- Email: [email protected]
27. Costs and utility of postdischarge acute inpatient rehabilitation following adult spinal deformity surgery
Proceedings of the 34th Annual Meeting of the North American Spine Society / The Spine Journal 19 (2019) S1−S58 were mobile; exclude pathological conditions; and assess sagittal Cobb angle (T4-T12). Pedicle screws were placed from T4-T12 bilaterally. Intact status was defined by over correcting the initial sagittal cobb measurement and reducing the precontoured, bilateral titanium alloy rods. Cobb measurements were repeated following rod reduction. Removed rods and repeated over correction process for the following release procedures implemented sequentially: (1) interspinous and supraspinous ligaments (ISL) transection; (2) ligamentum flavum transection; (3) Ponte osteotomy; (4) posterior longitudinal ligament transection (PLL); and (5) lateral discectomy. Used a novel rod-bender to create consistent, over corrected contoured rods at each step. Collected data on the radius of each rod’s curvature before and after each reduction. Cobb measurements collected on the instrumented construct for each procedure. Comparisons determined the effective contribution of each sequential release on the inducement of TK. RESULTS: Initial sagittal kyphosis from T4-12 was 38˚ and kyphosis increased to 52˚ with over correction with the precontoured rods applied. Each release resulted in 5-7˚ of additional kyphosis, and largest releases were ISL and PLL. The ISL transection was not significantly different than the intact condition with rod correction. All subsequent releases resulted in significant (p<0.05) increases in correction compared to the intact with rod correction. Regionally, kyphosis increase following successive releases was consistent at approximately 2˚ for superior, middle, and inferior regions. Comparing the radius of the precontoured rod curvature before and after application showed loss in rod curvature following reduction independent of the number of releases. CONCLUSIONS: Increased kyphosis was created in the thoracic spine using precontoured rods. Subsequent posterior releases provided a substantial, meaningful clinical change in the ability to induce additional kyphosis. Although each posterior release was effective for induction of TK (ISL and PLL having largest increase), ISL transection alone was not statistically different than the intact condition with rods applied. More than one release was necessary to induce a significant change in TK compared to the over correction accomplished on the intact thoracic spine. Rod flattening consistently occurred following attempted over correction with rod reduction, although the thoracic spine was sequentially destabilized with each release. Therefore, a presurgical plan for TK correction may be limited regardless of the number of releases performed. FDA DEVICE/DRUG STATUS: pre-contoured titanium alloy rods (Approved for this indication). https://doi.org/10.1016/j.spinee.2019.05.038
26. Posterior ligamentous reinforcement does not prevent proximal junctional kyphosis in adult spinal deformity Sravisht Iyer, MD1, Francis C. Lovecchio, MD2, Jonathan Elysee2, Renaud Lafage, MSc2, Frank J. Schwab, MD2, Virginie Lafage, PhD2, Han Jo Kim, MD2; 1 Rush University Medical Center, Chicago, IL, US; 2 Hospital for Special Surgery, New York, NY, US BACKGROUND CONTEXT: Violation of the posterior soft tissues is believed to contribute to the development of proximal junctional kyphosis (PJK). Clinical and biomechanical studies have suggested that augmentation of the posterior ligamentous structures (PLS) may help prevent PJK. PURPOSE: To determine whether augmentation of the PLS from the UIV-1 to UIV+1 prevents PJK. STUDY DESIGN/SETTING: Single-surgeon retrospective cohort study. PATIENT SAMPLE: One hundred fifty adult spinal deformity patients. OUTCOME MEASURES: PJK (defined as a proximal junctional angle ≥20˚) at final follow-up. METHODS: We conducted a retrospective cohort study of 150 adult spinal deformity patients who underwent ≥5 level fusions to the pelvis by a single surgeon between 2014 and 2017. Exclusion criteria included neuromuscular or congenital scoliosis (18 patients), or follow-up less than 1 year (24 patients), leaving 108 patients available for final analysis. Patients were divided into two groups: PLS+ patients had reconstruction of the PLS
S13
between UIV+1 and UIV-1 with a surgical nylon tape while PLS- patients did not. Demographics, surgical data, and sagittal alignment parameters were compared between the cohorts. The primary outcome of interest was the development of PJK at final follow-up (1 or 2 years). A subgroup propensity match and backward stepwise logistic regression model were utilized to control for surgical and radiographic differences in the cohorts. RESULTS: Thirty-one patients (28.7%) were PLS+. There were no differences with regard to preoperative or final sagittal alignment parameters, number of levels fused (10.7§3.8 vs 9.7§3.8, p=0.331), and BMI (24.9§ 5.2 vs 27.0§6.9 kg/m2, p=0.143), though the PLS+ cohort was older (64.1§10.4 vs 51.3§21.4 years, p=0.002) and had greater 6-week corrections in sacral slope (SS), pelvic tilt (PT), pelvic incidence-lumbar lordosis (PI-LL), C7-S1 sagittal vertical axis (C7 SVA), and T1 pelvic angle (T1PA), p<0.05 for all. The rates of PJK for PLS+ (27.3%) and PLS(28.6%) were similar (p=0.827). In subgroup analyses, the choice of UIV (above or below T9) did not affect the rates of PJK (below T9, 29.4% PLS + vs 37.8% PLS-, p=0.547; above T9, 28.6% PLS+ vs 25.0% PLS-, p=0.793). After controlling for sagittal correction via propensity matching to a PLS- cohort with comparable sagittal corrections (p>0.05 for 6-week changes in SS, PT, LL, PI-LL, C7 SVA, T1PA, thoracic kyphosis, thoracolumbar kyphosis, and cervical lordosis), PLS augmentation was still not associated with a lower rate of PJK (29% PLS+ vs 38.7% PLS-, p=0.367). In our multivariate analysis, only increased sagittal malalignment and failure to restore sagittal balance were retained as having independent associations with PJK, while PLS+ was not retained in the model. CONCLUSIONS: Even after controlling for relevant variables such as age, preoperative alignment, and degree of correction, PLS reinforcement at the UIV+1 did not reduce the incidence of PJK at 1 year. Our findings emphasize the multifactorial nature of PJK and the difficulty of preventing PJK with a single surgical technique FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. https://doi.org/10.1016/j.spinee.2019.05.039
27. Costs and utility of postdischarge acute inpatient rehabilitation following adult spinal deformity surgery Alexander A. Theologis, MD1, Darryl Lau, MD2, Cecilia L. Dalle Ore, BA3, Vedat Deviren, MD3, Christopher P. Ames, MD3; 1 UCSF Spine Center, San Francisco, CA, US; 2 San Francisco, CA, US; 3 University of California, San Francisco, San Francisco, CA, US BACKGROUND CONTEXT: As the United States’ health care system transitions to a value-based approach, defining costs for entire episodes of care is fundamental to determining value. This is particularly important for adults with spinal deformity (ASD) who undergo surgical intervention. PURPOSE: To further the discussion on costs of operative care for ASD, this study aims to evaluate the costs and functional utility of postdischarge acute inpatient rehabilitation after surgery for ASD. STUDY DESIGN/SETTING: Single-center, retrospective cohort analysis. PATIENT SAMPLE: Adults with spinal deformity (ASD) who underwent operative intervention (>7 levels fused) at a single tertiary care referral center and who were discharged postoperatively to one acute inpatient rehabilitation facility. OUTCOME MEASURES: Patient demographics, operative details, direct costs and length of stay for inpatient hospitilization and acute postoperative rehabilitation, and patient function, as assessed by the Functional Independence Measure (FIM) instrument. METHODS: Patient demographics, operative details, and costs were obtained for the index operation’s inpatient encounter. Data for acute rehabilitation included: direct costs, length of stay, and patient function, as assessed by the Functional Independence Measure (FIM) instrument [scores 18-30 (total assistance), 31-45 (maximal assistance), 46-63 (moderate assistance), 64-80 (minimal assistance), 81-100 (supervision), 101-125 (modified independence), 126 (complete independence)]. Student T-tests and Chi-square tests were used to compared continuous and categorical
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.
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Proceedings of the 34th Annual Meeting of the North American Spine Society / The Spine Journal 19 (2019) S1−S58
variables. Pearson’s tests were used to assess correlations. p<0.05 set statistical significance. RESULTS: Ninety patients (95 episodes of care; average age 70.5§10.6 years; male-31, female-59) were included. After operations, average inpatient length of stay was 8.2§2.6 days (4-16 days). Operative details included: posterior levels fused 13.6§3.6 (7-21 levels), posterior column osteotomies (per patient) 7§3.7 (range, 1-15; n=49 patients), forty-two 3COs (PSO-35, VCR-7), and 11 interbody fusions. Average direct costs were $90,738§$24,166 ($36,521−$141,090) for index inpatient stays and $38,808§$14,752 ($8,679−$100,829) for post-discharge acute rehabilitation (Figure 1). Patients spent an average of 11.7§4.0 days (2-28 days) in acute rehabilitation postdischarge. Average direct cost per day in rehabilitation was $3,338 §$2,131 ($506-$4,340). Significant improvements in function (FIM) were observed [admit: 66§14 (15−91) vs discharge: 94§ 14 (54−116); % improvement: 29§14]. CONCLUSIONS: Postdischarge inpatient acute rehabilitation following operations for adult spinal deformity is associated with an average direct cost of $38,808 per case. While rehabilitation resulted in significant functional improvements, it came at a very significant economic expense amounting to $3.7 million, which accounted for 30% of the costs for 95 episodes of care. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. https://doi.org/10.1016/j.spinee.2019.05.040
Wednesday, September 25, 2019 7:30 − 8:55 AM Thoracolumbar Surgery I 28. Evaluation of three commercially available synthetic bone grafts in a clinically relevant ovine model of instrumented lumbar posterolateral fusion Lukas A. van Dijk, MSc; University Medical Centre Utrecht, Utrecht, Netherlands BACKGROUND CONTEXT: Synthetic bone grafts are important tools for spinal surgeons who wish to avoid the invasive harvesting of autologous bone graft for spinal fusions. Various synthetic bone grafts are available on the market, including materials based on bioglass, calcium phosphate or a combination of both. Side-by-side comparisons of synthetic bone grafts in relevant preclinical study models can provide valuable insights that can aid in the selection of treatment options. PURPOSE: The current study compared three commercially available synthetic bone grafts as stand-alone grafts in a clinically relevant ovine model of instrumented posterolateral fusion (PLF). STUDY DESIGN/SETTING: The three different synthetic bone grafts evaluated are: (1) putty formulation of biphasic calcium phosphate with submicron topography that was previously shown to have equivalent performance to autograft in this model (BCP; MagnetOs Putty, Kuros Biosciences BV), (2) putty formulation of 45S5 bioglass (BG; Novabone Putty, Novabone Products LLC), (3) composite of beta-tri-calcium phosphate, 45S5 bioglass and bovine type I collagen (TCP+BG; Vitoss BA2X Foam pack, Orthovita, Inc). Autograft bone (AB) was used as positive control. Twelve weeks after implantation, the treatments were evaluated. OUTCOME MEASURES: Main study end points include fusion assessment by manual palpation, X-ray imaging and micro-CT scans. Range of motion (ROM) of spine levels was assessed in lateral bending (LB) and flexion-extension (FE). Quantification of fusion mass volume was performed using micro-CT. Histology was performed to evaluate bone formation and tissue responses with the different graft materials. METHODS: Following ethical approval, 9 sheep underwent instrumented PLF surgery at L2-3 and L4-5 levels. Autograft was harvested from the Os Ilium and distal femur. After decortication of the transverse processes (TPs), 10 cc of each graft material (AB; n=6, BCP; n=6, BG; n=3, TCP +BG; n=3) was implanted bilaterally in the posterolateral regions, bridging
the inter-transverse process space. After sacrifice, specimens were assessed by manual palpation, X-ray imaging, Micro-CT and ROM testing at 7.5 Nm after removing instrumentation. Subsequently, treated spine levels were processed for histology in polymethylmethacrylate to visualize bone tissue in the fusion mass. RESULTS: Fusion assessment by manual palpation revealed a 6/6 fusion rate for AB and BCP, while for both BG and TCP+BG, a 1/3 fusion rate was determined. Fusion assessment of X-ray and Micro-CT were consistent and determined an either unilateral or bilateral robust bone bridge in 6/6 levels for both AB and BCP, while The BG group exhibited unilateral bridging in 2/3 levels and the TCP+BG group did not include a robust bone bridge in any of the levels. ROM testing revealed equivalent ROMs in LB and FE for AB and BCP, being substantially and significantly lower than those of BG and TCP+BG groups. Fusion mass volume quantification determined fusion mass volumes of 5.7 § 1.6 cm3 for AB, 9.6 § 0.4 cm3 for BCP, 3.0 § 1.1 cm3 for BG and 2.4 § 1.0 cm3 for TCP+BG. Correspondingly, histology revealed significant graft resorption for BG and TCP +BG groups, while abundant bone tissue in the inter-TP space was observed for AB and BCP. A continuous bony bridge in between TPs was frequently observed in the BCP group on histological sections. CONCLUSIONS: Calcium phosphate with submicron topography was the only synthetic bone graft to perform equally well as autograft as a standalone graft in this PLF model. Both bioglass-based bone grafts significantly underperformed as compared to autograft and BCP on every single assessment method. The bioglass-based synthetics were observed to undergo significant resorption and were not able to induce bone formation in the soft tissue region in between the TPs. Calcium phosphate with submicron topography may be the better treatment option than bioglass-based bone grafts as a synthetic bone graft substitute. FDA DEVICE/DRUG STATUS: MagnetOs Granules (Investigational/ Not approved), Novabone Putty (Approved for this indication), Vitoss BA2X (Approved for this indication). https://doi.org/10.1016/j.spinee.2019.05.041
29. Understanding surgeon decision-making and current surgical practice regarding the DSIC scheme and DLS treatment: a CSORN study Audrey Maher; Ottawa, ON, Canada BACKGROUND CONTEXT: Degenerative lumbar spondylolisthesis (DLS) is a spinal pathology involving the slip of one or more lumbar spinal vertebrae. It is most common in women and African-Americans above the age of 50, and usually involves the anterior slip of the fourth lumbar vertebra of up to 30% of its vertebral body width due to the more sagittally-oriented facet joints, and therefore, high force concentration at that level. Despite its worldwide prevalence of about 6%, the classification and treatment of DLS is not standardized. In 2015, Simmonds et al published the largest to-date systematic review of best available evidence and proposed a degenerative spondylolisthesis instability classification (DSIC) scheme. This classification scheme proposes that the stability of the patient’s pathology be determined by a surgeon based on quantitative and qualitative clinical and radiographic parameters. PURPOSE: This study aims to determine whether surgeons are following DSIC scheme treatment recommendations. It also aims to determine which radiographic and/ or clinical parameters and/ or surgeon characteristics are most influencing classification and treatment decisions. The goal of this study is to shed light on current surgeon treatment decisions and to better understand the factors most taken into account. In order for the treatment of DLS to become standardized, and therefore uniform and cost effective, we must first understand how current treatment decisions are made. STUDY DESIGN/SETTING: This study used data from CSORN collected by surgeons across Canada between 2015 and 2018. Statistical analysis was used to determine which factors most influenced the classification and treatment decision of the surgeons. PATIENT SAMPLE: A total of 224 patients.
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.
26. Posterior ligamentous reinforcement does not prevent proximal junctional kyphosis in adult spinal deformity Sravisht Iyer, MD1, Francis C. Lovecchio, MD2, Jonathan Elysee2, Renaud Lafage, MSc2, Frank J. Schwab, MD2, Virginie Lafage, PhD2, Han Jo Kim, MD2; 1 Rush University Medical Center, Chicago, IL, US; 2 Hospital for Special Surgery, New York, NY, US BACKGROUND CONTEXT: Violation of the posterior soft tissues is believed to contribute to the development of proximal junctional kyphosis (PJK). Clinical and biomechanical studies have suggested that augmentation of the posterior ligamentous structures (PLS) may help prevent PJK. PURPOSE: To determine whether augmentation of the PLS from the UIV-1 to UIV+1 prevents PJK. STUDY DESIGN/SETTING: Single-surgeon retrospective cohort study. PATIENT SAMPLE: One hundred fifty adult spinal deformity patients. OUTCOME MEASURES: PJK (defined as a proximal junctional angle ≥20˚) at final follow-up. METHODS: We conducted a retrospective cohort study of 150 adult spinal deformity patients who underwent ≥5 level fusions to the pelvis by a single surgeon between 2014 and 2017. Exclusion criteria included neuromuscular or congenital scoliosis (18 patients), or follow-up less than 1 year (24 patients), leaving 108 patients available for final analysis. Patients were divided into two groups: PLS+ patients had reconstruction of the PLS
S13
between UIV+1 and UIV-1 with a surgical nylon tape while PLS- patients did not. Demographics, surgical data, and sagittal alignment parameters were compared between the cohorts. The primary outcome of interest was the development of PJK at final follow-up (1 or 2 years). A subgroup propensity match and backward stepwise logistic regression model were utilized to control for surgical and radiographic differences in the cohorts. RESULTS: Thirty-one patients (28.7%) were PLS+. There were no differences with regard to preoperative or final sagittal alignment parameters, number of levels fused (10.7§3.8 vs 9.7§3.8, p=0.331), and BMI (24.9§ 5.2 vs 27.0§6.9 kg/m2, p=0.143), though the PLS+ cohort was older (64.1§10.4 vs 51.3§21.4 years, p=0.002) and had greater 6-week corrections in sacral slope (SS), pelvic tilt (PT), pelvic incidence-lumbar lordosis (PI-LL), C7-S1 sagittal vertical axis (C7 SVA), and T1 pelvic angle (T1PA), p<0.05 for all. The rates of PJK for PLS+ (27.3%) and PLS(28.6%) were similar (p=0.827). In subgroup analyses, the choice of UIV (above or below T9) did not affect the rates of PJK (below T9, 29.4% PLS + vs 37.8% PLS-, p=0.547; above T9, 28.6% PLS+ vs 25.0% PLS-, p=0.793). After controlling for sagittal correction via propensity matching to a PLS- cohort with comparable sagittal corrections (p>0.05 for 6-week changes in SS, PT, LL, PI-LL, C7 SVA, T1PA, thoracic kyphosis, thoracolumbar kyphosis, and cervical lordosis), PLS augmentation was still not associated with a lower rate of PJK (29% PLS+ vs 38.7% PLS-, p=0.367). In our multivariate analysis, only increased sagittal malalignment and failure to restore sagittal balance were retained as having independent associations with PJK, while PLS+ was not retained in the model. CONCLUSIONS: Even after controlling for relevant variables such as age, preoperative alignment, and degree of correction, PLS reinforcement at the UIV+1 did not reduce the incidence of PJK at 1 year. Our findings emphasize the multifactorial nature of PJK and the difficulty of preventing PJK with a single surgical technique FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. https://doi.org/10.1016/j.spinee.2019.05.039
27. Costs and utility of postdischarge acute inpatient rehabilitation following adult spinal deformity surgery Alexander A. Theologis, MD1, Darryl Lau, MD2, Cecilia L. Dalle Ore, BA3, Vedat Deviren, MD3, Christopher P. Ames, MD3; 1 UCSF Spine Center, San Francisco, CA, US; 2 San Francisco, CA, US; 3 University of California, San Francisco, San Francisco, CA, US BACKGROUND CONTEXT: As the United States’ health care system transitions to a value-based approach, defining costs for entire episodes of care is fundamental to determining value. This is particularly important for adults with spinal deformity (ASD) who undergo surgical intervention. PURPOSE: To further the discussion on costs of operative care for ASD, this study aims to evaluate the costs and functional utility of postdischarge acute inpatient rehabilitation after surgery for ASD. STUDY DESIGN/SETTING: Single-center, retrospective cohort analysis. PATIENT SAMPLE: Adults with spinal deformity (ASD) who underwent operative intervention (>7 levels fused) at a single tertiary care referral center and who were discharged postoperatively to one acute inpatient rehabilitation facility. OUTCOME MEASURES: Patient demographics, operative details, direct costs and length of stay for inpatient hospitilization and acute postoperative rehabilitation, and patient function, as assessed by the Functional Independence Measure (FIM) instrument. METHODS: Patient demographics, operative details, and costs were obtained for the index operation’s inpatient encounter. Data for acute rehabilitation included: direct costs, length of stay, and patient function, as assessed by the Functional Independence Measure (FIM) instrument [scores 18-30 (total assistance), 31-45 (maximal assistance), 46-63 (moderate assistance), 64-80 (minimal assistance), 81-100 (supervision), 101-125 (modified independence), 126 (complete independence)]. Student T-tests and Chi-square tests were used to compared continuous and categorical
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.
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Proceedings of the 34th Annual Meeting of the North American Spine Society / The Spine Journal 19 (2019) S1−S58
variables. Pearson’s tests were used to assess correlations. p<0.05 set statistical significance. RESULTS: Ninety patients (95 episodes of care; average age 70.5§10.6 years; male-31, female-59) were included. After operations, average inpatient length of stay was 8.2§2.6 days (4-16 days). Operative details included: posterior levels fused 13.6§3.6 (7-21 levels), posterior column osteotomies (per patient) 7§3.7 (range, 1-15; n=49 patients), forty-two 3COs (PSO-35, VCR-7), and 11 interbody fusions. Average direct costs were $90,738§$24,166 ($36,521−$141,090) for index inpatient stays and $38,808§$14,752 ($8,679−$100,829) for post-discharge acute rehabilitation (Figure 1). Patients spent an average of 11.7§4.0 days (2-28 days) in acute rehabilitation postdischarge. Average direct cost per day in rehabilitation was $3,338 §$2,131 ($506-$4,340). Significant improvements in function (FIM) were observed [admit: 66§14 (15−91) vs discharge: 94§ 14 (54−116); % improvement: 29§14]. CONCLUSIONS: Postdischarge inpatient acute rehabilitation following operations for adult spinal deformity is associated with an average direct cost of $38,808 per case. While rehabilitation resulted in significant functional improvements, it came at a very significant economic expense amounting to $3.7 million, which accounted for 30% of the costs for 95 episodes of care. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. https://doi.org/10.1016/j.spinee.2019.05.040
Wednesday, September 25, 2019 7:30 − 8:55 AM Thoracolumbar Surgery I 28. Evaluation of three commercially available synthetic bone grafts in a clinically relevant ovine model of instrumented lumbar posterolateral fusion Lukas A. van Dijk, MSc; University Medical Centre Utrecht, Utrecht, Netherlands BACKGROUND CONTEXT: Synthetic bone grafts are important tools for spinal surgeons who wish to avoid the invasive harvesting of autologous bone graft for spinal fusions. Various synthetic bone grafts are available on the market, including materials based on bioglass, calcium phosphate or a combination of both. Side-by-side comparisons of synthetic bone grafts in relevant preclinical study models can provide valuable insights that can aid in the selection of treatment options. PURPOSE: The current study compared three commercially available synthetic bone grafts as stand-alone grafts in a clinically relevant ovine model of instrumented posterolateral fusion (PLF). STUDY DESIGN/SETTING: The three different synthetic bone grafts evaluated are: (1) putty formulation of biphasic calcium phosphate with submicron topography that was previously shown to have equivalent performance to autograft in this model (BCP; MagnetOs Putty, Kuros Biosciences BV), (2) putty formulation of 45S5 bioglass (BG; Novabone Putty, Novabone Products LLC), (3) composite of beta-tri-calcium phosphate, 45S5 bioglass and bovine type I collagen (TCP+BG; Vitoss BA2X Foam pack, Orthovita, Inc). Autograft bone (AB) was used as positive control. Twelve weeks after implantation, the treatments were evaluated. OUTCOME MEASURES: Main study end points include fusion assessment by manual palpation, X-ray imaging and micro-CT scans. Range of motion (ROM) of spine levels was assessed in lateral bending (LB) and flexion-extension (FE). Quantification of fusion mass volume was performed using micro-CT. Histology was performed to evaluate bone formation and tissue responses with the different graft materials. METHODS: Following ethical approval, 9 sheep underwent instrumented PLF surgery at L2-3 and L4-5 levels. Autograft was harvested from the Os Ilium and distal femur. After decortication of the transverse processes (TPs), 10 cc of each graft material (AB; n=6, BCP; n=6, BG; n=3, TCP +BG; n=3) was implanted bilaterally in the posterolateral regions, bridging
the inter-transverse process space. After sacrifice, specimens were assessed by manual palpation, X-ray imaging, Micro-CT and ROM testing at 7.5 Nm after removing instrumentation. Subsequently, treated spine levels were processed for histology in polymethylmethacrylate to visualize bone tissue in the fusion mass. RESULTS: Fusion assessment by manual palpation revealed a 6/6 fusion rate for AB and BCP, while for both BG and TCP+BG, a 1/3 fusion rate was determined. Fusion assessment of X-ray and Micro-CT were consistent and determined an either unilateral or bilateral robust bone bridge in 6/6 levels for both AB and BCP, while The BG group exhibited unilateral bridging in 2/3 levels and the TCP+BG group did not include a robust bone bridge in any of the levels. ROM testing revealed equivalent ROMs in LB and FE for AB and BCP, being substantially and significantly lower than those of BG and TCP+BG groups. Fusion mass volume quantification determined fusion mass volumes of 5.7 § 1.6 cm3 for AB, 9.6 § 0.4 cm3 for BCP, 3.0 § 1.1 cm3 for BG and 2.4 § 1.0 cm3 for TCP+BG. Correspondingly, histology revealed significant graft resorption for BG and TCP +BG groups, while abundant bone tissue in the inter-TP space was observed for AB and BCP. A continuous bony bridge in between TPs was frequently observed in the BCP group on histological sections. CONCLUSIONS: Calcium phosphate with submicron topography was the only synthetic bone graft to perform equally well as autograft as a standalone graft in this PLF model. Both bioglass-based bone grafts significantly underperformed as compared to autograft and BCP on every single assessment method. The bioglass-based synthetics were observed to undergo significant resorption and were not able to induce bone formation in the soft tissue region in between the TPs. Calcium phosphate with submicron topography may be the better treatment option than bioglass-based bone grafts as a synthetic bone graft substitute. FDA DEVICE/DRUG STATUS: MagnetOs Granules (Investigational/ Not approved), Novabone Putty (Approved for this indication), Vitoss BA2X (Approved for this indication). https://doi.org/10.1016/j.spinee.2019.05.041
29. Understanding surgeon decision-making and current surgical practice regarding the DSIC scheme and DLS treatment: a CSORN study Audrey Maher; Ottawa, ON, Canada BACKGROUND CONTEXT: Degenerative lumbar spondylolisthesis (DLS) is a spinal pathology involving the slip of one or more lumbar spinal vertebrae. It is most common in women and African-Americans above the age of 50, and usually involves the anterior slip of the fourth lumbar vertebra of up to 30% of its vertebral body width due to the more sagittally-oriented facet joints, and therefore, high force concentration at that level. Despite its worldwide prevalence of about 6%, the classification and treatment of DLS is not standardized. In 2015, Simmonds et al published the largest to-date systematic review of best available evidence and proposed a degenerative spondylolisthesis instability classification (DSIC) scheme. This classification scheme proposes that the stability of the patient’s pathology be determined by a surgeon based on quantitative and qualitative clinical and radiographic parameters. PURPOSE: This study aims to determine whether surgeons are following DSIC scheme treatment recommendations. It also aims to determine which radiographic and/ or clinical parameters and/ or surgeon characteristics are most influencing classification and treatment decisions. The goal of this study is to shed light on current surgeon treatment decisions and to better understand the factors most taken into account. In order for the treatment of DLS to become standardized, and therefore uniform and cost effective, we must first understand how current treatment decisions are made. STUDY DESIGN/SETTING: This study used data from CSORN collected by surgeons across Canada between 2015 and 2018. Statistical analysis was used to determine which factors most influenced the classification and treatment decision of the surgeons. PATIENT SAMPLE: A total of 224 patients.
Refer to onsite annual meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosure and FDA device/drug status at time of abstract submission.