Clinical Application of a New Plate Fixation System in Open-Door Laminoplasty

■ Feature Article

Clinical Application of a New Plate Fixation System in Open-door Laminoplasty

LIANGJUN JIANG, MD; WEISHAN CHEN, MD; QIXIN CHEN, MD; KAN XU, MD; QIONGHUA WU, MD; FANGCAI LI, MD

abstract Full article available online at ORTHOSuperSite.com. Search: 20120123-07

The purpose of this retrospective clinical series was to evaluate the benefi ts and complications of plate fi xation for open-door laminoplasty in cervical spondylotic myelopathy with multilevel spinal stenosis compared with open-door laminoplasty without fi xation. Forty-nine patients underwent open-door laminoplasty for cervical myelopathy with multilevel spinal stenosis with at least 13 months of follow-up. A A B plate was used as the sole method of fi xation between the lateral mass and lamina Figure: One-week postoperative anteroposterior with 3 screws. Computed tomography scans obtained pre- and postoperatively were (A) and lateral (B) radiographs of a patient with assessed for plate complications and spinal canal enlargement. Pre- and postoperative cervical spondylotic myelopathy with multilevel neurological condition was assessed by the Japanese Orthopedic Association (JOA) spinal stenosis who received plate open-door laminoplasty. We performed C3-C7 segment open-door myelopathy score. Overall cervical spine range of motion (ROM) was measured in full laminoplasty with 5 centerpiece plates. Each plate fl exion and extension radiographs pre- and postoperatively. was fi xed to the spinous lamina and the lateral mass by 3 mini-screws. No restenosis due to door reclosure was noted, and no plates failed. No screws were backed out or broken. Almost all patients showed neurological improvement. The JOA score increased by 3.9Ϯ0.7 points in the suture group and 4.3Ϯ0.8 points in the plate group (PϾ.05). The postoperative increase in mean anteroposterior diameter of the spinal canal from C3 to C7 was 4.5Ϯ0.6 mm in the suture group and 5.1Ϯ0.5 mm in the plate group. The greater mean anteroposterior diameter increase in the plate group was statistically signifi cant (PϽ.01). The mean cervical ROM decreased in the plate and suture groups postoperatively (PϽ.001). No signifi cant difference was found in mean cervical ROM reduction between the groups (PϾ.05). No difference in axial symptoms was found between the 2 groups.

Drs Jiang, Chen (Weishan), Chen (Qixin), Xu, Wu, and Li are from the Department of Orthopaedics, The 2nd Affi liated Hospital of Zhejiang University, Hangzhou, Zhejiang, China. Drs Jiang, Chen (Weishan), Chen (Qixin), Xu, Wu, and Li have no relevant fi nancial relationships to disclose. Correspondence should be addressed to: Liangjun Jiang, MD, Department of Orthopaedics, The 2nd Affi liated Hospital of Zhejiang University, Jiefang Rd #88, Hangzhou, Zhejiang, China (abacus0610@ yahoo.com.cn). doi: 10.3928/01477447-20120123-07

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ultisegmental cervical spondylotic myelopathy remains a Table 1 Mpathophysiological and thera- Patient Demographics peutic challenge. Expansive laminoplasty has gradually become a preferred proce- Average age 58 (41-81) dure for almost all patients with cervical (range), y spondylotic myelopathy with multilevel No. of 40:21 spinal stenosis. Hirabayashi et al1 intro- men:women duced unilateral open-door laminoplasty, No. of patients in 38 the plate group 1A 1B which has been widely used worldwide. In the classic open-door laminoplasty tech- No. of patients in 23 Figure 1: One-week postoperative anteroposterior the suture group (A) and lateral (B) radiographs of a patient with nique, the lamina door is tethered open Levels of decompression, no. cervical spondylotic myelopathy with multilevel via sutures through the spinous process spinal stenosis who received plate open-door lami- 3 9 (C3-C5) and facet capsule or paravertebral muscle, noplasty. We performed C3-C7 segment open-door ϭ which are then tied to prevent reclosure of 4 14 (C4-C7 7; laminoplasty with 5 centerpiece plates. Each plate C3-C6ϭ7) was fi xed to the spinous lamina and the lateral the lifted lamina. 5 38 (C3-C7) mass by 3 mini-screws. Although this technique has proven to be successful, its limitations include inad- Plates used, no. equate decompression on the hinge side, 26group, 6 patients used 2 plates, 27 patients the potential for reclosing of the door, 327used 3 plates, 3 patients used 4 plates, and 2 range of motion (ROM) restriction, and 43patients used 5 plates (Table 1). lack of a truly stable fusion.2-4 Therefore, 52 a few fi xations, such as sutures, bone SURGICAL TECHNIQUE struts, ceramic blocks, and suture anchors, Modifi cations were made to the origi- were used in the open-door laminoplasty, MATERIALS AND METHODS nal Hirabayashi et al1 laminoplasty in our but all of them were defi cient in some Between January 2008 and January surgical technique. A standard posterior way. Sutures may cut out, break, or stretch 2011, a total of 61 consecutive patients exposure of the cervical spine was per- over time. Bone struts and ceramic blocks with cervical spondylotic myelopathy with formed. The number of segments operated have the potential for graft kickout. Suture multilevel spinal stenosis were assessed in on depended on the pattern of spinal cord anchors may displace, and the suture may our study. All patients met the following en- compression. Two hinges at bilateral junc- cut out or break. rollment criteria: (1) a clear history of pro- tions of the bilateral lateral mass and bone Recently, a new plate fi xation sys- gressive neurological defi cit; and (2) com- lamina were created by completely remov- tem was developed for open-door lami- parable radiography, magnetic resonance ing the dorsal cortex and thinning the ven- noplasty that fi xes the free lamina and imaging (MRI), and computed tomography tral cortex with an electric drill. The ventral lateral mass. Rhee et al5 reported that a (CT) fi ndings verifying multilevel cervical cortex in the open side was removed. In the plate in open-door laminoplasty could stenosis with or without ossifi cation of the plate group, the open side was stabilized maintain stable spinal canal expansion posterior longitudinal ligaments. Patients with plates and mini-screws (Centerpiece; with high rates of hinge union. However, with serious systemic disease, such as acute Medtronic Sofamor Danek, Memphis, information is lacking about the benefi ts cardiac accident or cerebral infarction, were Tennessee). Commonly, we chose the left and complications of the plate. Since excluded. Mean patient age at surgery was side as the open-door side and the right 2008, we have used the plate system in 58 years (range, 41-81 years). Thirty-eight side as the hinge side. The plate was mea- the open-door laminoplasty in patients patients (24 men, 14 women) underwent sured to suit the space between the lateral with multisegmental cervical spondy- open-door laminoplasty with plate fi xa- mass and lamina, and a suffi cient size (usu- lotic myelopathy in our institution. The tion, and 23 patients (16 men, 7 women) ally model #10-#12) was chosen to allow purpose of this study was to evaluate the underwent open-door laminoplasty with adequate expansion of the spinal canal. benefi ts and complications of plate fi xa- suture. The choice of internal fi xation used Two mini-screws were placed into the lat- tion in open-door laminoplasty for cer- was randomized. Nine patients had 3 lev- eral mass through the plate, and another vical spondylotic myelopathy compared els of decompression (C3-C5), 14 patients mini-screw was placed into the cut lamina with open-door laminoplasty without had 4 levels (C4-C7ϭ7; C3-C6ϭ7), and 38 through the plate to create stable fi xation fi xation. patients had 5 levels (C3-C7). In the plate (Figure 1). In the suture group, the lamina

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Table 2 Follow-up Data

Characteristic Plate Group Suture Group No. of patients at follow-up 32 17 Mean patient age (range), y 56 (41-67) 59 (44-73) No. of men:women 20:12 13:4 Average operative time, min 145 132 Average blood loss, mL 350 345 Average follow-up (range), mo 19 (13-36) 20.5 (14-39)

2 Figure 2: Postoperative sagittal computed tomography scan. We measured the anteroposterior di- ameters of the C3-C7 segments and used the mean anteroposterior diameter ([aϩbϩcϩdϩe]/5) to evaluate the spinal canal expansion of open-door laminoplasty. In this patient, we performed an open-door laminoplasty with C3-C6 segment decompression, and the plates were fi xed in the C4 and C5 segments. 3A 3B Figure 3: The mean Japanese Orthopedic Association (JOA) score increased postoperatively in the plate group (PϽ.05) and the suture group (PϽ.05) (A). The Japanese Orthopedic Association score increase Ͼ door was tethered open via #1 nonabsorb- was not signifi cant between the groups (P .05) (B). able sutures through the spinous process and facet capsule or paravertebral muscle. All patients were allowed to sit up or It was measured in full fl exion and full eratively. The follow-up rate was 80.3%. walk between 3 and 5 days postoperatively. extension radiographs.7 The ROM was Mean patient age in the plate group was 56 A cervical brace was worn for 3 months. measured preoperatively and 6 months years (range, 41-67 years) and in the suture Pre- and postoperative neurological postoperatively to evaluate the change in group was 59 years (range, 44-73 years). condition was assessed by the Japanese the cervical spine. The plate group comprised 20 men and 12 Orthopaedic Association (JOA) myelopa- Results were analyzed statistically women, and the suture group comprised thy score. with paired Student t test using SPSS 17.0 13 men and 4 women. Average follow-up The anteroposterior (AP) diameter of software (SPSS Inc, Chicago, Illinois). was 19 months (range, 13-36 months) in the spinal canal from C3 to C7 was mea- Signifi cance was set at PϽ.05. the plate group and 20.5 months (range, sured on sagittal CT scans preoperatively 14-39 months) in the suture group (Table and 6 months postoperatively. The AP RESULTS 2). No restenosis due to door reclosure was diameter was defi ned as the distance be- The plate group comprised 38 patients, noted, and no plates failed. No screws were tween the middle of the posterior margin and the suture group comprised 23 pa- backed out or broken. of the vertebral body and a line parallel to tients. Operative time averaged 145 min- The JOA score system was used to the posterior margin of the vertebral body utes in plate group compared with 132 evaluate neurological function. Almost all and tangent to the base of the spinous pro- minutes in the suture group (PϽ.05), and patients showed improvement. The mean cess (Figure 2).6 We used the mean AP blood loss averaged 350 mL in the plate JOA score increased from 9.0Ϯ0.7 to diameter of the C3 to C7 spinal canal seg- group compared with 345 mL in the su- 13.3Ϯ0.9 in the plate group (PϽ.05) and ments to evaluate spinal canal expansion. ture group (PϾ.05). from 9.2Ϯ1.0 preoperatively to 13.1Ϯ0.7 The overall cervical spine ROM was Postoperatively, results were investigat- postoperatively in the suture group defi ned as the sum of the Cobb angle ed in 49 patients (32 from the plate group (PϽ.05). This is an increase of 4.3Ϯ0.8 in formed by lines along the inferior end- and 17 from the suture group) who were the plate group and 3.9Ϯ0.7 in the suture plate of C2 to the inferior endplate of C7. observed for at least 13 months postop- group (PϾ.05) (Figure 3).

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Radiographically, no patient had hinge side occurred earlier in the plate mm preoperatively to 16.2Ϯ1.4 mm post- progressive kyphotic deformity postop- group. Mean AP diameter increased from operatively in the suture group (PϽ.001). eratively compared with preoperative 10.8Ϯ1.7 mm to 15.9Ϯ1.6 mm in the This is an increase of 5.1Ϯ0.5 mm in the alignment. Bone fracture healing of the plate group (PϽ.001) and from 11.7Ϯ1.1 plate group and 4.5Ϯ0.6 mm in the suture group. The greater mean AP diameter increase in the plate group was statistically signifi cant (PϽ.01) (Figures 4, 5). Radiographically, mean cervical ROM decreased from 49.6°Ϯ6.9° preoperatively to 40.1°Ϯ4.0° postoperatively in the plate group (PϽ.001) and from 51.3°Ϯ8.1° preoperatively to 41.4°Ϯ5.1° postoperatively in the suture group (PϽ.001) (Figure 6). This is a decrease of 9.2°Ϯ5.3° 4A 4B in the plate group and 8.9°Ϯ4.3° in the su- Figure 4: Mean anteroposterior (AP) diameter increased postoperatively in the plate group (PϽ.001) and the suture group (PϽ.001) (A). The greater postoperative mean anteroposterior (AP) diameter increase ture group. No signifi cant difference was could be seen in the plate group (PϽ.01) (B). found in reduction of mean cervical ROM between the 2 groups (PϾ.05) (Figure 7). Complications included superfi - cial wound infection in 4 patients (plate groupϭ2, suture groupϭ2), transient C5 root palsy in 2 patients (plate groupϭ1, suture groupϭ1), and postoperative car- 5A 5B 5C diopulmonary events in 1 patient (suture groupϭ1). Eighteen patients (plate groupϭ12, suture groupϭ6) had axial pain at last follow-up.

DISCUSSION Unilateral open-door laminoplasty was introduced by Hirabayashi et al.1 Because 5D 5E 5F sutures in the original Hirabayashi et al1 Figure 5: Axial computed tomography scans demonstrating the increase of anteroposterior diameter in a open-door laminoplasty do not provide patient in the suture group (A-C) and a patient in the plate group (D-F). Preoperative (A, D), 1-week postop- enough rigid ﬁ xation, they may cut out, erative (B, E), and 6-month postoperative (C, F) scans. The spinal canal expanded postoperatively. Almost no change occurred in anteroposterior diameter at 1 week compared with 6 months postoperatively in the 2 break, or stretch over time, and the poten- patients. At 6 months postoperatively, the hinge-side ventral bone fracture in the plate group patient showed tial for reclosing of the door always exists. healing (arrows) (F). However, the bone fracture line remained in the suture group patient (arrows) (C).

6A 6B 6C 6D Figure 6: Preoperative full ﬂ exion (A) and full extension (B) and 6-month postoperative full ﬂ exion (C) and full extension (D) lateral radiographs measuring cervical range of motion (range of motionϭaϩb).

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Therefore, many fi xation systems have been developed to replace sutures, such as bone struts, ceramic blocks, and suture anchors. Bone struts and ceramic spacers can keep the position of lamina, and bone healing can occur between the bone struts, lamina, and lateral mass. However, bone struts and ceramic spacers may kick out and lead to door reclosure. A serious clini- 7A 7B cal outcome can result if the bone struts Figure 7: Mean cervical range of motion (ROM) decreased postoperatively in the plate group (PϽ.001) Ͻ or ceramic spacer dislodges into the spi- and the suture group (P .001) (A). Mean cervical range of motion reduction was not statistically signifi - cant between the groups (PϾ.05) (B). nal canal. Recently, suture anchors were used in open-door laminoplasty, and some studies reported excellent clinical results.8 eter increased from 10.8Ϯ1.7 mm preop- logical improvement postoperatively. The However, the suture anchors may displace, eratively to 15.9Ϯ1.6 mm postoperatively ratio of JOA score improvement rates was and the suture may cut out and break. A in the plate group and from 11.7Ϯ1.1 mm 47.8% in the plate group and 42.4% in the new plate fi xation system has been devel- preoperatively to 16.2Ϯ1.4 mm postop- suture group, which is similar to others re- oped in open-door laminoplasty. eratively in the suture group. This is a ported in the literature.14,15 The JOA score In the current study, bone-window CT mean AP diameter increase of 5.1Ϯ0.5 increase was higher in the plate group, but scan was used for measuring the size of mm in the plate group and 4.5Ϯ0.6 mm it was not statistically signifi cant between the spinal canal. Because AP diameter in the suture group, similar to increases the 2 groups. Using a plate in open-door directly infl uences the compression ratio between 5.0 and 5.4 mm reported in other laminoplasty may not contribute to neu- and canal area, we used AP diameter to as- studies.10,11 The mean postoperative AP rological improvement more than using sess canal expansion.6 We used CT scans diameter increased signifi cantly in the 2 sutures would. The greater expansion of to measure the spinal canal AP diameter groups. This indicates the effectiveness the spinal canal in the plate group may not as the evaluation of operative outcome. In of the laminoplasty procedure to expand result in better clinical improvement. patients with multilevel spinal stenosis, the spinal canal. The greater AP diameter Axial symptoms occurred in 18 this method can measure the exact spinal increase was seen in the plate group. The (36.7%) patients (plate groupϭ12, su- canal size of segments C3 to C7. However, plate offered enough strength and good ture groupϭ6). No signifi cant difference the diameter cannot refl ect the real spinal stability to support the lamina, so the ca- existed in the occurrence rate of axial canal size in some special segments with nal diameter could be designed larger in symptoms (37.5% in the plate group vs partial ossifi cation of the posterior longi- the plate group than in the suture group. 35.3% in the suture group) between the tudinal ligament, which is not at the mid- This was the most important advantage 2 groups. The plate offered stronger sup- dle site of the vertebral body. Although of the plate in open-door laminoplasty. port and better stability, but did not re- this diameter is the shortest distance of At follow-up, the AP diameter in the plate duce axial symptoms. First described in the middle site of the vertebral body to the group experienced nearly no change and 1996,16 axial pain is defi ned as pain from spinous process, it is not the narrowest site in the suture group was slightly smaller, the nuchal to the periscapular or shoulder of the spinal canal in patients with ossi- but it was not statistically signifi cant. region. Factors associated with axial pain fi cation of the posterior longitudinal liga- With suture fi xation, premature lami- are unclear. Hosono et al16 reported that ment. In the current study, 27 patients had noplasty closure has been reported at axial symptoms may be caused by several ossifi cation of the posterior longitudinal rates ranging from 1.5% to 34%.12,13 things, including nuchal muscle intraop- ligament; 18 patients and 32 cervical seg- However, during our follow-up, we found erative injury, destruction of facet joints, ments encountered this problem. To avoid no door reclosure in any patient. Rhee et intraoperative nerve root damage, and this error, we used the mean AP diameter al5 reported that the plate could promote hinge side nonunion. The reconstruction to minimize this systemic deviation. hinge-side ventral fracture bone healing. of posterior elements at laminoplasty is Kokubun et al9 reported that patients We found the same phenomenon in some expected to relieve axial symptoms. One with multilevel spinal stenosis with a mean patients in our institution. study reported that neck muscle strength AP diameter р12 mm would have more We measured functional and neurolog- and axial symptoms were strongly cor- chance of developmental canal stenosis. ical outcome with the JOA score. In our related.17 It has also been reported that In the current study, the mean AP diam- series, almost all patients showed neuro- successful reconstruction of the lamina

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of vertebral arches is essential because an open-mouth shape. It can contain the stenosis of cervical spine [in Japanese]. Nihon Seikeigeka Gakkai Zasshi. 1987; sinking or nonunion of the expanded lam- lamina, and the lower part of the mouth 61(5):455-465. 18 ina can induce postoperative axial pain. can offer good support. We usually used 7. Kim SW, Limson MA, Kim SB, et al. Sakaura et al19 reported that the muscles 3 screws to fi x the plate. The plate size Comparison of radiographic changes after at the cervicothoracic junction around the was the #10 or #12 model, and the screws ACDF versus Bryan disc arthroplasty in single and bi-level cases [published online C7 spinous process played a central role were 5 or 7 mm long. Postoperatively, the ahead of print January 6, 2009]. Eur Spine J. in the development of this postoperative patients received cervical brace support 2009; 18(2):218-231. axial pain. Because the C7 spinous pro- for 3 months. Adequate plate size, screw 8. Yu HL, Xiang LB, Liu J, Chen Y, Yu M, Cao Y. Laminoplasty using Twinfi x suture cess is the origin of the trapezius, rhom- length, and cervical brace support was im- anchors to maintain cervical canal expan- boid minor muscles, and nuchal ligament, portant to prevent internal fi xation failure. sion [published online ahead of print May 7, sacrifi cing this spinous process can cause Rigid internal fi xation was critical to the 2010]. Eur Spine J. 2010; 19(10):1795-1798. great damage to the posterior musculature expansion of the spinal canal. 9. Kokubun S, Sato T, Ishii Y, Tanaka Y. Cervical myelopathy in the Japanese. Clin of the cervical spine. In the current study, The advantages of the plate over other Orthop Relat Res. 1996; (323):129-138. the C7 spinous process was retained in 12 forms of laminoplasty fi xation include: (1) 10. Lee SH, Ahn Y, Lee JH. Laser-assisted anteri- patients at follow-up, and axial pain oc- the plate can provide enough strength to or cervical corpectomy versus posterior lami- curred in 2 of them. create immediate hinge stability postopera- noplasty for cervical myelopathic patients with multilevel ossifi cation of the posterior Axial symptoms are strongly corre- tively; (2) contrary to suture fi xation, the longitudinal ligament. Photomed Laser Surg. lated with cervical ROM. Many system- plate can maintain greater expansion of the 2008; 26(2):119-127. atic reviews on neck pain and headache spinal canal and prevent reclosure of the 11. Shaffrey CI, Wiggins GC, Piccirilli CB, Young JN, Lovell LR. Modifi ed open-door lamino- have demonstrated that ROM is the most open door; and (3) plate techniques are plasty for treatment of neurological defi cits in frequently reported objective outcome easier to grasp than some suturing or bone younger patients with congenital spinal steno- measure in published trials.20 In our se- graft techniques. Disadvantages include: sis: analysis of clinical and radiographic data. J Neurosurg. 1999; 90(2 suppl):170-177. ries, mean cervical ROM was decreased (1) increased treatment costs; and (2) when 12. Satomi K, Ogawa J, Ishii Y, Hirabayashi K. in both groups. This may be related to the used in internal fi xation, the possibility ex- Short-term complications and long-term re- axial symptoms. Postoperative reduction ists of internal fi xation failure such as sults of expansive open-door laminoplasty of mean cervical ROM was 9.2°Ϯ5.3° in screw backout and broken plates. for cervical stenotic myelopathy. 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