Revision Surgery Following Cervical Laminoplasty Etiology and Treatment Strategies

Revision Surgery Following Cervical Laminoplasty Etiology and Treatment Strategies Gabriel Liu, MD, Jacob M. Buchowski, MD, MS, Torphong Bunmaprasert, MD, Jin S. Yeom, MD, Hongxing Shen, MD, and K. Daniel Riew, MD SPINE Volume 34, Number 25, pp 2760 2768 2009, Lippincott Williams & Wilkins Study Design. Retrospective review of prospectively collected data. Objective. To identify the cause of failed open-door laminoplasty and to describe the surgical strategies for revision surgery. Summary of Background Data. Although laminoplasty has become popular, few articles have addressed the cause of failed cervical laminoplasty requiring revision surgery. Methods. All patients who required revision surgery following open-door cervical laminoplasty were identified. Clinical data, method of surgical revision, time between surgeries, Nurick grade, radiologic parameters, and complications were analyzed. Laminoplasty failures were classified into 3 categories: technique related, inadequate symptomatic relief after treatment, or recurrence of symptoms due to disease progression. Results. A total of 130 patients underwent cervical laminoplasty over a 10-year period (1996 2006), and 12 patients (9.2%) required revision surgery. The mean age was 50.7 years at the time of the index laminoplasty (range, 34 67 years) and 51.8 years (range, 35 70 years) at the time of the revision surgery. Mean duration of symptoms was 7.3 months before the index procedure (range, 2 17 months) and 5.6 months (range, 1 14 months) before revision surgery. The mean time interval between the index procedure and revision surgery was 16.6 months (range, 4 43 months). Of the 12 patients who required revision surgery, 5 had global lordosis of 10, 4 developed local kyphosis 13, and 5 had increased degenerative spondylolisthesis. Nonmyelopathic causes resulted in 50% of the revision surgery. Of 12 patients, 3 (25%) required revision surgery due to technique-related factors; 1 (8%) required surgery due to inadequate symptomatic relief after treatment; and 8 (67%) required revision surgery due to disease progression. Conclusion. Of the 130 patients who underwent cervical laminoplasty over a 10-year period, 12 patients (9.2%) required revision surgery. Although laminoplasty is generally successful, failures due to disease progression, technique-related factors, and inadequate symptomatic relief after treatment can occur. Patients should, therefore, be counseled regarding the potential need for revision surgery when undergoing open-door laminoplasty. Key words: laminoplasty, laminectomy, complications, revision surgery. Spine 2009;34:2760 2768 From the Department of Orthopaedic Surgery, Washington University in St. Louis, St. Louis, MO. Acknowledgment date: February 17, 2009. Acceptance date: April 26, 2009. The device(s)/drug(s) is/are FDA-approved or approved by corresponding national agency for this indication. No funds were received in support of this work. One or more if the author(s) has received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this manuscript e.g., royalties, stocks, stock options, decision making position). Address correspondence and reprint requests to Jacob M. Buchowski, MD, MS, Department of Orthopaedic Surgery, Washington University in St. Louis, 660 S. Euclid Ave., Campus Box 8233, St. Louis, MO 63110; E-mail: buchowskij@wustl.edu Since Hirabayashi et al 1 first reported the result of opendoor laminoplasty in 1977, the technique has become one of the most common procedures for the treatment of cervical myelopathy, 2 and has become the treatment of choice for myelopathic diseases involving 3 or more levels. 3 8 Laminoplasty is commonly used to manage cervical myelopathy resulting from spondylotic disease 9 13 and ossification of the posterior longitudinal ligament (OPLL). 1,14 16 Cervical laminoplasty avoids surgical morbidity 3,17 24 and graft-related complications 3,7,22,25 28 associated with anterior cervical surgery, and preserves cervical motion. 29,30 The procedure offers the advantage of direct decompression of the neural elements by increasing the spinal canal volume, 1 as well as, indirect decompression by allowing the spinal cord to drift dorsally away from retrodiscal and/or retrovertebral disease. 5,31 35 In addition, the reshaped laminae keep the postlaminectomy membrane or scar from compressing the spinal cord 4,8,36,37 and protect the spinal cord against future traumatic injury. 38 The reported neurologic recovery rates 10 years following laminoplasty range from 50% to 72%. 10,12,36,39 Despite these advantages, there are drawbacks to the procedure, including postoperative axial symptoms/pain, 12,13,36,39,40 reduced range of motion (ROM), 9,12,36,39 and C5 motor palsy. 1,12,13,36,39 Although these complications have been extensively studied, few reports have addressed revision surgery after cervical laminoplasty. The purpose of this study was to determine the cause of failed opendoor laminoplasty and to describe the surgical strategy necessary to address this difficult problem. To the best of the authors knowledge, the current study is the only study focusing on revision surgery after open-door laminoplasty. Materials and Methods A retrospective review of all patients who underwent opendoor cervical laminoplasty by the senior author over a 10-year period (1996 2006) was performed by independent spine surgeons uninvolved in the patients care. Patients who required revision surgery were identified. Patient clinical data were recorded with attention to patient age, duration of symptoms, neurologic deficits, and surgical indications for laminoplasty. Reasons for revision surgery, the surgical technique used, time interval between surgeries, and revisions were examined. Patient neurologic status was described according to the Nurick grade 41 for myelopathy before laminoplasty, following laminoplasty, before revision surgery, and following revision surgery. Laminoplasty failures were classified into those that were technique related, those with inadequate symptomatic relief after treatment, and recurrence of symptoms due to disease progression (Table 1). 2760

Revision Surgery Following Cervical Laminoplasty Liu et al 2761 Table 1. Etiology of Laminoplasty Failure Requiring Revision Surgery Etiologies of Postlaminoplasty Revision Surgery Technique Related Inadequate Treatment Disease Progression (New Early Onset Postoperative Symptoms) (Residual Preoperative Symptoms) (New Late Onset Postoperative Symptoms) Inherent to laminoplasty procedure Foraminal stenosis Within laminoplasty levels (1) Axial symptoms* (intractable neck pain) Large anterior cord compression ( 7 mm thick OPLL, (1) Spondylosis (2) C5 motor paresis* osteophyte, disc or 50% compression) (2) OPLL (mixed and continuous type) (3) Late closure with re-stenosis in laminoplasty without instrumentation S-shaped or 10 global 13 local kyphotic preoperative spinal alignment Adjacent segment diseases (1) Facet arthrosis or spacer Intractable preoperative neck pain (2) Herniated disc (4) Postlaminoplasty Global kyphosis Spinal instability* (3) Osteophytic/spondylotic (central or Surgical skill (1) Cord compression from lamina subsidence (2) After laminoplasty hinge fracture foraminal stenosis) (4) Junctional kyphosis (5) OPLL *Controversial whether early revision surgery is warranted. In addition to clinical analyses, all pre- and postoperative plain radiographs were examined and cervical alignment was assessed. More specifically, the C2 C7 angle between the tangential lines on the posterior wall of the C2 and C7 vertebral bodies on the lateral radiograph in a neutral position was measured as described by Penning. 42 Cervical ROM was determined by measuring the difference of the C2 C7 angles on lateral flexion and extension radiographs. 42 Ishihara s cervical curvature index, 30 Chiba s longitudinal distance index (LDI), 32 and Toyama s classification of cervical alignment 32 were measured before the index laminoplasty and before revision surgery. Finally, any other radiographic abnormalities such as cervical spondylolisthesis or magnetic resonance imaging (MRI), computed tomography, and/or myelogram findings that might have contributed to the reason for revision surgery, were recorded. Results Over the 10-year period, 130 patients underwent a cervical laminoplasty by the senior author. Of these 130 patients, 12 patients (9.2%) required revision surgery; 9 were men and 3 were women, and the mean age at the time of the initial surgery (i.e., laminoplasty) was 50.7 years (range, 34 67 years). The mean age at the time of the revision surgery was 51.8 years (range, 35 70 years) (Table 2). The mean duration of symptoms prior the initial procedure and subsequent revision surgery was 7.3 months (range, 2 17 months) and 5.6 months (range, 1 14 months), respectively. The mean period of time between the initial procedure and revision surgery was 16.6 months (range, 4 43 months). The mean Nurick grades before and after the index laminoplasty were 2.5 (range, 0 5) and 1.0 (range, 0 4), respectively. The mean Nurick grades before and after the revision surgery were 1.3 (range, 0 5) and 0.9 (range, 0 5), respectively. The mean patient follow-up period following the index laminoplasty was 39.8 months (range, 5 84 months). Radiographically, 5 of the 12 patients (41.6%) who required revision surgery had cervical lordosis that measured 10 before revision surgery, and 7 of the 12 patients (58.3%) had a nonlordotic spinal alignment according to the Toyama classification before revision surgery (Table 3). Before revision surgery, the Ishihara cervical curvature index, which represents the degree of cervical lordosis, was 8.9 (range, 0 24) and the Chiba LDI, which represents the sagittal distance from C2 to C7, was 4.8 (range, 3.6 5.8). In at least 1 study, a Chiba LDI of 5 was shown to be associated with a higher likelihood of improvement in myelopathic symptoms due to a smaller longitudinal cervical spinal distance that allowed a larger postlaminoplasty dorsal shift of the spinal cord. 7 In the current patient population, 4 of the 12 patients (33.3%) developed local kyphosis 13 before revision surgery. Of the 12 patients, 5 (41.6%) demonstrated increased degenerative segmental spondylolisthesis with the C2 C3, C3 C4, and C6 C7 levels most commonly affected. Revision surgery was required in 6 of the 12 patients (50.0%) due to worsening myelopathic symptoms, whereas in the remaining 6 patients (50.0%) revisions surgery was required due to nonmyelopathic causes (Table 2). Laminoplasty failures were due to techniquerelated factors in 3 patients (25.0%), inadequate symptomatic relief after treatment in 1 patient (8.3%), and disease progression in 8 patients (66.7%). All 3 patients who required revision surgery due to techniquerelated factors had laminoplasty closure during a period of time when suture-anchors were used to hold the hinge open. The patient who had inadequate symptomatic relief after treatment (case 2 illustrated below) had persistent postlaminoplasty radiculopathy due to foraminal stenosis, which resolved after anterior cervical discectomy and fusion (ACDF). The majority of patients who required revisions surgery (8 of 12 patients [66.7%]) did so for disease progression. All 8 patients had improvement or resolution of their presenting symptoms following the index laminoplasty, but subsequently had recur-

2762 Spine Volume 34 Number 25 2009 Table 2. Patient Clinical Data First Revision eration After Laminoplasty Number First Laminoplasty Case at (yr) Dx Pathologies Levels Pre Nurick Grade Post Nurick Grade Duration From First to Second Month Duration Symptom Month Reason for Reoperation (Re) Etiology Classification Pathologies Levels Type of Re- eration Pre Nurick Grade Post Nurick Grade st Comp 1 34 M Cong C3 C7 4 4 5 5 Laminar Tech C6 C7 Laminectomy, 5 5 Pneumonia closure F, C 2 52 M Spon C2 C7 3 0 4 4 Foramen Inad C5 C7 Hybrid Ant. F 0 0 stenosis 3 55 M Spon C3 C6 3 1 10 2 Spondylosis Prog C6 T1 Hybrid Ant. F 0 0 4 34 R Spon C3 C7 0 0 17 14 Spondylosis Prog C4 C7 Hybrid Ant. F 0 0 5 48 M Spon C3 C7 4 1 19 12 Spondylosis Prog C2 T2 Circumferential F 1 0 6 67 M Spon C4 C6 1 0 12 8 Kyphosis Prog C2 C4 Circumferential F 1 1 (junctional) 7 67 M Spon C3 C7 4 1 26 6 Kyphosis Prog C1 C3 Posterior F 1 1 (junctional) 8 58 M OPLL C4 C7 3 0 11 1 PID Prog C4 C5 ACDF 0 0 9 49 R Spon C3 C7 0 0 13 7 Foraminal Prog C3 C5 Post 0 0 stenosis foraminotomy 10 53 M OPLL C3 C7 5 4 5 2 Laminar Tech C3 C7 Laminectomy, F 4 4 closure 11 47 M OPLL C3 C7 1 0 43 3 OPLL Prog C3 C6 Hybrid Ant. F 0 0 C5 palsy 12 45 M Spon C3 C4?? 37 3 Laminar closure Tech C4 C5 Laminectomy, F 3 0 M indicates myleopathy; R, multilevel radiculopathies; Cong, congenital stenosis; Spond, spondylotic stenosis; PID, prolapsed intervertebral disc; Tech, technique related; Inad, inadequate treatment; Prog, disease progression; F, fusion; Post Comp, Post operative complications; pseudo, pseudoarthrosis. Hybrid Ant F anterior cervical fusion with both corpectomy(s) and disectomy(s). Circumferential F or C Anterior and posterior spinal fusion. rence and/or worsening of their symptoms (Table 1). Of the 8 patients, 1 patient had OPLL, whereas the remaining 7 patients had spondylotic disease progression either within or adjacent to the area of the laminoplasty (Table 2) with 3 patients presenting with at least 1 worsening disc osteophyte complex, 2 patients presenting with proximal junctional kyphosis, 1 patient with a new disc herniation, and 1 patient with worsening foraminal stenosis leading to radicular symptoms. Using Kapler- Meyer survival analysis, patients who required revision surgery due to disease progression had a risk of requiring revision surgery of 4% 2.2% 1 year following the index laminoplasty and 21% 7.7% 4 years following the index procedure. Revision surgery varied in approach (anterior vs. posterior vs. anterior/posterior). One patient (8.3%) (case 3) required 2 surgeries after the index laminoplasty due to adjacent level disease progression first at the level immediately caudal to the laminoplasty and then at the level cephalad to the laminoplasty. Two patients (16.7%) underwent a laminectomy and posterior cervical fusion. One patient (8.3%) underwent a laminectomy and an anterior cervical fusion. One patient (8.3%) underwent a posterior cervical fusion without an additional laminectomy. Five patients (41.7%) underwent an ACDF. Finally, 2 patients (16.7%) required a circumferential fusion following the index laminoplasty (Table 3). Spinal instrumentation was used in all revision cases. Although there were no surgical mortalities following revision surgery, 1 patient (8.3%) developed transient C5 motor palsy after anterior cervical surgery and 1 additional patient (8.3%) developed a postoperative pneumonia. Selected Case Examples Case 2. A 52-year-old man, who had a prior ACDF at C3 C4 and C4 C5 performed elsewhere, developed evidence of cervical spondylotic myelopathy due to spinal cord compression extending from C2 C3 to C6 C7. A right hinged open-door laminoplasty from C2 to C7 with bilateral C5 C6 and C6 C7 foraminotomies was performed. Laminoplasty plates and suture anchors were used to prevent laminoplasty closure. Although the patient s myelopathic symptoms resolved at 4 months postoperation, he continued to complaint of residual radicular pain. Plain radiograph showed preservation of lordosis in the upper cervical segments and no worsening of the preoperative segmental kyphosis of the lower cervical spine. There were large bilateral uncinate osteophytes from C5 to C7. Radiologic studies confirmed a well-decompressed central canal with residual foraminal stenosis from C4 to C7 (Figure 1). Electromyography revealed no evidence of peripheral neuropathy. Given evidence of persistent foraminal stenosis, a C5 subtotal corpectomy (anterior cervical corpectomy and fusion [ACCF]) and ACDF at C6 C7 with structural allograft and cervical plating from C4 to C7 were then performed. Following surgery, the patient had immediate improvement in his symptoms and at 2 years following the revision surgery he was asymptomatic and had a solid fusion anterior cervical fusion from C4 to C7.

Revision Surgery Following Cervical Laminoplasty Liu et al 2763 Table 3. Patient Radiographic Data Prefirst Laminoplasty Prefirst Revision eration After Initial Laminoplasty Case C2 C7 Angle Number (Degree) ROM Ishihara (Degree) Index Toyama Classification Longitudinal Distance Index Remarks C2 C7 Angle (Degree) ROM Ishihara Index Toyama Classification Longitudinal Distance Index Remarks 1 19 L 44 26 L 4.5 30 L 40 22 L 3.6 C6 C7 2 mm 2 8 K 7 0 S 5.5 5 K 12 0 K 5.5 C2 C3 3 mm 3 9 L 28 4 St 3.7 C3 C4 2 mm retro 7 K 43 3 St 4.8 C3 C4 0 mm retro C4 C5 2 L C4 C5 10 K C6 C7 10 K C6 C7 20 K 4 0 19 0 St 4.3 C4 C5 0 2 L 32 0 St 4.8 C4 C5 4 K C6 C7 2 L C6 C7 0 5 30 L 64 15 L 4.3 28 L 57 24 L 4.7 C6 C7 2 mm 6 12 L 39 13 S 5.1 C2 C3 4 mm 15 L 20 3 S 5.1 C2 C3 4 mm C2 C4 23 K C2 C4 24 K 7 6 L 32 0 St 4.4 C2 C3 2 mm 28 K 30 0 K 5.2 C2 C3 4 mm C2 C3 5 L C2 C3 3 K C2 C4 0 C2 C4 14 K 8 18 L 38 13 L 4.8 C4 C5 3 mm retro 10 L 25 6 St 4.9 C4 C5 0 mm retro 9 31 L 52 27 L 5.5 20 L 31 14 L 5.8 10 28 L 58 17 L 4 C2 C7 scoliosis 28 L 31 21 L 4.3 C3 C4 3.5 mm 11????? 23 L 40 14 L 3.8 12????? 7 K 17 0 K 5 C4 C5 15 K K indicates Kyphosis; L, lordosis; S, S shape spine; St, Straight spine; ROM, range of cervical spine motion;?, represent missing data; reto, retrolisthesis;, anterolisthesis. Ishara Index measure the amount of cervical lordosis. Toyama classification classified cervical alignment into: lordotic, kyphotic, straight spine and S-shaped spine. Longitudinal distance index measure sagittal distance (ratio) from C2 to C7. Case 3. A 55-year-old man who was wheelchair-bound after multiple bilateral lower extremity reconstructive surgeries for arthrogryposis multiplex congenita had become myelopathic and unable to lift himself out of the wheelchair. MRI showed multiple cervical disc herniations from C3 to C6 with cervical spondylotic myelopathy. In view of the minimal axial symptom and the importance in preserving his cervical mobility needed to navigate his wheelchair, a left hinged open-door laminoplasty from C3 to C6 with bilateral foraminotomies was performed using suture anchors to hold open the Figure 1. Case 2: The T2 axial MRI showed a wide opened central spinal canal as indicated by the spinous process position and a narrow arrow indicating residual foraminal stenosis after the laminoplasty had been performed at C4 C5 and C6 C7 spinal levels. laminoplasty. After surgery, his myelopathic symptoms resolved. Ten months after the index procedure, he developed new left-sided radicular pain and numbness along his shoulder, elbow, and ulnar 2 digits. Radiographic studies showed significant disc degeneration, facet arthropathy, and kyphosis from C6 to T1 and, to a lesser extent from C4 to C5. To address the pathology below the laminoplasty, a subtotal C7 ACCF with a structural allograft and cervical plate was performed. Subsequent pain relief was achieved for another year, but unfortunately, approximately 1 year later, the patient had return of bilateral radicular symptoms as a result of foraminal stenosis from C3 to C6. A subtotal C4 ACCF and ACDF at C5 C6 was then performed using a structural allograft and plating (Figure 2) with relief of his symptoms. Approximately 13 months following the last surgery, the patient remains symptom free. Case 7. A 67-year-old woman became quadriplegic after she tripped and fell at home. Despite a significant improvement in her neurologic status, she remained disabled due to inability to work with her hands and severe difficulty with balance. Radiologic studies showed a lordotic cervical spine with spondylotic spinal canal stenosis from C3 to C7 with spinal cord signal change on MRI. A right hinged open-door laminoplasty from C3 to

2764 Spine Volume 34 Number 25 2009 Figure 2. Case 3. A, Shows a prelaminoplasty lateral cervical spine radiograph. B, Shows open-door laminoplasty held opened by suture anchors. Spondylotic disease progression at C6-T1 adjacent to the laminoplasty levels. C, Spondylotic progression requiring C7 ACCF. D, Showed subsequent spondylotic progression requiring C3 C6 spinal fusions. C7 with bilateral foraminotomies was performed approximately 4 months following the fall using laminoplasty plates to hold open the laminoplasty. Normal neurologic function returned 3 months following surgery. Following surgery, the patient developed mild global kyphotic cervical spinal alignment. Two years following her index surgery, patient s myelopathic symptoms returned as the kyphosis worsened especially at the cephalad portion of the laminoplasty. Imaging studies showed cord compression and spinal stenosis from a pannus behind C1, C2, and C3 with severe facet arthrosis at C2 C3, a congenitally narrowed C1 arch with C1 C2 anterior subluxation and autofusion from C4 to C7. There was no closure of the laminoplasty. Given the degree of spinal stenosis, a posterior spinal fusion from C1 to C5 with instrumentation was performed 26 months after the index procedure. Following the revision surgery, the patient has done well with steady gradual improvement in her neurologic function (Figure 3). Case 10. A 53-year-old woman with Down syndrome developed rapidly worsening myelopathic symptoms

Revision Surgery Following Cervical Laminoplasty Liu et al 2765 Figure 3. Case 7. A, Prelaminoplasty lateral cervical spinal alignment. B, Kyphotic spinal alignment across the proximal junction of the operated laminoplasty levels. C, C1 C2 spinal cord compression by pannus at C1 C2 with cervical kyphosis. No cord compression was seen at laminoplasty spinal segments. D, Restoration of cervical alignment after C1 C5 posterior spinal instrumentation and fusion. and bladder incontinence due to spinal cord compression from C3 to C7 due to OPLL. A right hinged open-door laminoplasty from C3 to C7 was performed using suture anchors. Following temporary improvement in her symptoms, the myelopathic symptoms returned due to closure of the laminoplasty 3 months after surgery (Figure 4). Given the closure of the laminoplasty, an instrumented posterior spinal fusion and laminectomy from C3 to C7 was performed. A halo-vest was used temporarily following surgery. Following the revision surgery, there was no further neurologic deterioration. Discussion Laminoplasty is a safe and effective treatment for symptomatic cervical myelopathy with a relatively low complication rate. 2,13,30,43 Surgical revision rates following laminoplasty are also low, ranging from 0% to 8%, 5 to 10 years following surgery. 9,10,12,36,38 40,44 The findings in the current study mirror the historical revision rates: in the current study, 12 of 130 patients (9.2%) who underwent laminoplasty required revision surgery. More specifically, 3 patients (25.0%) required revision surgery Figure 4. Case 10. The narrow arrow points out the closure of the laminoplasty with spinal cord recompression by OPLL and lamina; the broad arrow demonstrates the position of the suture anchor used to keep the laminoplasty opened. due to technique-related factors, 1 patient (8.3%) required revision surgery due to inadequate symptomatic relief after treatment, and 8 patients (66.7%) required revision surgery due to recurrence and/or worsening of symptoms due to disease progression. Of the 8 patients who required revision surgery, 1 patient had OPLL, whereas the remaining 7 patients had progression of spondylotic disease progression either within or adjacent to the area of the laminoplasty with 3 patients presenting with at least 1 worsening disc osteophyte complex, 2 patients presenting with proximal junctional kyphosis, 1 patient with a new disc herniation, and 1 patient with worsening foraminal stenosis leading to radicular symptoms. Technique-related factors that lead to the need for revision surgery may be divided into those that are inherent to the nature of the procedure and into those that are related to the manner in which the procedure is performed (Table 1). Factors that are inherent to the nature of the procedure include postoperative axial symptoms 12,13,36,39,40 and C5 motor palsy. 1,12,13,36,39,40 Postlaminoplasty axial symptoms may have significant effects on the quality of patients lives 40,45 as can C5 palsy; however, the decision whether revision surgery ought to be performed is often controversial due to the uncertainty of the origin of axial neck pain and usually selflimiting nature of the C5 palsy. Technique-related factors that are related to the manner in which the procedure was performed include laminoplasty closure, which is not uncommon complication following laminoplasty. 8,10,46 At least 2 authors have described cases where laminectomy following laminoplasty had to be performed to relieve spinal cord compression resulting from a fractured laminoplasty hinge with intrusion of the lamina into the canal. 8,46 Satomi et al reported laminoplasty closure after open-door laminoplasties with hydroxyapatite spacers in 3 patients who then required revision laminectomy. 10 In the current study, 3 patients (25%) had closure of laminoplasty (cases 1, 10, and 12), and all 3 had their laminoplasty held open by suture anchors. No laminoplasty closures were observed in patients when laminoplasty plates were used. Although the use of suture anchors (as opposed to laminoplasty plates) was likely a principal cause of failure in

2766 Spine Volume 34 Number 25 2009 these patients, poor head control likely was a contributing factor as 2 of the 3 patients had unreliable head control due to cerebral palsy in 1 patient (case 1) and Down syndrome in 1 patient (case 10). Poor laminoplasty results have been reported in patients with uncontrolled head movement secondary to athetoid cerebral palsy. 38,47 In the current study, all 3 patients were treated successfully with laminectomy, fusion, and instrumentation. Furthermore, since application of laminoplasty plates has become a standard part of our procedure (as opposed to using suture anchors), no laminoplasty closures have been observed and the majority of patients who require repeat surgery do so due to disease progression (Table 1). In the current study, 1 patient (8.3%) required revision surgery because the preoperative symptoms persisted following the procedure. Inadequate symptomatic relief after treatment can be due to a variety of causes which are listed in Table 1. To ensure an adequate dorsal shift of the spinal cord to achieve a maximum relief of myelopathy, laminoplasty is contraindicated in a kyphotic spine. 1,3 8,34,48 Poor neurologic recovery after laminoplasty in cervical spine with 10 global kyphosis, 48,49 13 local segmental kyphosis, 50 or S-shaped spine 9 have been reported. Other factors that lead to unsatisfactory results in the treatment of myelopathy include a large retrovertebral or osteodiscogenic anterior spinal cord compression. Yamazaki et al 48 reported poor postlaminoplasty result in patients with OPLL thicker than 7 mm or 50% spinal canal intrusion. Patients with intractable preoperative neck pain from cervical spondylosis 3,4,6 or spinal instability, 51 53 where spinal decompression with fusion instead of motion preserving laminoplasty should be considered. en-door laminoplasty with foraminotomies appears to be a satisfactory treatment for myeloradiculopathic cervical disease as reflected by the lack of revision surgery required to treat any nonresolving postlaminoplasty symptoms in this study. However, inadequate posterior decompression from significant foraminal stenosis requiring further anterior decompression may still occur as seen in case 2. In this study, 8 of the 12 patients (66.7%) who required revision surgery did so due to progression of degenerative cervical pathology (cases 3 9, 11) demonstrated by recurrence of symptoms after a postlaminoplasty symptom-free period. These include progression of OPLL (1 of 12 patients [8.4%]), worsening spondylosis (7 of 12 patients [58.3%]), and/or worsening cervical alignment (2 of 12 patients [16.7%]). Progression of OPLL after the treatment of cervical laminoplasty has been observed. 1,14,15,34 Kawaguchi et al, in a study of 45 patients, reported that 73% of patients with OPLL had worsening of OPLL 10 years following open-door cervical laminoplasty and 3 of the 45 patients (6.7%) had late neurologic deterioration with spinal cord compromise due to postoperative worsening of OPLL. 15 The authors found that young patients 53 8.6 years of age with mixed and continuous types of OPLL had the greatest risk of progression. The authors hypothesized that the reasons for progression may be related to biologic stimulation and alteration of the mechanical and microcirculatory environment in the spinal canal after surgery. 14 An example of disease progression can be seen in case 11, where the patient suffered from disabling occipitocervical headaches and neck pain due to foraminal stenosis and OPLL progression. His symptoms resolved after anterior cervical decompression and fusion. Disease progression secondary to worsening spondylosis was observed in 7 of 12 patients (58.3%) (cases 3 9). Although it is not known what exactly is the specific cause of the spondylotic changes seen with disease progression, such as facet arthrosis, disc degeneration, and/or disc herniation, the observed changes may be induced by postsurgical change in spinal biomechanics, as part of the ongoing aging deterioration, or both. Interestingly, the majority of patients (4 of 7 patients [57.2%]) with worsening spondylosis, had the greatest extent of disease progression at the segments immediately cephalad or caudal to the laminoplasty (cases 3, 5 7). Although laminoplasty is a motion preserving procedure and may, therefore, theoretically lower the risk of adjacent segment degeneration 54 commonly seen in anterior cervical fusion surgery, 22,55,56 the ROM following laminoplasty does decrease over time. 9,10,12,13,36,38,39,44,46 Seichi et al found that 11 of the 35 patients (32%) had no cervical ROM at 13-year followup. 38 In addition to a decrease in motion over time, C2 C3 auto-spinal fusion had been noted to occur in up to 79% of patients 38,57 and up to 80% of patients will have reduced lordotic alignments at C2 C3 and C6 C7 junctions after a C3 C7 laminoplasty at 3-years follow-up. 58 With these changes, the local spinal biomechanics are undoubtedly altered, and it is therefore not entirely surprising that spinal segments adjacent to the laminoplasty (cases 3, 5 7) as well as those at the end of the laminoplasty (case 8) would be at risk for future deterioration. Another disease progression-related cause is the worsening of postlaminoplasty cervical alignment seen in 2 of the 12 patients (16.7%). The reported incidence of postlaminoplasty cervical kyphosis ranges from 0% to 22%. 9,12,13,36,38,44,59 Poor postoperative neurologic recovery, 9 and late neurologic deterioration 36 in patients with postlaminoplasty cervical kyphosis had been reported. Paraspinal muscle damage from the laminoplasty procedure is believed to be the cause of the postoperative kyphotic spinal alignment. 1,9,36 It is postulated that the detachment of the semispinalis cervicis from its insertion at C2 spinous process leads postlaminoplasty kyphosis. 57,60,61 Development of postlaminoplasty kyphosis combined with adjacent level degeneration accounts for the causes of the proximal junctional kyphosis noted in cases 6 and 7. Surgical strategies for revision procedure after a laminoplasty procedure are similar to the strategies used in the treatment of cervical myelopathy. 3,6,7,29 In this study, neurologic deficits (myelopathy) due to technique-related factors were treated via a posterior cervical approach (cases 1,

Revision Surgery Following Cervical Laminoplasty Liu et al 2767 10, and 12). Symptoms including intractable axial pain and/or radiculopathy due to inadequate symptomatic relief or disease progression were treated via an anterior approach with or without circumferential fusion (cases 2 4, 8, 11). Circumferential fusion was performed in patients with spinal deformity and those deemed at risk for pseudarthrosis or instrumentation failure due to poor neck control after spinal fusion (cases 1, 5, and 6). A limitation of the current study is the small patient sample size and the heterogeneous nature of the patient subgroups requiring repeat surgery after cervical laminoplasty. Revisions following laminoplasties are relatively rare, making a study with a large series of revisions difficult. Without combining the data from several surgeons, it is difficult to produce a much larger series. On the other hand, a multisurgeon retrospective study has inherent problems of its own. We believe that, while small, our series nevertheless helps to define the causes that necessitated revision surgery. While some, such as adjacent level breakdown or progression of OPLL may be difficult or impossible to avoid, others, such as substituting plates for suture anchors can markedly diminish the rate of revision surgery. In summary, revision surgery after cervical laminoplasty is not uncommon: in the current study, 12 of 130 patients (9.2%) required revision surgery over a 10-year period. The reasons for surgical revision may be classified into laminoplasty technique related, inadequate symptomatic relief after treatment, or recurrence of symptoms due to disease progression. Disease progression accounted for the largest group of revised patients (66%) who had a surgical revision risk of 4% 2.2% and 21% 7.7% at 1 and 4 years following laminoplasty. These numbers are comparable to those following fusion operations. One avoidable cause or revision surgery was the use of suture anchors, as none of the plated laminoplasties required revisions for laminar closure. Key Points A retrospective review of 130 patients who underwent cervical laminoplasty over a 10-year period (1996 2006) was performed in order to identify the cause of failed open-door laminoplasty and to describe the surgical strategies for revision surgery. Of the 130 patients who underwent cervical laminoplasty, 12 patients (9.2%) required revision surgery. The mean time interval between the index procedure and revision surgery was 16.6 months (range, 4 43 months). Of 12 patients, 3 (25%) required revision surgery due to laminoplasty closure when suture anchors were used, 1 (8%) required surgery due to inadequate decompression, and 8 (67%) required revisions surgery due to disease progression. Patients with laminoplasty closure were treated using a posterior cervical approach; those with inadequate symptomatic relief after treatment and those with disease progression were treated via an anterior approach; and those with spinal deformity or at risk for nonunion were treated with a circumferential fusion. References 1. Hirabayashi K, Toyama Y, Chiba K. Expansive laminoplasty for myelopathy in ossification of the longitudinal ligament. Clin Orthop Relat Res 1999:35 48. 2. Deutsch H, Mummaneni PV, Rodts GE, et al. Posterior cervical laminoplasty using a new plating system: technical note. J Spinal Disord Tech 2004;17: 317 20. 3. Edwards CC II, Riew KD, Anderson PA, et al. Cervical myelopathy. Current diagnostic and treatment strategies. Spine J 2003;3:68 81. 4. Epstein N. Posterior approaches in the management of cervical spondylosis and ossification of the posterior longitudinal ligament. Surg Neurol 2002; 58:194 207; discussion 207 8. 5. Kawakami M, Tamaki T, Ando M, et al. 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