AAOS Comprehensive Orthopaedic Review 4: Print + Ebook (AAOS - American Academy of Orthopaedic Surgeons)

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Section 2 | Spine

b. Less commonly, conditions involving the pos terior structures, such as ligamentum flavum hypertrophy or, rarely, ossification of the liga mentum flavum, may contribute. c. Degenerative spondylolisthesis also can exac erbate or cause compression. d. CSM commonly arises in the setting of a con genitally narrowed cervical canal. CSM often does not become symptomatic until the later decades of life because the cord may have sufficient space to avoid compression until a threshold amount of space-occupying degen erative changes accumulate. 2. Less commonly, other causes of cervical cord compression (eg, epidural abscess, tumor, trauma) can result in cervical myelopathy. These cases usually present somewhat differently, with pain, constitutional symptoms, or a history of injury in addition to myelopathic symptoms. 3. Kyphosis (primary or postlaminectomy) is another less common cause. 4. A broad differential diagnosis should be consid ered, including nonspinal disorders such as stroke, movement disorders, and multiple sclerosis. D. Imaging evaluation 1. Either MRI or CT myelography is necessary to confirm spinal cord compression. 2. MRI a. MRI is noninvasive and provides adequate imaging characteristics in most patients. b. Signal changes within the cord may be demon strated on MRI, suggesting severe compression. c. The compression ratio (the ratio of the small est sagittal cord diameter to the largest trans verse cord diameter at the same level) can be calculated from measurements on MRI. • A compression ratio of less than 0.4 is asso ciated with a poor prognosis. • Conversely, an increase in the compression ratio to more than 0.4 postoperatively cor relates with clinical recovery. 3. CT myelography a. CT myelography should be considered if MRI cannot be obtained for medical reasons (eg, cardiac pacemakers, aneurysm clips, or severe claustrophobia) or if metal or scarring from prior cervical surgery precludes adequate visu alization on MRI because of artifact. b. CT with or without myelography can help diagnose the presence of OPLL, which may

not be obvious on MRI or plain radiography but can have a profound effect on the surgical approach. E. Treatment 1. Surgery is the treatment of choice. Although some studies indicate that mild cases of CSM can be observed, CSM is typically progressive and is considered a disorder for which surgical treat ment is indicated. 2. Surgical management has been shown to improve functional outcomes, pain, and neurologic status. 3. Early intervention, before permanent changes occur in the spinal cord, improves the prognosis. 4. If nonsurgical care is elected, careful and frequent follow-up is mandatory. Firm orthoses, anti-­ inflammatory medications, isometric exercises, and epidural steroids can be considered. 5. Observation, not surgery, is recommended for patients with only radiographic cord compression from spondylosis without clinical myelopathy or radiculopathy. A recent systematic review esti mated that myelopathy develops in these patients at a rate of 22% at mean follow-up of 44 months. However, patients without myelopathy with cord compression and radiculopathy have a much higher risk of developing myelopathy. Such patients can be counseled to either have prophylactic surgery or closely monitor their symptoms. F. Surgical treatment—overview of options 1. Considerable debate exists regarding the opti mal surgical approach for CSM. Options include laminectomy with or without fusion, ACDF, and laminoplasty. 2. No single procedure is clearly favorable in all circumstances, but the following considerations

2 | Spine

may favor one approach over another: a. Number of stenotic levels present b. Patient factors, such as comorbidities c. Desire to either limit or preserve motion

G. Laminectomy without fusion 1. Effective in stable spines, as long as the facets are mostly preserved. 2. Postlaminectomy kyphosis can occur, with esti mates ranging from 11% to 47%. Although this complication can result in potential recur rent myelopathy if the cord becomes draped and compressed over the kyphosis, the incidence of clinically apparent neurologic problems resulting from this complication is unclear. Copyright © Wolters Kluwer, Inc. Unauthorized reproduction of the content is prohibited. 2023

AAOS Comprehensive Orthopaedic Review 4

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