The Spine Journal 14 (2014) 1081–1092

Letters to the Editor Minimally invasive versus open laminotomy

To the Editor: We read with great interest the recent article by Ang et al. [1], titled ‘‘Minimally invasive compared with open lumbar laminotomy: no functional benefits at 6 or 24 months after surgery.’’ The authors compared the functional and pain outcomes of 30 patients with open laminotomies against 83 patients with minimally invasive surgery (MIS) laminotomies at 6 and 24 months. They concluded that ‘‘MIS lumbar laminotomy gave no clear advantages in long-term functional or pain scores. The MIS group also had patients with inadvertent durotomies and reoperation within 2 years. In any lumbar decompressive surgery, the purported advantages of an MIS approach should be carefully weighed against potential complications.’’ We applaud the authors’ effort in conducting this study in pursuit of optimizing patient care and agree with them in concluding that the purported advantages of an MIS approach should be carefully weighed against potential complications, which in fact should be true for any clinical procedure. However, we would like to point out several relevant issues related to this article. First, the authors encountered three unintended durotomies of 83 MIS laminotomies (2.7%), whereas none of the 30 open laminotomy patients had durotomies (no statistical significant difference). They cited this as a potential complication unique to MIS procedures, when in fact unintended durotomies are well-known complications to spine surgery, regardless of whether an open or MIS approach is used [2,3]. In fact, when an unintended durotomy does occur, it is much less likely to be symptomatic in the MIS group because there is much less dead space available for pseudomeningocele formation and the paraspinal muscles re-expansion after tubular dilator removal further minimizes the risk of wound-related complications. Therefore, unintended durotomies should not be considered a complication unique to MIS surgery, and although we agree that there might be higher incidence of durotomies during the initial part of the learning curve with MIS (note that 2 of the 3 durotomies occurred with relatively inexperienced surgeons); there should be no difference as the surgeons become experienced. Secondly, the authors presented that there were two patients in the MIS group who required fusion within the 2year study period. Again, this is not statistically significant, meaning that the two fusion cases in the MIS group could have occurred purely by chance. Also, the reason to perform fusion on the two patients was progression of disc prolapse

at the operated segments causing recurrent ipsilateral stenosis [1]. Though the authors elected to perform decompressive laminectomy and fusion on those, a redo-MIS procedure with discectomy could have been an option if there was no instability. Also the failure seen in these two patients resulted from progression of the disc prolapse and probably have no relation with MIS. As the authors mentioned that one of those patients had Grade I spondylolisthesis, if instability was not ruled out on dynamic X-rays before surgery, the chances of that patient requiring fusion down the line would be high to begin with, regardless of the choice of approach. If anything, an MIS laminotomy would be better in these circumstances, as it preserves the integrity of the soft tissue and ligaments better. There is emerging data showing the effectiveness of minimally invasive decompression in patients with Grade I spondylolisthesis [4,5]. The risk of progression in spondylolithesis always remains in this group, but not all slip progressions are clinically symptomatic and may not warrant fusion on follow-up. Careful patient selection with avoidance of mobile spondylolisthesis remains critical [4,5]. Thirdly, posterior tension band is important in spine biomechanics and disruption of the paraspinal muscle can increase the risk of delayed instability which may not be apparent at only 2 years, especially when dealing with laminotomy, which is a relatively small open procedure to begin with. In fact, the true benefits of MIS techniques are unlikely to be realized in this procedure that already has low complication rates and morbidity with rapid recovery rates. The advantage of MIS may be more apparent with multilevel decompressive procedures as MIS techniques become more familiar to surgeons. Fourth, the authors had mentioned that the MIS group had much shorter hospital stay compared with the open surgery group (1.1 days vs. 2.0 days, p!.001), which means much less health care burden. This along with early return to work by these patients can easily offset the one-time cost of purchasing MIS equipment. In fact, patients at our center routinely go home the same day after MIS laminotomy for lumbar stenosis. Various studies have clearly shown the clear benefits of MIS techniques over open surgery such as decreases in blood loss, infection rates, hospitalization times and narcotic use, and minimization of physiological stress on the patient, which are clear advantages that cannot be ignored [4–10]. This is also evident in the author’s study, where MIS was associated with greater satisfaction at 6 months. As open spine surgery has been the standard of care for decades demonstrating excellent outcome, it should not be surprising that both groups did better and were equally satisfied at 24 months. Nevertheless, the


Letters to the Editor / The Spine Journal 14 (2014) 1081–1092

immediate advantages of MIS translating into better satisfaction in the early postoperative period cannot be ignored. Fifth, an additional advantage of MIS is in obese patients in whom the exposure with tubular dilators is much easier than open approach, given the depth of the soft tissue in these patients. Risk of complications after MIS for lumbar spine fusion is not influenced by obesity because of the potential for shorter operative time and reduction of wound complications in these patients [9]. Finally, the percentage numbers in Table 2 for ‘‘Race’’ and ‘‘Side of laminotomy’’ appears to be incorrect. There has been an unprecedented advancement in MIS techniques and technologies over the past 15 years. Any minimally access surgery must be proven to treat symptoms to the same degree as compared with open procedures, while in the meantime, decreasing muscular and soft-tissue trauma, reducing physiological stress to the patient, enabling maintenance of the normal biomechanics of the spine, and improving on the perioperative end points are achieved with traditional surgeries [11]. In addition, it must be safe with fewer complications, less infections, and less requirement for subsequent surgeries than after open surgery. There are a number of studies demonstrating all these points in the literature specifically for lumbar stenosis [6,8,11]. We strongly believe that MIS is an excellent approach that does not have any additional complication compared with open approach but with added benefits of shorter hospital stay, quicker recovery, faster return to work, and less infection and wound complications and all spine surgeons should strive to bring that in their armamentarium for management of lumbar stenosis. References [1] Ang CL, Phak-Boon Tow B, Fook S, et al. Minimally invasive compared with open lumbar laminotomy: no functional benefits at 6 or 24 months after surgery. Spine J 2013;. spinee.2013.07.461. [2] Ruban D, O’Toole JE. Management of incidental durotomy in minimally invasive spine surgery. Neurosurg Focus 2011;31:E15. [3] Williams BJ, Sansur CA, Smith JS, et al. Incidence of unintended durotomy in spine surgery based on 108,478 cases. Neurosurgery 2011;68:117–23. [4] Ikuta K, Tono O, Oga M. Clinical outcome of microendoscopic posterior decompression for spinal stenosis associated with degenerative spondylolisthesisdminimum 2-year outcome of 37 patients. Minim Invasive Neurosurg 2008;51:267–71. [5] Jang JW, Park JH, Hyun SJ, et al. Clinical outcomes and radiologic changes following microsurgical bilateral decompression via a unilateral approach in patients with lumbar canal stenosis and grade I degenerative spondylolisthesis with a minimum 3-year follow-up. J Spinal Disord Tech 2012;. [6] Oertel MF, Ryang YM, Korinth MC, et al. Long-term results of microsurgical treatment of lumbar spinal stenosis by unilateral laminotomy for bilateral decompression. Neurosurgery 2006;59:1264–9. [7] Djurasovic M, Bratcher KR, Glassman SD, et al. The effect of obesity on clinical outcomes after lumbar fusion. Spine 2008;33: 1789–92. [8] O’Toole JE. The future of minimally invasive spine surgery. Neurosurgery 2013;60(1 Suppl):13–9. [9] Rosen DS, Ferguson SD, Ogden AT, et al. Obesity and self-reported outcome after minimally invasive lumbar spinal fusion surgery. Neurosurgery 2008;63:956–60.

[10] Rosen DS, O’Toole JE, Eichholz KM, et al. Minimally invasive lumbar spinal decompression in the elderly: outcomes of 50 patients aged 75 years and older. Neurosurgery 2007;60:503–9. [11] Smith ZA, Fessler RG. Paradigm changes in spine surgery: evolution of minimally invasive techniques. Nat Rev Neurol 2012;8:443–50.

Lee A. Tan, MD Manish K. Kasliwal, MD, MCh Richard G. Fessler, MD, PhD Department of Neurosurgery RUSH University Medical Center 1725 W Harrison Street, Suite 855 Chicago, IL, 60612, USA FDA device/drug status: Not applicable. Author disclosures: LAT: Nothing to disclose. MKK: Nothing to disclose. RGF: Nothing to disclose. Source of support: None. Source of funding: None. 1529-9430/$ - see front matter Ó 2014 Elsevier Inc. All rights reserved

Comments about Zou Z, Song Y, Cai Q, Kong Q. Spontaneous resolution of scoliosis associated with lumbar spondylolisthesis. Spine J 2013;13:e7–e10 To the Editor: We thank Zou and colleagues for extensively referring to our article, ‘‘AIS and spondylolisthesis,’’ [1] in their case report, and would like to make comments about their observations.  In our work we described structured scoliosis, which features fixed deformity rotation with rib hump in anterior bending and all the other peculiarities of the socalled idiopathic scoliosis. We also cited functional scoliosis, which other authors have reported on [2–4]. The case study does not show any rotation, as the authors have extensively described. This type of scoliosis is completely solved in the supine position and so it does not involve the structured or fixed aspects associated with idiopathic scoliosis. It should be considered as functional scoliosis, and not as a structured and fixed scoliosis with idiopathic curve features, as we [1] have already reported in agreement with the above works [2–4]. It seems arbitrary that the authors stated ([5], page 10 fourth line) that we [1] claim to have treated scoliosis and spondylolisthesis at the same time. In this patient, we treated spondylolisthesis only and we detected and observed scoliosis evolution on time.  We would like, moreover, to point out in relation to the case description ([5], page 8 first paragraph, 21st line) that the authors reported no pain, and described only a modest restriction in forward bending. No neurologic

Minimally invasive versus open laminotomy.

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