Posterior Correction of Cervical Postlaminectomy Instability

Laminectomy is a procedure often performed in the posterior spine to decompress the spinal cord and nerve roots. The procedure is indicated for cervical stenosis with myelopathy and to gain access to the thecal sac for removal of spinal cord tumors. A single-level laminectomy typically does not destabilize the posterior aspect of the spine because most ligaments remain intact and only one level of bone is removed; however, when decompression requires multiple levels of laminectomy, it is more likely that the disruption of interspinous ligaments and the ligamentum flavum can result in a loss of stability from the removal of the posterior tension band. ¹^, ²^, ³^, ⁴ Taking too much bone laterally when performing the laminectomy or entering the facets or facet capsule can result in destabilization of the bony portion of the posterior spine. Destabilization of the soft or bony tissues of the posterior cervical spine can result in subluxation or progressive kyphotic angulation referred to as cervical postlaminectomy instability.

Cervical postlaminectomy instability is the most common postsurgical deformity resulting in kyphosis. ⁵ Its quoted incidence after laminectomy is 14 to 47%. ⁶^, ⁷ Predisposing factors include age at surgery (younger patients have a higher incidence), number of laminae removed, performance of a C2 laminectomy, disruption of the facets joints, preoperative curvature of the cervical column, and radiation therapy. ⁶^, ⁸^, ⁹ Children and young adults are predisposed to postlaminectomy kyphosis owing to ongoing spinal growth, laxity of spinal ligaments, and more horizontal orientation of the facet complex with poor resistance of incompletely ossified vertebral bodies to compressive loads ⁹^, ¹⁰^, ¹¹^, ¹² ( ▶ Fig. 15.1 a). Postlaminectomy kyphosis is not as common in adults because the anterior portion of the spine is often already fused from degenerative changes. With the exception of a study by Guigui et al, ⁸ the literature shows that patients who have more laminae removed are move likely to develop cervical instability ⁹ ( ▶ Fig. 15.2 a). Patients with a C2 laminectomy have more intervertebral mobility at cervical 2 to 3 after laminectomy than at other vertebral levels. ⁸ Disruption of the facet or facet capsule increases cervical spine instability, ⁸ as does demonstrated loss of cervical lordosis on preoperative imaging. Radiation therapy has been shown to result in instability and kyphosis. ⁹

Fig. 15.1 (a) Lateral x-ray of a 6-year-old patient with cervical kyphosis from cervical laminectomies (C3-C4) for resection of malignant peripheral nerve sheath tumor with adjuvant spinal radiation therapy. (b) The postoperative lateral X-ray with anterior cervical diskectomy and fusion (C2–5) and posterior spinal fusion (C2–6) for correction of cervical kyphosis and stabilization.

Fig. 15.2 (a) Lateral X-ray of a patient with chin on chest deformity from multilevel laminectomies (C3–T1) for cervical myelopathy. (b) The postoperative lateral X-ray showing multilevel fusion with anterior cervical diskectomy and fusion (C3–6) and posterior spinal fusion (C2–T4) for stabilization of chin on chest deformity.

15.2 Patient Selection

Posterior instrumentation and spinal fusion of the cervical spine are indicated for correction of cervical postlaminectomy instability in patients with worsening symptoms of cervical have worsening neck pain, neurologic deficits, difficulty swallowing, difficulty breathing, or chin-on-chest deformity may benefit from cervical posterior spinal fusion. Neurologic deficits include worsening symptoms of myelopathy, radiculopathy, quadriparesis, and quadriplegia. Occasionally patients who have low back pain after cervical laminectomy have developed lumbar hyperlordosis to compensate for cervical kyphosis. ⁹

Patients undergoing multilevel cervical laminectomy with risk factors that predispose to cervical instability should consider prophylactic posterior instrumentation and fusion ⁹ ( ▶ Fig. 15.2 b). For example, patients with preoperative radiographs that show significant listhesis with hypermobility in sagittal or horizontal planes may benefit from instrumentation and fusion ¹³; however, the risk factors of fusion must be carefully weighed and considered. Posterior fusion has the risks of failed fusion, hardware failure, and adjacent segment disease. ⁹ Hardware malposition can result in injury to nerve roots, adjacent facet joints, and the vertebral artery.

The choice of whether to add anterior stabilization must take into account the individual patient’s anatomy, the overall goal of surgery, neurologic compromise (or lack thereof), and the accessibility of the anterior cervical spine. ¹⁴ In patients with osteoporosis where construct failure is a concern, additional stabilization with anterior instrumentation should be considered. Patients with significant anterior cord compression may also need an anterior approach as a part of their procedure.

15.3 Preoperative Preparation

A detailed history and physical examination of the patient should be obtained along with preoperative labs and imaging. Preoperative laboratory tests include a basic metabolic profile, complete blood count, coagulation profile, and urinalysis. Preoperative X-ray imaging includes plain film radiographs of the cervical spine, including anterior-posterior, lateral, flexion, and extension views. CT and magnetic resonance imaging of the cervical spine should be reviewed before surgery. Prior cervical spine and operative reports should be requested for review by the surgeon.

Traction may be used for 5 to 7 days preoperatively to help reduce the kyphotic deformity and prepare for surgical correction. ⁹ Some patients may not tolerate traction, however. During traction reduction, patients are at risk of neurologic compromise and should be closely monitored. Comorbid medical complications can result from prolonged immobilization. ¹⁵

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