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Driver Reaction Time Following Selective Nerve Root Block

The authors of the study evaluated the effect of lumbar radiculopathy and selective nerve root block, SNRB, on driver reaction time, DRT. The driver reaction time is the measurement of ability to stop rapidly. This involves reaction time as well as strength in
the lower limb. Possible safe reaction time varies, depending on the country where studied.

In Britain, it is considered 700 milliseconds. In Germany, 1500 milliseconds. An on road study found that the DRT of normal drivers was 300 to 1200 milliseconds. The median was 660
milliseconds. Car simulators have been used to study DRTs for many orthopedic procedures.

The authors of the study used a custom built simulator.

The authors studied DRT in 20 subjects with radiculopathy, ten on the right side, and ten on the left side. They also evaluated the DRTs of 20 normal control subjects. The control subjects were matched for age and sex. The test subjects were tested prior to SNRB, immediately following SNRB, and at two and six weeks following SNRB. Subjects were included if they were regular drivers, over age seventeen, and had a valid driving license.

Subjects with coexisting neurological disorders, acute trauma, pathologic or infectious problems, and loss of full muscle strength were excluded from the study.

An electronic timer measured the reaction time. Force applied by the brake was also measured. When the brake was applied in response to a flashgun being triggered on the driving simulator, the timer would start. It would stop when a desired amount of force was applied to the brake. The authors also evaluated the effect of pain on DRTs using a visual analog pain scale from zero to ten.

The results of the study showed that all of the subjects with radiculopathy had slower DRTs than the normal control subjects prior to treatment. The average DRTs immediately after SNRB in both the left and right sided groups were slower than the control group. The average DRT of those treated with right SNRB remained slower than at the two week interval, but not at the six week interval after SNRB. The DRTs of the subjects with left-sided SNRB were not significantly slower at either the two or six week intervals. The authors also found that there was no correlation between leg pain on the VAS, and DRT.

The stopping distance increase in subjects undergoing SNRB on the right was 3.8 meters immediately after SNRB, and 1.9 meters at two weeks after SNRB at the speed of 100 kilometers per hour. The stopping distance was increased by 1.4 meters in the left-sided
radiculopathy subjects immediately following SNRB. It was not significantly increased at the two and six week intervals following SNRB.

Throughout the study, the average DRT of the radiculopathty groups was significantly longer than that of the normal group but still within the range of normal drivers in on road studies. Therefore, driving restrictions may or may not be appropriate following SNRB for lumbar radiculopathy.


A. Al-khayer et al. Driver reaction time before and after treatment for lumbar radiculopathy.SPINE July 2008. Volume 33, Number 15. Pp. 1696-1700.


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