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Pedicle Screw Safety: How Much Anterior Breach is Safe? A Cadaveric- and CT-Based Study
Proceedings of the NASS 29th Annual Meeting / The Spine Journal 14 (2014) 1S–183S perioperative morbidity. The use of minimally invasive surgery (MIS) for correction of ADS has been theorized to lower the perioperative morbidity when compared to traditional open surgical approaches. However, there is concern that patients treated with MIS techniques will not achieve the same level of clinical improvement as those treated with traditional open surgery approaches. This study compared patients treated with MIS (MIS lateral or transforaminal interbody fusion (LIF or TLIF) with percutaneous pedicle screw fixation), hybrid techniques (HYB) (MIS LIF or TLIF in combination with open posterior pedicle screw fixation), and open techniques to assess ODI at 1 and 2 years. PURPOSE: To compare disability outcomes between open and MIS deformity surgery. STUDY DESIGN/SETTING: Retrospective review of propensity matched cohorts. PATIENT SAMPLE: 120 patients with adult deformity treated with MIS, hybrid or open surgeries. OUTCOME MEASURES: Radiographic parameters and ODI. METHODS: All cases were reviewed retrospectively. Inclusion criteria included: ageO18yr, ASD, min 2-yr follow-up. Patients treated for adult spinal deformity using either less invasive or open surgical approaches were propensity matched by preop SVA, baseline ODI, and by number of fused levels. Patients’ results were compared at 1 and 2 years postop. RESULTS: 40 patients were propensity matched into each group for a total number of 120. Mean number of levels fused and SVA was HYB 5 5.9, 37.7mm, MIS 5 3.7, 30.7mm, OPEN 5 6.0, 47.5 mm. At baseline, ODI was: HYB569.6, MIS549.7, Open549.6. At postop 1 year patients reported significantly improved ODI (P!0.01 when compared to baseline) (HYB537.3, MIS526.8, Open535.6) (between groups PO0.05). At 2 years the patients maintained improvement in disability (HYB537.5, SVA 43.6, MIS 28.0, SVA 34.5, and Open 30.6, SVA 33.5). CONCLUSIONS: Patients treated with MIS techniques can achieve similar reductions in disability to those treated with open deformity surgery. When matched by SVA, number of levels and baseline ODI, there was no statistically significant difference in disability at 1 and 2 years after surgery. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.369
P116. Pedicle Screw Safety: How Much Anterior Breach is Safe? A Cadaveric- and CT-Based Study Vishal Sarwahi, MD1, Terry D. Amaral, MD2, Monica Payares, MD3, Aviva Dworkin3, Dan Wang4, Adam L. Wollowick, MD2; 1New York, NY, US; 2Bronx, NY, US; 3Montefiore Medical Center, Bronx, NY, US; 4Albert Einstein College of Medicine, Bronx, NY, US BACKGROUND CONTEXT: Pedicle screw misplacement rate varies from 6%-15%. Most commonly these misplacements are anterior or anterolateral and these can potentially endanger vital structures. While the limits of medial breach (!3mm) are known, the safe limits for anterior/ anterolaterally breach are not yet defined. PURPOSE: Purpose is to determine the safety limits of an anterior/ anterior lateral misplaced pedicle screw in spinal deformity. STUDY DESIGN/SETTING: Basic science/cadaveric/retrospective. PATIENT SAMPLE: Eight cadavers were instrumented and postoperative CT scans of 165 patients operated on for spine deformity were reviewed. OUTCOME MEASURES: Fisher’s exact test. METHODS: This study had two parts. In part I, 8 cadavers were instrumented with 6 x 30mm and 6x40mm bilaterally from T1-S1. Screws were randomly inserted under navigation guidance into 3 positions: in, out medial, out anterior laterally. CT scan was performed, followed by gross dissection to determine screw position. In part II, postoperative CT scans of 165 patients operated on for spine deformity were reviewed for screw misplacement (2800 screws). The amount of breach for anterior/anterolateral
153S
was measured. Protrusions were also evaluated for proximity to vital structures. All scans were reviewed by musculoskeletal radiologist. RESULTS: Part I: 285 screws were inserted. 93 were misplaced anterior/ anterolaterally. On gross dissection, 89 were misplaced; 67 protruded through soft tissue and were easily visualized while 32 were covered entirely by soft tissue but were palpable. These 32 screws did not endanger any structures. All 32 screws protruded !4mm on CT scan. Part II: 117 (4.14%) screws were misplaced anterior/anterolaterally. 31 (26.5%) were adjacent to vital structures. Fisher’s exact test showed !4mm breach has significantly lower likelihood of impingement (p!0.001) and sensitivity 81%. Screws adjacent/impinging the aorta protruded an avg 5.7 mm (SE 0.6), while screws not involving the aorta breached an avg 3.9 mm (SE 0.2), p50.005. CONCLUSIONS: Anterior/anterolateral breaches !4mm on CT poses no significant risk of impingement and therefore can be considered safe. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.370
P117. Adolescent Idiopathic Scoliosis Patients Are at Increased Risk for Pulmonary Hypertension which Reverses After Scoliosis Surgery Vishal Sarwahi, MD1, Rachel E. Borlack, BS2, Aviva Dworkin3, Dan Wang4, Sarika Kalantre, MD5; 1New York, NY, US; 2Bronx, NY, US; 3 Montefiore Medical Center, Bronx, NY, US; 4Albert Einstein College of Medicine, Bronx, NY, US; 5Children’s Hospital at Montefiore, Bronx, NY, US BACKGROUND CONTEXT: The incidence of structural cardiac disease and pulmonary hypertension in Adolescent Idiopathic Scoliosis (AIS) patients has been infrequently studied. Pulmonary hypertension has a high mortality rate. PURPOSE: The purpose of this study is to determine the incidence of structural cardiac anomalies and pulmonary hypertension in AIS patients and its relationship with curve severity. This is the first study to document evidence of pulmonary hypertension (pulm HT) in AIS patients, the severity of which directly correlates with the size of the curve. Pulmonary hypertension, which can potentially be fatal, reverts to normal after corrective scoliosis surgery. These findings provide direct evidence of immediate benefit of scoliosis surgery and can change the entire scoliosis treatment paradigm. STUDY DESIGN/SETTING: Retrospective study. PATIENT SAMPLE: 107 AIS patients whom had screening echocardiograms. OUTCOME MEASURES: Spearman correlation and Logistic Regression analysis. METHODS: Retrospective review of AIS pts with PSF from ‘09 –‘12 was done. 2D echos where reviewed for structural heart disease, aortic root size, and Tricuspid regurgitant jet velocity (TRV). Right ventricular systolic pressure (RVSP) was estimated using the Bernoulli’s equation (4*(TRV)2 þ right atrial pressure). RVSP O 25mm Hg was indicates pulmonary hypertension. 2D echo of 100 aged matched health adolescents served as control. RESULTS: 160 pts had spinal fusion surgery in the study period. Of these, 120 had AIS and 107 AIS pts (72F:35M) had screening 2D echos. Average age was 14.8 6 2.2 years. Average Cobb angle was 50.9612.3 . 2 AIS pts had ASD, 2 had VSD, and 3 had MVP, while 64 pts had mild to trivial mitral regurgitation. 24 AIS pts had higher incidence of mild tricuspid regurgitation (p!0.001) and higher TRV/ RVSP (O25 mm Hg) (p50.04) indicating pulmonary HT. Spearman correlation coefficient between Cobb angle and RVSP was 0.32 in AIS (p50.04). This is a significant correlation between increasing Cobb and worsening RVSP. Logistic Regression showed an odds ratio of 3.29 for elevated TRV (meaning increased pulmonary HT) in AIS (p 5 0.007).18 out of 24 AIS patients with elevated TRV/ RVSP had 2D echo at 2 year post-op. All had normal RVSP (mean 20.4 mm Hg), which shows reversal of pulmonary HT to normal values.
Refer to onsite Annual Meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosures and FDA device/drug status at time of abstract submission.
P116. Pedicle Screw Safety: How Much Anterior Breach is Safe? A Cadaveric- and CT-Based Study Vishal Sarwahi, MD1, Terry D. Amaral, MD2, Monica Payares, MD3, Aviva Dworkin3, Dan Wang4, Adam L. Wollowick, MD2; 1New York, NY, US; 2Bronx, NY, US; 3Montefiore Medical Center, Bronx, NY, US; 4Albert Einstein College of Medicine, Bronx, NY, US BACKGROUND CONTEXT: Pedicle screw misplacement rate varies from 6%-15%. Most commonly these misplacements are anterior or anterolateral and these can potentially endanger vital structures. While the limits of medial breach (!3mm) are known, the safe limits for anterior/ anterolaterally breach are not yet defined. PURPOSE: Purpose is to determine the safety limits of an anterior/ anterior lateral misplaced pedicle screw in spinal deformity. STUDY DESIGN/SETTING: Basic science/cadaveric/retrospective. PATIENT SAMPLE: Eight cadavers were instrumented and postoperative CT scans of 165 patients operated on for spine deformity were reviewed. OUTCOME MEASURES: Fisher’s exact test. METHODS: This study had two parts. In part I, 8 cadavers were instrumented with 6 x 30mm and 6x40mm bilaterally from T1-S1. Screws were randomly inserted under navigation guidance into 3 positions: in, out medial, out anterior laterally. CT scan was performed, followed by gross dissection to determine screw position. In part II, postoperative CT scans of 165 patients operated on for spine deformity were reviewed for screw misplacement (2800 screws). The amount of breach for anterior/anterolateral
153S
was measured. Protrusions were also evaluated for proximity to vital structures. All scans were reviewed by musculoskeletal radiologist. RESULTS: Part I: 285 screws were inserted. 93 were misplaced anterior/ anterolaterally. On gross dissection, 89 were misplaced; 67 protruded through soft tissue and were easily visualized while 32 were covered entirely by soft tissue but were palpable. These 32 screws did not endanger any structures. All 32 screws protruded !4mm on CT scan. Part II: 117 (4.14%) screws were misplaced anterior/anterolaterally. 31 (26.5%) were adjacent to vital structures. Fisher’s exact test showed !4mm breach has significantly lower likelihood of impingement (p!0.001) and sensitivity 81%. Screws adjacent/impinging the aorta protruded an avg 5.7 mm (SE 0.6), while screws not involving the aorta breached an avg 3.9 mm (SE 0.2), p50.005. CONCLUSIONS: Anterior/anterolateral breaches !4mm on CT poses no significant risk of impingement and therefore can be considered safe. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs. http://dx.doi.org/10.1016/j.spinee.2014.08.370
P117. Adolescent Idiopathic Scoliosis Patients Are at Increased Risk for Pulmonary Hypertension which Reverses After Scoliosis Surgery Vishal Sarwahi, MD1, Rachel E. Borlack, BS2, Aviva Dworkin3, Dan Wang4, Sarika Kalantre, MD5; 1New York, NY, US; 2Bronx, NY, US; 3 Montefiore Medical Center, Bronx, NY, US; 4Albert Einstein College of Medicine, Bronx, NY, US; 5Children’s Hospital at Montefiore, Bronx, NY, US BACKGROUND CONTEXT: The incidence of structural cardiac disease and pulmonary hypertension in Adolescent Idiopathic Scoliosis (AIS) patients has been infrequently studied. Pulmonary hypertension has a high mortality rate. PURPOSE: The purpose of this study is to determine the incidence of structural cardiac anomalies and pulmonary hypertension in AIS patients and its relationship with curve severity. This is the first study to document evidence of pulmonary hypertension (pulm HT) in AIS patients, the severity of which directly correlates with the size of the curve. Pulmonary hypertension, which can potentially be fatal, reverts to normal after corrective scoliosis surgery. These findings provide direct evidence of immediate benefit of scoliosis surgery and can change the entire scoliosis treatment paradigm. STUDY DESIGN/SETTING: Retrospective study. PATIENT SAMPLE: 107 AIS patients whom had screening echocardiograms. OUTCOME MEASURES: Spearman correlation and Logistic Regression analysis. METHODS: Retrospective review of AIS pts with PSF from ‘09 –‘12 was done. 2D echos where reviewed for structural heart disease, aortic root size, and Tricuspid regurgitant jet velocity (TRV). Right ventricular systolic pressure (RVSP) was estimated using the Bernoulli’s equation (4*(TRV)2 þ right atrial pressure). RVSP O 25mm Hg was indicates pulmonary hypertension. 2D echo of 100 aged matched health adolescents served as control. RESULTS: 160 pts had spinal fusion surgery in the study period. Of these, 120 had AIS and 107 AIS pts (72F:35M) had screening 2D echos. Average age was 14.8 6 2.2 years. Average Cobb angle was 50.9612.3 . 2 AIS pts had ASD, 2 had VSD, and 3 had MVP, while 64 pts had mild to trivial mitral regurgitation. 24 AIS pts had higher incidence of mild tricuspid regurgitation (p!0.001) and higher TRV/ RVSP (O25 mm Hg) (p50.04) indicating pulmonary HT. Spearman correlation coefficient between Cobb angle and RVSP was 0.32 in AIS (p50.04). This is a significant correlation between increasing Cobb and worsening RVSP. Logistic Regression showed an odds ratio of 3.29 for elevated TRV (meaning increased pulmonary HT) in AIS (p 5 0.007).18 out of 24 AIS patients with elevated TRV/ RVSP had 2D echo at 2 year post-op. All had normal RVSP (mean 20.4 mm Hg), which shows reversal of pulmonary HT to normal values.
Refer to onsite Annual Meeting presentations and postmeeting proceedings for possible referenced figures and tables. Authors are responsible for accurately reporting disclosures and FDA device/drug status at time of abstract submission.