Cervical Laminoplasty

Cervical laminoplasty is an alternative surgical intervention to traditional cervical laminectomy and fusion, and multilevel corpectomy for cervical spondylotic myelopathy. Laminoplasty involves decortication of the lamina on one side creating an opening trough, and formation of a unicortical hinge on the contralateral side thereby effectively sparing resection of the posterior spinal elements while providing canal expansion. [1, 2]

Indications

Multilevel cervical stenosis with myelopathy.
Congenital stenosis with superimposed spondylosis
Ossification of the posterior longitudinal ligament (OPLL)
Multilevel disk herniations
Tumors
Adjacent segment stenosis after previous anterior cervical fusion

Contraindications

Fixed cervical kyphosis
Epidural scarring or adhesions
Significant preoperative neck pain
Severe spinal cord compression with significant ventral pathology

Preoperative Planning

Pre-operative planning involves the evaluation of the number of levels to be expanded as well as whether foraminotomies are indicated for radicular symptomology. Segmental instability may necessitate an additional focused/limited posterior fusion.[3] Flexion/ extension films should be obtained for evidence of instability and for evaluation of a correctable kyphosis.

CT scans, MRI and AP/Lateral views of the cervical spine are used to correlate clinical findings and help to localize surgical levels. MRI scan better assess soft tissue evaluation. CT myelography may be utilized to assess the extent of bony ossification particularly in cases of severe OPLL. [4].

Positioning

Fiberoptic intubation is performed. Neuromonitoring electrodes in the form of somatosensory-evoked potentials and motor evoked potentials are placed and baseline recordings are performed.

Three pronged Mayfield tongs are used to immobilize the spine and prevent excessive pressure on the eyes and face (Figure 1).

Figure 1: Three Mayfield tongs are utilized.

The patient is positioned on a regular operating table with chest pads and with the knees flexed 60°to 90°

and the bed in a reverse Trendelenburg (head up) position in order to decrease the venous pressure and bleeding (Figure 2).

Figure 2: Patient positioning with the bed in the reverse Trendelenburg position.

The operative alignment of the spine should be in a neutral to slightly flexed position to aid in exposure, and allow for “unshingling” of the cervical lamina[4].

The shoulders and arms are taped down to ensure adequate intra-operative imaging [5].

Approach

Surgical Anatomy

The nuchal ligament forms a septum between the left and right trapezius muscles and is attached to the external occipital protuberance on the rostral side. The ligament becomes the supraspinous ligament at the 6^th or 7^th spinous process on the caudal side[6].

A superficial muscular layer in the posterior cervical approach is comprised of the trapezius and splenius capitis muscles. The trapezius muscle attaches on either side of the nuchal ligament. Immediately underneath the trapezius muscle the splenius capitis muscle insertion into the spinous processes are visualized.

Deep to the insertion of the splenius capitis, another muscular layer is encountered and is comprised of the interspinalis and semispinalis cervicis muscles. The semispinalis insertion is at the C2 spinous process and can be palpated as the occipital protuberance. Additional muscular attachments at the C2 spinous process include the rectus capitis posterior major and the inferior capitis oblique muscles[6].

No major nerves are encountered in the posterior cervical approach. The dorsal root ganglion of the C2 posterior branch of the greater occipital nerve is at the lateral margin of the dura mater, penetrates the semispinalis capitis and runs cranially. The deeper layer of the nuchal musculature is innervated by posterior branch of the spinal nerve root.

No major arterial supply is encountered in laminoplasty. An epidural venous plexus is present underneath the lamina. Avoidance of this plexus can decrease operative blood loss.

Exposure

A midline incision is made over the levels to be decompressed. Most commonly this occurs from the C3-C7 levels. More recently it has been demonstrated that preservation of the C7 lamina may decrease post-operative axial discomfort [7, 8]. In these cases the incision is extended from the occipital protuberance (inferior edge of the C2 lamina) to the superior portion of the C7 spinous process using lateral fluoroscopy. To maintain cervical lordosis, the nuchal attachments of C2 must be preserved. Electrocautery is used to subperiosteally dissect the muscular attachments laterally from the spinous processes, laminae and medial aspect of the facets. On the designated open side, the dissection should be to the extent of the medial aspect of the lateral masses but not facet joint complex unless fusion is being attempted. On the hinge side the dissection is taken as far the lamina-facet junction.

Technique

The Open door and French door techniques are both ways in which decompression can be accomplished. In the open door technique the lamina is detached unilaterally from the facet and the contralateral side is scored uni-cortically for use as the hinge. The French door (or double-door cervical laminoplasty) technique uses a midline division of the posterior spinal elements and widens the spinal canal through bilateral hinges on the lamina-facet complexes with use of one of a variety of materials to keep the posterior elements in an open position. The following section describes the Open door technique for laminoplasty from levels C3-C7.

Step 1: The interspinous ligaments are excised at the interspaces superior and inferior to the levels of the laminoplasty.

Step 2: A bone cutter is used to remove the spinous processes from C3-C6. Care is taken to undercut C7 but to preserve the muscular and ligamentous attachments. Bone wax or a hemostatic sealant is applied to control bone bleeding.

Step 3: The junction between the lamina and facet is identified. At this junction, a high speed burr is used to create an opening of approximately 3 mm. This requires approximately 15% resection of the facet joint [9].

Step 4: The open side should be burred down to thin the lamina to the ligamentum flavum while avoiding contact with the dura. A curved microcurette can be used to palpate the defect to ensure that the trough is through the bone.

Step 5: Attention is now turned to the hinge side where a high speed burr is used to remove the dorsal cortex and thin the ventral cortex. This trough should be unicortical.

Step 6: On the open side, opening is performed by placing curved curettes underneath the lamina and gently manipulating it to the contralateral side. Excessive force should be avoided to prevent any breaks along the hinge side.

Step 7: Once all lamina are expanded with the curettes, trial spacers are used to determine proper allograft size of 10-12 mm or plate in the lamina-facet space at the C3, C5 and C7. The ligamentum flavum is resected from C3-C7.

Step 8: A double pre-bent miniplate of appropriate length can be fixed to the allograft via a center screw hole. The notched ends of the grafts should be fit securely into the cut ends of the lamina and the lateral mass.

Step 9: The mini plate is centered in the middle of the lamina and lateral mass for placement.

Step 10: A built- in stop drill bit is used to prepare the insertion sites for the screws.

Step 11: Proper screw sizes are obtained and direction of purchase are necessary to avoid violation of the facet joints and spinal canal (Figure 3).

Figure 3: Purchase of the screw should avoid violation of facet joints and spinal canal.

Step 12: Two 2.0 mm cortex screws are first placed through the plate over the lateral mass.

Step 13: One or two 2.0 mm cortex screws are placed through the plate into the lamina. This step is optional and it is the senior author’s preference not to instrument the laminar side.

Step 14: This screw and plate procedure is repeated at the other operative spinal levels. Levels are alternated as there is no need for fixation at every level particularly if the ligamentum flavum and interspinous ligaments are preserved (Figure 4).

Figure 4: The screw and plate procedure at the C5 level.

Step 15: Intra-operative fluoroscopy is used to determine proper placement of hardware.

Step 16: Once proper hardware placement is confirmed, the wound is copiously irrigated. The subcutaneous tissue and skin are closed in a typical manner.

Pearls and Pitfalls

Pitfalls[10]:

1. Segmental motor paralysis particularly at the C5 level has been noted to occur. Risks of this neuropraxia should be pre-operatively discussed with the patient. Prophylactic foraminotomies may be performed however the scientific evidence is limited.

2. Detachment of the hinge side can occur if excessive drilling occurs. Fracture of the hinge side can occur due to excessive force of the curve curette when opening the contralateral open side.

3. Cerebrospinal fluid leakage due to a dural tear on the opening side may occur with overly aggressive burring.

4. If the cuts are too far lateral then the facet joint complex may be de-stabilized.

Pearls:

1. Slight flexion of cervical spine facilitates both exposure and closure by eliminating posterior skin folds and decreases shingling of the lamina for improved identification of adjacent levels.

2. The superior aspect of the lamina is usually the thickest area and is the area most often not thinned enough. Therefore the surgeon must make sure to recheck the opening side if difficulty is encountered elevating the hinge side[10].

3. Burring too deep into the troughs can lead to inadvertent durotomies. Thus extreme care and attention must be paid when the holes are burred[11].

Postoperative Care

The patient is placed in a soft cervical collar for comfort. It is the senior author’s preference to wear the collar for only 23 hours. Gentle range of motion exercises are encouraged in the immediate post operative period on post-operative day one. At this time physical therapy in the form of bed transfers and ambulation should occur[12]. Patients are typically discharged 24- 48 after surgery. X-rays should be obtained at 4 weeks postoperatively to demonstrate adequate fixation. Active resistive exercises are begun at the 4 week post-operative time period.

Outcome

Studies have found significant improvement in pain and functional outcome scores 5 to 10 years after the laminoplasty procedure [13, 14].
Multiple studies have shown that patients with cervical myelopathy due to cervical spondylosis or OPLL benefit from laminoplasty. Mean recovery rates using the Japanese Orthopedic Association (JOA) scoring system have ranged from 50-90%.[2, 5]
Age greater than 60 and a history of symptoms pre-operatively for more than one year, and a history of ossified posterior longitudinal ligament are slightly worse prognostic indicators [15, 16].
Kaminsky et al. compared laminoplasty versus laminectomy without fusion for cervical spondylotic myelopathy and found that laminoplasty treated patients had less postoperative cervical pain and less than cervical range of motion.[17]
Edwards et al. compared laminoplasty to ACDF in matched cohort of 13 patients in each group and found higher rates of neurologic improvements, less pain medication needs, and fewer complications in the laminoplasty cohort [18]. Yonenobu et al. support these conclusions and agree that in comparison of subtotal corpectomy with strut grafting, laminoplasty offers advantages of less bone grafting complications, and better post-operative mobilization[19].

Complications

Segmental nerve root palsy ranges from 1-3% and most commonly affects the C5 nerve root. It may present at any period after the surgery, from minutes up to 20 days postoperatively. Recovery or improvement occurs over weeks to months in a majority of patients [20, 21].
Postoperative new onset neck pain has been reported in several studies. One study suggests that this can be reduced with early postoperative motion and active rehabilitation of the cervical extensor muscles, and preservation of the C7 spinous process (Need reference) [22-24].
Loss of motion may occur most likely due to facet joint injury, and spontaneous fusion or alterations in tissue elasticity following posterior exposure[4]. One study suggests that not using bone graft along the hinged side as well as earlier post-operative mobilization may decrease this loss of motion[25].

References

1. Chiba, K.M.D.P., et al., Long-term Results of Expansive Open-Door Laminoplasty for Cervical Myelopathy-Average 14-Year Follow-up Study. Spine (Phila Pa 1976), 2006. 31(26): p. 2998-3005.

2. Cunningham, M.R.A.M.D., S.M.D. Hershman, and J.M.D. Bendo, Systematic Review of Cohort Studies Comparing Surgical Treatments for Cervical Spondylotic Myelopathy. Spine (Phila Pa 1976), 2010. 35(5): p. 537-543.

3. Rhee, J.M. and S. Basra, Posterior surgery for cervical myelopathy: laminectomy, laminectomy with fusion, and laminoplasty. Asian Spine J, 2008. 2(2): p. 114-26.

4. John M, R., Posterior Surgery for Cervical Myelopathy: Laminectomy, Laminectomy with Fusion, and Laminoplasty. Seminars in Spine Surgery, 2007. 19(1): p. 35-43.

5. Sayana MK , H.J., Poynton A, Cervical Laminoplasty for Multilevel Cervical Myelopathy. Advances in Orthopedics, 2011. 2011: p. 1-4.

6. Nakamura, K.o.o., Y. Toyama, and Y. Hoshino, Cervical laminoplasty. 2003, Tokyo ; New York: Springer. xii, 193 p.

7. Takeuchi, T. and Y. Shono, Importance of preserving the C7 spinous process and attached nuchal ligament in French-door laminoplasty to reduce postoperative axial symptoms. European Spine Journal, 2007. 16(9): p. 1417-1422.

8. Zhang, P., et al., Preserving the C7 spinous process in laminectomy combined with lateral mass screw to prevent axial symptom. Journal of Orthopaedic Science, 2011. 16(5): p. 492-497.

9. Singh, K. and A.R. Vaccaro, Pocket atlas of spine surgery. 2012, New York: Thieme.

10. Vaccaro, A.R. and T.J. Albert, Spine surgery : tricks of the trade. 2nd ed. 2009, New York: Thieme. xxi, 321 p.

11. Wang, J.C., American Academy of Orthopaedic Surgeons., and North American Spine Society., Advanced reconstruction : spine. 2011, Rosemont, IL: American Academy of Orthopaedic Surgeons. xxiii, 688 p.

12. Vaccaro, A.R. and E.M. Baron, Spine surgery. Operative techniques. 2008, Philadelphia, PA: Saunders / Elsevier. xviii, 481 p.

13. Seichi, A., et al., Long-term results of double-door laminoplasty for cervical stenotic myelopathy. Spine (Phila Pa 1976), 2001. 26(5): p. 479-87.

14. Kawaguchi, Y., et al., Minimum 10-year followup after en bloc cervical laminoplasty. Clin Orthop Relat Res, 2003(411): p. 129-39.

15. Lee, T.T., G.R. Manzano, and B.A. Green, Modified open-door cervical expansive laminoplasty for spondylotic myelopathy: operative technique, outcome, and predictors for gait improvement. J Neurosurg Spine, 1997. 86(1): p. 64-68.

16. Iwasaki, M., et al., Long-term results of expansive laminoplasty for ossification of the posterior longitudinal ligament of the cervical spine: more than 10 years follow up. Journal of Neurosurgery: Spine, 2002. 96(2): p. 180-189.

17. Kaminsky, S.B., C.R. Clark, and V.C. Traynelis, Operative treatment of cervical spondylotic myelopathy and radiculopathy. A comparison of laminectomy and laminoplasty at five year average follow-up. Iowa Orthop J, 2004. 24: p. 95-105.

18. Edwards, C.C., 2nd, J.G. Heller, and H. Murakami, Corpectomy versus laminoplasty for multilevel cervical myelopathy: an independent matched-cohort analysis. Spine (Phila Pa 1976), 2002. 27(11): p. 1168-75.

19. Yonenobu, K., et al., Laminoplasty versus subtotal corpectomy. A comparative study of results in multisegmental cervical spondylotic myelopathy. Spine (Phila Pa 1976), 1992. 17(11): p. 1281-4.

20. Uematsu, Y., Y. Tokuhashi, and H. Matsuzaki, Radiculopathy After Laminoplasty of the Cervical Spine. Spine (Phila Pa 1976), 1998. 23(19): p. 2057-2062.

21. Satomi, K., et al., Long-Term Follow-up Studies of Open-Door Expansive Laminoplasty for Cervical Stenotic Myelopathy. Spine (Phila Pa 1976), 1994. 19(5): p. 507-510.

22. Hosono, N., K. Yonenobu, and K. Ono, Neck and Shoulder Pain After Laminoplasty: A Noticeable Complication. Spine (Phila Pa 1976), 1996. 21(17): p. 1969-1973.

23. Kawaguchi, Y., et al., Axial symptoms after en bloc cervical laminoplasty. J Spinal Disord, 1999. 12(5): p. 392-5.

24. Kawaguchi, Y., et al., Preventive Measures for Axial Symptoms Following Cervical Laminoplasty. J Spinal Disord Tech, 2003. 16(6): p. 497-501.

25. Wada, E., et al., Subtotal corpectomy versus laminoplasty for multilevel cervical spondylotic myelopathy: a long-term follow-up study over 10 years. Spine (Phila Pa 1976), 2001. 26(13): p. 1443-7; discussion 1448.