The aim of this study was to determine whether chilled irrigation
saline decreases the incidence of clinical upper limb palsy (ULP;
a reduction of one grade or more on manual muscle testing; MMT),
based on the idea that ULP results from thermal damage to the nerve
roots by heat generated by friction during bone drilling. Irrigation saline for drilling was used at room temperature (RT,
25.6°C) in open-door laminoplasty in 400 patients (RT group) and
chilled to a mean temperature of 12.1°C during operations for 400
patients (low-temperature (LT) group). We assessed deltoid, biceps,
and triceps brachii muscle strength by MMT. ULP occurring within
two days post-operatively was categorised as early-onset palsy.Aims
Methods
Using the transverse processes of fresh porcine lumbar spines as an experimental model we evaluated the heat generated by a rotating burr of a high-speed drill in cutting the bone. The temperature at the drilled site reached 174°C with a diamond burr and 77°C with a steel burr. With water irrigation at a flow rate of 540 ml/hr an effective reduction in the temperature was achieved whereas irrigation with water at 180 ml/hr was much less effective. There was a significant negative correlation between the thickness of the residual bone and the temperature measured at its undersurface adjacent to the drilling site (p <
0.001). Our data suggest that tissues neighbouring the drilled bone, especially nerve roots, can be damaged by the heat generated from the tip of a high-speed drill. Nerve-root palsy, one of the most common complications of cervical spinal surgery, may be caused by thermal damage to nerve roots arising in this manner.
