Cervical Laminectomy with Lateral Mass Screw Fixation in Cervical Spondylotic Myelopathy: Neurological and Sagittal Alignment Outcome: Do We Need Lateral Mass Screws at each Segment?

Abstract

Background: Anterior cervical decompression and fusion is the standard procedure used for treating patients with cervical myelopathy. However, these procedures are associated with complications such as pseudarthrosis, construct failure, and neurological complications. Posterior cervical laminectomy and instrumentation is an alternative procedure to treat multilevel cervical myelopathy. In this study, we raised questions whether instrumentation is required at all levels and whether stabilizing the spine in neutral or lordotic contour with indirect decompression leads to neurological improvement with radiological evidence of anterior decompression. The results of posterior cervical laminectomy and instrumentation with lateral mass screw in terms of radiological and functional outcome in patients with multilevel cervical myelopathy are prospectively evaluated.

Materials and methods: In this prospective study conducted between June 2006 and December 2015, we have evaluated 112 patients with multilevel cervical myelopathy who underwent multilevel cervical laminectomy and instrumentation with lateral mass screw. All patients were evaluated preoperatively and postoperatively with Nurick's grading and Modified Japanese Orthopaedic Association (mJOA) scale for neurological function. Cooper scale and British Medical Research Council grading system for motor function. Curvature index was used to measure the alignment of cervical spine preoperatively and postoperatively. Alignment of the cervical spine was done preoperatively and postoperatively by calculating the curvature index. Axial MRI was used to calculate the severity of compression preoperatively which was calculated as per Singh's criteria and postoperatively to assess the adequacy of decompression at the operated level.

Results: In our study, there were 112 patients including 99 males and 13 females, with mean age of 59.53 years. The mean duration of followup of patients was 33.24 months. In total, cervical laminectomy was performed at 342 levels in 112 patients with an average of 3.05 laminectomies, and in total, 112 lateral mass screws were inserted. On postoperative followup, the mJOA and Nurick's grading showed improvement in all cases as compared to preoperative findings. The mean mJOA improved significantly from 8.56 preoperatively to 13.57 postoperatively (P < 0.001). The mean Nurick's grading also improved significantly from 2.59 preoperatively to 0.66 postoperatively (P < 0.001). The mean Cooper scale also showed significant improvement in both upper and lower limbs postoperatively (P < 0.001). The mean preoperative Cooper scale was 1.75 and postoperative was 0.31 for upper limbs, and the mean Cooper scale was 2.14 preoperatively and 0.56 postoperatively for lower limbs. X-rays done on routine followups showed good alignment of the cervical spine with maintenance of curvature index in all patients. The mean grade of compression as seen on preoperative MRI was 2.46 which reduced significantly postoperatively to 0.16 (P < 0.001).

Conclusion: The multilevel cervical laminectomy and instrumentation with lateral mass screw for multilevel cervical myelopathy is a safe technique that provides decompression of the spinal cord, prevents the development of kyphotic spinal deformity and posterior tension band of the spinal cord as associated with laminoplasty or uninstrumented laminectomy.

Keywords: Bone screws; Cervical laminectomy; cervical myelopathy; indirect decompression; laminectomy; lateral mass screw; myelopathy; spinal cord compression.

Figure 1

T2W MRI axial cut showing (a) Grade 0-360° cushion of cerebrospinal fluid around the spinal cord. (b) Grade 1 - loss of cerebrospinal fluid cushion without indention of spinal cord. (c) Grade 2 - mild spinal cord compression. (d) Grade 3 - severe spinal cord compression

Figure 2

(a) Immediate postoperative X-ray of cervical spine anteroposterior and lateral views following C3–C7 laminectomy and instrumentation done with lateral mass screw at C3, C5, and C7. (b) 2-year followup X-ray of the same patient showing well-maintained alignment of the cervical spine. Screws and rods are in good position

Figure 3

(a) Immediate postoperative X-ray of cervical spine anteroposterior and lateral views following C3–C6 laminectomy and instrumentation done with lateral mass screw at C3 and C6. (b) 3-year followup X-ray of the same patient showing well-maintained alignment of the cervical spine. Screws and rods are in good position

Figure 4

Sagittal MRI T2WI of cervical spine showing (a) multilevel spinal cord compression secondary to ossification of posterior longitudinal ligament. (b) Well decompressed spinal cord which has moved substantially away from anterior pathology. (c) Preoperative axial scan showing severe compression of the spinal cord. (d) Postoperative axial scan showing well-decompressed cord with 360° cushioning of cerebrospinal fluid

Figure 5

Sagittal MRI T2WI of cervical spine showing (a) multilevel spinal cord compression secondary to cervical spondylosis. (b) Well decompressed spinal cord which has moved substantially away from anterior pathology in postoperative image. (c) Preoperative axial scan showing severe compression of the spinal cord. (d) Postoperative axial scan showing well-decompressed cord with 360° cushioning of cerebrospinal fluid