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.     

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.     

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.     

Beta tricalcium phosphate: observation of use in 100 posterolateral lumbar instrumented fusions

BackgroundBeta tricalcium phosphate (B-TCP) is increasingly used to supplement lamina autograft to perform posterolateral lumbar-instrumented arthrodesis.PurposeTo determine the radiographic arthrodesis and pseudarthrosis rates after multisegment lumbar laminectomies and one- or two-segment posterolateral instrumented fusion using lamina autograft and an artificial bone graft expander B-TCP (Vitoss; Orthovita, Malvern, PA, USA).Study design/settingTo document radiographic arthrodesis/pseudarthrosis rates using lamina autograft and B-TCP.Patient sampleOne hundred patients with lumbar spinal stenosis underwent multisegment laminectomies (average 3.6 segments) and one- (78 patients) or two- (22 patients) segment posterolateral instrumented arthrodesis.Outcome measuresTwo-year postoperative outcomes were assessed using Short-Form 36 questionnaires.MethodsThe arthrodesis mass consisted of lamina autograft and B-TCP. Two independent neuroradiologists, using both dynamic X-rays and 2D-CT studies performed 3, 4.5, 6, and up to 12 months postoperatively, documented radiographic arthrodesis progression.ResultsOne-segment arthrodesis was performed in 79 patients; 74 (93.7%) were radiographically fused “early” (6.5 postoperative months), 2 (2.5%) fused “late” (6.5–12 months), and 3 (3.8%) exhibited pseudarthrosis. Two-segment arthrodesis was performed in 21 patients; 14 (66.7%) radiographically fused “early,” 5 (23.8%) fused “late,” and 2 (9.5%) exhibited pseudarthrosis. Although chi-square analyses revealed a significant increase in the number of “late” radiographic fusions occurring for patients undergoing two-level arthrodesis, no significant difference in radiographic pseudarthrosis rates was noted between the two patient populations. In both groups, Short-Form 36 questionnaires revealed nearly comparable maximal improvement on seven of eight Health Scales by the second postoperative year.ConclusionsAt 6.5 months after multisegment lumbar laminectomies with posterolateral instrumented lumbar arthrodesis using lamina autograft/B-TCP, more one-segment (93.7%) versus two-segment (66.7%) radiographic arthrodesis occurred. By 1 year after operation, there was no significant difference in fusion rates between one- and two-segment radiographic arthrodeses.     

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.     

An argument for traditional posterior cervical fusion techniques: evidence from 35 cases

BACKGROUND: For patients with adequate preservation of the cervical lordotic curvature, focal laminectomy (1-3 levels), and multilevel posterior fusion offer decompression with immediate stabilization. For lateral mass/pedicle screw techniques, CT-guided cadaveric studies document a 13.4% incidence of noncritical, and 10.6% frequency of critical pedicle breaches. Without CT guidance, fewer critical breaches (1.4%-9%) occur in patients who exhibit even fewer neurovascular injuries. Alternatively, for 35 patients undergoing focal laminectomy with posterior fusions using spinous process-based wiring techniques, no screw-related neurovascular injuries occurred, whereas 100% of patients fused. METHODS: Patients averaged 65 years of age (22 men and 13 women) and exhibited severe myelopathy (Nurick grade 4.1). Dynamic x-ray and MR/CT studies documented preserved cervical lordotic curvatures and cord compression (stenosis, OPLL, OYL, olisthy). Patients required, on average, 2 level laminectomies (range, 1-3) and 7 level posterior fusions. Fusions used spinous process-based wiring techniques with iliac autograft/bone graft expanders. One-year SF-36 and 2-year fusion (dynamic x-rays/2D-CT) rates and Odom's criteria were assessed. RESULTS: Two years postoperatively, patients exhibited mild radiculopathy (Nurick grade 0.3). Complications included 2 transient root injuries (diabetic patients), 2 wound infections, 1 wound breakdown, no cord injuries, and no mortalities. Fusion occurred in 100% of patients an average of 5.2 months postoperatively. Odom's criteria revealed 29 good/excellent and 6 fair/poor outcomes, whereas SF-36 data revealed improvement on all 8 health scales. CONCLUSIONS: Focal cervical laminectomies using multilevel posterior fusions, based on spinous process wiring techniques, resulted in high fusion rates with limited morbidity.     

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.     

Short Form-36 outcomes following focal 1- and 2-level cervical laminectomy with multilevel instrumented fusion

BACKGROUND: Multilevel laminectomy with instrumented fusion addresses diffuse dorsal cord compression with an adequately preserved cervical lordosis. However, for patients with only 1 to 2 laminar impingement, more "focal" laminectomy and fusion may suffice, the shortened laminectomy allowing for a more simple spinous process fusion skipping the 1 or 2 lamina that have been removed. METHODS: Fourteen patients presented with severe spastic myeloradiculopathy (Nurick grade IV) attributed to magnetic resonance imaging- and CT-documented 1- to 2-level laminar compression, stenosis, and ossification of the yellow ligament. Magnetic resonance images also revealed 1- to 2-level hyperintense signals within the cord at the levels of maximal compromise. Surgical procedures included 1- to 2-level laminectomies and average 6.4-level posterior fusions. Dynamic x-ray/CT studies, which were obtained 3, 6, and up to 12 months postoperatively, followed progression toward fusion. Outcomes were assessed using Nurick grades (0-V) and SF-36 questionnaires assessed preoperatively and up to 12 months postoperatively. RESULTS: Patients improved on all 8 SF-36 Health Scales within the first postoperative year. Maximal improvement was observed on 5 Health Scales within the first 6 postoperative months (physical function, mental health, vitality, general health, role physical). The preoperative average Nurick grade (3.8) improved postoperatively (0.7 at 6 months, 0.5 at 1 year). Dynamic x-ray and CT studies documented fusion for all 14 patients by the sixth postoperative month. CONCLUSIONS: One- and two-level cervical laminectomies with multilevel-instrumented fusion effectively decompressed "focal" cord compression, whereas fusion maintained the cervical lordotic curvature and provided stability to avert future disease progression.     

The influence of lumbar lordosis on spinal fusion and functional outcome after posterolateral spinal fusion with and without pedicle screw instrumentation

The aim of the current study was to examine the correlation between lumbar lordosis, spinal fusion, and functional outcome in patients suffering from severe low back pain, treated by posterolateral spinal fusion with or without pedicle screw instrumentation. One hundred thirty patients were randomly allocated to posterolateral lumbar fusion with or without Cotrel-Dubousset instrumentation. Functional outcome was assessed preoperatively, and 1 and 2 years postoperatively. Lordosis angles of the lumbar spine and fusion rates were assessed at the 1- and 2-year follow-up. No difference in lordosis angle was found between the two groups at any time. Lordosis was unchanged at 2 years compared with preoperative status in both groups. In the instrumented group, nonunion (23%) was followed by a decrease in lordosis at follow-up (p < 0.05). However, in the noninstrumented group, nonunion (14%) resulted in increased lordosis (p < 0.05). No correlation was found between functional outcome and lordosis angle. The current study showed no correlation between functional outcome and lordosis angle either before or after posterolateral spinal fusion. Use of instrumentation did not influence lumbar spinal alignment compared with noninstrumented fusions. The sagittal alignment was stable both 1 and 2 years after solid fusion. The failure mode of instrumented fusions was a reduced degree of lordosis in contrast to an increased degree of lordosis in patients with noninstrumented fusion.     

The frequency and etiology of intraoperative dural tears in 110 predominantly geriatric patients undergoing multilevel laminectomy with noninstrumented fusions

STUDY DESIGN: A retrospective analysis of the frequency and etiology of dural tears (DT), defined as an unintended incidental intraoperative durotomy, occurring in 110 predominantly geriatric patients undergoing multilevel laminectomies with noninstrumented fusions. OBJECTIVE: To document the frequency and etiology of DT occurring in these older patients. SUMMARY OF BACKGROUND DATA: The frequency and etiology of DT occurring in older patients are not well documented. METHODS: The clinical (including comorbidities), neurodiagnostic, surgical procedures, and Short-Form 36 outcomes (questionnaires administered preoperatively, and 3, 6, 12 mo postoperatively) were retrospectively analyzed for these 110 patients with/without DT. RESULTS: Intraoperative DT occurred in 10 of 110 patients. These patients were typically older (average 74 y with fistulas vs. 69 y old without fistulas), included a higher percentage of females (90% vs. 76%), and had undergone somewhat more extensive laminectomies (5.5 vs. 5.0 levels) with noninstrumented fusions (1.8 vs. 1.6 levels). Three factors seemed to contribute to DT. Marked ossification of the yellow ligament (OYL), documented in all 10 patients with DT, extended to and through the dura in 3 patients. For the 100 patients without DT, 57 exhibited moderate/hypertrophied yellow ligament and 22 showed marked OYL. Synovial cysts with marked OYL were observed in 5 of 10 patients with DT, whereas only 8 of 100 without DT had synovial cysts. Prior surgical scar, originally anticipated to be a major contributing factor to DT, was found in only 2 of 10 patients with DT (also with marked OYL) compared with 10% without DT. Short-Form 36 outcome data revealed improvement on 4 or 5 Health Scales over the first postoperative year for both populations. CONCLUSIONS: Ten of 110 patients undergoing multilevel laminectomies and noninstrumented fusions developed unintended incidental DT attributed to OYL extending to/through the dura (3 patients), postoperative scar/marked OYL (2 patients), and synovial cysts/marked OYL (5 patients).     

Results of lumbosacral distraction spondylodesis for the treatment of spondylolisthesis,failed-back syndrome,and lumbar instability

Summary Various methods of lumbosacral fusions for the treatment of degenerative spinal diseases are used clinically. Results vary greatly depending on indication, type of fusion, implants, and method of evaluation. In a retrospective clinical and radiological examination after an average follow-up time of 3.9 years this study reports on the outcome of lumbosacral distraction spondylodesis (LSDS) in a consecutive series of 147 patients being fused for the treatment of spondylolisthesis, failed-back syndrome, or lumbar instability. LSDS consists of a posterolateral fusion together with an autologous corticocancellous H-graft wedged under distraction between the spinous processes of L4 and S1. With 81.0% good and excellent results this noninstrumented fusion technique showed the best outcome in patients with spondylolisthesis, while in cases with a failed-back syndrome or lumbar instability only 62.3% excellent to satisfying outcomes were noted. The rate of pseudarthrosis was 13.6% in the whole patient group; no major complications such as nerve root damage, postoperative neurological deficits, or spinal stenosis were found.     

Dynamic anterior cervical plates for multilevel anterior corpectomy and fusion with simultaneous posterior wiring and fusion: efficacy and outcomes

STUDY DESIGN: To prospectively evaluate major complications associated with the application of dynamic ABC plates (Aesculap, Tuttlingen, Germany) to multilevel Anterior Corpectomy/Fusion (ACF) followed by posterior fusion (C2-C7 PF). OBJECTIVES: To determine whether dynamic ABC (Aesculap, Tuttlingen, Germany) plates would minimize major complications (plate/graft extrusion, pseudarthrosis) while maximizing neurological outcomes in 40 consecutive patients undergoing simultaneous multilevel ACF/PF with halo application. SETTING: USA. METHODS: Patients averaged 53 years of age and preoperatively exhibited severe myeloradiculopathy (Nurick Grade 3.9). MR/CT studies documented marked ossification of the posterior longitudinal ligament/spondylostenosis. Surgery included two to four level ACF utilizing fibula strut allograft and ABC plates. Posterior spinous process wiring/fusions utilized braided titanium cables. The average operative time was 8.9 h. Fusion was confirmed on dynamic X-rays/CTs (3-12 months postoperatively). The average follow-up interval was 2.7 years. Outcomes (3 months-2 years postoperatively) were assessed utilizing Odom's Criteria, Nurick Grades, and SF-36 questionnaires. RESULTS: Major complications included one pseudarthrosis requiring secondary PWF. Minor complications in six patients included two pulmonary emboli (PE), two tracheostomies, and five superficial wound infections. At 1 year postoperatively, marked improvement was observed in all patients utilizing Odom's criteria (38 excellent/good), Nurick Grades (mild radiculopathy 0.4), and the SF-36 (3 Health Scales; Role Physical (12.5-38.6), Bodily Pain (39.9-65.5), and Role Emotional (53.8-75.8)]. The 2-year postoperative data showed minimal additional improvement. The average time to fusion was 6.3 months. CONCLUSION: Patients undergoing multilevel ACF/PF demonstrated marked neurological improvement (SF-36), and only one of 40 developed a delayed pseudarthrosis.     

Prospective clinical outcomes of revision fusion surgery in patients with pseudarthrosis after posterior lumbar interbody fusions using stand-alone metallic cages.

BACKGROUND CONTEXT: Posterior lumbar interbody fusion (PLIF) is a popular method of arthrodesis for surgical treatment of instabilities and degenerative conditions of the spine. With the introduction of threaded titanium cage devices, surgeons began performing PLIF procedures using these cages as stand-alone devices. Complications have been reported, however, including pseudarthrosis with persistent pain. Outcomes after revision surgical treatment for these patients with failed PLIF are not known. PURPOSE: To prospectively evaluate clinical outcomes of revision fusion surgery in patients who previously underwent posterior lumbar interbody fusion with stand-alone metallic cages resulting in pseudarthrosis. STUDY DESIGN/SETTING: Prospective case series. METHODS: Nineteen patients referred to the senior author were evaluated and diagnosed with pseudoarthrosis having previously undergone a PLIF procedure with stand-alone metallic cages. History, physical exam, and imaging studies were performed preoperatively and postoperatively. All underwent revision posterolateral fusion with iliac crest graft and pedicle screw instrumentation. Patient demographics, SF-36, and Oswestry Disability Index (ODI) data were collected prior to surgery and two years postoperatively. RESULTS: Patients undergoing revision fusion surgery were found to have had extensive facetectomies and pseudarthrosis intraoperatively. Outcomes data was collected on eighteen of nineteen patients (95%). Mean clinical follow up was 3.2 years (range 2.5-3.5 years). Seventeen patients (94%) achieved a solid fusion. Improvement was noted in seven of eight SF-36 sub-categories, but was significant only in two (Physical Function and Role Emotional). There was no significant difference in ODI scores. CONCLUSIONS: Pseudarthrosis should be considered in the differential diagnosis if severe symptoms persist in patients who undergo PLIF with stand-alone metallic cages. Successful revision fusion did not always correlate with improved clinical outcomes in these challenging patients undergoing further surgery. Performing PLIF using stand-alone metallic cages, especially after total resection of the facet joints, is not advocated unless supplemental instrumentation is utilized.     

rhBMP-2 enhancement of posterolateral spinal fusion in a rabbit model in the presence of concurrently administered doxorubicin.

BACKGROUND CONTEXT: Spinal fusions can be necessary in patients undergoing chemotherapy with doxorubicin. In a previous study, doxorubicin was shown to decrease spinal fusion rates in a rabbit model of lumbar intertransverse process spinal fusion with autograft iliac crest bone. In the current study, we determine whether spinal fusion with recombinant human bone morphogenetic protein-2 (rhBMP-2) can overcome the inhibitory effect of doxorubicin in spinal fusion. PURPOSE: To determine if rhBMP-2 can overcome the inhibitory effects of doxorubicin (adriamycin) in an animal model of posterolateral spinal fusion. STUDY DESIGN/SETTING: Prospective, controlled, rabbit model of posterolateral lumbar fusion. OUTCOME MEASURES: Spine fusion was assessed by manual palpation (by observers blinded to the treatment group) at the level of arthrodesis. Fusion was graded according to a five-tiered classification (0-4). Posteroanterior radiographs of the excised spines were also graded in a blinded fashion using a six-point scoring system (0-5) devised to describe the amount of bone observed between the L5-L6 transverse processes. METHODS: Thirty-two New Zealand White rabbits underwent posterolateral fusion at L5-L6 with either autograft (iliac crest autograft bone) or rhBMP-2 (rhBMP-2/absorbable collagen sponge (0.86 mg/level). All animals received a dose of doxorubicin (2.5 mg/kg) known to inhibit spine fusion via the central vein of the ear immediately postoperatively. Five weeks postoperatively the rabbits were euthanized. Spine fusion was assessed by manual palpation, and graft quality was assessed with posteroanterior radiographs. RESULTS: Four of the 16 spines (25%) in the autograft group and 16 of the 16 spines (100%) in the rhBMP-2 group fused in the presence of doxorubicin administration (p<.05). There was significantly increased bone formation in the rhBMP-2 group (p<.05). One unilateral, subclinical wound infection was observed in each group at the time of euthanization (autograft [n=1, 6%] and rhBMP-2 [n=1, 6%]). CONCLUSIONS: We confirm that when autograft is used, doxorubicin decreases spinal fusion rate (25%) compared with historical controls (60-75%). More importantly, using rhBMP-2 overcomes the inhibitory effect of doxorubicin, resulting in 100% fusion in our animal model. This study suggests that rhBMP-2 has the potential to improve fusion rates in human patients undergoing chemotherapy with doxorubicin.     

Two-year fusion and clinical outcomes in 224 patients treated with a single-level instrumented posterolateral fusion with iliac crest bone graft

Background contextReported fusion rates for spine fusions using iliac crest bone graft (ICBG) vary between 40% and 100% because of different fusion techniques, patient comorbidity, diagnosis and assessment criteria.PurposeWe report two-year results of single-level instrumented posterolateral fusions evaluated with radiographs, fine-cut computed tomography (CT) scans with reconstructions and outcome measures.Study design/ settingRetrospective analysis of data from a prospective multicenter randomized clinical controlled trial.Patient samplePatients with various degenerative diagnoses enrolled in the control arm of a Food and Drug Administration (FDA)-regulated, multicenter trial of single-level decompression and posterolateral fusion for degenerative lumbar disease.Outcome measuresShort Form-36 (SF-36), Oswestry Disability Index (ODI), Numeric Rating Scales (0–20) for back, leg, and graft site pain, CT scans, anteroposterior and lateral flexion/extension radiographs.MethodsPatients enrolled in an FDA-regulated, multicenter trial at 29 sites with degenerative lumbar disease treated with single-level instrumented posterolateral fusion with ICBG were included in the analysis. Demographic and surgical data were collected. Clinical outcomes were followed using standard metrics. Fusion was assessed by independent radiologists at 6, 12, and 24 months postoperatively. Two fusion criteria were compared: anteroposterior and flexion/extension radiographs to assess motion and bridging bone, with CT scans as needed to confirm bridging bone; and CT scan assessment for bridging bone only.ResultsOne hundred ninety-four of 224 subjects (86.6%) completed the study. The mean operative time was 2.9 hours with a blood loss of 448.6 mL. The average graft volume was 36.3 mL. There were 21 (9.4%) wound infections, 18 (8.0%) incidental durotomies, 3 (1.3%) implant displacements, 2 (0.9%) malpositioned implants, and 17 (7.6%) graft-related complications. Twenty-seven patients (13.9%) required reoperation, the majority for nonunions. Fusion rates based on radiographs with selective CTs at 6, 12, and 24 months were 65.3%, 82.5%, and 89.3%, respectively. Fusion rates based on bridging bone on CT scans were 56.1%, 71.5%, 83.9%, respectively. Two-year improvement for all outcome measures was significant (p<.001)—ODI 25.3, SF-36 Physical Component Score (PCS) 12.2, back pain 7.9, and leg pain 7.1. Two years postoperatively, 60% of patients complained of graft site pain (mean pain score=8.5).ConclusionIn a large series of patients who had primary single-level instrumented posterolateral fusion with ICBG, evidence of bridging bone on fine-cut CT scans improved with time to 83.9% at 24 months. Significant improvement from baseline was noted in all clinical outcome measures at all time intervals with 75% achieving minimum clinically important difference (MCID) for ODI and 66% achieving MCID for SF-36 PCS.     

Posterior cervical fusion failure in three morbidly obese patients following circumferential surgery

BACKGROUND: The stability of multilevel anterior corpectomy with fusion (ACF) is often enhanced by simultaneous posterior fusion (PF) which provides a "posterior tension band." Three morbidly obese patients undergoing circumferential surgery had posterior fusions performed without autogenous iliac crest graft to avoid donor site morbidity. METHODS: Three morbidly obese patients (300-350 lbs.), averaging 48 years of age, presented with rapidly progressive moderate/severe myelopathies. Magnetic resonance imaging (MRI) and computed tomography (CT) studies demonstrated severe ventral ossification of the posterior longitudinal ligament. Two to four level plated ACFs were performed utilizing fibula strut allograft and plates. Posterior spinous process wiring/fusion from C2-T1 were completed with braided titanium cables, fibula strut allografts, Inductive Conductive Matrix (a form of demineralized bone matrix), and allograft bone to avoid iliac crest donor site morbidity in such morbidly obese patients. Halo devices were utilized until fusion was documented on postoperative X-ray and 2D-CT studies subsequently obtained 3, 6, and up to 12 months postoperatively. Patients were followed an average of 3 years. RESULTS: Postoperatively, all 3 patients demonstrated mild residual myelopathy (Nurick Grade 0-I). Nevertheless, all 3 exhibited posterior pseudarthroses accompanied by anterior strut/plate extrusion (1 patient), partial anterior graft pseudarthrosis (1 patient), and a delayed strut fracture (1 patient). The first 2 patients required secondary posterior fusions performed with autogenous iliac crest graft, while the third fused with 6 months of additional bracing. CONCLUSIONS: Following circumferential cervical procedures, posterior fusions failed in 3 morbidly obese patients where iliac crest autograft was omitted in an attempt to avoid donor site morbidity.     

Fusion assessment of posterior lumbar interbody fusion using radiolucent cages: X-ray films and helical computed tomography scans compared with surgical exploration of fusion

BACKGROUND: Plain radiographic assessment of posterolateral fusion has been reported as accurate in only two thirds of patients who were found to be healed at surgical exploration. Plain radiographic techniques for fusion assessment of interbody fusion with radiolucent cages are reported to be accurate. A helical computed tomography (CT) scan shows a high sensitivity for pseudarthrosis compared with plain radiography. PURPOSE: To determine the accuracy of fusion assessment with plain X-ray films and helical CT scans by comparison to results of surgical exploration of fusion. STUDY DESIGN/SETTING: The accuracy and interobserver agreement of plain X-ray films and thin-cut helical CT scans were compared with fusion assessment by surgical exploration in patients with posterior lumbar interbody fusion using a radiolucent carbon fiber reinforced polymer cage (CFRP) and iliac crest bone graft. PATIENT SAMPLE: A review of 90 patients who had surgical exploration of the lumbar fusion. OUTCOME MEASURES: All patients had plain X-ray films including Ferguson anteroposterior parallel to the interbody space. Fifty-four patients had thin-section helical CT scans. METHODS: Fusion assessment by exploration was compared with blinded assessment by plain X-ray films and CT scans. RESULTS: Ninety patients had surgical exploration of 172 lumbar interbody and posterolateral fusion levels. At the time of exploration, fusion was determined to be successful in 87 of 90 patients and 168 of 172 (97%) fusion levels. X-ray assessment showed healed interbody fusions in 87% and posterolateral fusion healed in 75%. CT grading of the interbody fusion found healed interbody fusion in 77%, and the posterolateral fusion was fused in 68%. Plain X-ray films and CT scans had a sensitivity of 100% for pseudarthrosis and a negative predictive value of 100% for healed fusion. Specificity was almost 90% and was not significantly different between X-ray films and CT scans. CONCLUSIONS: Fusion assessment with plain X-ray films and helical CT scans showed equal accuracy after posterior lumbar interbody fusion confirmed by surgical exploration. Our results indicate that when plain X-ray films show strong evidence of fusion or pseudarthrosis, the helical CT is unlikely to provide useful new information.     

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.     

Osteogenic protein-1 overcomes the inhibitory effect of nicotine on posterolateral lumbar fusion

STUDY DESIGN: An established rabbit posterolateral lumbar fusion model was used to evaluate the ability of osteogenic protein-1 to overcome the inhibitory effect of nicotine. OBJECTIVE: To determine whether osteogenic protein-1 should be considered as a bone graft alternative for the patient who smokes. SUMMARY OF BACKGROUND DATA: Smoking interferes with the success of posterolateral lumbar fusion. This inhibitory effect has been attributed to nicotine and confirmed in a New Zealand white rabbit model. Osteoinductive protein-1 has been shown to induce posterolateral spine fusion reliably in the rabbit model. The effectiveness with which osteogenic protein-1 induces fusion in the presence of nicotine has not been studied previously. METHODS: Single-level posterolateral intertransverse process fusions were performed at L5-L6 in 18 New Zealand white rabbits. Either autograft or osteogenic protein-1 was used as grafting material. Nicotine was administered via subcutaneous mini-osmotic pumps. The animals were killed 5 weeks after surgery, and the resulting fusion masses were studied. RESULTS: Three rabbits (17%) were excluded because of complications. By manual palpation, two of the eight nicotine-exposed autograft rabbits (25%) and all of the nicotine-exposed osteogenic protein-1 rabbits (100%) were found to be fused. These results correlated well with those obtained from biomechanical testing. Histologically, the fusion zones of the nicotine-exposed autograft rabbits were distinctly less mature than the fusion masses of the nicotine-exposed osteogenic protein-1 rabbits. CONCLUSION: Osteoinductive protein-1 was able to overcome the inhibitory effects of nicotine in a rabbit posterolateral spine fusion model, and to induce bony fusion reliably at 5 weeks.     

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.