Through examination of many of the available examination forms on the market for chiropractic physicians, it has been noted that there seems to be a dependency on the grip dynamometer as one of the means for assessment of motor function in the upper extremities. While grip strength is a valuable measure of upper extremity dysfunction, its clinical utility in assessment of neurological deficits secondary to cervical radiculopathy is lacking. In a series of 846 consecutive cases of cervical radiculopathy, the incidence of neuromuscular deficits were as follows:1
Triceps muscle 37%
Biceps muscle 28%
Deltoid muscle 1.9%
Grip muscles 0.6%
As one can see from this series, the incidence of grip strength abnormalities associated with cervical radiculopathies is extremely low. This is primarily due to the fact that for all of the cervical discs associated with the roots of the brachial plexus, the incidence of C7/DT1 cervical disc herniation is the least common of all. The order of involvement from most common levels of involvement to least common levels is:
C5/6 level
C6/7 level
C4/5 level
C3/4 level
C7/T1 level
As you can see from these statistics, cervical radiculopathy involves nerve root levels outside the scope of testing of the grip dynamometer. In order to close loopholes in the examination process, the assessment of upper extremity strength should include an assessment of the following muscle groups in order for the doctor to properly cover his bases in the radicular assessment.
Deltoid muscles C5
Biceps muscles C5, C6
Extensor carpi radialis C6
Extensor carpi ulnaris C7
Wrist flexors C7
Finger extensors C7
Finger flexor muscles C8
Interossei muscles T1
References
1. Dillin, W., et al. "Cervical Radiculopathy: A Review." Spine 1986; 11(10).
Brad McKechnie, D.C., D.A.C.A.N.
Pasadena, Texas