Spinal Posterior Movement After Posterior Cervical Decompression Surgery: Clinical Findings and Factors Affecting Postoperative Functional Recovery

■ Feature Article

GANG XIA, MD; RONG TIAN, MD; TIANTONG XU, MD; HUIMING LI, MD; XUELI ZHANG, MD

abstract Full article available online at ORTHOSuperSite.com. Search: 0000020111021-03

This study investigated the posterior movement of the spinal cord after posterior decompression surgery and evaluated factors affecting postoperative functional recovery in patients with cervical spondylotic myelopathy (CSM). Thirty-two patients with CSM underwent posterior decompression from C3 to C7 through laminectomy (nϭ12) and single, open-door laminoplasty (nϭ20). There were no signifi cant differences between laminectomy and laminoplasty in degree of spinal posterior movement, recovery rate, A and curvature index. Japanese Orthopedic Association (JOA) scores improved from preoperative (10.63Ϯ1.77; range, 7-14) to 3-months postoperative (13.57Ϯ1.50; range, 11-16) (nϭ32, PϽ.05) and from preoperative (10.24Ϯ1.87; range, 7-14) to 6-months postoperative (14.16Ϯ1.54; range, 12-16) (nϭ21) (PϽ.05). C5 palsy was observed in 1 (3.1%) patient. The vertebral body-to-spinal cord distances signifi cantly increased after operations, with the greatest posterior movement at C5 and the least posterior movement at C3 and C7. However, the difference in the degree of the spinal movement of C3 to C7 was not statistically signifi cant (PϾ.05). Furthermore, no correlation was found between the magnitude of spinal posterior movement and the curvature index. In addition, the magnitude of posterior movement and age were not correlated with the postoperative JOA improvement, but the preoperative JOA scores were. B Our study shows that both laminectomy and laminoplasty can produce a similar de- Figure: Pre- (A) and postoperative (B) radiographs gree of posterior movement of the spinal cord. Cervical lordosis is not associated with of the cervical spine of patients who underwent laminectomy. the posterior movement of the cord. The preoperative JOA scores, but not posterior movement of the cord and age, are important determinants for postoperative outcome.

Drs Xia, Tian, Xu, Li, and Zhang are from the Department of Orthopedics, Tianjin Union Medical Center, Tianjin, China. Drs Xia, Tian, Xu, Li, and Zhang have no relevant ﬁ nancial relationships to disclose. The authors thank Dr. Xinlong Ma for helpful discussion, and Dr. Jun Yang from Department of Radiology for technical assistance with radiological measurement. Correspondence should be addressed to: Gang Xia, MD, Department of Orthopedics, Tianjin Union Medical Center, 190 Jieyuan Rd, Tianjin 300121, China ([email protected]). doi: 10.3928/01477447-20111021-03

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ervical spondylotic myelopathy (CSM) is a common degenerative Cdisease that affects the elderly. Narrowing of the spinal canal with age leads to compression of the spinal cord, which can cause a variety of symptoms, including pain, numbness, and weakness. Surgery is often required to widen the spinal canal to release the compression of the spinal cord, especially when the clinical symptoms are severe and progressive and 1A 1B when the conservative treatment, such as acupuncture, physical therapy, and various traction methods, as well as analge- sic medications and neuromodulating medications, is not effective in relieving the pain and other symptoms.1-3 Posterior decompression surgery, including laminectomy and laminoplasty, has been used in clinics to allow the spinal cord to move backward to keep it clear of anterior com- 3,4 pression. 1C 1D However, the mechanism of the pos- Figure 1: Plain radiographs of the cervical spine of patients who underwent laminectomy (A, B) and lami- terior movement of the spinal cord post- noplsty (C, D) preoperatively (A, C) and 3 months postoperatively (B, D). operatively remains unclear. The posterior movement of spinal cord is hypothesized to result from the bowstring effect with an MATERIALS AND METHODS SURGICAL TECHNIQUE increased tension in the spinal cord after Thirty-two patients (22 men and 10 We performed a laminectomy or single, the posterior decompression surgery wid- women) who underwent laminectomy open-door laminoplasty. Laminoplasty ens the spinal canal.5-7 The spinal cord (n=12) and single, open-door laminoplas- was preferred by the surgeons, but lami- (bowstring) moves backward by itself in ty (n=20) at C3-C7 were included in this nectomy was performed in patients with response to the change of cervical lordosis study. The average age at operation was severe spinal stenosis, a broken hinge (bow) after the posterior decompression 51 years (range, 29-73 years). All patients during laminoplasty, or a thin and frag- surgery. However, the feasibility of the presented with symptoms of neural com- ile lamina that is diffi cult to use to form bowstring effect of the spinal cord has not pression, and magnetic resonance imag- a hinge. been clearly demonstrated. ing (MRI) fi ndings were consistent with The patient was placed in a prone posi- In addition, the clinical signifi cance CSM. tion on an operating table. A midline ap- of posterior movement of the spinal This study selected patients with CSM proach was made to expose the spinous cord after posterior decompression who had progressive neurological symp- process. For laminectomies, lateral gutters surgery remains controversial. Some toms, alterations of bladder function, and were created at the medial margin of bilat- studies have reported that the degree of multilevel cervical involvement. Patients eral intervertebral joints, and the C3-C7 posterior movement is associated with with spinal cord injuries due to acute trau- lamina were then taken out by removing the postoperative outcome,8,9 whereas matic injuries, ossifi cation of the posterior the outer cortex, cancellous bone, and in- others have reported that the degree longitudinal ligament, and tumors were ner cortex. The posterior wall of the spinal of movement is not.4 We performed excluded. All patients underwent plain canal was completely removed by this sur- laminectomy and laminoplasty on 32 radiographs and MRIs preoperatively and gery (Figure 1A, B). For single, open-door patients with cervical spondylotic my- were followed-up 3 months postoperative- laminoplasty, lateral gutters were created elopathy to investigate the posterior ly. The MRIs and plain radiographs for all at the medial margin of the bilateral inter- movement of the spinal cord and its as- patients were also performed at 3 months vertebral joints. The gutter on the lateral sociated postoperative outcome. postoperatviely during the follow-up. margin of the lamina was completed fi rst

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3A 4A

2B Figure 2: The enlargement and expansion of the spinal cord during laminectomy (A) after the lamina was removed, and during laminoplasty (B) after the lamina door was opened. on the open side to remove the outer cor- 4B tex, cancellous bone, and inner cortex. On Figure 4: The measurement of cervical curvature the hinge side, the inner cortex and part of index in a diagram (A) and in a sagittal MRI (B). the cancellous bone remained. The lamina door was opened by carefully moving the 3B lamina on the open side laterally toward the the TE was 112 ms and the TR was 4500 Figure 3: The measurement of the distance from hinge side. The lamina was ﬁ xed to the sur- the posterior surface of the vertebral body to the ms. In the sagittal plane, the ﬁ eld of view rounding ligament and muscle, and bones anterior surface of the spinal cord on sagittal mag- was 28 cm, and the slice thickness was trimmed from spinous processes were netic resonance images preoperatively (A) and 3 set at 3 mm with a spacing of 0.5 mm. grafted into the hinges to secure the expan- months postoperatively (B). To estimate the magnitude of posterior sion of the spinal canal (Figure 1C, D). movement of the spinal cord, the distance During the posterior decompression preoperative score)/(17–preoperative from the posterior surface of the vertebral surgery, the enlargement and expansion score)ϫ100%. The patients were catego- body to the anterior surface of the spinal of the spinal cord was observed after the rized into 2 groups according to the recov- cord (vertebral body-to-spinal cord dis- lamina was removed for laminectomy ery rate: an excellent group with recovery tance) was measured using T1-weighted (Figure 2A) and after the lamina door was rate у33% and a fair group with recovery sagittal MRIs (Figure 3). The degree of opened for laminoplasty (Figure 2B). rate р33%. postoperative posterior movement of the The MRI study was produced by a spinal cord was calculated by the differ- Evaluation 1.5-T MRI device (Philips, Best, The ence between the pre- and postoperative For each patient, neurologic functions Netherlands). T1-weighted images were vertebral body-to-spinal cord distances. were evaluated pre- and postoperatively captured by the spin-echo method in To quantify postoperative cervical lordo- according to the Japanese Orthopedic which the echo time (TE) was 12 ms, and sis, a cervical curvature index was cal- Association (JOA). The recovery rate the repetition time (TR) was 500 ms. T2- culated using postoperative MRI (Figure was calculated according to the equation: weighted images were captured by the 4) according to the equation: curvature recovery rate=(postoperative score– fast spin echo sequence method in which index=100ϫ(a1ϩa2ϩa3ϩa4)/A.

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Statistical Analysis The values were presented as means Table 1 and standard deviations. Student’s t test Surgical Outcome of Laminectomy and Laminoplasty and analysis of variance (ANOVA) were at 3 Months Postoperatively used for comparison of the difference in the means. A paired t test was used (MeanϮSD) to assess the statistical signiﬁ cance be- Preoperative Curvature Posterior tween pre- and postoperative JOA scores. Parameter JOA Scores Recovery Rate Index Movement, mm Pearson correlation analysis was applied Laminectomy 10.42Ϯ1.38 45.18%Ϯ12.34% 13.18Ϯ6.90 1.55Ϯ1.37 to assess the relationship between the Laminoplasty 10.75Ϯ2.00 54.39%Ϯ14.25% 16.33Ϯ12.76 1.58Ϯ0.79 magnitude of the posterior movement Abbreviations: JOA, Japanese Orthopedic Association; SD, standard deviation. and the curvature index. A P value Ͻ.05 Pу.05, laminectomy vs laminoplasty using Student’s t test. was considered statistically signiﬁ cant. Analyses were performed using SPSS ver- sion 17.0 software (SPSS, Inc, Chicago, Table 2 Illinois). Posterior Movement of the Spinal Cord in a Patient with C5 Palsya

RESULTS Parameter Preoperative, mm Postoperative, mm Posterior Movement, mm C3-C7 laminectomy was performed C3 3.0 4.8 1.8 in 12 patients, and C3-C7 single, open- C4 3.4 6.8 3.4 door laminoplasty was performed in 20 C5 3.3 7.6 4.3 patients. No signifi cant differences were C6 5.4 8.4 3.3 observed between laminectomy and lami- C7 4.3 5.4 1.1 noplasty in preoperative JOA scores, re- aCalculated by the difference between the preoperative and postoperative vertebral body- covery rate, curvature index, and the de- to-spinal cord distances. gree of posterior movement of the spinal cord (Table 1). Therefore, we grouped all 32 patients to analyze the pre- and postop- 32 patients. The C5 palsy developed fi rst gree of the spinal movement at C3-C7 was erative differences. on the open side at 2 weeks after single, not statistically signifi cant between each In the 32 patients followed-up at open-door laminoplasty and was present spinal level (ANOVA, PϾ.05). 3-months postoperatively, the JOA scores on the hinge side at 4 weeks postopera- The frequency of occurrence of maxi- improved from 10.63Ϯ1.77 (range, 7-14) tively. The posterior movement of spinal mum posterior movement was 37.5% (12 preoperatively to 13.57Ϯ1.50 (range, cord at C3-C7 is listed in Table 2. The C5 patients) at C5, 25% at C4 and C6, 12.5% 11-16) postoperatively (PϽ.05). The im- palsy did not heal with time and conser- at C3, and 0% at C7 (Table 4). The postop- proving rate of JOA scores ranged from vative treatment. The patient was treated erative curvature index was 15.15Ϯ10.91, 33.33% to 80.00% (average, 50.93%). with anterior C5 corpectomy surgery 3.5 with a range of –4.23 to 47.25. No correla- Only 21 patients were followed-up at months after laminoplasty and recovered tion was observed between the magnitude 6-months postoperatively, and the JOA at 6 months postoperatively. of posterior movement and the curvature scores for these patients improved from The average postoperative posterior index (r=0.2396, PϾ.05). 10.24Ϯ1.87 (range, 7-14) preoperatively movement of the cervical spinal cord was We further evaluated the potential ef- to 14.16Ϯ1.54 (range, 12-16) postop- 1.6Ϯ1.0 mm (range, 0.3-4.9 mm). We fects of posterior movement of the cord eratively (PϽ.05). The improvement measured the distance from the posterior after laminectomy and laminoplasty on rate of JOA scores ranged from 42.86% surface of the vertebral body to the ante- postoperative outcomes. We divided our to 85.71% (average, 60.58%). The JOA rior surface of the spinal cord at C3-C7 patients into 2 groups based on the recov- scores at 6 months postoperatively sig- (Table 3). A signifi cant increase occurred ery rate: an excellent group including pa- nifi cantly improved compared with those in the postoperative posterior movement tients at the top 33% of recovery rate, and at 3 months postoperatively (PϽ.05), in- of the spinal cord at each level (PϽ.001), a fair group including patients at the bot- dicating a better functional recovery at 6 with the greatest posterior movement at tom 33% of recovery rate. The recovery months postoperatively. C5 and the least posterior movement at rate is often used to evaluate the postop- C5 palsy was observed in 1 (3.1%) of C3-C7. However, the difference in the de- erative outcome in many studies.10-12

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Our study confi rms the posterior spi- Table 3 nal cord movement in 32 patients who Distance from the Posterior Surface of the Vertebral Body underwent laminectomy and lamino- to the Anterior Surface of the Spinal Cord plasty. Unlike laminectomy to remove Pre- and Postoperativelya the posterior structure of the spinal canal, laminoplasty widens and reconstructs the (MeanϮSD) posterior spinal canal structure possibly Posterior restricting the posterior spinal cord move- Parameter Preoperative (X) Postoperative (Y) Movement (Y-X) Pb ment. However, we identifi ed a similar C3 3.5Ϯ1.1 4.6Ϯ1.5 1.2Ϯ1.0 Ͻ.001 degree of posterior movement of spinal C4 3.4Ϯ1.2 5.1Ϯ1.6 1.7Ϯ 0.9 Ͻ.001 cord in patients treated with laminectomy C5 3.5Ϯ1.4 5.5Ϯ1.9 1.9Ϯ1.3 Ͻ.001 and laminoplasty, suggesting that lamino- C6 3.7Ϯ1.4 5.6Ϯ2.1 1.8Ϯ1.5 Ͻ.001 plasty provides enough space for the spinal cord and does not restrict the posterior C7 3.7Ϯ0.9 5.1Ϯ1.6 1.4Ϯ1.3 Ͻ.001 movement of the spinal cord. Abbreviation: SD, standard deviation. aPosterior movement of the spinal cord was calculated by the difference between the Therefore, we believe that lamino- preoperative (x) and postoperative (y) vertebral body-to-spinal cord distances. plasty is the preferred posterior decom- b Paired t test, preoperative vs postoperative. pression method of treatment for CSM because it has been reported to work well 48.73%) (PϾ.05), suggesting that the in the majority of patients and has a low Table 4 spinal cord level of posterior movement risk of adverse effects such as instabil- Frequency of Occurrence is also not associated with postoperative ity,2,13,15,17 which often develops in lami- 18-20 2 of Maximal Posterior function recovery. nectomy. In addition, Kaminsky et al Movement at Each Although younger patients tended to compared 2 similar groups of CSM pa- recover more quickly than elderly patients treated with laminectomy or lami- Spinal Level tients, we did not fi nd a signifi cant cor- noplasty and found a similar improvement Parameter No. % relation between age and postoperative rate between the 2 groups, with fewer late JOA score improvement (PϾ.05) at 3 complications in laminoplasty group. C3 4 12.5 and 6 months postoperatively (Tables 5, Laminectomy is still commonly per- C4 8 25 6). However, we identifi ed a signifi cant formed in China and Japan. Although a C5 12 37.5 correlation between the preoperative trend in cervical spinal surgery has moved C6 8 25 JOA score and postoperative JOA score to replace laminectomy with laminoplasty, C7 0 0 improvement (PϽ.05) at both 3 and 6 laminectomy is still useful as an alterna- Total 32 100 months postoperatively, suggesting that tive in our hospital when the laminoplasty preoperative JOA scores are associated fails due to a broken hinge during an oper- with postoperative prognosis. ation or when a thin or fragile lamina that We found no correlation between is not easily formed into a hinge is pres- the degree of posterior movement and DISCUSSION ent. In addition, laminectomy is preferred the recovery rate at both 3 months and Clinically, posterior decompression to perform on patients with severe spinal 6 months postoperatively (Tables 5, 6), surgery, such as laminectomy and lami- stenosis, which causes a severe compres- suggesting that the degree of posterior noplasty, has been used to treat CSM sion on the spinal cord or nerve root. movement is not a good indicator for patients and can result in satisfactory out- If the patients show no signs of spinal postoperative function recovery. In addi- comes.2,13-16 Posterior movement of the instability preoperatively, we prefer to per- tion, the improvement rate of JOA scores cervical spinal cord after posterior decom- form laminectomy without fusion to prevent of patients with maximum posterior pression surgery is one of the most impor- the potential risks associated with fusion, movement at C5 (nϭ12; range, 33.33%- tant factors for achieving satisfactory de- such as the injury of the spinal cord and 75%; average, 52.36%) is not signifi - compression and is the major mechanism nerve root and improper fusion of the bone, cantly different from that of patients of the posterior decompression surgery as well as the risks of bleeding and infection with maximum posterior movement at to release the anterior compression in pa- associated with the site on the body from C3 (nϭ4; range, 33.33%-60%; average, tients with CSM.3,4 which the bone for grafting is taken.

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It is hypothesized that the posterior movement of the spinal cord is caused by a Table 5 so-called bowstring effect, which suggests Surgical Results and Factors Affecting Outcome that the spinal cord moves backward and at 3 Months Postoperatively elongates by itself after posterior decompression surgery, acting like the bowstring (MeanϮSD) after removal of the external force.5-7 Excellent Recovery Fair Recovery The bowstring effect is largely based Parameter Groupa (n=10) Groupb (n=10) Pc on the assumption that the physiological Posterior movement, mm 1.56Ϯ0.96 2.04Ϯ1.41 Ͼ.05 cervical lordosis (bow) determines the de- Age, y 46.4Ϯ10.4 56.2Ϯ11.6 Ͼ.05 gree of posterior movement of the spinal Preoperative JOA score 11.9Ϯ1.37 9.9Ϯ1.20 Ͻ.05 cord (bowstring). With the bow spreading Abbreviations: JOA, Japanese Orthopedic Association; SD, standard deviation. (the cervical lordosis changing), the bow- aTop 33% (n=10), with recovery rate у60%. string (spinal cord) is gradually tensed to bBottom 33% (n=10), with recovery rate р40%. cStudent’s t test, excellent recovery vs fair recovery. move backward.7 Our ﬁ nding that the posterior movement of the spinal cord is the greatest at C5 and is the least at C3 and C7 agrees Table 6 with the bowstring effect, which hypoth- Surgical Results and Factors Affecting Outcome esizes that the greatest movement in the at 6 Months Postoperativelya middle of the cervical spine is due to the lordosis of the spinal cord.6 According (MeanϮSD) to the bowstring effect, the cervical spi- Excellent Recovery Fair Recovery nal cord moves greatest at the point of Parameter Groupa (n=7) Groupb (n=7) Pc maximum concavity, when the spinal cord Posterior movement, mm 1.55Ϯ0.94 1.44Ϯ0.88 Ͼ.05 spreads under tension.6 Age, y 48.14Ϯ10.31 54.43Ϯ9.20 Ͼ.05 However, our study shows that the Preoperative JOA score 11.14Ϯ1.57 9.0Ϯ1.15 Ͻ.05 magnitude of posterior movement is not correlated with cervical curvature in- Abbreviations: JOA, Japanese Orthopedic Association; SD, standard deviation. aTop 33% (n=7) with recovery rate у75%. dex, suggesting that cervical lordosis is bBottom 33% (n=7) with recovery rate р50%. not necessary for the posterior move- cStudent’s t test, excellent recovery vs fair recovery. ment. In addition, the degree of posterior movement between C3-C7 was not sig- niﬁ cantly different. The maximum poste- exact mechanism of how the posterior right position) and MRI (supine position) rior movement occurs only 37.5% at C5. movement occurs after posterior decom- may affect spinal cord position,24 leading These facts are not consistent with the pression remains to be determined. to measurement errors. Therefore, the bowstring effect. Therefore, the bowstring Although plain radiography is good same MRI image used for measuring both effect alone is not enough to explain the enough to determine cervical lordosis, spinal posterior movement and cervical posterior movement of the cord. MRI was selected in this study to inves- lordosis is best suitable for our purpose of If the spinal cord does not move back- tigate the correlation between the magni- studying the relationship between spinal ward like a bowstring, other stressors have tude of posterior movement and cervical posterior movement and cervical lordosis. to force it to move backward. One pos- lordosis. Magnetic resonance imaging has The incidence of C5 palsy after cer- sibility is that the spinal cord is dragged an advantage over upright plain radiogra- vical spinal surgery ranges from 0% to backward by the denticulate ligament. It phy because it can show clear images on 23%.7,25,26 Sasai et al25 reported that none is well documented that posterior decom- both the spinal cord and the vertebrate of their 74 patients experienced C5 palsy pression surgery will lead to enlargement body, which are critical for measurement after laminoplasty. The incidence of C5 of the spinal cord (Figure 2),6,21-23 which of spinal posterior movement. If upright palsy in our study (3.1%) is in the lower may stretch the dural sac and cause the radiography images are used for measur- range of the reported incidence. The large backward shift of the spinal cord through ing cervical lordosis, the different patient variation in the incidence of C5 palsy re- the denticulate ligament. However, the posture between radiography images (up- mains unknown, possibly because many

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factors contribute to the etiology of C5 quickly, suggesting that preoperative JOA segmental cervical spondylotic myelopathy? Spine (Phila Pa 1976). 2005; 30(21):2414- palsy, such as C5 nerve injury during op- scores are associated with postoperative 2419. 27 eration and tethering of the nerve by spi- prognosis. 5. Epstein JA. The surgical management of nal posterior movement.7,9,28 Despite its sound results, this study cervical spinal stenosis, spondylosis, and Some studies reported that tethering of has some limitations. The spinal poste- myeloradiculopathy by means of the posterior approach. Spine (Phila Pa 1976). 1988; the nerve root might cause the develop- rior movement was only measured at 3 13(7):864-869. ment of C5 palsy as a result of posterior months postoperatively. An MRI taken 6. Aita I, Hayashi K, Wadano Y, et al. Posterior movement of the spinal cord after poste- earlier than 3 months postoperatively may movement and enlargement of the spinal cord rior decompression.7,9,28 Yamashita et al28 lead to erroneous outcome due to postop- after cervical laminoplasty. J Bone Joint Surg Br. 1998; 80(1):33-37. reported that patients with C5 palsy had erative swelling. However, we are not sure 7. Liu T, Zou W, Han Y, et al. Correlative study signifi cantly greater posterior movements whether the degree of posterior movement of nerve root palsy and cervical posterior of the cord than those without C5 palsy. will change over a longer period of time, decompression laminectomy and internal fi xation. Orthopedics. 2010; 33(8). doi: The extent of posterior movement was such as 6 months or 1 year. A study of the 10.3928/01477447-20100625-08 greatest at the C5 level, with an average posterior movement of the spinal cord 8. Baba H, Uchida K, Maezawa Y, et al. movement of 5 mm at the C4 or C5 level. with time is worth further investigation. Lordotic alignment and posterior migration In agreement with their study, our study We also observed the enlargement of the of the spinal cord following en bloc open- door laminoplasty for cervical myelopathy: a showed that the posterior movement in the spinal cord postoperatively. The spinal magnetic resonance imaging study. J Neurol. patient with C5 palsy was 4.3 mm, which cord enlargement may stretch the dural 1996; 243(9):626-632. is greater than the average (1.9 mm). sac, causing the backward shift of the 9. Sodeyama T, Goto S, Mochizuki M, et However, Sodeyama et al9 reported spinal cord through denticulate ligament. al. Effect of decompression enlargement laminoplasty for posterior shifting of the that no correlation existed between the However, we did not make any attempt spinal cord. Spine (Phila Pa 1976). 1999; incidence of C5 palsy and the degree of to study the change in the morphology in 24(15):1527-1531. posterior movement of the cord. The dif- detail. Therefore, the correlation between 10. Yamazaki T, Yanaka K, Sato H, et al. Cervical spondylotic myelopathy: surgical results and ference among these studies is likely due the enlargement and posterior movement factors affecting outcome with special refer- to an insuffi cient number of cases with C5 is a potential area for future study. ence to age differences. Neurosurgery. 2003; palsy (1 case in our study, 3 cases reported 52(1):122-126. by Yamashits et al,28 and 4 cases reported CONCLUSION 11. Fujiwara K, Yonenobu K, Ebara S, et al. The 9 prognosis of surgery for cervical compres- by Sodeyama et al ). The degree of posterior movement of sion myelopathy. An analysis of the fac- Although posterior decompression sur- spinal cord is similar between laminoplas- tors involved. J Bone Joint Surg Br. 1989; gery has been reported to produce satisfac- ty and laminectomy and is not correlated 71(3):393-398. tory postoperative outcomes,2,13-15 some with cervical lordosis. The outcomes of 12. Papadopoulos CA, Katonis P, Papagelopoulos PJ, et al. Surgical decompression for cervical controversies regarding the prognostic posterior decompression surgery are not spondylotic myelopathy: correlation between factors still exist. It is well documented correlated with the degree of spinal poste- operative outcomes and MRI of the spinal that postoperative outcomes are affected rior movement. Preoperative JOA scores cord. Orthopedics. 2004; 27(10):1087-1091. by various factors, such as age, preop- are an important determinant for postop- 13. Sakaura H, Hosono N, Mukai Y, et al. Long- term outcome of laminoplasty for cervical erative JOA scores, symptom duration, erative outcomes. myelopathy due to disc herniation: a com- transverse area of the spinal cord at maxi- parative study of laminoplasty and anterior spinal fusion. Spine (Phila Pa 1976). 2005; mum compression, and signal change on REFERENCES 30(7):756-759. 10-12,29-31 MRI scan. However, few studies 1. Tracy JA, Bartleson JD. Cervical spondylotic 14. Herkowitz HN. A comparison of anterior cer- have reported the correlation between the myelopathy. Neurologist. 2010; 16(3):176- vical fusion, cervical laminectomy, and cervi- 187. postoperative outcomes and the degree of cal laminoplasty for the surgical management 2. Kaminsky SB, Clark CR, Traynelis VC. of multiple level spondylotic radiculopathy. posterior movement of the spinal cord af- Operative treatment of cervical spondylotic Spine (Phila Pa 1976). 1988; 13(7):774-780. ter laminectomy and laminoplasty. In the myelopathy and radiculopathy. 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Is posterior spinal cord shifting by extensive posterior de- 32(4):416-420. preoperative JOA scores recovered more compression clinically signifi cant for multi-

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17. Wang MY, Shah S, Green BA. Clinical out- Spinal cord expansion after decompression thy. Spine (Phila Pa 1976). 1994; 19(5):507- comes following cervical laminoplasty for in cervical myelopathy. Investigation by 510. 204 patients with cervical spondylotic my- computed tomography myelography and ul- 28. Yamashita TYK, Yokozawa H, et al. C5 elopathy. Surg Neurol. 2004; 62(6):487-492. trasonography. Spine (Phila Pa 1976). 1995; nerve palsy after cervical laminoplasty: an 20(15):1657-1663. 18. Kaptain GJ, Simmons NE, Replogle RE, et analysis of three cases. Seikei Geka. 1996; al. Incidence and outcome of kyphotic de- 23. Fujimura Y, Nishi Y, Nakamura M. Dorsal 47(12):1365-1369. formity following laminectomy for cervical shift and expansion of the spinal cord after 29. Ahn JS, Lee JK, Kim BK. Prognostic factors spondylotic myelopathy. J Neurosurg. 2000; expansive open-door laminoplasty. J Spinal that affect the surgical outcome of the lami- 93(2 Suppl):199-204. Disord. 1997; 10(4):282-287. noplasty in cervical spondylotic myelopathy. 19. Mikawa Y, Shikata J, Yamamuro T. Spinal 24. Ranger MR, Irwin GJ, Bunbury KM, et al. Clin Orthop Surg. 2010; 2(2):98-104. deformity and instability after multilevel cer- Changing body position alters the location 30. Chen CJ, Lyu RK, Lee ST, et al. vical laminectomy. Spine (Phila Pa 1976). of the spinal cord within the vertebral canal: Intramedullary high signal intensity on T2- 1987; 12(1):6-11. a magnetic resonance imaging study. Br J weighted MR images in cervical spondy- Anaesth. 2008; 101(6):804-809. 20. Sim FH, Svien HJ, Bickel WH, et al. Swan- lotic myelopathy: prediction of prognosis neck deformity following extensive cervical 25. Sasai K, Saito T, Akagi S, et al. Preventing with type of intensity. Radiology. 2001; laminectomy. A review of twenty-one cases. C5 palsy after laminoplasty. Spine (Phila Pa 221(3):789-794. J Bone Joint Surg Am. 1974; 56(3):564-580. 1976). 2003; 28(17):1972-1977. 31. Hamburger C, Buttner A, Uhl E. The cross- 21. Takahashi Y, Narusawa K, Shimizu K, et 26. Sakaura H, Hosono N, Mukai Y, et al. C5 pal- sectional area of the cervical spinal canal in al. Enlargement of cervical spinal cord cor- sy after decompression surgery for cervical patients with cervical spondylotic myelopa- relates with improvement of motor function myelopathy: review of the literature. Spine thy. Correlation of preoperative and postop- in upper extremities after laminoplasty for (Phila Pa 1976). 2003; 28(21):2447-2451. erative area with clinical symptoms. Spine J Spinal Disord Tech (Phila Pa 1976). cervical myelopathy. . 27. Satomi K, Nishu Y, Kohno T, et al. Long-term 1997; 22(17):1990-1994. 2006; 19(3):194-198. follow-up studies of open-door expansive 22. Matsuyama Y, Kawakami N, Mimatsu K. laminoplasty for cervical stenotic myelopa-

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