Fusion rates and SF-36 outcomes after multilevel laminectomy and noninstrumented lumbar fusions in a predominantly geriatric population

STUDY DESIGN: This study prospectively analyzed posterolateral fusion rates and Short-Form 36 (SF-36) outcomes after multilevel lumbar laminectomies and noninstrumented fusions. OBJECTIVE: SF-36 outcomes and posterolateral fusion rates were assessed. SUMMARY OF BACKGROUND DATA: Technologically advanced and expensive instrumentation techniques and fusion adjuncts (ie, bone morphogenetic protein) may not be necessary to achieve lumbar fusion in the geriatric population. Rather, noninstrumented fusions using lamina autograft and a bone volume expander may suffice. METHODS: Seventy-five patients averaging 69 years of age (49 females, 26 males) underwent average 4.9 level lumbar laminectomies with average 2.0 level noninstrumented posterolateral fusions using lamina autograft (average 30 cm) supplemented with demineralized bone matrix (average 30 cm) in a 50:50 mix. Two independent radiologists separately evaluated both 2-dimensional computed tomography (2D-CT) and dynamic x-ray data 3, 4.5, 6, and up to 12 months postoperatively; patients had to demonstrate fusion on both studies. Outcomes were assessed using the SF-36 questionnaire (preoperatively) 3, 6, 12, and 24 months postoperatively. Patients were followed an average of 3.3 years (minimum 2 y). RESULTS: Thirteen (17.3%) patients demonstrated pseudarthrosis as they had not fused on dynamic x-ray and/or 2D-CT studies an average of 5.6 months postoperatively. One patient required a secondary fusion. One and 2 years postoperatively, patients demonstrated nearly identical maximal improvement on 6 SF-36 Health Scales, but showed no real changes on General Health and Mental Health scales. CONCLUSIONS: Seventy-five predominantly geriatric patients underwent multilevel laminectomies with noninstrumented fusions using lamina autograft combined with a bone volume expander. Thirteen patients (17.3%) demonstrated pseudarthrosis on the basis of both dynamic x-ray and 2D-CT criteria; 1 patient required a second instrumented fusion. Moderate pseudarthrosis rates, a low reoperation rate, and satisfactory SF-36 outcomes were achieved using noninstrumented posterolateral fusions in a predominantly geriatric population.     

An analysis of noninstrumented posterolateral lumbar fusions performed in predominantly geriatric patients using lamina autograft and beta tricalcium phosphate

BACKGROUND CONTEXT: The artificial bone-volume expander, beta tricalcium phosphate (B-TCP, Vitoss, OrthoVita, Malvern, PA), is increasingly used to supplement autograft in posterolateral lumbar fusions. PURPOSE: To determine fusion rates/outcomes using B-TCP/autograft. STUDY DESIGN/SETTING: Fusion rates and outcomes were assessed for 60 predominantly geriatric patients undergoing multilevel lumbar laminectomies and 1- to 2-level noninstrumented fusions using B-TCP/autograft. PATIENT SAMPLE: Patients on average were 70 years old. OUTCOME MEASURES: Odom's criteria and Short-Form 36 (SF-36) outcomes were studied 2 years postoperatively. METHODS: Sixty patients underwent an average of 5.4-level laminectomies with 1- to 2-level noninstrumented fusions. Based on dynamic X-ray/magnetic resonance/computed tomography (CT) studies, laminectomies addressed multilevel stenosis (60 patients), ossification of the yellow ligament (46 patients), disc herniations (20 patients), or synovial cysts (8 patients), and fusions addressed degenerative spondylolisthesis (48 patients), spondylolisthesis/lysis (2 patients), or degenerative scoliosis (10 patients). The fusion mass on each side contained half of all harvested autograft combined with one to 1.5 strips of B-TCP (saturated in 10cc of bone marrow aspirate/strip). Fusion rates were documented by two independent neuroradiologists using both dynamic X-rays, and thin-cut CT (2-dimensional/3-dimensional CT) studies obtained up to 2 years postoperatively. Odom's criteria and SF-36 outcomes were assessed over the same interval. RESULTS: Pseudarthrosis was documented in nine (15%) patients. Two years postoperatively, Odom's criteria revealed 28 excellent, 23 good, 5 fair, and 4 poor results, whereas SF-36 data revealed improvement on 6 of 8 Health Scales in all patients. CONCLUSIONS: A 15% pseudarthrosis rate followed multilevel laminectomy and 1- to 2-level noninstrumented posterolateral fusion using lamina autograft/B-TCP.     

A preliminary study of the efficacy of Beta Tricalcium Phosphate as a bone expander for instrumented posterolateral lumbar fusions

The associated morbidity of allograft(s) as bone graft expanders in spinal surgery has prompted the search for alternatives. The efficacy of Vitoss/Beta Tricalcium Phosphate (B-TCP: OrthoVita, Malvern PA, USA), an artificial bone substitute, combined with lamina autograft (50:50 mix) in 40 prospective posterolateral fusions utilizing pedicle/screw instrumentation was analyzed. Multilevel lumbar laminectomies (average 3.7 levels) were accompanied by 1 (27 patients) and 2 level (13 patients) fusions. Two neuroradiologists independently assessed fusion progression on dynamic x-rays and 2D-CT studies performed at 3, 6, and up to 12 months postoperatively. Outcomes were quantified utilizing Odom Criteria and Short-Form 36 (SF-36) questionnaires (preoperatively; and 3, 6, and 12 months postoperatively). By the sixth postoperative month, fusion was neuroradiologically confirmed on both dynamic x-rays and CT studies for 26 of 27 single level fusions (1 pseudarthrosis), and 11 of 13 two level fusions (L4-S1). Odom Criteria 3, 6, and 12 months postoperatively revealed continued improvement for all patients. SF-36 outcomes, however, revealed deterioration on 2 Health Scales (Role Physical, Role Emotional) 3 and 6 months post-operatively, and minimal to marked improvement on 6 Health Scales (PF, V, PF, V, SF, BP). Twelve months postoperatively improvement occurred on all 8 Health Scales, exceeding pre-operative baselines; minimal (RP, GH), mild (MH), moderate (PF, BP, V, SF), and marked improvement (RE). Although Vitoss/B-TCP and laminar autograft resulted in pseudarthrosis for 1 of 27 single level and 2 of 13 two level posterolateral instrumented lumbar fusions, only 1 of the latter patients required a secondary fusion.     

SF-36 outcomes and fusion rates after multilevel laminectomies and 1 and 2-level instrumented posterolateral fusions using lamina autograft and demineralized bone matrix

Short-Form 36 (SF-36) outcomes and fusion rates were assessed after multilevel laminectomies and 1 (95 patients) or 2-level (45 patients) instrumented fusions. The posterolateral fusion mass consisted of lamina autograft and demineralized bone matrix (Osteofil/ICM: Sofamor Danek, Memphis, TN) in a 50:50 mix. SF-36 questionnaires were administered preoperatively and 3, 6, and 12 months postoperatively. Two independent neuroradiologists (blinded to study design) separately documented fusion on both dynamic x-rays and two-dimensional-computed tomography (2D-CT) studies performed 3, 6, and up to 12 months postoperatively until arthrodesis was demonstrated. Patients were followed an average of 3 years in both fusion series (minimum of 1.5 y). One-year postoperatively, comparably improved outcomes were observed for both groups on 6 of 8 Health Scales of the SF-36. 2D-CT studies documented 1-level fusion an average of 5.2 months (Standard Deviation 1.8) postoperatively in 88 (92.6%) of 95 cases, whereas dynamic x-rays confirmed fusion in 93 (98%) patients. For 2 patients undergoing 1-level fusions, both 2D-CT and dynamic x-ray documented pseudarthrosis/instability; both patients required secondary surgery an average of 8 months postoperatively. 2D-CT documented 2-level fusion an average of 6.1 months (Standard Deviation 1.9) postoperatively in 41 of 45 (91.2%) patients, whereas dynamic x-rays confirmed fusion in 43 (96%) patients. For 2 patients undergoing 2-level fusions, both 2D-CT and dynamic x-rays documented pseudarthrosis/instability; both patients required secondary fusion an average of 10 months postoperatively. High fusion rates and adequate outcomes were observed after multilevel laminectomies and 1 and 2-level instrumented posterolateral fusions performed using lamina autograft and demineralized bone matrix: Osteofil/ICM.     

Use of biphasic calcium phosphate versus demineralized bone matrix: retrospective clinical and CT analysis of posterolateral fusion results

Purpose

Bone graft extenders have been developed to prevent donor site morbidity associated with iliac crest bone graft, but few studies compared the efficacy of various substitutes. Our purpose was to determine fusion rate and clinical outcome in patients undergoing lumbar arthrodesis using demineralized bone matrix (DBM) and biphasic calcium phosphate (BCP).

Methods

Patients with degenerative spondylolisthesis undergoing one-level or two-level arthrodesis of lumbar spine were retrospectively reviewed. Two treatment groups placed either BCP or DBM, in addition to local autograft in lumbar posterolateral space. Three-dimensional CT exam and dynamic flexion–extension radiographs at postoperative 2-year were assessed for posterolateral fusion status and pain scale and Oswestry Disability Index (ODI) for clinical outcome.

Results

Of the 148 patients reviewed (including 23 in one- and 58 patients in two-level in BCP group, and 47 in one- and 20 patients in two-level in DBM group), no significant differences were found in terms of age, sex, BMI, smoking, diabetes, steroids, number of level fused, non-union rate or revision surgery between BCP and DBM groups. Significantly improved pain scale of back and leg and ODI were found in both groups postoperatively without group difference. We found a comparable fusion rate in one-level surgery (100% versus 93.6%) and a superior fusion rate of BCP group in two-level surgery (98.3% versus 80.0%, p = 0.01).

Conclusion

Being a bone graft extender without osteoinductive property, with local autograft, BCP is comparable to DBM for one- and superior for two-level fusion. No significant difference was found in clinical outcomes.

     

Efficacy of different bone volume expanders for augmenting lumbar fusions

BACKGROUND: A wide variety of bone volume expanders are being used in performing posterolateral lumbar noninstrumented and instrumented lumbar fusions. This article presents a review of their efficacy based on fusion rates, complications, and outcomes. METHODS: Lumbar noninstrumented and instrumented fusions frequently use laminar autografts and different bone graft expanders. This review presents the utility of multiple forms/ratios of DBMs containing allografts. It also discusses the efficacy of artificial bone graft substitutes, including HA and B-TCP. Dynamic x-ray and/or CT examinations were used to document fusion in most series. Outcomes were variously assessed using Odom's criteria or different outcome questionnaires (Oswestry Questionnaire, SF-36, Dallas Pain Questionnaire, and/or Low Back Pain Rating Scale). RESULTS: Performing noninstrumented and instrumented lumbar posterolateral fusions resulted in comparable fusion rates in many series. Similar outcomes were also documented based on Odom's criteria or the multiple patient-based questionnaires. However, in some studies, the addition of spinal instrumentation increased the reoperation rate, operative time, blood loss, and cost. Various forms of DBMs, applied in different ratios to autografts, effectively supplemented spinal fusions in animal models and patient series. beta-Tricalcium phosphate, which is used to augment autograft fusions addressing idiopathic scoliosis or lumbar disease, also proved to be effective. CONCLUSIONS: Different types of bone volume expanders, including various forms of allograft-based DBMs, and artificial bone graft substitutes (HA and B-TCP) effectively promote posterolateral lumbar noninstrumented and instrumented fusions when added to autografts.     

Surgical treatment of adjacent instability after lumbar spine fusion.

STUDY DESIGN: This study is a retrospective review of 39 patients with previous instrumented lumbar fusion who underwent secondary spine surgery for lumbar adjacent instability. To the authors' knowledge, this is the largest study of surgical treatment of lumbar adjacent instability in the literature to date. OBJECT: This study evaluated the feasibility of adjacent instability treated with medial facetectomy, fusion with autologous bone grafting, and pedicle screw instrumentation. SUMMARY OF BACKGROUND DATA: The surgical treatment of adjacent instability has seldom been discussed. Revision spine fusions are challenged by high pseudarthrosis rates. METHODS: Thirty-nine patients with previous lumbar fusion underwent second lumbar spine surgery for adjacent instability. All were treated with autogenous posterolateral arthrodesis and transpedicle screw fixation in addition to decompressive laminectomy. Medical records, radiographs, and pain scores were obtained. RESULTS: The clinical results were excellent or good in 76.9% of patients, and the radiographic fusion was successful in 37 (94.9%) of patients. Flat back was noted in 8 (20.5%) of patients. In 5 patients (12.8%), neighboring segment breakdown again developed, and 2 of those patients underwent a third lumbar fusion. Dural tear during operation occurred in 2 patients. One patient experienced cauda equina syndrome but recovered bladder function 1 month later. CONCLUSION: Autogenous posterolateral arthrodesis combined with pedicle screw fixation led to successful radiologic and clinical outcome in patients with lumbar adjacent instability. Adequate decompression of the adjacent stenosis requires medial facetectomy, thus preventing aggressive nerve root manipulation and reducing the incidence of dural tear.     

Radiographic fusion rate after implantation of facet bone dowels

Background contextAchieving a posterolateral fusion in conjunction with performing decompressive laminectomies can prevent recurrence of stenosis or worsening of spondylolisthesis. Facet bone dowels have been introduced and marketed as a less invasive alternative to pedicle screws. Surgeons have been placing them during lumbar laminectomy surgery and coding for intervertebral biomechanical device and posterolateral fusion. These bone dowels have also been placed percutaneously in outpatient surgery centers and pain clinics for facet-mediated back pain.PurposeTo describe fusion outcomes in patients who underwent facet bone dowel placement.Study design/settingRetrospective analysis of a single center's experience.Patient sampleNinety-six patients comprise the entire cohort of patients who underwent facet bone dowel implantation at our institution with adequate postoperative imaging to determine fusion status.Outcome measuresFusion rates as determined on postoperative computed tomography (CT) scans and dynamic lumbar X-rays if CT is not available.MethodsThreaded facet bone dowels in this study were placed according to the manufacturer's recommended methods. The bone dowels were placed after open exploration of the facet complex or percutaneously through a tubular retractor on the contralateral side from a microdiscectomy or synovial cyst resection. The most recent available postoperative imaging was reviewed to determine fusion status.ResultsOf 96 patients in our series, 6 (6.3%) had a fusion seen on CT and 4 did not exhibit any movement on dynamic lumbar X-rays for a total fusion rate of 10.4% (10/96). Eighty-six (89.6%) patients were shown on imaging to not have a solid fusion either by visualizing a patent facet joint on CT or measurable movement between the flexion and the extension lumbar X-rays.ConclusionsThis article is mainly intended to question whether the implantation of facet bone dowels can produce a solid fusion radiographically. In our experience, the placement of facet bone dowels does not equal the time, skill, or attention to detail that is necessary for a posterolateral lumbar arthrodesis, and our follow-up radiographic studies clearly demonstrate an inadequate fusion rate.     

The First Clinical Trial of Beta-Calcium Pyrophosphate as a Novel Bone Graft Extender in Instrumented Posterolateral Lumbar Fusion

Background

Porous β-calcium pyrophosphate (β-CPP) was developed to improve the fusion success of posterolateral lumbar fusion (PLF). The possibility of accomplishing PLF using a mixture of porous β-CPP and iliac bone was studied. This paper reports the radiologic results of PLF using the β-CPP plus autograft for lumbar degenerative disease as a bone graft extender.

Methods

A prospective, case-matched, radiographic study evaluating the results of short segment lumbar fusion using a β-CPP plus autograft was performed to compare the efficacy of β-CPP plus autograft with that of an autograft alone for short segment lumbar fusion. Thirty one consecutive patients (46 levels) underwent posterolateral fusion with pedicle screw fixation and additional posterior lumbar interbody fusion. In all patients, 3 mL of β-CPP plus 3 mL of autogenous bone graft was placed randomly in one side of a posterolateral gutter, and 6 mL of autogenous iliac bone graft was placed on the other. The fusion rates, volumes of fusion masses, and bone absorption percentage were evaluated postoperatively using simple radiographs and 3 dimensional computed tomography (3D-CT) scans.

Results

The control sides treated with an autograft showed significantly better Lenke scores than the study sides treated with β-CPP at 3 and 6 months postoperatively, but there was no difference between the two sides at 12 months. The fusion rates (confirmed by 3D-CT) were 87.0% in the β-CPP group and 89.1% in the autograft group, which were not significantly different. The fusion mass volumes and bone absorption percentage at 12 months postoperatively were 2.49 mL (58.4%) and 1.89 mL (69.5%) for the β-CPP and autograft groups, respectively, and mean fusion mass volume was significantly higher in the β-CPP group.

Conclusions

β-CPP combined with an autograft is as effective as autologous bone for grafting during instrumented posterolateral spinal fusion. These findings suggest that β-CPP bone chips can be used as a novel bone graft extender for short-segment posterolateral spinal fusion.     

The effects of local insulin application to lumbar spinal fusions in a rat model

Background contextThe rates of pseudoarthrosis after a single-level spinal fusion have been reported up to 35%, and the agents that increase the rate of fusion have an important role in decreasing pseudoarthrosis after spinal fusion. Previous studies have analyzed the effects of local insulin application to an autograft in a rat segmental defect model. Defects treated with a time-released insulin implant had significantly more new bone formation and greater quality of bone compared with controls based on histology and histomorphometry. A time-released insulin implant may have similar effects when applied in a lumbar spinal fusion model.PurposeThis study analyzes the effects of a local time-released insulin implant applied to the fusion bed in a rat posterolateral lumbar spinal fusion model. Our hypothesis was twofold: first, a time-released insulin implant applied to the autograft bed in a rat posterolateral lumbar fusion will increase the rate of successful fusion and second, will alter the local environment of the fusion site by increasing the levels of local growth factors.Study designAnimal model (Institutional Animal Care and Use Committee approved) using 40 adult male Sprague-Dawley rats.MethodsForty skeletally mature Sprague-Dawley rats weighing approximately 500 g each underwent posterolateral intertransverse lumbar fusions with iliac crest autograft from L4 to L5 using a Wiltse-type approach. After exposure of the transverse processes and high-speed burr decortication, a Linplant (Linshin Canada, Inc., ON, Canada) consisting of 95% microrecrystalized palmitic acid and 5% bovine insulin (experimental group) or a sham implant consisting of only palmitic acid (control group) was implanted on the fusion bed with iliac crest autograft. As per the manufacturer, the Linplant has a release rate of 2 U/day for a minimum of 40 days. The transverse processes and autograft beds of 10 animals from the experimental and 10 from the control group were harvested at Day 4 and analyzed for growth factors. The remaining 20 spines were harvested at 8 weeks and underwent a radiographic examination, manual palpation, and microcomputed tomographic (micro-CT) examination.ResultsOne of the 8-week control animals died on postoperative Day 1, likely due to anesthesia. In the groups sacrificed at Day 4, there was a significant increase in insulinlike growth factor-I (IGF-I) in the insulin treatment group compared with the controls (0.185 vs. 0.129; p=.001). No significant differences were demonstrated in the levels of transforming growth factor beta-1, platelet-derived growth factor-AB, and vascular endothelial growth factor between the groups (p=.461, .452, and .767 respectively). Based on the radiographs, 1 of 9 controls had a solid bilateral fusion mass, 2 of 9 had unilateral fusion mass, 3 of 9 had small fusion mass bilaterally, and 3 of 9 had graft resorption. The treatment group had solid bilateral fusion mass in 6 of 10 and unilateral fusion mass in 4 of 10, whereas a small bilateral fusion mass and graft resorption were not observed. The difference between the groups was significant (p=.0067). Based on manual palpation, only 1 of 9 controls was considered fused, 4 of 9 were partially fused, and 4 of 9 were not fused. In the treatment group, there were 6 of 10 fusions, 3 of 10 partial fusions, and 1 of 10 were not fused. The difference between the groups was significant (p=.0084). Based on the micro-CT, the mean bone volume of the control group was 126.7 mm³ and 203.8 mm³ in the insulin treatment group. The difference between the groups was significant (p=.0007).ConclusionsThis study demonstrates the potential role of a time-released insulin implant as a bone graft enhancer using a rat posterolateral intertransverse lumbar fusion model. The insulin-treatment group had significantly higher fusion rates based on the radiographs and manual palpation and had significantly higher levels of IGF-I and significantly more bone volume on micro-CT.     

The use of bone morphogenetic protein in spine fusion

Background contextBecause pseudarthrosis remains a clinically significant complication after spinal arthrodesis, the role of recombinant bone morphogenetic proteins (BMPs) is continually evaluated in spine surgery.PurposeThis article reviews the important literature in clinical research involving the use of BMPs in the augmentation of spinal fusion.Study design/settingReview article.MethodsA literature search was performed via MEDLINE through PubMed with the dates January 1960 to July 2007 using the keywords “bone morphogenetic protein, BMP, spinal arthrodesis, and/or bone healing.” Pertinent preclinical and clinical publications were chosen based on relevance and quality for inclusion in this study.ResultsPublications focused on the historical context and potential clinical applications using BMP were selected to delineate the risks, benefits, and current indications for the augmentation of spinal arthrodesis.ConclusionsAlthough multiple commercially available recombinant BMPs have demonstrated clinical success in interbody and posterolateral fusions, the associated costs preclude its routine use in spinal arthrodesis. The spine surgeon must assess each patient individually based on age, bone quality, diagnosis, comorbidities, and risks of nonunion to determine the cost effectiveness of the use of BMP to augment spinal fusion.     

The effect of osteogenic protein-1 in instrumented and noninstrumented posterolateral fusion in rabbits.

BACKGROUND CONTEXT: The use of rigid instrumentation combined with bone graft makes intuitive sense given the requirements for vascular ingrowth, bone formation and a stable environment for the cellular events of healing to develop. However, with the advances of potent osteoinductive growth factors, the role of internal fixation may come into question. Whether bone morphogenic proteins (BMPs) would benefit from a more "stable" spinal segment for bone production and modeling remains unknown. In addition, it is unknown whether BMP and rigid fixation may have an additive effect on fusion healing. PURPOSE: This study is proposed to test the hypothesis that rigid fixation in the lumbar spine would be advantageous to achieve fusion for autogenous bone grafting, but fusion would occur regardless of fixation with the use of osteogenic protein (OP)-1. STUDY DESIGN/SETTING: A histologic and radiographic analysis of BMP in a rabbit lumbar fusion model. METHODS: Thirty-two rabbits were randomized into four groups: 1) control animals: in situ posterolateral L5-L6 arthrodesis using autogenous iliac crest bone graft; 2) fixation group: posterolateral arthrodesis L5-L6 with autogenous bone graft and interspinous fixation; 3) OP-1 group: in situ posterolateral L5-L6 arthrodesis using OP-1 and 4) combined OP-1 and fixation group. Radiographic fusion analysis was performed with computed tomography scans at 3 and 12 weeks after surgery. Decalcified histology was performed to assess tissue morphology and cellularity. RESULTS: Minimal evidence of fusion was noted at 3 weeks with autograft or OP-1. By 12 weeks, all OP-1-treated animals had solid fusion, whereas no fusion was noted in autograft animals. The addition of fixation slightly increased radiographic fusion at 3 weeks in autograft and OP-1 groups but did not affect OP-1 animals at 12 weeks where all were fused. Decalcified histologic results confirmed the proliferative bone formation noted with OP-1 and the variable cellular response with autograft. CONCLUSIONS: The results of the present study suggest that the osteoinductive effect of OP-1 may be only minimally enhanced early in the bone healing process but does not appear to be affected in the long term by spinal fixation in the rabbit intertransverse fusion model. Fixation appeared to enhance early fusion in the autograft group.     

A preliminary comparative study of radiographic results using mineralized collagen and bone marrow aspirate versus autologous bone in the same patients undergoing posterior lumbar interbody fusion with instrumented posterolateral lumbar fusion.

BACKGROUND CONTEXT: Multiple bone graft substitutes for spinal fusion have been studied with varying results. PURPOSE: The purpose of this study was to assess the effectiveness of a mineralized collagen matrix combined with bone marrow, versus autologous bone, in the same patients undergoing a posterior lumbar interbody fusion and an instrumented posterolateral lumbar fusion. STUDY DESIGN/SETTING: A prospective, comparative study. PATIENT SAMPLE: Patients indicated for one-level posterior lumbar interbody fusion and instrumented posterolateral lumbar fusion, serving as self-controls. OUTCOME MEASURES: Thin-cut computed tomographic scans with sagittal reconstruction and plain radiographs, including lateral flexion/extension views were performed and assessed at 12 and 24 months after surgery. Oswestry Disability Index and Visual Analog Scale questionnaires were completed by all patients preoperatively and at 12 and 24 months after surgery. METHODS: After informed consent and failure of nonoperative treatment, 25 consecutive patients requiring one-level instrumented posterolateral fusion combined with posterior interbody fusion were enrolled in the study. Mineralized collagen bone graft substitute combined with bone marrow aspirate was used on one side of the posterolateral fusion, with iliac crest autograft on the contralateral side. RESULTS: A fusion rate of 84% (21/25) was achieved for the autologous bone grafts and 80% (20/25) for the bone graft substitute. The interbody fusion rate was 92% (23/25). Mean Oswestry Disability Index (ODI) scores decreased 57.2% at 12 months and 55.6% at 24 months, compared with baseline. CONCLUSIONS: Mineralized collagen bone graft substitute exhibited similar radiographic results compared with autograft in this model. Further trials incorporating bilateral fusion, as well as posterolateral fusion alone without interbody fusion are warranted to confirm the results of this study.     

What is the role of dynamic cervical spine radiographs in predicting pseudarthrosis revision following anterior cervical discectomy and fusion?

Background ContextPostoperative dynamic radiographs are used to assess fusion status after anterior cervical discectomy and fusion (ACDF) with comparable accuracy to computed tomography (CT) scans.PurposeTo (1) determine if dynamic radiographs accurately predict pseudarthrosis revision in a cohort of largely asymptomatic patients who underwent ACDF, (2) determine how adjacent segment motion is affected by fusion status, and (3) analyze how clinical outcomes differ between patients with symptomatic and asymptomatic pseudarthrosis.Study DesignRetrospective cohort study.Patient SamplePatients ≥ 18 years who underwent primary one- to four-level ACDF at a single institution over a 10-year period.Outcome MeasuresInterspinous motion on preoperative and postoperative flexion-extension radiographs and preoperative and postoperative Visual Analogue Scale for Neck Pain (VAS Neck) and Arm Pain (VAS Arm), Neck Disability Index (NDI), Modified Japanese Orthopaedic Association scale (mJOA), Mental and Physical Component Scores of the Short-Form 12 (SF-12) Health Survey (MCS-12 and PCS-12)MethodsThe difference in spinous process motion between flexion and extension radiographs was used to determine motion at each level of the ACDF construct. Pseudarthrosis was defined as ≥ 1 mm spinous process motion on dynamic radiographs. A receiver operating characteristic (ROC) curve was generated to predict the probability of surgical revision for pseudarthrosis based on millimeters of interspinous motion at each instrumented level. Patient reported outcome measures (PROMs) were used to assess the effect of pseudarthrosis on clinical outcomes. Alpha was set at p<.05.ResultsA total of 597 patients met inclusion criteria including 1,203 ACDF levels. Of those, 215 patients (36.0%) were diagnosed with a pseudarthrosis on dynamic radiographs with 29 patients (4.9%) requiring pseudarthrosis revision. ROC analysis identified a “cutoff” value of 1.00 mm of interspinous process motion for generating an optimal area under the curve (AUC). The negative predictive value (NPV) was 99.6%, whereas the positive predictive value (PPV) was 13.7%. When analyzing adjacent segment motion, the Δ supra-adjacent interspinous process motion (ISM) was significantly lower for patients with a superior construct pseudarthrosis (-1.06 mm vs. 1.80 mm, p<.001), whereas the Δ infra-adjacent level ISM was significantly lower for patients with an inferior construct pseudarthrosis (-1.21 mm vs. 2.15 mm, p<.001). Patients with a pseudarthrosis not requiring revision had worse postoperative NDI (29.3 vs. 23.4, p=.027), VAS Neck (3.40 vs. 2.63, p=.012), and VAS Arm (3.09 vs. 1.85, p=.001) scores at 3 months, but not 1-year, compared with patients who were fused. Patients requiring pseudarthrosis revision had higher 1-year postoperative NDI (38.0 vs. 23.7, p=.047) and lower 1-year postoperative Δ VAS Arm (-0.22 vs. -2.97, p=.016) scores.ConclusionsOne-year postoperative dynamic radiographs have a greater than 99% negative predictive value for identifying patients requiring pseudarthrosis revision, but they have a low positive predictive value. Most patients with a pseudarthrosis remain asymptomatic with similar 1-year postoperative patient-reported outcomes compared with patients without a pseudarthrosis.     

Osseointegration of autograft versus osteogenic protein-1 in posterolateral spinal arthrodesis: emphasis on the comparative mechanisms of bone induction.

BACKGROUND CONTEXT: Recent studies have documented increased fusion success afforded by bone morphogenetic proteins versus autogenous graft for posterolateral spinal arthrodesis. PURPOSE: The current study was designed to investigate the time-course maturation processes of lumbar posterolateral arthrodeses performed with Osteogenic Protein-1 (Stryker Biotech, Inc., Hopkinton, MA, USA) (rhOP-1) versus "gold standard" autograft. STUDY DESIGN: The primary focus of this study was to compare the histologic mechanisms of posterolateral osseointegration produced by "hot topic" growth factors. METHODS: A total of 36 coonhounds were equally divided into one of four postoperative time periods of 4, 8, 12 and 24 weeks (nine animals per period). Posterolateral arthrodesis treatments included 1) autograft alone, 2) autograft plus rhOP-1, or 3) rhOP-1 alone. The treatments and animals were divided such that a value of n=6 was obtained for each treatment group per time period and no one animal received the same treatment at both operative sites. Functional spinal unit (FSU) fusion status was assessed using radiographic analysis, biomechanical testing and undecalcified histopathologic and histomorphometric analyses. RESULTS: Radiographic differences in fusion maturation between the treatment groups were evident as early as the 4-week time interval and continued through the 24-week time period. The Osteogenic Protein-1 treatments demonstrated an accelerated rate of radiographic fusion by 4 weeks, which plateaued after the 8-week time period (22% autograft, 88% autograft/rhOP-1 and 66% rhOP-1). In contradistinction, the so-called "gold standard" autograft alone treatments reached a maximum of 50% fusion by the 6-month interval. Biomechanical testing of the FSUs indicated lower flexion-extension and axial rotation range of motion levels for both rhOP-1 treatments versus autograft alone at the 8- and 12-week time periods, respectively (p<.05). Histomorphometric analysis yielded no difference in the posterolateral trabecular bone area (mm(2)) between the three treatments (p>.05), and histopathology indicated no significant histopathologic changes. The most distinctive finding in this study deals with the mechanisms of posterolateral ossification. Based on plain and polarized light microscopy, bone induction and development for the rhOP-1 treatments, with and without autograft, was the result of intramembranous ossification, whereas the process of osseointegration for autograft alone was endochondral bone formation. By the 24-week interval, no discernable differences in trabecular histomorphology were evident based on the different mechanisms of ossification. CONCLUSIONS: This serves as the first study to document the mechanisms of bone induction and fusion maturation between posterolateral arthrodeses treated with autograft versus rhOP-1. The histological data served to corroborate the radiographic and biomechanical findings, because the rhOP-1 treatments consistently demonstrated increased fusion rates and lower range of motion levels compared with the autograft group, particularly at the 8-week postoperative time period. The improvements in these fusion criteria for Osteogenic Protein-1 versus autograft were considered secondary to the differing mechanisms of bone induction. When implanted for posterolateral arthrodesis, rhOP-1 induces an intramembranous healing response, obviating the need for the cartilage intermediate phases found in endochondral bone development. The mechanism of increased speed and incidence of fusion using growth factors (rhOP-1) is delineated by this comprehensive study of preferential intramembranous ossification.     

Considering healthcare value and associated risk factors with postoperative urinary retention after elective laminectomy

BACKGROUNDMitigating common complications such as postoperative urinary retention (POUR) following elective spine surgery is prudent. Identifying patients at risk for POUR and recognizing associated factors, to avoid a more complicated postoperative episode should be a priority and easily achievable. Understanding the financial burden of complications, such as POUR, is also important for value-based healthcare, not only for providers, but for employers and payors as well.PURPOSEThe purpose of this study is to examine patient and surgical factors that may lead to increased risk for POUR and its associated cost following elective lumbar laminectomies.STUDY DESIGN/SETTINGThis is a retrospective study of the incidence of postoperative urinary retention after elective one- and two-level primary lumbar laminectomies.PATIENT SAMPLEWe followed patients undergoing one- and two-level primary elective lumbar laminectomies performed between April 2014 and December 2016.OUTCOME MEASURESPatient factors included age, gender, body-mass index, and comorbidities. Surgical factors included surgical time, intraoperative fluid volume requirements, anesthesia type, and surgical levels involved. Other outcome variables included length of stay, discharge disposition, 30-day all-cause readmissions and emergency department visits, 90-day complications, and variable direct costs.METHODSThe incidence of POUR was evaluated and compared with patient and surgical factors and cost-specific variables to identify correlations and potential risk for POUR after one- and two-level primary lumbar laminectomies.RESULTSAnalysis included 333 patients – 203 one-level laminectomies and 130 two-level laminectomies. The overall incidence of POUR was 17.4%. Age, male gender, and history of urinary retention were significantly associated with POUR. There was a significantly increased risk of POUR with increased surgical time, but not with anesthesia type. There were also no significant differences in body-mass index, other study comorbidities, intraoperative fluid requirements, readmission, emergency department visit, and complication rates between groups. On average, patients with POUR had a significantly longer length of stay than patients without POUR. In addition, more POUR patients were discharged to acute rehabilitation facilities and had higher average variable direct cost compared tonon-POUR patients.CONCLUSIONSPOUR is a significant risk after elective laminectomy. This study supports several widely accepted beliefs regarding POUR risk, while challenging others. It also highlights the burden of POUR development after surgery. At our institution, we developed a protocol supported by these findings.     

Impact of bone morphogenetic proteins on frequency of revision surgery,use of autograft bone,and total hospital charges in surgery for lumbar degenerative disease: review of the Nationwide Inpatient Sample from 2002 to 2008

Background contextBone morphogenetic proteins (BMPs) were developed with the goal of improving clinical outcomes through the promotion of bony healing and reducing morbidity from iliac crest bone graft harvest.PurposeTo complete a population-based assessment of the impact of BMP on use of autograft, rates of operative treatment for lumbar pseudoarthrosis, and hospital charges.Study designNationwide Inpatient Sample (NIS) retrospective cohort assessment of 46,452 patients from 2002 to 2008.Patient sampleAll patients who underwent lumbar arthrodesis procedures for degenerative spinal disease.Outcome measuresUse of BMP, revision surgery status as a percentage of total procedures, and autograft harvest in lumbar fusion procedures completed for degenerative diagnoses.MethodsDemographic and geographic/practice data, hospital charges, and length of stay of all NIS patients with thoracolumbar and lumbosacral procedure codes for degenerative spinal diagnoses were recorded. Codes for autograft harvest, use of BMP, and revision surgery were included in multivariable regression analysis.ResultsThe assessment found 46,452 patients from 2002 to 2008 undergoing thoracolumbar or lumbar arthrodesis procedures for degenerative disease. Assuming a representative sample, this cohort models more than 200,000 US patients. There was steady growth in lumbar spine fusion and in the use of BMP. The use of BMP increased from 2002 to 2008 (odds ratio [OR], 1.50; 95% confidence interval [CI], 1.48–1.52). Revision procedures decreased over the study period (OR, 0.94; 95% CI, 0.91–0.96). The use of autograft decreased substantially after introduction of BMP but then returned to baseline levels; there was no net change in autograft use from 2002 to 2008. The use of BMP correlated with significant increases in hospital charges ($13,362.39; standard deviation±596.28, p<.00001). The use of BMP in degenerative thoracolumbar procedures potentially added more than $900 million to hospital charges from 2002 to 2008.ConclusionsThere was an overall decrease in rates of revision fusion procedures from 2002 to 2008. Introduction of BMP did not correlate with decrease in use of autograft bone harvest. Use of BMP correlated with substantial increase in hospital charges. The small decrease in revision surgeries recorded, combined with lack of significant change in autograft harvest rates, may question the financial justification for the use of BMP.     

复杂性腰椎管狭窄症手术方法比较

目的 评估椎板切除后外侧融合术，椎板切除椎间融合经椎弓根内固定术治疗复杂性腰椎管狭窄患者的术后近，中期疗效。方法 有21例患者接受椎板切除后外侧融合术，22例患者接受椎板切除椎间融合椎弓根内固定术，术后进行Oswestry疗效评定和腰椎影像学观察。结果 术后1年疗效优良率后外侧融合组为81.0%。椎间融合固定组为81.8%。术后1年两组疗效优良率无显著差别。术后4年疗效优良率后外侧融合组为72.2%,椎间融合组为78.9%。术后4后外侧融合组疗效下降显著，椎间融合组疗效下降不显著，结论 椎板切除椎间融合经椎弓根内固定术，椎板切除后外侧融合术治疗复杂性腰椎管狭窄症，术后近期疗效均满意，椎板切除后外侧融合组术后中期疗效下降，其腰椎不稳定和腰椎管再狭窄发生率较高。     

Circumferential and posterolateral fusion for lumbar disc disease

Clinical outcome of low back fusion is unpredictable. There are various reports discussing the merits and clinical outcome of these two procedures. The patients were selected from a population of patients who had chronic low back pain unresponsive to conservative treatment. Thirty-six instrumented posterolateral fusions and 35 instrumented circumferential fusions with posterior lumbar interbody fusions were done simultaneously. Preoperative radiographic assessment included plain radiographs, magnetic resonance imaging scans, and provocative discography in all the patients. Posterolateral fusion or anterior lumbar interbody fusion was done for internal disc disruption. The Oswestry disability index, subjective scoring, and assessment of fusion were done at a minimum followup of 2 years. On subjective scoring assessment there was a satisfactory outcome of 63.9% (23 patients) in the posterolateral fusion group and 82.8% (29 patients) in the posterior lumbar interbody fusion group. On assessment by the Oswestry index no difference was found in outcome between the two groups. The posterolateral fusion group had a 63.9% satisfactory outcome and the posterior lumbar interbody fusion group had an 80% satisfactory outcome using the Oswestry disability index for postoperative assessment. There was 61.1% improvement in working ability in the posterolateral fusion group and 77.1% improvement in the posterior lumbar interbody fusion group which was not statistically significant. The authors consider instrumented circumferential fusion with posterior lumbar interbody fusion better than instrumented posterolateral fusion for managing chronic disabling low back pain.     

The efficacy of a nanosynthetic bone graft substitute as a bone graft extender in rabbit posterolateral fusion

BACKGROUND CONTEXTSynthetic bone graft substitutes are commonly used in spinal fusion surgery. Preclinical data in a model of spinal fusion to support their efficacy is an important component in clinical adoption to understand how these materials provide a biological and mechanical role in spinal fusion.PURPOSETo evaluate the in vivo response of a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft compared to autograft alone or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft in a rabbit spinal fusion model.STUDY DESIGNEfficacy of a nanosynthetic silicated calcium phosphate putty as an extender to autograft was studied in an experimental animal model of posterolateral spinal fusion at 6, 9, 12 and 26 weeks, compared to a predicate device.METHODSSkeletally mature female New Zealand White rabbits (70) underwent single level bilateral posterolateral intertransverse process lumbar fusion, using either autograft alone (AG), a nanosynthetic silicated calcium phosphate putty (OstP) combined with autograft (1:1), or a collagen-biphasic calcium phosphate putty (MasP) combined with autograft (1:1). Iliac crest autograft was harvested for each group, and a total of 2 cc of graft material was implanted in the posterolateral gutters per side. Fusion success was assessed at all time points by manual palpation, radiographic assessment, micro-CT and at 12 weeks only using non-destructive range of motion testing. Tissue response, bone formation and graft resorption were assessed by decalcified paraffin histology and by histomorphometry of PMMA embedded sections.RESULTSAssessment of fusion by manual palpation at the 12 week endpoint showed 7 out of 8 (87.5%) bilateral fusions in the OstP extender group, 4 out of 8 (50%) fusions in the MasP extender group, and 6 out of 8 (75%) fusions in the autograft alone group. Similar trends were observed with fusion scores of radiographic and micro-CT data. Histology showed a normal healing response in all groups, and increased bone formation in the OstP extender group at all timepoints compared to the MasP extender group. New bone formed directly on the OstP granule surface within the fusion mass while this was not a feature of the Collagen-Biphasic CaP material. After 26 weeks the OstP extender group exhibited 100% fusions (5 out of 5) by all measures, whereas the MasP extender group resulted in bilateral fusions in 3 out of 5 (60%), assessed by manual palpation, and fusion of only 20 and 0% by radiograph and micro-CT scoring, respectively. Histology at 26 weeks showed consistent bridging of bone between the transverse processes in the Ost P extender group, but this was not observed in the MasP extender group.CONCLUSIONSThe nanosynthetic bone graft substituted studied here, used as an extender to autograft, showed a progression to fusion between 6 and 12 weeks that was similar to that observed with autograft alone, and showed excellent fusion outcomes, bone formation and graft resorption at 26 weeks.CLINICAL SIGNIFICANCEThis preclinical study showed that the novel nanosynthetic silicated CaP putty, when combined with autograft, achieved equivalent fusion outcomes to autograft. The development of synthetic bone grafts that demonstrate efficacy in such models can eliminate the need for excessive autograft harvest and results from this preclinical study supports their effective use in spinal fusion surgery.