Soon-Woo Hong

A comparison of unilateral and bilateral laminotomies for decompression of L4-L5 spinal stenosis.

Study Design. A retrospective review of clinical and radiographic data was performed at a single institution. Objectives. To compare clinical and radiologic outcomes between unilateral and bilateral laminotomies for bilateral decompression in patients with L4–L5 spinal stenosis. Summary of Background Data. Laminotomy has been shown to be comparable with laminectomy with the advantage of potentially maintaining more stability by preserving more of the osseous structures. However, the comparison between unilateral and bilateral laminotomies is available only for short-term follow-up. Methods. Fifty-three patients at one institution having decompres–sive surgery for L4–L5 spinal stenosis, including grade 1 degenerative spondylolisthesis without instability, were entered into this study with a minimum of 3-year follow-up. Clinical outcomes were assessed with visual analog scale for back and leg pain and the Oswestry disability index. Radiographic measurements were performed and included translational motion, angular motion, and epidural cross-sectional area. Results. The average age of the patients was 62.4 years (range: 31–82). The mean follow-up period was 49.3 months (range: 40–61). Clinical outcomes and complication rates were similar in both groups. Intraoperative blood loss and operative time were less in the unilateral laminotomy group. Radiographically, the amount of increased translational motion was significantly increased in the bilateral laminotomy group (P = 0.012), but the amount of increased angular motion was not significantly different (P = 0.195) between the two groups. Postoperative radiographic instability was detected more frequently in bilateral laminotomy group than in the unilateral group, without statistical significance. Conclusions. Both unilateral and bilateral laminotomies provide sufficient decompression of spinal stenosis and excellent pain reduction. However, unilateral laminotomy can be performed with shorter operative times and less blood loss. Radiologically, the use of a unilateral laminotomy induces less translational motion increase after surgery; thus, it may reduce the risk of late instability when compared with a bilateral laminotomy.

Comparison between the accuracy of percutaneous and open pedicle screw fixations in lumbosacral fusion

BACKGROUND CONTEXT In pedicle screw fixation, accurate insertion is essential to avoid neurological injury or weak stability. The percutaneous pedicle screw system was developed for minimally invasive spine surgery, and its safety has already been reported. However, the accuracy of percutaneous pedicle screw fixation (PPF) has not been compared with that of the open system to date. PURPOSE To compare the accuracy of PPF with that of open pedicle screw fixation (open PF) and to investigate the risk factors associated with pedicle wall penetration. STUDY DESIGN/SETTING A retrospective case series. PATIENT SAMPLE The study group included 237 patients who underwent posterior pedicle screw fixation between January 2008 and October 2010 at a single institute with a total of 1,056 pedicle screw fixations completed. One hundred and twenty-six patients with 558 screws underwent open PF and 111 patients with 498 screws underwent PPF. OUTCOME MEASURES Postoperative computerized tomography, including sagittal and coronal reformatted images. METHODS Consecutive surgeries with either conventional open PF or PPF for anterior lumbar interbody fusion or transforaminal lumbar interbody fusion were performed. The open pedicle screw employed was from the WSH system (Winova, Seoul, Korea), and the two percutaneous pedicle screw systems were the Sextant (Medtronics, Minneapolis, MN, USA) and the Viper systems (DePuy Spine, Raynham, MA, USA). Computed tomography images were evaluated to determine pedicle wall penetration after operation. Severity was classified as mild (<3 mm), moderate (3-6 mm), and severe (≥6 mm), and the direction was assessed as medial, lateral, inferior, and superior. RESULTS Pedicle wall penetration occurred in 75 patients (13.4%) in the open PF group and 71 patients (14.3%) in the PPF group and was not statistically different between the groups (p=.695). Assessment of the severity of the pedicle wall penetration revealed that minor penetration was the most common (open PF group, 9.7%; PPF group, 10.6%), although the distribution of the degree of severity was not statistically different between the groups (p=.863). A relatively higher incidence of lateral penetration was observed in the open PF group (66.7% vs. 43.7%), whereas medial, superior, and inferior penetrations were higher in the PPF group (p=.033). Other parameters such as age, sex, surgical method, and surgeon factors did not influence the penetration rate, but bone mineral densitometry negatively correlated with the penetration. CONCLUSIONS Pedicle wall penetration during screw fixation was not different between the open PF and PPF groups. The lateral, paraspinal, muscle-splitting approach seems to lessen medial wall penetration, especially in the S1 vertebra. Distribution of the direction of penetration differs between the groups, with lateral wall penetration being more prominent in the open PF group. Careful placement of pedicle screws is necessary for a stronger construct because of the high incidence of penetration.

Spinopelvic alignment after interspinous soft stabilization with a tension band system in grade 1 degenerative lumbar spondylolisthesis.

Study Design. Retrospective clinical study. Objective. The purpose of this study was to examine the changes in spinopelvic alignment after interspinous soft stabilization (ISS) with a tension band system and to identify the lumbosacral parameters related to those changes and to determine their impact on the clinical outcomes compared with posterior lumbar interbody fusion (PLIF) in patients with low-grade degenerative spondylolisthesis (DS). Summary of Background Data. The sacropelvic morphometric changes after fusion surgery have received much research attention. However, few reports have addressed the issue after use of dynamic or soft stabilization systems. Methods. From April 2001 to November 2003, 45 patients presenting with grade 1 DS with stenosis underwent either ISS with a tension band system (ISS group) or PLIF with pedicle screw fixation (PLIF group). The mean follow-up period was 76.8 months. Three pelvic parameters, the sacral slope (SS), pelvic tilt (PT), and pelvic incidence, were investigated to address the sacropelvic morphometric change. Clinical outcomes were assessed using the visual analog scale score, the Oswestry Disability Index, and the patients satisfaction index. Results. Both groups showed significant improvements in all of the clinical outcomes, with no significant differences between groups. In the ISS group, the SS increased and PT decreased, whereas in the PLIF group, the SS decreased and PT increased, resulting in pelvic anteversion and retroversion, respectively, with significant intergroup differences in SS and PT (SS: P = 0.047; PT: P = 0.01). The positive association of lumbar lordosis with SS (r = 0.448) and its negative association with PT (r = −0.674) in the respective groups indicate the influence of changes in lumbar lordosis on pelvic positional changes. Significant correlations between follow-up segmental lumbar lordosis and the visual analog scale score for leg pain (r = −0.685) and Oswestry Disability Index score (r = −0.425) were found in the ISS group alone. Conclusion. Segmental lordotic change after ISS with a tension band system was the possible decisive factor in the development of pelvic anteversion while maintaining sagittal lumbar balance; lack of lumbar lordosis led to compensatory pelvic retroversion in the PLIF group. Considering the comparable clinical results with PLIF surgery and the achievement of physiologic sagittal spinopelvic balance, the ISS procedure can be a feasible alternative to fusion surgery in patients with grade 1 DS with stenosis.

Factors affecting clinical outcomes in treating patients with grade 1 degenerative spondylolisthesis using interspinous soft stabilization with a tension band system: a minimum 5-year follow-up.

Study Design. Retrospective clinical study. Objective. To explore the factors influencing the clinical outcomes and motion-preserving stabilization after interspinous soft stabilization (ISS) with a tension band system for grade 1 degenerative spondylolisthesis (DS). Summary of Background Data. Despite increasing recognition of the benefits of dynamic stabilization systems for treating lumbar degenerative disorders, the factors affecting the clinical and radiological outcomes of these systems have rarely been identified. Methods. Sixty-five patients (mean age, 60.3 years) who underwent ISS with a tension band system between 2002 and 2004 were analyzed. The mean follow-up period was 72.5 months. The patients were divided according to the postsurgical clinical improvements into the optimal (n = 44) and suboptimal groups (n = 21), and the radiological intergroup differences were analyzed. Multiple linear regression analysis was performed to determine the impact of the radiological factors on the clinical outcomes. Results. Significant intergroup differences were observed on the follow-up clinical examination. Radiologically, total lumbar lordosis (TLL) and segmental lumbar lordosis (SLL) were significantly improved only in the optimal group, resulting in significant intergroup differences in TLL (P = 0.023), SLL (P = 0.001), and the L1 tilt (P = 0.002). All these measures were closely associated with postoperative segmental lumbar lordosis, which also was the most influential radiological variable for the clinical parameters. Conclusion. In the patients with grade 1 DS, the back pain relief and functional improvement following ISS were affected by the improvements in the sagittal spinal alignment through the achievement of segmental lumbar lordosis. ISS can be an alternative treatment to fusion surgery for grade 1 DS in patients who do not require fixation or reduction.

Anterior Dislodgement of a Fusion Cage after Transforaminal Lumbar Interbody Fusion for the Treatment of Isthmic Spondylolisthesis

Transforaminal lumbar interbody fusion (TLIF) is commonly used procedure for spinal fusion. However, there are no reports describing anterior cage dislodgement after surgery. This report is a rare case of anterior dislodgement of fusion cage after TLIF for the treatment of isthmic spondylolisthesis with lumbosacral transitional vertebra (LSTV). A 51-year-old man underwent TLIF at L4-5 with posterior instrumentation for the treatment of grade 1 isthmic spondylolisthesis with LSTV. At 7 weeks postoperatively, imaging studies demonstrated that banana-shaped cage migrated anteriorly and anterolisthesis recurred at the index level with pseudoarthrosis. The cage was removed and exchanged by new cage through anterior approach, and screws were replaced with larger size ones and cement augmentation was added. At postoperative 2 days of revision surgery, computed tomography (CT) showed fracture on lateral pedicle and body wall of L5 vertebra. He underwent surgery again for paraspinal decompression at L4-5 and extension of instrumentation to S1 vertebra. His back and leg pains improved significantly after final revision surgery and symptom relief was maintained during follow-up period. At 6 months follow-up, CT images showed solid fusion at L4-5 level. Careful cage selection for TLIF must be done for treatment of spondylolisthesis accompanied with deformed LSTV, especially when reduction will be attempted. Banana-shaped cage should be positioned anteriorly, but anterior dislodgement of cage and reduction failure may occur in case of a highly unstable spine. Revision surgery for the treatment of an anteriorly dislodged cage may be effectively performed using an anterior approach.

Dynamic MRI of the Spine

Spinal imaging is one of the most important diagnostic tools for assessing spine pathologies. The advent of Magnetic Resonance Imaging (MRI) allowed much more detailed evaluation of musculoskeletal injuries including the spine. However, because of the structural limitations of MRI equipment, patient scanning has been limited to supine or prone positions without weight-bearing, which renders static images in fixed positions. Specifically, dynamic evaluation of the spine with functional loading has not been possible.

Interspinous ligamentoplasty. Authors' reply

Lumbar spinal stenosis is a common cause of lowback pain and neurogenic claudication in the adult population. Moreover, degenerative spondylolisthesis ac c ounts for a substantial proportion of lumbar spinal stenosis in this age group. Spinal fusion has become the established operative treatment for unstable degenerative spondylolisthesis.2 However, there are several disadvantages and issues related to posterior instrumented fusion including adjacent-segment degeneration, pseudarthrosis, and other potential complications.7,8 In light of these issues, surgeons have developed an increasing interest in examining alternative approaches to lumbar fusion, which is the basis of the article on interspinous ligamentoplasty by Hong et al.3 in this issue of the Journal of Neurosurgery: Spine. Adjacent-segment disease after lumbar fusion has been well documented in the literature and the awareness of this complication among our community is high. Its incidence ranges in some studies from 25 to 40% with the radiographic incidence approaching 100% and the symptomatic incidence nearly 25%.5 Of particular relevance to the article by Hong et al., Ghiselli et al.1 reported only 3% symptomatic caudal adjacent-segment disease for singlelevel fusion at L4–5 after a mean follow-up of 7.3 years. Hong et al. had an adjacent-segment disease incidence of 4% (1 case out of 23), which is comparable to the rate following single-level fusion at the same level. The above-mentioned issues have provided the impetus for spine surgeons to examine new devices, including dynamic implants. A number of semirigid implant designs have been developed to improve segmental stability, unload posterior elements, and restrict painful motion while otherwise enabling movement. The aim is to attempt to reestablish the “neutral zone” of spinal motion where the range of displacement occurs with force-free motion, as elucidated by White and Panjabi.9 So far, the most studied interspinous device, the X-STOP has only provided us with shortand medium-term results.10–12 The concept of interspinous ligamentoplasty (ILP) was first introduced by Senegas.6 A modified technique was first reported by authors from the same institution as Hong and colleagues (Wooridul Spine Hospital) in 2005.4 Conceptually, ILP restricts flexion of the lumbar spine with augmentation of the interspinous and supraspinatus ligaments. Intuitively, this should limit translation in cases of degenerative spondylolisthesis. The article by Hong et al.3 in this issue is essentially a case series, in which the authors performed their modified ILP in 32 patients (following up 23 patients or 72%) who had Grade 1 spondylolisthesis at L4–5 and were symptomatic for spinal stenosis and in whom conservative management for at least 6 months had failed. Only patients who exhibited sagittal listhesis with central canal stenosis and lateral recess stenosis were included in the study. All other forms of spinal stenosis that were associated with scoliosis, lateral translation, severe disc collapse, or foraminal stenosis were excluded. A control group of 18 patients who underwent bilateral laminotomies was also included, although this group was not prospectively defined and the extent of matching is not clear. The follow-up assessments were made with outcome scores based on the Oswestry Disability Index (ODI) and visual analog scale (VAS) scores, as well as radiological measurements. The mean duration of follow-up was just over 5 years, which qualifies as medium-term results. The clinical outcome showed improvement in the ODI as well as the VAS. Radiological analysis showed consistent improvement in lordosis but there was increased slippage as well as disc collapse, although the latter 2 radiological outcomes did not appear to affect the clinical outcome. What appears to be most significant is that the canal area was increased postoperatively at the referenced level of L4–5. This is obviously a result of the decompression that was performed. It is therefore not proven that ILP is superior to a formal decompression laminectomy, and it is not known if the positive clinical outcome was contributed by a combination of ILP and the decompression, or if decompression alone would have been adequate. It is thus wise not to over-interpret the clinical outcomes of this paper. With regard to complications related to ILP, the auJ Neurosurg Spine 13:24–26, 2010 See the corresponding article in this issue, pp 27–35.