Guidelines for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 17: bone growth stimulators and lumbar fusion

The Results of Using a Transforaminal Lumbar Interbody Fusion Cage at the Upper Lumbar Level

Aim

The aim of this study is to apply surgical treatments to upper lumbar disc hernias in order to provide lumbar stability and lumbar lordosis using a transforaminal lumbar interbody fusion (TLIF) cage and to preserve the success rate of surgical results by protecting neural structures without excessive subject tension.

Material and methods

Between 2012 and 2017, 32 patients who had undergone an operation for upper lumbar disc herniation and who had received a transforaminal lumbar interbody fusion cage using a posterior technique were evaluated retrospectively.

Results

The radiological and clinical findings, surgical methods, and results of the patients were evaluated. In our study, 25 (78.1%) of the patients with upper lumbar disc hernias who were evaluated retrospectively were female and seven (21.9%) were male. Their average age was 55.43 years. The average follow-up was 21.75 months. The most common complaints were lower back pain, leg pain, and claudication. In the findings from neurological examinations, a positive result on the femoral stretching test occurred in 30 (93.7%) patients. In the degenerative spinal structure of patients at the L1-2 and L2-3 levels, a transforaminal lumbar interbody fusion was performed via a wide laminectomy with posterior stabilization due to a wide-bottomed disc hernia and stenosis. Only one of the patients with a neurological deficit still had a motor deficit after surgery.

Conclusion

While planning a surgery for upper lumbar disc hernias, the anatomical features of this region and the patients' radiological and neurological findings should be carefully evaluated. If TLIF is performed during upper lumbar region surgery, it may be preferable to perform it using a posterior technique.

Limited post-operative dexamethasone use does not affect lumbar fusion: a single institutional experience

Background

The use of exogenous dexamethasone during and after lumbar spine surgery remains controversial. The preponderance of studies on this topic is primarily from animal models and little is known about the effects of exogenous dexamethasone use on fusion outcomes in human subjects undergoing lumbar arthrodesis. The aim of this study is to investigate the effect of limited exogenous dexamethasone use on bone fusion after instrumented lumbar arthrodesis.

Methods

Consecutive adult patients (18 years and older) undergoing one and two level lumbar decompression and fusion between January 2013 and December 2014 were reviewed. Patients were dichotomized into one of two groups (A & B) based on whether they received dexamethasone-Group (A) dexamethasone; and Group (B) no dexamethasone. Baseline characteristics, operative details, length of hospital stay, rates of wound infection, and fusion rates at 1 year were gathered by direct medical record review. All patients enrolled in this study were followed for a minimum of 12 months after surgery.

Results

One hundred sixty-five consecutive patients undergoing 1- and 2-level fusions were included in the study. Fifty eight patients received dexamethasone and 107 patients did not. The mean ± SD age was similar between both cohorts ("dexamethasone": 58.12±16.25 years vs. "no dexamethasone": 61.00±12.95, P=0.24). The was no difference in the prevalence of smoking (P=0.72) between both cohorts. Length of in-hospital stay was similar between cohorts ("dexamethasone": 4.08±3.44 days vs. "no dexamethasone": 4.50±2.85 days, P=0.43). The incidence of post-operative infections was similar between cohorts. At 12 months after surgery, 70% of patients in the dexamethasone cohort had radiographic evidence of bony fusion compared to 73% of patients in the no-dexamethasone cohort (P=0.68).

Conclusions

Our study suggests that a limited exposure to exogenous dexamethasone after lumbar spine fusion may not be associated with a lower fusion rate. Prospective randomized control trials are needed to corroborate our findings.

Rational decision making in a wide scenario of different minimally invasive lumbar interbody fusion approaches and devices

With the proliferation of a variety of modern MIS spine surgery procedures, it is mandatory that the surgeon dominate all aspects involved in surgical indication. The information related to the decision making in patient selection for specific procedures is mandatory for surgical success. The objective of this study is to present decision-making criteria in minimally invasive surgery (MIS) selection for a variety of patients and pathologies. In this article, practicing surgeons who specialize in various MIS approaches for spinal fusion were engaged to provide expert opinion and literature review on decision making criteria for several MIS procedures. Pros, cons, relative limitations, and case examples are provided for patient selection in treatment with MIS posterolateral fusion (MIS-PLF), mini anterior lumbar interbody fusion (mini-ALIF), lateral interbody fusion (LLIF), MIS posterior lumbar interbody fusion (MIS-PLIF) and MIS transforaminal lumbar interbody fusion (MIS-TLIF). There is a variety of aspects to consider when deciding which modern MIS surgical approach is most appropriate to use based on patient and pathologic characteristics. The surgeon must adapt them to the characteristic of each type of patients, helping them to choose the most effective and efficient therapeutic option for each case.

Radiographic and Clinical Outcome of Silicate-substituted Calcium Phosphate (Si-CaP) Ceramic Bone Graft in Spinal Fusion Procedures

STUDY DESIGN

Retrospective cohort study.

OBJECTIVE

To evaluate the radiographic and clinical outcome of silicate-substituted calcium phosphate (Si-CaP), utilized as a graft substance in spinal fusion procedures.

SUMMARY OF BACKGROUND DATA

Specific properties of Si-CaP provide the graft with negative surface charge that can result in a positive effect on the osteoblast activity and neovascularization of the bone.

METHODS

This study included those patients who underwent spinal fusion procedures between 2007 and 2011 in which Si-CaP was used as the only bone graft substance. Fusion was evaluated on follow-up CT scans. Clinical outcome was assessed using Oswestry Disability Index, Neck Disability Index, and the visual analogue scale (VAS) for back, leg, neck, and arm pain.

RESULTS

A total of 234 patients (516 spinal fusion levels) were studied. Surgical procedures consisted of 57 transforaminal lumbar interbody fusion, 49 anterior cervical discectomy and fusion, 44 extreme lateral interbody fusion, 30 posterior cervical fusions, 19 thoracic fusion surgeries, 17 axial lumbar interbody fusions, 16 combined anterior and posterior cervical fusions, and 2 anterior lumbar interbody fusion. At a mean radiographic follow-up of 14.2±4.3 months, fusion was found to be present in 82.9% of patients and 86.8% of levels. The highest fusion rate was observed in the cervical region. At the latest clinical follow-up of 21.7±14.2 months, all clinical outcome parameters showed significant improvement. The Oswestry Disability Index improved from 45.6 to 13.3 points, Neck Disability Index from 40.6 to 29.3, VAS back from 6.1 to 3.5, VAS leg from 5.6 to 2.4, VAS neck from 4.7 to 2.7, and VAS arm from 4.1 to 1.7. Of 7 cases with secondary surgical procedure at the index level, the indication for surgery was nonunion in 3 patients.

CONCLUSIONS

Si-CaP is an effective bone graft substitute. At the latest follow-up, favorable radiographic and clinical outcome was observed in the majority of patients.

LEVEL OF EVIDENCE

Level-III.

Cross-Sectional Area of the Lumbar Spine Trunk Muscle and Posterior Lumbar Interbody Fusion Rate: A Retrospective Study

STUDY DESIGN

A retrospective study.

OBJECTIVE

To investigate the relationship between trunk muscle cross-sectional area (MCSA) and fusion rate after posterior lumbar interbody fusion using pedicle screw fixation (PLIF-PSF).

SUMMARY OF BACKGROUND DATA

Although trunk muscles of the lumbar spine contribute to spinal stability and alignment, effect of trunk muscles on spinal fusion rate and time to fusion is unclear.

METHODS

A total of 192 adult patients with degenerative lumbar disease who underwent PLIF-PSF at L3-L4 or L4-L5 were included. The MCSA of the flexor (psoas major, PS), extensor (erector spinae, ES; multifidus, MF) were measured using preoperative lumbar magnetic resonance imaging at 3 segments. Bone union was evaluated using lumbar dynamic plain radiography. Patients were divided into 2 groups according to the presence of bone fusion.

RESULTS

Most PS MCSAs in the fusion group were significantly larger than in the nonfusion group, except for MCSA at the L2-L3 segment (all P<0.05). In cases of ES and MF MCSAs, 4 of 6 segments were significantly large. Multivariate analysis revealed that the PS MCSA at L4-L5 was an independent factor for decreased possibility of nonfusion status in both segments (OR=0.812, P=0.028). Pearson analysis demonstrated that the most trunk MCSAs were negatively correlated with time to fusion for both segments and PS MCSAs exhibited a significant correlation with time to fusion except for MCSA at the L2-L3 segment.

CONCLUSIONS

Trunk MCSAs were significantly larger for a fusion group than a nonfusion group. As trunk MCSAs increased, fusion timing decreased.

Electrical stimulation to enhance spinal fusion: a systematic review

Study Design Systematic review. Clinical Questions Compared with no stimulation, does electrical stimulation promote bone fusion after lumbar spinal fusion procedures? Does the effect differ based on the type of electrical stimulation used? Methods Electronic databases and reference lists of key articles were searched up to October 15, 2013, to identify randomized controlled trials (RCTs) comparing the effect of electrical stimulation to no electrical stimulation on fusion rates after lumbar spinal fusion for the treatment of degenerative disease. Two independent reviewers assessed the strength of evidence using the Grades of Recommendation Assessment, Development and Evaluation (GRADE) criteria. Results Six RCTs met the inclusion criteria. The following types of electrical stimulation were investigated: direct current (three studies), pulsed electromagnetic field (three studies), and capacitive coupling (one study). The control groups consisted of no stimulation (two studies) or placebo (four studies). Marked heterogeneity in study populations, characteristics, and design prevented a meta-analysis. Regardless of the type of electrical stimulation used, cumulative incidences of fusion varied widely across the RCTs, ranging from 35.4 to 90.6% in the intervention groups and from 33.3 to 81.9% in the control groups across 9 to 24 months of follow-up. Similarly, when stratified by the type of electrical stimulation used, fusion outcomes from individual studies varied, leading to inconsistent and conflicting results. Conclusion Given the inconsistency in study results, possibly due to heterogeneity in study populations/characteristics and quality, we are unable to conclude that electrical stimulation results in better fusion outcomes compared with no stimulation. The overall strength of evidence for the conclusions is low.

Guideline update for the performance of fusion procedures for degenerative disease of the lumbar spine. Part 17: Bone growth stimulators as an adjunct for lumbar fusion

The relationship between the formation of a solid arthrodesis and electrical and electromagnetic energy is well established; most of the information on the topic, however, pertains to the healing of long bone fractures. The use of both invasive and noninvasive means to supply this energy and supplement spinal fusions has been investigated. Three forms of electrical stimulation are routinely used: direct current stimulation (DCS), pulsed electromagnetic field stimulation (PEMFS), and capacitive coupled electrical stimulation (CCES). Only DCS requires the placement of electrodes within the fusion substrate and is inserted at the time of surgery. Since publication of the original guidelines, few studies have investigated the use of bone growth stimulators. Based on the current review, no conflict with the previous recommendations was generated. The use of DCS is recommended as an option for patients younger than 60 years of age, since a positive effect on fusion has been observed. The same, however, cannot be stated for patients over 60, because DCS did not appear to have an impact on fusion rates in this population. No study was reviewed that investigated the use of CCES or the routine use of PEMFS. A single low-level study demonstrated a positive impact of PEMFS on patients undergoing revision surgery for pseudarthrosis, but this single study is insufficient to recommend for or against the use of PEMFS in this patient population.

Hydroxyapatite-Based Biomaterials Versus Autologous Bone Graft in Spinal Fusion: An In Vivo Animal Study

STUDY DESIGN

An in vivo study was designed to compare the efficacy of biomimetic magnesium-hydroxyapatite (MgHA) and of human demineralized bone matrix (HDBM), both dispersed in a mixture of biomimetic MgHA nanoparticles, with that of an autologous bone graft.

OBJECTIVE

The objective of this study was to evaluate 2 new bone substitutes as alternatives to a bone autograft for spinal fusion, determining their osteoinductive and osteoconductive properties, and their capacity of remodeling, using a large animal model.

SUMMARY OF BACKGROUND DATA

Spinal fusion is a common surgical procedure and it is performed for different conditions. A successful fusion requires potentially osteogenic, osteoinductive, and osteoconductive biomaterials.

METHODS

A posterolateral spinal fusion model involved 18 sheep, bilaterally implanting test materials between the vertebral transverse processes. The animals were divided into 2 groups: 1 fusion level was treated with MgHA (group 1) or with HDBM-MgHA (group 2). The other fusion level received bone autografts in both groups.

RESULTS

Radiographical, histological, and microtomographic results indicated good osteointegration between the spinous process and the vertebral foramen for both materials. Histomorphometry revealed no significant differences between MgHA and autologous bone for all the parameters examined, whereas significantly lower values of bone volume were observed between HDBM-MgHA and autologous bone. Moreover, the normalization of the histomorphometric data with autologous bone revealed that MgHA showed a significantly higher value of bone volume and a lower value of trabecular number, more similar to autologous bone than HDBM-MgHA.

CONCLUSION

The study showed that the use of MgHA in an ovine model of spinal fusion led to the deposition of new bone tissue without qualitative and quantitative differences with respect to new bone formed with autologous bone, whereas the HDBM-MgHA led to a reduced deposition of newly formed bone tissue.

LEVEL OF EVIDENCE

N/A.

Biomechanical comparison of anterior lumbar interbody fusion: stand-alone interbody cage versus interbody cage with pedicle screw fixation -- a finite element analysis

Background

Anterior lumbar interbody fusion (ALIF) followed by pedicle screw fixation (PSF) is used to restore the height of the intervertebral disc and provide stability. Recently, stand-alone interbody cage with anterior fixation has been introduced, which eliminates the need for posterior surgery. We compared the biomechanics of the stand-alone interbody cage to that of the interbody cage with additional PSF in ALIF.

Methods

A three-dimensional, non-linear finite element model (FEM) of the L2-5 segment was modified to simulate ALIF in L3-4. The models were tested under the following conditions: (1) intact spine, (2) destabilized spine, (3) with the interbody cage alone (type 1), (4) with the stand-alone cage with anterior fixation (SynFix-LR®; type 2), and (5) with type 1 in addition to PSF (type 3). Range of motion (ROM) and the stiffness of the operated level, ROM of the adjacent segments, load sharing distribution, facet load, and vertebral body stress were quantified with external loading.

Results

The implanted models had decreased ROM and increased stiffness compared to those of the destabilized spine. The type 2 had differences in ROM limitation of 8%, 10%, 4%, and 6% in flexion, extension, axial rotation, and lateral bending, respectively, compared to those of type 3. Type 2 had decreased ROM of the upper and lower adjacent segments by 3-11% and 3-6%, respectively, compared to those of type 3. The greatest reduction in facet load at the operated level was observed in type 3 (71%), followed by type 2 (31%) and type 1 (23%). An increase in facet load at the adjacent level was highest in type 3, followed by type 2 and type 1. The distribution of load sharing in type 2 (anterior:posterior, 95:5) was similar to that of the intact spine (89:11), while type 3 migrated posterior (75:25) to the normal. Type 2 reduced about 15% of the stress on the lower vertebral endplate compared to that in type 1. The stress of type 2 increased two-fold compared to the stress of type 3, especially in extension.

Conclusions

The stand-alone interbody cage can provide sufficient stability, reduce stress in adjacent levels, and share the loading distribution in a manner similar to an intact spine.

Silicate-substituted calcium phosphate ceramic bone graft replacement for spinal fusion procedures

STUDY DESIGN

Retrospective study.

OBJECTIVE

To assess the clinical and radiographical outcomes in spinal fusion procedures using silicate-substituted calcium phosphate (Si-CaP).

SUMMARY OF BACKGROUND DATA

Si-CaP is a newer-generation synthetic ceramic designed to maximize osteoinduction and osteoconduction.

METHODS

This is a retrospective analysis of a prospectively collected patient database including 108 patients (204 individual spinal levels). Different surgical procedures performed included 25 anterior cervical discectomy and fusions, 17 posterior cervical fusions, 7 combined anterior and posterior cervical fusions, 10 thoracic fusion surgeries, 18 transforaminal lumbar interbody fusions with 12 axial lumbar interbody fusions, 11 transpsoas discectomy and fusions, and 8 combined thoracolumbar fusion procedures. Si-CaP was used as bone extender without any additional graft material, bone marrow aspirate, or bone morphogenetic protein. Clinical outcomes were assessed using the visual analogue scale (VAS), Oswestry Disability Index, and Neck Disability Index. Fusion was determined by the presence of bony bridging on 2 consecutive sections in at least 2 planes on computed tomographic imaging.

RESULTS

At a follow-up of 12 (± 4.7) months, 90% of all patients demonstrated radiographical fusion. Fusion rates were highest in the cervical spine (97%) followed by thoracic and lumbar spines (86% and 81%, respectively). There were significant improvements in all clinical outcome measures-Oswestry Disability Index, 11.1 (± 10.2) and Neck Disability Index, 9.0 (± 11.4); VAS-back, 3.1(± 3.0); VAS-leg, 3.5 (± 3.6); VAS-neck, 3.7 (± 2.5); and VAS-arm 4.0 (± 3.2). There was no radiographical loosening of instrumentation due to infection or nonunion in this series, and no subsequent revisions for nonunion were required.

CONCLUSION

Si-CaP is an alternative to autogenous bone graft in spinal arthrodesis procedures. At 12-month follow-up, we detected high levels of bony fusion using Si-CaP in combination with various surgical spinal techniques.

Lateral interbody fusion for treatment of discogenic low back pain: minimally invasive surgical techniques

Low back pain is one of the most common ailments in the general population, which tends to increase in severity along with aging. While few patients have severe enough symptoms or underlying pathology to warrant surgical intervention, in those select cases treatment choices remain controversial and reimbursement is a substancial barrier to surgery. The object of this study was to examine outcomes of discogenic back pain without radiculopathy following minimally-invasive lateral interbody fusion. Twenty-two patients were treated at either one or two levels (28 total) between L2 and 5. Discectomy and interbody fusion were performed using a minimallyinvasive retroperitoneal lateral transpsoas approach. Clinical and radiographic parameters were analyzed at standard pre- and postoperative intervals up to 24 months. Mean surgical duration was 72.1 minutes. Three patients underwent supplemental percutaneous pedicle screw instrumentation. Four (14.3%) stand-alone levels experienced cage subsidence. Pain (VAS) and disability (ODI) improved markedly postoperatively and were maintained through 24 months. Segmental lordosis increased significantly and fusion was achieved in 93% of levels. In this series, isolated axial low back pain arising from degenerative disc disease was treated with minimally-invasive lateral interbody fusion in significant radiographic and clinical improvements, which were maintained through 24 months.

Nerve injury during the transpsoas approach for lumbar fusion

A lateral transpsoas approach to achieve interbody fusion in the lumbar spine using either the extreme lateral interbody fusion or direct lateral interbody fusion technique is an increasingly popular method to treat spinal disease. Dissection and dilation through the iliopsoas muscle places the lumbosacral plexus at risk for injury, but there is very limited information in the published literature about adverse clinical events resulting in postoperative motor deficits or reports of failure of electrophysiological monitoring to detect nerve injury. The authors present 2 cases of postoperative motor deficits following the transpsoas approach not detected by intraoperative monitoring, review the medical literature, and discuss strategies for complication avoidance.

Evidence-based spine surgery

STUDY DESIGN

Literature review.

OBJECTIVE

To describe the state of the literature regarding the performance of lumbar fusion for low back pain due to degenerative disease of the spine.

SUMMARY OF BACKGROUND DATA

The effectiveness and costs associated with spinal surgery have been a topic of significant debate in both the popular press and professional literature.

METHODS

Evidence-based medicine techniques have been applied to many areas of spinal surgery. The results of these analyses are being used by practicing physicians, payors, and others to determine what procedures are appropriate for certain patient populations.

RESULTS

This manuscript describes the methodology, strengths, and weaknesses of evidence-based medicine approaches to spinal surgery. The case for lumbar fusion as a treatment for chronic low back pain due to degenerative disc disease is described as an example.

CONCLUSION

Evidence-based medicine is a useful tool for summarizing and grading the evidence available in the literature for or against a particular treatment strategy. Its utility is limited by the quality of the primary literature, and the absence of proof cannot be equated with the proof of absence.