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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

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.     

Posterolateral lumbar fusions in athymic rats: characterization of a model.

BACKGROUND CONTEXT: The athymic rat has been used to study the role of osteoinductive products in spinal fusions. This small animal model has been advocated to minimize potential inflammatory responses to allogeneic or xenogenic proteins. Despite past experience, this model has not yet been well characterized. PURPOSE: To further define and validate a posterolateral lumbar fusion model in the athymic rat. STUDY DESIGN/SETTING: Comparison of fusions after animal survival surgery. PATIENT SAMPLE: Forty athymic and 20 normothymic rats. OUTCOME MEASURES: Manual palpation, radiography and histology at 3 and 6 weeks. METHODS: Single-level intertransverse fusions were performed at the L4-L5 level of 40 athymic rats. Twenty rats were implanted with autograft (athymic/autograft), and 20 had no graft placed (athymic/no graft). An additional 20 autograft fusions were performed on normothymic rats (normothymic/autograft). Half were sacrificed at 3 weeks; half were sacrificed at 6 weeks. RESULTS: At 3 weeks, 0% of the athymic/no graft rats fused, 20% of the athymic/autograft rats fused and 20% of the normothymic/autograft rats fused by manual palpation. At 6 weeks, 0% of the athymic/no graft rats fused, 30% of the athymic/autograft rats fused and 40% of the normothymic/autograft rats fused by manual palpation. Radiographs were of limited utility in determining fusion, and histology results were roughly concordant with those of manual palpation. CONCLUSIONS: This work further characterizes the athymic rat posterolateral lumbar fusion model. The absence of a thymus does not appear to affect autograft fusion rates, and no spontaneous fusions were seen when no graft was placed.     

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 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.     

Roentgenographic and biomechanical analysis of lumbar fusions: a canine model

An animal model of anterior and posterior column instability was developed to allow in vivo observation of bone remodeling and arthrodesis after spinal instrumentation. Various combinations of spinal fusions and instrumentation procedures were performed after an initial anterior and posterior destabilizing lesion was created at the L5-L6 vertebral levels in 35 adult beagles. After 6 months of postoperative observation, there was improved probability of achieving a spinal fusion if spinal instrumentation had been used. All biomechanical testing was performed after removal of instrumentation to test the inherent stiffnesses and quality of the spinal fusions. The fusions performed in conjunction with instrumentation (group V = Harrington instrumentation and posterolateral fusion; group VI = Luque instrumentation and posterolateral fusion) demonstrated the greatest axial rotation stiffnesses (group V, p less than .05); axial compressive stiffness (group V, p less than .05); and flexural stiffness (group VI, p less than .05). The results show that a spinal fusion can be more reliably achieved and will be more rigid if it is accompanied by spinal instrumentation.     

Potential significance of facet joint fusion or posteromedial fusion observed on CT imaging following attempted posterolateral or posterior interbody fusion

BACKGROUND CONTEXTRadiologic evidence of successful lumbar fusion has traditionally been based on bridging bone spanning the intertransverse processes (posterolateral fusion or PLF) or disc space (interbody fusion, or IBF). Often, postoperative computed tomography (CT) of unsuccessful PLF and IBF demonstrates bridging bone across the facet joints or connecting the medial transverse process to the ipsilateral superior articular facet of the caudal vertebra. The significance of this finding in terms of implant stability and clinical outcomes has not previously been reported.PURPOSETo determine rates of facet joint fusion (FJF)/posteromedial fusion (PMF) following single-level PLF surgery, with or without interbody. A secondary goal was to determine comparative outcomes associated with isolated FJF/PMF versus PLF and IBF.STUDY DESIGNRetrospective CT-based review.PATIENT SAMPLETwo hundred-three patients underwent single-level PLF surgery with local autograft bone or PLF+IBF with local autograft bone.OUTCOME MEASURESFusion was assessed at 6-months and 12-months postoperatively using strict CT criteria. Patient reported outcome measures included visual analogue scale (VAS) scores for back pain and leg pain, Oswestry Disability Index (ODI), and SF-36.METHODSThin-cut CTs were examined to determine whether successful fusion had occurred in seven different anatomic locations. One-way analysis of variance was used to determine significant differences in mean outcome scores and other continuous measures between groups at baseline and follow-up. Chi-square test of independence or Fisher's exact test was used to compare proportions between groups on categorical measures.RESULTSTwo hundred-three patients and 157 patients completed 6- and 12 month follow-up, respectively. At 12 months, 35.1% of PLF patients demonstrated successful unilateral/bilateral PLF. Including unilateral or bilateral FJF/PMF, the fusion rate was 73.4%. Among PLF+IBF patients, 38.1% demonstrated successful IBF/PLF. Including unilateral or bilateral FJF/PMF, the fusion rate was 55.6%. All fusion groups demonstrated significant improvement in back pain and leg pain scores as well as ODI and SF-36 PF at 6- and 12 months compared with pre-op. No significant difference in any outcome measure, rates of implant loosening or reoperation was observed between successful PLF/IBF and FJF/PMF groups.CONCLUSIONSFJF/PMF is often observed on postoperative CT evaluation following surgery originally performed to achieve PLF or IBF. Short-term follow-up suggests no significant difference in implant loosening rates or patient reported outcomes when FJF/PMF is observed versus PLF or IBF in such patients. Long-term clinical outcomes of FJF/PMF versus PLF or IBF remain unknown. These findings apply solely to single-level instrumented spinal fusion surgery utilizing pedicle screws with or without IBF.     

Elective shoulder arthroplasty in patients older than ninety years of age

This study examined the outcome of elective shoulder arthroplasty for glenohumeral osteoarthritis or rotator cuff arthropathy in patients aged older than 90 years. The study included 7 shoulders in 6 patients with an average age of 93 years 5 months, (range, 91 years 0 months to 97 years 4 months). Average follow-up was 2.2 years, (range, 1-4 years). Preoperative range of motion, Simple Shoulder Test (SST) scores, and Medical Outcomes Study Short-Form 36-Item Health Survey (SF-36) scores were obtained and compared with postoperative values at 3 and 6 months and yearly thereafter. Average forward elevation improved from 87 degrees to 137 degrees (P < .00001), and external rotation to the side improved from 0 degrees to 50 degrees (P < .0001). The SST scores improved from a preoperative average of 2.0 to 6.1 at 3 months (P < .0001), 6.9 at 6 months (P < .0001), 8.0 at 1 year (P < .00001), and 7.4 at 2 years (P < .0001). Significant improvements occurred in 6 of 8 SF-36 domains: Mental Health (P < .05), Vitality (P < .01), Role limitations due to emotional problems (P < .05), Social Function (P < .001), Role limitations due to physical health (P < .001), and Comfort (P < .00001). No patient had worse pain or function postoperatively. These data suggest that elective shoulder arthroplasty can be performed in patients 90 years of age and older, providing excellent pain relief, improved functional outcome, and enhanced general health status.     

Erythropoietin augments bone formation in a rabbit posterolateral spinal fusion model

We tested the hypothesis that erythropoietin (EPO) enhances bone formation after posterolateral spinal fusion (PLF) in a rabbit model. Thirty-four adult rabbits underwent posterolateral intertransverse arthrodesis at the L5-L6 level using 2.0 g autograft per side. The animals were randomly divided into two groups receiving subcutaneous daily injections of either EPO or saline for 20 days. Treatment commenced 2 days preoperatively. Hemoglobin was monitored at baseline and 2, 4, and 6 weeks after fusion surgery. After euthanasia 6 weeks postoperatively, manual palpation, radiographic, and histomorphometric examinations were performed. Bone volume of the fusion mass was estimated by CT after 6 weeks. EPO increased bone fusion volume to 3.85 ccm (3.66-4.05) compared with 3.26 ccm (2.97-3.55) in the control group (p<0.01). EPO treatment improved vascularization of the fusion mass and increased hemoglobin levels (p<0.01). Fusion rate tended to be higher in the EPO group based on manual palpation, CT, and radiographic examinations. For the first time EPO has shown to augment bone formation after autograft PLF in a rabbit model. Increased vascularization provides a partial explanation for the efficacy of EPO as a bone autograft enhancer.     

Comparison of the responsiveness of the SF-36 and WOMAC in patients undergoing total hip arthroplasty

This study examines the responsiveness of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and Short Form-36 (SF-36) in patients undergoing total hip arthroplasty. Eighty-nine patients completed the WOMAC and SF-36 preoperatively and postoperatively. Standardized response means (SRMs) and effect sizes (ES) were used to measure responsiveness. Mean follow-up was 17 months. The SRMs for the WOMAC ranged from -0.93 to -1.49, and the ES ranged from -1.02 to -1.53. The SRMs for the SF-36 ranged from 0.22 to 1.64, and the ES ranged from 0.20 to 1.97. The highest values occurred with the physical functioning, bodily pain, and Physical Component Summary Scales. This study demonstrates a similar level of responsiveness of the WOMAC and several components of the SF-36. This suggests that the isolated use of the SF-36 may be adequate to monitor outcomes after total hip arthroplasty. There may still be a role for the WOMAC when comparing outcomes of specific designs or techniques of total hip arthroplasty.