General:
- Performing extensive multilevel laminectomies does not immediately destabilize an otherwise intact spine but can result in progressive deformity
- incidence of postoperative kyphosis after multilevel cervical spine laminectomy is 20%
Causes of post laminectomy cervical deformity
- Iatrogenic injury
- Denervation and atrophy of the posterior cervical muscles
- Loss of posterior tension band → increases weight through the anterior vertebral body → worsening sagittal deformity → worsening kyphosis → draping and tenting of cord over vertebral body → flattening of small feeding vessels to the cord → worsening myelopathy and pain
- Denervation and disruption of facet joints
- Natural anatomy of the C spine:
- Anterior VB supports only 36% of cervical load
- Posterior column supports 64% of cervical load
- Paeds
- The incidence of postlaminectomy kyphotic spinal deformity is higher.
- Because the incompletely ossified VBs in children
- offer poor resistance to compressive forces
- are more prone to developing wedge deformity and progressive loss of sagittal balance
Factors have been associated with a higher incidence of postoperative kyphosis:
- preoperative loss of cervical lordosis
- Increases risk of post op kyphosis by 2x
- Normal cervical spine has a mean lordotic curve of 14 to 20°
- Any kyphosis in the C spine is abnormal
- Check with
- Standing AP and Lat Xray
- MRI
- CT
- Facet capsule destruction and extent of laminectomy
- Tumor
- Irradiation
- Radiation causes bone death and impaired bone growth resulting in delayed deformity in growing children.
- Doses > 3000 rads have been linked to higher rates of scoliosis
- Radiotherapy for neuroblastoma in whom survival was greater than 5 years;
- 76% incidence of spinal deformity after a 13-year follow up.
- 20% of the survivors required deformity correction surgery
- Post op neurological deficits
Clinical and radiological features of deformity
- Back or neck pain
- Most common
- Due to
- Muscle fatigue
- Can improve with physical therapy and or brace
- Facet joint arthropathy
- Radiculopathy due to foraminal compression
- Neurological deficit
- Due to myelopathy
- Late findings
- Lhermite sign
Preventing post op kyphotic deformity
- posterior segmental instrumentation and fusion performed at the time of the initial surgery.
- Cons
- Adds considerable time and morbidity to the operation
- Result in a substantial decrease in mobility
- Can cause sagittal imbalance in growing child
- Accelerated degeneration of adjacent level disease
- Performing laminoplasty or osteoplastic laminotomy
- Decreases but does not remove the risk of kyphotic deformity
Treatment
- Conservative treatment
- Chosen initially
- Frequent radiographic follow-up evaluation and exercises are necessary
- The role of brace therapy remains controversial
- Surgical fixation
- Indication
- progressive neurological decline,
- functional loss
- intractable pain
- Options
- If the deformity can be reduced, it can be corrected by careful positioning on the operating room table or in traction OR
- Can be augmented with: Cranial traction for up to 5 days
- Anterior fixation and fusion
- Whenever possible, we prefer to preserve the VBs and perform multiple discectomies and disc interspace distraction to restore the normal cervical lordosis.
- in cases involving multilevel fusion and in patients who smoke, the placement of an anterior autograft is preferable.
- Anterior plating stabilizes the spine and increases fusion rates, especially in multilevel constructs
- In early reports involving anterior correction without ACPs, the anterior construct failed in up to half of all cases.
- Graft to use
- Vertebrectomy is necessary, an anterior fibula strut graft or an autograft-filled cage can be used
- excellent fusion rates using a polyetheretherketone interbody spacer in conjunction with recombinant human bone morphogenetic protein.
- Avoids the morbidities associated with harvesting of iliac crest bone and achieves very high fusion rates even in cases with multiple levels
- Post op
- collar for 12 weeks after surgery in all cases of deformity surgery
- Via: segmental lateral mass instrumentation with a polyaxial screw and rod system.
- Screw purchase on the lateral mass is limited to 16 mm or less, but for longer constructs such as in the upper thoracic pedicles, C-7, C-2, and C-1 lateral mass pedicle screws can be used
- The amount of force that can be applied for deformity reduction is restricted by the limited screw purchase
- Osteotomies
- Posterior osteotomies facilitate kyphotic deformity reduction.
- Smith-Petersen osteotomy
- A limited degree of correction can be achieved
- Posterior elements are excised
- Pedicle subtraction osteotomies
- can achieve a greater reduction
- Cons
- high risk of neurological deterioration including
- Quadriparesis
- C-8 nerve root injury
- Use has been generally limited to extremely severe cases in which an anterior approach is not possible.
- Evidence
- McMaster
- osteotomies at C7– T1 n=15 patients
- mean correction was 54°;
- new neurological deficits developed in 20% of the patients.
- Ant + post
- Indication
- in cases in which the anterior procedure involves more than a two-level corpectomy
- Very unstable spine
- allows for deformity correction and the posterior approach supplements the construct stability.
- For Fixed deformity
- Herman and Sonntag et al: Postlaminectomy kyphosis (mean angle was 38°)
- Using an anterior approach.
- Traction improved the kyphotic angle by a mean of 8°
- Open reduction via only an anterior approach and a vertebrectomy resulted in a mean improvement of 28°.
- Steinmetz et al
- Using an anterior approach.
- Their mean kyphotic deformity was 13°. The mean correction was 20° and the mean postoperative lordotic angle was 6°;
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