Postoperative Sagittal Imbalance after Lumbar Fusion Surgery

Transcription

1 Original Article J. of Advanced Spine Surgery Volume 2, Number 1, pp 20~31 Journal of Advanced Spine Surgery JASS Postoperative Sagittal Imbalance after Lumbar Fusion Surgery Jee-Soo Jang, M.D., Sang-Ho Lee, M.D. Department of Neurosurgery, Wooridul Spine Hospital, Seoul, Korea Purpose: There is an increasing recognition of the clinical importance of the sagittal balance after lumbar fusion surgery. The purpose of this study to review the etiology of sagittal imbalance after lumbar fusion surgery and report the radiographic and clinical results of surgical treatment of these patients. Materials and Methods: Retrospective review of revision spine surgery due to sagittal imbalance in 35 patients. Various surgical methods such as posterior anterior posterior (PAP) sequential approach, Smith Peterson osteotomy (SPO), pedicle subtraction osteotomy (PSO), and vertebral column resection (VCR) were performed to restore lumbar lordosis. The outcome variables included preoperative, postoperative, and follow-up radiographic films, and a clinical assessment using Oswestry Disability Index (ODI), SRS 22, and a review of postoperative complications. Results: The mean age of the patients was 62 years (age range, 49 74), and mean follow-up duration was 31 months (range, 24 37) for clinical and radiographic outcome variables. The mean preoperative LL/PI (lumbar lordosis/ pelvic incidence) ratio was different from postoperative value (P< ). Twenty one out of 35 patients showed perioperative complications including proximal junctional kyphosis or infection. All functional outcomes measures improved postoperatively (P < ). Conclusion: Most common causes of revision spine surgery due to sagittal imbalance include failure to enhance lumbar lordosis, proximal vertebral collapse, and junctional kyphosis. LL/PI ratio was considered as one of the valuable spinopelvic parameter for evaluation of sagittal imbalance. Following surgical treatment, sagittal balance was generally improved with good to excellent clinical outcomes and high patient satisfaction, although the perioperative complication rates are high. Key Words: Sagittal imbalance, SPO, PSO and VCR Introduction Imbalance of the spine in the sagittal plane is a clinically important deformity. Its characteristic clinical feature is difficulty during walking and a stooped trunk. Harrington distraction instrumentation is the most common iatrogenic cause of positive sagittal imbalance. 1) Several other procedures can lead to fixed sagittal imbalance. The most common causes and exacerbating factors include failure to enhance regional lordosis during lumbar fusion for degenerative spondylosis, development of pseudoarthrosis or postoperative loss of correction, development of kyphosis at the thoracolumbar junction, development of degeneration and decompensation cephalad or caudad to a prior fusion, and hip flexion contractures. 2-7) The ideal treatment for the resulting sagittal imbalance is restoration of adequate lumbar lordosis (LL) for sagittal balance. 8-11) It is challenging to determine the amount of LL that each patient would require to maintain optimal sagittal balance. Sagittal alignment has been traditionally known Corresponding author: Jee-Soo Jang, M.D. Department of Neurosurgery, Wooridul Spine Hospital, 47-4, Cheongdamdong, Gangnam-gu, Seoul , Korea TEL: , FAX : spinejjs@yahoo.co.kr 20 Copyright 2012 Korean Society for the Advancement of Spine Surgery

2 to be regulated by the maintenance of balance of the reciprocal curves of thoracic kyphosis (TK) and LL; 12) however, recent studies have shown the importance of pelvic morphology and orientation in the regulation of the sagittal alignment ) The relationship between pelvic incidence (PI) and LL has been studied extensively ) PI is the sum of the sacral slope and the pelvic tilting (Fig 1). PI is anatomical constant parameter individually, on the contrary SS and PT are variable positional parameters (Fig 1). In order to plan an optimal surgery to correct sagittal imbalance, it is necessary to predict the postoperative alignment. PI is a constant anatomical value that indicates the sagittal alignment of the spine. Therefore, the amount or extent of LL is dependent on an individual s PI. Thus, for optimal sagittal balance, a patient with a high PI requires more LL than that required by a patient with low PI, and may be vulnerable to any loss of LL ) The various methods currently used to rectify fixed sagittal imbalance include the Smith-Peterson osteotomy (SPO), pedicle subtraction osteotomy (PSO), and vertebral column resection (VCR). 17,18) The recommended surgical treatment depends on the extent of lordosis required by a patient. For the past decade, spinal deformities have been treated successfully with the posterior-anterior-posterior (PAP) sequential approach performed on a single day. 6,19,20) To achieve lordosis with SPO, the posterior column is shortened and the anterior column is lengthened. With PSO, the posterior column is shortened with or without lengthening of the anterior column. 2,5,6,17,21) The VCR achieves balance in the sagittal and coronal planes by shortening the length of the spinal column. 22) We review the etiology of revision surgery due to sagittal imbalance and to evaluate changes in sagittal alignment and pelvic position. We also aim to demonstrate the utility of the PAP sequential approach-spo, Fig. 1. Sagittal pelvic parameters based on standing radiographs. The PI is constant for each person. SS and PT vary depending on the version of the pelvis about the hip axis. Fig. 2. (A) Forced transtable lateral view showed high flexibility. (B) Whole spine lateral view showed severe lumbar kyphosis with sagittal imbalance. (C) ALIF followed by posterior SPO is an adequate surgical method in the patient with high flexibility. 21

3 PSO, and VCR technique-as revision surgery for sagittal imbalance. The efficacy of these techniques in correcting sagittal imbalance can be assessed by radiographic parameters and clinical outcomes. Methods We retrospectively reviewed 35 consecutive patients with iatrogenic fixed sagittal imbalance who underwent treatment with the PAP sequential procedure or combined methods. Before surgery, all patients underwent a careful history and physical examination. Preoperative radiographs consisted of anteroposterior and lateral spine films with dynamic flexion and extension views. To evaluate flexibility, forced transtable lateral views were checked. Evaluation of flexibility is important to choose surgical methods. For example in the patient with high flexibility, ALIF followed by posterior SPO is adequate surgical methods to restore lumbar lordosis (Fig. 2). On the contrary, in the patients with rigid deformity, PSO or VCR should be done to make adequate lordosis (Fig. 3). Long-cassette standing anteroposterior and lateral radiographs were taken preoperatively, 3 months postoperatively, and at the most recent postoperative visit for all the patients. Computed tomograms and magnetic resonance images were obtained from all the patients. For patients who underwent revision surgery, consideration of previous fixation and fusion status was important. Surgical methods Surgery is the mainstay of treatment for patients with sagittal imbalance after lumbar fusion. A suitable surgical approach is selected depending on the flexibility and severity of the deformity. Various surgical procedures such as posterior-anterior-posterior (PAP) sequential approach, the Smith-Petersen osteotomy (SPO), pedicle subtraction osteotomy (PSO), and vertebral column resection (VCR) are performed to restore lumbar lordosis Fig. 3. (A) Forced transtable lateral view showed fixed sagittal imbalance. (B) Whole spine lateral view showed severe sagittal imbalance with T-L kyphosis. (C) PSO or VCR is an adequate surgical method in the patient with rigid deformity. Fig. 4. (A) Whole spine lateral view showed sagittal imbalance with flat back. (B) P-A-P sequential approach is an adequate surgical method to restore lumbar lordosis. 22

4 Table 1. Selection of surgical method ASF cages + SPOs ASF cages + PSO ASF cages + SPOs + PSO ASF cages + SPOs + PSO + VCR Table 2. How many levels? ( L1, 2 or T10) Thoracolumbar junction angle (L2-T10) 1) > 20 kyphosis : T10 2) 0-20 kyphosis: depending on disc, bone and muscle condition 3) Lordosis : L1 or L2 Table 3. Causes of sagittal imbalance inadequte lumbar lorsosis 32 proximal compression fracture 12 proximal junctional kyphosis 7 instrumentation failure 2 Fig. 5. (A) Whole spine lateral view showed severe sagittal imbalance with T-L kyphosis. (B) ALIF with PSO is adequate an adequate surgical method to correct sagittal imbalance. Fig. 6. (A, B) Preoperative whole spine AP and lateral view showed coronal and sagittal imblance with T-L kyphosis. (C, D) VCR is adequate surgical method to correct coronal and sagittal imbalance. Postoperative whole spine AP and lateral views showed good coronal and sagittal imbalance. 23

5 Table 4. Radiological parameters (pre and final follow-up) Pre-op Final follow-up p-value Pelvic Incidence(PI) 53.0 ± ± Scral Slope (SS) 19.0 ± ± 8.1 < Pelvic Tilt (PT) 34.0 ± ± 9.3 < Lumbar Lordosis (LL) 15.0 ± ± 13 < Thoracolumbar Junction (TLJ) 18.8 ± ± Thoracic Kyphosis (TK) 11.0 ± ± 11.8 < C7 Plumb line (C7) ± ± 29 < Mean ± SD, Paired t-test (Table 1)(Fig. 4,5). In the anterior approach, the anterior column height is increased to decrease the deformity. The posterior approach generally involves posterior-column shortening procedures such as SPO, PSO, and VCR that allow for the enhancement of lordosis. In patients with posterior instrumentation in place and a fixed deformity, we prefer a posterior approach for the first stage of surgery, where the hardware removal and osteotomy is carried out through the posterior fusion mass or through any identified pseudoarthrosis. As the second step, an anterior interbody fusion is performed, followed by posterior instrumentation and fusion. If the patient has severe lordosis, additional posterior-column shortening procedures may be performed to restore sagittal balance. Anterior surgical approach is not advisable for patients who have previously undergone interbody fusion or an anterior lumbar interbody fusion. In these patients, PSO is performed. VCR is indicated for patients with severe sagittal imbalance due to compression fracture or a combination of severe sagittal and coronal imbalance (Fig. 6). How many levels should be fused (Table 2)? Whether fusion extension above thoracolumbar junction or not depend on the thoracolumbar junction angle (L 2-T10). If the thoracolumbar junction have lordotic curve, fu- Fig. 7. (A) Whole spine lateral view showed sagittal imblance with T-L junction lordosis. (B) Postoperative whole spine lateral view showed good sagittal imbalance after restoration of lumbar lordosis. 24 Fig. 8. (A) Whole spine lateral view showed severe sagittal imbalance with T-L junction kyphosis. (B) Postoperative whole spine lateral view showed good sagittal imbalance after correction of T-L kyphosis.

6 Table 5. Functional outcomes Pre-op Final Follow-up p-value VAS(Back) 7.6 ± ± 2.2 < VAS(Leg) 6.5 ± ± 2.2 < ODI 68.2 ± ± 17.6 < SRS 22(Function/activity) 2.1 ± ± 0.7 < SRS 22(Pain) 1.7 ± ± 0.8 < SRS 22(Self-image) 1.7 ± ± 0.7 < SRS 22 (Mental Health) 2.5 ± ± 0.6 < Satisfaction/Dissatisfaction with Management 4.3 ± 0.9 PSI 4.4 ± 0.9 Mean ± SD, Wilcoxon s signed rank test sion levels need not to be extended above thoracolumbar junction (Fig. 7). On the contrary, if the thoracolumbar junction have kyphotic curve more than 20 degree, fusion levels should be extended above thoracolumbar junction (Fig. 8). Results 1. Causes of sagittal imbalance The causes of sagittal imbalance in this study include failure of restoration of LL in 21 cases, proximal vertebral compression fracture in 12 cases, junctional kypho- Fig. 9. Most common causes of sagittal imbalance result from include failure of restoration of lumbar lordosis. 25

7 sis in 7 cases, and instrumentation failure or non union in 2 cases. In this study, the most common causes of sagittal imbalance were an inadequate lumbar fusion surgery and adjacent disc degeneration (Table 2 and Fig. 9,10,11,12) 2. Complications Fifteen patients out of 35 had perioperative complications including proximal junctional kyphosis (PJK) or proximal compression fracture in 5, radiculopathy or motor weakness in 3, infection in 2, screw malpositioning in 1, instrumentation failure in 1, dural tearing in 2, and incisional hernia in 1 patient. Of these 15 patients, 10 underwent unexpected operations because of these complications. For solving theses complications, various procedures including posterior fusion extension, vertebroplasty, PSO, or VCR were performed. 3. Radiographic findings The mean C7 sagittal plumb line for all 35 patients improved from 116±65 mm preoperatively to 32±29 mm at the final follow-up visit. Mean LL was 15 ±20 before surgery, and it increased by 23 (-38 ±13) at the final follow-up. Sacral slope (p= 0.000), pelvic tilting (p= 0.000) and thoracic angle (p= 0.000) were statistically different between preoperative and final measurement (Table 4). After the restoration of lumbar lordosis, pelvic position was rotated anteroversion which was presented with decreased pelvic tilting and increased sacral slope. LL/PI ratio (p= 0.000) also was statistically different between preoperative and final measurement (Table 4). 4. Outcome analysis The functional outcome was measured using SRS 22. The SRS-22 questionnaire includes five domains. The domains and the number of questions in them are as follows: function/activity(5), pain (5), self-image(5), mental health(5), satisfaction/dissatidfaction with management(5). The SRS-22 outcome scores at 2 year postoperative did demonstrate significant differences comparing to preoperative scores in all five domains (Table 5). A higher score is better result. The score on the last follow-up function, pain, self -image, function, and satisfaction subsclaes of the patients demonstrated significant different scores compared with the preoperative scores (Table 5). 5. Oswestry scores Nineteen patients completed items from the Oswestry questionnaire both preoperatively and postoperatively. The mean ODI scores improved from 62± 11 before the surgery to 36 ± 12 after the surgery (P < ). Discussion Fig. 10. Proximal vertebral compression fracture is another cause of sagittal imbalance after lumbar fusion. Flat back syndrome was initially recognized by Doherty in 1973 as a postural disorder of the spine caused by distraction instrumentation during the correction of scoliosis. 1 While distraction instrumentation is classically the primary cause of sagittal imbalance, other important contributing factors have also been identified. These include failure to create LL during fusion surgery, 23-26) 3,5 27) pseudoarthrosis following spinal fusion, thoracolumbar kyphosis without lumbar compensation, 27) 26

8 or decompensation by adjacent segments cephalad or caudal to a fusion mass. 2,3,6) Due to the increasing application of lumbar fusions for the treatment of degenerative spondylolisthesis, scoliosis, or stenosis with instability, various failed back surgery syndromes due to sagittal imbalance have been 3,6, 28,29) encountered. Especially, a degenerative flat back developed from degenerative loss of LL or flat back syndrome has been commonly reported in the Asian population. 30) Failure to correct degenerative flat back syndrome can result in another failed back surgery syndrome due to sagittal imbalance. Failure to achieve sufficient LL accelerates inferior or superior adjacent segment degeneration leading to the loss of additional lordosis ) Therefore, greater attention should be paid to sagittal alignment and enhancement of LLduring all lumbar fusions. Thoracolumbar kyphosis may preexist as a result of thoracolumbar or lumbar scoliosis or a post-traumatic etiology. When TK increases, LL increases as a compensatory measure. However, in patients with degenerative loss of LL or previous inadequate lumbar fusions, thoracolumbar kyphosis results in sagittal imbalance. 6,27) Failure to create LL in a previous operation often causes compression fracture of the proximal vertebral body leading to severe sagittal imbalance. Large cantilever loads are transmitted to the proximal vertebral body of fusion mass. 31,32) This biomechanical stress may increase the risk of proximal vertebral body compression fracture (Fig. 11,12). Sagittal imbalance can be compensated by pelvic retroversion to maintain erect posture, which are controlled by erect spinae musculature. The pelvis can be retroversed, resulting in a decreased sacral slope and a increased pelvic tilting to compensate saggital imbalance. This change might have resulted in back muscle fatigue and exhaustion, which led to intractable back pain in standing posture. This back pain could be relieved by Fig. 11. Combined failure of restoration of lumbar lordosis and proximal junctional kyphosis are common causes of sagittal imbalance after lumbar fusion surgery. 27

9 changing of pelvic position which is possible by restoration of lumbar lordosis. After the restoration of lumbar lordosis, pelvic position was rotated anteroversion which was presented with decreased pelvic tilting and increased sacral slope. In this study, 12 out of 35 patients showed that proximal vertebral body of the fusion mass was compressed resulting in severe sagittal imbalance. The causes of sagittal imbalance after fusion surgery were found to be inadequate lumbar fusion surgery and proximal vertebral body collapse without trauma. To prevent flat back syndrome, a surgeon should assess sagittal balance preoperatively, avoid distraction of instrumentation and extension of long fusions into the lower lumbar spine, enhance physiologic lordosis during lumbar fusions, and place a patient in position with the hips extended intraoperatively. 33) The choice of surgical technique for the correction of sagittal deformity may depend on the required lordosis and flexibility. Required LL is determined by pelvic incidence. LL should be restored as much as pelvic incidence. 12,34) Therefore, LL/PI ratio is important spinopelvic parameter for evaluation of sagittal imbalance and. In our study, the LL/PI ratio was changed from 0.029± preoperatively to -0.86±0.23 postoperatively. Inadequate restoration of lumbar lordosis after lumbar fusion surgery showed statistically different from adequate restoration of lumbar lordosis in LL/PI ratio. Especially in the patients with high PI patients required high lumbar lordosis as much as PI (Fig. 13). Therefore, for the evaluation of dianosis and surgical outcomes for the patients with sagittal imbalance, LL/ PI ratio was considered as one of the valuable spinpelvic parameter. Most cases of iatrogenic fixed sagittal imbalance involved rigid deformities. For its treatment, the PAP approach is the commonly used sequence. This sequence usually involves posterior and anterior release and structural graft, followed by a posterior-base procedure including SPO, PSO, and VCR. After the posterior and anterior release, surgery should, therefore, focus on the anterior support, height restoration and posterior shortening in order to generate adequate lumbar lordosis. However, in some cases, we could not get enough lumbar lordosis by PAP sequential approach. By doing addition PSO procedure, we could get enough lumbar Fig. 12. Combined failure of restoration of lumbar lordosis and proximal compression fracture are common causes of sagittal imbalance after lumbar fusion surgery. 28

10 lordosis. Posterior-based procedures have been well described for the surgical management of primary sagittal plane deformities. Possible posterior procedures include SPO, and PSO. 17,18) The VCR achieves balance in the sagittal and coronal planes by shortening the length of the spinal column. 22) Our indications for a PSO for the correction of sagittal deformity include a prior circumferential fusion of the lumbar spine. Revision deformity surgeries have a high risk of complications. Overall complication rate following posterior correction of flat back syndrome ranges from 20% to 60%. These surgical complications include pseudoarthrosis, nerve root injury, radiculopathy, cauda equina syndrome due to epidural hematoma, and inadequate correction of lumbar kyphosis. 2,5,6,28,29) Sagittal imbalance after spinal fusion surgery may be a major source of pain and disability, which could be treated by restoration of lumbar lordosis. Conclusions The most common cause of revision spine surgery due to sagittal imbalance is the failure to enhance LL during lumbar fusion surgery. LL/PI ratio was considered as one of the valuable spinpelvic parameter for evaluation of sagittal imbalance. Patients were effectively treated with combined anterior and posterior arthrodesis, SPO, PSO, VCR or combined procedures. After the surgical treatment, sagittal balance improved in general, with fair-to-good clinical outcomes, high patient satisfaction, although the perioperative complication rates are high. Key point Sagittal balance should be taken consideration before lumbar fusion surgery. Adequate restoration of lumbar lordosis is needed to prevent sagittal imbalance ( LL=PI) LL/PI value is important spinopelvic parameter in evaluation of sagittal imbalance. Construct should be extended thoracolumbar junction (T10-L2) if this angle is more than 20 kyphosis preoperatively References Fig. 13 (A) Whole spine lateral view showed severe sagittal imbalance with high PI. (B) High PI patient is required high lumbar lordosis as much as PI. 1. Doherty JH. Complications of fusion in lumbar scoliosis: proceedings of the Scoliosis Research Society. J Bone Joint Surg Am. 1973;55: Berven SH, Deviren V, Smith JA, Emami A, Hu SS, Bradford DS. Management of fixed sagittal plane deformity: results of the transpedicular wedge resection osteotomy. Spine. 2001;26: Bridwell KH, Lenke LG, Lewis SJ. Treatment of spinal stenosis and fixed sagittal imbalance. Clin Orthop. 2001;384: Cummine JL, Lonstein JE, Moe JH, Winter RB, Bradford DS. Reconstructive surgery in the adult for failed scoliosis fusion. J Bone Joint Surg Am. 1979;61: Lagrone MO, Bradford DS, Moe JH, Lonstein JE, Winter RB, Ogilvie JW. Treatment of symptomatic flatback after spinal fusion. J Bone Joint Surg Am. 1988;70: Kostuik JP, Maurais GR, Richardson WJ, Okajima Y. Combined 29

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12 cal treatment of adult scoliosis. A review of two hundred and twenty-two cases. J Bone Joint Surg Am. 1981;63: Potter BK, Lenke LG, Kuklo TR. Prevention and Management of iatrogenic flatback deformity. J Bone Joint Surg Am. 2004;86- A: Schwab F, Lafage V, Patel A, Farcy JP. Sagittal plane consideration and the pelvis in the adult patient. Spine. 2009;34: 요추유합술후시상면불균형 장지수, 이상호우리들병원신경외과 목적 : 요추유합술시시상면균형에대한임상적중요성이점차강조되고있다. 요추유합술후시상면불균형으로인한임상증상으로재수술이필요하기때문이다. 본연구는요추유합술후시상면불균형으로재수술을받은 35 명을후향적으로분석하였다. 수술전후의임상양상과방사선학적변화를관찰하였으며수술후합병증을분석하였다. 대상및방법 : 요추전만각복원을위해전후방접근과절골술등다양한수술방법을적용하였으며수술후기능적평가를하였다. 결과 : 요추유합술후시상면불균형으로재수술을받은환자는대부분처음요추유합술시요추의전만각복원의실패에있으며따라서요추유합술시항상시상면균형을고려해야한다. 본연구에따르면요추의전만각복원목표는 PI 값에따라다르며따라서 LL/PI ratio (lumbar lordosis/pelvic incidence) 는시상면균형을평가하는데중요한지표로사용할수있었다. 결론 : 결론적으로요추유합술시시상면균형을고려해야하며필요한전만각복원각도는 PI 값으로예측할수있었다. 색인단어 : 시상면불균형, 스미스 - 피터슨절골술, 척추경골절술과척추제거술 31