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Kirschner wire is more effective than the nerve root retractor in treating patients with disc herniation
Clinical Neurology and Neurosurgery 139 (2015) 51–55
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Kirschner wire is more effective than the nerve root retractor in treating patients with disc herniation Yetian Li, Xiaohai Zhang, Zhiyang Kong, Wenjun Huang, Guangye Wang ∗ Department of Orthopaedics, No. 2 People’s Hospital of Wuhu, China
a r t i c l e
i n f o
Article history: Received 20 May 2015 Received in revised form 28 August 2015 Accepted 1 September 2015 Available online 3 September 2015 Keywords: Kirschner wire Nerve root injury Nerve root retractor Lumbar disc herniation Spinal fusion
a b s t r a c t Objective: To investigate the value of using Kirschner wire in the intraspinal procedures. Methods: From May 2011 to October 2013, a total of 46 patients with a single-level lumbar disc herniation with concomitant lumbar instability were randomly assigned to two groups at the time of admission. Group 1 had 23 patients who underwent posterior lumbar fusion using a nerve root retractor to drag nerve root, and Group 2 also had 23 patients who underwent the same operation by fixing Kirschner wires in the vertebral body to drag nerve root. All of these patients were assessed with visual analog scales (VAS) and Japanese Orthopaedic Association (JOA) scores before surgery, and were followed up at the time points of one week (VAS score only), three, six, and twelve months respectively after surgery. The actual retraction time of the nerve root of each patient was also recorded during the operation. Results: The differences in VAS and JOA scores were not significant between Group 1 and 2 before surgery. However, these scores showed significant improvement in Group 2 at one week and three months after surgery compared with those in Group 1. At six and twelve month follow-up time points, no significant difference was observed between these two groups. However, the retraction time of the nerve root of the patients in Group 2 was significantly shorter than in Group 1. Conclusions: Using Kirschner wires instead of the nerve root retractor to pull nerve root in the patients with a single-level lumbar disc herniation accompanied by the lumbar instability is more effective in reducing the dragging damage of the nerve root at early phases after surgery and in shortening retraction time. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Clinically, lumbar instability, lumbar disc herniation, lumbar spinal stenosis, and lumbar spondylolisthesis are common lumbar lesions. These diseases are characterized by a number of symptoms including low back pain and radiculopathy, which are usually improved with appropriate conservative treatments [1]; however, surgical intervention is needed in the refractory cases [1,2]. Spinal canal decompression and posterior lumbar interbody fusion are widely recognized as effective operations to treat patients with lumbar lesions [3]. In these cases, surgeons usually choose a posterior approach to decompress nerve roots and cauda equina. Also, during the operation, the retraction of nerve roots and dura is needed to expose disc space followed by cage placement [4,5].
∗ Corresponding author at: Department of Orthopaedics, No. 2 People’s Hospital of Wuhu, Wuhu 241000, China. E-mail address: [email protected] (G. Wang). http://dx.doi.org/10.1016/j.clineuro.2015.09.001 0303-8467/© 2015 Elsevier B.V. All rights reserved.
Actually, the retraction injury of nerve roots and dura is a leading cause of the lower limb pain, numbness, weakness, and even the failure of back surgery [5–7]. Moreover, excessive retraction of the nerve root has an especially disastrous effect on the posterior ramus. Thus, such a violent maneuver within the spinal canal must be avoided or reduced to the minimum [6], and how to avoid the intraoperative retraction injury is an important measure to assess the success of an intraspinal operation. To expose nerve roots and remove disc materials, the nerve root retractor has been an useful surgical instrument [8,9]. However, the old version of nerve root retractor once commonly used in clinic could cause nerve root injury due to various reasons including excessive traction [5,6]. At present, the ever widely used newstyle nerve root retractor such as the Love nerve root retractor has also not been recommended for its clinical use due to its complex structure and poor clinical utility [5]. Therefore, finding a safe and effective method to retract nerve root and expose disc space would hold great promise for clinic. The present study was aimed to investigate the clinical value of using Kirschner wires to alter the position of the nerve root in the intraspinal operation.
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Y. Li et al. / Clinical Neurology and Neurosurgery 139 (2015) 51–55
Fig. 1. The two instruments shown in (A) are the nerve root retractor. (B) Intervertebral space exposed with use the retractors, and two pedicle screws by the side of the retractors.
2. Materials and methods
2.2. Operative technique
2.1. Patients
All patients were operated on using standard procedures. Briefly, patients were placed in a prone position on a Jackson spinal table. A posterior midline incision was performed, followed eventually by subperiosteal exposure of the posterior elements of the intended motion segment. The paravertebral muscle was retracted bilaterally using a self-retaining retractor. The placement of four pedicle screws was monitored through the X-ray machine (Sino 6.0pedicle Screw Fixation System, Sandong Wego Orthopaedic Device Co., Ltd.). The hemilaminectomy was executed in all patients so that the spinal space was appropriately exposed, the involved nerve root was easily released, and the intervertebral fusion was smoothly finished. To obtain a suitable nerve root tension, we loosed about 1.5-cm length nerve root. The thecal sac and traversing nerve roots were mobilized and retracted to the midline using two methods: (1) in Group 1, the nerve root retractor was used to alter the position of the involved nerve root intraoperatively, thereby optimizing the surgical exposure. At this point the underlying disc was exposed (Fig. 1); (2) in Group 2, two Kirschner wires (diameter, 0.5 mm/each; length, 25 cm/each) were fixed in the adjacent vertebral bodies to alter the position of the involved nerve root intraoperatively. The nerve root was retracted to the midline, and brain cotton piece was place in the middle of nerve root and Kirschner wires (Fig. 2). To prepare the disc space, any posterior osteophytes or osteocartilaginous materials were removed using a combination of standard disc rongeurs, disc shavers, reamer, and downbiting curved curettes. The cartilaginous end plates were denuded while the neural elements were protected. Generally, a 22-mm deep cage was used for females and a 26-mm deep cage for males (Milestonelumbar Fusion System, Sandong Wego Orthopaedic Device
Between May 2011 and September 2013, totally 46 patients were enrolled in our hospital, who had both (1) single-level disc herniation and (2) evidence of associated spinal segmental instability, as diagnosed by the radiography with the following criteria: exceeding 3 mm translatory or 11◦ angulatory motion on active flexion-extension lateral or anteroposterior bending radiographs. All patients had suffered from some backache and unilateral radiating pain of lower limbs over the preceding five years. These patients were randomly divided into two groups. Group 1 had 13 males and 10 females with an average age of 58.81 years (range, 44–74 years), and Group 2 had 11 males and 12 females with an average age of 55.05 years (range, 35–76 years). All patients complained of unilateral leg pain with or without lower back pain, muscle weakness, and/or sensory loss, and all patients had undergone a period of conservative therapy, including physiotherapy and acupuncture, chiropractic treatment, or massage, for at least three months before admission. Plain radiographs and MR images were obtained in all subjects to diagnose the single-level disc herniation in association with lumbar instability. Patients were excluded if they had (1) degenerative spondylolisthesis of Grade I or greater at the level of the degenerative disc or at an adjacent level, (2) multi-level disc herniation and lumbar instability, (3) potential destruction of the inside cortical bone of vertebral pedicle in the course of placement screw, or (4) any form of malignancy. The trial was approved by the Wuhu Ethics Committee, Anhui, China.
Fig. 2. (A) The Kirschner wires used in the surgery in Group 2. (B) The Kirschner wires were fixed in the vertebral body to expose the operative area. (C) Lateral radiograph showing the position of Kirschner wires in the vertebral body and reamer used to excise cartilaginous end plates.
Y. Li et al. / Clinical Neurology and Neurosurgery 139 (2015) 51–55
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Fig. 5. Comparison of pre- and post-operative VAS scores at different follow-up time points between Group 1 and 2.
Table 1 Comparison of the levels of lumbar disc herniation affected in two groups.
Fig. 3. The postoperation lateral radiograph.
L3–L4 L4–L5 L5–S1
Group 1
Group 2
2 12 7
0 12 9
There was no significant difference in levels affected by group (p > 0.05).
Co., Ltd.), and we filled the artificial and autologous bones in disc space first, and then the cage devices, which were tamped into the disc space to engage the vertebral end plates. Efforts were made to minimize the actual time of nerve root retraction. The length of retraction time of all patients was recorded (Fig. 3). 2.3. Clinical evaluation With informed consent, patients were requested by an independent researcher to provide background information and to complete the following outcome assessment scores: AVS score was assessed at one week, and both VAS and JOA scores were assessed at the time points of three, six, and twelve months after surgery, respectively. 2.4. Statistical methods All data are presented as mean ± standard deviation (SD). Student’s t-test was used for statistical analysis of those data presented in Table 2, Figs. 4 and 5, and chi-square test for the data in Table 1 between two groups. p < 0.05 was considered statistically significant.
Fig. 4. Comparison of pre- and post-operative JOA scores at different follow-up time points between Group 1 and 2.
Table 2 Comparison of age and retraction time in two groups.
Age Retraction time
Group 1
Group 2
58.81 ± 9.46 11.38 ± 1.99
55.24 ± 10.11 10.05 ± 2.16
Data were presented as mean ± SD. The difference between two groups was not statistically significant in age, but was significant in retraction time. *p < 0.05.
3. Results At the follow-up time point of one year after surgery, 42 out of 46 patients were available for clinical review. The failure in follow-up of four patients was due to refusal to complete the outcome assessments (1), revision surgery (1), and loss of contact (2). Our results indicated that there was a significant difference in the retraction time of the nerve root between the two groups (Table 2). The average VAS score for leg pain and/or tingling at the time point of one week and three months, and the average JOA score at three month follow-up time point in Group 2 showed significant improvement compared with those in Group 1; however, the average VAS and JOA scores at six and twelve month time points showed no significant difference between these two groups (Figs. 4 and 5). In Group 1, there were two significant improvements in VAS scores, with one between one week and three months and the other between three and six months after surgery, respectively. Also, there was one significant improvement in JOA score in Group 1 between three and six months after operation (Figs. 4 and 5). However, only one significant improvement in VAS score was observed between one week and three months after operation in Group 2 (Figs. 4 and 5). In addition, in Group 1, two patients who experienced the complication of foot drop gained a satisfactory recovery until one year after surgery, when the symptoms of leg pain and/or tingling became more serious than those before operation. In Group 2, one patient, whose data was excluded, required revision surgery for cage displacement at two months post-operation.
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Y. Li et al. / Clinical Neurology and Neurosurgery 139 (2015) 51–55
4. Discussion Since Nagayama et al. reported nucleotomy after partial laminectomy for a lumbar disc herniation [6], this procedure has been the gold standard for patients with such lesions. In recent years, after numerous adaptations and innovations of surgical techniques, posterior lumbar fusion has also been widely accepted as an effective operation mode for lumbar lesions including spondylolisthesis, degenerative disc disease or spinal instability [10]. However, there were some cases in which patients had more severe leg pain, low back pain and discomfort after intraspinal procedures than before operation. The injury of the posterior ramus after excessive retraction of the nerve root was believed to contribute to these postsurgical symptoms [11,12]. Compared with the peripheral nerves, spinal nerve roots have no perineurium and are covered only with a thin root sheath [13]. In addition, spinal nerve roots have a poorly developed vascular network compared with the peripheral nerves and have no regional arteriolar blood supply [14]. Therefore, nerve root compression easily induces structural change compared with the peripheral nerve. Matsui et al. [15] demonstrated a correlation between retraction pressure and alteration of blood flow within nerve roots in the patients with lumbar intervertebral disc herniation who underwent posterior discectomy. Also, the retraction injury of nerve roots and dura was believed to be the leading cause of the early limb pain, limb numbness, and weakness [5,6]. Therefore, how to reduce the nerve root retraction injury attracts increasing attention in recent years. Cui et al. [16] developed a new-style nerve root retractor using baroreceptor to reduce traction nerve injury, but the complexity of equipment has limited its clinical utilization. To reduce the traction injury, Bindal et al. [17] suggested that intraoperative neural physiological function monitoring or intraoperative wake-up test should be performed if the condition is allowed. Considering the universality of nerve root injury and insufficiency of the current design of nerve root retractor in the posterior lumbar operation, we designed a simple drawing device which only needed two 2.5-mm Kirschners and a soft rubber tube. In order to rule out other influencing factors, we chose single-segmental disc herniation cases accompanied by intervertebral instability, which were the indication of intervertebral fusion surgery. During the follow-up periods, we found that two patients in Group 1 showed numbness, weakness, pain of limbs and foot drop that were more serious than before operation although both of them have gained desired recovery within one year after surgery. In contrast, in Group 2, no patients were found to have such issues. Meanwhile, those patients in Group 2 obtained better VAS and JOA scores than the ones in Group 1 during the first six month follow-up period after surgery. We summarized the advantages of using Kirschner wires over the conventional retractor: (1) The consistent traction force, that was obtained through fixing the Kirschner wires in the vertebral body, avoided causing excessive artificial involuntary traction damage of nerve root, especially the acute traction damage. With a traditional retractor, in order to show the surgical field, the assistant often unconsciously excessively retracted the nerve root and dura, thus often achieving or exceeding the midline of vertebral canal, sometimes even reaching 3/4 of the spinal canal; (2) The operation was simple, convenient, and practical, and only needed two 2.5-mm Kirschners and two corresponding soft rubber tubes which were used to reduce the cutting injury; this technique did not require any special equipment or professional knowledge training; (3) After fixing of Kirschners, the assistant did not need to retract the nerve root and dura, and thus the man power was saved. However, with a retractor, the assistant must perform this action during operation; (4) High safety: in the intraspinal procedures,
especially during the lumbar discectomy and intervertebral fusion, the bleeding of venous plexus in the spinal canal often blurred the surgical field. We might have to take the risk of missing the nerve root in the field or failing to pull the nerve roots out of the surgical field accidentally. Then the surgeon had to use reamer or scraper to remove intervertebral disc and the nucleus or place the cage devices, and the contusion of nerve root may be inevitable. In contrast, by fixing Kirschners in the vertebral body to isolate the nerve root outside the surgical field, such risks can be completely avoided; (5) Shortening traction time: when nerve roots were retracted with a retractor, we usually spent some time, which could be saved by this new method, in repetitively confirming that the nerve root was retracted outside the operating field. Also, in general, we did not need to readjust the position of the Kirschner wires after their placement, because we usually had gently pushed away the nerve root and dural sac from the next operation area before we placed Kirschner. In the first half year of follow-up after surgery, the patients in Group 2 showed better VAS and JOA scores than the ones in Group 1. Thus, we have good reasons to believe that the traditional nerve root retractor caused more obvious damage to nerve root than Kirschners, especially in the first two weeks after surgery, when more pronounced intraneural edema may contribute to more serious limb pain symptoms in Group 1. However, the injured nerve has been shown to be capable of regeneration, which usually occurs in the first six months after operation. Macnab et al. [18] reported that denervation potentials were demonstrated within one year after surgery, but polyphasic potentials, which indicated partial reinnervation, were found in many of their patients six weeks after surgery. In an experimental study in dogs, Yoshizawa et al. [19] also observed regeneration of the spinal unit at three months after nerve root compression, regenerated myelinated nerve fiber at six months, and regenerated nerve fiber within the whole of the injured nerve root. Therefore, it is highly likely that the various statuses of regeneration of postoperative nerve fibers may contribute to the different results of VAS and JOA scores at later phases after surgery. Although we showed the advantages of using Kirschner wire over using the nerve root retractor in our study, some limitations should be noted. For example, the technique used in our study only applies to the PLIF operation but not the more widely used TLIF operation. Also, whether it can be used in the percutaneous procedures that use tubular retraction systems needs investigation. In addition, the sample size in the present study was small, and a further study with a larger cohort will be needed to further corroborate our observations. Finally, its long term beneficial effects on patients compared with the conventional retractor remain to be determined.
5. Conclusion We report here that using Kirschners to replace the nerve root retractor to retract nerve root not only shortens operative time and reduces the injury of retraction nerve root in the early phase, but also effectively avoids the serious contusion of nerve root. Thus, using Kirschner wire in treating patients with a disc herniation provides a safer, more effective and practical method to finish intervertebral posterior fusion.
Conflict of interest All the authors declare that they have no conflict of interest.
Y. Li et al. / Clinical Neurology and Neurosurgery 139 (2015) 51–55
Acknowledgement It was funded by the Major Science and Technology Project of Wuhu City (2014zd16). References [1] J.Y. Lee, P.G. Whang, J.Y. Lee, F.M. Phillips, A.A. Patel, Lumbar spinal stenosis, Instr. Course Lect. 62 (2013) 383–396. [2] S. Genevay, S.J. Atlas, J.N. Katz, Variation in eligibility criteria from studies of radiculopathy due to a herniated disc and of neurogenic claudication due to lumbar spinal stenosis: a structured literature review, Spine (Phila Pa 1976) 35 (2010) 803–811. [3] F. Omidi-Kashani, E.G. Hasankhani, A. Ashjazadeh, Lumbar spinal stenosis: who should be fused? An updated review, Asian Spine J. 8 (2014) 521–530. [4] K. Haba, M. Ikeda, M. Soma, T. Yamashima, Bilateral decompression of multilevel lumbar spinal stenosis through a unilateral approach, J. Clin. Neurosci. 12 (2005) 169–171. [5] C. Feltes, K. Fountas, R. Davydov, V. Dimopoulos, J.S. Robinson Jr., Effects of nerve root retraction in lumbar discectomy, Neurosurg. Focus 13 (2002) E6. [6] R. Nagayama, H. Nakamura, Y. Yamano, T. Yamamoto, Y. Minato, M. Seki, S. Konishi, An experimental study of the effects of nerve root retraction on the posterior ramus, Spine (Phila Pa 1976) 25 (2000) 418–424. [7] R.G. Hazard, Failed back surgery syndrome: surgical and nonsurgical approaches, Clin. Orthop. Relat. Res. 443 (2006) 228–232. [8] U. Schick, J. Dohnert, Technique of microendoscopy in medial lumbar disc herniation, Minim. Invasive Neurosurg. 45 (2002) 139–141.
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[9] P.C. Hsieh, C.H. Wang, Posterior endoscopic lumbar discectomy using a thoracoport as a tubular retractor, Minim. Invasive Neurosurg. 47 (2004) 319–323. [10] M. Fernandez-Fairen, P. Sala, H. Ramirez, J. Gil, A prospective randomized study of unilateral versus bilateral instrumented posterolateral lumbar fusion in degenerative spondylolisthesis, Spine (Phila Pa 1976) 32 (2007) 395–401. [11] N. Hayashi, T. Tamaki, H. Yamada, Experimental study of denervated muscle atrophy following severance of posterior rami of the lumbar spinal nerves, Spine (Phila Pa 1976) 17 (1992) 1361–1367. [12] H. Paajanen, M. Erkintalo, R. Parkkola, J. Salminen, M. Kormano, Age-dependent correlation of low-back pain and lumbar disc regeneration, Arch. Orthop. Trauma Surg. 116 (1997) 106–107. [13] F.R. Haller, F.N. Low, The fine structure of the peripheral nerve root sheath in the subarachnoid space in the rat and other laboratory animals, Am. J. Anat. 131 (1971) 1–19. [14] W.W. Parke, R. Watanabe, The intrinsic vasculature of the lumbosacral spinal nerve roots, Spine (Phila Pa 1976) 10 (1985) 508–515. [15] H. Matsui, H. Kitagawa, Y. Kawaguchi, H. Tsuji, Physiologic changes of nerve root during posterior lumbar discectomy, Spine (Phila Pa 1976) 20 (1995) 654–659. [16] Z.M. Cui, W.D. Li, G.F. Bao, G.H. Xu, Y.Y. Sun, L.L. Wang, L.Y. Zhu, Study of nerve root traction injury in lumbar interbody fusion from posterior rout approach, Orthop. J. China 21 (2008) 1619–1621. [17] R.K. Bindal, S. Ghosh, Intraoperative electromyography monitoring in minimally invasive transforaminal lumbar interbody fusion, J. Neurosurg. Spine 6 (2007) 126–132. [18] I CH Macnab, C.M. Godfrey, The incidence of denervation of the sacrospinales muscles following spinal surgery, Spine 2 (1977) 294–298. [19] H. Yoshizawa, S. Kobayashi, T. Morita, Chronic nerve root compression. Pathophysiologic mechanism of nerve root dysfunction, Spine (Phila Pa 1976) 20 (1995) 397–407.
Contents lists available at ScienceDirect
Clinical Neurology and Neurosurgery journal homepage: www.elsevier.com/locate/clineuro
Kirschner wire is more effective than the nerve root retractor in treating patients with disc herniation Yetian Li, Xiaohai Zhang, Zhiyang Kong, Wenjun Huang, Guangye Wang ∗ Department of Orthopaedics, No. 2 People’s Hospital of Wuhu, China
a r t i c l e
i n f o
Article history: Received 20 May 2015 Received in revised form 28 August 2015 Accepted 1 September 2015 Available online 3 September 2015 Keywords: Kirschner wire Nerve root injury Nerve root retractor Lumbar disc herniation Spinal fusion
a b s t r a c t Objective: To investigate the value of using Kirschner wire in the intraspinal procedures. Methods: From May 2011 to October 2013, a total of 46 patients with a single-level lumbar disc herniation with concomitant lumbar instability were randomly assigned to two groups at the time of admission. Group 1 had 23 patients who underwent posterior lumbar fusion using a nerve root retractor to drag nerve root, and Group 2 also had 23 patients who underwent the same operation by fixing Kirschner wires in the vertebral body to drag nerve root. All of these patients were assessed with visual analog scales (VAS) and Japanese Orthopaedic Association (JOA) scores before surgery, and were followed up at the time points of one week (VAS score only), three, six, and twelve months respectively after surgery. The actual retraction time of the nerve root of each patient was also recorded during the operation. Results: The differences in VAS and JOA scores were not significant between Group 1 and 2 before surgery. However, these scores showed significant improvement in Group 2 at one week and three months after surgery compared with those in Group 1. At six and twelve month follow-up time points, no significant difference was observed between these two groups. However, the retraction time of the nerve root of the patients in Group 2 was significantly shorter than in Group 1. Conclusions: Using Kirschner wires instead of the nerve root retractor to pull nerve root in the patients with a single-level lumbar disc herniation accompanied by the lumbar instability is more effective in reducing the dragging damage of the nerve root at early phases after surgery and in shortening retraction time. © 2015 Elsevier B.V. All rights reserved.
1. Introduction Clinically, lumbar instability, lumbar disc herniation, lumbar spinal stenosis, and lumbar spondylolisthesis are common lumbar lesions. These diseases are characterized by a number of symptoms including low back pain and radiculopathy, which are usually improved with appropriate conservative treatments [1]; however, surgical intervention is needed in the refractory cases [1,2]. Spinal canal decompression and posterior lumbar interbody fusion are widely recognized as effective operations to treat patients with lumbar lesions [3]. In these cases, surgeons usually choose a posterior approach to decompress nerve roots and cauda equina. Also, during the operation, the retraction of nerve roots and dura is needed to expose disc space followed by cage placement [4,5].
∗ Corresponding author at: Department of Orthopaedics, No. 2 People’s Hospital of Wuhu, Wuhu 241000, China. E-mail address: [email protected] (G. Wang). http://dx.doi.org/10.1016/j.clineuro.2015.09.001 0303-8467/© 2015 Elsevier B.V. All rights reserved.
Actually, the retraction injury of nerve roots and dura is a leading cause of the lower limb pain, numbness, weakness, and even the failure of back surgery [5–7]. Moreover, excessive retraction of the nerve root has an especially disastrous effect on the posterior ramus. Thus, such a violent maneuver within the spinal canal must be avoided or reduced to the minimum [6], and how to avoid the intraoperative retraction injury is an important measure to assess the success of an intraspinal operation. To expose nerve roots and remove disc materials, the nerve root retractor has been an useful surgical instrument [8,9]. However, the old version of nerve root retractor once commonly used in clinic could cause nerve root injury due to various reasons including excessive traction [5,6]. At present, the ever widely used newstyle nerve root retractor such as the Love nerve root retractor has also not been recommended for its clinical use due to its complex structure and poor clinical utility [5]. Therefore, finding a safe and effective method to retract nerve root and expose disc space would hold great promise for clinic. The present study was aimed to investigate the clinical value of using Kirschner wires to alter the position of the nerve root in the intraspinal operation.
52
Y. Li et al. / Clinical Neurology and Neurosurgery 139 (2015) 51–55
Fig. 1. The two instruments shown in (A) are the nerve root retractor. (B) Intervertebral space exposed with use the retractors, and two pedicle screws by the side of the retractors.
2. Materials and methods
2.2. Operative technique
2.1. Patients
All patients were operated on using standard procedures. Briefly, patients were placed in a prone position on a Jackson spinal table. A posterior midline incision was performed, followed eventually by subperiosteal exposure of the posterior elements of the intended motion segment. The paravertebral muscle was retracted bilaterally using a self-retaining retractor. The placement of four pedicle screws was monitored through the X-ray machine (Sino 6.0pedicle Screw Fixation System, Sandong Wego Orthopaedic Device Co., Ltd.). The hemilaminectomy was executed in all patients so that the spinal space was appropriately exposed, the involved nerve root was easily released, and the intervertebral fusion was smoothly finished. To obtain a suitable nerve root tension, we loosed about 1.5-cm length nerve root. The thecal sac and traversing nerve roots were mobilized and retracted to the midline using two methods: (1) in Group 1, the nerve root retractor was used to alter the position of the involved nerve root intraoperatively, thereby optimizing the surgical exposure. At this point the underlying disc was exposed (Fig. 1); (2) in Group 2, two Kirschner wires (diameter, 0.5 mm/each; length, 25 cm/each) were fixed in the adjacent vertebral bodies to alter the position of the involved nerve root intraoperatively. The nerve root was retracted to the midline, and brain cotton piece was place in the middle of nerve root and Kirschner wires (Fig. 2). To prepare the disc space, any posterior osteophytes or osteocartilaginous materials were removed using a combination of standard disc rongeurs, disc shavers, reamer, and downbiting curved curettes. The cartilaginous end plates were denuded while the neural elements were protected. Generally, a 22-mm deep cage was used for females and a 26-mm deep cage for males (Milestonelumbar Fusion System, Sandong Wego Orthopaedic Device
Between May 2011 and September 2013, totally 46 patients were enrolled in our hospital, who had both (1) single-level disc herniation and (2) evidence of associated spinal segmental instability, as diagnosed by the radiography with the following criteria: exceeding 3 mm translatory or 11◦ angulatory motion on active flexion-extension lateral or anteroposterior bending radiographs. All patients had suffered from some backache and unilateral radiating pain of lower limbs over the preceding five years. These patients were randomly divided into two groups. Group 1 had 13 males and 10 females with an average age of 58.81 years (range, 44–74 years), and Group 2 had 11 males and 12 females with an average age of 55.05 years (range, 35–76 years). All patients complained of unilateral leg pain with or without lower back pain, muscle weakness, and/or sensory loss, and all patients had undergone a period of conservative therapy, including physiotherapy and acupuncture, chiropractic treatment, or massage, for at least three months before admission. Plain radiographs and MR images were obtained in all subjects to diagnose the single-level disc herniation in association with lumbar instability. Patients were excluded if they had (1) degenerative spondylolisthesis of Grade I or greater at the level of the degenerative disc or at an adjacent level, (2) multi-level disc herniation and lumbar instability, (3) potential destruction of the inside cortical bone of vertebral pedicle in the course of placement screw, or (4) any form of malignancy. The trial was approved by the Wuhu Ethics Committee, Anhui, China.
Fig. 2. (A) The Kirschner wires used in the surgery in Group 2. (B) The Kirschner wires were fixed in the vertebral body to expose the operative area. (C) Lateral radiograph showing the position of Kirschner wires in the vertebral body and reamer used to excise cartilaginous end plates.
Y. Li et al. / Clinical Neurology and Neurosurgery 139 (2015) 51–55
53
Fig. 5. Comparison of pre- and post-operative VAS scores at different follow-up time points between Group 1 and 2.
Table 1 Comparison of the levels of lumbar disc herniation affected in two groups.
Fig. 3. The postoperation lateral radiograph.
L3–L4 L4–L5 L5–S1
Group 1
Group 2
2 12 7
0 12 9
There was no significant difference in levels affected by group (p > 0.05).
Co., Ltd.), and we filled the artificial and autologous bones in disc space first, and then the cage devices, which were tamped into the disc space to engage the vertebral end plates. Efforts were made to minimize the actual time of nerve root retraction. The length of retraction time of all patients was recorded (Fig. 3). 2.3. Clinical evaluation With informed consent, patients were requested by an independent researcher to provide background information and to complete the following outcome assessment scores: AVS score was assessed at one week, and both VAS and JOA scores were assessed at the time points of three, six, and twelve months after surgery, respectively. 2.4. Statistical methods All data are presented as mean ± standard deviation (SD). Student’s t-test was used for statistical analysis of those data presented in Table 2, Figs. 4 and 5, and chi-square test for the data in Table 1 between two groups. p < 0.05 was considered statistically significant.
Fig. 4. Comparison of pre- and post-operative JOA scores at different follow-up time points between Group 1 and 2.
Table 2 Comparison of age and retraction time in two groups.
Age Retraction time
Group 1
Group 2
58.81 ± 9.46 11.38 ± 1.99
55.24 ± 10.11 10.05 ± 2.16
Data were presented as mean ± SD. The difference between two groups was not statistically significant in age, but was significant in retraction time. *p < 0.05.
3. Results At the follow-up time point of one year after surgery, 42 out of 46 patients were available for clinical review. The failure in follow-up of four patients was due to refusal to complete the outcome assessments (1), revision surgery (1), and loss of contact (2). Our results indicated that there was a significant difference in the retraction time of the nerve root between the two groups (Table 2). The average VAS score for leg pain and/or tingling at the time point of one week and three months, and the average JOA score at three month follow-up time point in Group 2 showed significant improvement compared with those in Group 1; however, the average VAS and JOA scores at six and twelve month time points showed no significant difference between these two groups (Figs. 4 and 5). In Group 1, there were two significant improvements in VAS scores, with one between one week and three months and the other between three and six months after surgery, respectively. Also, there was one significant improvement in JOA score in Group 1 between three and six months after operation (Figs. 4 and 5). However, only one significant improvement in VAS score was observed between one week and three months after operation in Group 2 (Figs. 4 and 5). In addition, in Group 1, two patients who experienced the complication of foot drop gained a satisfactory recovery until one year after surgery, when the symptoms of leg pain and/or tingling became more serious than those before operation. In Group 2, one patient, whose data was excluded, required revision surgery for cage displacement at two months post-operation.
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4. Discussion Since Nagayama et al. reported nucleotomy after partial laminectomy for a lumbar disc herniation [6], this procedure has been the gold standard for patients with such lesions. In recent years, after numerous adaptations and innovations of surgical techniques, posterior lumbar fusion has also been widely accepted as an effective operation mode for lumbar lesions including spondylolisthesis, degenerative disc disease or spinal instability [10]. However, there were some cases in which patients had more severe leg pain, low back pain and discomfort after intraspinal procedures than before operation. The injury of the posterior ramus after excessive retraction of the nerve root was believed to contribute to these postsurgical symptoms [11,12]. Compared with the peripheral nerves, spinal nerve roots have no perineurium and are covered only with a thin root sheath [13]. In addition, spinal nerve roots have a poorly developed vascular network compared with the peripheral nerves and have no regional arteriolar blood supply [14]. Therefore, nerve root compression easily induces structural change compared with the peripheral nerve. Matsui et al. [15] demonstrated a correlation between retraction pressure and alteration of blood flow within nerve roots in the patients with lumbar intervertebral disc herniation who underwent posterior discectomy. Also, the retraction injury of nerve roots and dura was believed to be the leading cause of the early limb pain, limb numbness, and weakness [5,6]. Therefore, how to reduce the nerve root retraction injury attracts increasing attention in recent years. Cui et al. [16] developed a new-style nerve root retractor using baroreceptor to reduce traction nerve injury, but the complexity of equipment has limited its clinical utilization. To reduce the traction injury, Bindal et al. [17] suggested that intraoperative neural physiological function monitoring or intraoperative wake-up test should be performed if the condition is allowed. Considering the universality of nerve root injury and insufficiency of the current design of nerve root retractor in the posterior lumbar operation, we designed a simple drawing device which only needed two 2.5-mm Kirschners and a soft rubber tube. In order to rule out other influencing factors, we chose single-segmental disc herniation cases accompanied by intervertebral instability, which were the indication of intervertebral fusion surgery. During the follow-up periods, we found that two patients in Group 1 showed numbness, weakness, pain of limbs and foot drop that were more serious than before operation although both of them have gained desired recovery within one year after surgery. In contrast, in Group 2, no patients were found to have such issues. Meanwhile, those patients in Group 2 obtained better VAS and JOA scores than the ones in Group 1 during the first six month follow-up period after surgery. We summarized the advantages of using Kirschner wires over the conventional retractor: (1) The consistent traction force, that was obtained through fixing the Kirschner wires in the vertebral body, avoided causing excessive artificial involuntary traction damage of nerve root, especially the acute traction damage. With a traditional retractor, in order to show the surgical field, the assistant often unconsciously excessively retracted the nerve root and dura, thus often achieving or exceeding the midline of vertebral canal, sometimes even reaching 3/4 of the spinal canal; (2) The operation was simple, convenient, and practical, and only needed two 2.5-mm Kirschners and two corresponding soft rubber tubes which were used to reduce the cutting injury; this technique did not require any special equipment or professional knowledge training; (3) After fixing of Kirschners, the assistant did not need to retract the nerve root and dura, and thus the man power was saved. However, with a retractor, the assistant must perform this action during operation; (4) High safety: in the intraspinal procedures,
especially during the lumbar discectomy and intervertebral fusion, the bleeding of venous plexus in the spinal canal often blurred the surgical field. We might have to take the risk of missing the nerve root in the field or failing to pull the nerve roots out of the surgical field accidentally. Then the surgeon had to use reamer or scraper to remove intervertebral disc and the nucleus or place the cage devices, and the contusion of nerve root may be inevitable. In contrast, by fixing Kirschners in the vertebral body to isolate the nerve root outside the surgical field, such risks can be completely avoided; (5) Shortening traction time: when nerve roots were retracted with a retractor, we usually spent some time, which could be saved by this new method, in repetitively confirming that the nerve root was retracted outside the operating field. Also, in general, we did not need to readjust the position of the Kirschner wires after their placement, because we usually had gently pushed away the nerve root and dural sac from the next operation area before we placed Kirschner. In the first half year of follow-up after surgery, the patients in Group 2 showed better VAS and JOA scores than the ones in Group 1. Thus, we have good reasons to believe that the traditional nerve root retractor caused more obvious damage to nerve root than Kirschners, especially in the first two weeks after surgery, when more pronounced intraneural edema may contribute to more serious limb pain symptoms in Group 1. However, the injured nerve has been shown to be capable of regeneration, which usually occurs in the first six months after operation. Macnab et al. [18] reported that denervation potentials were demonstrated within one year after surgery, but polyphasic potentials, which indicated partial reinnervation, were found in many of their patients six weeks after surgery. In an experimental study in dogs, Yoshizawa et al. [19] also observed regeneration of the spinal unit at three months after nerve root compression, regenerated myelinated nerve fiber at six months, and regenerated nerve fiber within the whole of the injured nerve root. Therefore, it is highly likely that the various statuses of regeneration of postoperative nerve fibers may contribute to the different results of VAS and JOA scores at later phases after surgery. Although we showed the advantages of using Kirschner wire over using the nerve root retractor in our study, some limitations should be noted. For example, the technique used in our study only applies to the PLIF operation but not the more widely used TLIF operation. Also, whether it can be used in the percutaneous procedures that use tubular retraction systems needs investigation. In addition, the sample size in the present study was small, and a further study with a larger cohort will be needed to further corroborate our observations. Finally, its long term beneficial effects on patients compared with the conventional retractor remain to be determined.
5. Conclusion We report here that using Kirschners to replace the nerve root retractor to retract nerve root not only shortens operative time and reduces the injury of retraction nerve root in the early phase, but also effectively avoids the serious contusion of nerve root. Thus, using Kirschner wire in treating patients with a disc herniation provides a safer, more effective and practical method to finish intervertebral posterior fusion.
Conflict of interest All the authors declare that they have no conflict of interest.
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Acknowledgement It was funded by the Major Science and Technology Project of Wuhu City (2014zd16). References [1] J.Y. Lee, P.G. Whang, J.Y. Lee, F.M. Phillips, A.A. Patel, Lumbar spinal stenosis, Instr. Course Lect. 62 (2013) 383–396. [2] S. Genevay, S.J. Atlas, J.N. Katz, Variation in eligibility criteria from studies of radiculopathy due to a herniated disc and of neurogenic claudication due to lumbar spinal stenosis: a structured literature review, Spine (Phila Pa 1976) 35 (2010) 803–811. [3] F. Omidi-Kashani, E.G. Hasankhani, A. Ashjazadeh, Lumbar spinal stenosis: who should be fused? An updated review, Asian Spine J. 8 (2014) 521–530. [4] K. Haba, M. Ikeda, M. Soma, T. Yamashima, Bilateral decompression of multilevel lumbar spinal stenosis through a unilateral approach, J. Clin. Neurosci. 12 (2005) 169–171. [5] C. Feltes, K. Fountas, R. Davydov, V. Dimopoulos, J.S. Robinson Jr., Effects of nerve root retraction in lumbar discectomy, Neurosurg. Focus 13 (2002) E6. [6] R. Nagayama, H. Nakamura, Y. Yamano, T. Yamamoto, Y. Minato, M. Seki, S. Konishi, An experimental study of the effects of nerve root retraction on the posterior ramus, Spine (Phila Pa 1976) 25 (2000) 418–424. [7] R.G. Hazard, Failed back surgery syndrome: surgical and nonsurgical approaches, Clin. Orthop. Relat. Res. 443 (2006) 228–232. [8] U. Schick, J. Dohnert, Technique of microendoscopy in medial lumbar disc herniation, Minim. Invasive Neurosurg. 45 (2002) 139–141.
55
[9] P.C. Hsieh, C.H. Wang, Posterior endoscopic lumbar discectomy using a thoracoport as a tubular retractor, Minim. Invasive Neurosurg. 47 (2004) 319–323. [10] M. Fernandez-Fairen, P. Sala, H. Ramirez, J. Gil, A prospective randomized study of unilateral versus bilateral instrumented posterolateral lumbar fusion in degenerative spondylolisthesis, Spine (Phila Pa 1976) 32 (2007) 395–401. [11] N. Hayashi, T. Tamaki, H. Yamada, Experimental study of denervated muscle atrophy following severance of posterior rami of the lumbar spinal nerves, Spine (Phila Pa 1976) 17 (1992) 1361–1367. [12] H. Paajanen, M. Erkintalo, R. Parkkola, J. Salminen, M. Kormano, Age-dependent correlation of low-back pain and lumbar disc regeneration, Arch. Orthop. Trauma Surg. 116 (1997) 106–107. [13] F.R. Haller, F.N. Low, The fine structure of the peripheral nerve root sheath in the subarachnoid space in the rat and other laboratory animals, Am. J. Anat. 131 (1971) 1–19. [14] W.W. Parke, R. Watanabe, The intrinsic vasculature of the lumbosacral spinal nerve roots, Spine (Phila Pa 1976) 10 (1985) 508–515. [15] H. Matsui, H. Kitagawa, Y. Kawaguchi, H. Tsuji, Physiologic changes of nerve root during posterior lumbar discectomy, Spine (Phila Pa 1976) 20 (1995) 654–659. [16] Z.M. Cui, W.D. Li, G.F. Bao, G.H. Xu, Y.Y. Sun, L.L. Wang, L.Y. Zhu, Study of nerve root traction injury in lumbar interbody fusion from posterior rout approach, Orthop. J. China 21 (2008) 1619–1621. [17] R.K. Bindal, S. Ghosh, Intraoperative electromyography monitoring in minimally invasive transforaminal lumbar interbody fusion, J. Neurosurg. Spine 6 (2007) 126–132. [18] I CH Macnab, C.M. Godfrey, The incidence of denervation of the sacrospinales muscles following spinal surgery, Spine 2 (1977) 294–298. [19] H. Yoshizawa, S. Kobayashi, T. Morita, Chronic nerve root compression. Pathophysiologic mechanism of nerve root dysfunction, Spine (Phila Pa 1976) 20 (1995) 397–407.