Posterolateral Lumbar Spine Research Articles

How I do it. Posterolateral lumbar spine fixation and decompression with navigation interfaced with a robotic exoscope with head mounted display.

Lumbar spine fixation and fusion is currently performed with intraoperative tools such as intraoperative CT scan integrated to navigation system to provide accurate and safe positioning of the screws. The use of microscopic visualization systems enhances visualization and accuracy during decompression of the spinal canal as well. We introduce a novel setting in microsurgical decompression and fusion of lumbar spine using an exoscope with robotized arm (RoboticScope) interfaced with navigation and head mounted displays. Spinal canal decompression and fusion can effectively be performed with RoboticScope, with significant advantages especially regarding ergonomics.

EVALUATION OF A CALCIUM PHOSPHATE-COLLAGEN MATRIX BONE GRAFT WITH NEEDLE-SHAPED SUBMICRON SURFACE TOPOGRAPHY IN A CLINICALLY RELEVANT SHEEP POSTEROLATERAL LUMBAR SPINE FUSION MODEL

Biphasic calcium phosphate (BCP) with a characteristic needle-shaped submicron surface topography (MagnetOs) has attracted much attention due to its unique bone-forming ability which is essential for repairing critical-size bone defects such as those found in the posterolateral spine. Previous in vitro and ex-vivo data performed by van Dijk LA and Yuan H demonstrated that these specific surface characteristics drive a favorable response from the innate immune system.This study aimed to evaluate and compare the in vivo performance of three commercially-available synthetic bone grafts, (1) i-FACTOR Putty®, (2) OssDsign® Catalyst Putty and (3) FIBERGRAFT® BG Matrix, with that of a novel synthetic bone graft in a clinically-relevant instrumented sheep posterolateral lumbar spine fusion (PLF) model. The novel synthetic bone graft comprised of BCP granules with a needle-shaped submicron surface topography (MagnetOs) embedded in a highly porous and fibrillar collagen matrix (MagnetOs Flex Matrix).Four synthetic bone grafts were implanted as standalone in an instrumented sheep PLF model for 12 weeks (n=3 bilateral levels per group; levels L2/3 & L4/5), after which spinal fusion was determined by manual palpation, radiograph and µCT imaging (based on the Lenke scale), range-of-motion mechanical testing, and histological and histomorphological evaluation.Radiographic fusion assessment determined bilateral robust bone bridging (Lenke scale A) in 3/3 levels for MagnetOs Flex Matrix compared to 1/3 for all other groups. For µCT, bilateral fusion (Lenke scale A) was found in 2/3 levels for MagnetOs Flex Matrix, compared to 0/3 for i-FACTOR Putty®, 1/3 for OssDsign® Catalyst Putty and 0/3 for FIBERGRAFT® BG Matrix. Fusion assessment for MagnetOs Flex Matrix was further substantiated by histology which revealed significant graft resorption complemented by abundant bone tissue and continuous bony bridging between vertebral transverse processes resulting in bilateral spinal fusion in 3/3 implants.These results show that MagnetOs Flex Matrix achieved better fusion rates compared to three commercially-available synthetic bone grafts when used as a standalone in a clinically-relevant instrumented sheep PLF model.

Rates and risk factors associated with 30- and 90-day readmissions and reoperations after spinal fusions for adult lumbar degenerative pathology and spinal deformity.

Analyze state databases to determine variables associated with of short-term readmissions and reoperations following thoracolumbar spine fusions for degenerative pathology and spinal deformity. Retrospective study of State Inpatient Database (2005-13, CA, NE, NY, FL, NC, UT). age > 45years, diagnosis of degenerative spinal deformity, ≥ 3 level posterolateral lumbar spine fusion. revision surgery, cervical fusions, trauma, and cancer. Univariate and step-wise multivariate logistic regression analyses were performed to identify independent variables associated with of 30- and 90-day readmissions and reoperations. 12,641 patients were included. All-cause 30- and 90-day readmission rates were 14.6% and 21.1%, respectively. 90-day readmissions were associated with: age > 80 (OR: 1.42), 8 + level fusions (OR: 1.19), hospital length of stay (LOS) > 7days (OR: 1.43), obesity (OR: 1.29), morbid obesity (OR: 1.66), academic hospital (OR: 1.13), cancer history (OR:1.21), drug abuse (OR: 1.31), increased Charlson Comorbidity index (OR: 1.12), and depression (OR: 1.20). Private insurance (OR: 0.64) and lumbar-only fusions (OR: 0.87) were not associated with 90-day readmissions. All-cause 30- and 90-day reoperation rates were 1.8% and 4.2%, respectively. Variables associated with 90-day reoperations were 8 + level fusions (OR: 1.28), LOS > 7days (OR: 1.43), drug abuse (OR: 1.68), osteoporosis (OR: 1.26), and depression (OR: 1.23). Circumferential fusion (OR: 0.58) and lumbar-only fusions (OR: 0.68) were not associated with 90-day reoperations. 30- and 90-day readmission and reoperation rates in thoracolumbar fusions for adult degenerative pathology and spinal deformity may have been underreported in previously published smaller studies. Identification of modifiable risk factors is important for improving quality of care through preoperative optimization.

Instrumented Versus Noninstrumented Spinal Fusion for Degenerative Lumbar Spondylolisthesis: A Systematic Review.

Systematic review. This systematic review compares radiographic and clinical outcomes between instrumented and noninstrumented posterolateral lumbar spine fusions for the treatment of degenerative lumbar spondylolisthesis. The optimal method of fusion for instability from degenerative lumbar spondylolisthesis remains to be an area of debate amongst spine surgeons. There are no prior comprehensive systematic review of comparative studies that compares outcomes between instrumented and noninstrumented posterolateral spine fusions for the treatment of degenerative lumbar spondylolisthesis. A systematic review was registered with PROSPERO and performed according to Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) guidelines using the PubMed, SCOPUS, and Ovid MEDLINE databases. All level I-III comparative studies published in the English language investigating the clinical outcomes between instrumented and noninstrumented posterolateral spine fusions for the treatment of degenerative lumbar spondylolisthesis were included. Seven studies (672 patients, 274 noninstrumented, 398 instrumented) were analyzed. One randomized study was level I evidence, 2 randomized studies were level II, and 4 nonrandomized studies were level III. Mean follow-up ranged from 1.4 to 5.9 years. Instrumented patients had a higher rate of solid fusion (87.6% vs. 77.1%, P=0.023) and a lower rate of definitive pseudarthrosis (5.3% vs. 19.9%, P<0.001). However, there was no difference in overall functional improvement at final follow-up between the 2 treatment groups (75.0% vs. 81.7%, P=0.258). In addition, there was no difference in reoperation or complication rates. For the treatment of degenerative lumbar spondylolisthesis, there are significantly higher rates of fusion among patients undergoing instrumented posterolateral fusion compared with noninstrumented posterolateral fusion. However, there is no difference in overall functional improvement, pain-related outcome scores, reoperation rates, or complication rates between the 2 treatment groups. Level III-systematic review of level I-III studies.

P1. Efficacy of a calcium phosphate collagen matrix bone graft with needle-shaped submicron surface topography in a rabbit posterolateral lumbar spine fusion model

<h3>BACKGROUND CONTEXT</h3> Synthetic bone grafts are a promising alternative for the treatment of degenerative spine conditions and are available without the added drawbacks associated autografts including limited availability and donor-site morbidity. Of these synthetic materials, calcium phosphate (CaP) with a characteristic needle-shaped submicron surface topography (BCP<µm) has attracted much attention due to its unique bone-forming ability which is essential for repairing critical-size bone defects such as those found in the posterolateral spine [1,2]. Previous in vitro and ex-vivo data presented by van Dijk LA [3] and Yuan H [4] at NASS, 2020 demonstrated that these specific surface characteristics drive a favorable response from the innate immune system. <h3>PURPOSE</h3> This study was to evaluate the efficacy of a novel synthetic bone graft using a clinically-relevant "Boden" rabbit posterolateral spine fusion model. The synthetic bone graft comprised of CaP granules with a needle-shaped submicron surface structure (BCP<µm) embedded in a highly porous and fibrillar bovine type I collagen matrix (col-BCP<µm). The fibrillar collagen was introduced as a carrier, designed to facilitate admixing of the graft with biological fluids perioperatively and to minimize graft migration postoperatively. <h3>STUDY DESIGN/SETTING</h3> The novel synthetic bone graft was first mixed in a 1:1 volume ratio with autologous bone (ABG). Subsequently, grafts were implanted in the rabbit posterolateral spine environment for 3 days, 6, 9 and 12 weeks. An autologous bone graft group was used as a positive control in this study. Outcomes for the test article were additionally compared to historical data for the same material (BCP<µm) implanted alone, without the fibrillar collagen carrier. <h3>OUTCOME MEASURES</h3> Spinal fusion was determined by manual palpation (MP), X-ray and µCT imaging (based on the Lenke scale), mechanical testing (range of motion testing at 12 weeks only) and histology (decalcified and undecalcified). <h3>METHODS</h3> Forty skeletally mature New Zealand white rabbits were divided into two groups and underwent single-level bilateral posterolateral intertransverse process spine arthrodesis at L4-5. Animals were euthanized after 3 days, 6, 9 and 12 weeks. <h3>RESULTS</h3> Based on all endpoints, the test group and positive control group showed an equivalent and gradual progression in bone formation and implant resorption over time, leading to mature fusion masses at 12 weeks. No adverse reactions were observed in any of the groups. Bilateral fusion rates by MP were consistent with the literature (0-40% at 6 weeks; 60-70% at 12 weeks) and similar trends were seen by histological and radiographic assessment (both X-ray and µCT). Flexion-extension and lateral bending results at 12 weeks demonstrated fusion of the treated level consistent with the MP results. The results observed for the test group were consistent with those seen historically for the same material implanted without the fibrillar collagen carrier. <h3>CONCLUSIONS</h3> These results show that BCP with needle-shaped submicron-scale surface topography (BCP<µm) combined with a fibrillar collagen matrix (col-BCP<µm) could achieve equivalent fusion rates to ABG when used as a bone graft extender in a clinically relevant single level rabbit intertransverse process posterolateral lumbar fusion model. Over time, a progression in bone healing, graft resorption and remodeling were seen with all experimental endpoints, with equivalency between the groups. The results for col-BCP<µm were consistent with those previously seen for BCP<µm alone, confirming that the fibrillar collagen carrier improved handling properties but was not detrimental to the bone-forming capacity of the BCP<µm. <h3>FDA DEVICE/DRUG STATUS</h3> Col-BCP<µm (Investigational/Not approved)

The temporal and spatial expression of sclerostin and Wnt signaling factors during the maturation of posterolateral lumbar spine fusions.

The bone healing environment in the posterolateral spine following arthrodesis surgery is one of the most challenging in all of orthopedics and our understanding of the molecular signaling pathways mediating osteogenesis during spinal fusion is limited. In this study, the spatial and temporal expression pattern of Wnt signaling factors and inhibitors during spinal fusion was assessed for the first time. Bilateral posterolateral spine arthrodesis with autologous iliac crest bone graft was performed on 21 New Zealand White rabbits. At 1‐, 2‐, 3‐, 4‐, and 6‐weeks, the expression of sclerostin and a variety of canonical and noncanonical Wnts signaling factors was measured by qRT‐PCR from tissue separately collected from the transverse processes, the Outer and Inner Zones of the fusion mass, and the adjancent paraspinal muscle. Immunohistochemistry for sclerostin protein was also performed. Sclerostin and many Wnt factors, especially Wnt3a and Wnt5a, were found to have distinct spatial and temporal expression patterns. For example, harvesting ICBG caused a significant increase in sclerostin expression. Furthermore, the paraspinal muscle immediately adjacent to the transplanted ICBG also had significant increases in sclerostin expression at 3 weeks, suggesting new potential mechanisms for pseudarthroses following spinal arthrodesis. The presented work is the first description of the spatial and temporal expression of sclerostin and Wnt signaling factors in the developing spine fusion, filling an important knowledge gap in the basic biology of spinal fusion and potentially aiding in the development of novel biologics to increase spinal fusion rates.

Comparison of Fusion Rate between Demineralized Bone Matrix versus Autograft in Lumbar Fusion : Meta-Analysis

The demineralized bone matrix (DBM) as the bone graft material to increase the fusion rate was widely used in spinal fusion. The current study aimed to compare the fusion rate of DBM to the fusion rate of autograft in lumbar spine fusion via meta-analysis of published literature. After systematic search, comparative studies were selected according to eligibility criteria. Checklist (risk of bias assessment tool for non-randomized study) was used to evaluate the risk of bias of the included nonrandomized controlled studies. The corresponding 95% confidence interval (95% CI) were calculated. We also used subgroup analysis to analyze the fusion rate of posterolateral lumbar fusion and lumbar interbody fusion. Eight studies were finally included in this meta-analysis. These eight studies included 581 patients. Among them, 337 patients underwent spinal fusion surgery using DBM (DBM group) and 204 patients underwent spinal fusion surgery with mainly autologous bone and without using DBM (control group). There was no significant differences of fusion rate between the two groups in posterolateral fusion analysis (risk ratio [RR], 1.03; 95% CI, 0.90–1.17; p=0.66) and interbody fusion analysis (RR, 1.13; 95% CI, 0.91–1.39; p=0.27). Based on the available evidence, the use of DBM with autograft in posterolateral lumbar spine fusion and lumbar interbody fusion showed a slightly higher fusion rate than that of autograft alone; however, there was no statistically different between two groups.

Posterolateral lumbar spine fusion with unidirectional porous beta-tricalcium phosphate in a canine model

We investigated the use of the autologous iliac bone and unidirectional porous beta-tricalcium phosphate (UDPTCP) in posterolateral lumbar spine fusion (PLF). Ten canine PLF models were prepared. Using only the autologous bone as the control group, 100%, 75%, 50%, and 25% groups were prepared according to the mixing ratios of UDPTCP. Radiological evaluation and histological analysis were performed 12weeks after surgery. Bone fusion was evaluated according to anteroposterior plain X-rays and coronal reconstruction CT views using four grades: 0 = no osteogenesis, 1 = only slight discontinuous osteogenesis between transverse processes, 2 = discontinuous osteogenesis between transverse processes, and 3 = continuous osteogenesis between transverse processes. Bone fusion determined by X-ray was 2.8 ± 0.5 in the control group, 0 in the 100% UDPTCP group (p = 0.02), 1.8 ± 0.5 (p = 0.03) in the 75% UDPTCP group, 2.5 ± 0.6 (p = 0.54) in the 50% UDPTCP group, and 2.8 ± 0.5 (p = 1.0) in the 25% UDPTCP group. The bone fusion score was significantly lower in the 75% and 100% UDPTCP groups than in the control group. Bone fusion determined by CT was 2.8 ± 0.5 in the control group, 1.0 ± 0.8 (p = 0.01) in the 100% UDPTCP group, 2.0 ± 0.0 (p = 0.02) in the 75% UDPTCP group, 2.5 ± 0.6 (p = 0.54) in the 50% UDPTCP group, and 2.8 ± 0.5 (p = 1.0) in the 25% UDPTCP group. Similar to the bone fusion determination by X-ray, the bone fusion score was significantly lower in the 75% and 100% UDPTCP groups. These data suggest that, in a canine PLF model, the appropriate mixing ratio of UDPTCP is 50% or less.

Autologous blood coagulum is a physiological carrier for BMP6 to induce new bone formation and promote posterolateral lumbar spine fusion in rabbits.

In the present study, we describe autologous blood coagulum (ABC) as a physiological carrier for BMP6 to induce new bone formation. Recombinant human BMP6 (rhBMP6), dispersed within ABC and formed as an autologous bone graft substitute (ABGS), was evaluated either with or without allograft bone particles (ALLO) in rat subcutaneous implants and in a posterolateral lumbar fusion (PLF) model in rabbits. ABGS induced endochondral bone differentiation in rat subcutaneous implants. Coating ALLO by ABC significantly decreased the formation of multinucleated foreign body giant cells (FBGCs) in implants, as compared with ALLO alone. However, addition of rhBMP6 to ABC/ALLO induced a robust endochondral bone formation with little or no FBGCs in the implant. In rabbit PLF model, ABGS induced new bone formation uniformly within the implant resulting in a complete fusion when placed between two lumbar transverse processes in the posterolateral gutter with an optimum dose of 100‐μg rhBMP6 per ml of ABC. ABGS containing ALLO also resulted in a fusion where the ALLO was replaced by the newly formed bone via creeping substitution. Our findings demonstrate for the first time that rhBMP6, with ABC as a carrier, induced a robust bone formation with a complete spinal fusion in a rabbit PLF model. RhBMP6 was effective at low doses with ABC serving as a physiological substratum providing a permissive environment by protecting against foreign body reaction elicited by ALLO.

P4. Autologous blood coagulum as a native carrier for rhBMP6 induces new bone formation and posterolateral lumbar spine fusion in rabbits and sheep

BACKGROUND CONTEXT RhBMP2 soaked in bovine tendon collagen and synthetic ceramics composite as well as rhBMP7/OP1 lyophilized in bovine bone collagen particles with additive carboxyl-methyl cellulose have been evaluated for posterolateral lumbar fusion (PLF). We investigated rhBMP6 delivered in autologous blood coagulum (ABC), a native carrier (scaffold), with and without allograft bone particles (ALLO) to induce new bone formation and promote posterolateral lumbar spine fusion (PLF) in rabbit and sheep. PURPOSE To evaluate the efficacy of RhBMP6 with autologous blood coagulum (ABC) alone or with ABC and allograft (ALLO) will induce a successful posterolateral spinal fusion in animal models. STUDY DESIGN/SETTING Preclinical evaluation of spine fusion in animal models. PATIENT SAMPLE Multiple experimental groups of rats, rabbits and sheep. OUTCOME MEASURES Radiographic and histologic evaluation for bone formation and spinal fusion. METHODS An autologous bone graft substitute (ABGS) was fabricated by dispersing rhBMP6 in ABC with and without ALLO and evaluated for bone induction in rat subcutaneous implants and to promote bone formation in posterolateral lumbar fusion in preclinical models. The cellular response of bone induction and the quantity and quality of newly formed bone were examined by histology, radiographs, micro-CT analyses at various time intervals. RESULTS ABGS with and without ALLO induced new bone formation in rat implants. ALLO alone induced formation of multinucleated foreign body giant cells (FBGCs). However, ALLO plus ABC decreased the formation of FBGCs. The addition of rhBMP6 to ABC/ALLO, resulted in fewer or no FBGCs. In Rabbits, the groups with ABC alone or with ALLO did not fuse. The 50 micrograms rhBMP6 group only 2 out of 4 animals successfully fused. In the 100 micrograms, 200 micrograms and 400 micrograms rhBMP6 groups all animals successfully fused. In sheep, the groups with ABC or ABC with ALLO failed to fuse. In the rhBMP6 187.5 micro grams/ml group with ABC and instrumentation fusion was achieved in 83% (10/12 animals). In the 187.5 micro grams/ml group with ABC, ALLO and instrumentation, fusion was achieved in 93% (11/12 animals). Bone formation occurred uniformly within ABGS implants where the ALLO was replaced by the newly formed bone via creeping substitution. CONCLUSIONS RhBMP6 with autologous blood coagulum (ABC) alone or with ABC and allograft (ALLO) induced a robust bone formation in posterolateral spinal fusion in preclinical models. FDA DEVICE/DRUG STATUS RhBMP6 (Not approved for this indication).

110. Use of a novel allograft in single-level posterolateral lumbar spine fusion surgery: 1-year clinical and radiographic results from a prospective multicenter study with comparison to reported results for ICBG

BACKGROUND CONTEXT Instrumented posterolateral lumbar fusion (PLF) surgery is commonly used to alleviate pain and other symptoms associated with degenerative conditions of the lumbosacral spine. Although autologous iliac crest bone graft (ICBG) remains the “gold standard” grafting material for these procedures, surgeons have sought alternatives to avoid the potential morbidity associated with ICBG harvest. OSTEOAMP is a novel allograft bone graft substitute (BGS) that has been processed to retain multiple endogenous growth factors. A prospective multicenter study was designed to enable comparison of this novel product to available data for autologous bone graft controls from large randomized controlled trials (RCTs). PURPOSE Compare 1-year outcomes from an ongoing study investigating radiographic and clinical outcomes to reported results for ICBG controls from a large RCT. STUDY DESIGN/SETTING Prospective multicenter single-arm study conducted in the United States. PATIENT SAMPLE Consenting patients, 21 to 85 years of age, scheduled for PLF surgery with a diagnosis of degenerative disc disease (DDD), degenerative spondylolisthesis, and/or mild degenerative scoliosis. OUTCOME MEASURES Bilateral radiographic fusion (blinded, multireader with adjudication) was assessed. Additional outcome measures included Oswestry Disability Index (ODI), Short Form-36 (SF-36) physical component summary (PCS) and mental component summary (MCS) scores, and improvement in leg/back pain scores. Product-related serious adverse events (SAEs) and secondary surgeries were also assessed. METHODS Forty-two patients were prospectively enrolled after obtaining IRB approval at each of 9 centers and underwent a 1-level (26 patients) or 2-level (16 patients) PLF procedure utilizing the novel BGS (67% BGS: 33% local bone graft). Clinical outcomes were measured and radiographic studies were obtained preop and postop at 1.5, 3, 6, and 12 months. Radiographic analysis included CT assessment of fusion at 12 months. One-year outcomes were available for 23 of the 26 patients who underwent a 1-level procedure and were compared to 1-year outcomes reported for ICBG controls from a large previously published RCT by estimation of novel BGS:ICBG Risk Ratios (RR) with 95% confidence intervals (CI). RESULTS One-year fusion rates and results for each of the measures (novel BGS vs ICBG) are as follows: bilateral fusion = 73.9% (17/23) vs 82.5% (151/183) with RR 0.90 (0.69, 1.15 CI); ODI (>15 improvement) = 73.9% (17/23) vs 73.9% (150/203), RR 1.00 (0.77, 1.29 CI); leg pain = 95.7% (22/23) vs 87.6% (177/202), RR 1.09 (0.99, 1.21 CI); back pain = 91.3% (21/23) vs 93.1% (180/203), RR 0.98 (0.86, 1.12 CI); SF-36 MCS = 73.9% (17/23) vs 68.7% (138/201), RR 1.08 (0.83, 1.40); SF-36 PCS = 95.7% (22/23) vs 86.6% (174/201), RR 1.10 (1.00, 1.22 CI). No statistically significant difference was found in RR between groups for all comparisons. No product-related SAEs and only one secondary surgery were observed with the novel BGS. CONCLUSIONS One-year clinical and radiographic outcomes following single-level PLF procedures with OSTEOAMP compare favorably to results reported for an ICBG control group from a large RCT. FDA DEVICE/DRUG STATUS OSTEOAMP (Approved for this indication)

Surgical Infection after Posterolateral Lumbar Spine Arthrodesis: CT Analysis of Spinal Fusion.

To determine the incidence of infection after instrumented lumbar spine surgery, the demographic and surgical variables associated with acute infection, and the influence of infection and debridement on the consolidation of spinal fusion. After obtaining approval from the hospital ethics committee, an observational study was made on a prospective cohort of consecutive patients surgically treated by posterolateral lumbar spine arthrodesis (n = 139, 2005-2011). In all cases, the minimum follow-up period was 18 months. The following bivariate analysis was conducted of demographic and surgical variables: non-infection group (n = 123); infection group (n = 16). Fusion rates were determined by multislice CT. Logistic regression analysis was performed. Incidence of deep infection requiring debridement: 11.51% (95% confidence interval, 5.85-17.18]). Bivariate analysis: differences were observed in hospital stay (7.0 days [range, 4-10] vs 14.50 days [range, 5.25-33.75]; P = 0.013), surgical time (3.15 h vs 4.09 h; P = 0.004), body mass index (25.11 kg/m2 [22.58-27.0] vs 26.02 kg/m2 [24.15 to 29.38]; P = 0.043), Charlson comorbidity index (median, 0 vs 1; P = 0.027), and rate of unsuccessful consolidation according to CT (18.4% vs 72.7%; P = 0.0001). In a model of multivariate logistic regression, taking as the dependent variable unsuccessful arthrodesis after 1 year, and adjusting for the other independent variables (infection, body mass index, Charlson comorbidity index, and surgical time), the only variable that was significantly associated with an outcome of unsuccessful spinal fusion after 1 year was infection, with OR = 12.44 (95% confidence interval, 2.50-61.76). Deep infection after instrumented lumbar spine arthrodesis is a common complication that compromises the radiographic outcome of surgery. Patients who develop a postoperative infection and require debridement surgery are 12 times less likely to achieve satisfactory radiological fusion.

Bone graft materials for posterolateral fusion made simple: a systematic review.

Iliac crest has long been the gold standard for lumbar fusion, but concerns over donor site morbidity have led to a wide variety of bone graft substitutes. Despite prolific research, a general consensus is yet to be reached on bone graft materials that lead to optimal fusion. The purpose of this review is to evaluate the current literature for bone graft material options that maximize fusion rate in posterolateral lumbar fusion surgery. Systematic Review. A PRISMA-compliant systematic review of PubMed, EMBASE, and the Web of Science was conducted. Included studies were published from January 2000 to July 2015, were clinical human research studies involving available autograft, allograft, or synthetic bone graft options in posterolateral lumbar spine fusion, and reported radiographic fusion rate as a primary end outcome. This research had no funding source and the authors have no conflicts to declare. 81 articles underwent full-text review, and 48 were included in this study. 18 studies assessed fusion rate by plain radiographs alone (37.5%), while 6 used CT scan (12.5%), and 24 used both (50.0%). 45 studies looked at ICBG in conjunction with LAG (29), BCP(1), APC (2), BMPs (6), or DBM (1). Aggregate mean fusion rates among these ranged from 68.0 to 91.5%. 22 studies evaluated fusion rates of LAG, either isolated (3) or combined with ceramic extenders (8), DBM (4), BMP (1), BMA (4), APC (1), or ICBG(1). Aggregate mean fusion rate ranged from 75 to 95.5%. With the exception of studies involving allograft (mean fusion rate 40.0%), the mean fusion rate for all other graft combinations exceeded 70.0%. While our results find that LAG+BMA provided highest fusion rate, most material options analyzed in this study provide comparable fusion outcomes. The ideal graft option must incorporate a combination of materials with osteoconductive, osteoinductive, and osteogenic properties. Our results represent the robust and dynamic nature of the current state of lumbar graft technology. These slides can be retrieved under Electronic Supplementary Material.

Radiological assessment of experimental mono-segmental posterior-lateral lumbar fusion using autologous platelet rich fibrin

The results of the use of autologous platelet-rich fibrin, for pos­terolateral lumbar spinal fusion are discussed. Objective: to evaluate the radiographic signs of experimental posterolateral lumbar spine fusion using fibrin-rich platelets. Methods: mono segmental posterolateral lumbar spinal fusion performed in 42 adult male California rabbits aged 4–5 months, which were divided into 6 groups of 7 animals each. In the control group 1 grafts were not used in group 2 used the local autograft, group 3 — local autograft combined with fibrin-rich platelets, 4 — al­lograft of ilium, 5 — allograft from ilium combined with fibrin-rich platelets, 6 — fibrin-rich platelets. Results: revealed ra­diographic characteristics of posterolateral osteoplastic fusion, namely the formation of continuous trabecular bone in the area of spinal fusion, preserved height of interbody gaps, homoge­nous structure of newly formed bone, increasing the intensity of X-ray images in fusion masses. In radiometric studies iden­tified more intensive bone density block of rabbits in groups 3 and 5, as well as forming a homogeneous bone accretion in group 6. Conclusions: groups of rabbits with osteoplastic spinal fusion detected radiographic signs of bone formed block in 77.1 % of cases in the control decortication group of trans­verse processes — in 57.1 %. Results of roentgenometric zone fusion evaluation suggest that autologous platelet rich fibrin, promotes strong bone accretion.

Comparison of the osteogenesis and fusion rates between activin A/BMP-2 chimera (AB204) and rhBMP-2 in a beagle's posterolateral lumbar spine model

Background ContextActivin A/BMP-2 chimera (AB204) could promote bone healing more effectively than recombinant bone morphogenetic protein 2 (rhBMP-2) with much lower dose in a rodent model, but there is no report about the effectiveness of AB204 in a large animal model. PurposeThe purpose of this study was to compare the osteogenesis and fusion rate between AB204 and rhBMP-2 using biphasic calcium phosphate (BCP) as a carrier in a beagle's posterolateral lumbar fusion model. Study DesignThis is a randomized control animal study. MethodsSeventeen male beagle dogs were included. Bilateral posterolateral fusion was performed at the L1–L2 and L4–L5 levels. Biphasic calcium phosphate (2 cc), rhBMP-2 (50 µg)+BCP (2 cc), or AB204 (50 µg)+BCP (2 cc) were implanted into the intertransverse space randomly. X-ray was performed at 4 and 8 weeks. After 8 weeks, the animals were sacrificed, and new bone formation and fusion rate were evaluated by manual palpation, computed tomography (CT), and undecalcified histology. ResultsThe AB204 group showed significantly higher fusion rate (90%) than the rhBMP-2 group (15%) or the Osteon group (6.3%) by manual palpation. On x-ray and CT assessment, fusion rate and the volume of newly formed bone were also significantly higher in AB204 group than other groups. In contrast, more osteolysis was found in rhBMP-2 group (40%) than in AB204 group (10%) on CT study. In histologic results, new bone formation was sufficient between transverse processes in AB204 group, and obvious trabeculation and bone remodeling were observed. But in rhBMP-2 group, new bone formation was less than AB204 group and osteolysis was observed between the intertransverse spaces. ConclusionsA low dose of AB204 with BCP as a carrier significantly promotes the fusion rate in a large animal model when compared with the rhBMP-2. These findings demonstrate that AB204 could be an alternative to rhBMP-2 to improve fusion rate.

Readmission Rates, Reasons, and Risk Factors in Elderly Patients Treated With Lumbar Fusion for Degenerative Pathology.

Retrospective database review. To determine readmission rates after 1 to 2 level, primary, elective lumbar spinal fusion surgery for degenerative pathology and elucidate risk factors that predict increased risk of 30-day readmission SUMMARY OF BACKGROUND DATA.: Early postoperative readmissions after spine surgery represent a significant source of increased cost and morbidity. As the elderly population represents a demographic with a growing need for spine surgery, readmissions within this population are of significant interest. Medicare data (2005-2012) from an insurance database was queried for patients who underwent primary 1 to 2 level posterolateral lumbar spine fusion surgeries for degenerative lumbar pathology. After applying specific exclusion criteria to select for elderly patients (65-84 yr) undergoing mostly elective procedures, 52,567 patients formed the final study population. Readmission rates for medical, surgical, and all reasons were calculated within 30 days, 90 days, and 1 year postoperatively. Risk factors for medical, surgical, and all 30-day readmissions were also determined. Within 30 days, 90 days, and 1 year, 1510 (2.9%), 2776 (5.3%), and 6574 (12.5%) patients were readmitted, respectively. At 30 days, surgical diagnoses constituted 50.1% of all readmissions. Wound infection was the reason for readmission in 25.8% of all readmissions within 30 days. Diagnoses of chronic pulmonary disease (OR 1.41 95% CI 1.22-1.63), obesity (OR 2.20 95% CI 1.90-2.54), and positive smoking history (OR 1.33 95% CI 1.15-1.54) were associated with increased risk of surgical readmission. Elderly patients undergoing lumbar spine fusion experience 30-day, 90-day, and 1-year readmission rates of 2.9, 5.3, and 12.5% for both medical and surgical reasons. Surgical site infection and wound complications are the most common surgery-related reasons for readmission. Medical diagnoses are more predominant during later readmissions, highlighting the comorbidity burden present in elderly patients. 4.

Complications and Mortality After Lumbar Spinal Fusion in Elderly Patients With Late Stage Renal Disease.

Retrospective database review. To assess complication and mortality rates after lumbar spinal fusion surgery in patients with late stage renal disease. Lumbar spinal fusion surgeries are common in elderly patients who are well-known to have increased comorbidity burden. Elderly patients with severe chronic kidney disease (CKD) represent a population with poorly understood mortality and complication rates after spine surgery. Medicare data from the PearlDiver Database (2005-2012) was queried for patients who underwent primary 1-2 level posterolateral lumbar spine fusion surgeries. This cohort was divided into two study groups: a cohort with a preexisting diagnosis of late stage renal disease (N = 1654) and a control cohort of all other patients (N = 242,085). The control group was matched to the renal disease cohort by age, sex, and comorbidities. Moreover, 90-day complication rates and 90-day and 1-year mortality were assessed. The renal disease cohort had increased rates of all medical complications (21.3 vs. 14.2%; odds ratio, OR, 1.64; 95% confidence intervals, CI, 1.44 -1.85; P < 0.0001). Increased rates of infection (4.4 vs. 1.8%; OR 2.43; 95% CI 1.87 - 3.16; P < 0.0001) and procedure-day blood transfusions (20.7 vs. 14.7%; OR 1.51; 95% CI 1.33 - 1.72; P < 0.0001) were also observed in the renal disease cohort. Both 90-day (1.1 vs. 0.2%; OR 5.05; 95% CI 2.90-8.77; P < 0.0001) and 1-year mortality (1.9 vs. 0.7%; OR 2.77; 95% CI 1.87-4.11; P < 0.0001) were significantly higher in the renal disease group compared with the control group. Elderly patients with late-stage renal disease treated with 1-2 level posterolateral lumbar fusion have 1.6 times increased odds of experiencing a major medical complication within 3 months of surgery and 2.8 times increased odds of 1-year mortality when compared with matched controls. 3.

An allograft generated from adult stem cells and their secreted products efficiently fuses vertebrae in immunocompromised athymic rats and inhibits local immune responses

Background ContextSpine pain and the disability associated with it are epidemic in the United States. According to the National Center for Health Statistics, more than 650,000 spinal fusion surgeries are performed annually in the United States, and yet there is a failure rate of 15%–40% when standard methods employing current commercial bone substitutes are used. Autologous bone graft is the gold standard in terms of fusion success, but the morbidity associated with the procedure and the limitations in the availability of sufficient material have limited its use in the majority of cases. A freely available and immunologically compatible bone mimetic with the properties of live tissue is likely to substantially improve the outcome of spine fusion procedures without the disadvantages of autologous bone graft. PurposeThis study aimed to compare a live human bone tissue analog with autologous bone grafting in an immunocompromised rat model of posterolateral fusion. Design/SettingThis is an in vitro and in vivo preclinical study of a novel human stem cell–derived construct for efficacy in posterolateral lumbar spine fusion. MethodsOsteogenically enhanced human mesenchymal stem cells (OEhMSCs) were generated by exposure to conditions that activate the early stages of osteogenesis. Immunologic characteristics of OEhMSCs were evaluated in vitro. The secreted extracellular matrix from OEhMSCs was deposited on a clinical-grade gelatin sponge, resulting in bioconditioned gelatin sponge (BGS). Bioconditioned gelatin sponge was used alone, with live OEhMSCs (BGS+OEhMSCs), or with whole human bone marrow (BGS+hBM). Efficacy for spine fusion was determined by an institutionally approved animal model using 53 nude rats. ResultsBioconditioned gelatin sponge with live OEhMSCs did not cause cytotoxicity when incubated with immunologically mismatched lymphocytes, and OEhMSCs inhibited lymphocyte expansion in mixed lymphocyte assays. Bioconditioned gelatin sponge with live OEhMSC and BGS+hBM constructs induced profound bone growth at fusion sites in vivo, with a comparable rate of fusion with syngeneic bone graft (negative [0 of 10], BGS alone [0 of 10], bone graft [7 of 10], BGS+OEhMSC [10 of 15], and BGS+hBM [8 of 8]). ConclusionsCollectively, these studies demonstrate that BGS+OEhMSC constructs possess low immunogenicity and drive vertebral fusion with efficiency matching syngeneic bone graft in rodents. We also demonstrate that BGS serves as a promising scaffold for spine fusion when combined with hBM.

P38 - Complications and Mortality after Lumbar Spinal Fusion in Elderly Patients with Late Stage Renal Disease

STUDY DESIGN Retrospective database review. OBJECTIVE To assess complication and mortality rates after lumbar spinal fusion surgery in patients with late stage renal disease. SUMMARY OF BACKGROUND DATA Lumbar spinal fusion surgeries are common in elderly patients who are well-known to have increased comorbidity burden. Elderly patients with severe chronic kidney disease (CKD) represent a population with poorly understood mortality and complication rates after spine surgery. METHODS Medicare data from the PearlDiver Database (2005-2012) was queried for patients who underwent primary 1-2 level posterolateral lumbar spine fusion surgeries. This cohort was divided into two study groups: a cohort with a preexisting diagnosis of late stage renal disease (N = 1654) and a control cohort of all other patients (N = 242,085). The control group was matched to the renal disease cohort by age, sex, and comorbidities. Moreover, 90-day complication rates and 90-day and 1-year mortality were assessed. RESULTS The renal disease cohort had increased rates of all medical complications (21.3 vs. 14.2%; odds ratio, OR, 1.64; 95% confidence intervals, CI, 1.44 -1.85; P < 0.0001). Increased rates of infection (4.4 vs. 1.8%; OR 2.43; 95% CI 1.87 - 3.16; P < 0.0001) and procedure-day blood transfusions (20.7 vs. 14.7%; OR 1.51; 95% CI 1.33 - 1.72; P < 0.0001) were also observed in the renal disease cohort. Both 90-day (1.1 vs. 0.2%; OR 5.05; 95% CI 2.90-8.77; P < 0.0001) and 1-year mortality (1.9 vs. 0.7%; OR 2.77; 95% CI 1.87-4.11; P < 0.0001) were significantly higher in the renal disease group compared with the control group. CONCLUSION Elderly patients with late-stage renal disease treated with 1-2 level posterolateral lumbar fusion have 1.6 times increased odds of experiencing a major medical complication within 3 months of surgery and 2.8 times increased odds of 1-year mortality when compared with matched controls. LEVEL OF EVIDENCE 3.

P13 The use of collagen tripeptide, chitosan and hyaluronic acid based hydrogel for posterolateral lumbar spine fusion

P13 The use of collagen tripeptide, chitosan and hyaluronic acid based hydrogel for posterolateral lumbar spine fusion