. 2 The measurement of thumb abduction and index flexion strength. Thumb abduction strength is measured by placing load cell at the radial border of the thumb interphalangeal joint flexion crease (A). Index flexion strength is measured by placing load cell at the distal interphalangeal joint flexion crease (B).

• 

  Fig. 3 The difference of TIR according to NCS grade. The TIR of NCS grade extremely severe was significantly lower than those of other NCS grades in post-hoc analysis. TIR : thumb index ratio, NCS : nerve conductive studies.

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  Fig. 4 The difference of TIR according to presence or absence of thenar atrophy on physical examination. TIR : thumb index ratio.

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  Fig. 5 The difference of TIR according to WFR. The patients with higher WFR have significantly lower TIR in post-hoc analysis (p=0.034). TIR : thumb index ratio, WFR : wrist to forearm ratio.

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