- Email: [email protected]
Mini-open spinal column shortening for the treatment of adult tethered cord syndrome
Journal of Clinical Neuroscience xxx (2017) xxx–xxx
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Technical note
Mini-open spinal column shortening for the treatment of adult tethered cord syndrome Michael M. Safaee ⇑, Ethan A. Winkler, Dean Chou Department of Neurological Surgery, University of California, San Francisco, United States
a r t i c l e
i n f o
Article history: Received 22 April 2017 Accepted 21 July 2017 Available online xxxx Keywords: Tethered cord syndrome Spinal column shortening Minimally invasive
a b s t r a c t Tethered cord syndrome (TCS) is a challenging entity characterized by adhesions at the caudal spinal cord that prevent upward movement during growth and result in stretching of the cord with a concomitant constellation of neurologic symptoms. Although growth in height stops in adulthood, some patients still develop progressive symptoms; many underwent detethering as a child or adolescent, resulting in significant scar tissue and re-tethering. Recent strategies have focused on spinal column shortening to reduce tension on the spinal cord without exposing the previous de-tethering site. Mini-open and minimally invasive approaches avoid the large dissection and exposure associated with traditional approaches and are associated with reduced blood loss, shorter hospital stay, and similar outcomes when compared to conventional open approaches. We describe a technique for mini-open spinal column shortening. Using intraoperative navigation pedicle screws were placed at T10, T11, L1, and L2. A mini-open 3column ‘‘egg shell” decancellation osteotomy of T12 was performed through a transpedicular approach with preservation of the superior and inferior endplates. This procedure was performed on a 28 year old male with recurrent TCS and neurogenic bladder. Postoperative imaging showed a reduction in spinal column length of 1.5 cm and evidence of decreased tension on the spinal cord. At last follow-up he was recovering well with improved urinary function. Spinal column shortening for adult TCS can be safely achieved through a mini-open approach. Future studies should compare the efficacy of this technique to both traditional de-tethering and open spinal column shortening. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction Tethered cord syndrome (TCS) is a common form of spinal dysraphism in which adhesions at the caudal spinal cord prevent upward movement of the cord during growth. Although this commonly can be tethered by the filum terminale itself, many times, a lipoma is associated with the spinal cord and anchors the spinal cord in an aberrant caudal position. In the growing spinal column, this tether prevents the spinal cord from ascending to its normal position in adulthood, resulting in spinal cord dysfunction as the patient grows. In the adult, however, there no longer is any further growth of the spinal column, but many times, adult will nonetheless have progressive worsening symptoms despite de-tethering years or decades ago as a child. The progressive symptoms occur (despite no further growth of the patient) because daily normal motion of flexion, extension, and bending slowly pull and tug on ⇑ Corresponding author at: Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Ave. Room M779, San Francisco, CA 94143, United States. E-mail address: [email protected] (M.M. Safaee).
the tethered, resulting in dysfunction. Thus, even without growth of the spinal column, the tethered cord can result in symptoms because of the tension of the spinal cord, especially if scar tissue progressively thickens and becomes less compliant. This anomaly results in abnormal stretching of the spinal cord that causes progressive symptoms including pain, motor or sensory dysfunction, and bowel or bladder dysfunction. For decades, standard treatment has involved microsurgical detethering of neural elements, with recurrence in nearly half of patients [1–8]. Furthermore, revision surgical de-tethering for recurrent TCS has a high risk of complications including neurologic injury, cerebrospinal fluid (CSF) leak, and impaired wound healing [3,4,9,10]. This is because the spinal cord itself often times must be dissected off the dura, which can cause dysfunction and damage because the spinal cord is adherent to the dura. Moreover, the lower lumbar wound is often abnormal from the patient’s prior surgery or dysraphism. This allows for poor wound healing and a higher risk of CSF leak postoperatively. Because of the abnormal blood supply and poor wound healing to this local tissue, the risk of infection is also a concern. In addition, after revision de-tethering, the spinal cord may simply retether again because of the scar tissue and inflammation from sur-
http://dx.doi.org/10.1016/j.jocn.2017.07.037 0967-5868/Ó 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
2
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx
gery, resulting in the patient having the same symptoms as before surgery. Thus, revision surgical de-tethering remains a suboptimal surgical option for adult patients with TCS who have had prior detethering with a spinal cord adhered to the dura. Spinal column shortening in adults represents an alternative to the morbidity of detethering for patients with TCS. Kokubun [11] first reported a case of spinal shortening as a treatment for lowlying conus medullaris, which was followed by Güven et al. [12] who described a transpedicular decancellation osteotomy in patients who had undergone multiple surgeries with postlaminectomy kyphosis and fibrosis-related tethered cord. In a cadaveric model, Grande et al. [13] showed that shortening the spinal column through a thoracolumbar osteotomy reduced tension on the
spinal cord, lumbosacral nerve roots, and filum terminale. Hsieh et al. [14] reported on the use of vertebral column resection (VCR) in two patients with multiply recurrent TCS with good outcomes at over 12 months in each case. However, all these manuscripts reported on standard, open procedures, not minimally invasive or mini-open ones. Minimally invasive surgery (MIS) techniques have increased in popularity given comparable outcomes with traditional open approaches [15–25]. In addition, they are associated with less blood loss and shorter length of stay [26,27]. Mini-open approaches are a hybrid of true MIS and open surgery in that the surgeries are carried out with less tissue dissection, but not necessarily through a tube. We have used the mini-open approach to perform spinal column shortening in the adult for TCS, decreasing the muscular dissection and morbidity associated with the procedure. We report the use of a mini-open VCR in an adult patient with TCS who had a de-tethering as a child. This approach provides a similar reduction in vertebrae height with a less invasive procedure and potential for lower blood loss, shorter operative time, and less morbidity by decreasing the amount of paraspinal muscular dissection.
2. Methods 2.1. Surgical procedure
Fig. 1. Preoperative MRI in an adult presenting with recurrent tethered cord syndrome. T2-weighted MRI shows the spinal cord tethered at the S1–S2 level with an associated lipoma. The patient underwent L3–S1 laminectomies for excision of this lipoma and untethering of the spinal cord 15 years prior to this MRI, but developed worsening urinary symptoms prompting neurosurgical evaluation.
After induction of general anesthesia the patient was placed prone on a Jackson table. The T12 level was localized by X-ray and a single skin incision only was made down the midline from approximately T10 to L2, but the fascia was left intact (Fig. 2A). A reference arc was placed on the L3 spinous process and an intraoperative O-Arm spin with Stealth navigation (Medtronic, Memphis, TN) was performed for registration of navigation. Intraoperative navigation was used to identify the entry points through the fascia for the pedicle screw placement. Pedicle screw entry sites were drilled and tapped using navigation guidance through the fascia. K-wires were then placed into the pedicles of T10, T11, L1, and L2 and used to dilate the soft tissue overlying the facets at these levels with a minimally invasive retractor tube system (MetRx, Medtronic, Memphis, TN). Facet location was confirmed by intraoperative Stealth navigation (Fig. 2B). Facets were denuded with monopolar cautery then drilled with a high speed burr followed by placement of allograft to facilitate facet arthrodesis (Fig. 2C). Pedicle screws were percutaneously placed at T10, T11, L1, and L2 with placement confirmed by intraoperative Oarm. The fascia overlying T11-12 and T12-L1 was then opened to
Fig. 2. Intraoperative photographs for mini-open spinal column shortening. For T12 spinal column shortening, a single skin incision is made down the midline from approximately T10 to L2 with the fascia left intact except at the level of the VCR (A). An intraoperative O-Arm spine is performed to facilitate Stealth navigation for pedicle screw placement and facet localization (B). K-wires placed in the pedicles at the levels above and below the VCR are used to dilate the soft tissue over the facets at these levels with a minimally invasive retractor tube system. Facets are denuded with monopolar cautery and drilled with a high speed burr (C). Allograft is then placed to facilitate facet arthrodesis.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx
3
perform laminectomies at T11-12 and T12-L1 to allow for decompression of the spinal cord, conus medullaris, and adjacent neural elements. A 3-column ‘‘egg shell” decancellation osteotomy of T12 was performed by first removing the pedicles of T12. Cancellous bone within the vertebral body was removed and the 3column osteotomy was completed through this technique, preserving the superior and inferior endplates of T12. The posterior longitudinal ligament was identified and removed. Temporary rods were placed to prevent collapse and the posterior cortex of the vertebral body was removed with a central pedicle subtraction osteotomy central impactor. The osteotomy was closed with an approximate shortening of 1.5 cm. Motor evoked potential were stable throughout closure of the osteotomy. Permanent rods were secured in place and posterolateral arthrodesis was performed from T10 to L2 using local autograft bone. Bone graft was placed into the osteotomy site itself to ensure no gap in the osteotomy after closure. The fascia and skin were closed in the usual fashion after epidural drains were left in place. The technique is summarized in Supplemental Video 1. 2.2. Clinical history The patient is a 28 year old male who initially presented with leg length discrepancy at age 12. Subsequent MRI scans revealed a large lumbosacral lipoma and tethered cord. He underwent sacral laminectomies for excision of this lipoma and untethering of the spinal cord at age 12 without complication and was doing well for 15 years. At age 27, he presented with 12 months of progressively worsening back pain and urinary frequency and urgency. MRI at this time showed the spinal cord tethering at the S1-2 level with an associated lipoma (Fig. 1). He had normal bowel and sexual function but began to lose control of his urination. Urodynamic studies were consistent with neurogenic bladder and after a lengthy discussion of the risks, benefits, and alternatives, the patient elected to undergo surgical treatment. Because of the prior scar tissue and morbidity associated with revision de-tethering, a mini-open spinal column shortening was planned at T12, away from the prior surgical site.
Fig. 3. Postoperative standing X-rays after mini-open spinal column shortening. Preoperative (A) and postoperative (B) standing 36-inch X-rays show good alignment of spinal implants and a significant reduction in the height of the T12 vertebrae.
3. Results 3.1. Postoperative course The patient tolerated this procedure well and was discharged in good condition. Postoperative standing 36-inch X-ray showed good implant alignment with an over 50% reduction in the height of the T12 vertebral body based on a preoperative height 30 mm compared to 13.5 mm measured at the midpoint of the vertebral body (Fig. 3). Postoperative CT confirmed significant reduction in the height of the T12 vertebral body (Fig. 4A); postoperative MRI showed persistent tethering of the spinal cord, but a subtle decrease in the T2 signal (Fig. 4B). Six months following his operation, the patient reported significant improvement in his urinary function with improved urgency and only intermittent elective straight catheterization. His lower extremity strength and sensation remained intact. Repeat imaging demonstrated good spinal alignment with shortening of the spinal column. 4. Discussion The surgical management of adult TCS is challenging, particularly in cases of re-tethering. Without intervention, patients usually experience progressive neurologic decline; [4,7,28] however, repeat attempts at de-tethering carry significant morbidity due to scarring and arachnoid adhesions from prior surgery and associ-
Fig. 4. Postoperative imaging after mini-open spinal column shortening. Midline sagittal CT scan shows significant reduction in height of the T12 vertebral body (A). Postoperative T2-weighted MRI shows persistent tethering of the spinal cord at the S1–S2 level with a subtle reduction in T2 signal (B).
ated with increased risk of CSF leak, pseudomeningocele, wound complications, infection, neurologic injury, and recurrent tethering [5,6,9,29]; Moreover, revision de-tethering is extremely morbid because the distal portion of the spinal cord itself is actually dis-
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
4
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx
sected off the dura; this invariably results in some type of neurologic damage from the removal of the spinal cord off the dura. Patients should be prepared to have worsening function after revision de-tethering before noticing any improvement or any halt in the progressive symptoms. The rationale for VCR for spinal column shortening is based on cadaveric studies showing that a decrease in vertebral column height by 20–25 mm resulted in a significant reduction in tension of the sacral nerve roots and filum terminale [13,30]. Grande et al. found that greater than 90% of tethered neural elements must be released during a traditional detethering operation to achieve similar reductions in tension compared to a VCR [13]. Such a dissection of this much of the distal cord invariably has a very high risk of neurologic damage because many times, the cord itself does not freely dissect off the dura; rather, a thin layer of spinal cord is left on the dura and the rest of the cord is removed off this outer layer of the spinal cord. In addition, even if it is dissected off the dura, the manipulation of the cord itself to this degree usually results in some component of neurologic damage. Thus, the VCR provides a viable alternate to surgical detethering, particularly in cases of recurrent TCS where the surgery will carry unacceptably high morbidity. Previous reports on the use of spinal column shortening for treatment of adult TCS have utilized an open surgical approach [11,12,14]. The uniqueness of our technique is that we have taken this one step further and performed the same operation with a mini-open technique. We have previously described our experience with mini-open approaches for vertebral corpectomy [31– 35] and shown that a mini-open approach provides the advantage of reduced blood loss, shorter hospital stay, and a trend toward lower perioperative complications and infection without difference in operative time or long-term neurologic outcomes for patients with metastatic spinal tumors [36]. In addition, we have also shown that the mini-open VCR for spinal deformity is a feasible technique and an option in patients with kyphosis [32]. For select adult patients with TCS, the mini-open approach has the potential to allow for safe and effective treatment for this challenging entity. There has been significant growth in MIS techniques as the technology improves and more data emerges to support their role in managing both simple and complex spinal disorders. In a systematic review of 602 patients with spondylolisthesis, Lu et al. showed that MIS was associated with less blood loss and shorter length of stay with no difference in functional or pain outcomes [37]. Furthermore, Singh et al. showed that MIS transforaminal lumbar interbody fusion (TLIF) was associated with shorter operative time, length of stay, anesthesia time, visual analog scale (VAS) scores, blood loss, and hospital costs when compared to an open technique [38]. These findings were corroborated by a large systematic review performed by Goldstein et al. containing over 8000 patients that demonstrated improved perioperative outcomes including operative time, blood loss, and length of stay with no difference in patient-reported outcomes or complication rates [39]. In an analysis of over 100,000 cases from the Scoliosis Research Society Morbidity and Mortality Committee, Smith et al. found that MIS was associated with a lower infection rate for both lumbar discectomy and TLIF when compared to traditional open techniques [40]. Beyond the immediate advantages of MIS such as less muscle dissection and faster recovery, Djurasovic et al. showed that these benefits extend beyond the perioperative period with MIS TLIF patients showing greater improvements in Oswestry Disability Index (ODI) at 1 year and greater improvements in both pain and ODI at 2 years compared to a propensity-matched cohort of patients who underwent open TLIF [41]. The advantages of MIS may not extend across all disease processes; for example in patients with adult degenerative scoliosis, MIS was associated with reduced costs, blood loss, and hospital stay, however open surgery showed a greater improvement in VAS scores, deformity correc-
tion, and sagittal balance [42]. Interestingly, a study by Hamilton et al. with the international Spine Study group found reoperation rates among MIS and open groups were similar, however hybrid procedures (MIS interbody fusion with open posterior segmental fixation) had a higher incidence of reoperation [43]. In this manuscript, we present a novel mini-open spinal column shortening for the treatment of adult tethered cord syndrome. This operation effectively translates into a minimally invasive technique for spinal column shortening, which has shown to be effective for cases of recurrent TCS and represents a less morbid alternative to microscopic revision de-tethering. This technique also highlights the evolution of MIS and mini-open procedures as these tools and their applications continue to expand. Over time we hope to refine this technique and assess long term clinical outcomes in more patients, particularly compared to traditional detethering and open spinal column shortening. 5. Conclusion TCS represents a challenging clinical entity, particularly in adults with recurrent TCS. Traditional surgical treatment consists of revision de-tethering and carries a high morbidity and concomitant complications. More recent strategies have focused on vertebral column resection and spinal column shortening. In this manuscript we present a novel adaptation of this procedure with a safe and effective means for spinal column shortening with the potential for less blood loss, shorter hospital stay, and less tissue dissection and damage. This manuscript is intended to be a description of the technique, not an outcomes study. Additional studies are needed validate this technique and compare long term results with those of traditional open spinal column shortening and microscopic revision de-tethering to demonstrate the ideal surgical modality for the treatment of adult TCS. Conflict of interest None. Disclosure of funding None. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jocn.2017.07.037. References [1] Archibeck MJ, Smith JT, Carroll KL, et al. Surgical release of tethered spinal cord: survivorship analysis and orthopedic outcome. J Pediatr Orthop 1997;17:773–6. [2] Filler AG, Britton JA, Uttley D, et al. Adult postrepair myelomeningocoele and tethered cord syndrome: good surgical outcome after abrupt neurological decline. Br J Neurosurg 1995;9:659–66. [3] Herman JM, McLone DG, Storrs BB, et al. Analysis of 153 patients with myelomeningocele or spinal lipoma reoperated upon for a tethered cord. Presentation, management and outcome. Pediatr Neurosurg 1993;19:243–9. [4] Kang JK, Lee KS, Jeun SS, et al. Role of surgery for maintaining urological function and prevention of retethering in the treatment of lipomeningomyelocele: experience recorded in 75 lipomeningomyelocele patients. Childs Nerv Syst 2003;19:23–9. [5] Lagae L, Verpoorten C, Casaer P, et al. Conservative versus neurosurgical treatment of tethered cord patients. Z Kinderchir 1990;45(Suppl 1):16–7. [6] Lee TT, Arias JM, Andrus HL, et al. Progressive posttraumatic myelomalacic myelopathy: treatment with untethering and expansive duraplasty. J Neurosurg 1997;86:624–8. [7] Lew SM, Kothbauer KF. Tethered cord syndrome: an updated review. Pediatr Neurosurg 2007;43:236–48.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx [8] Morimoto K, Takemoto O, Wakayama A. Spinal lipomas in children–surgical management and long-term follow-up. Pediatr Neurosurg 2005;41:84–7. [9] Maher CO, Goumnerova L, Madsen JR, et al. Outcome following multiple repeated spinal cord untethering operations. J Neurosurg 2007;106:434–8. [10] Schoenmakers MA, Gooskens RH, Gulmans VA, et al. Long-term outcome of neurosurgical untethering on neurosegmental motor and ambulation levels. Dev Med Child Neurol 2003;45:551–5. [11] Kokubun S. Shortening spinal osteotomy for tethered cord syndrome in adults. Spine Spinal Cord 1995;8. [12] Guven O, Bezer M, Gokkus K, et al. Transpedicular decancellation osteotomy in the treatment of peridural fibrosis. Arch Orthop Trauma Surg 2001;121:517–20. [13] Grande AW, Maher PC, Morgan CJ, et al. Vertebral column subtraction osteotomy for recurrent tethered cord syndrome in adults: a cadaveric study. J Neurosurg Spine 2006;4:478–84. [14] Hsieh PC, Ondra SL, Grande AW, et al. Posterior vertebral column subtraction osteotomy: a novel surgical approach for the treatment of multiple recurrences of tethered cord syndrome. J Neurosurg Spine 2009;10:278–86. [15] Kepler CK, Yu AL, Gruskay JA, et al. Comparison of open and minimally invasive techniques for posterior lumbar instrumentation and fusion after open anterior lumbar interbody fusion. Spine J 2013;13:489–97. [16] McAnany SJ, Overley SC, Kim JS, et al. Open versus minimally invasive fixation techniques for thoracolumbar trauma: a meta-analysis. Global Spine J 2016;6:186–94. [17] German JW, Adamo MA, Hoppenot RG, et al. Perioperative results following lumbar discectomy: comparison of minimally invasive discectomy and standard microdiscectomy. Neurosurg Focus 2008;25:E20. [18] Holly LT, Schwender JD, Rouben DP, et al. Minimally invasive transforaminal lumbar interbody fusion: indications, technique, and complications. Neurosurg Focus 2006;20:E6. [19] Lau D, Lee JG, Han SJ, et al. Complications and perioperative factors associated with learning the technique of minimally invasive transforaminal lumbar interbody fusion (TLIF). J Clin Neurosci 2011;18:624–7. [20] Ntoukas V, Muller A. Minimally invasive approach versus traditional open approach for one level posterior lumbar interbody fusion. Minim Invasive Neurosurg 2010;53:21–4. [21] Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine (Phila Pa 1976) 2007;32:537–43. [22] Peng CW, Yue WM, Poh SY, et al. Clinical and radiological outcomes of minimally invasive versus open transforaminal lumbar interbody fusion. Spine (Phila Pa 1976) 2009;34:1385–9. [23] Rahman M, Summers LE, Richter B, et al. Comparison of techniques for decompressive lumbar laminectomy: the minimally invasive versus the ‘‘classic” open approach. Minim Invasive Neurosurg 2008;51:100–5. [24] Schizas C, Tzinieris N, Tsiridis E, et al. Minimally invasive versus open transforaminal lumbar interbody fusion: evaluating initial experience. Int Orthop 2009;33:1683–8. [25] Wu RH, Fraser JF, Hartl R. Minimal access versus open transforaminal lumbar interbody fusion: meta-analysis of fusion rates. Spine (Phila Pa 1976) 2010;35:2273–81.
5
[26] Uribe JS, Deukmedjian AR, Mummaneni PV, et al. Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques. Neurosurg Focus 2014;36:E15. [27] Goldstein CL, Macwan K, Sundararajan K, et al. Perioperative outcomes and adverse events of minimally invasive versus open posterior lumbar fusion: meta-analysis and systematic review. J Neurosurg Spine 2016;24:416–27. [28] Agarwalla PK, Dunn IF, Scott RM, et al. Tethered cord syndrome. Neurosurg Clin N Am 2007;18:531–47. [29] Paradiso G, Lee GY, Sarjeant R, et al. Multi-modality neurophysiological monitoring during surgery for adult tethered cord syndrome. J Clin Neurosci 2005;12:934–6. [30] Yamada S, Iacono RP, Andrade T, et al. Pathophysiology of tethered cord syndrome. Neurosurg Clin N Am 1995;6:311–23. [31] Chou D, Eltgroth M, Yang I, et al. Rib head disarticulation for multilevel transpedicular thoracic corpectomies and expandable cage reconstruction. Neurol India 2009;57:469–74. [32] Chou D, Lau D, Roy E. Feasibility of the mini-open vertebral column resection for severe thoracic kyphosis. J Clin Neurosci 2014;21:841–5. [33] Chou D, Lu DC. Mini-open transpedicular corpectomies with expandable cage reconstruction. Technical note. J Neurosurg Spine 2011;14:71–7. [34] Chou D, Wang VY. Trap-door rib-head osteotomies for posterior placement of expandable cages after transpedicular corpectomy: an alternative to lateral extracavitary and costotransversectomy approaches. J Neurosurg Spine 2009;10:40–5. [35] Chou D, Wang VY, Gupta N. Transpedicular corpectomy with posterior expandable cage placement for L1 burst fracture. J Clin Neurosci 2009;16:1069–72. [36] Lau D, Chou D. Posterior thoracic corpectomy with cage reconstruction for metastatic spinal tumors: comparing the mini-open approach to the open approach. J Neurosurg Spine 2015;23:217–27. [37] Lu VM, Kerezoudis P, Gilder HE, et al. Minimally invasive surgery versus open surgery spinal fusion for spondylolisthesis: a systematic review and metaanalysis. (Spine Phila Pa 1976) 2016. [38] Singh K, Nandyala SV, Marquez-Lara A, et al. A perioperative cost analysis comparing single-level minimally invasive and open transforaminal lumbar interbody fusion. Spine J 2014;14:1694–701. [39] Goldstein CL, Phillips FM, Rampersaud YR. Comparative effectiveness and economic evaluations of open versus minimally invasive posterior or transforaminal lumbar interbody fusion: a systematic review. Spine (Phila Pa 1976) 2016;41(Suppl 8):S74–89. [40] Smith JS, Shaffrey CI, Sansur CA, et al. Rates of infection after spine surgery based on 108,419 procedures: a report from the Scoliosis Research Society Morbidity and Mortality Committee. Spine (Phila Pa 1976) 2011;36:556–63. [41] Djurasovic M, Rouben DP, Glassman SD, et al. Clinical outcomes of minimally invasive versus open TLIF: a propensity-matched cohort study. Am J Orthop (Belle Mead NJ). 2016;45:E77–82. [42] Uddin OM, Haque R, Sugrue PA, et al. Cost minimization in treatment of adult degenerative scoliosis. J Neurosurg Spine 2015;23:798–806. [43] Hamilton DK, Kanter AS, Bolinger BD, et al. Reoperation rates in minimally invasive, hybrid and open surgical treatment for adult spinal deformity with minimum 2-year follow-up. Eur Spine J 2016;25:2605–11.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
Contents lists available at ScienceDirect
Journal of Clinical Neuroscience journal homepage: www.elsevier.com/locate/jocn
Technical note
Mini-open spinal column shortening for the treatment of adult tethered cord syndrome Michael M. Safaee ⇑, Ethan A. Winkler, Dean Chou Department of Neurological Surgery, University of California, San Francisco, United States
a r t i c l e
i n f o
Article history: Received 22 April 2017 Accepted 21 July 2017 Available online xxxx Keywords: Tethered cord syndrome Spinal column shortening Minimally invasive
a b s t r a c t Tethered cord syndrome (TCS) is a challenging entity characterized by adhesions at the caudal spinal cord that prevent upward movement during growth and result in stretching of the cord with a concomitant constellation of neurologic symptoms. Although growth in height stops in adulthood, some patients still develop progressive symptoms; many underwent detethering as a child or adolescent, resulting in significant scar tissue and re-tethering. Recent strategies have focused on spinal column shortening to reduce tension on the spinal cord without exposing the previous de-tethering site. Mini-open and minimally invasive approaches avoid the large dissection and exposure associated with traditional approaches and are associated with reduced blood loss, shorter hospital stay, and similar outcomes when compared to conventional open approaches. We describe a technique for mini-open spinal column shortening. Using intraoperative navigation pedicle screws were placed at T10, T11, L1, and L2. A mini-open 3column ‘‘egg shell” decancellation osteotomy of T12 was performed through a transpedicular approach with preservation of the superior and inferior endplates. This procedure was performed on a 28 year old male with recurrent TCS and neurogenic bladder. Postoperative imaging showed a reduction in spinal column length of 1.5 cm and evidence of decreased tension on the spinal cord. At last follow-up he was recovering well with improved urinary function. Spinal column shortening for adult TCS can be safely achieved through a mini-open approach. Future studies should compare the efficacy of this technique to both traditional de-tethering and open spinal column shortening. Ó 2017 Elsevier Ltd. All rights reserved.
1. Introduction Tethered cord syndrome (TCS) is a common form of spinal dysraphism in which adhesions at the caudal spinal cord prevent upward movement of the cord during growth. Although this commonly can be tethered by the filum terminale itself, many times, a lipoma is associated with the spinal cord and anchors the spinal cord in an aberrant caudal position. In the growing spinal column, this tether prevents the spinal cord from ascending to its normal position in adulthood, resulting in spinal cord dysfunction as the patient grows. In the adult, however, there no longer is any further growth of the spinal column, but many times, adult will nonetheless have progressive worsening symptoms despite de-tethering years or decades ago as a child. The progressive symptoms occur (despite no further growth of the patient) because daily normal motion of flexion, extension, and bending slowly pull and tug on ⇑ Corresponding author at: Department of Neurological Surgery, University of California, San Francisco, 505 Parnassus Ave. Room M779, San Francisco, CA 94143, United States. E-mail address: [email protected] (M.M. Safaee).
the tethered, resulting in dysfunction. Thus, even without growth of the spinal column, the tethered cord can result in symptoms because of the tension of the spinal cord, especially if scar tissue progressively thickens and becomes less compliant. This anomaly results in abnormal stretching of the spinal cord that causes progressive symptoms including pain, motor or sensory dysfunction, and bowel or bladder dysfunction. For decades, standard treatment has involved microsurgical detethering of neural elements, with recurrence in nearly half of patients [1–8]. Furthermore, revision surgical de-tethering for recurrent TCS has a high risk of complications including neurologic injury, cerebrospinal fluid (CSF) leak, and impaired wound healing [3,4,9,10]. This is because the spinal cord itself often times must be dissected off the dura, which can cause dysfunction and damage because the spinal cord is adherent to the dura. Moreover, the lower lumbar wound is often abnormal from the patient’s prior surgery or dysraphism. This allows for poor wound healing and a higher risk of CSF leak postoperatively. Because of the abnormal blood supply and poor wound healing to this local tissue, the risk of infection is also a concern. In addition, after revision de-tethering, the spinal cord may simply retether again because of the scar tissue and inflammation from sur-
http://dx.doi.org/10.1016/j.jocn.2017.07.037 0967-5868/Ó 2017 Elsevier Ltd. All rights reserved.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
2
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx
gery, resulting in the patient having the same symptoms as before surgery. Thus, revision surgical de-tethering remains a suboptimal surgical option for adult patients with TCS who have had prior detethering with a spinal cord adhered to the dura. Spinal column shortening in adults represents an alternative to the morbidity of detethering for patients with TCS. Kokubun [11] first reported a case of spinal shortening as a treatment for lowlying conus medullaris, which was followed by Güven et al. [12] who described a transpedicular decancellation osteotomy in patients who had undergone multiple surgeries with postlaminectomy kyphosis and fibrosis-related tethered cord. In a cadaveric model, Grande et al. [13] showed that shortening the spinal column through a thoracolumbar osteotomy reduced tension on the
spinal cord, lumbosacral nerve roots, and filum terminale. Hsieh et al. [14] reported on the use of vertebral column resection (VCR) in two patients with multiply recurrent TCS with good outcomes at over 12 months in each case. However, all these manuscripts reported on standard, open procedures, not minimally invasive or mini-open ones. Minimally invasive surgery (MIS) techniques have increased in popularity given comparable outcomes with traditional open approaches [15–25]. In addition, they are associated with less blood loss and shorter length of stay [26,27]. Mini-open approaches are a hybrid of true MIS and open surgery in that the surgeries are carried out with less tissue dissection, but not necessarily through a tube. We have used the mini-open approach to perform spinal column shortening in the adult for TCS, decreasing the muscular dissection and morbidity associated with the procedure. We report the use of a mini-open VCR in an adult patient with TCS who had a de-tethering as a child. This approach provides a similar reduction in vertebrae height with a less invasive procedure and potential for lower blood loss, shorter operative time, and less morbidity by decreasing the amount of paraspinal muscular dissection.
2. Methods 2.1. Surgical procedure
Fig. 1. Preoperative MRI in an adult presenting with recurrent tethered cord syndrome. T2-weighted MRI shows the spinal cord tethered at the S1–S2 level with an associated lipoma. The patient underwent L3–S1 laminectomies for excision of this lipoma and untethering of the spinal cord 15 years prior to this MRI, but developed worsening urinary symptoms prompting neurosurgical evaluation.
After induction of general anesthesia the patient was placed prone on a Jackson table. The T12 level was localized by X-ray and a single skin incision only was made down the midline from approximately T10 to L2, but the fascia was left intact (Fig. 2A). A reference arc was placed on the L3 spinous process and an intraoperative O-Arm spin with Stealth navigation (Medtronic, Memphis, TN) was performed for registration of navigation. Intraoperative navigation was used to identify the entry points through the fascia for the pedicle screw placement. Pedicle screw entry sites were drilled and tapped using navigation guidance through the fascia. K-wires were then placed into the pedicles of T10, T11, L1, and L2 and used to dilate the soft tissue overlying the facets at these levels with a minimally invasive retractor tube system (MetRx, Medtronic, Memphis, TN). Facet location was confirmed by intraoperative Stealth navigation (Fig. 2B). Facets were denuded with monopolar cautery then drilled with a high speed burr followed by placement of allograft to facilitate facet arthrodesis (Fig. 2C). Pedicle screws were percutaneously placed at T10, T11, L1, and L2 with placement confirmed by intraoperative Oarm. The fascia overlying T11-12 and T12-L1 was then opened to
Fig. 2. Intraoperative photographs for mini-open spinal column shortening. For T12 spinal column shortening, a single skin incision is made down the midline from approximately T10 to L2 with the fascia left intact except at the level of the VCR (A). An intraoperative O-Arm spine is performed to facilitate Stealth navigation for pedicle screw placement and facet localization (B). K-wires placed in the pedicles at the levels above and below the VCR are used to dilate the soft tissue over the facets at these levels with a minimally invasive retractor tube system. Facets are denuded with monopolar cautery and drilled with a high speed burr (C). Allograft is then placed to facilitate facet arthrodesis.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx
3
perform laminectomies at T11-12 and T12-L1 to allow for decompression of the spinal cord, conus medullaris, and adjacent neural elements. A 3-column ‘‘egg shell” decancellation osteotomy of T12 was performed by first removing the pedicles of T12. Cancellous bone within the vertebral body was removed and the 3column osteotomy was completed through this technique, preserving the superior and inferior endplates of T12. The posterior longitudinal ligament was identified and removed. Temporary rods were placed to prevent collapse and the posterior cortex of the vertebral body was removed with a central pedicle subtraction osteotomy central impactor. The osteotomy was closed with an approximate shortening of 1.5 cm. Motor evoked potential were stable throughout closure of the osteotomy. Permanent rods were secured in place and posterolateral arthrodesis was performed from T10 to L2 using local autograft bone. Bone graft was placed into the osteotomy site itself to ensure no gap in the osteotomy after closure. The fascia and skin were closed in the usual fashion after epidural drains were left in place. The technique is summarized in Supplemental Video 1. 2.2. Clinical history The patient is a 28 year old male who initially presented with leg length discrepancy at age 12. Subsequent MRI scans revealed a large lumbosacral lipoma and tethered cord. He underwent sacral laminectomies for excision of this lipoma and untethering of the spinal cord at age 12 without complication and was doing well for 15 years. At age 27, he presented with 12 months of progressively worsening back pain and urinary frequency and urgency. MRI at this time showed the spinal cord tethering at the S1-2 level with an associated lipoma (Fig. 1). He had normal bowel and sexual function but began to lose control of his urination. Urodynamic studies were consistent with neurogenic bladder and after a lengthy discussion of the risks, benefits, and alternatives, the patient elected to undergo surgical treatment. Because of the prior scar tissue and morbidity associated with revision de-tethering, a mini-open spinal column shortening was planned at T12, away from the prior surgical site.
Fig. 3. Postoperative standing X-rays after mini-open spinal column shortening. Preoperative (A) and postoperative (B) standing 36-inch X-rays show good alignment of spinal implants and a significant reduction in the height of the T12 vertebrae.
3. Results 3.1. Postoperative course The patient tolerated this procedure well and was discharged in good condition. Postoperative standing 36-inch X-ray showed good implant alignment with an over 50% reduction in the height of the T12 vertebral body based on a preoperative height 30 mm compared to 13.5 mm measured at the midpoint of the vertebral body (Fig. 3). Postoperative CT confirmed significant reduction in the height of the T12 vertebral body (Fig. 4A); postoperative MRI showed persistent tethering of the spinal cord, but a subtle decrease in the T2 signal (Fig. 4B). Six months following his operation, the patient reported significant improvement in his urinary function with improved urgency and only intermittent elective straight catheterization. His lower extremity strength and sensation remained intact. Repeat imaging demonstrated good spinal alignment with shortening of the spinal column. 4. Discussion The surgical management of adult TCS is challenging, particularly in cases of re-tethering. Without intervention, patients usually experience progressive neurologic decline; [4,7,28] however, repeat attempts at de-tethering carry significant morbidity due to scarring and arachnoid adhesions from prior surgery and associ-
Fig. 4. Postoperative imaging after mini-open spinal column shortening. Midline sagittal CT scan shows significant reduction in height of the T12 vertebral body (A). Postoperative T2-weighted MRI shows persistent tethering of the spinal cord at the S1–S2 level with a subtle reduction in T2 signal (B).
ated with increased risk of CSF leak, pseudomeningocele, wound complications, infection, neurologic injury, and recurrent tethering [5,6,9,29]; Moreover, revision de-tethering is extremely morbid because the distal portion of the spinal cord itself is actually dis-
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
4
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx
sected off the dura; this invariably results in some type of neurologic damage from the removal of the spinal cord off the dura. Patients should be prepared to have worsening function after revision de-tethering before noticing any improvement or any halt in the progressive symptoms. The rationale for VCR for spinal column shortening is based on cadaveric studies showing that a decrease in vertebral column height by 20–25 mm resulted in a significant reduction in tension of the sacral nerve roots and filum terminale [13,30]. Grande et al. found that greater than 90% of tethered neural elements must be released during a traditional detethering operation to achieve similar reductions in tension compared to a VCR [13]. Such a dissection of this much of the distal cord invariably has a very high risk of neurologic damage because many times, the cord itself does not freely dissect off the dura; rather, a thin layer of spinal cord is left on the dura and the rest of the cord is removed off this outer layer of the spinal cord. In addition, even if it is dissected off the dura, the manipulation of the cord itself to this degree usually results in some component of neurologic damage. Thus, the VCR provides a viable alternate to surgical detethering, particularly in cases of recurrent TCS where the surgery will carry unacceptably high morbidity. Previous reports on the use of spinal column shortening for treatment of adult TCS have utilized an open surgical approach [11,12,14]. The uniqueness of our technique is that we have taken this one step further and performed the same operation with a mini-open technique. We have previously described our experience with mini-open approaches for vertebral corpectomy [31– 35] and shown that a mini-open approach provides the advantage of reduced blood loss, shorter hospital stay, and a trend toward lower perioperative complications and infection without difference in operative time or long-term neurologic outcomes for patients with metastatic spinal tumors [36]. In addition, we have also shown that the mini-open VCR for spinal deformity is a feasible technique and an option in patients with kyphosis [32]. For select adult patients with TCS, the mini-open approach has the potential to allow for safe and effective treatment for this challenging entity. There has been significant growth in MIS techniques as the technology improves and more data emerges to support their role in managing both simple and complex spinal disorders. In a systematic review of 602 patients with spondylolisthesis, Lu et al. showed that MIS was associated with less blood loss and shorter length of stay with no difference in functional or pain outcomes [37]. Furthermore, Singh et al. showed that MIS transforaminal lumbar interbody fusion (TLIF) was associated with shorter operative time, length of stay, anesthesia time, visual analog scale (VAS) scores, blood loss, and hospital costs when compared to an open technique [38]. These findings were corroborated by a large systematic review performed by Goldstein et al. containing over 8000 patients that demonstrated improved perioperative outcomes including operative time, blood loss, and length of stay with no difference in patient-reported outcomes or complication rates [39]. In an analysis of over 100,000 cases from the Scoliosis Research Society Morbidity and Mortality Committee, Smith et al. found that MIS was associated with a lower infection rate for both lumbar discectomy and TLIF when compared to traditional open techniques [40]. Beyond the immediate advantages of MIS such as less muscle dissection and faster recovery, Djurasovic et al. showed that these benefits extend beyond the perioperative period with MIS TLIF patients showing greater improvements in Oswestry Disability Index (ODI) at 1 year and greater improvements in both pain and ODI at 2 years compared to a propensity-matched cohort of patients who underwent open TLIF [41]. The advantages of MIS may not extend across all disease processes; for example in patients with adult degenerative scoliosis, MIS was associated with reduced costs, blood loss, and hospital stay, however open surgery showed a greater improvement in VAS scores, deformity correc-
tion, and sagittal balance [42]. Interestingly, a study by Hamilton et al. with the international Spine Study group found reoperation rates among MIS and open groups were similar, however hybrid procedures (MIS interbody fusion with open posterior segmental fixation) had a higher incidence of reoperation [43]. In this manuscript, we present a novel mini-open spinal column shortening for the treatment of adult tethered cord syndrome. This operation effectively translates into a minimally invasive technique for spinal column shortening, which has shown to be effective for cases of recurrent TCS and represents a less morbid alternative to microscopic revision de-tethering. This technique also highlights the evolution of MIS and mini-open procedures as these tools and their applications continue to expand. Over time we hope to refine this technique and assess long term clinical outcomes in more patients, particularly compared to traditional detethering and open spinal column shortening. 5. Conclusion TCS represents a challenging clinical entity, particularly in adults with recurrent TCS. Traditional surgical treatment consists of revision de-tethering and carries a high morbidity and concomitant complications. More recent strategies have focused on vertebral column resection and spinal column shortening. In this manuscript we present a novel adaptation of this procedure with a safe and effective means for spinal column shortening with the potential for less blood loss, shorter hospital stay, and less tissue dissection and damage. This manuscript is intended to be a description of the technique, not an outcomes study. Additional studies are needed validate this technique and compare long term results with those of traditional open spinal column shortening and microscopic revision de-tethering to demonstrate the ideal surgical modality for the treatment of adult TCS. Conflict of interest None. Disclosure of funding None. Appendix A. Supplementary data Supplementary data associated with this article can be found, in the online version, at http://dx.doi.org/10.1016/j.jocn.2017.07.037. References [1] Archibeck MJ, Smith JT, Carroll KL, et al. Surgical release of tethered spinal cord: survivorship analysis and orthopedic outcome. J Pediatr Orthop 1997;17:773–6. [2] Filler AG, Britton JA, Uttley D, et al. Adult postrepair myelomeningocoele and tethered cord syndrome: good surgical outcome after abrupt neurological decline. Br J Neurosurg 1995;9:659–66. [3] Herman JM, McLone DG, Storrs BB, et al. Analysis of 153 patients with myelomeningocele or spinal lipoma reoperated upon for a tethered cord. Presentation, management and outcome. Pediatr Neurosurg 1993;19:243–9. [4] Kang JK, Lee KS, Jeun SS, et al. Role of surgery for maintaining urological function and prevention of retethering in the treatment of lipomeningomyelocele: experience recorded in 75 lipomeningomyelocele patients. Childs Nerv Syst 2003;19:23–9. [5] Lagae L, Verpoorten C, Casaer P, et al. Conservative versus neurosurgical treatment of tethered cord patients. Z Kinderchir 1990;45(Suppl 1):16–7. [6] Lee TT, Arias JM, Andrus HL, et al. Progressive posttraumatic myelomalacic myelopathy: treatment with untethering and expansive duraplasty. J Neurosurg 1997;86:624–8. [7] Lew SM, Kothbauer KF. Tethered cord syndrome: an updated review. Pediatr Neurosurg 2007;43:236–48.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037
M.M. Safaee et al. / Journal of Clinical Neuroscience xxx (2017) xxx–xxx [8] Morimoto K, Takemoto O, Wakayama A. Spinal lipomas in children–surgical management and long-term follow-up. Pediatr Neurosurg 2005;41:84–7. [9] Maher CO, Goumnerova L, Madsen JR, et al. Outcome following multiple repeated spinal cord untethering operations. J Neurosurg 2007;106:434–8. [10] Schoenmakers MA, Gooskens RH, Gulmans VA, et al. Long-term outcome of neurosurgical untethering on neurosegmental motor and ambulation levels. Dev Med Child Neurol 2003;45:551–5. [11] Kokubun S. Shortening spinal osteotomy for tethered cord syndrome in adults. Spine Spinal Cord 1995;8. [12] Guven O, Bezer M, Gokkus K, et al. Transpedicular decancellation osteotomy in the treatment of peridural fibrosis. Arch Orthop Trauma Surg 2001;121:517–20. [13] Grande AW, Maher PC, Morgan CJ, et al. Vertebral column subtraction osteotomy for recurrent tethered cord syndrome in adults: a cadaveric study. J Neurosurg Spine 2006;4:478–84. [14] Hsieh PC, Ondra SL, Grande AW, et al. Posterior vertebral column subtraction osteotomy: a novel surgical approach for the treatment of multiple recurrences of tethered cord syndrome. J Neurosurg Spine 2009;10:278–86. [15] Kepler CK, Yu AL, Gruskay JA, et al. Comparison of open and minimally invasive techniques for posterior lumbar instrumentation and fusion after open anterior lumbar interbody fusion. Spine J 2013;13:489–97. [16] McAnany SJ, Overley SC, Kim JS, et al. Open versus minimally invasive fixation techniques for thoracolumbar trauma: a meta-analysis. Global Spine J 2016;6:186–94. [17] German JW, Adamo MA, Hoppenot RG, et al. Perioperative results following lumbar discectomy: comparison of minimally invasive discectomy and standard microdiscectomy. Neurosurg Focus 2008;25:E20. [18] Holly LT, Schwender JD, Rouben DP, et al. Minimally invasive transforaminal lumbar interbody fusion: indications, technique, and complications. Neurosurg Focus 2006;20:E6. [19] Lau D, Lee JG, Han SJ, et al. Complications and perioperative factors associated with learning the technique of minimally invasive transforaminal lumbar interbody fusion (TLIF). J Clin Neurosci 2011;18:624–7. [20] Ntoukas V, Muller A. Minimally invasive approach versus traditional open approach for one level posterior lumbar interbody fusion. Minim Invasive Neurosurg 2010;53:21–4. [21] Park Y, Ha JW. Comparison of one-level posterior lumbar interbody fusion performed with a minimally invasive approach or a traditional open approach. Spine (Phila Pa 1976) 2007;32:537–43. [22] Peng CW, Yue WM, Poh SY, et al. Clinical and radiological outcomes of minimally invasive versus open transforaminal lumbar interbody fusion. Spine (Phila Pa 1976) 2009;34:1385–9. [23] Rahman M, Summers LE, Richter B, et al. Comparison of techniques for decompressive lumbar laminectomy: the minimally invasive versus the ‘‘classic” open approach. Minim Invasive Neurosurg 2008;51:100–5. [24] Schizas C, Tzinieris N, Tsiridis E, et al. Minimally invasive versus open transforaminal lumbar interbody fusion: evaluating initial experience. Int Orthop 2009;33:1683–8. [25] Wu RH, Fraser JF, Hartl R. Minimal access versus open transforaminal lumbar interbody fusion: meta-analysis of fusion rates. Spine (Phila Pa 1976) 2010;35:2273–81.
5
[26] Uribe JS, Deukmedjian AR, Mummaneni PV, et al. Complications in adult spinal deformity surgery: an analysis of minimally invasive, hybrid, and open surgical techniques. Neurosurg Focus 2014;36:E15. [27] Goldstein CL, Macwan K, Sundararajan K, et al. Perioperative outcomes and adverse events of minimally invasive versus open posterior lumbar fusion: meta-analysis and systematic review. J Neurosurg Spine 2016;24:416–27. [28] Agarwalla PK, Dunn IF, Scott RM, et al. Tethered cord syndrome. Neurosurg Clin N Am 2007;18:531–47. [29] Paradiso G, Lee GY, Sarjeant R, et al. Multi-modality neurophysiological monitoring during surgery for adult tethered cord syndrome. J Clin Neurosci 2005;12:934–6. [30] Yamada S, Iacono RP, Andrade T, et al. Pathophysiology of tethered cord syndrome. Neurosurg Clin N Am 1995;6:311–23. [31] Chou D, Eltgroth M, Yang I, et al. Rib head disarticulation for multilevel transpedicular thoracic corpectomies and expandable cage reconstruction. Neurol India 2009;57:469–74. [32] Chou D, Lau D, Roy E. Feasibility of the mini-open vertebral column resection for severe thoracic kyphosis. J Clin Neurosci 2014;21:841–5. [33] Chou D, Lu DC. Mini-open transpedicular corpectomies with expandable cage reconstruction. Technical note. J Neurosurg Spine 2011;14:71–7. [34] Chou D, Wang VY. Trap-door rib-head osteotomies for posterior placement of expandable cages after transpedicular corpectomy: an alternative to lateral extracavitary and costotransversectomy approaches. J Neurosurg Spine 2009;10:40–5. [35] Chou D, Wang VY, Gupta N. Transpedicular corpectomy with posterior expandable cage placement for L1 burst fracture. J Clin Neurosci 2009;16:1069–72. [36] Lau D, Chou D. Posterior thoracic corpectomy with cage reconstruction for metastatic spinal tumors: comparing the mini-open approach to the open approach. J Neurosurg Spine 2015;23:217–27. [37] Lu VM, Kerezoudis P, Gilder HE, et al. Minimally invasive surgery versus open surgery spinal fusion for spondylolisthesis: a systematic review and metaanalysis. (Spine Phila Pa 1976) 2016. [38] Singh K, Nandyala SV, Marquez-Lara A, et al. A perioperative cost analysis comparing single-level minimally invasive and open transforaminal lumbar interbody fusion. Spine J 2014;14:1694–701. [39] Goldstein CL, Phillips FM, Rampersaud YR. Comparative effectiveness and economic evaluations of open versus minimally invasive posterior or transforaminal lumbar interbody fusion: a systematic review. Spine (Phila Pa 1976) 2016;41(Suppl 8):S74–89. [40] Smith JS, Shaffrey CI, Sansur CA, et al. Rates of infection after spine surgery based on 108,419 procedures: a report from the Scoliosis Research Society Morbidity and Mortality Committee. Spine (Phila Pa 1976) 2011;36:556–63. [41] Djurasovic M, Rouben DP, Glassman SD, et al. Clinical outcomes of minimally invasive versus open TLIF: a propensity-matched cohort study. Am J Orthop (Belle Mead NJ). 2016;45:E77–82. [42] Uddin OM, Haque R, Sugrue PA, et al. Cost minimization in treatment of adult degenerative scoliosis. J Neurosurg Spine 2015;23:798–806. [43] Hamilton DK, Kanter AS, Bolinger BD, et al. Reoperation rates in minimally invasive, hybrid and open surgical treatment for adult spinal deformity with minimum 2-year follow-up. Eur Spine J 2016;25:2605–11.
Please cite this article in press as: Safaee MM et al. Mini-open spinal column shortening for the treatment of adult tethered cord syndrome. J Clin Neurosci (2017), http://dx.doi.org/10.1016/j.jocn.2017.07.037