Date Published: May 28, 2012
Publisher: Hindawi Publishing Corporation
Author(s): Brett A. Braly, David Lunardini, Chris Cornett, William F. Donaldson.
Cervical spondylotic myelopathy (CSM) is a degenerative process which may result in clinical signs and symptoms which require surgical intervention. Many treatment options have been proposed with various degrees of technical difficulty and technique sensitive benefits. We review laminoplasty as a motion-sparing posterior decompressive method. Current literature supports the use of laminoplasty for indicated decompression. We also decribe our surgical technique for an open-door, or “hinged”, laminoplasty.
Cervical spondylotic myelopathy (CSM) is the natural result of degenerative compression on the cervical spinal cord. The result may be a progressive and stepwise deterioration of neurological function in patients. The chronic debilitating nature of this process justifies surgical decompression. Posterior decompression has been described as a treatment for CSM since the 1940s. Laminectomy was the initial surgical option used. The decompression was performed by rongeurs. However, the insertion of the rongeur in an already limited space available for the cord led often to a decrease in neurological function postoperatively [1–3]. Even with modern approaches to laminectomy using high speed burs, development of postoperative instability has led surgeons to explore more efficacious ways of decompression.
Several factors must be considered in selecting the appropriate patient for laminoplasty. As mentioned, cervical laminoplasty is indicated for multilevel stenosis (AP canal diameter < 13 mm) due to spondylosis or OPLL (Figures 1, 2, and 3). The procedure is generally contraindicated in kyphotic cervical pathology as there is less room for posterior drift of the cord; however, up to 10 degrees of cervical kyphosis has been shown to have acceptable results [11, 12, 14]. Further contraindications include previous posterior cervical surgery, ossification of the ligamentum flavum (OLF), and epidural fibrosis. Preservation of the posterior elements allows for reinsertion of the nuchal muscles and spinal ligaments, allowing for better preservation of lordosis. Single- or two-level stenosis may best be treated from an anterior approach. Of the various techniques described for achieving decompression by means of laminoplasty, no one technique has been shown to have better results over others. The technique we employ is similar to the originally described expansive open-door of Hirabayashi and will be described here. As a posterior exposure of the cervical spine requires that patients lie prone, the anesthesia team must be experienced in managing access and endotracheal intubation in this position. Neurophysiologic monitoring should be considered for patients undergoing posterior cervical decompression. We use somatosensory-evoked potentials with care to determine baselines prior to prone positioning. Most patients receive arterial line monitoring, and we try to keep the patients mean arterial pressure at around 80–85 mm Hg to safely maintain cord perfusion. The patient is then prepped and draped in sterile fashion, the spinous processes are palpated to estimate levels, and a midline incision is made. Electrocautery is used to carry the incision deeply and expose the spinous processes, laminae and lateral masses of the desired levels, with care to preserve the facet capsules as well as the supraspinous and interspinous ligaments, as well as the interspinalis muscles. Localization can be confirmed by a lateral radiograph intraoperatively. Although it has limitations, the most comprehensive method of assessing the degree of impairment secondary to myelopathy is likely the Japanese Orthopaedic Association (JOA) score, with higher scores indicating better patient status and lower scores representing poorer patient status. Multiple studies reviewing laminoplasty have shown increases in the JOA by 55–65% [4–8]. Handa et al.  reported on 61 patients treated with the open-door technique which showed increase in recovery as well as JOA scores at one year. Their group was stratified by age (older versus younger than 70 years), and both groups showed improvement (62% and 59%, resp.). When cohorts are stratified by diagnosis, there is also a difference. Miyazaki and colleagues  reported more improvement when laminoplasty was performed for OPLL than for CSM (87% versus 76%, resp.). Interestingly, when laminoplasty was combined with a posterolateral fusion, the improvement scores for CSM surpassed those for OPLL, indicating that postoperative instability has some effect on outcomes. The postoperative complications for laminoplasty are similar to those of other posterior decompression techniques. Some have advocated that there is a larger incidence of wound complications and poor healing presumably due to the increased tension created by the mass effect of elevating the posterior structures . It is for this reason that we commonly debulk the more pronounced spinous processes prior to wound closure. Cervical spondylotic myelopathy is a progressive decline in the ability of the cervical spine to function properly. The natural history would suggest a continuous decline in neurological function which can ultimately become debilitating for patients. Current treatment theory suggests that a thorough decompression of the spinal canal can aid in preventing this decline. Source: http://doi.org/10.1155/2012/508534