Biomechanical effects of a unilateral approach to minimally invasive lumbar decompression

The importance of the posterior osteoligamentous complex of the lumbar spine: dogma changing biomechanical insights

BACKGROUND

During full flexion of the spine, the paraspinal muscles are largely inactive. This suggests that passive structures like the posterior osteoligamentous complex (POLC), consisting of interspinous and supraspinous ligaments and the spinous processes, play a key role in spinal stability and protection of the spinal column. The POLC, however, is often resected or damaged during spinal decompression surgeries, whereas the biomechanical implications of this resection or damage are not yet fully understood.

METHODS

A stepwise reduction study was performed on three fresh frozen cadaveric torsi (aged 30-78 years) using a custom setup which only allows sagittal plane motion. After preloading and locking in full flexion, the posterior lumbar structures were gradually resected in the following order: Skin, fascia, musculature, facet joints, ligamentum flavum, posterior ligamentous complex, and posterior longitudinal ligaments. Load cells measured force increase on the fixation frame after each resection step.

RESULTS

The load increased sequentially with each resection, demonstrating load transfer from the passive structures onto the fixation frame. The POLC, including the supraspinous and interspinous ligaments at L2-L5, accounted for 69 - 74% of the measured passive load resistance in full flexion, representing the largest contribution. Facet joints with their capsules contributed 10-18%, while muscular contributions were negligible (< 2%).

CONCLUSION

The experiment indicates that the POLC is the primary passive stabilizer of the fully flexed lumbar spine. Surgical resection of this structure can redistribute loads and increase stresses on remaining spinal tissues, potentially leading to spinal instability, accelerated degeneration, and poor clinical long-term outcomes.

Experimental ex vivo characterization of the biomechanical effects of laminectomy and posterior fixation of the lumbo-sacral spine

Laminectomy and posterior fixation are well-established surgical techniques to decompress nervous structures in case of lumbar spinal stenosis. While laminectomy is suspected to increase the instability of the spine, posterior fixation is associated with some complications such as adjacent segment degeneration. This study aimed to investigate how laminectomy and posterior fixation alter the biomechanics of the lumbar spine in terms of range of motion (ROM) and strains on the intervertebral discs. Twelve L2-S1 cadaveric spines were mechanically tested in flexion, extension, and lateral bending in the intact condition, after two-level laminectomy and after L4-S1 posterior fixation. The ROM of the spine segment was measured in each spine condition, and each loading configuration. The strain distribution on the surface of all the intervertebral discs was measured with Digital Image Correlation. Laminectomy significantly increased the ROM in flexion (p = 0.028) and lateral bending (p = 0.035). Posterior fixation decreased the ROM in all the loading configurations. Laminectomy did not significantly modify the strain distribution in the discs. Posterior fixation significantly increased the principal tensile and compressive strains in the disc adjacent the fixation both in flexion and in lateral bending. These findings can elucidate one of the clinical causes of the adjacent segment degeneration onset.

Effect of two-level decompressive procedures on the biomechanics of the lumbo-sacral spine: an ex vivo study

Hemilaminectomy and laminectomy are decompressive procedures commonly used in case of lumbar spinal stenosis, which involve the removal of the posterior elements of the spine. These procedures may compromise the stability of the spine segment and create critical strains in the intervertebral discs. Thus, this study aimed to investigate if decompressive procedures could alter the biomechanics of the lumbar spine. The focus was on the changes in the range of motion and strain distribution of the discs after two-level hemilaminectomy and laminectomy. Twelve L2-S1 cadaver specimens were prepared and mechanically tested in flexion, extension and both left and right lateral bending, in the intact condition, after a two-level hemilaminectomy on L4 and L5 vertebrae, and a full laminectomy. The range of motion (ROM) of the entire segment was assessed in all the conditions and loading configurations. In addition, Digital Image Correlation was used to measure the strain distribution on the surface of each specimen during the mechanical tests, focusing on the disc between the two decompressed vertebrae and in the two adjacent discs. Hemilaminectomy did not significantly affect the ROM, nor the strain on the discs. Laminectomy significantly increased the ROM in flexion, compared to the intact state. Laminectomy significantly increased the tensile strains on both L3-L4 and L4-L5 disc (p = 0.028 and p = 0.014) in ipsilateral bending, and the compressive strains on L4-L5 intervertebral disc, in both ipsilateral and contralateral bending (p = 0.014 and p = 0.0066), with respect to the intact condition. In conclusion, this study found out that hemilaminectomy did not significantly impact the biomechanics of the lumbar spine. Conversely, after the full laminectomy, flexion significantly increased the range of motion and lateral bending was the most critical configuration for largest principal strain.

Comparative Biomechanical Stability of the Fixation of Different Miniplates in Restorative Laminoplasty after Laminectomy: A Finite Element Study

A novel H-shaped miniplate (HSM) was specifically designed for restorative laminoplasties to restore patients' posterior elements after laminectomies. A validated finite element (FE) model of L2/4 was utilized to create a laminectomy model, as well as three restorative laminoplasty models based on the fixation of different miniplates after a laminectomy (the RL-HSM model, the RL-LSM model, and the RL-THM model). The biomechanical effects of motion and displacement on a laminectomy and restorative laminoplasty with three different shapes for the fixation of miniplates were compared under the same mechanical conditions. This study aimed to validate the biomechanical stability, efficacy, and feasibility of a restorative laminoplasty with the fixation of miniplates post laminectomy. The laminectomy model demonstrated the greatest increase in motion and displacement, especially in axial rotation, followed by extension, flexion, and lateral bending. The restorative laminoplasty was exceptional in preserving the motion and displacement of surgical segments when compared to the intact state. This preservation was particularly evident in lateral bending and flexion/extension, with a slight maintenance efficacy observed in axial rotation. Compared to the laminectomy model, the restorative laminoplasties with the investigated miniplates demonstrated a motion-limiting effect for all directions and resulted in excellent stability levels under axial rotation and flexion/extension. The greatest reduction in motion and displacement was observed in the RL-HSM model, followed by the RL-LSM model and then the RL-THM model. When comparing the fixation of different miniplates in restorative laminoplasties, the HSMs were found to be superior to the LSMs and THMs in maintaining postoperative stability, particularly in axial rotation. The evidence suggests that a restorative laminoplasty with the fixation of miniplates is more effective than a conventional laminectomy due to the biomechanical effects of restoring posterior elements, which helps patients regain motion and limit load displacement responses in the spine after surgery, especially in axial rotation and flexion/extension. Additionally, our evaluation in this research study could benefit from further research and provide a methodological and modeling basis for the design and optimization of restorative laminoplasties.

Early Functional Outcomes in Low Back Pain Subjects with a Novel Interspinous Fusion Device: REFINE Study 6-Month Results

Purpose

Lumbar interlaminar decompression with interspinous fixation is an established safe and effective treatment for spinal stenosis. Early maintenance of improvements in pain intensity and function are critical for durability of symptom relief. The purpose of this study was to investigate the efficacy of minimally invasive treatments for low back pain during the early period after treatment and their utility in setting the course for longer term success.

Patients and Methods

This study utilized patient evaluations at 3- and 6-months following treatment and is part of an actively enrolling, institutional review board (IRB) approved, single-arm, multicenter, prospective, open-label 12-month study. Clinical efficacy was assessed primarily using the change from baseline in Oswestry Disability Index (ODI), Visual Analog Scale (VAS) of the back and leg pain during walking and standing, and Zurich Claudication Questionnaire (ZCQ), and secondarily using the Patient Global Impression of Change (PGIC) and Patient-Reported Outcomes Measurement Information System (PROMIS) 29 v2.1. The safety endpoints were the adverse events and reoperations or revisions at the index level(s).

Results

At 6-month post-op, 76%, 62%-64%, and 64% of patients demonstrated clinical meaningful, and statistically significant improvement in their pain as defined by ZCQ, VAS (back and leg), and ODI, respectively. In addition, 78% of patients noted improvement in PGIC. Two procedure-related adverse events were noted which fully resolved without surgical intervention.

Conclusion

This 6-month interim analysis at 42% enrollment of patients was conducted to determine prolonged safety and efficacy of the interspinous fusion device. Our analysis showed a sustained improvement in clinical efficacy, and safety endpoints, when compared to the 3-months evaluations, across both interventional pain and neurosurgery specialties.

Lumbar vertebropexy after unilateral total facetectomy

BACKGROUND CONTEXT

Posterior decompression with spinal instrumentation and fusion is associated with well-known complications. Alternatives that include decompression and restoration of native stability of the motion segment without fusion continue to be explored, however, an ideal solution has yet to be identified.

PURPOSE

The aim of this study was to test two different synthetic lumbar vertebral stabilization techniques that can be used after unilateral total facetectomy.

STUDY DESIGN

Biomechanical cadaveric study.

METHODS

Twelve spinal segments were biomechanically tested after unilateral total facetectomy and stabilized with a FiberTape cerclage. The cerclage was pulled through the superior and inferior spinous process (interspinous technique) or through the spinous process and around both laminae (spinolaminar technique). The specimens were tested after (1) unilateral total facetectomy, (2) interspinous vertebropexy and (3) spinolaminar vertebropexy. The segments were loaded in flexion-extension (FE), lateral shear (LS), lateral bending (LB), anterior shear (AS) and axial rotation (AR).

RESULTS

Unilateral facetectomy increased native ROM in FE by 10.6% (7.6%-12.6%), in LS by 25.8% (18.7%-28.4%), in LB 7.5% (4.6%-12.7%), in AS 39.4% (22.6%-49.2%), and in AR by 27.2% (15.8%-38.6%). Interspinous vertebropexy significantly reduced ROM after unilateral facetectomy: in FE by 73% (p=.001), in LS by 23% (p=.001), in LB by 13% (p=.003), in AS by 16% (p=.007), and in AR by 20% (p=.001). In FE and LS the ROM was lower than in the baseline/native condition. In AS and AR, the baseline ROM was not reached by 17% and 1%, respectively. Spinolaminar vertebropexy significantly reduced ROM after unilateral facetectomy: in FE by 74% (p=.001), in LS by 24% (p=.001), in LB by 13% (p=.003), in AS by 28% (p=.004), and in AR by 15 % (p=.001). Baseline ROM was not reached by 9% in AR.

CONCLUSION

Interspinous vertebropexy seems to sufficiently counteract destabilization after unilateral total facetectomy, and limits range of motion in flexion and extension while avoiding full segmental immobilization. Spinolaminar vertebropexy additionally restores native anteroposterior stability, allowing satisfactory control of shear forces after facetectomy.

CLINICAL SIGNIFICANCE

Lumbar vertebropexy seems promising to counteract the destabilizating effect of facetectomy by targeted stabilization.

Vertebropexy as a Ligamentous Stabilization for Degenerative Low-Grade Spondylolisthesis: A Report of 3 Cases

CASE

Three patients with low-grade spondylolisthesis were treated with vertebropexy, a new surgical technique that replaces rigid fusion with ligamentous stabilization. Clinical outcomes, functional radiographs, and magnetic resonance imaging were used to document the early clinical results of this biomechanically established and promising new surgical method.

CONCLUSION

Vertebropexy may be a valuable alternative to rigid fusion in the treatment of low-grade degenerative spondylolisthesis.

Interspinous and spinolaminar synthetic vertebropexy of the lumbar spine

PURPOSE

To develop and test synthetic vertebral stabilization techniques ("vertebropexy") that can be used after decompression surgery and furthermore to compare them with a standard dorsal fusion procedure.

METHODS

Twelve spinal segments (Th12/L1: 4, L2/3: 4, L4/5: 4) were tested in a stepwise surgical decompression and stabilization study. Stabilization was achieved with a FiberTape cerclage, which was pulled through the spinous process (interspinous technique) or through one spinous process and around both laminae (spinolaminar technique). The specimens were tested (1) in the native state, after (2) unilateral laminotomy, (3) interspinous vertebropexy and (4) spinolaminar vertebropexy. The segments were loaded in flexion-extension (FE), lateral shear (LS), lateral bending (LB), anterior shear (AS) and axial rotation (AR).

RESULTS

Interspinous fixation significantly reduced ROM in FE by 66% (p = 0.003), in LB by 7% (p = 0.006) and in AR by 9% (p = 0.02). Shear movements (LS and AS) were also reduced, although not significantly: in LS reduction by 24% (p = 0.07), in AS reduction by 3% (p = 0.21). Spinolaminar fixation significantly reduced ROM in FE by 68% (p = 0.003), in LS by 28% (p = 0.01), in LB by 10% (p = 0.003) and AR by 8% (p = 0.003). AS was also reduced, although not significantly: reduction by 18% (p = 0.06). Overall, the techniques were largely comparable. The spinolaminar technique differed from interspinous fixation only in that it had a greater effect on shear motion.

CONCLUSION

Synthetic vertebropexy is able to reduce lumbar segmental motion, especially in flexion-extension. The spinolaminar technique affects shear forces to a greater extent than the interspinous technique.

Instrumented Posterior Arthrodesis of the Lumbar Spine: Prospective Study Evaluating Fusion Outcomes in Patients Receiving an Interspinous Fixation Device for the Treatment of Degenerative Spine Diseases

Purpose

Prospective evaluation of radiographic fusion outcomes in patients receiving instrumented posterior arthrodesis of the lumbar spine using a minimally invasive interspinous fixation device.

Patients and Methods

All patients (n = 110) from a single US physician's practice who received instrumented posterior arthrodesis of the lumbar spine with a minimally invasive interspinous fixation device in the calendar year 2020 were invited to return for a follow-up CT scan to radiographically assess fusion. Forty-three patients, representing 69 total treated levels, consented to participate and received a lumbar CT scan at a mean of 459 days post-surgery (177 to 652). The interspinous/interlaminar fusion was assessed by 3 independent radiologists using a novel grading scale. Spinous process fractures were also assessed.

Results

92.8% of the assessed levels were considered fused. There were no intraoperative spinous process fractures. There were 4 spinous process fractures (5.8%) identified on CT imaging, all of which were asymptomatic and healed without subsequent intervention. There were no instances of device mechanical failure or device-related reoperation.

Conclusion

Instrumented posterior arthrodesis of the lumbar spine using a minimally invasive interspinous fixation device provides clinically meaningful fusion rates with no reoperations and a low risk of spinous process fracture or other device-related complications.

Interspinous-Interbody Fusion via a Strictly Lateral Surgical Approach: A Biomechanical Stabilization Comparison to Constructs Requiring Both Lateral and Posterior Approaches

Objective Lumbar fusion performed through lateral approaches is becoming more common. The interbody devices are generally supported by supplemental posterior fixation implanted through a posterior approach, potentially requiring a second incision and intraoperative repositioning of the patient. A minimally invasive lateral interspinous fixation device may eliminate the need for intraoperative repositioning and avoid disruption of the supraspinous ligament. The objective of this in vitrobiomechanical study was to investigate segmental multidirectional stability and maintenance of foraminal distraction of a lateral interspinous fixation device compared to commonly used pedicle screw and facet screw posterior fixation constructs when combined with lumbar interbody cages. Methods Six human cadaver lumbar spine specimens were subjected to nondestructive quasistatic loading in the following states: (1) intact; (2) interspinous fixation device alone and (3) with lateral interbody cage; (4) lateral lumbar interbody cage with bilateral pedicle screws; (5) lateral lumbar interbody cage with unilateral pedicle screws; and (6) lateral lumbar interbody cage with facet screws. Multidirectional pure bending in 1.5 Nm increments to 7.5 Nm, and 7.5 Nm flexion-extension bending with a 700 N compressive follower load were performed separately with optoelectronic segmental motion measurement. Relative angular motions of L2-L3, L3-L4, and L4-L5 functional spinal units were evaluated, and the mean instantaneous axis of rotation in the sagittal plane was calculated for the index level. Foraminal height was assessed during combined flexion-extension and compression loading for each test construct. Results All implant configurations significantly restricted flexion-extension motion compared with intact (p < 0.05). No significant differences were found in flexion-extension when comparing the different posterior implants combined with lateral lumbar interbody cages. All posterior fixation devices provided comparable neuroforaminal distraction and maintained distraction during flexion and extension. Conclusions When combinedwith lateral lumbar interbody cages, the minimally invasive lateral interspinous fixation device effectively stabilized the spine and maintained neuroforaminal distraction comparable to pedicle screw constructs or facet screws. These results suggest the lateral interspinous fixation device may provide a favorable alternative to other posterior systems that require patient repositioning during surgery and involve a greater disruption of native tissues.

Biomechanics after spinal decompression and posterior instrumentation

PURPOSE

The aim of this study was to elucidate segmental range of motion (ROM) before and after common decompression and fusion procedures on the lumbar spine.

METHODS

ROM of fourteen fresh-frozen human cadaver lumbar segments (L1/2: 4, L3/4: 5, L5/S1: 5) was evaluated in six loading directions: flexion/extension (FE), lateral bending (LB), lateral shear (LS), anterior shear (AS), axial rotation (AR), and axial compression/distraction (AC). ROM was tested with and without posterior instrumentation under the following conditions: 1) native 2) after unilateral laminotomy, 3) after midline decompression, and 4) after nucleotomy.

RESULTS

Median native ROM was FE 6.8°, LB 5.6°, and AR 1.7°, AS 1.8 mm, LS 1.4 mm, AC 0.3 mm. Unilateral laminotomy significantly increased ROM by 6% (FE), 3% (LB), 12% (AR), 11% (AS), and 8% (LS). Midline decompression significantly increased these numbers to 15%, 5%, 21%, 20%, and 19%, respectively. Nucleotomy further increased ROM in all directions, most substantially in AC of 153%. Pedicle screw fixation led to ROM decreases of 82% in FE, 72% in LB, 42% in AR, 31% in AS, and 17% in LS. In instrumented segments, decompression only irrelevantly affected ROM.

CONCLUSIONS

The amount of posterior decompression significantly impacts ROM of the lumbar spine. The here performed biomechanical study allows creation of a simplified rule of thumb: Increases in segmental ROM of approximately 10%, 20%, and 50% can be expected after unilateral laminotomy, midline decompression, and nucleotomy, respectively. Instrumentation decreases ROM by approximately 80% in bending moments and accompanied decompression procedures only minorly destabilize the instrumentation construct.

The effect of various options for decompression of degenerated lumbar spine motion segments on the range of motion: a biomechanical in vitro study

BACKGROUND

Lumbar spinal stenosis is a common disease in the aging population. Decompression surgery represents the treatment standard, however, a risk of segmental destabilization depending on the approach and extent of decompression is discussed. So far, biomechanical studies on techniques were mainly conducted on non-degenerated specimens. This biomechanical in vitro study aimed to investigate the increase in segmental range of motion (ROM) depending on the extent of decompression in degenerated segments.

METHODS

Ten fresh frozen lumbar specimens were embedded in polymethyl methacrylate (PMMA) and loaded in a spine tester with pure moments of ± 7.5 Nm. The specimens were tested in their intact state for lateral bending (LB), flexion/extension (FE) and axial rotation (AR). Subsequently, four different decompression techniques were performed: unilateral interlaminar decompression (DC1), unilateral with "over the top" decompression (DC2), bilateral interlaminar decompression (DC3) and laminectomy (DC4). The ROM of the index segment was reported as percent (%) of the native state.

RESULTS

Specimens were measured in their intact state prior to decompression. The mean ROM was defined as 100% (FE:6.3 ± 2.3°; LB:5.4 ± 2.8°; AR:3.0 ± 1.6°). Interventions showed a continuous ROM increase: FE (DC1: + 4% ± 4.3; DC2: + 4% ± 4.5; DC3: + 8% ± 8.3;DC4: + 20% ± 15.9), LB(DC1: + 4% ± 6.0; DC2: + 5% ± 7.3; DC3: + 8% ± 8.3; DC4: + 11% ± 9.9), AR (DC1: + 7% ± 6.0; DC2: + 9% ± 7.9; DC3: + 15% ± 11.5; DC4: + 19% ± 10.5). Significant increases in ROM for all motion directions (p < 0.05) were only obtained after complete laminectomy (DC4).

CONCLUSION

Unilateral and/or bilateral decompressive surgery resulted in a statistically insignificant ROM increase, whereas complete laminectomy showed statistically significant ROM increase. If this ROM increase also has an impact on the clinical outcome and how to identify segments at risk for secondary lumbar instability should be evaluated in further studies.

Influence of microsurgical decompression on segmental stability of the lumbar spine - One-year results in a prospective, consecutive case series using upright, kinetic-positional MRI

Background

Standard procedure in patients with lumbar spinal canal stenosis is decompression to relieve the neural structures. Clinical results generally show superiority compared to nonoperative therapy after an observation period of several years. However, there is still a question of postsurgical segmental stability and correlation to clinical findings. Therefore, the aim of this prospective study was to evaluate the clinical outcome in patients who underwent microsurgical decompression in lumbar spine and particularly to analyze intervertebral movement by use of upright, kinetic-positional magnetic resonance imaging (MRI) over a period of 12 months and then to correlate the clinical and imaging data with each other.

Methods

Complete clinical data of 24 consecutive participants with microsurgical decompression of the lumbar spine were obtained by questionnaires including visual analogue scale (VAS) for back and leg, Oswestry Disability Index (ODI), Roland-Morris Disability Questionnaire (RMDQ), Short-Form-36 (SF-36), walking distance and use of analgesics with assessment preoperatively and after 6 weeks and 12 months. At the same points of time all patients underwent upright, kinetic-positional MRI to measure intersegmental motion of the operated levels with determination of intervertebral angles and translation and to correlate the clinical and imaging data with each other.

Results

VAS for leg, ODI, RMDQ and physical component scale of SF-36 improved statistically significantly without statistically significant differences regarding intersegmental motion and horizontal displacement 6 weeks and 12 months after operation. Regression analysis did not find any linear dependencies between the clinical scores and imaging parameters.

Conclusions

In awareness of some limitations of the study, our results demonstrate no increase of intersegmental movement or even instability after microsurgical decompression of the lumbar spine over a follow-up period of 12 months, which is equivalent to preservation of intervertebral stability. Furthermore, the magnitude of intervertebral range of motion showed no correlation to the clinical score parameters at all three examination points of time.

Lumbar Foraminal Stenosis Classification That Guides Surgical Treatment

BACKGROUND

There are numerous radiological and anatomical studies on lumbar foramina in the literature, but there are no distinctive studies about the relationship between treatment and the type of foraminal stenosis. This study was conducted to better evaluate foraminal stenosis and to plan treatment accordingly.

METHODS

Foraminal stenosis was divided into 2 groups: stable and unstable stenosis. Both groups were also divided into 4 subgroups in relation to the cause and type of compression and based on the structure of the intervertebral disc. The visual analog scale for leg pain (VAS-LP) and Oswestry Disability Index (ODI) scores were investigated before and after surgery.

RESULTS

A total of 115 patients (59 women and 56 men) underwent surgery for lumbar foraminal stenosis. The mean patient age was 56.1 years (range 17-80 years). The mean follow-up was 29 months (range 24-39 months). There were 36 patients (32%) with stable foraminal stenosis and 79 patients (68%) with unstable foraminal stenosis. The majority of the patients were identified as having unstable type 1 foraminal stenosis (45 of 115). The VAS-LP and ODI scores for each group decreased gradually during the follow-up periods and showed significant decrease during the last follow-up (P < 0.001). Interobserver and intraobserver agreement in the classification of foraminal stenosis was found to be nearly perfect. No patients experienced postoperative radiculopathy complication. Only 2 patients experienced superficial operation site infection and 1 showed deep wound infection. The patient who had a deep wound infection needed to repeat surgery for the infection.

CONCLUSIONS

We introduced a novel classification system for lumbar foraminal stenosis. We aimed to guide appropriate treatment modality depending on the determined classification. This classification helps to determine the optimal treatment. In the light of our findings, the patients who were operated according to our classification experienced satisfactory clinical outcomes and low complication rates.

LEVEL OF EVIDENCE: 3

Decompression Using Minimally Invasive Surgery for Lumbar Spinal Stenosis Associated with Degenerative Spondylolisthesis: A Review

Lumbar spinal stenosis (LSS), which often occurs concurrently with degenerative spondylolisthesis (DS), is a common disease in the elderly population, affecting the quality of life of aged people significantly. Notwithstanding the frequently good effect of conservative therapy on LSS, a minority of the patients ultimately require surgery. Surgery for LSS aims to decompress the narrowed spinal canals with preservation of spinal stability. Traditional open surgery, either pure decompression or decompression with fusion, was considered effective for the treatment of LSS with or without DS. However, the long-term clinical outcomes of traditional open surgery are still unclear. Moreover, the disadvantages of conventional open surgery are extensive, examples including tissue injuries or secondary instability, with limited outcomes and significant reoperation rates. With the development and improvement of surgical tools, various minimally invasive spine surgery (MISS) methods, including indirect decompression techniques of interspinous process devices (IPDs) and direct decompression techniques such as microscopic spine surgery or endoscopic spine surgery (ESS), have been updated with enhancement. IPDs, such as Superion devices, were reported to behave with comparable physical function, disability, and symptoms outcomes to laminectomy decompression. As an emerging technique of MISS, ESS has beneficial hallmarks including minimal tissue injuries, reduced complication rates, and shortened recovery periods, thus gaining popularity in recent years. ESS can be classified in terms of endoscopic hallmarks and approaches. Predictably, with the continuous development and gradual maturity, MISS is expected to replace traditional open surgery widely in the surgical treatment of LSS associated with DS in the future.

Open versus minimally invasive decompression for low-grade spondylolisthesis: analysis from the Quality Outcomes Database

OBJECTIVE

Lumbar decompression without arthrodesis remains a potential treatment option for cases of low-grade spondylolisthesis (i.e., Meyerding grade I). Minimally invasive surgery (MIS) techniques have recently been increasingly used because of their touted benefits including lower operating time, blood loss, and length of stay. Herein, the authors analyzed patients enrolled in a national surgical registry and compared the baseline characteristics and postoperative clinical and patient-reported outcomes (PROs) between patients undergoing open versus MIS lumbar decompression.

METHODS

The authors queried the Quality Outcomes Database for patients with grade I lumbar degenerative spondylolisthesis undergoing a surgical intervention between July 2014 and June 2016. Among more than 200 participating sites, the 12 with the highest enrollment of patients into the lumbar spine module came together to initiate a focused project to assess the impact of fusion on PROs in patients undergoing surgery for grade I lumbar spondylolisthesis. For the current study, only patients in this cohort from the 12 highest-enrolling sites who underwent a decompression alone were evaluated and classified as open or MIS (tubular decompression). Outcomes of interest included PROs at 2 years; perioperative outcomes such as blood loss and complications; and postoperative outcomes such as length of stay, discharge disposition, and reoperations.

RESULTS

A total of 140 patients undergoing decompression were selected, of whom 71 (50.7%) underwent MIS and 69 (49.3%) underwent an open decompression. On univariate analysis, the authors observed no significant differences between the 2 groups in terms of PROs at 2-year follow-up, including back pain, leg pain, Oswestry Disability Index score, EQ-5D score, and patient satisfaction. On multivariable analysis, compared to MIS, open decompression was associated with higher satisfaction (OR 7.5, 95% CI 2.41-23.2, p = 0.0005). Patients undergoing MIS decompression had a significantly shorter length of stay compared to the open group (0.68 days [SD 1.18] vs 1.83 days [SD 1.618], p < 0.001).

CONCLUSIONS

In this multiinstitutional prospective study, the authors found comparable PROs as well as clinical outcomes at 2 years between groups of patients undergoing open or MIS decompression for low-grade spondylolisthesis.

Radiologic Efficacy and Patient Satisfaction after Minimally Invasive Unilateral Laminotomy and Bilateral Decompression in Patients with Lumbar Spinal Stenosis: A Retrospective Analysis

BACKGROUND AND STUDY AIMS

 Lumbar spinal stenosis (LSS) is the most common spinal disease in older adults. Although surgical modalities are recommended in patients who are unresponsive to conservative treatment, the most appropriate minimally invasive surgical procedure for patients with LSS remains controversial. Moreover, few previous studies have focused on patient-centered outcomes with radiologic correlation. In the present study, we aimed to investigate radiologic efficacy and patient satisfaction following bilateral decompression via unilateral laminotomy.

MATERIALS AND METHODS

 We performed a retrospective analysis of radiologic efficacy and patient satisfaction in a series of surgical patients treated at our institution. We classified patients into two groups based on the primary pathology (i.e., central or lateral recess stenosis). Medical records were analyzed retrospectively for radiologic outcomes and clinical parameters including pain and changes in quality of life. Data related to outcomes were collected at 2 weeks, 3 months, and 12 months after surgery in the outpatient clinic.

RESULTS

 Among the 122 patients enrolled in this study, 51 had central spinal stenosis; 71 had lateral recess stenosis. Radiologically, we observed significant improvements in the anteroposterior diameter and cross-sectional area of the dural sac (central stenosis) and the lateral width of the central canal and depth of the lateral recess (lateral recess stenosis). Two weeks and 12 months after the surgical procedure, we observed significant improvements in the extent of symptoms, patient satisfaction, and quality of life (including physical function).

CONCLUSION

 Our findings suggest that bilateral decompression via a unilateral approach shows improved radiologic outcomes, varying based on the type of stenosis. Furthermore, patient satisfaction significantly improved regardless of the type of disease.

[Minimally invasive decompression techniques for spinal cord stenosis]

BACKGROUND

Lumbar spinal canal stenosis is frequently found among elderly patients and significantly limits their quality of life. Non-surgical therapy is an initial treatment option; however, it does not eliminate the underlying pathology. Surgical decompression of the spinal canal has now become the treatment of choice.

OBJECTIVE

Minimalization of surgical approach strategies with maintaining sufficient decompression of the spinal canal and avoiding disadvantages of macrosurgical techniques, monolateral paravertebral approach with bilateral intraspinal decompression, specific surgical techniques.

MATERIALS AND METHODS

Minimally invasive decompression techniques using a microscope or an endoscope are presented and different surgical strategies depending on both the extent (mono-, bi-, and multisegmental) and the location of the stenosis (intraspinal central, lateral recess, foraminal) are described.

RESULTS

Minimally invasive microscopic or endoscopic decompression procedures enable sufficient widening of the spinal canal. Disadvantages of macrosurgical procedures (e. g., postoperative instability) can be avoided. The complication spectrum overlaps partially with that of macrosurgical interventions, albeit with significantly less marked severity. Subjective patient outcome is clearly improved.

CONCLUSIONS

Referring to modern minimally invasive decompression procedures, surgery of lumbar spinal canal stenosis represents a rational and logical treatment alternative, since causal treatment of the pathology is only possible with surgery.

Minimally Invasive Approaches for Surgical Treatment of Lumbar Spondylolisthesis

The unilateral laminotomy for bilateral decompression initially was described in the late 1990s and has evolved in conjunction with minimally invasive surgical instrumentation. This technique has been shown to significantly improve bilateral symptoms regardless of the side of approach. It also can be used for multilevel decompressions using the slalom technique with alternating lateralizing sites of access. The over-the-top technique involving a unilateral approach for bilateral decompression helps preserve the posterior tension band and can accomplish the operative goals with better clinical outcomes than traditional open approaches.

Minimally invasive spinal decompression for degenerative lumbar spondylolisthesis and stenosis maintains stability and may avoid the need for fusion

Aims

The aim of this study was to investigate the clinical and radiographic outcomes of microendoscopic laminotomy in patients with lumbar stenosis and concurrent degenerative spondylolisthesis (DS), and to determine the effect of this procedure on spinal stability.

Patients and Methods

A total of 304 consecutive patients with single-level lumbar DS with concomitant stenosis underwent microendoscopic laminotomy without fusion between January 2004 and December 2010. Patients were divided into two groups, those with and without advanced DS based on the degree of spondylolisthesis and dynamic instability. A total of 242 patients met the inclusion criteria. There were 101 men and 141 women. Their mean age was 68.1 years (46 to 85). Outcome was assessed using the Japanese Orthopaedic Association and Roland Morris Disability Questionnaire scores, a visual analogue score for pain and the Short Form Health-36 score. The radiographic outcome was assessed by measuring the slip and the disc height. The clinical and radiographic parameters were evaluated at a mean follow-up of 4.6 years (3 to 7.5).

Results

There were no significant differences in the preoperative measurements between the group and no significant differences between the clinical parameters at the final follow-up. The mean percentage slip was 17.1% preoperatively and 17.7% at the final follow-up (p = 0.35). Progressive instability was noted in 13 patients (8.2%) with DS and 6 patients (7.0%) with advanced DS, respectively (p = 0.81). There was radiological evidence of restabilization of the spine in 30 patients (35%) with preoperative instability. The success rate of microendoscopic laminotomy was good/excellent in 166 (69%), fair in 49 (20%) and poor in 27 patients (11%) in both groups.

Conclusion

Microendoscopic laminotomy is an effective form of surgical treatment for patients with DS and stenosis. Preservation of the stabilizing structures using this technique prevents postoperative instability. Cite this article: Bone Joint J 2018;100-B:499-506.

Lumbar Spinal Stenosis Associated With Degenerative Lumbar Spondylolisthesis: A Systematic Review and Meta-analysis of Secondary Fusion Rates Following Open vs Minimally Invasive Decompression

Background

Decompression without fusion is a treatment option in patients with lumbar spinal stenosis (LSS) associated with stable low-grade degenerative spondylolisthesis (DS). A minimally invasive unilateral laminotomy (MIL) for "over the top" decompression might be a less destabilizing alternative to traditional open laminectomy (OL).

Objective

To review secondary fusion rates after open vs minimally invasive decompression surgery.

Methods

We performed a literature search in Pubmed/MEDLINE using the keywords "lumbar spondylolisthesis" and "decompression surgery." All studies that separately reported the outcome of patients with LSS+DS that were treated by OL or MIL (transmuscular or subperiosteal route) were included in our systematic review and meta-analysis. The primary end point was secondary fusion rate. Secondary end points were total reoperation rate, postoperative progression of listhetic slip, and patient satisfaction.

Results

We identified 37 studies (19 with OL, 18 with MIL), with a total of 1156 patients, that were published between 1983 and 2015. The studies' evidence was mostly level 3 or 4. Secondary fusion rates were 12.8% after OL and 3.3% after MIL; the total reoperation rates were 16.3% after OL and 5.8% after MIL. In the OL cohort, 72% of the studies reported a slip progression compared to 0% in the MIL cohort, respectively. After OL, satisfactory outcome was 62.7% compared to 76% after MIL.

Conclusion

In patients with LSS and DS, minimally invasive decompression is associated with lower reoperation and fusion rates, less slip progression, and greater patient satisfaction than open surgery.

Biomechanical Evaluation of Lumbar Decompression Adjacent to Instrumented Segments

BACKGROUND

Multilevel lumbar stenosis, in which 1 level requires stabilization due to spondylolisthesis, is routinely treated with multilevel open laminectomy and fusion. We hypothesized that a minimally invasive (MI) decompression is biomechanically superior to open laminectomy and may allow decompression of the level adjacent the spondylolisthesis without additional fusion.

OBJECTIVE

To study the mechanical effect of various decompression procedures adjacent to instrumented segments in cadaver lumbar spines.

METHODS

Conditions tested were (1) L4-L5 instrumentation, (2) L3-L4 MI decompression, (3) addition of partial facetectomy at L3-L4, and (4) addition of laminectomy at L3-L4. Flexibility tests were performed for range of motion (ROM) analysis by applying nonconstraining, pure moment loading during flexion-extension, lateral bending, and axial rotation. Compression flexion tests were performed for motion distribution analysis.

RESULTS

After instrumentation, MI decompression increased flexion-extension ROM at L3-L4 by 13% (P = .03) and axial rotation by 23% (P = .003). Partial facetectomy further increased axial rotation by 15% (P = .03). After laminectomy, flexion-extension ROM further increased by 12% (P = .05), a 38% increase from baseline, and axial rotation by 17% (P = .02), a 58% increase from baseline. MI decompression yielded no significant increase in segmental contribution of motion at L3-L4, in contrast to partial facetectomy and laminectomy (<.05).

CONCLUSION

MI tubular decompression is biomechanically superior to open laminectomy adjacent to instrumented segments. These results lend support to the concept that in patients in whom a multilevel MI decompression is performed, the fusion might be limited to the segments with actual instability.

ABBREVIATION

MI, minimally invasive.

Interlaminar endoscopic lateral recess decompression-surgical technique and early clinical results

BACKGROUND

Lateral recess stenosis is a common pathology causing de-novo or residual radicular pain following lumbar spine surgery. Diagnostic criteria and treatment strategies for symptomatic lateral recess stenosis are not well established.

METHODS

We identified ten patients in our prospective patient database (n=146) who underwent endoscopic interlaminar decompression for unilateral symptomatic lateral recess stenosis. Lateral recess height and angle were measured on axial T2-weighted MRI. Values from the symptomatic side were compared to the contralateral side which served as asymptomatic control. Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) for back and leg pain were collected preoperatively, postoperatively and at last follow-up.

RESULTS

Preoperative MRI revealed that both lateral recess angle and height were significantly smaller on the symptomatic compared to the asymptomatic side (angle: 19.3° vs. 35.7°; height: 2.9 vs. 5.7 mm; P<0.01). All patients tolerated endoscopic interlaminar decompression well and half of the patients were discharged on the day of surgery. At last follow-up (12.6±1.7 months), 8 out of 10 patients experienced a minimally clinically important improvement of their VAS for ipsilateral leg pain, which improved from 7.2±0.5 preoperatively to 2.5±0.8 postoperatively (P=0.001). The back pain VAS also improved (preoperatively 5.1±1.1 vs. postoperatively 1.7±0.9, P<0.05). The ODI improved from 50±5.8 preoperatively to 22.2±5.1 at last follow-up (P=0.001). One patient experienced persistent leg pain.

CONCLUSIONS

Lateral recess height and angle correlate with symptomatic lateral recess stenosis which is effectively treated utilizing interlaminar endoscopic lateral recess decompression.

Ten-Step Minimally Invasive Spine Lumbar Decompression and Dural Repair Through Tubular Retractors

BACKGROUND: Minimally invasive spine (MIS) surgery utilizing tubular retractors has become an increasingly popular approach for decompression in the lumbar spine. However, a better understanding of appropriate indications, efficacious surgical techniques, limitations, and complication management is required to effectively teach the procedure and to facilitate the learning curve.

OBJECTIVE: To describe our experience and recommendations regarding tubular surgery for lumbar disc herniations, foraminal compression with unilateral radiculopathy, lumbar spinal stenosis, synovial cysts, and dural repair.

METHODS: We reviewed our experience between 2008 and 2014 to develop a step-by-step description of the surgical techniques and complication management, including dural repair through tubes, for the 4 lumbar pathologies of highest frequency. We provide additional supplementary videos for dural tear repair, laminotomy for bilateral decompression, and synovial cyst resection.

RESULTS: Our overview and complementary materials document the key technical details to maximize the success of the 4 MIS surgical techniques. The review of our experience in 331 patients reveals technical feasibility as well as satisfying clinical results, with no postoperative complications associated with cerebrospinal fluid leaks, 1 infection, and 17 instances (5.1%) of delayed fusion.

CONCLUSION: MIS surgery through tubular retractors is a safe and effective alternative to traditional open or microsurgical techniques for the treatment of lumbar degenerative disease. Adherence to strict microsurgical techniques will allow the surgeon to effectively address bilateral pathology while preserving stability and minimizing complications.

Biological Treatment Approaches for Degenerative Disk Disease: A Literature Review of In Vivo Animal and Clinical Data

STUDY DESIGN

Literature review.

OBJECTIVE

Degenerative disk disease (DDD) has a negative impact on quality of life and is a major cause of morbidity worldwide. There has been a growing interest in the biological repair of DDD by both researchers and clinicians alike. To generate an overview of the recent progress in reparative strategies for the treatment of DDD highlighting their promises and limitations, a comprehensive review of the current literature was performed elucidating data from in vivo animal and clinical studies.

METHODS

Articles and abstracts available in electronic databases of PubMed, Web of Science, and Google Scholar as of December 2014 were reviewed. Additionally, data from unpublished, ongoing clinical trials was retrieved from clinicaltrials.gov and available abstracts from research forums. Data was extracted from the most recent in vivo animal or clinical studies involving any of the following: (1) treatment with biomolecules, cells, or tissue-engineered constructs and (2) annulus fibrosus repair.

RESULTS

Seventy-five articles met the inclusion criteria for review. Among these, 17 studies involved humans; 37, small quadrupeds; and 21, large quadrupeds. Findings from all treatments employed demonstrated improvement either in regenerative capacity or in pain attenuation, with the exception of one clinical study.

CONCLUSION

Published clinical studies on cell therapy have reported encouraging results in the treatment of DDD and resultant back pain. We expect new data to emerge in the near future as treatments for DDD continue to evolve in parallel to our greater understanding of disk health and pathology.

Minimally Invasive Spinal Surgery in the Elderly: Does It Make Sense?

Lumbar degenerative disease can have varied pathoanatomy, with stenosis, spondylolisthesis, and scoliosis contributing to significant pain and disability. Among appropriately selected patients, surgical intervention can treat both back pain and leg pain and improve quality of life in a cost-effective manner with an acceptable safety profile. The evolution of minimally invasive surgical (MIS) techniques offers the potential to decrease the physiological impact of surgery and to improve the complication profile while achieving the same spine surgical objectives. The utility of such techniques among elderly patients >65 years of age has not been rigorously evaluated, and this systematic review sought to define the utility and safety of MIS spinal surgery for decompression, interbody fusion, and deformity correction in this population. Review of 2 studies for MIS lumbar decompression reveals that the majority of elderly patients exhibit significant improvements in pain (change in visual analog score for leg pain, 3.4 points) and disability (change in Oswestry Disability Index, 19 points), with inadvertent durotomy in 3% of patients. Review of 4 studies for MIS lumbar interbody fusion reveals robust improvement in pain (change in visual analog score for leg pain, 3.4 points; change in visual analog score for back pain, 7.2 points), with inadvertent durotomy in 5% of patients. Narrative review was performed for adult degenerative deformity correction, revealing that MIS techniques are feasible for managing such patients with acceptable rates of osseous union and complication. On the basis of largely low-quality, retrospective evidence, we recommend that elderly patients should not be excluded from MIS interventions for symptomatic lumbar degenerative spinal disease.

Adult Degenerative Scoliosis

The treatment of adult degenerative scoliosis begins in the outpatient setting when evaluating a patient both radiographically. Assessing the flexibility of the deformity is essential in determining what techniques will be required to achieve the goals of correction. Ultimately the surgeon's comfort and experience and the patient's medical risk stratification determine the strategy needed to address either a focal pathology or ultimate deformity correction.

Economic impact of minimally invasive lumbar surgery

Cost effectiveness has been demonstrated for traditional lumbar discectomy, lumbar laminectomy as well as for instrumented and noninstrumented arthrodesis. While emerging evidence suggests that minimally invasive spine surgery reduces morbidity, duration of hospitalization, and accelerates return to activites of daily living, data regarding cost effectiveness of these novel techniques is limited. The current study analyzes all available data on minimally invasive techniques for lumbar discectomy, decompression, short-segment fusion and deformity surgery. In general, minimally invasive spine procedures appear to hold promise in quicker patient recovery times and earlier return to work. Thus, minimally invasive lumbar spine surgery appears to have the potential to be a cost-effective intervention. Moreover, novel less invasive procedures are less destabilizing and may therefore be utilized in certain indications that traditionally required arthrodesis procedures. However, there is a lack of studies analyzing the economic impact of minimally invasive spine surgery. Future studies are necessary to confirm the durability and further define indications for minimally invasive lumbar spine procedures.

Treatment results in the different surgery of intradural extramedullary tumor of 122 cases

Study Design

A retrospective study of intradural extramedullary tumor.

Objective

To compare the treatment results in the different surgeries of spinal intradural extramedullary tumor.

Methods

The study retrospectively reviewed 122 patients. The minimally invasive surgery (MIS) group was divided into Group A (hemilaminectomy + tumor microscopic excision) and Group B (laminectomy + tumor microscopic excision + pedicle screw fixation). Meanwhile, the non-MIS group was divided into Group C (hemilaminectomy + tumor excision), Group D (laminectomy + tumor excision), and Group E (laminectomy + tumor excision + pedicle screw fixation). In order to study postoperative spinal stability, we simultaneously divided all of the subjects into three categories, namely Group HE: hemilaminectomy + tumor excision; Group LE: laminectomy + tumor excision; and Group LEPSF: laminectomy + tumor excision + pedicle screw fixation.

Results

The MIS group exhibited fewer postoperative complications (p<0.05), better short-term clinical efficacy (p<0.05) and less non-surgical cost (p<0.05) than in non-MIS group. The rate of postoperative spinal instability in hemilaminectomy was lower than in laminectomy in a single spinal segment (p<0.05). The rate of postoperative spinal instability in laminectomy + pedicle screw fixation was lower than in hemilaminectomy and laminectomy in two or more spinal segments (p<0.05).

Conclusion

In the case of appropriate surgical indications, minimally invasive surgery for intradural extramedullary tumor is a useful method that can successfully produce good clinical results and reduce non-surgical cost. In addition, pedicle screw fixation helps avoid spinal postoperative instability.