The quantitative analysis of back muscle degeneration after posterior lumbar fusion: comparison of minimally invasive and conventional open surgery

Fatty Infiltration in Paraspinal Muscles: Predicting the Outcome of Lumbar Surgery and Postoperative Complications

Lumbar spine disorders often cause lower back pain, lower limb radiating pain, restricted movement, and neurological dysfunction, which seriously affect the quality of life of middle-aged and older people. It has been found that pathological changes in the spine often cause changes in the morphology and function of the paraspinal muscles (PSMs). Fatty infiltration (FI) in PSMs is closely associated with disc degeneration and Modic changes. And FI causes inflammatory responses that exacerbate the progression of lumbar spine disease and disrupt postoperative recovery. Magnetic resonance imaging can better distinguish between fat and muscle tissue with the threshold technique. Three-dimensional magnetic resonance imaging multi-echo imaging techniques such as water-fat separation and proton density are currently popular for studying FI. Muscle fat content obtained based on these imaging sequences has greater accuracy, visualization, acquisition speed, and utility. The proton density fat fraction calculated from these techniques has been shown to evaluate more subtle changes in PSMs. Magnetic resonance spectroscopy can accurately reflect the relationship between FI and the degeneration of PSMs by measuring intracellular and extracellular lipid values to quantify muscle fat. We have pooled and analyzed published studies and found that patients with spinal disorders often exhibit FI in PSMs. Some studies suggest an association between FI and adverse surgical outcomes, although conflicting results exist. These suggest that clinicians should consider FI when assessing surgical risks and outcomes. Future studies should focus on understanding the biological mechanisms underlying FI and its predictive value in spinal surgery, providing valuable insights for clinical decision-making.

Does Conventional Open TLIF cause more Muscle Injury when Compared to Minimally Invasive TLIF?-A Prospective Single Center Analysis

STUDY DESIGN

Prospective, observational.

OBJECTIVES

The aim of our study was to assess the amount of reduction in lean muscle mass (LMM) of multifidus muscle (MFM) between conventional open Transforaminal lumbar interbody fusion (CO-TLIF) as compared to Minimally invasive spine Transforaminal lumbar interbody fusion (MIS-TLIF).

METHODS

This study was conducted between 2017 and 2020. It included 100 patients divided into two groups, 50 patients treated with CO-TLIF, 50 treated with MIS-TLIF. Only patients undergoing single level, primary lumbar fusion at L4-5 or L5-S1 level for degenerative pathologies were included. All patients were assessed by magnetic resonance imaging (MRI) scans 1-year post surgery. Measurements were performed using ImageJ image processing program.

RESULTS

Mean percentage reduction in LMM in CO-TLIF group was 45.52 ± 12.36% and MIS-TLIF group was 25.83 ± 9.64% [statistically significant (t = 8.78, P < .001)]. Mean percentage reduction in LMM on side of cage insertion was 39.63 ± 15.96% and opposite side was 31.40 ± 15.01% [statistically significant (t = 9.06, P < .001)]. Mean reduction of LMM among males was 29.38 ± 15.23% and females was 40.42 ± 12.67% [statistically significant (t = -3.95, P < .001)].We observed significant but weak degree of correlation between age and percentage reduction of LMM (r = .22, P = .028).

CONCLUSION

Mean reduction in LMM was greater in CO-TLIF group as compared to MIS-TLIF. There was greater reduction in LMM in females and on side of cage insertion. We also found greater reduction in LMM with increasing age in both groups.

Association between history of lumbar spine surgery and paralumbar muscle health: a propensity score-matched analysis

BACKGROUND CONTEXT

Prior studies have suggested that muscle strength and quality may be associated with low back pain. Recently, a novel magnetic resonance imaging (MRI)-based lumbar muscle health grade was shown to correlate with health-related quality of life scores after spine surgery. However, the potential association between history of lumbar spine surgery and paralumbar muscle health requires further investigation.

PURPOSE

To compare MRI-based paralumbar muscle health parameters between patients with versus without a history of surgery for degenerative lumbar spinal disease.

STUDY DESIGN/SETTING

Retrospective cohort study.

PATIENT SAMPLE

Consecutive series of patients who presented to the spine surgery clinic of a single surgeon.

OUTCOME MEASURES

MRI-based measurements of paralumbar cross-sectional area (PL-CSA), Goutallier grade, lumbar indentation value (LIV).

METHODS

A retrospective analysis was performed on a consecutive series of patients of a single surgeon, and patients were included based on availability of lumbar MRI. Axial T2-weighted lumbar MRIs were analyzed for PL-CSA, Goutallier classification, and LIV. Measurements were performed at the center of disc spaces from L1 to L5. Patients with and without history of spine surgery were matched based on age, sex, race, ethnicity, and body mass index (BMI) via propensity score matching. Normality of each muscle health variable was assessed using Kolmogorov-Smirnov test. Mann-Whitney U test or independent t-test performed to compare the matched cohorts, as appropriate.

RESULTS

A total of 615 patients were assessed. For final analysis, 89 patients with a history of previous spine surgery were matched with 89 patients without a history of spine surgery. There were no statistically significant differences in age, sex, race, ethnicity, or BMI between the matched cohorts. History of spine surgery was generally associated with worse lumbar muscle health. At all 4 intervertebral levels between L1-L5, PL-CSA was significantly smaller among patients with history of spine surgery. At L4-L5, patients with prior spine surgery had significantly smaller PL-CSA/BMI. Patients with prior spine surgery were found to have greater fatty infiltration of the muscles, with higher average Goutallier grades at levels L1-L2, L2-L3, and L4-L5. In addition, history of spine surgery was associated with smaller LIV at L1-L2, L3-L4, and L4-L5.

CONCLUSIONS

The current study demonstrates that history of lumbar spine surgery is associated with worse paralumbar muscle health based on quantitative and qualitative measurements on MRI. On average, patients with history of spine surgery were found to have smaller cross-sectional areas of the paralumbar muscles, greater amounts of fatty infiltration based on Goutallier classification, and smaller lumbar indentation values.

Comparison between OLIF and MISTLIF in degenerative lumbar stenosis: an age-, sex-, and segment-matched cohort study

To compare outcomes after oblique lateral interbody fusion (OLIF) versus minimally invasive transforaminal lumbar interbody fusion (MISTLIF) with bilateral decompression via unilateral approach for treating mild to moderate symptomatic degenerative lumbar spinal stenosis (DLSS). We retrospectively compared patients who underwent single-level (L4/5) OLIF with an age-, sex-, and segment-matched MISTLIF with bilateral decompression via unilateral approach cohort. Perioperative data were collected for the operative time, intraoperative blood loss, drainage in the first postoperative day, postoperative hospital stay, cost, intraoperative fluoroscopy, and complications. Lumbar radiographs were measured for changes in posterior intervertebral space height (PISH), intervertebral space foramen height (IFH), intervertebral foramen area (IFA), and area of the spinal canal (ASC). Clinical and psychological outcomes included the visual analog scale (VAS), Oswestry Disability Index (ODI), and hospital anxiety and depression scale (HADS). 35 OLIF patients were compared with 35 MISTLIF patients in L4/5 DLSS. The OLIF group had shorter bedtime, postoperative hospital stays, less intraoperative and postoperative blood loss (all P < 0.05), but had more times of intraoperative fluoroscopy, longer operative time, and higher cost (all P < 0.05). The complication rates were equivalent (OLIF vs MISTLIF: 22.86% vs 17.14%). PISH (11.94 ± 1.78 mm vs 9.42 ± 1.94 mm, P < 0.05), IFH (23.87 ± 3.05 mm vs 21.41 ± 2.95 mm, P < 0.05), and IFA (212.14 ± 51.82 mm2 vs 177.07 ± 51.73 mm2, P < 0.05) after surgery were significantly increased in the OLIF group. The ASC was increased significantly after the operation in both groups, but the ASC in the MISTLIF group was increased significantly more than that in the OLIF group (450.04 ± 66.66 mm2 vs 171.41 ± 58.55 mm2, P < 0.05). The lumbar VAS scores at 1 month (1.89 ± 0.87 vs 2.34 ± 0.84, P = 0.028) and 6 months (1.23 ± 0.97 vs 1.80 ± 0.99, P = 0.018) after operation in the OLIF group were significantly lower. There were no significant differences in lower extremity VAS and ODI scores between the two groups. Compared with MISTLIF group, HADS scores on postoperative day 3 (2.91 ± 1.46 vs 4.89 ± 1.78, P < 0.05) and prior to hospital discharge (PTD) (2.54 ± 1.38 vs 3.80 ± 1.78, P = 0.002) in the OLIF group were decreased significantly. OLIF showed more advantages of less surgical invasion, lower incidence of postoperative low back pain, faster postoperative recovery, and less anxiety compared with MISTLIF. Regardless of cost, OLIF seems to be a better option to treat mild to moderate symptomatic DLSS.

Comparisons of Lumbar Muscle Performance Between Minimally-Invasive and Open Lumbar Fusion Surgery at 1-Year Follow-Up

STUDY DESIGN

Prospective study.

OBJECTIVE

Minimally-invasive lumbar fusion surgery (MIS) is a viable alternative to conventional open surgery (COS) for spinal disorders. Although MIS seems to be associated with less para-spinal muscle trauma, the actual back muscle performance after MIS and COS remain controversial. This study investigated post-operative para-spinal muscle performance, and the correlation between muscle dysfunction and clinical outcome.

METHODS

In this prospective, non-randomized control study, 50 patients were enrolled and split into 2 groups: COS and MIS. We established a biomechanical model of the para-spinal muscle in the lumbar spine using electromyography (EMG) and specific muscle function tests. Functional outcomes were also reviewed and analyzed. All patients underwent EMG pre-operatively, and at 3 months and 1 year post-operatively. The para-spinal muscle performance was investigated by comparing the back muscle co-contraction ratio and the load transmission zone to the pre-operative data.

RESULTS

Twenty-one patients in the COS group and 25 in the MIS group completed the study. Both groups showed a significant improved functional score. The abdominal and back muscle strengths were decreased post-operatively, and were then increased at 12 months post-operatively in both groups. During the perturbed balance task and static task, the MIS group exhibited a trend of recovery in comparison with the COS group. But, the back muscle performance at 12 months was poorer than the pre-op performance in both groups.

CONCLUSIONS

There was no significant difference in clinical outcome and para-spinal muscle performance between groups. In both methods, the global muscle function had declined post-operatively.

Magnetic Resonance Imaging Documentation of Approach Trauma With Lumbar Endoscopic Interlaminar, Translaminar, Compared to Open Microsurgical Discectomy

BACKGROUND

Endoscopic spine surgery is associated with less approach trauma than conventional open translaminar surgery. However, objective evidence to corroborate this empiric observation is scarce. Preservation of the anatomic attachment and sensory function of multifidus muscles have been stipulated to be critical to maintaining the normal function of the lumbar spinal motion segment. The authors were interested in comparing the postoperative approach trauma between traditional open translaminar microsurgical and interlaminar endoscopic discectomy.

METHODS

The approach trauma to the paraspinal muscles due to interlaminar or open microsurgical discectomy was evaluated on T2-weighted axial magnetic resonance imaging (MRI) images of 39 consecutive patients who underwent lumbar disc surgery. Postoperative MRI images taken at 4 days and within 1 year after surgery were analyzed. Eleven patients underwent conventional open translaminar microdiscectomy surgery. Endoscopic discectomy was performed on 17 patients via the interlaminar and on another 11 patients via the transforaminal approach. The immediate surgical approach trauma was estimated as the defect zone by measuring the normalized relative cross-sectional area (rCSA) of muscle disruption in the surgical corridor 4 days postoperatively. The long-term effect of surgical approach trauma was assessed by measuring the area of the paraspinal muscles that had been replaced by fatty tissue 1 year postoperatively.

RESULTS

The rCSA data showed diminished approach trauma with a smaller surgical defect zone in the interlaminar endoscopy group (17.6%) was smaller than in the microsurgical group 4 days postoperatively (41.2%). At 1 year postoperatively, the mean fatty replacement of the paraspinal muscles was 23.6% after microsurgery and 2.1% after the interlaminar endoscopy. Muscle recovery was substantially reduced in the interlaminar endoscopic group, with the muscle zone reducing from 20.3% to 2.1% when analyzed 1 year postoperatively. In the microsurgery group, the muscle damage by atrophy increased from 41.2% to 62.9% at 1 year postoperatively (P < 0.001). Fatty replacement of the multifidus muscle was seen on the ipsilateral and contralateral approach side. There was a negligible change in the muscle zone with the transforaminal approach.

CONCLUSIONS

Tissue trauma was significantly reduced with endoscopic surgery techniques compared with the traditional translaminar microdiscectomy approach. There was a minor postoperative tissue trauma and hardly any long-term replacement of the multifidus and paraspinal muscles by fatty tissue 1 year postoperatively with the endoscopic technique. The transforaminal approach has the least effect on the paraspinal muscles of the surgical motion segment. Further study is needed to investigate whether these findings translate into decreased postoperative instability or low back pain following endoscopic discectomy surgery.

CLINICAL RELEVANCE

MRI analysis of multifidus atrophy following various lumbar translaminar and transforaminal decompression techniques.

LEVEL OF EVIDENCE: 3

Minimally invasive versus open transforaminal lumbar interbody fusion: a prospective, controlled observational study of short-term outcome

Instrumented stabilization with intersomatic fusion can be achieved by open (O-TLIF) or minimally invasive (MIS-TLIF) transforaminal surgical access. While less invasive techniques have been associated with reduced postoperative pain and disability, increased manipulation and insufficient decompression may contradict MIS techniques. In order to detect differences between both techniques in the short-term, a prospective, controlled study was conducted. Thirty-eight patients with isthmic or degenerative spondylolisthesis or degenerative disk disease were included in this prospective, controlled study (15 MIS-TLIF group vs. 23 O-TLIF group) after failed conservative treatment. Patients were examined preoperatively, on the first, third, and sixth postoperative day as well as after 2, 4, and 12 weeks postoperatively. Outcome parameters included blood loss, duration of surgery, pre- and postoperative pain (numeric rating scale [NRS], visual analog scale [VAS]), functionality (Timed Up and Go test [TUG]), disability (Oswestry Disability index [ODI]), and quality of life (EQ-5D). Intraoperative blood loss (IBL) as well as postoperative blood loss (PBL) was significantly higher in the O-TLIF group ([IBL O-TLIF 528 ml vs. MIS-TLIF 213 ml, p = 0.001], [PBL O-TLIF 322 ml vs. MIS-TLIF 30 ml, p = 0.004]). The O-TLIF cohort showed significantly less leg pain postoperatively compared to the MIS-TLIF group ([NRS leg 3rd postoperative day, p = 0.027], [VAS leg 12 weeks post-op, p = 0.02]). The MIS group showed a significantly better improvement in the overall ODI (40.8 ± 13 vs. 56.0 ± 16; p = 0.05). After 3 months in the short-term follow-up, the MIS procedure tends to have better results in terms of patient-reported quality of life. MIS-TLIF offers perioperative advantages but may carry the risk of increased nerve root manipulation with consecutive higher radicular pain, which may be related to the learning curve of the procedure.

Biomechanical Evaluation of the Effect of Minimally Invasive Spine Surgery Compared with Traditional Approaches in Lifting Tasks

Fusion of spinal vertebrae can be accomplished by different surgical approaches. We investigated Traditional Open Spine Surgery (TOSS) versus Minimally Invasive Spine Surgery (MISS). While TOSS sacrifices spine muscles originating or inserting on the affected vertebrae, MISS seeks to minimize the approach-related morbidity and preserve the tendon attachments of the muscles in the area. We captured 3-D motions of the full body of one healthy subject performing a variety of 10 kg box lifting operations representing activities-of-daily-living that are likely to challenge the spine biomechanically. The motion data were transferred to a full-body biomechanical model with a detailed representation of the biomechanics of the spine, and simulations of the internal spine loads and muscle forces were performed under a baseline configuration and muscle configurations typical for TOSS respectively MISS for the cases of L3/L4, L4/L5, L5/S1, L4/S1 and L3/L5 fusions. The computational model was then used to investigate the biomechanical differences between surgeries. The simulations revealed that joint reaction forces are more affected by both surgical approaches for lateral lifting motions than for sagittal plane motions, and there are indications that individuals with fused joints, regardless of the approach, should be particularly careful with asymmetrical lifts. The MISS and TOSS approaches shift the average loads of different muscle groups in different ways. TOSS generally leads to higher post-operative muscle loads than MISS in the investigated cases, but the differences are smaller than could be expected, given the differences of surgical technique.

Comparison of adjacent segment disease after minimally invasive versus open lumbar fusion: a minimum 10-year follow-up

OBJECTIVE

The object of this study was to compare, after a long-term follow-up, the incidence and features of adjacent segment disease (ASDis) following lumbar fusion surgery performed via an open technique using conventional interbody fusion plus transpedicular screw fixation or a minimally invasive surgery (MIS) using a tubular retractor together with percutaneous pedicle screw fixation.

METHODS

The authors conducted a retrospective chart review of patients with a follow-up period > 10 years who had undergone instrumented lumbar fusion at the L4-5 level between January 2004 and December 2010. The patients were divided into an open surgery group and MIS group based on the surgical method performed. Baseline characteristics and radiological findings, including factors related to ASDis, were compared between the two groups. Additionally, the incidence of ASDis and related details, including diagnosis, time to diagnosis, and treatment, were analyzed.

RESULTS

Among 119 patients who had undergone lumbar fusion at the L4-5 level in the study period, 32 were excluded according to the exclusion criteria. The remaining 87 patients were included as the final study cohort and were divided into an open group (n = 44) and MIS group (n = 43). The mean follow-up period was 10.50 (range 10.0-14.0) years in the open group and 10.16 (range 10.0-13.0) years in the MIS group. The overall facet joint violation rate was significantly higher in the open group than in the MIS group (54.5% vs 30.2%, p = 0.022). However, in terms of adjacent segment degeneration, there were no significant differences in corrected disc height, segmental angle, range of motion, or degree of listhesis of the adjacent segments between the two groups during follow-up. The overall incidence of ASDis was 33.3%, with incidences of 31.8% in the open group and 34.9% in the MIS group, showing no significant difference between the two groups (p = 0.822). Additionally, detailed diagnosis and treatment factors were not different between the two groups.

CONCLUSIONS

After a minimum 10-year follow-up, the incidence of ASDis did not differ significantly between patients who had undergone open fusion and those who had undergone MIS fusion at the L4-5 level.

Oblique Lateral Interbody Fusion versus Transforaminal Lumbar Interbody Fusion in Degenerative Lumbar Spondylolisthesis: A Single-Center Retrospective Comparative Study

Objective

To compare the efficacy of oblique lateral interbody fusion (OLIF) and transforaminal lumbar interbody fusion (TLIF) in single-level degenerative lumbar spondylolisthesis (DLS).

Methods

A retrospective analysis of patients who underwent single-level DLS surgery in our department from 2015 to 2018 was performed. According to the surgical method, the enrolled patients were divided into two groups, namely, the OLIF group who underwent OLIF combined with percutaneous pedicle screw fixation (PPSF) and the TLIF group. Clinical outcomes included operation time, operation blood loss, postoperative drainage, hospital stay, visual analog scale (VAS) score, Oswestry disability index (ODI), and complications, and imaging outcomes included upper vertebral slip, intervertebral space height (ISH), intervertebral foramen height (IFH), intervertebral space angle (ISA), lumbar lordosis (LL), and bone fusion rate. All outcomes were recorded and analyzed.

Results

A total of 65 patients were finally included, and there were 28 patients and 37 patients in the OLIF group and the TLIF group, respectively. The OLIF group showed shorter operation time, less blood loss, less postoperative drainage, and shorter hospital stay than the TLIF group (P < 0.05). The ISH, IFH, ISA, and LL were all larger in the OLIF group at postoperative and last follow-up (P < 0.05), but the degree of upper vertebral slip was found no difference between the two groups (P > 0.05). The bone graft fusion rate of OLIF group and TLIF group at 3 months, 6 months, and last follow-up was 78.57%, 92.86%, and 100% and 70.27%, 86.49%, and 97.30%, respectively, and no significant differences were found (P > 0.05). Compared with the TLIF group, the OLIF group showed a superior improvement in VAS and ODI at 1 month, 3 months, and 6 months postoperative (P < 0.05), but no differences were found at 12 months postoperative and the last follow-up (P > 0.05). There was no significant difference in complications between the two groups, with 4 patients and 6 patients in the OLIF group and TLIF group, respectively (P > 0.05).

Conclusions

Compared with TLIF, OLIF showed the advantages of less surgical invasion, better decompression effect, and faster postoperative recovery in single-level DLS surgery.

Preliminary investigation of spinal level and postural effects on thoracic muscle morphology with upright open MRI

OBJECTIVE

Spinal-muscle morphological differences between weight-bearing and supine postures have potential diagnostic, prognostic, and therapeutic applications. While the focus to date has been on cervical and lumbar regions, recent findings have associated spinal deformity with smaller paraspinal musculature in the thoracic region. We aim to quantitatively investigate the morphology of trapezius (TZ), erector spinae (ES) and transversospinalis (TS) muscles in upright postures with open upright MRI and also determine the effect of level and posture on the morphological measures.

METHODS

Six healthy volunteers (age 26 ± 6 years) were imaged (0.5 T MROpen, Paramed, Genoa, Italy) in four postures (supine, standing, standing with 30° flexion, and sitting). Two regions of the thorax, middle (T4-T5), and lower (T8-T9), were scanned separately for each posture. 2D muscle parameters such as cross-sectional area (CSA) and position (radius and angle) with respect to the vertebral body centroid were measured for the three muscles. Effect of spinal level and posture on muscle parameters was examined using 2-way repeated measures ANOVA separately for T4-T5 and T8-T9 regions.

RESULTS

The TZ CSA was smaller (40%, P = .0027) at T9 than at T8. The ES CSA was larger at T5 than at T4 (12%, P = .0048) and at T9 than at T8 (10%, P = .0018). TS CSA showed opposite trends at the two spinal regions with it being smaller (16%, P = .0047) at T5 than at T4 and larger (11%, P = .0009) at T9 than at T8. At T4-T5, the TZ CSA increased (up to 23%), and the ES and TS CSA decreased (up to 10%) in upright postures compared to supine.

CONCLUSION

Geometrical parameters that describe muscle morphology in the thorax change with level and posture. The increase in TZ CSA in upright postures could result from greater activation while upright. The decrease in ES CSA in flexed positions likely represents passive stretching compared to neutral posture.

Quantifying Dysfunction of the Lumbar Multifidus Muscle After Radiofrequency Neurotomy and Fusion Surgery: A Preliminary Study

The multifidus is an important muscle for the active stabilization of the spine. Unfortunately, clinical procedures such as posterior lumbar fusion (PLF) and radio frequency neurotomy (RFN) cause injury to these muscles affecting their function. However, evaluating multifidus function using traditional biomechanical methods is challenging due to its unique anatomical features. The change in muscle shear modulus during contraction has been corrected to force generation for several skeletal muscles. Therefore, the change in shear modulus can be used to quantify muscle contraction. The objective of this study was to evaluate multifidus dysfunction by comparing changes in shear modulus during muscle contraction in healthy individuals and patients who received RFN and PLF in the lumbar spine. We used our recently developed protocol which consists of measuring changes of multifidus shear modulus at lying prone, sitting up, and sitting up with the arms lifted. In healthy individuals, the median multifidus shear modulus increased progressively from prone, sitting, and sitting with arms raised: 18.55 kPa, 27.14 kPa, and 38.45 kPa, respectively. A moderate increase in shear modulus for these body positions was observed in PLF patients: 9.81 kPa, 17.26 kPa, and 21.85 kPa. In RFN patients, the shear modulus remained relatively constant: 14.44 kPa, 16.57 kPa, and 17.26 kPa. Overall, RFN and PLF caused a reduction in the contraction of multifidus muscles. However, the contraction of multifidus muscle slightly increased during multifidus activation in PLF patients, while it did not change in RFN patients. These preliminary measurements suggest that the proposed protocol using SWE can provide important information about the function of individual spine muscles to guide the design and evaluation of postsurgical rehabilitation protocols.

Comparison of paraspinal muscle degeneration and decompression effect between conventional open and minimal invasive approaches for posterior lumbar spine surgery

Laminotomy and transforaminal lumbar interbody fusion (TLIF) is usually used to treat unstable spinal stenosis. Minimally invasive surgery (MIS) can cause less muscle injury than conventional open surgery (COS). The purpose of this study was to compare the degree of postoperative fatty degeneration in the paraspinal muscles and the spinal decompression between COS and MIS based on MRI. Forty-six patients received laminotomy and TLIF (21 COS, 25 MIS) from February 2016 to January 2017 were included in this study. Lumbar MRI was performed within 3 months before surgery and 1 year after surgery to compare muscle-fat-index (MFI) change of the paraspinal muscles and the dural sac cross-sectional area (DSCAS) change. The average MFI change at L2–S1 erector spinae muscle was significantly greater in the COS group (27.37 ± 21.37% vs. 14.13 ± 19.19%, P = 0.044). A significant MFI change difference between the COS and MIS group was also found in the erector spinae muscle at the caudal adjacent level (54.47 ± 37.95% vs. 23.60 ± 31.59%, P = 0.016). DSCSA improvement was significantly greater in the COS group (128.15 ± 39.83 mm² vs. 78.15 ± 38.5 mm², P = 0.0005). COS is associated with more prominent fatty degeneration of the paraspinal muscles. Statically significant post-operative MFI change was only noted in erector spinae muscle at caudal adjacent level and L2–S1 mean global level. COS produces a greater area of decompression on follow up MRI than MIS with no statistical significance on clinical grounds.

Does minimally invasive spine surgery reduce the rate of perioperative medical complications? A retrospective single-center experience of 1435 degenerative lumbar spine surgeries

PURPOSE

It is unclear if minimally invasive techniques reduce the rate of perioperative complications when compared to traditional open approaches to the lumbar spine. Our aim was to evaluate perioperative complications in patients that underwent MIS and conventional open techniques for degenerative lumbar pathology.

METHODS

A retrospective review of a prospectively collected database identified 1435 patients that underwent surgery for degenerative lumbar pathology from January 2013-2016. We evaluated the rates of deep vein thrombosis, pulmonary embolism, urinary tract infection, and pneumonia. Groups were analyzed based on decompression alone as compared with decompression and fusion for both MIS and traditional open techniques.

RESULTS

Patients that underwent traditional open lumbar decompression surgery were more likely to develop a DVT (P = .01) than those undergoing MIS decompression. There was no significant difference in rates of PE (P = .99), UTI (P = .24), or pneumonia (P = .56). Patients that underwent traditional open lumbar fusion surgery compared to MIS fusion were also more likely to have a PE (P = .03). There was no significant difference in rates of DVT (P = .22), UTI (P = .43), or pneumonia (P = .24).

CONCLUSION

Minimally invasive spinal surgery was found to reduce the rate of DVT for decompression surgeries and reduce the rate of PE for fusion surgeries.

Reoperation, Readmission, and Discharge Disposition for Patients With Degenerative Lumbar Pathology Treated With Either Open or Minimally Invasive Techniques: A Single-Center Retrospective Review of 1435 Cases

BACKGROUND

Spine surgery has been transformed by the growth of minimally invasive surgery (MIS) procedures. Previous studies agree that MIS has shorter hospitalization and faster recovery time when compared to conventional open surgery. However, the reoperation and readmission rates between the 2 techniques have yet to be well characterized.

OBJECTIVE

To evaluate the rate of subsequent revision between MIS and open techniques for degenerative lumbar pathology.

METHODS

A total of 1435 adult patients who underwent lumbar spine surgery between 2013 and 2016 were included in this retrospective analysis. The rates of need for subsequent reoperation, 30- and 90-d readmission, and discharge to rehabilitation were recorded for both MIS and traditional open techniques. Groups were divided into decompression alone and decompression with fusion.

RESULTS

The rates of subsequent reoperation following MIS and open surgery were 10.4% and 12.2%, respectively (P = .32), which were maintained when subdivided into decompression and decompression with fusion. MIS and open 30-d readmission rates were 7.9% and 7.2% (P = .67), while 90-d readmission rates were 4.3% and 3.6% (P = .57), respectively. Discharge to rehabilitation was significantly lower for patients under 60 yr of age undergoing MIS (1.64% vs 5.63%, P = .04).

CONCLUSION

The use of minimally invasive techniques for the treatment of lumbar spine pathology does not result in increased reoperation or 30- and 90-d readmission rates when compared to open approaches. Patients under the age of 60 yr undergoing MIS procedures were less likely to be discharged to rehab.

The Impact of Cervical Spinal Muscle Degeneration on Cervical Sagittal Balance and Spinal Degenerative Disorders

STUDY DESIGN

This is a retrospective analysis of kinematic magnetic resonance images (kMRI).

OBJECTIVE

To assess the association of cervical paraspinal muscle with cervical sagittal balance and degenerative spinal disorders.

SUMMARY OF BACKGROUND DATA

Although the effects of spinal disorders and cervical imbalance on patient's symptoms have been well described, the relationship of the cervical muscle quality and volume to cervical imbalance or spinal disorders is not well established.

MATERIALS AND METHODS

In total, 100 kMRI taken in a neutral weight-bearing position were analyzed. The adjusted cross-sectional area ratio (aCSA ratio: the value of muscle CSA divided by the vertebral CSA) and fat infiltration ratio of the transversospinalis muscles at C4 and C7 vertebral levels were measured using axial slice of kMRI. The correlation with cervical balance parameters [Oc-C2 angle, C2-C7 angle, C7-T1 angle, C7 slope, T1 slope, cranial tilt, cervical tilt, thoracic inlet angle (TIA), and neck tilt] and cervical degenerative disorders (disk degeneration, Modic change, and spondylolisthesis) were evaluated.

RESULTS

The aCSA ratio at C4 correlated with C2-C7 angle (r=0.267), C7 slope (r=0.207), T1 slope (r=0.221), disk degeneration at C3-4, C4-5, C5-6 (r=-0.234, -0.313, -0.262) and spondylolisthesis at C3 (anterior: r=-0.206, posterior: r=-0.249). The aCSA ratio at C7 correlated with disk degeneration at C3-4, C4-5, C5-6, C6-7 (r=-0.209, -0.294, -0.239, -0.209). The fat infiltration ratio at C4 correlated with TIA (r=0.306) and neck tilt (r=0.353), likewise the ratio at C7 correlated with TIA (r=0.270) and neck tilt (r=0.405). All correlations above were statistically significant with P<0.05.

CONCLUSIONS

The paraspinal muscle volume showed significant relationship with the cervical balance parameters and disk degeneration. While, paraspinal muscle quality related to the thoracic inlet parameters. Our findings can be an important step to develop the knowledge of the association between cervical muscle and cervical degenerative disorders, as well as the sagittal balance of the cervical spine.

LEVEL OF EVIDENCE

Level III.

Paraspinal muscle atrophy after posterior lumbar surgery with and without pedicle screw fixation with the classic technique

OBJECTIVES

Lumbar spine surgery causes a muscular injury during its approach that could worsen long-term postoperative functional results. This study aims to analyze the postoperative paraspinal atrophy associated with two types of intervention.

MATERIAL AND METHODS

Clinical records and lumbar magnetic resonance imaging were collected from a group of 41 patients, 20 underwent laminectomy with lumbar fixation due to lumbar spinal stenosis (fixation group) and another group of 21 underwent hemilaminectomy without fixation due to lumbar disc disease (non-fixation group). In which muscle atrophy was analyzed quantitatively.

RESULTS

We found a negative correlation between age and preoperative muscle, which was higher in those who underwent lumbar fixation (rho = -0.64 p = .002). We also found a positive correlation between preoperative muscle and postoperative atrophy (rho = 0.32 p = .041). In the age, sex and fixation adjusted multivariate linear regression model (R² = 0.31), laminectomy with fixation is attributed to 5.3% atrophy (IC95 1.4-9.5%, p = .017); preoperative musculature > 70% is attributed to atrophy of 13.8% (95% CI 5.5%-22%, p = .002). Age did not correlate with postoperative atrophy.

CONCLUSIONS

Paraspinal muscle atrophy after lumbar spinal surgery is greater if an extensive approach is performed such as complete laminectomy with bilateral facetectomy and transpedicular fixation. A greater previous musculature regardless of age, sex and type of surgery also predicts greater postoperative atrophy.

Split laminotomy versus conventional laminotomy: postoperative outcomes in pediatric patients

OBJECTIVE Split laminotomy is a technique for accessing the spinal canal from the posterior midline that minimizes muscle dissection and bone removal. Benefits of this approach in minimizing postoperative pain and muscle atrophy in the adult population have been reported, but pediatric data are limited. Herein, the authors evaluate the benefits of the split laminotomy technique in pediatric patients. METHODS Data obtained in patients who underwent posterior spine surgery at Children's Hospital of Wisconsin for an intradural midline pathology between April 2008 and June 2015 were reviewed retrospectively. Each patient was assigned to one of two groups, the split-laminotomy or conventional-laminotomy group. The primary outcomes assessed were mean daily pain score, total opioid use over a period of 72 hours after surgery, and the degree of paraspinal muscle atrophy and fat infiltration found on short-term (1-4 months) and long-term (1-4 years) follow-up spine MRI studies. RESULTS A total of 117 patients underwent lumbar-level surgery (83 conventional laminotomy, 34 split laminotomy), and 8 patients underwent thoracic-level surgery (4 in each group). No significant difference in the mean daily pain scores between groups was found. The daily opioid use was significantly lower in the split-laminotomy group on postoperative day 0 (POD0) and POD1 but not on POD2 (p = 0.01, 0.01, and 0.10, respectively). The total opioid use over the 72-hour postoperative period was significantly lower in the split-laminotomy group (p = 0.0008). The fat/muscle ratio was significantly higher in both the short-term and long-term follow-up periods in the conventional-laminotomy group (p = 0.01 and 0.0002, respectively). The rate of change of paraspinal muscle fat infiltration was significantly lower in the split-laminotomy group than in the conventional-laminotomy group (p = 0.007). The incidence of complications was not significantly different between groups (p = 0.08). CONCLUSIONS This study was of the largest series reported thus far of pediatric patients who underwent split laminotomy and the only controlled study that has involved children. The authors' results reinforce the short-term benefit of split laminotomy in minimizing acute postoperative pain and long-term benefits of decreasing muscle atrophy and fatty degeneration, which are known to be associated with the development of chronic pain and spinal instability. Additional efforts for assessing long-term effects in the development of chronic pain, spinal instability, and spinal deformity are still necessary.

Limitations in clinical outcome after posterior stabilization of thoracolumbar fractures do not correlate with dynamic trunk muscle dysfunction: an ultrasound controlled prospective cohort study

BACKGROUND AND PURPOSE

Posterior stabilization of the spine is associated with iatrogenic muscle damage. This is discussed to represent an important cause of postoperative pain, especially in open reduction and fixation. The aim of this study was to visualize muscular changes after open or percutaneous posterior stabilization of traumatic thoracolumbar spine fractures and to investigate whether or not these changes are related to the clinical outcome.

METHODS

This prospective cohort study was performed between 05/2012 and 10/2014. A group of posteriorly stabilized patients (study group; SG) with traumatic fractures (AOSpine Type A3 or A4) of the thoracolumbar junction (T11-L2) without neurological deficit were matched to a healthy control group (CG) by age, gender and body mass index.

FOLLOW-UP

12 months after surgery.

PARAMETERS

muscle size, voluntary muscular activation (VMA) using a standardized ultrasound protocol and standardized questionnaires (VAS Spine Score; ODI; SF-36) were analyzed.

STATISTICS

SPSS (Version 20, 76 Chicago, IL, USA). T test, Chi squared test, analysis of variance and a correlation analysis were performed. Significance level was at p < 0.05.

RESULTS

Twenty-five patients (SG) and 23 control individuals (CG) were included. At follow-up, voluntary muscular activation of the lumbar multifidus (LM) as well as the transverse abdominis muscle (TrA) was diminished in all patients compared to the control group (VMA LM at level L3/4: SG 3.2%; CG 5.1%; p < 0.05; VMA TrA: SG 33.43%; CG 37.84%; p < 0.05). Concomitant interviews revealed health restrictions in all patients when compared with the control group. A correlation between muscle function and clinical outcome could not been demonstrated (rs > 0.07; NS).

CONCLUSION

In surgically treated A3 and A4 fractures, there is continuous muscular deficit 1 year after surgery as documented by ultrasound and clinical control. But, by means of our study we conclude that those muscular deficits alone seem not to be decisive for the clinical outcome 1 year after surgery.

Assessment of Paraspinal Muscle Atrophy Percentage after Minimally Invasive Transforaminal Lumbar Interbody Fusion and Unilateral Instrumentation Using a Novel Contralateral Intact Muscle-Controlled Model

Study Design

Retrospective comparative clinical study.

Purpose

This study aimed to assess paraspinal muscle atrophy in patients who underwent minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) and unilateral pedicle screw fixation using a novel contralateral intact muscle-controlled model.

Overview of Literature

The increased incidence of paravertebral lumbar muscle injuries after open techniques has raised the importance of implementing minimally invasive spine surgical techniques using tubular retractors and minimally invasive screw placement. The functional cross-sectional area (FCSA) represents the lean muscle mass; furthermore, FCSA is a useful marker of the contractile ability of a muscle following a spine surgery. However, the benefits of unilateral fixation and MI-TLIF on paraspinal muscles have not been defined.

Methods

We performed a retrospective imagenological review on eleven patients who underwent unilateral MI-TLIF and unilateral transpedicular screw lumbar placement. FCSAs of the multifidus and erector spinae were measured 1 year after surgery at adjacent levels and were compared to the contralateral intact muscles. Measurement differences between the surgical and nonsurgical sites were compared. The interobserver reliability was calculated using an intraclass correlation coefficient.

Results

The mean FCSA at the surgical site was 20.97±5.07 cm² at the superior level and 8.89±2.87 cm² at the inferior level. The mean FCSA at the contralateral nonsurgical site was 20.15±5.95 cm² at the superior level and 9.20±2.66 cm² at the inferior level was. The superior and inferior FCSA measurements showed no significant difference between the surgical and nonsurgical sites (p=0.5, p=0.922, respectively).

Conclusions

Using a mini-open tubular approach through the sulcus between the longissimus and iliocostalis, MI-TLIF and unilateral pedicle screw instrumentation produced minimal paraspinal muscle damage at the superior and inferior adjacent levels.

Open versus percutaneous instrumentation in thoracolumbar fractures: magnetic resonance imaging comparison of paravertebral muscles after implant removal

OBJECTIVE

Percutaneous instrumentation in thoracolumbar fractures is intended to decrease paravertebral muscle damage by avoiding dissection. The aim of this study was to compare muscles at instrumented levels in patients who were treated by open or percutaneous surgery.

METHODS

Twenty-seven patients underwent open instrumentation, and 65 were treated percutaneously. A standardized MRI protocol using axial T1-weighted sequences was performed at a minimum 1-year follow-up after implant removal. Two independent observers measured cross-sectional areas (CSAs, in cm2) and region of interest (ROI) signal intensity (in pixels) of paravertebral muscles by using OsiriX at the fracture level, and at cranial and caudal instrumented pedicle levels. An interobserver comparison was made using the Bland-Altman method. Reference ROI muscle was assessed in the psoas and ROI fat subcutaneously. The ratio ROI-CSA/ROI-fat was compared for patients treated with open versus percutaneous procedures by using a linear mixed model. A linear regression analyzed additional factors: age, sex, body mass index (BMI), Pfirrmann grade of adjacent discs, and duration of instrumentation in situ.

RESULTS

The interobserver agreement was good for all CSAs. The average CSA for the entire spine was 15.7 cm2 in the open surgery group and 18.5 cm2 in the percutaneous group (p = 0.0234). The average ROI-fat and ROI-muscle signal intensities were comparable: 497.1 versus 483.9 pixels for ROI-fat and 120.4 versus 111.7 pixels for ROI-muscle in open versus percutaneous groups. The ROI-CSA varied between 154 and 226 for open, and between 154 and 195 for percutaneous procedures, depending on instrumented levels. A significant difference of the ROI-CSA/ROI-fat ratio (0.4 vs 0.3) was present at fracture levels T12–L1 (p = 0.0329) and at adjacent cranial (p = 0.0139) and caudal (p = 0.0100) instrumented levels. Differences were not significant at thoracic levels. When adjusting based on age, BMI, and Pfirrmann grade, a significant difference between open and percutaneous procedures regarding the ROI-CSA/ROI-fat ratio was present in the lumbar spine (p < 0.01). Sex and duration of instrumentation had no significant influence.

CONCLUSIONS

Percutaneous instrumentation decreased muscle atrophy compared with open surgery. The MRI signal differences for T-12 and L-1 fractures indicated less fat infiltration within CSAs in patients who received percutaneous treatment. Differences were not evidenced at thoracic levels, where CSAs were smaller. Fat infiltration was not significantly different at lumbar levels with either procedure in elderly patients with associated discopathy and higher BMI. In younger patients, there was less fat infiltration of lumbar paravertebral muscles with percutaneous procedures.

Does stabilization of the degenerative lumbar spine itself produce multifidus atrophy?

The effect of stabilization of the degenerative segment on changes in the pattern of paraspinal muscle activity was investigated using a previously developed musculoskeletal model. Muscle activity change depending on L4-L5 segment stabilization with and without taking into account the presence of multifidus atrophy according to direct invasion of the back muscle during surgery (MADIBM) was analysed in erect standing and 20° flexed postures. For the stabilization of the degenerative segment, a fusion or non-fusion stabilization with a pedicle-based dynamic stabilization system (PBDS) was applied. During erect standing, fusion generated a 12% reduction in the total multifidus muscle force, while its reduction was 6.6% with PBDS application. The presence of MADIBM produced 23.0% and 22.5% reductions in fusion and with PBDS application, respectively. During 20° flexion, 10.5% and 9.3% reductions were produced for fusion and PBDS application, respectively, and the corresponding values were 23.4% and 23.0%, respectively, in the presence of MADIBM. Increased facet joint contact forces were produced at the non-stabilized levels after stabilization while in erect standing posture. Alterations in muscle activity, which could be regarded as adaptions to altered spinal stability, may generate unexpected secondary problems in the spine.

Correlation between intervertebral disc degeneration, paraspinal muscle atrophy, and lumbar facet joints degeneration in patients with lumbar disc herniation

Background

To assess the correlation between lumbar disc degeneration (LDD), multifidus muscle atrophy (LMA), and facet joints degeneration in patients with L4-L5 lumbar disc herniation (LDH).

Methods

Sixty patients with L4-L5 LDH diagnosed by a 1.5 T MRI scanner were enrolled in the study group and another 60 patients with non-specific back pain were enrolled in the control group. LDD, LMA, and facet joints degeneration were examined and analyzed independently by two independent orthopedic surgeons using T2-weighted images. Wilcoxon test was used for analyzing the difference of LDD and facet joints degeneration between L3-L4 and L5-S1 and difference of LMA between the herniated and control groups. Correlation analysis of the three degeneration grades at the same level was determined by Spearman rank correlation test.

Results

In the herniated group, most LMA at L3-L4 level was grade 1 (42, 70.0%); grade 2 (33, 55.0%) at L4-L5 level; and grade 3 (27, 45.0%) at L5-S1 level. LMA and LDD grading were significantly different between L3-L4 and L5-S1 levels (P < 0.05). In the herniation group, the Spearman value for LDD and LMA grading were 0.352 (P < 0.01) at L3-L4 and 0.036 (P > 0.05) at the L5-S1 level. The differences in LMA between the herniated and control groups at the three levels were significant (P < 0.05).

Conclusions

Disc degeneration and multifidus muscles atrophy were positively correlated at the L3-L4 disc level. A lumbar extension muscle strengthening program could be helpful in preventing muscle atrophy and lumbar spinal degeneration.

Minimally invasive TLIF leads to increased muscle sparing of the multifidus muscle but not the longissimus muscle compared with conventional PLIF-a prospective randomized clinical trial

BACKGROUND CONTEXT

An overload of the paravertebral muscles after surgical intervention is suggested to be the major cause of postoperative pain. In cross-sectional area analyses, increased atrophy of the multifidus muscle (MF) after conventional open versus minimally invasive posterior lumbar interbody fusion (PLIF) has been described. The three-dimensional characteristics of the paravertebral muscles and separate evaluation of the longissimus muscle (LS) have not been addressed in analyses thus far.

PURPOSE

The purpose of the present study was to compare the MF and LS volume atrophy and fatty degeneration between single-level minimally invasive transforaminal lumbar interbody fusion (miTLIF) and conventional midline approach-based PLIF (coPLIF) of L4/L5 or L5/S1 at the index and superior adjacent segments.

DESIGN

This was a prospective, randomized, controlled, non-blinded study.

PATIENT SAMPLE

Fifty patients with single-level segment degeneration (Pfirrmann ≥III and Modic ≥3) of L4/L5 or L5/S1 not requiring decompression were randomly assigned to two groups.

OUTCOME MEASURES

Paraspinal lumbar residual muscle tissue volume, change in the relative fat content of MF and LS at the index and superior adjacent segments, and clinical parameters, including a visual analogue scale (VAS) for low back pain and the Oswestry Disability Questionnaire (ODI) were the outcome measures in this study.

METHODS

Twenty-five patients were treated with miTLIF, and the remaining patients were treated with coPLIF (both with transpedicular fixation). Clinical scoring was performed preoperatively and at 1 week and 12 months postoperatively, and computed tomography was performed at the latter two follow-ups.

RESULTS

The LS damage at the index segment was similar in both groups (3% greater fat content increase in the coPLIF vs. the miTLIF group, p=.032), whereas MF atrophy and degeneration were increased (p<.001) in the coPLIF group. At the adjacent segment, muscle atrophy and increased fatty infiltration (p<.05) were minimal in both muscles but were similar in both groups. Visual analogue scale and ODI scores improved (p<.001), without differences between the groups.

CONCLUSIONS

The muscle damage after miTLIF was inferior to that after coPLIF; spatially, however, the muscle sparing was predominantly attributed to the MF and, surprisingly, not to the LS.

Posterior Dynamic Stabilization With Direct Pars Repair via Wiltse Approach for the Treatment of Lumbar Spondylolysis: The Application of a Novel Surgery

STUDY DESIGN

A retrospective study to evaluate the clinical outcomes of a novel surgical method for treating patients with lumbar spondylolysis.

OBJECTIVE

The aim of this study was to investigate the effectiveness of posterior ISOBAR TTL stabilization of the lumbar spine with direct pars repair using Wiltse approach for the treatment of lumbar spondylolysis with or without slight spondylolisthesis and discuss the indications of this surgery.

SUMMARY OF BACKGROUND DATA

Surgical treatment of lumbar spondylolysis has yielded relatively good results. However, there are still many limitations of the current surgical methods, including, adjacent level degeneration, restricted indications, and soft tissue damage.

METHODS

Between August 2010 and January 2013, 13 (9 males and 4 females; mean age: 28.2 yrs), patients with lumbar spondylolysis with or without slight spondylolisthesis underwent posterior ISOBAR TTL stabilization of the lumbar spine, with direct pars repair via Wiltse approach. All patients were followed up for at least 24 months at outpatient visits or telephonically. Pre-operative and postoperative radiological assessments included anteroposterior, lateral and flexion extension radiographs, 3-dimensional reconstruction computed tomography (CT), and magnetic resonance imaging (MRI). Data pertaining to intraoperative blood loss, duration of operation, visual analog score (VAS), Oswestry disability index (ODI) scores, and other assessments were collected.

RESULTS

The median follow-up duration was 36 months (range, 24-53 months). Surgery was successful in all patients with no complications; bony fusion of pars was confirmed on CT scan at postoperative 2 years. Significant pain relief was achieved in all patients including those with discogenic pain, those >30 years of age, and those with severe disc degeneration (P < 0.01).

CONCLUSION

We evaluated a new surgical technique for the treatment of patients with spondylolysis with or without slight spondylolisthesis. Besides the good clinical results, the indications for this new surgery are much wider and can potentially overcome the limitations of earlier techniques.

LEVEL OF EVIDENCE

4.

Quantification of Multifidus Atrophy and Fatty Infiltration Following a Minimally Invasive Microdiscectomy

BACKGROUND

Multifidus muscle degeneration and atrophy have been demonstrated following traditional open spine surgery. The purpose of this study was to quantify multifidus muscle atrophy and fatty infiltration following a 1-level minimally invasive (MIS) lumbar discectomy.

METHODS

Magnetic resonance imaging (MRI) of 24 patients who underwent a primary 1-level MIS microdiscectomy were reviewed. Demographics, operative levels, and time from surgery to imaging were assessed. Total and lean cross-sectional areas (CSA), T1-signal intensity ratio between the multifidus and psoas muscles, and lean-to-total CSA ratio were measured. Pre- and postoperative values were compared within each patient utilizing paired sample T-tests.

RESULTS

The mean age was 47.8±14.2 years. MRI was obtained 182.5±194.4 days following index surgery. On the ipsilateral side, total CSA decreased at the index level (-4.9%) and the lean CSA decreased at the index (-6.2%), inferior pedicle (-13.0%), and inferior disc levels (-18.6%). On the contralateral side, no significant decreases in total or lean CSA were demonstrated. T1-signal intensity ratios increased at all levels, but the differences were not statistically significant. The lean-to-total CSA ratio was decreased at the superior disc (-5.2%), inferior pedicle (-8.4%), and inferior disc levels (-17.2%) on the ipsilateral side and at the contralateral inferior disc level (-5.3%).

CONCLUSIONS

Primary 1-level MIS discectomy results in minimal short-term atrophy and fatty infiltration of the multifidus at the index level. Total CSA atrophy was mainly confined to the ipsilateral side at the index level. Lean CSA atrophy was observed mainly at and below the index level on the ipsilateral side. Fatty infiltration, as measured by the lean-to-total CSA ratio, ranged 1.2-17.2% on the ipsilateral and 0-5.3% on the contralateral side with greater fat content demonstrated caudally to the surgical level.

CLINICAL RELEVANCE

Overall, the majority of the multifidus muscle appears to be radiographically preserved following an MIS lumbar discectomy.

Sarcopenia and neurosurgery

Aging process can be characterized as a spontaneous decrease of function in various organs with age. Muscle, as a big organ of human body, undergoes aging process presenting with loss of muscle mass, "sarcopenia". Recently, several working groups have tried to make consensus about sarcopenia for definition and diagnosis. Muscle mass is known to be closely related with bone, brain, fat, cardiovascular and metabolic systems. With increased understanding, clinical and basic researches about sarcopenia have been also increased rapidly from various areas of health science and technology. In this paper, the history and recent concepts of sarcopenia were reviewed and brief discussion of its prospect in the field of neurosurgery was done.

Minimally invasive one-level lumbar decompression and fusion surgery with posterior instrumentation using a combination of pedicle screw fixation and transpedicular facet screw construct

Background:

Minimally invasive lumbar spine fusion surgery has gained popularity in recent years. Routinely, this technique requires bilateral parasagittal incisions for decompression, interbody fusion, and posterior instrumentation. The following study is a description of a new minimally invasive technique for one-level transforaminal lumbar interbody fusion (TLIF) using a unilateral parasagittal incision (Wiltse approach), with placement of pedicle screws and then a percutaneous transpedicular facet screw insertion on the contralateral side. The biomechanical stability of this posterior construct will be discussed while the efficacy and complications of this technique have been examined.

Methods:

Forty patients underwent this new technique of one-level TLIF with posterior instrumentation using unilateral pedicle screw fixation supplemented with contralateral percutaneous transpedicular facet screw construct. Data regarding surgical time, estimated blood loss (EBL), hospital length of stay (LOS), and complications related to the posterior instrumentation are recorded.

Results:

The average surgical time of this new procedure was 124 minutes; average EBL was 140 cc; average hospital LOS was 3 days. Two patients developed new leg pain on the side where the facet screw had been placed. Both patients had the facet screw removed.

Conclusion:

This novel technique of unilateral pedicle screw fixation combined with contralateral percutaneous transpedicular facet screw construct has further reduced the amount of normal tissue injury while maintaining the same biomechanical advantages of bilateral pedicle screw fixation. However, caution is needed during the placement of the percutaneous facet screw in order to avoid nerve root injury.

Back muscle changes after pedicle based dynamic stabilization

OBJECTIVE

Many studies have investigated paraspinal muscle changes after posterior lumbar surgery, including lumbar fusion. However, no study has been performed to investigate back muscle changes after pedicle based dynamic stabilization in patients with degenerative lumbar spinal diseases. In this study, the authors compared back muscle cross sectional area (MCSA) changes after non-fusion pedicle based dynamic stabilization.

METHODS

Thirty-two consecutive patients who underwent non-fusion pedicle based dynamic stabilization (PDS) at the L4-L5 level between February 2005 and January 2008 were included in this retrospective study. In addition, 11 patients who underwent traditional lumbar fusion (LF) during the same period were enrolled for comparative purposes. Preoperative and postoperative MCSAs of the paraspinal (multifidus+longissimus), psoas, and multifidus muscles were measured using computed tomographic axial sections taken at the L4 lower vertebral body level, which best visualize the paraspinal and psoas muscles. Measurements were made preoperatively and at more than 6 months after surgery.

RESULTS

Overall, back muscles showed decreases in MCSAs in the PDS and LF groups, and the multifidus was most affected in both groups, but more so in the LF group. The PDS group showed better back muscle preservation than the LF group for all measured muscles. The multifidus MCSA was significantly more preserved when the PDS-paraspinal-Wiltse approach was used.

CONCLUSION

Pedicle based dynamic stabilization shows better preservation of paraspinal muscles than posterior lumbar fusion. Furthermore, the minimally invasive paraspinal Wiltse approach was found to preserve multifidus muscles better than the conventional posterior midline approach in PDS group.

Increased intramuscular fatty infiltration without differences in lumbar muscle cross-sectional area during remission of unilateral recurrent low back pain

Lumbar muscle degeneration is a common feature in non-specific low back pain (LBP). It is hypothesized that degenerated muscles might compromise spinal stability and lead to further injury/pain. However, little is known about lumbar muscle morphometry after resolution of LBP. Therefore, this study investigated the extent of lumbar muscle atrophy and fatty infiltration in individuals who are at risk for a recurrence of LBP. Thirteen participants in remission of unilateral recurrent LBP were compared to 13 healthy controls, comparable for age, weight, length and level of physical activity. Total, lean muscle and fat cross-sectional area (CSA) of lumbar multifidus (MF), erector spinae (ES) and psoas (PS) were investigated on T1-weighted Magnetic Resonance Imaging (MRI), bilaterally and at 3 lumbar levels (L3 upper, L4 upper and L4 lower endplate). In addition, a muscle-fat-index (MFI) was calculated reflecting the amount of fatty infiltration in lean muscle tissue. No significant differences for total, lean muscle and fat CSA were found between people in remission of recurrent LBP and the control group. Conversely, MFI was increased bilaterally at the 2 lowest lumbar levels. There were no differences between the previously painful and non-painful side of the LBP group for any of the parameters. These results show a generalized increase in intramuscular fatty infiltration in lean muscle tissue in the absence of macroscopical signs of muscle degeneration after resolution of LBP. These findings reflect a decreased muscle quality, but not quantity, and might indicate a pathophysiological mechanism contributing to recurrence of LBP.

No difference in long-term trunk muscle strength, cross-sectional area, and density in patients with chronic low back pain 7 to 11 years after lumbar fusion versus cognitive intervention and exercises

BACKGROUND CONTEXT

Reduced muscle strength and density observed at 1 year after lumbar fusion may deteriorate more in the long term.

PURPOSE

To compare the long-term effect of lumbar fusion and cognitive intervention and exercises on muscle strength, cross-sectional area, density, and self-rated function in patients with chronic low back pain (CLBP) and disc degeneration.

STUDY DESIGN

Randomized controlled study with a follow-up examination at 8.5 years (range, 7-11 years).

PATIENTS AND METHODS

Patients with CLBP and disc degeneration randomized to either instrumented posterolateral fusion of one or both of the two lower lumbar levels or a 3-week cognitive intervention and exercise program were included. Isokinetic muscle strength was measured by a Cybex 6000 (Cybex-Lumex, Inc., Ronkonkoma, NY, USA). All patients had previous experience with the test procedure. The back extension (E) flexion (F) muscles were tested, and the E/F ratios were calculated. Cross-sectional area and density of the back muscles were measured at the L3-L4 segment by computed tomography. Patients rated their function by the General Function Score.

OUTCOME MEASURES

Trunk muscle strength, cross-sectional area, density, and self-rated function.

RESULTS

Fifty-five patients (90%) were included at long-term follow-up. There were no significant differences in cross-sectional area, density, muscle strength, or self-rated function between the two groups. The cognitive intervention and exercise group increased trunk muscle extension significantly (p<.05), and both groups performed significantly better on trunk muscle flexion tests (p<.01) at long-term follow-up. On average, self-rated function improved by 56%, cross-sectional area was reduced by 8.5%, and muscle density was reduced by 27%.

CONCLUSION

Although this study did not assess the morphology of muscles likely damaged by surgery, trunk muscle strength and cross-sectional area above the surgical levels are not different between those who had lumbar fusion or cognitive intervention and exercises at 7- to 11-year follow-up.