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Cervical laminoplasty
The Spine Journal 6 (2006) 274S–281S
Cervical laminoplasty Michael P. Steinmetz, MD, Daniel K. Resnick, MD* Department of Neurosurgery, University of Wisconsin School of Medicine, K4/834 Clinical Science Center, 600 Highland Ave., Madison, WI 53792, USA
Abstract
Laminoplasty was developed to treat multilevel pathology of the cervical spine, namely ossification of the posterior longitudinal ligament and cervical spondylotic myelopathy. Laminoplasty was popularized in the 1980s, and since then many variations on the theme have been developed. All are similar in that they expand the cervical canal while leaving the protective dorsal elements in place. Advocates claim that this prevents the formation of the ‘‘postlaminectomy’’ membrane, maintains spinal alignment, and should aid in maintaining cervical range of motion. The aforementioned are all potential shortcomings of laminectomy or laminectomy and fusion. The procedure has proven to be essentially equal to other cervical decompressive procedures in the neutral or lordotic spine, and outcome has been shown to be durable. Ó 2006 Elsevier Inc. All rights reserved.
Keywords:
Laminoplasty; Cervical spine; Laminectomy; Ossification of the posterior longitudinal ligament; Cervical spondylotic myelopathy; Myelopathy; Cervical stenosis
Introduction Cervical laminectomy has long been the treatment for multilevel cervical spondylosis. It permits adequate decompression of the cervical spinal cord and is safe and easily performed. Potential adverse outcomes after cervical laminectomy include instability and epidural scar formation. It has been hypothesized that this scar may be responsible for persistent postoperative cervical and head pain after surgery and even neurologic deterioration. Fear of instability has resulted in many surgeons performing a simultaneous fusion operation at the time of laminectomy. This potentially adds morbidity to the procedure, there may be nonunion or construct failure, and it reduces motion in the cervical spine. Laminoplasty was developed to widen the spinal canal dimensions without permanently removing the dorsal elements of the cervical spine. The retained dorsal elements should aid in the prevention of muscle scarring to the dura (ie, result in less cervical and head pain after surgery) and FDA device/drug status: approved but not for this indication (miniplates). Author DKR acknowledges a financial relationship (consultant with Medtronic) that may indirectly relate to the subject of this research. * Corresponding author. Dept. of Neurological Surgery, University of Wisconsin School of Medicine, K4/834 Clinical Science Center, 600 Highland Ave., Madison, WI 53792. Tel.: (608) 263-9651; fax: (608) 263-1728. E-mail address: [email protected] (D.K. Resnick) 1529-9430/06/$ – see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2006.04.023
potentially reduce the incidence of postoperative instability. Cervical motion is theoretically preserved. In 1973, Oyama et al. introduced a Z-plasty of the cervical spine [1]. This procedure allowed decompression, while the retained laminae provided support and prevented invasion of the postlaminectomy membrane. Hirabayashi et al. reported on the open-door laminoplasty in 1981 [2]. Following this publication, various modifications have been developed that are purported to improve the safety and effectiveness of the procedure.
Goals of laminoplasty The main goal of laminoplasty is to provide decompression of the spinal cord by widening the spinal canal while preventing instability after decompression (ie, development of kyphosis) and scar in-growth with potential neurological deterioration after surgery. The development of postsurgical cervical kyphosis is well described [3–5], especially in children [6]. The risk has been shown to be reduced with lateral mass fixation [7], and theoretically with laminoplasty, although some loss of lordosis is often seen. The maximum region of canal expansion is on the open side in hinge-type procedures and in the midline in bilateral hinge operations. Migration of the cord away from the ventral vertebral bodies has been documented in both varieties
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of laminoplasties [8,9]. This has been confirmed with postoperative computed tomographic myelography. Although the performance of a laminoplasty procedure allows for a decompression without a fusion, there still does appear to be some loss of motion associated with the procedure. Many studies have reported a loss in cervical range of motion (ROM) after laminoplasty. The degree of loss of ROM ranges from 17% to 50% in published series, with most authors reporting an approximate 50% loss of global ROM [2,10–25]. The loss of ROM is in flexion, extension, rotation, and lateral bending. It is of note that some authors have not reported any change of ROM after laminoplasty [26]. The loss of ROM after laminoplasty should be taken in context, however, as fusion results in a much more substantial loss of motion [27,28]. Some authors believe that the increased stiffness seen after laminoplasty decreases the potential for injury to the cord via dynamic movements [29] and aids in the resolution of ossification of the posterior longitudinal ligament (OPLL) [25]. In contrast, some authors believe that maintaining ROM is crucial. For example, Shaffrey et al. emphasized the maintenance of cervical ROM via laminoplasty as a means to avoid adjacent-segment disease [30].
Limitations and contraindications Indications for laminoplasty include multilevel cervical spondylosis and OPLL. It may also be used for certain varieties of spinal cord tumors. The procedure is generally contraindicated in kyphotic cervical pathology. It is possible to perform laminoplasty in a straightened spine, but a lordotic posture is preferred. As noted above, most studies document loss of cervical lordosis after surgery. Laminoplasty is generally not indicated for one- or two-level disease. The limited length of decompression in such cases generally does not allow the free migration of the spinal cord away from the ventral elements.
Fig. 1. In the Z-Plasty, troughs are first drilled into the lamina at the junction of the lateral mass. The laminae are then thinned. After this, a ‘‘Z’’ is cut in the laminae with a high-speed drill. Note the dotted line of the proposed cut.
Z-Plasty This technique was originally described by Oyama et al. [1]. In this procedure, the spinous processes are first removed and the laminae thinned. They are thinned out to the laminae–facet junction. Troughs are performed laterally. At this point a ‘‘Z’’ is cut into the thinned laminae (Fig. 1). This may be performed with a high-speed drill and diamond drill bit or a fine Kerrison punch. After the ‘‘Z’’ cut, the thinned sections of laminae may then be separated and the canal opened or expanded. The laminae may then be secured with suture or wire to maintain the expanded canal (Fig. 2).
Laminoplasty techniques Many techniques that are variations of laminoplasty have been described. They are all similar in that they expand the cervical canal and preserve some or all of the posterior elements. Modifications on where the cuts in the lamina or spinous processes are made and how the canal is kept open have been developed. Newer techniques, such as the use of ceramic spacers and titanium miniplates have been proposed, which may decrease the surgical time and improve the safety of the procedure. No one procedure has proven to be more effective than any other in terms of neurological outcome, cervical alignment, or ROM.
Hirabayashi laminoplasty Hirabayashi and colleagues described the expansive open-door laminoplasty [2]. In this technique, the spinous processes and laminae are exposed from C2–C7. The supraspinous and interspinous ligaments are preserved and not injured. In the authors’ experience, the ligaments must be cut between C2 and C3 and C7 and T1, depending on which levels are to be expanded. This aids in ‘‘opening the door’’. Using a high-speed drill, a trough is created on the ‘‘open’’ side at the junction between the laminae and the facets (Fig. 3). The trough is drilled down to the
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Fig. 4. After drilling the complete trough on the open-door side, a second trough is drilled on the closed side. Care must be taken not to drill all the way through the lamina. This will lead to fracture of the hinge and an ineffective open-door laminoplasty.
Fig. 2. After the cuts, the laminae are spread apart and held with wires or suture, effectively widening the canal.
ligamentum flavum. One may drill all the way through the laminae or one may leave a very thin remnant of laminae, especially at its cranial aspect. This thin rim and associated ligament are then removed with a 1-mm or 2-mm Kerrison punch. A second trough is then drilled in the opposite or ‘‘closed’’ side with a high-speed drill (Fig. 4). Care is taken to only thin the lamina on this side and not cut all the way through. This trough is cut somewhat more lateral as compared with the ‘‘open’’ side. The opening on the open side is then gently expanded, thus lifting the lamina off the spinal cord and expanding the canal. The surgeon may gently
Fig. 3. In the Hirabayashi-type open-door laminoplasty, a trough is first drilled in the laminae. This is done somewhat more medial then the lamina, lateral mass junction. The cut is taken down to dura. The ligament and any remaining thinned bone must be removed with a Kerrison punch.
expand the opening with a Penfield dissector or curette while an assistant gently rotates the laminae towards the closed side using a Kocher or similar instrument (Fig. 5). Care must be taken to not allow the block of laminae to slip and rapidly snap back into original position; this may result in a spinal cord injury. The door may be kept open by placing suture through the facet capsule on the closed side and through the spinous processes (Fig. 6). Many variations on
Fig. 5. After the troughs have been cut, the ligamentum flavum between the rostral and caudal vertebrae and their respective rostral and caudal neighbors must be removed with a Kerrison punch. Now the door may be opened. Using a curette between the laminae and lateral mass on the open side and a Kocher on the spinous processes, the block of laminae is rotated towards the closed or hinged side. This effectively opens and expands the spinal canal.
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Fig. 6. The laminae may be help open with sutures passing around or through the spinous processes and the facet capsule on the closed side.
keeping the door open have been described. These include the use of titanium mini-plates [30], bone graft (allograft and autograft) [31], and ceramic spacers (Figs. 7 and 8). French door laminoplasty In the open-door expansive laminoplasty, the canal is opened on one side and hinged on the other. This essentially created an asymmetric expansion of the canal. In the French door laminoplasty, the door is opened in the midline and thus creates a symmetric opening of the canal [32]. It must be emphasized that one technique has not be proven superior to the other. Troughs are drilled on each side, usually C3–C7 at the laminae/facet junction. This is performed with a high-speed drill, with care not to drill all the way through the laminae. The laminae are then cut in the midline using a high-speed drill and fine Kerrison punches (Fig. 9). The laminae are then lifted off the spinal
Fig. 7. The laminae may also be held open with titanium mini-plates.
Fig. 8. An axial computed tomographic scan of a patient 6 months after a Hirabayashi-type open-door laminoplasty. Note the expansion of the spinal canal.
cord in the midline to expand the canal (Fig. 10). The laminae may then be secured in an open position using suture through the facet capsules and the laminae. In this original description, the canal is left open. Variations have been described to bridge the gap in the open laminae and recreate the protective arch. Pieces of the resected spinous processes may be secured with wire between the lamina, or ceramic spacers may be used [33].
Fig. 9. In the French door type laminoplasty, the spinous processes are split in the midline. They may be first cut at their bases to ease the midline cut. Troughs are then cut into the lamina at the junction of the lateral masses. The laminae are only thinned and not cut completely through.
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Fig. 10. After the completion of the trough cuts, the spinous processes are split in the midline. This may be performed with Kerrison punches or a high-speed drill, or both. The spinous processes are then spread in the midline and held open, similar to a French door. They may be held open with suture or small bone grafts.
Kurokawa modification In this modification of the French door laminoplasty, the dorsal aspect of the spinous processes is removed and used as grafts [34]. The spinous processes/laminae are cut in the midline using a high-speed drill. The spinous process is split open and held open with bone grafts that are wired in place. Tomita modification In this modification, the spinous process/laminae are split with a wire-saw. This has been termed the T-saw laminoplasty [35].
Postoperative management Some controversy exists in regard to the appropriate amount of time for postoperative immobilization. The senior author encourages early mobilization and does not employ a collar at all. Early mobilization of the neck followed by neck exercises is encouraged. Other authors have recommended hard collar immobilization for 4–8 weeks. Others recommend more limited cervical immobilization, with wearing of a hard collar for less than 4 weeks [36].
Complications In general, complications after laminoplasty are similar to those after laminectomy. Wound complications, such as dehiscence or infection, may be somewhat more common
after laminoplasty [36]. This is likely due to the block of laminae that are rotated and held open. Delayed deterioration may occur, although it is less likely due to a hematoma as would be in laminectomy; this is a result of the protective nature of the laminae. Delayed deterioration is caused by closing of the door or loss of the expansion. This may be the result of inadequate fixation of the open laminae or a fracture of the hardware (ie, titanium mini-plates); this may be seen on computed tomographic scanning. Furthermore, fracture of the hinged side of the laminoplasty may encroach on the spinal cord and lead to spinal cord injury. This complication may be disclosed on computed tomographic scanning. Laminectomy may be required if this complication occurs. Careful surgical technique will decrease the incidence of fracture of the hinge. Patients may complain of axial neck pain or stiffness after laminoplasty. Its true incidence is unknown because it is not consistently reported in the literature. It may be a result of the surgical manipulation and dissection around the facet joints [36]. The pain usually begins shortly after surgery, but usually resolves within one year. Some advocate early postoperative cervical mobilization [36]. Nonsteroidal anti-inflammatory medications and cervical stretching and strengthening exercises may also be effective, but this has not been proven. Neurological complications are theoretically less after laminoplasty compared with laminectomy [36]. This is likely a result of the need not to put any instruments under the lamina on top of the spinal cord. Nerve root palsy has been reported to occur after laminoplasty. Similar to any dorsal decompressive operation, nerves may be injured by mechanical injury during dissection for removal of bone (ie, drill or punch). Isolated nerve root palsy may occurs after laminoplasty, but has also been reported after laminectomy [37–39]. It is predominantly a motor weakness, less so sensory changes. It affects C5 greater than other cervical roots. It usually begins 1–3 days after surgery and begins with deltoid weakness and shoulder pain. The weakness may be profound. The incidence of C5 palsy was 11% in one series, 9% motor weakness and 2% sensory changes [38]. The authors studied this injury in relation to the type of laminoplasty performed. Interestingly, there was a greater prevalence in those procedures that included foraminotomy or facetectomy (or both) compared with those that did not in this series. The reason for C5 palsy is unknown, but it is likely caused by the course of the nerve through its foramen and traction on the nerve as the cord migrates dorsally [37–39]. Other series have attributed postoperative C5 palsy to intraoperative nerve root trauma, to unrecognized preoperative foraminal stenosis as well as to intrinsic changes existing within the spinal cord before surgery. The pain may be controlled with physical therapy and nonsteroidal anti-inflammatory drugs. The motor palsy usually recovers to normal or near normal within 12 months after surgery. Foraminotomy and facetectomy have been tried in order to prevent this complication; neither has proven
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effective. A controlled opening of the ‘‘door’’ may aid in the prevention of this complication.
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has been reported to range from 2% to 4%, with 0% in the hardware augmentation group. Not all authors measure cervical alignment in a similar manner, and therefore results may not be directly comparable.
Outcome Neurologic Most authors report outcome based on the Japanese Orthopedic Association scoring system. Reported results include mean preoperative and postoperative scores for all patients, and a calculated rate of recovery is provided. The mean recovery rate after the Hirabayashi expansive laminoplasty is approximately 60% [10,12– 14,16,17,21,24,26,29,40–43]. Herkowitz studied anterior arthrodesis, laminectomy, and laminoplasty for the management of multilevel cervical spondylosis [26]. The author concluded that anterior cervical arthrodesis was superior, but laminoplasty was a useful alternative. Herkowitz also reported on the Hirabayashi type laminoplasty with unilateral foraminotomy on the open-door side; the reported rate of recovery was 90% [44]. Other authors have reported a mean improvement of 56% with Baba and Tomita’s modification of the Hirabayashi laminoplasty [10,45]. Overall, the majority of patients reported some neurological improvement. In the French door laminoplasty and its modifications, the mean recovery rate is approximately 50% [18, 22,23,25,35]. Similar results have been reported in the hardware assisted laminoplasty literature [30,46]. In general, the overall recovery rate is reported to range from 50% to 70%. The range of recovery is likely related to the degree of preoperative myelopathy and not the specific surgical procedure. As previously noted, no one surgical technique has proved more effective than another. Laminoplasty has been used for the treatment of cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL). In some series, patients with CSM had better recovery compared with OPLL [15], whereas in others, a better recovery was reported with CSM. Outcome is more likely related to preoperative neurologic status and not the disease process or surgical procedure. Cervical alignment In general, no specific laminoplasty technique has been able to prevent the development of some degree of kyphosis after surgery. Moreover, no laminoplasty technique is effective for the restoration of lordosis in an already kyphotic spine. The range of worsening spinal alignment, not necessarily kyphosis, has been reported to range from 22% to 53% [11,15–17,24,42,43,47]. This loss of lordosis is not improved with the addition of a posterolateral fusion [28,48]. Other authors have reported much better preservation of lordosis with the use of modern instrumentation techniques [46]. The incidence of development of kyphosis
Range of motion Cervical ROM has been reported to decrease 17–50%, with an average of approximately 50% after laminoplasty. [2,10–25]. When laminoplasty is augmented with fusion, ROM was decreased 70–80% [27]. The clinical relevance of this decreased ROM is controversial. Some authors have noted the beneficial nature of this decreased ROM. The decreased ROM has been noted to limit dynamic factors which are thought to contribute to myelopathy [16]. It may also aid in the prevention of OPLL progression [25]. Other authors have noted a benefit to the maintenance of cervical ROM. It is thought that this improved ROM decreases axial neck pain after laminoplasty and prevents adjacent segment cervical disease [30]. In long-term follow-up studies, there is a clear trend towards a decrease in cervical ROM. Seichi et al. reported a significant rate of spontaneous facet fusion in their patients whom they monitored for at least 10 years after laminoplasty [22].
Long-term outcome A few studies have reported long-term outcome after laminoplasty. Miyazaki et al. observed that improved neurologic status was maintained at a mean of 12 years after surgery [27]. Kawai et al. reported 10-year follow-up after Z-type laminoplasty. Patients with CSM were stable after surgery, whereas those with OPLL demonstrated some late deterioration [15]. Similarly, Seichi et al. documented lasting benefit after laminoplasty for patients with CSM, while only 20% of those patients operated upon for OPLL demonstrated late worsening [22]. It appears that OPLL may progress despite laminoplasty. In general, improvement after laminoplasty is stable, even up to 10 years after surgery.
Comparison with laminectomy or fusion Few authors have directly compared laminoplasty with laminectomy with or without fusion. Kaminsky et al. compared two similar groups of patients treated with laminoplasty or laminectomy for CSM [49]. Using the modified Nurick grading scale, they noted similar rates of improvement between both groups; however, the laminoplasty group had a lower incidence of cervical pain. Measures of neck stiffness were similar between both groups, and ROM was decreased in the laminoplasty patients. Edwards et al. reported on a matched cohort of patients treated with laminoplasty or ventral decompression and fusion [50]. Neurological improvement was significantly better in the laminoplasty group, although the disease was found to be
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stabilized with both treatment strategies. Complication rates and pain medication usage were lower in the laminoplasty group.
Conclusions Laminoplasty, popularized in the 1980s, is now used for a variety of cervical disorders. Multiple variations on the theme have been developed, but all are similar in that they expand the cervical canal while leaving the protective dorsal elements in place to varying degrees. Advocates claim that this prevents the formation of the ‘‘postlaminectomy’’ membrane, maintains spinal alignment, and should aid in maintaining cervical ROM. The procedure has proven to be essentially equal to other cervical decompressive procedures, and outcome has been shown to be durable. Laminoplasty is an effective procedure for the decompression of multilevel cervical disease, CSM, and OPLL. Moreover, it may be used for certain spinal cord tumors, especially in children. References [1] Oyama M, Hattori S, Moriwaki N. A new method of posterior decompression. [Japanese]. Chubuseisaisi 1973;16:792. [2] Hirabayashi K, Miyagawa J, Satomi K, Maruyama T, Wakano K. Operative results and postoperative progression of ossification among patients with ossification of cervical posterior longitudinal ligament. Spine 1981;6:354–64. [3] Kaptain G, Simmons NE, Replogle RE, Pobereskin L. Incidence and outcome of kyphotic deformity following laminectomy for cervical spondylotic myelopathy. J Neurosurg (Spine 2) 2000;93:199–204. [4] Mikawa Y, Shikata J, Yamamuro T. Spinal deformity and instability after multilevel cervical laminectomy. Spine 1987;12:6–11. [5] Sim F, Svien HJ, Bickel WH, Janes JM. Swan-neck deformity following extensive cervical laminectomy: A review of 21 cases. J Bone Joint Surg Am 1974;56:564–80. [6] Cattell H, Clark GL Jr. Cervical kyphosis and instability following multiple laminectomies in children. J Bone Joint Surg Am 1967;24:713–20. [7] Kumar V, Rea GL, Mervis LJ, McGregor JM. Cervical spondylotic myelopathy: functional and radiographic long-term outcome after laminectomy and posterior fusion. Neurosurgery 1999;44:771–8. [8] Aita I, Hayashi K, Wadano Y, Yabuki T. Posterior movement and enlargement of the spinal cord after cervical laminoplasty. J Bone Joint Surg Br 1998;80:33–7. [9] Sodeyama T, Goto S, Mochizuki M, Takahashi J, Moriya H. Effect of decompression enlargement laminoplasty for posterior shifting of the spinal cord. Spine 1999;24:1527–32. [10] Baba H, Chen Q, Uchida K, et al. Laminoplasty with foraminotomy for coexisting cervical myelopathy and unilateral radiculopathy: a preliminary report. Spine 1996;21:196–202. [11] Edwards CC II, Heller JG, Silcox DH III. T-saw laminoplasty for the management of cervical spondylotic myelopathy: clinical and radiographic outcome. Spine 2000;24:1788–94. [12] Inoue H, Ohmori K, Ishida Y, Suzuki K, Takatsu T. Long-term follow-up review of suspension laminotomy for cervical compression myelopathy. J Neurosurg 1996;85:817–23. [13] Itoh T, Tsuji H. Technical improvements and results of laminoplasty for compressive myelopathy in the cervical spine. Spine 1985;10: 729–36.
[14] Kawaguchi Y, Matsui H, Ishihara H. Surgical outcome of cervical expansive laminoplasty in patients with diabetes mellitus. Spine 2000;25:551–5. [15] Kawai S, Sunago K, Doi K, Saka M, Taguchi T. Cervical laminoplasty (Hattori’s method), procedure and follow-up results). Spine 1988;13:1245–50. [16] Kimura I, Shingu H, Nasu Y. Long-term follow-up of cervical spondylotic myelopathy treated by canal-expansive laminoplasty. J Bone Joint Surg Br 1995;77:956–61. [17] Mochida J, Nomura T, Chiba M, Nishmaura K, Toh E. Modified expansive open-door laminoplasty in cervical myelopathy. J Spinal Disord 1999;12:386–91. [18] Morimoto T, Matsuyama T, Hirabayashi H, Sakaki T, Yabuno T. Expansive laminoplasty for multilevel cervical OPLL. J Spinal Disord 1997;10:296–8. [19] Saruhashi Y, Hukuda S, Katsuura A, Miyahara K, Asajima S, Omura K. A long-term follow-up study of cervical spondylotic myelopathy treated by ‘‘French Window’’ laminoplasty. J Spinal Disord 1999;12:99–101. [20] Sasai K, Saito T, Akagi S, Kato I, Ogawa R. Cervical curvature after laminoplasty for spondylotic myelopathy: involvement of yellow ligament, semispinalis, cervicis muscle, and nuchal ligament. J Spinal Disord 2000;13:26–30. [21] Satomi K, Nishu Y, Kohno T, Hirabayashi K. Long-term follow-up studies of open-door expansive laminoplasty for cervical stenotic myelopathy. Spine 1994;19:507–10. [22] Seichi A, Takeshita K, Ohishi I, et al. Long-term results of doubledoor laminoplasty for cervical stenotic myelopathy. Spine 2001;479–87. [23] Takayasu M, Takagi T, Nishizawa T, Osuka K, Nakajima T, Yoshida J. Bilateral open-door cervical expansive laminoplasty with hydroxyapatite spacers and titanium screws. J Neurosurg (Spine 1) 2001;96:22–8. [24] Wada E, Suzuki S, Kanazawa A, Matsuoka T, Miyamoto S, Yonenobu K. Subtotal corpectomy versus laminoplasty for multilevel cervical spondylotic myelopathy: a long-term follow-up study over 10 years. Spine 2001;26:1443–8. [25] Yoshida M, Otani K, Shibasaki K, Ueda S. Expansive laminoplasty with reattachment of spinous process and extensor musculature for cervical myelopathy. Spine 1992;17:491–7. [26] Herkowitz H. A comparison of anterior cervical fusion, cervical laminectomy, and cervical laminoplasty for the surgical management of multiple level spondylotic radiculopathy. Spine 1988;13:774–80. [27] Miyazaki K, Hirohuji E, Ono S. Extensive simultaneous multi-segmental laminectomy and posterior decompression with posterolateral fusion. J Jpn Spine Res Soc 1994;5:167. [28] Miyazaki K, Tada K, Matsuda Y, Okuno M, Yasuda T, Morakami H. Posterior extensive simultaneous multisegment decompression with posterolateral fusion for cervical myelopathy with cervical instability and kyphotic and/or S-shaped deformities. Spine 1989;14: 1160–70. [29] Kimura I, Oh-Hama M, Shingu H. Cervical myelopathy treated by canal-expansive laminoplasty: computed tomographic and myelographic findings. J Bone Joint Surg Am 1995;66:914–20. [30] Shaffrey C, Wiggins GC, Piccirilli CB, Young JN, Lovell LR. Modified open-door laminoplasty for treatment of neurological deficits in younger patients with congenital spinal stenosis: analysis of clinical and radiographic data. J Neurosurg (Spine) 1999;90:170–7. [31] Matsuzaki H, Hoshino M, Kiuchi T, Toriyama S. Dome-like expansive laminoplasty for the second cervical vertebrae. Spine 1989;14: 1198–203. [32] Hukuda S, Mochizuki T, Ogata M, Shichikawa K, Shimomura Y. Operations for cervical spondylotic myelopathy: a comparison of the results of anterior and posterior procedures. J Bone Joint Surg 1985;67: 609–15. [33] Hase H, Watanabe T, Hirasawa Y, et al. Bilateral open laminoplasty using ceramic laminas for cervical myelopathy. Spine 1991;16: 1269–76.
M.P. Steinmetz and D.K. Resnick / The Spine Journal 6 (2006) 274S–281S [34] Kurokawa T, Tsuyama N, Tanaka H. Enlargement of spinal canal by the sagittal splitting of the spinous process. Bessatusu Seikeigeka 1982;2:234–40. [35] Tomita K, Kawahara N, Toribatake Y, Heller JG. Expansive midline T-saw laminoplasty (modified spinous process-splitting) for the management of cervical myelopathy. Spine 1998;23:22–7. [36] Yonenobu K, Wada E, Ono K. Laminoplasty. In: Clark CR, editor. The cervical spine. Philadelphia: Lippincott Williams and Wilkins, 2005:1057–71. [37] Tsuzuki N, Zhogshi L, Abe R. Paralysis of the arm after posterior decompression of the cervical spinal cord. 1. Anatomical investigation of the mechanism of paralysis. Eur Spine J 1993;2:191–6. [38] Tsuzuki N, Abe R, Saiki K. Paralysis of the arm after posterior decompression of the cervical spinal cord. 2. Analyses of clinical findings. Eur Spine J 1993;2:197–202. [39] Yonenobu K, Hosono N, Iwasaki M, Asano M, Ono K. Neurological complications of surgery for cervical compression myelopathy. Spine 1991;16:1277–82. [40] Chiba K, Toyama Y, Watanabe M, Maruiwa H, Maksumoto M, Hirabayashi K. Impact of longitudinal distance of the cervical spine on the results of expansive open-door laminoplasty. Spine 2000;25:2893–8. [41] Hirabayashi K, Satomi K. Operative procedure and results of expansive open-door laminoplasty. Spine 1988;13:870–6. [42] Lee T, Manazano GR, Green BA. Modified open-door cervical expansive laminoplasty for spondylotic myelopathy: operative technique, outcome, and predictors for gait improvement. J Neurosurg 1997;86:64–8.
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[43] Yonenobu K, Hosono N, Iwasaki M, Asano M, Ono K. Laminoplasty versus subtotal corpectomy: a comparative study of results in multisegmental cervical spondylotic myelopathy. Spine 1992;17: 1281–4. [44] Herkowitz H. Cervical laminoplasty: its role in the treatment of cervical radiculopathy. J Spinal Disord 1988;1:179–88. [45] Tomita K, Nokuma S, Umeda S, Baba H. Cervical laminoplasty to enlarge the spinal canal in multilevel ossification of the posterior longitudinal ligament with myelopathy. Arch Orthop Trauma Surg 1988;107:148–53. [46] O’Brien M, Peterson D, Casey ATH, Crockard HA. A novel technique for laminoplasty augmentation of spinal canal area using titanium miniplate stabilization: a computerized morphometric analysis. Spine 1996;21:474–84. [47] Matsunaga S, Sakou T, Nakanisi K. Analysis of the cervical spine alignment following laminoplasty and laminectomy. Spinal Cord 1999;37:20–4. [48] Morio Y, Yamamoto K, Teshima R, Nagashima H, Hagino H. Clinicoradiologic study of cervical laminoplasty with posterolateral fusion or bone graft. Spine 2000;25:190–6. [49] Kaminsky SB, Clark CR, Traynelis VC. Operative treatment of cervical spondylotic myelopathy and radiculopathy: a comparison of laminectomy and laminoplasty at five year average follow-up. Iowa Orthop J 2004;24:95–105. [50] Edwards CC II, Heller JG, Murakami H. Corpectomy versus laminoplasty for multilevel cervical myelopathy: an independent matchedcohort analysis. Spine 2002;25:1168–75.
Cervical laminoplasty Michael P. Steinmetz, MD, Daniel K. Resnick, MD* Department of Neurosurgery, University of Wisconsin School of Medicine, K4/834 Clinical Science Center, 600 Highland Ave., Madison, WI 53792, USA
Abstract
Laminoplasty was developed to treat multilevel pathology of the cervical spine, namely ossification of the posterior longitudinal ligament and cervical spondylotic myelopathy. Laminoplasty was popularized in the 1980s, and since then many variations on the theme have been developed. All are similar in that they expand the cervical canal while leaving the protective dorsal elements in place. Advocates claim that this prevents the formation of the ‘‘postlaminectomy’’ membrane, maintains spinal alignment, and should aid in maintaining cervical range of motion. The aforementioned are all potential shortcomings of laminectomy or laminectomy and fusion. The procedure has proven to be essentially equal to other cervical decompressive procedures in the neutral or lordotic spine, and outcome has been shown to be durable. Ó 2006 Elsevier Inc. All rights reserved.
Keywords:
Laminoplasty; Cervical spine; Laminectomy; Ossification of the posterior longitudinal ligament; Cervical spondylotic myelopathy; Myelopathy; Cervical stenosis
Introduction Cervical laminectomy has long been the treatment for multilevel cervical spondylosis. It permits adequate decompression of the cervical spinal cord and is safe and easily performed. Potential adverse outcomes after cervical laminectomy include instability and epidural scar formation. It has been hypothesized that this scar may be responsible for persistent postoperative cervical and head pain after surgery and even neurologic deterioration. Fear of instability has resulted in many surgeons performing a simultaneous fusion operation at the time of laminectomy. This potentially adds morbidity to the procedure, there may be nonunion or construct failure, and it reduces motion in the cervical spine. Laminoplasty was developed to widen the spinal canal dimensions without permanently removing the dorsal elements of the cervical spine. The retained dorsal elements should aid in the prevention of muscle scarring to the dura (ie, result in less cervical and head pain after surgery) and FDA device/drug status: approved but not for this indication (miniplates). Author DKR acknowledges a financial relationship (consultant with Medtronic) that may indirectly relate to the subject of this research. * Corresponding author. Dept. of Neurological Surgery, University of Wisconsin School of Medicine, K4/834 Clinical Science Center, 600 Highland Ave., Madison, WI 53792. Tel.: (608) 263-9651; fax: (608) 263-1728. E-mail address: [email protected] (D.K. Resnick) 1529-9430/06/$ – see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2006.04.023
potentially reduce the incidence of postoperative instability. Cervical motion is theoretically preserved. In 1973, Oyama et al. introduced a Z-plasty of the cervical spine [1]. This procedure allowed decompression, while the retained laminae provided support and prevented invasion of the postlaminectomy membrane. Hirabayashi et al. reported on the open-door laminoplasty in 1981 [2]. Following this publication, various modifications have been developed that are purported to improve the safety and effectiveness of the procedure.
Goals of laminoplasty The main goal of laminoplasty is to provide decompression of the spinal cord by widening the spinal canal while preventing instability after decompression (ie, development of kyphosis) and scar in-growth with potential neurological deterioration after surgery. The development of postsurgical cervical kyphosis is well described [3–5], especially in children [6]. The risk has been shown to be reduced with lateral mass fixation [7], and theoretically with laminoplasty, although some loss of lordosis is often seen. The maximum region of canal expansion is on the open side in hinge-type procedures and in the midline in bilateral hinge operations. Migration of the cord away from the ventral vertebral bodies has been documented in both varieties
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of laminoplasties [8,9]. This has been confirmed with postoperative computed tomographic myelography. Although the performance of a laminoplasty procedure allows for a decompression without a fusion, there still does appear to be some loss of motion associated with the procedure. Many studies have reported a loss in cervical range of motion (ROM) after laminoplasty. The degree of loss of ROM ranges from 17% to 50% in published series, with most authors reporting an approximate 50% loss of global ROM [2,10–25]. The loss of ROM is in flexion, extension, rotation, and lateral bending. It is of note that some authors have not reported any change of ROM after laminoplasty [26]. The loss of ROM after laminoplasty should be taken in context, however, as fusion results in a much more substantial loss of motion [27,28]. Some authors believe that the increased stiffness seen after laminoplasty decreases the potential for injury to the cord via dynamic movements [29] and aids in the resolution of ossification of the posterior longitudinal ligament (OPLL) [25]. In contrast, some authors believe that maintaining ROM is crucial. For example, Shaffrey et al. emphasized the maintenance of cervical ROM via laminoplasty as a means to avoid adjacent-segment disease [30].
Limitations and contraindications Indications for laminoplasty include multilevel cervical spondylosis and OPLL. It may also be used for certain varieties of spinal cord tumors. The procedure is generally contraindicated in kyphotic cervical pathology. It is possible to perform laminoplasty in a straightened spine, but a lordotic posture is preferred. As noted above, most studies document loss of cervical lordosis after surgery. Laminoplasty is generally not indicated for one- or two-level disease. The limited length of decompression in such cases generally does not allow the free migration of the spinal cord away from the ventral elements.
Fig. 1. In the Z-Plasty, troughs are first drilled into the lamina at the junction of the lateral mass. The laminae are then thinned. After this, a ‘‘Z’’ is cut in the laminae with a high-speed drill. Note the dotted line of the proposed cut.
Z-Plasty This technique was originally described by Oyama et al. [1]. In this procedure, the spinous processes are first removed and the laminae thinned. They are thinned out to the laminae–facet junction. Troughs are performed laterally. At this point a ‘‘Z’’ is cut into the thinned laminae (Fig. 1). This may be performed with a high-speed drill and diamond drill bit or a fine Kerrison punch. After the ‘‘Z’’ cut, the thinned sections of laminae may then be separated and the canal opened or expanded. The laminae may then be secured with suture or wire to maintain the expanded canal (Fig. 2).
Laminoplasty techniques Many techniques that are variations of laminoplasty have been described. They are all similar in that they expand the cervical canal and preserve some or all of the posterior elements. Modifications on where the cuts in the lamina or spinous processes are made and how the canal is kept open have been developed. Newer techniques, such as the use of ceramic spacers and titanium miniplates have been proposed, which may decrease the surgical time and improve the safety of the procedure. No one procedure has proven to be more effective than any other in terms of neurological outcome, cervical alignment, or ROM.
Hirabayashi laminoplasty Hirabayashi and colleagues described the expansive open-door laminoplasty [2]. In this technique, the spinous processes and laminae are exposed from C2–C7. The supraspinous and interspinous ligaments are preserved and not injured. In the authors’ experience, the ligaments must be cut between C2 and C3 and C7 and T1, depending on which levels are to be expanded. This aids in ‘‘opening the door’’. Using a high-speed drill, a trough is created on the ‘‘open’’ side at the junction between the laminae and the facets (Fig. 3). The trough is drilled down to the
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Fig. 4. After drilling the complete trough on the open-door side, a second trough is drilled on the closed side. Care must be taken not to drill all the way through the lamina. This will lead to fracture of the hinge and an ineffective open-door laminoplasty.
Fig. 2. After the cuts, the laminae are spread apart and held with wires or suture, effectively widening the canal.
ligamentum flavum. One may drill all the way through the laminae or one may leave a very thin remnant of laminae, especially at its cranial aspect. This thin rim and associated ligament are then removed with a 1-mm or 2-mm Kerrison punch. A second trough is then drilled in the opposite or ‘‘closed’’ side with a high-speed drill (Fig. 4). Care is taken to only thin the lamina on this side and not cut all the way through. This trough is cut somewhat more lateral as compared with the ‘‘open’’ side. The opening on the open side is then gently expanded, thus lifting the lamina off the spinal cord and expanding the canal. The surgeon may gently
Fig. 3. In the Hirabayashi-type open-door laminoplasty, a trough is first drilled in the laminae. This is done somewhat more medial then the lamina, lateral mass junction. The cut is taken down to dura. The ligament and any remaining thinned bone must be removed with a Kerrison punch.
expand the opening with a Penfield dissector or curette while an assistant gently rotates the laminae towards the closed side using a Kocher or similar instrument (Fig. 5). Care must be taken to not allow the block of laminae to slip and rapidly snap back into original position; this may result in a spinal cord injury. The door may be kept open by placing suture through the facet capsule on the closed side and through the spinous processes (Fig. 6). Many variations on
Fig. 5. After the troughs have been cut, the ligamentum flavum between the rostral and caudal vertebrae and their respective rostral and caudal neighbors must be removed with a Kerrison punch. Now the door may be opened. Using a curette between the laminae and lateral mass on the open side and a Kocher on the spinous processes, the block of laminae is rotated towards the closed or hinged side. This effectively opens and expands the spinal canal.
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Fig. 6. The laminae may be help open with sutures passing around or through the spinous processes and the facet capsule on the closed side.
keeping the door open have been described. These include the use of titanium mini-plates [30], bone graft (allograft and autograft) [31], and ceramic spacers (Figs. 7 and 8). French door laminoplasty In the open-door expansive laminoplasty, the canal is opened on one side and hinged on the other. This essentially created an asymmetric expansion of the canal. In the French door laminoplasty, the door is opened in the midline and thus creates a symmetric opening of the canal [32]. It must be emphasized that one technique has not be proven superior to the other. Troughs are drilled on each side, usually C3–C7 at the laminae/facet junction. This is performed with a high-speed drill, with care not to drill all the way through the laminae. The laminae are then cut in the midline using a high-speed drill and fine Kerrison punches (Fig. 9). The laminae are then lifted off the spinal
Fig. 7. The laminae may also be held open with titanium mini-plates.
Fig. 8. An axial computed tomographic scan of a patient 6 months after a Hirabayashi-type open-door laminoplasty. Note the expansion of the spinal canal.
cord in the midline to expand the canal (Fig. 10). The laminae may then be secured in an open position using suture through the facet capsules and the laminae. In this original description, the canal is left open. Variations have been described to bridge the gap in the open laminae and recreate the protective arch. Pieces of the resected spinous processes may be secured with wire between the lamina, or ceramic spacers may be used [33].
Fig. 9. In the French door type laminoplasty, the spinous processes are split in the midline. They may be first cut at their bases to ease the midline cut. Troughs are then cut into the lamina at the junction of the lateral masses. The laminae are only thinned and not cut completely through.
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Fig. 10. After the completion of the trough cuts, the spinous processes are split in the midline. This may be performed with Kerrison punches or a high-speed drill, or both. The spinous processes are then spread in the midline and held open, similar to a French door. They may be held open with suture or small bone grafts.
Kurokawa modification In this modification of the French door laminoplasty, the dorsal aspect of the spinous processes is removed and used as grafts [34]. The spinous processes/laminae are cut in the midline using a high-speed drill. The spinous process is split open and held open with bone grafts that are wired in place. Tomita modification In this modification, the spinous process/laminae are split with a wire-saw. This has been termed the T-saw laminoplasty [35].
Postoperative management Some controversy exists in regard to the appropriate amount of time for postoperative immobilization. The senior author encourages early mobilization and does not employ a collar at all. Early mobilization of the neck followed by neck exercises is encouraged. Other authors have recommended hard collar immobilization for 4–8 weeks. Others recommend more limited cervical immobilization, with wearing of a hard collar for less than 4 weeks [36].
Complications In general, complications after laminoplasty are similar to those after laminectomy. Wound complications, such as dehiscence or infection, may be somewhat more common
after laminoplasty [36]. This is likely due to the block of laminae that are rotated and held open. Delayed deterioration may occur, although it is less likely due to a hematoma as would be in laminectomy; this is a result of the protective nature of the laminae. Delayed deterioration is caused by closing of the door or loss of the expansion. This may be the result of inadequate fixation of the open laminae or a fracture of the hardware (ie, titanium mini-plates); this may be seen on computed tomographic scanning. Furthermore, fracture of the hinged side of the laminoplasty may encroach on the spinal cord and lead to spinal cord injury. This complication may be disclosed on computed tomographic scanning. Laminectomy may be required if this complication occurs. Careful surgical technique will decrease the incidence of fracture of the hinge. Patients may complain of axial neck pain or stiffness after laminoplasty. Its true incidence is unknown because it is not consistently reported in the literature. It may be a result of the surgical manipulation and dissection around the facet joints [36]. The pain usually begins shortly after surgery, but usually resolves within one year. Some advocate early postoperative cervical mobilization [36]. Nonsteroidal anti-inflammatory medications and cervical stretching and strengthening exercises may also be effective, but this has not been proven. Neurological complications are theoretically less after laminoplasty compared with laminectomy [36]. This is likely a result of the need not to put any instruments under the lamina on top of the spinal cord. Nerve root palsy has been reported to occur after laminoplasty. Similar to any dorsal decompressive operation, nerves may be injured by mechanical injury during dissection for removal of bone (ie, drill or punch). Isolated nerve root palsy may occurs after laminoplasty, but has also been reported after laminectomy [37–39]. It is predominantly a motor weakness, less so sensory changes. It affects C5 greater than other cervical roots. It usually begins 1–3 days after surgery and begins with deltoid weakness and shoulder pain. The weakness may be profound. The incidence of C5 palsy was 11% in one series, 9% motor weakness and 2% sensory changes [38]. The authors studied this injury in relation to the type of laminoplasty performed. Interestingly, there was a greater prevalence in those procedures that included foraminotomy or facetectomy (or both) compared with those that did not in this series. The reason for C5 palsy is unknown, but it is likely caused by the course of the nerve through its foramen and traction on the nerve as the cord migrates dorsally [37–39]. Other series have attributed postoperative C5 palsy to intraoperative nerve root trauma, to unrecognized preoperative foraminal stenosis as well as to intrinsic changes existing within the spinal cord before surgery. The pain may be controlled with physical therapy and nonsteroidal anti-inflammatory drugs. The motor palsy usually recovers to normal or near normal within 12 months after surgery. Foraminotomy and facetectomy have been tried in order to prevent this complication; neither has proven
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effective. A controlled opening of the ‘‘door’’ may aid in the prevention of this complication.
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has been reported to range from 2% to 4%, with 0% in the hardware augmentation group. Not all authors measure cervical alignment in a similar manner, and therefore results may not be directly comparable.
Outcome Neurologic Most authors report outcome based on the Japanese Orthopedic Association scoring system. Reported results include mean preoperative and postoperative scores for all patients, and a calculated rate of recovery is provided. The mean recovery rate after the Hirabayashi expansive laminoplasty is approximately 60% [10,12– 14,16,17,21,24,26,29,40–43]. Herkowitz studied anterior arthrodesis, laminectomy, and laminoplasty for the management of multilevel cervical spondylosis [26]. The author concluded that anterior cervical arthrodesis was superior, but laminoplasty was a useful alternative. Herkowitz also reported on the Hirabayashi type laminoplasty with unilateral foraminotomy on the open-door side; the reported rate of recovery was 90% [44]. Other authors have reported a mean improvement of 56% with Baba and Tomita’s modification of the Hirabayashi laminoplasty [10,45]. Overall, the majority of patients reported some neurological improvement. In the French door laminoplasty and its modifications, the mean recovery rate is approximately 50% [18, 22,23,25,35]. Similar results have been reported in the hardware assisted laminoplasty literature [30,46]. In general, the overall recovery rate is reported to range from 50% to 70%. The range of recovery is likely related to the degree of preoperative myelopathy and not the specific surgical procedure. As previously noted, no one surgical technique has proved more effective than another. Laminoplasty has been used for the treatment of cervical spondylotic myelopathy (CSM) and ossification of the posterior longitudinal ligament (OPLL). In some series, patients with CSM had better recovery compared with OPLL [15], whereas in others, a better recovery was reported with CSM. Outcome is more likely related to preoperative neurologic status and not the disease process or surgical procedure. Cervical alignment In general, no specific laminoplasty technique has been able to prevent the development of some degree of kyphosis after surgery. Moreover, no laminoplasty technique is effective for the restoration of lordosis in an already kyphotic spine. The range of worsening spinal alignment, not necessarily kyphosis, has been reported to range from 22% to 53% [11,15–17,24,42,43,47]. This loss of lordosis is not improved with the addition of a posterolateral fusion [28,48]. Other authors have reported much better preservation of lordosis with the use of modern instrumentation techniques [46]. The incidence of development of kyphosis
Range of motion Cervical ROM has been reported to decrease 17–50%, with an average of approximately 50% after laminoplasty. [2,10–25]. When laminoplasty is augmented with fusion, ROM was decreased 70–80% [27]. The clinical relevance of this decreased ROM is controversial. Some authors have noted the beneficial nature of this decreased ROM. The decreased ROM has been noted to limit dynamic factors which are thought to contribute to myelopathy [16]. It may also aid in the prevention of OPLL progression [25]. Other authors have noted a benefit to the maintenance of cervical ROM. It is thought that this improved ROM decreases axial neck pain after laminoplasty and prevents adjacent segment cervical disease [30]. In long-term follow-up studies, there is a clear trend towards a decrease in cervical ROM. Seichi et al. reported a significant rate of spontaneous facet fusion in their patients whom they monitored for at least 10 years after laminoplasty [22].
Long-term outcome A few studies have reported long-term outcome after laminoplasty. Miyazaki et al. observed that improved neurologic status was maintained at a mean of 12 years after surgery [27]. Kawai et al. reported 10-year follow-up after Z-type laminoplasty. Patients with CSM were stable after surgery, whereas those with OPLL demonstrated some late deterioration [15]. Similarly, Seichi et al. documented lasting benefit after laminoplasty for patients with CSM, while only 20% of those patients operated upon for OPLL demonstrated late worsening [22]. It appears that OPLL may progress despite laminoplasty. In general, improvement after laminoplasty is stable, even up to 10 years after surgery.
Comparison with laminectomy or fusion Few authors have directly compared laminoplasty with laminectomy with or without fusion. Kaminsky et al. compared two similar groups of patients treated with laminoplasty or laminectomy for CSM [49]. Using the modified Nurick grading scale, they noted similar rates of improvement between both groups; however, the laminoplasty group had a lower incidence of cervical pain. Measures of neck stiffness were similar between both groups, and ROM was decreased in the laminoplasty patients. Edwards et al. reported on a matched cohort of patients treated with laminoplasty or ventral decompression and fusion [50]. Neurological improvement was significantly better in the laminoplasty group, although the disease was found to be
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stabilized with both treatment strategies. Complication rates and pain medication usage were lower in the laminoplasty group.
Conclusions Laminoplasty, popularized in the 1980s, is now used for a variety of cervical disorders. Multiple variations on the theme have been developed, but all are similar in that they expand the cervical canal while leaving the protective dorsal elements in place to varying degrees. Advocates claim that this prevents the formation of the ‘‘postlaminectomy’’ membrane, maintains spinal alignment, and should aid in maintaining cervical ROM. The procedure has proven to be essentially equal to other cervical decompressive procedures, and outcome has been shown to be durable. Laminoplasty is an effective procedure for the decompression of multilevel cervical disease, CSM, and OPLL. Moreover, it may be used for certain spinal cord tumors, especially in children. References [1] Oyama M, Hattori S, Moriwaki N. A new method of posterior decompression. [Japanese]. Chubuseisaisi 1973;16:792. [2] Hirabayashi K, Miyagawa J, Satomi K, Maruyama T, Wakano K. Operative results and postoperative progression of ossification among patients with ossification of cervical posterior longitudinal ligament. Spine 1981;6:354–64. [3] Kaptain G, Simmons NE, Replogle RE, Pobereskin L. Incidence and outcome of kyphotic deformity following laminectomy for cervical spondylotic myelopathy. J Neurosurg (Spine 2) 2000;93:199–204. [4] Mikawa Y, Shikata J, Yamamuro T. Spinal deformity and instability after multilevel cervical laminectomy. Spine 1987;12:6–11. [5] Sim F, Svien HJ, Bickel WH, Janes JM. Swan-neck deformity following extensive cervical laminectomy: A review of 21 cases. J Bone Joint Surg Am 1974;56:564–80. [6] Cattell H, Clark GL Jr. Cervical kyphosis and instability following multiple laminectomies in children. J Bone Joint Surg Am 1967;24:713–20. [7] Kumar V, Rea GL, Mervis LJ, McGregor JM. Cervical spondylotic myelopathy: functional and radiographic long-term outcome after laminectomy and posterior fusion. Neurosurgery 1999;44:771–8. [8] Aita I, Hayashi K, Wadano Y, Yabuki T. Posterior movement and enlargement of the spinal cord after cervical laminoplasty. J Bone Joint Surg Br 1998;80:33–7. [9] Sodeyama T, Goto S, Mochizuki M, Takahashi J, Moriya H. Effect of decompression enlargement laminoplasty for posterior shifting of the spinal cord. Spine 1999;24:1527–32. [10] Baba H, Chen Q, Uchida K, et al. Laminoplasty with foraminotomy for coexisting cervical myelopathy and unilateral radiculopathy: a preliminary report. Spine 1996;21:196–202. [11] Edwards CC II, Heller JG, Silcox DH III. T-saw laminoplasty for the management of cervical spondylotic myelopathy: clinical and radiographic outcome. Spine 2000;24:1788–94. [12] Inoue H, Ohmori K, Ishida Y, Suzuki K, Takatsu T. Long-term follow-up review of suspension laminotomy for cervical compression myelopathy. J Neurosurg 1996;85:817–23. [13] Itoh T, Tsuji H. Technical improvements and results of laminoplasty for compressive myelopathy in the cervical spine. Spine 1985;10: 729–36.
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