Cervical Laminoplasty Michael P

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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 potentially reduce the incidence of postoperative instability. Cervical motion is theoretically preserved. In 1973, Oyama Cervical laminectomy has long been the treatment for et al. introduced a Z-plasty of the cervical spine [1]. This multilevel cervical spondylosis. It permits adequate decom- procedure allowed decompression, while the retained lam- pression of the cervical spinal cord and is safe and easily inae provided support and prevented invasion of the postla- performed. Potential adverse outcomes after cervical lami- minectomy membrane. Hirabayashi et al. reported on the nectomy include instability and epidural scar formation. It open-door laminoplasty in 1981 [2]. Following this publi- has been hypothesized that this scar may be responsible cation, various modifications have been developed that for persistent postoperative cervical and head pain after sur- are purported to improve the safety and effectiveness of gery and even neurologic deterioration. Fear of instability the procedure. 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 non- union or construct failure, and it reduces motion in the Goals of laminoplasty cervical spine. Laminoplasty was developed to widen the spinal canal The main goal of laminoplasty is to provide decompres- dimensions without permanently removing the dorsal ele- sion of the spinal cord by widening the spinal canal while ments of the cervical spine. The retained dorsal elements preventing instability after decompression (ie, development should aid in the prevention of muscle scarring to the dura of kyphosis) and scar in-growth with potential neurological (ie, result in less cervical and head pain after surgery) and deterioration after surgery. The development of postsurgical cervical kyphosis is well described [3–5], especially in chil- FDA device/drug status: approved but not for this indication (mini- dren [6]. The risk has been shown to be reduced with lateral plates). mass fixation [7], and theoretically with laminoplasty, al- Author DKR acknowledges a financial relationship (consultant with though some loss of lordosis is often seen. Medtronic) that may indirectly relate to the subject of this research. The maximum region of canal expansion is on the open * Corresponding author. Dept. of Neurological Surgery, University of Wisconsin School of Medicine, K4/834 Clinical Science Center, 600 High- side in hinge-type procedures and in the midline in bilateral land Ave., Madison, WI 53792. Tel.: (608) 263-9651; fax: (608) 263-1728. hinge operations. Migration of the cord away from the ven- E-mail address: [email protected] (D.K. Resnick) tral vertebral bodies has been documented in both varieties

1529-9430/06/$ – see front matter Ó 2006 Elsevier Inc. All rights reserved. doi:10.1016/j.spinee.2006.04.023 M.P. Steinmetz and D.K. Resnick / The Spine Journal 6 (2006) 274S–281S 275S 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 sub- stantial 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].

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 Limitations and contraindications cut in the laminae with a high-speed drill. Note the dotted line of the proposed cut. 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 Z-Plasty contraindicated in kyphotic cervical pathology. It is possi- This technique was originally described by Oyama et al. ble to perform laminoplasty in a straightened spine, but [1]. In this procedure, the spinous processes are first re- a lordotic posture is preferred. As noted above, most studies moved and the laminae thinned. They are thinned out to document loss of cervical lordosis after surgery. Lamino- the laminae–facet junction. Troughs are performed later- plasty is generally not indicated for one- or two-level dis- ally. At this point a ‘‘Z’’ is cut into the thinned laminae ease. The limited length of decompression in such cases (Fig. 1). This may be performed with a high-speed drill generally does not allow the free migration of the spinal and diamond drill bit or a fine Kerrison punch. After the cord away from the ventral elements. ‘‘Z’’ cut, the thinned sections of laminae may then be sep- arated 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 Hirabayashi laminoplasty have been described. They are all similar in that they expand the cervical canal and preserve some or all of the Hirabayashi and colleagues described the expansive posterior elements. Modiﬁcations on where the cuts in open-door laminoplasty [2]. In this technique, the spinous the lamina or spinous processes are made and how the ca- processes and laminae are exposed from C2–C7. The supra- nal is kept open have been developed. Newer techniques, spinous and interspinous ligaments are preserved and not such as the use of ceramic spacers and titanium mini- injured. In the authors’ experience, the ligaments must be plates have been proposed, which may decrease the surgi- cut between C2 and C3 and C7 and T1, depending on cal time and improve the safety of the procedure. No one which levels are to be expanded. This aids in ‘‘opening procedure has proven to be more effective than any other the door’’. Using a high-speed drill, a trough is created in terms of neurological outcome, cervical alignment, or on the ‘‘open’’ side at the junction between the laminae ROM. and the facets (Fig. 3). The trough is drilled down to the 276S M.P. Steinmetz and D.K. Resnick / The Spine Journal 6 (2006) 274S–281S

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 in- effective open-door laminoplasty.

expand the opening with a Penﬁeld dissector or curette Fig. 2. After the cuts, the laminae are spread apart and held with wires or while an assistant gently rotates the laminae towards the suture, effectively widening the canal. 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 ligamentum ﬂavum. One may drill all the way through the in a spinal cord injury. The door may be kept open by plac- laminae or one may leave a very thin remnant of laminae, ing suture through the facet capsule on the closed side and especially at its cranial aspect. This thin rim and associated through the spinous processes (Fig. 6). Many variations on 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. 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 Fig. 3. In the Hirabayashi-type open-door laminoplasty, a trough is ﬁrst be opened. Using a curette between the laminae and lateral mass on the drilled in the laminae. This is done somewhat more medial then the lamina, open side and a Kocher on the spinous processes, the block of laminae lateral mass junction. The cut is taken down to dura. The ligament and any is rotated towards the closed or hinged side. This effectively opens and ex- remaining thinned bone must be removed with a Kerrison punch. pands the spinal canal. M.P. Steinmetz and D.K. Resnick / The Spine Journal 6 (2006) 274S–281S 277S

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.

Fig. 8. An axial computed tomographic scan of a patient 6 months after keeping the door open have been described. These include a Hirabayashi-type open-door laminoplasty. Note the expansion of the spi- the use of titanium mini-plates [30], bone graft (allograft nal canal. and autograft) [31], and ceramic spacers (Figs. 7 and 8).

French door laminoplasty cord in the midline to expand the canal (Fig. 10). The lam- In the open-door expansive laminoplasty, the canal is inae may then be secured in an open position using suture opened on one side and hinged on the other. This essen- through the facet capsules and the laminae. In this original tially created an asymmetric expansion of the canal. In description, the canal is left open. Variations have been de- the French door laminoplasty, the door is opened in the scribed to bridge the gap in the open laminae and recreate midline and thus creates a symmetric opening of the canal the protective arch. Pieces of the resected spinous processes [32]. It must be emphasized that one technique has not be may be secured with wire between the lamina, or ceramic proven superior to the other. Troughs are drilled on each spacers may be used [33]. 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. 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 Fig. 7. The laminae may also be held open with titanium mini-plates. masses. The laminae are only thinned and not cut completely through. 278S M.P. Steinmetz and D.K. Resnick / The Spine Journal 6 (2006) 274S–281S 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. Further- more, 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 Fig. 10. After the completion of the trough cuts, the spinous processes are of the surgical manipulation and dissection around the facet 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 joints [36]. The pain usually begins shortly after surgery, midline and held open, similar to a French door. They may be held open but usually resolves within one year. Some advocate early with suture or small bone grafts. postoperative cervical mobilization [36]. Nonsteroidal anti-inflammatory medications and cervical stretching and strengthening exercises may also be effective, but this has Kurokawa modification not been proven. Neurological complications are theoretically less after In this modification of the French door laminoplasty, the laminoplasty compared with laminectomy [36]. This is dorsal aspect of the spinous processes is removed and used likely a result of the need not to put any instruments under as grafts [34]. The spinous processes/laminae are cut in the the lamina on top of the spinal cord. Nerve root palsy has midline using a high-speed drill. The spinous process is been reported to occur after laminoplasty. Similar to any split open and held open with bone grafts that are wired dorsal decompressive operation, nerves may be injured by in place. mechanical injury during dissection for removal of bone (ie, drill or punch). Isolated nerve root palsy may occurs af- Tomita modification ter laminoplasty, but has also been reported after laminec- In this modification, the spinous process/laminae are tomy [37–39]. It is predominantly a motor weakness, less split with a wire-saw. This has been termed the T-saw lam- so sensory changes. It affects C5 greater than other cervical inoplasty [35]. 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 Postoperative management [38]. The authors studied this injury in relation to the type Some controversy exists in regard to the appropriate of laminoplasty performed. Interestingly, there was a greater amount of time for postoperative immobilization. The se- prevalence in those procedures that included foraminotomy nior author encourages early mobilization and does not em- or facetectomy (or both) compared with those that did not ploy a collar at all. Early mobilization of the neck followed in this series. The reason for C5 palsy is unknown, but it by neck exercises is encouraged. Other authors have recom- is likely caused by the course of the nerve through its fora- mended hard collar immobilization for 4–8 weeks. Others men and traction on the nerve as the cord migrates dorsally recommend more limited cervical immobilization, with [37–39]. Other series have attributed postoperative C5 wearing of a hard collar for less than 4 weeks [36]. palsy to intraoperative nerve root trauma, to unrecognized preoperative foraminal stenosis as well as to intrinsic changes existing within the spinal cord before surgery. Complications The pain may be controlled with physical therapy and nonsteroidal anti-inflammatory drugs. The motor palsy usu- In general, complications after laminoplasty are similar ally recovers to normal or near normal within 12 months af- to those after laminectomy. Wound complications, such as ter surgery. Foraminotomy and facetectomy have been tried dehiscence or infection, may be somewhat more common in order to prevent this complication; neither has proven M.P. Steinmetz and D.K. Resnick / The Spine Journal 6 (2006) 274S–281S 279S effective. A controlled opening of the ‘‘door’’ may aid in has been reported to range from 2% to 4%, with 0% in the the prevention of this complication. hardware augmentation group. Not all authors measure cervical alignment in a similar manner, and therefore results may not be directly comparable. Outcome Range of motion Neurologic Cervical ROM has been reported to decrease 17–50%, Most authors report outcome based on the Japanese Or- with an average of approximately 50% after laminoplasty. thopedic Association scoring system. Reported results in- [2,10–25]. When laminoplasty is augmented with fusion, clude mean preoperative and postoperative scores for all ROM was decreased 70–80% [27]. The clinical relevance patients, and a calculated rate of recovery is provided. of this decreased ROM is controversial. Some authors have The mean recovery rate after the Hirabayashi expansive noted the beneficial nature of this decreased ROM. The de- laminoplasty is approximately 60% [10,12– creased ROM has been noted to limit dynamic factors 14,16,17,21,24,26,29,40–43]. Herkowitz studied anterior which are thought to contribute to myelopathy [16].It arthrodesis, laminectomy, and laminoplasty for the man- may also aid in the prevention of OPLL progression [25]. agement of multilevel cervical spondylosis [26]. The author Other authors have noted a benefit to the maintenance of concluded that anterior cervical arthrodesis was superior, cervical ROM. It is thought that this improved ROM de- but laminoplasty was a useful alternative. Herkowitz also creases axial neck pain after laminoplasty and prevents adja- reported on the Hirabayashi type laminoplasty with unilat- cent segment cervical disease [30]. In long-term follow-up eral foraminotomy on the open-door side; the reported rate studies, there is a clear trend towards a decrease in cervical of recovery was 90% [44]. Other authors have reported ROM. Seichi et al. reported a significant rate of spontaneous a mean improvement of 56% with Baba and Tomita’s mod- facet fusion in their patients whom they monitored for at least ification of the Hirabayashi laminoplasty [10,45]. Overall, 10 years after laminoplasty [22]. the majority of patients reported some neurological improvement. In the French door laminoplasty and its modifications, Long-term outcome the mean recovery rate is approximately 50% [18, 22,23,25,35]. Similar results have been reported in the A few studies have reported long-term outcome after lam- hardware assisted laminoplasty literature [30,46]. In gen- inoplasty. Miyazaki et al. observed that improved neurologic eral, the overall recovery rate is reported to range from status was maintained at a mean of 12 years after surgery 50% to 70%. The range of recovery is likely related to [27]. Kawai et al. reported 10-year follow-up after Z-type the degree of preoperative myelopathy and not the specific laminoplasty. Patients with CSM were stable after surgery, surgical procedure. As previously noted, no one surgical whereas those with OPLL demonstrated some late deteriora- technique has proved more effective than another. tion [15]. Similarly, Seichi et al. documented lasting benefit Laminoplasty has been used for the treatment of cervical after laminoplasty for patients with CSM, while only 20% spondylotic myelopathy (CSM) and ossification of the pos- of those patients operated upon for OPLL demonstrated late terior longitudinal ligament (OPLL). In some series, pa- worsening [22]. It appears that OPLL may progress despite tients with CSM had better recovery compared with laminoplasty. In general, improvement after laminoplasty is OPLL [15], whereas in others, a better recovery was re- stable, even up to 10 years after surgery. ported with CSM. Outcome is more likely related to preoperative neurologic status and not the disease process or surgical procedure. Comparison with laminectomy or fusion

Cervical alignment Few authors have directly compared laminoplasty with laminectomy with or without fusion. Kaminsky et al. com- In general, no specific laminoplasty technique has been pared two similar groups of patients treated with lamino- able to prevent the development of some degree of kyphosis plasty or laminectomy for CSM [49]. Using the modified after surgery. Moreover, no laminoplasty technique is effec- Nurick grading scale, they noted similar rates of improve- tive for the restoration of lordosis in an already kyphotic ment between both groups; however, the laminoplasty spine. The range of worsening spinal alignment, not neces- group had a lower incidence of cervical pain. Measures sarily kyphosis, has been reported to range from 22% to of neck stiffness were similar between both groups, and 53% [11,15–17,24,42,43,47]. This loss of lordosis is not ROM was decreased in the laminoplasty patients. 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