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1.  Paraspinal Muscle Sparing versus Percutaneous Screw Fixation : A Prospective and Comparative Study for the Treatment of L5-S1 Spondylolisthesis 
Objective
Both the paraspinal muscle sparing approach and percutaneous screw fixation are less traumatic procedures in comparison with the conventional midline approach. These techniques have been used with the goal of reducing muscle injury. The purpose of this study was to evaluate and to compare the safety and efficacy of the paraspinal muscle sparing technique and percutaneous screw fixation for the treatment of L5-S1 spondylolisthesis.
Methods
Twenty patients who had undergone posterior lumbar interbody fusion (PLIF) at the L5-S1 segment for spondylolisthesis were prospectively studied. They were divided into two groups by screw fixation technique (Group I : paraspinal muscle sparing approach and Group II: percutaneous screw fixation). Clinical outcomes were assessed by Low Back Outcome Score (LBOS) and Visual Analogue Scale (VAS) for back and leg pain at different times after surgery. In addition, modified MacNab's grading criteria were used to assess subjective patients' outcomes 6 months after surgery. Postoperative midline surgical scarring, intraoperative blood loss, mean operation time, and procedure-related complications were analyzed.
Results
Excellent or good results were observed in all patients in both groups 6 months after surgery. Patients in both groups showed marked improvement in terms of LBOSs all over time intervals. Postoperative midline surgical scarring and intraoperative blood loss were lower in Group II compared to Group I although these differences were not statistically significant. Low back pain (LBP) and leg pain in both groups also showed significant improvement when compared to preoperative scores. However, at 7 days and 1 month after surgery, patients in Group II had significantly better LBP scores compared to Group I.
Conclusion
In terms of LBP during the early postoperative period, patients who underwent percutaneous screw fixation showed better results compared to ones who underwent screw fixation via the paraspinal muscle sparing approach. Our results indicate that the percutaneous screw fixation procedure is the preferable minimally invasive technique for reducing LBP associated with L5-S1 spondylolisthesis.
doi:10.3340/jkns.2011.49.3.163
PMCID: PMC3085812  PMID: 21556236
Spondylolisthesis; Paraspinal muscle sparing approach; Percutaneous screw fixation; Back pain
2.  Spinous process-splitting open pedicle screw fusion provides favorable results in patients with low back discomfort and pain compared to conventional open pedicle screw fixation over 1 year after surgery 
European Spine Journal  2012;21(4):745-753.
Introduction
The conventional open pedicle screw fusion (PSF) requires an extensive detachment of the paraspinal muscle from the posterior aspect of the lumbar spine, which can cause muscle injury and subsequently lead to “approach-related morbidity”. The spinous process-splitting (SPS) approach for decompression, unilateral laminotomy for bilateral decompression, and the Wiltse approach for pedicle screw insertion are considered to be less invasive to the paraspinal musculature. We investigated whether SPS open PSF combined with the abovementioned techniques attenuates the paraspinal muscle damage and yields favorable clinical results, including alleviation in the low back discomfort, in comparison to the conventional open PSF.
Methods
We studied 53 patients who underwent single-level PSF for the treatment of degenerative spondylolisthesis (27 patients underwent SPS open PSF and the other 26 underwent the conventional open PSF). The clinical outcomes were assessed using the Japanese Orthopedic Association (JOA) score, the Roland–Morris disability questionnaire (RDQ), and the visual analog scale (VAS) for low back pain and low back discomfort (heavy feeling or stiffness). Postoperative multifidus (MF) atrophy was evaluated using MRI. Follow-up examinations were performed at 1 and 3 years after the surgery.
Results
Although there was no significant difference in the JOA and RDQ score between the two groups, the VAS score for low back pain and discomfort after the surgery were significantly lower in the SPS open PSF group than in the conventional open PSF group. The extent of MF atrophy after SPS open PSF was reduced more significantly than after the conventional open PSF during the follow-up. The MF atrophy ratio was found to correlate with low back discomfort at the 1-year follow-up examination.
Conclusion
In conclusion, SPS open PSF was less damaging to the paraspinal muscle than the conventional open PSF and had a significant clinical effect, reducing low back discomfort over 1 year after the surgery.
doi:10.1007/s00586-011-2146-2
PMCID: PMC3326135  PMID: 22237851
Posterior lumbar fusion; Multifidus muscle; Wiltse approach; Minimally invasive; Conventionally open
3.  Minimally Invasive Mini Open Split-Muscular Percutaneous Pedicle Screw Fixation of the Thoracolumbar Spine 
Orthopedic Reviews  2015;7(1):5661.
We prospectively assessed the feasibility and safety of a new percutaneous pedicle screw (PPS) fixation technique for instrumentation of the thoracic and lumbar spine in this study. All patients were operated in the prone position under general anesthesia. A 6 to 8 cm midline skin incision was made and wide subcutaneous dissection was performed. The paravertebral muscles were first dissected subperiosteally into the midline incision of the fascia for lumbar microdiscectomy with transforaminal lumbar interbody fusion cage implantation. After the secondary paramedian incisions on the fascia, the PPSs were inserted via cleavage of the multifidus muscles directly into the pedicles under fluoroscopy visualization. A total of 35 patients underwent surgery with this new surgical technique. The control group for operative time, blood loss and analgesic usage consisted of 35 randomly selected cases from our department. The control group underwent surgery via conventional pedicle screw instrumentation with paramedian fusion. All patients in the minimal invasive surgery series were ambulatory with minimal pain on the first postoperative day. The operation time and blood loss and the postoperative analgesic consumption were significantly less with this new technique. In conclusion, the minimal invasive mini open split-muscular percutaneous pedicle screw fixation technique is safe and feasible. It can be performed via a short midline skin incision and can also be combined with interbody fusion, causing minimal pain without severe muscle damage.
doi:10.4081/or.2015.5661
PMCID: PMC4387363  PMID: 25874062
minimally invasive; thoracolumbar; percutaneous; pedicle screw; spinal surgery
4.  Pedicle screw fixation and posterior fusion for lumbar degenerative diseases: effects on individual paraspinal muscles and lower back pain; a single-center, prospective study 
Background
To the best of our knowledge, there have been no reports on the points at which the denervated multifidus and erector spinae muscles become reinnervated after pedicle screw fixation and posterior fusion in patients with lumbar degenerative diseases. Our study was designed to confirm reinnervation of denervated paraspinal muscles following pedicle screw fixation and posterior fusion and to confirm alleviation of the patients’ lower back pain (LBP).
Methods
In this prospective study, we enrolled 67 patients who had undergone pedicle screw fixation and posterior fusion. The surgery had alleviated their leg pain, but the patients complained of LBP at the L3-5 level 3 months after the surgery. The patients were divided into two groups (I and II) according to the level at which pain was experienced. Paraspinal mapping scores were recorded preoperatively and 3, 6, 12, and 18 months postoperatively. Oswestry Disability Index and visual analogue scale scores were determined. Regression analyses using a general linear model and a mixed model were performed.
Results
Pedicle screw fixation and posterior fusion significantly denervated the multifidus and erector spinae not only in the surgical segment, but also in adjacent segments. Group I patients displayed reinnervation in the denervated erector spinae and multifidus muscles at 12 and 18 months, respectively. In contrast, group II showed reinnervation only in of the denervated erector spinae of the upper segment at 18 months, with no other areas of reinnervation. Postoperative LBP was significantly diminished at 12 months in group I and at 18 months in group II. There was also significantly less LBP at 6 months (prior to reinnervation of the paraspinal muscles).
Conclusions
The denervated multifidus and erector spinae muscles at L4–5, which had been denervated using pedicle screw fixation and posterior fusion, were significantly reinnervated at 18 months postoperatively, whereas patients with denervation at L3–5 had only a tendency to be reinnervated at follow-up. Postoperative LBP in these patients was significantly diminished at the follow-up visits.
doi:10.1186/s12891-016-0927-9
PMCID: PMC4744382  PMID: 26850001
Pedicle screw fixation; Posterior fusion; Paraspinal muscle; Reinnervation; Lower back pain
5.  The Quantitative Analysis of Back Muscle Degeneration after Posterior Lumbar Fusion: Comparison of Minimally Invasive and Conventional Open Surgery 
Asian Spine Journal  2009;3(2):89-95.
Study Design
Prospective controlled study.
Purpose
The results of conventional open surgery was compared with those from minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) for lumbar fusion to determine which approach resulted in less postoperative paraspinal muscle degeneration.
Overview of Literature
MI TLIF is new surgical technique that appears to minimize iatrogenic injury. However, there aren't any reports yet that have quantitatively analyzed and proved whether there's difference in back muscle injury and degeneration between the minimally invasive surgery and conventional open surgery in more than 1 year follow-up after surgery.
Methods
This study examined a consecutive series of 48 patients who underwent lumbar fusion in our hospital during the period, March 2006 to March 2008, with a 1-year follow-up evaluation using MRI. There were 17 cases of conventional open surgery and 31 cases of MI-TLIF (31 cases of single segment fusion and 17 cases of multi-segment fusion). The digital images of the paravertebral back muscles were analyzed and compared using the T2-weighted axial images. The point of interest was the paraspinal muscle of the intervertebral disc level from L1 to L5. Picture archiving and communication system viewing software was used for quantitative analysis of the change in fat infiltration percentage and the change in cross-sectional area of the paraspinal muscle, before and after surgery.
Results
A comparison of the traditional posterior fusion method with MI-TLIF revealed single segment fusion to result in an average increase in fat infiltration in the paraspinal muscle of 4.30% and 1.37% and a decrease in cross-sectional area of 0.10 and 0.07 before and after surgery, respectively. Multi-segment fusion showed an average 7.90% and 2.79% increase in fat infiltration and a 0.16 and 0.10 decrease in cross-sectional area, respectively. Both single and multi segment fusion showed less change in the fat infiltration percentage and cross-sectional area, particularly in multi segment fusion. There was no significant difference between the two groups in terms of the radiologic results.
Conclusions
A comparison of conventional open surgery with MI-TLIF upon degeneration of the paraspinal muscle with a 1 year follow-up evaluation revealed that both single and multi segment fusion showed less change in fat infiltration percentage and cross-sectional area in the MI-TLIF but there was no significant difference between the two groups. This suggests that as time passes after surgery, there is no significant difference in the level of degeneration of the paraspinal muscle between surgical techniques.
doi:10.4184/asj.2009.3.2.89
PMCID: PMC2852079  PMID: 20404953
Paraspainal muscle; Fat degeneration; MRI; Posterior fusion
6.  Paraspinal Muscle Sparing Versus Percutaneous Screw Fixation: A Comparative Enzyme Study of Tissue Injury during the Treatment of L4-L5 Spondylolisthesis 
Korean Journal of Spine  2012;9(4):321-325.
Objective
Screw fixation via the paraspinal muscle sparing approach and by percutaneous screw fixation are known to diminish the risk of complications, such as, iatrogenic muscle injury as compared with the conventional midline approach. The purpose of this study was to evaluate tissue injury markers after these less traumatic screw fixation techniques for the treatment of L4-L5 spondylolisthesis.
Methods
Twenty-two patients scheduled for posterior lumbar interbody fusion (PLIF) at the L4-L5 segment for spondylolisthesis were prospectively studied. Patients were divided into two groups by screw fixation technique (Group I: paraspinal muscle sparing approach and Group II: percutaneous screw fixation). Levels of serum enzymes representing muscle injury (CK-MM and Troponin C type 2 fast), pro-inflammatory cytokine (IL-8), and anti-inflammatory cytokine (IL-1ra) were analyzed using ELISA techniques on the day of the surgery and 1, 3, and 7 days after the surgery.
Results
Serum CK-MM, Troponic C type 2 fast (TNNC2), and IL-1ra levels were significantly elevated in Group I on postoperative day 1 and 3, and returned to preoperative levels on postoperative day 7. No significant intergroup difference was found between IL-8 levels despite higher concentrations in Group I on postoperative day 1 and 3.
Conclusion
This study shows that percutaneous screw fixation procedure is the preferable minimally invasive technique in terms of minimizing muscle injury associated with L4-L5 spondylolisthesis.
doi:10.14245/kjs.2012.9.4.321
PMCID: PMC4430557  PMID: 25983840
Paraspinal muscle sparing approach; Percutaneous screw fixation; Tissue injury
7.  The Effects of Spinopelvic Parameters and Paraspinal Muscle Degeneration on S1 Screw Loosening 
Objective
To investigate risk factors for S1 screw loosening after lumbosacral fusion, including spinopelvic parameters and paraspinal muscles.
Methods
We studied with 156 patients with degenerative lumbar disease who underwent lumbosacral interbody fusion and pedicle screw fixation including the level of L5-S1 between 2005 and 2012. The patients were divided into loosening and non-loosening groups. Screw loosening was defined as a halo sign larger than 1 mm around a screw. We checked cross sectional area of paraspinal muscles, mean signal intensity of the muscles on T2 weight MRI as a degree of fatty degeneration, spinopelvic parameters, bone mineral density, number of fusion level, and the characteristic of S1 screw.
Results
Twenty seven patients showed S1 screw loosening, which is 24.4% of total. The mean duration for S1 screw loosening was 7.3±4.1 months after surgery. Statistically significant risk factors were increased age, poor BMD, 3 or more fusion levels (p<0.05). Among spinopelvic parameters, a high pelvic incidence (p<0.01), a greater difference between pelvic incidence and lumbar lordotic angle preoperatively (p<0.01) and postoperatively (p<0.05). Smaller cross-sectional area and high T2 signal intensity in both multifidus and erector spinae muscles were also significant muscular risk factors (p<0.05). Small converging angle (p<0.001) and short intraosseous length (p<0.05) of S1 screw were significant screw related risk factors (p<0.05).
Conclusion
In addition to well known risk factors, spinopelvic parameters and the degeneration of paraspinal muscles also showed significant effects on the S1 screw loosening.
doi:10.3340/jkns.2015.58.4.357
PMCID: PMC4651997  PMID: 26587190
Lumbosacral region; Pedicle screws; Instrumentation; Muscle; Spinal fusion; Risk factors
8.  Benefits of the Paraspinal Muscle-Sparing Approach Versus the Conventional Midline Approach for Posterior Nonfusion Stabilization: Comparative Analysis of Clinical and Functional Outcomes 
SAS Journal  2007;1(3):93-99.
Background
The influence of approach on outcomes of posterior nonfusion stabilization has not been described. This paper analyzes the influence of surgical approach on functional outcome with nonfusion stabilization.
Methods
We performed a prospective consecutive cohort outcome analysis of 88 patients who had undergone posterior nonfusion stabilization of the lumbar spine at 178 levels using the Dynesys system (Zimmer Spine, Inc, Warsaw, Indiana). Patients needing decompression (n = 42) were operated through a midline approach using microscopic laminotomy/foraminotomy with or without discectomy, followed by posterior nonfusion stabilization with Dynesys. None of the patients had a complete laminectomy. Patients not needing decompression (n = 46) underwent the procedure via the bilateral paraspinal muscle-sparing approach and were subsequently stabilized. Clinical and functional outcomes data were collected using the visual analog scale (VAS), Treatment Intensity Score (TIS), Oswestry Disability Index (ODI), and SF-36. Average follow-up was 18 months (range, 12–36 mo).
Results
All outcome measures in both groups showed significant improvement at last follow-up. Between the groups a significant difference was apparent in the reduction of the TIS when measured at 1 week and 6 weeks. The preoperative, 1-week, and 6-week values were 66, 48, and 40, respectively (P < 0.05), for the midline group and 80, 32, and 28 (P < 0.05) for the paraspinal group. This trend continued through 3 to 6 months after the procedure but did not reach statistical significance. In the paraspinal group, pain scores showed a nonsignificant trend toward lower values in the first month, compared with values in the midline group. Patients reported excellent to fair results, with the exception of three patients in the midline group and two in the paraspinal group, who rated the procedure as fair.
Conclusions
Significantly fewer patients required postoperative narcotics in the paraspinal group than in the midline group. This improvement in early outcomes suggests a significant early benefit to the less tissue-destructive muscle-sparing approach in posterior nonfusion stabilization procedures.
doi:10.1016/SASJ-2007-0101-RR
PMCID: PMC4365577  PMID: 25802585
Posterior nonfusion spinal stabilization; muscle-sparing approach; paraspinal approach
9.  CT and MRI Determination of Intermuscular Space within Lumbar Paraspinal Muscles at Different Intervertebral Disc Levels 
PLoS ONE  2015;10(10):e0140315.
Background
Recognition of the intermuscular spaces within lumbar paraspinal muscles is critically important for using the paramedian muscle-splitting approach to the lumbar spine. As such, it is important to determine the intermuscular spaces within the lumbar paraspinal muscles by utilizing modern medical imaging such as computed tomography (CT) and magnetic resonance imaging (MRI).
Methods
A total of 30 adult cadavers were studied by sectional anatomic dissection, and 60 patients were examined using CT (16 slices, 3-mm thickness, 3-mm intersection gap, n = 30) and MRI (3.0T, T2-WI, 5-mm thickness, 1-mm intersection gap, n = 30). The distances between the midline and the superficial points of the intermuscular spaces at different intervertebral disc levels were measured.
Results
Based on study of our cadavers, the mean distances from the midline to the intermuscular space between multifidus and longissimus, from intervertebral disc levels L1–L2 to L5–S1, were 0.9, 1.1, 1.7, 3.0, and 3.5 cm, respectively. Compared with the upper levels (L1–L3), the superficial location at the lower level (L4–S1) is more laterally to the midline (P<0.05). The intermuscular space between sacrospinalis and quadratus lumborum, and that between longissimus and iliocostalis did not exist at L4–S1. The intermuscular spaces in patients also varied at different levels of the lumbar spine showing a low discontinuous density in CT and a high signal in MRI. There were no significant differences between the observations in cadavers and those made using CT and MRI.
Conclusion
The intermuscular spaces within the paraspinal muscles vary at different intervertebral disc levels. Preoperative CT and MRI can facilitate selection of the muscle-splitting approach to the lumbar spine. This paper demonstrates the efficacy of medical imaging techniques in surgical planning.
doi:10.1371/journal.pone.0140315
PMCID: PMC4601766  PMID: 26458269
10.  TLIF for symptomatic disc degeneration: a retrospective study of 100 patients 
European Spine Journal  2011;20(Suppl 1):57-60.
The goal of a fusion of the lumbar spine is to obtain a primary solid arthrodesis thus to alleviate pain. Different circumferential fusion techniques have been described such as combined anterior–posterior fusion (APF), instrumented posterior lumbar interbody fusion (PLIF) and transforaminal lumbar interbody fusion (TLIF). The TLIF procedure has rapidly gained popularity; because of its posterolateral extracanalar discectomy and fusion, it has been reported as a safe technique, without the potential complications described when using combined APF and PLIF techniques. A retrospective clinical and radiographic study was performed. The database of our Center was interrogated in a retrospective way to extract data from patients that underwent a one or two level lumbar fusion with TLIF approach. All patients had symptomatic disc degeneration of the lumbar spine. One hundred and fourteen levels fused from 2003 to 2008. All patients were operated in the same center. All the patients were operated by the same surgical team. Patients were evaluated preoperatively and postoperatively at 1 and 3 months and 1 and 2 years follow-up. The spine was approached through a classic posterior midline incision and subperiosteal muscular detachment. The side of facetectomy was chosen according to the subject’s symptoms of leg pain if present. A posterolateral annulotomy was made and subtotal discectomy was performed and the hyaline cartilage of endplates was removed. Once the surgeon was satisfied with endplate preparation, a banana shaped allograft spacer was inserted through the annulotomy and placed anteriorly. Additional autograft locally harvested from decompression was packed behind the allograft spacer in all cases. Laminae and the remaining contralateral facet joint were decorticated, and packed with bone graft (local autologous and allograft chips in some cases). The posterior fusion was instrumented with pedicle screws and titanium rods. The TLIF procedure had led to shortened surgical times, less neurologic injury, and improved overall outcomes. The introduction of the TLIF procedure has allowed surgeons to achieve successful fusion without the risk of nerve root tethering that is seen so frequently with standard PLIF techniques.
doi:10.1007/s00586-011-1761-2
PMCID: PMC3087043  PMID: 21461695
TLIF; Minimal invasive fusion; Degenerative disc disease; Interbody fusion
11.  Lumbar interbody fusion: techniques, indications and comparison of interbody fusion options including PLIF, TLIF, MI-TLIF, OLIF/ATP, LLIF and ALIF 
Journal of Spine Surgery  2015;1(1):2-18.
Degenerative disc and facet joint disease of the lumbar spine is common in the ageing population, and is one of the most frequent causes of disability. Lumbar spondylosis may result in mechanical back pain, radicular and claudicant symptoms, reduced mobility and poor quality of life. Surgical interbody fusion of degenerative levels is an effective treatment option to stabilize the painful motion segment, and may provide indirect decompression of the neural elements, restore lordosis and correct deformity. The surgical options for interbody fusion of the lumbar spine include: posterior lumbar interbody fusion (PLIF), transforaminal lumbar interbody fusion (TLIF), minimally invasive transforaminal lumbar interbody fusion (MI-TLIF), oblique lumbar interbody fusion/anterior to psoas (OLIF/ATP), lateral lumbar interbody fusion (LLIF) and anterior lumbar interbody fusion (ALIF). The indications may include: discogenic/facetogenic low back pain, neurogenic claudication, radiculopathy due to foraminal stenosis, lumbar degenerative spinal deformity including symptomatic spondylolisthesis and degenerative scoliosis. In general, traditional posterior approaches are frequently used with acceptable fusion rates and low complication rates, however they are limited by thecal sac and nerve root retraction, along with iatrogenic injury to the paraspinal musculature and disruption of the posterior tension band. Minimally invasive (MIS) posterior approaches have evolved in an attempt to reduce approach related complications. Anterior approaches avoid the spinal canal, cauda equina and nerve roots, however have issues with approach related abdominal and vascular complications. In addition, lateral and OLIF techniques have potential risks to the lumbar plexus and psoas muscle. The present study aims firstly to comprehensively review the available literature and evidence for different lumbar interbody fusion (LIF) techniques. Secondly, we propose a set of recommendations and guidelines for the indications for interbody fusion options. Thirdly, this article provides a description of each approach, and illustrates the potential benefits and disadvantages of each technique with reference to indication and spine level performed.
doi:10.3978/j.issn.2414-469X.2015.10.05
PMCID: PMC5039869  PMID: 27683674
Degenerative disc disease; spine; interbody; lumbar spine fusion; posterior lumbar interbody fusion (PLIF); transforaminal lumbar interbody fusion (TLIF); minimally invasive transforaminal lumbar interbody fusion (MI-TLIF); lateral lumbar interbody fusion (LLIF); oblique lumbar interbody fusion (OLIF); anterior to psoas (ATP); anterior lumbar interbody fusion (ALIF)
12.  Microdialysis of paraspinal muscle in healthy volunteers and patients underwent posterior lumbar fusion surgery 
European Spine Journal  2009;18(11):1604-1609.
Paraspinal muscle damage is inevitable during conventional posterior lumbar fusion surgery. Minimal invasive surgery is postulated to result in less muscle damage and better outcome. The aim of this study was to monitor metabolic changes of the paraspinal muscle and to evaluate paraspinal muscle damage during surgery using microdialysis (MD). The basic interstitial metabolisms of the paraspinal muscle and the deltoid muscle were monitored using the MD technique in eight patients, who underwent posterior lumbar fusion surgery (six male and two female, median age 57.7 years, range 37–74) and eight healthy individuals for different positions (five male and three female, age 24.1 ± 0.8 years). Concentrations of glucose, glycerol, and lactate pyruvate ratio (L/P) in both tissues were compared. In the healthy group, the glucose and glycerol concentrations and L/P were unchanged in the paraspinal muscle when the body position changed from prone to supine. The glucose concentration and L/P were stable in the paraspinal muscle during the surgery. Glycerol concentrations increased significantly to 243.0 ± 144.1 μM in the paraspinal muscle and 118.9 ± 79.8 μM in the deltoid muscle in the surgery group. Mean glycerol concentration difference (GCD) between the paraspinal muscle and the deltoid tissue was 124.1 μM (P = 0.003, with 95% confidence interval 83.4–164.9 μM). The key metabolism of paraspinal muscle can be monitored by MD during the conventional posterior lumbar fusion surgery. The glycerol concentration in the paraspinal muscle is markedly increased compared with the deltoid muscle during the surgery. It is proposed that GCD can be used to evaluate surgery related paraspinal muscle damage. Changing body position did not affect the paraspinal muscle metabolism in the healthy subjects.
doi:10.1007/s00586-009-1021-x
PMCID: PMC2899392  PMID: 19418074
Glucose; Lactate pyruvate ratio; Glycerol; Paraspinal muscle; Microdialysis
13.  MRI assessment of paraspinal muscles in patients with acute and chronic unilateral low back pain 
Wan, Q | Lin, C | Li, X | Zeng, W | Ma, C
The British Journal of Radiology  2015;88(1053):20140546.
Objective:
To investigate the changes in paraspinal muscle cross-sectional area (CSA) and composition, using the digital data from lumbar spine MRIs of patients with acute and chronic low back pain (LBP).
Methods:
In total, 178 patients with unilateral LBP who had lumbar MRI examination were recruited. The data were obtained by a retrospective documentation audit. The CSAs and mean signal intensities of the bilateral paraspinal muscles [psoas major (PM), quadratus lumborum, multifidus (MF) and erector spinae (ES)] were measured, and the percentage of fat infiltration was calculated. The data between the painful side and non-painful side were compared, and between-group comparisons were tested. 42 patients with chronic unilateral LBP could indicate the problem level, and the CSA and mean signal intensity of the MF muscle were analysed at the problem level, and one vertebral above and one vertebral level below the problem level.
Results:
The CSAs of the PM and ES muscles were significantly decreased in the acute LBP group, while in the chronic LBP group, significant reduction in CSA was found in the MF and ES muscles on the painful side compared with the non-painful side. The mean signal intensity and fat content of the ES muscle on the painful side in the chronic LBP group was significantly higher than that on the painful side in the acute LBP group. The significant decrease of CSA in the MF muscle was found at multiple levels on the painful side.
Conclusion:
The present findings show that there is selective ipsilateral atrophy of paraspinal muscles, specific to the symptomatic side, in patients with acute and chronic LBP. The reduction of the muscle CSA and increased fatty infiltration occurred synchronously, and the extent of change is significantly greater in chronic LBP in the ES muscle. Atrophy of the MF muscle appears to be at multiple levels but side specific in relation to symptoms in patients with chronic LBP, and the decreased muscle CSA may occur prior to fatty infiltration.
Advances in knowledge:
There are specific paraspinal muscles undergoing atrophy and fatty infiltration in patients with acute and chronic LBP on the symptomatic side. The CSA of the MF muscle decreased at multiple levels on the symptomatic side in patients with chronic unilateral LBP, which may occur prior to fatty infiltration.
doi:10.1259/bjr.20140546
PMCID: PMC4743557  PMID: 26105517
14.  RESPONSE OF LUMBAR PARASPINAL MUSCLES SPINDLES IS GREATER TO SPINAL MANIPULATIVE LOADING COMPARED WITH SLOWER LOADING UNDER LENGTH CONTROL 
Background Context
Spinal manipulation (SM) is a form of manual therapy used clinically to treat patients with low back and neck pain. The most common form of this maneuver is characterized as a high velocity (duration < 150ms), low amplitude (segmental translation < 2mm, rotation < 4°, and applied force 220-889N) impulse thrust (HVLA-SM). Clinical skill in applying an HVLA-SM lies in the practitioner's ability to control the duration and magnitude of the load (i.e., the rate of loading), the direction in which the load is applied, and the contact point at which the load is applied. Control over its mechanical delivery presumably related to its clinical effects. Biomechanical changes evoked by an HVLA-SM are thought to have physiological consequences caused, at least in part, by changes in sensory signaling from paraspinal tissues.
Purpose
If activation of afferent pathways does contribute to the effects of an HVLA-SM, it seems reasonable to anticipate that neural discharge might increase or decrease in a non-linear fashion as the thrust duration thrust approaches a threshold value. We hypothesized that the relationship between the duration of an impulsive thrust to a vertebra and paraspinal muscle spindle discharge would be non-linear with an inflection near the duration of an HVLA-SM delivered clinically (<150ms). In addition, we anticipated that muscle spindle discharge would be more sensitive to larger amplitude thrusts.
Study Design/Setting
A neurophysiological study of spinal manipulation using the lumbar spine of a feline model.
Methods
Impulse thrusts (duration: 12.5, 25, 50, 100, 200, and 400 ms; amplitude 1 or 2mm posterior to anterior) were applied to the spinous process of the L6 vertebra of deeply anesthetized cats while recording single unit activity from dorsal root filaments of muscle spindle afferents innervating the lumbar paraspinal muscles. A feedback motor was used in displacement control mode to deliver the impulse thrusts. The motor's drive arm was securely attached to the L6 spinous process via a forceps.
Results
As thrust duration became shorter the discharge of the lumbar paraspinal muscle spindles increased in a curvilinear fashion. A concave up inflection occurred near the 100ms duration eliciting both a higher frequency discharge compared to the longer durations and a substantially faster rate of change as thrust duration was shortened. This pattern was evident in paraspinal afferents with receptive fields both close and far from the midline. Paradoxically, spindle afferents were almost twice as sensitive to the 1mm compared to the 2mm amplitude thrust (6.2 vs 3.3 spikes/s/mm/s). This latter finding may be related to the small vs large signal range properties of muscle spindles.
Conclusions
. The results indicate that the duration and amplitude of a spinal manipulation elicits a pattern of discharge from paraspinal muscle spindles different from slower mechanical inputs. Clinically, these parameters may be important determinants of an HVLA-SM's therapeutic benefit.
doi:10.1016/j.spinee.2006.10.006
PMCID: PMC2075482  PMID: 17905321
lumbar spine; spinal manipulation; chiropractic; osteopathy; paraspinal muscles; muscle spindle
15.  Factors affecting the accurate placement of percutaneous pedicle screws during minimally invasive transforaminal lumbar interbody fusion 
European Spine Journal  2011;20(10):1635-1643.
We retrospectively evaluated 488 percutaneous pedicle screws in 110 consecutive patients that had undergone minimally invasive transforaminal lumbar interbody fusion (MITLIF) to determine the incidence of pedicle screw misplacement and its relevant risk factors. Screw placements were classified based on postoperative computed tomographic findings as “correct”, “cortical encroachment” or as “frank penetration”. Age, gender, body mass index, bone mineral density, diagnosis, operation time, estimated blood loss (EBL), level of fusion, surgeon’s position, spinal alignment, quality/quantity of multifidus muscle, and depth to screw entry point were considered to be demographic and anatomical variables capable of affecting pedicle screw placement. Pedicle dimensions, facet joint arthritis, screw location (ipsilateral or contralateral), screw length, screw diameter, and screw trajectory angle were regarded as screw-related variables. Logistic regression analysis was conducted to examine relations between these variables and the correctness of screw placement. The incidence of cortical encroachment was 12.5% (61 screws), and frank penetration was found for 54 (11.1%) screws. Two patients (0.4%) with medial penetration underwent revision for unbearable radicular pain and foot drop, respectively. The odds ratios of significant risk factors for pedicle screw misplacement were 3.373 (95% CI 1.095–10.391) for obesity, 1.141 (95% CI 1.024–1.271) for pedicle convergent angle, 1.013 (95% CI 1.006–1.065) for EBL >400 cc, and 1.003 (95% CI 1.000–1.006) for cross-sectional area of multifidus muscle. Although percutaneous insertion of pedicle screws was performed safely during MITLIF, several risk factors should be considered to improve placement accuracy.
doi:10.1007/s00586-011-1892-5
PMCID: PMC3175862  PMID: 21720727
Risk factor; Percutaneous; Pedicle screw; Minimally invasive; TLIF
16.  Anatomical study of the paraspinal approach to the lumbar spine 
European Spine Journal  2004;14(4):366-371.
The original description of the paraspinal posterior approach to the lumbar spine was for spinal fusion, especially regarding lumbosacral spondylolisthesis treatment. In spite of the technical details described by Wiltse, exact location of the area where the sacrospinalis muscle has to be split remains somewhat unclear. The goal of this study was to provide topographic landmarks to facilitate this surgical approach. Thirty cadavers were dissected in order to precisely describe the anatomy of the trans-muscular paraspinal approach. The level of the natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was noted and measurements were done between this level and the midline at the level of the spinous process of L4. A natural cleavage plane between the multifidus and the longissimus part of the sacrospinalis muscle was present in all cases. There was a fibrous separation between the two muscular parts in 55 out of 60 cases. The mean distance between the level of the cleavage plane and the midline was 4 cm (2.4–5.5 cm). In all cases, small arteries and veins were present, precisely at the level of the cleavage plane. We found it possible to easily localize the anatomical cleavage plane between the multifidus part and the longissimus part of the sacrospinalis muscle. First the superficial muscular fascia is opened near the midline, exposing the posterior aspect of the sacrospinalis muscle. Then, the location of the muscular cleft can be found by identifying the perforating vessels leaving the anatomical inter-muscular space.
doi:10.1007/s00586-004-0802-5
PMCID: PMC3489211  PMID: 15526219
Paraspinal approach; Lumbar spine; Lumbosacral spondylolisthesis; Sacrospinalis muscle; Minimally invasive approach
17.  Transdural retrieval of a retropulsed lumbar interbody cage: Technical case report 
The purpose of this case report was to describe a novel method to retrieve a herniated lumbar interbody cage. Transforaminal lumbar interbody fusion (TLIF) is an increasingly popular method of spinal fixation and fusion. Unexpected retropulsion of an interbody is a rare event that can result in intractable pain or motor compromise necessitating surgical retrieval of the interbody. Both anterior and posterior approaches to removing migrated cages may be associated with significant surgical morbidity and mortality. A 60-year-old woman underwent an L4-S1 TLIF coupled with pedicle screw fixation at a previous hospital 5 years prior to admission. She noted sudden-onset bilateral lower extremity weakness and right-sided foot drop. Magnetic resonance imaging and radiographs were notable for purely centrally herniated interbody. A posterior, midline transdural approach was used to retrieve the interbody. Situated in between nerve rootlets to the ventral canal, this virgin corridor allowed us to easily visualize and protect neurological structures while safely retrieving the interbody. The patient experienced an immediate improvement in symptoms and was discharged on postoperative day 3. At 12-month follow-up, she had no evidence of cerebrospinal fluid (CSF) leak and had returned to normal activities of daily living. While the risk of CSF leak may be higher with a transdural approach, we maintain that avoiding unnecessary retraction of the nerve roots may outweigh this risk. To our knowledge, this is the first case report of a transdural approach for the retrieval of a retropulsed lumbar interbody cage.
doi:10.4103/1793-5482.165802
PMCID: PMC4732253  PMID: 26889290
Cage migration; lumbar interbody; transdural approach
18.  Multifidus muscle changes and clinical effects of one-level posterior lumbar interbody fusion: minimally invasive procedure versus conventional open approach 
European Spine Journal  2009;19(2):316-324.
We set out to determine whether a minimally invasive approach for one-level instrumented posterior lumbar interbody fusion reduced undesirable changes in the multifidus muscle, compared to a conventional open approach. We also investigated associations between muscle injury during surgery (creatinine kinase levels), clinical outcome and changes in the multifidus at follow-up. We studied 59 patients treated by one team of surgeons at a single institution (minimally invasive approach in 28 and conventional open approach in 31, voluntarily chosen by patients). More than 1 year postoperatively, all the patients were followed up with the visual analogue scale (VAS) and Oswestry disability index (ODI), and 16 patients from each group were evaluated using MRI. This enabled the cross-sectional area (CSA) of lean multifidus muscle, and the T2 signal intensity ratio of multifidus to psoas muscle, to be compared at the operative and adjacent levels. The minimally invasive group had less postoperative back pain (P < 0.001) and lower postoperative ODI scores (P = 0.001). Multifidus atrophy was less in the minimally invasive group (P < 0.001), with mean reductions in CSA of 12.2% at the operative and 8.5% at the adjacent levels, compared to 36.8% and 29.3% in the conventional open group. The increase in the multifidus:psoas T2 signal intensity ratio was similarly less marked in the minimally invasive group where values increased by 10.6% at the operative and 8.3% at the adjacent levels, compared to 34.4 and 22.7% in the conventional open group (P < 0.001). These changes in multifidus CSA and T2 signal intensity ratio were significantly correlated with postoperative creatinine kinase levels, VAS scores and ODI scores (P < 0.01). The minimally invasive approach caused less change in multifidus, less postoperative back pain and functional disability than conventional open approach. Muscle damage during surgery was significantly correlated with long-term multifidus muscle atrophy and fatty infiltration. Furthermore these degenerative changes of multifidus were also significantly correlated with long-term clinical outcome.
doi:10.1007/s00586-009-1191-6
PMCID: PMC2899808  PMID: 19876659
Minimally invasive; Lumbar spine; Multifidus muscle; Interbody fusion
19.  Endoscopic transforaminal decompression, interbody fusion, and percutaneous pedicle screw implantation of the lumbar spine: A case series report 
Background
On the basis of the experiences gained from conventional open spinal procedures, a long list of desirable objectives have emerged with the evolution of the lesser invasive spinal procedures. At the top of that list is the desire to minimize the trauma of surgery. The rest of the objectives, which include reductions of operating time, surgical blood loss, hospital stay, postoperative narcotic medication, convalescence, complication rates, and escalating health care costs, as well as the desire of elderly patients to continue rigorous physical activities, largely depend on the ability to minimize the trauma of surgery. The purpose of this study was to investigate the feasibility of the least invasive lumbar decompression, interbody fusion and percutaneous pedicle screw implantation, to minimize surgical trauma without compromising the quality of the treatment outcome, as well as to minimize risk of complications.
Methods
In this case series, 60 patients with diagnoses of degenerative disc disease, degenerative motion segments with stenosis, and spondylolisthesis, in whom nonoperative treatments failed, were treated with endoscopic transforaminal decompression and interbody fusion by 1 surgeon in 2 centers. The outcome measures were as follows: operating time, intraoperative blood loss, hospital stay, Visual Analogue Scale (VAS) scores for back and leg pain, scores on the Roland-Morris Disability Questionnaire, and postoperative imaging studies. A consecutive series of patients who met the treatment criteria completed VAS forms and Roland-Morris questionnaires preoperatively. Surgical procedures included arthroscopic decompression of the foramina and the discs; endplate preparation and implantation of allograft bone chips and bone morphogenetic protein 2 on absorbable collagen sponge into the disc space; and percutaneous implantation of pedicle screws. Postoperatively, the patients again completed the VAS forms and Roland-Morris questionnaires. Their charts were reviewed for office notes, operative notes, hospital stay, medications, and imaging studies. The latest X-ray and computed tomography scan films were reviewed and analyzed. Patients were followed up for a minimum of 6 months. The literature was reviewed for comparison of outcomes.
Results
Sixty patients met the inclusion criteria. The mean age was 52.8 years. The duration of illness averaged 5 years. Follow-up ranged from 6 to 25 months, with a mean of 12 months. Preoperative diagnoses included degenerative disc disease, degenerative motion segments with stenosis, and spondylolisthesis. The mean time in the operating room was 2 hours 54 minutes. Estimated blood loss averaged 57.6 mL. The duration of the hospital stay averaged 2.6 days. Preoperative back pain and leg pain were significantly reduced (P < .005). Forty-seven imaging studies obtained at the last visit, including X-ray and computed tomography scans, showed solid fusion in 28 patients (59.6%), stable fixation in 17 (36.2%), and osteolysis around the pedicle screws in 2 (4.2%). All patients had improvement of motor function, whereas 2 patients complained of residual numbness. In addition, 8 patients (13%) complained of residual discomfort on extension of the lumbar spine. Two patients had pedicle screw–related complications requiring surgery. A review of the literature showed that endoscopic transforaminal decompression and interbody fusion performed better than open transforaminal lumbar interbody fusion/posterior lumbar interbody fusion, minimally invasive transforaminal lumbar interbody fusion, and extreme lateral lumbar interbody fusion, with regard to most parameters studied.
Conclusions
The endoscopic transforaminal lumbar decompression, interbody fusion, and percutaneous pedicle screw instrumentation consistently produced satisfactory results in all demographics. It performed better than the alternative procedures for most parameters studied.
doi:10.1016/j.ijsp.2012.04.001
PMCID: PMC4300894  PMID: 25694885
ETDIF; Arthroscopic; Posterolateral; Interbody; Percutaneous; BMP-2
20.  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.
doi:10.3340/jkns.2013.54.2.128
PMCID: PMC3809439  PMID: 24175028
Cage; Transforaminal lumbar interbody fusion; Spondylolisthesis; Lumbosacral spine; Transitional vertebra
21.  Minimally invasive transforaminal lumbar interbody fusion 
Indian Journal of Orthopaedics  2014;48(6):562-567.
Background:
The use of minimally invasive surgical (MIS) techniques represents the most recent modification of methods used to achieve lumbar interbody fusion. The advantages of minimally invasive spinal instrumentation techniques are less soft tissue injury, reduced blood loss, less postoperative pain and shorter hospital stay while achieving clinical outcomes comparable with equivalent open procedure. The aim was to study the clinicoradiological outcome of minimally invasive transforaminal lumbar interbody fusion.
Materials and Methods:
This prospective study was conducted on 23 patients, 17 females and 6 males, who underwent MIS-transforaminal lumbar interbody fusion (TLIF) followed up for a mean 15 months. The subjects were evaluated for clinical and radiological outcome who were manifested by back pain alone (n = 4) or back pain with leg pain (n = 19) associated with a primary diagnosis of degenerative spondylolisthesis, massive disc herniation, lumbar stenosis, recurrent disc herniation or degenerative disc disease. Paraspinal approach was used in all patients. The clinical outcome was assessed using the revised Oswestry disability index and Macnab criteria.
Results:
The mean age of subjects was 55.45 years. L4-L5 level was operated in 14 subjects, L5-S1 in 7 subjects; L3-L4 and double level was fixed in 1 patient each. L4-L5 degenerative listhesis was the most common indication (n = 12). Average operative time was 3 h. Fourteen patients had excellent results, a good result in 5 subjects, 2 subjects had fair results and 2 had poor results. Three patients had persistent back pain, 4 patients had residual numbness or radiculopathy. All patients had a radiological union except for 1 patient.
Conclusion:
The study demonstrates a good clinicoradiological outcome of minimally invasive TLIF. It is also superior in terms of postoperative back pain, blood loss, hospital stay, recovery time as well as medication use.
doi:10.4103/0019-5413.144217
PMCID: PMC4232824  PMID: 25404767
Degenerative spine; lumbar fusion; minimally invasive transforaminal lumbar interbody fusion; spondylolisthesis; Spinal arthritis; spondyloarthritis; spondylolisthesis; minimally invasive; spinal fusion
22.  Regional Myosin Heavy Chains Distribution in Selected Paraspinal Muscles 
Spine  2010;35(13):1265-1270.
Study Design
Cross-sectional study with repeated measures design.
Objective
To compare the myosin heavy chain isoform distribution within and between paraspinal muscles and to test the theory that fiber type gradients exist as a function of paraspinal muscle depth.
Summary of Background Data
There is still uncertainty regarding the fiber type distributions within different paraspinal muscles. It has been previously proposed that deep fibers of the multifidus muscle may contain a higher ratio of type I to type II fibers, because, unlike superficial fibers, they primarily stabilize the spine, and may therefore have relatively higher endurance. Using a minimally invasive surgical approach, utilizing tubular retractors that are placed within anatomic inter-muscular planes, it was feasible to obtain biopsies from the multifidus, longissimus, iliocostalis and psoas muscles at specific predefined depths.
Methods
Under an IRB approved protocol, muscle biopsies were obtained from 15 patients who underwent minimally invasive spinal surgery, using the posterior paramedian (Wiltse) approach or the minimally invasive lateral approach. Myosin heavy chain (MyHC) isoform distribution was analyzed using SDS-PAGE electrophoresis. Since multiple biopsies were obtained from each patient, MyHC distribution was compared using both within- and between-muscle repeated measures analyses.
Results
The fiber type distribution was similar among the posterior paraspinal muscles and was composed of relatively high percentage of type I (63%), compared to type IIA (19%) and type IIX (18%) fibers. In contrast, the psoas muscle was found to contain a lower percentage of type I fibers (42%) and a higher percentage of type IIA (33%) and IIX fibers (26%; P<0.05). No significant difference was found for fiber type distribution among three different depths of the multifidus and psoas muscles.
Conclusion
Fiber type distribution between the posterior paraspinal muscles is consistent and is composed of relatively high percentage of type I fibers, consistent with a postural function. The psoas muscle, on the other hand, is composed of a higher percentage of type II fibers such as in the appendicular muscles. Our data do not support the idea of a fiber type gradient as a function of depth for any muscle studied.
doi:10.1097/BRS.0b013e3181bfcd98
PMCID: PMC2947743  PMID: 20461040
Lumbar multifidus; Muscle mechanics; Lumbar spine
23.  A Comparison of Surgical Invasions for Spinal Nerve Ligation with or without Paraspinal Muscle Removal in a Rat Neuropathic Pain Model 
BioMed Research International  2016;2016:6741295.
L5 spinal nerve ligation (SNL) in rats is one of the most popular models for studying neuropathic pain because of its high reproducibility. During the surgery, a part of the L5 paraspinal muscle is usually removed, which produces extra trauma and may potentially affect the physiological processes involved in neuropathic pain. To reduce the surgical trauma, the paraspinal muscle retraction was developed for exposure of the spinal nerve. The current study was aimed at comparing the surgical invasions between the L5 SNL models with paraspinal muscle removal or retraction. The results showed that both methods induced similar neuropathic pain behavior. However, the paraspinal muscle retraction group exhibited an average of 2.7 mg less blood loss than the muscle removal group. This group also showed a significantly lower increase in serum myoglobin and creatine phosphokinase levels on postoperative days 1 and 2, as well as a lower increase in interleukin-1β and interleukin-6 levels on postoperative day 1. The paraspinal muscle maintained normal morphological features following paraspinal muscle retraction. Our results indicate that the SNL rat model with paraspinal muscle retraction is a reliable physiological model that is reproducible, readily available, and less invasive than the model with muscle removal.
doi:10.1155/2016/6741295
PMCID: PMC4997083  PMID: 27597970
24.  Bilateral decompression using a unilateral pedicle construct for lumbar stenosis 
International Orthopaedics  2013;38(3):573-578.
Purpose
To determine the effectiveness of bilateral decompression via a unilateral approach using unilateral pedicle screw fixation for two-level lumbar stenosis with instability.
Methods
Between October 2006 and October 2010, 98 patients (61 men and 37 women) who had reached the three-year follow-up interval were treated with unilateral pedicle screw fixation at the authors’ institution. All patients underwent two-level transforaminal lumbar interbody fusion (TLIF), and the mean age was 59.6 years (range, 40–72). Visual analog scale (VAS) scores and Oswestry Disability Index (ODI) were used to assess the pre-operative and postoperative clinical results. Fusion status, the disc space height, and the whole lumbar lordotic angle were analysed for the radiological evaluation.
Results
The ODI scores decreased significantly in both early and late follow-up evaluations and the visual analog scale (VAS) score demonstrated significant improvement in late follow-up (P < 0.01). The disc space height (P < 0.05) and the whole lumbar lordotic angle (P < 0.05) were increased at the final follow-up. Successful fusion was achieved in all patients.
Conclusion
Bilateral decompression via a unilateral approach using unilateral pedicle screw fixation for two-level lumbar stenosis with instability, which can maintain the lumbar lordosis and the disc space height, is an effective and less invasive method than with bilateral constructs.
doi:10.1007/s00264-013-2225-6
PMCID: PMC3936069  PMID: 24337752
Unilateral; Transforaminal lumbar interbody fusion; Lumbar stenosis; Invasive
25.  100 Consecutive Cases of Degenerative Lumbar Conditions Using a Non-Threaded Locking Screw System With a 90-Degree Locking Cap 
SAS Journal  2009;3(1):1-11.
Background
This prospective study analyzes the perioperative outcomes and long-term fusion success of 100 consecutive lumbar degenerative cases. The cases were managed using a non-threaded locking screw system, in conjunction with polyetheretherketone (PEEK) cages, for posterior lumbar interbody fusion (PLIF) procedures. These 100 cases were compared to another prospective study treating patients with the same inclusion and exclusion criteria using conventional plate-based pedicle screw spinal instrumentation augmented with carbon fiber interbody cages.
Methods
A total of 167 operative levels were treated in 100 patients (51 single-level, 39 two-level and 10 three-level cases). Eleven cases were revisions and 67 patients received interbody fusion cages. Patients had an average of 22.8 ± 4.0 months followup. Results: There was one instrumentation failure but no significant subsidence at the interbody fusion level. The disc space height was restored as part of the surgical procedure at the interbody cage levels: from 7.5 ± 2.3 mm preoperative to 9.0 ± 2.1 mm postoperative. There were 2 cases of pseudarthrosis (2 / 100 = 2%). The average operative time for 1-level cases was 111 ± 25 minutes; for 2-level cases it was 132.4 ± 21.8 minutes; and for 3-level cases it was 162.6 ± 33 minutes. Blood loss averaged 800 ± 473 cc for 1-level cases, 1055 ± 408 cc for 2 levels, and 1155 ± 714 cc for 3 levels. The length of stay was similar between the 3 groups (4.4 ± 1.2 days for single-level cases, 4.7 ± 1.1 for 2 levels, and 5.0 ± 1.1 for 3 levels; P > .05). There were 3 incidental durotomies, and 4 other patients developed infections postoperatively that required reoperation.
Conclusion
The disc and foraminal heights can be restored and maintained with a unilateral cage and pedicle screw construct. Unilateral transforaminal lumbar interbody fusion using a PEEK cage combined with a non-threaded locking pedicle screw and rod system results in similar fusion rates to those achieved using the bilateral Brantigan interbody fusion cage or a single BAK Vista implant. When compared to the bilateral Brantigan cages, decreased operative time (P < .001), decreased blood loss (P < .001) and reduced incidence of dural tears (P < .001) are advantages of using a non-threaded locking screw system and single PEEK interbody cage for lumbar degenerative conditions without compromising subsequent fusion rates.
doi:10.1016/SASJ-2008-0022-RR
PMCID: PMC4365587  PMID: 25802623
Deformity; Interbody Fusion; Spinal Instrumentation

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