Writing in the Journal of Neurosurgery: Spine, Shota Takenaka (Department of Orthopaedic Surgery, Osaka Kosei-nenkin Hospital, Fukushima, Japan) and others report that the use of cooled saline during bone drilling for cervical laminoplasty may reduce the incidence of upper-limb palsy.
Takenaka et al commented that even though cervical laminoplasty for cervical compressive myelopathy is associated with “excellent long-term results”, postoperative upper-limb palsy “persists as a complication” of this procedure. They added: “Possible causes of this complication have been suggested, although none have been able to fully account for the occurrence of upper-limb palsy after cervical laminoplasty.”
The authors proposed—in the Journal of Neurosurgery: Spine article—that friction-generated heat from the high-speed drill used for bone cutting during cervical laminoplasty “results in thermal damage, which causes the upper-limb palsy”.
“We therefore hypothesised that the use of cooled irrigation saline during bone drilling could prevent postoperative upper-limb palsy by minimising the generation of frictional heat,” Takenaka et al noted.
In the retrospective study, 159 patients underwent cervical laminoplasty receiving irrigation saline at two different temperatures: between December 2008 and May 2010, 79 patients received irrigation saline at room temperature (average 25.6°C); and 80 received cooled irrigation saline (average 12.1°C) between June 2010 and October 2011.
Takenaka et al reported that, according to a univariate analysis, a decrease in arm muscle strength (postoperation) was observed significantly more frequently in patients who had received room temperature saline than in those who had received cooled saline. They added: “The decrease in strength in the room temperature and low temperature groups was 7.6% and 1.9% in the deltoid muscle, 10.1% and 4.4% in the biceps brachii muscle, 1.3% and 0.6% in the triceps brachii muscle, and 7.6% and 3.1% in grip, respectively.” Furthermore, in a multivariate logistic regression analysis, room temperature saline (alongside female sex and an open-gutter side) was found to be a significant predictor for decreased deltoid muscle strength (p=0.054) and a potential predictor (not significant) for decreased biceps brachii muscle strength.
According to the authors, muscle strength decreased more frequently in the left arm than in the right arm. They explained: “In this study, the left side of the lamina was always opened irrespective of the laterality of cord compression. The nerve roots exposed on the open side are more susceptible to thermal damage than those on the hinge side where residual laminae can offer some measure of protection. Therefore, these results support the thermal damage theory.”
Concluding, Takenaka et al stated that other measures to prevent upper-limb palsy (such as high-dose methylprednisolone) are limited by their potential side-effects. They said: “We propose here the use of cooled irrigation saline during bone drilling because it is very easy to perform, does not require any kind of special apparatus, and poses no additional risk to patients.”