Faculty Bibliography

BACKGROUND CONTEXT: Age and pelvic incidence (PI) optimal alignment has been shown to minimize mechanical complications such as PJK. Low PI patients may be susceptible to overcorrection because PI specific alignment is not always prioritized. PURPOSE: The purpose of this study is to examine the incidence of over-correction in low PI ASD patients undergoing surgical intervention, and to quantify the impact of over-correction on radiographic PJK in this patient population. STUDY DESIGN/SETTING: Retrospective analysis of a prospective, multicenter database. PATIENT SAMPLE: Surgical ASD patients with low pelvic incidence. OUTCOME MEASURES: PJK defined as 1) proximal junctional angle (PJA, U

BACKGROUND CONTEXT: Operative treatment of adult spinal deformity (ASD) can be very challenging with high complication rates. Despite these challenges it's well established that pts benefit from such treatment. However, the surgical outcomes for pts with mild scoliosis and age appropriate sagittal alignment have not been reported. PURPOSE: To determine if patients (pts) with mild scoliosis and age appropriate sagittal alignment have favorable outcomes following surgical correction. STUDY DESIGN/SETTING: Retrospective review of a prospective, multicenter ASD database. PATIENT SAMPLE: ASD patients: operative pts age>=18, and all preoperartive pelvic tilt (PT), mismatch between pelvic incidence and lumbar lordosis (PI-LL), and C7 sagittal vertical axis (SVA) within established age adjusted parameters with minimum 2-year follow up. A subanalysis for pts with max coronal cobb angle 10-30degree (mild scoli) was done. OUTCOME MEASURES: Health-related quality of life (HRQOL) scores: Oswestry Disability Index (ODI), Short form-36(SF36), Scoliosis Research Society (SRS22), back/leg pain numerical rating scale (NRS) and minimum clinically important difference (MCID)/substantial clinical benefit (SCB). Radiographic values: max coronal cobb angle, coronal C7 plumb line, PT, PI-LL, thoracic kyphosis (TK), SVA. Demographic, frailty, surgical and complications data were collected.
METHOD(S): Two-year and baseline HRQOL/radiographic data were compared.
RESULT(S): A total of 103 pts were included from 667 operative patients (89.3% female, avg age 59.8+/-13.1yrs). Of the 103 pts, 29 (28.2%) had max preop coronal cobb angle 10-30degree. Two-year max coronal cobb angle and C7 coronal plumb were significantly improved compared to baseline (p<0.001 for both the overall cohort and mild scoli). All 2yr HRQOL measures were significantly improved compared to baseline(p<0.001) for both groups. 33.3-81.5%% of mild scoli pts met either MCID/SCB for all HRQOL. In mild scoli pts, 62.1% had min one complication, 27.6% had a major complication with 24.1% requiring a revision.
CONCLUSION(S): Pts with mild scoliosis and sagittal alignment within age appropriate parameters benefit from surgical correction at 2 years postop both radiographically and clinically including 81.5% meeting MCID for SRS pain despite having high complication rates. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright

BACKGROUND CONTEXT: Frailty is an increasingly recognized characteristic that has been validated across many studies as influencing operative risk. Utilization of frailty indices can allow for its identification of which spine patients may be too high risk for surgical intervention. This may be especially useful when it comes to surgeries that are minimally invasive and are supposed to have decrease perioperative outcomes. PURPOSE: Identify MIS techniques effects in postoperative outcomes in TLIF patients. STUDY DESIGN/SETTING: Retrospective review of a prospective database. PATIENT SAMPLE: TLIF spine patients. OUTCOME MEASURES: Complications, length of stay (LOS), estimated blood loss (EBL).
METHOD(S): Pts that underwent a lumbar spine procedure in a single-center Comprehensive Spine Quality Database. Pts were stratified based on procedural approach (Open [OP] and Minimally invasive Surgery [MIS]). Frailty was then calculated for each resultant group by using 30 variables with a validated method. Based on these scores, pts were categorized no frailty [NF]: <0.09, frail [F]: 0.09-0.18, and severe frailty [SF] >0.18. Groups were then controlled for surgical invasiveness. Chi-squared tests identified the relationship between complications and length of stay among various frailty states given surgical approach (OP vs MIS). These patients were propensity score matched for levels fused. Hospital acquired complications (HACs) were identified based on frailty groups through the use of chi-squared and t-tests for other surgical factors. A logistic regression analysis identified the association between frailty status and surgical, regarding postoperative (postop) outcomes.
RESULT(S): A total of 1,300 TLIF spine patients were isolated (59yrs, 29.3kg/m2). After PSM for levels fused, there were 338 pts for both MIS and OP. MIS pts were older (56.1 vs 53.3; p<0.05) than Op pts and had similar BMI's (29.1 vs 29.7; respectively). However, OP received more posterior approaches and less anterior approaches than MIS pts (p<0.05). By surgical factors: MIS and OP patients had similar LOS (3 vs 2.9days) and EBL (282.8 vs 251.5cc) but differed by Op time (195.7 vs 247.1; p<0.05) respectively. Further breakdown by frailty displayed statistical significance between MIS and OP patients with MIS pts having more F (16% vs 12%) and SF pts (4.3% vs 1.9%) than OP (all p<0.05). FMIS patients had lower postop neurologic complications as compared to FOP pts (4.63% vs 14.8%). However, SFMIS patiens had more post-operative complications than SFOP pts (55.2% vs 23.1%) and increased a pt's likelihood of being SFMIS by 5.4x's (all p<0.05).
CONCLUSION(S): This study displays that when frailty status is taken into account, TLIF MIS patients benefit from this procedure type when analyzed against neurologic complications. However, these patients were seen to suffer more from postop complications but did not differ on any other specific complications or surgical variables. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright

BACKGROUND CONTEXT: Prior literature has demonstrated that correction of sagittal plane deformity in adult patients has resulted in improvements in health-related quality of life (HRQOL) outcomes. In the absence of sagittal plane pathology, the effects of coronal malalignment under-correction in patients with spinal deformity have not been fully investigated. PURPOSE: To evaluate the impact of coronal malalignment correction on HRQOL outcomes in adult spinal deformity. STUDY DESIGN/SETTING: Retrospective review of a multicenter database. PATIENT SAMPLE: A total of 522 ASD patients had preoperative coronal malalignment greater than 40 mm. We excluded anyone who had SVA greater than 50 mm in order to control for patients without severe sagittal deformities. OUTCOME MEASURES: Our outcome measures included Oswestry Disability Index (ODI), SF-36 Physical Component Summary (PCS), and several other SF-36 and SRS-22r health domains scores.
METHOD(S): Using a prospective, multicenter database, we identified 1560 surgical patients. Of these, 522 patients had preoperative coronal malalignment greater than 40 mm. We excluded anyone who had SVA greater than 50 mm in order to control for patients who only had coronal plane deformity. We only included patients undergoing primary surgery. We then compared 2-year post HRQOL outcomes in patients that had their coronal malalignment corrected (CVA < 40mm) vs not.
RESULT(S): Mean age of patients was 54 +/- 15 years, 91% females. 79 patients were identified with only a coronal plane deformity undergoing a primary ASD surgery. Of these, 38 (48%) were under-corrected and 41 (52%) had their coronal alignment corrected to <40mm. Compared to the corrected group, the uncorrected group had a higher ODI (26.0+/- 2.9 vs 14.7+/- 2.5; p=0.002) and lower SRS-22r Activity (3.6+/- 0.14 vs 4.2+/- 0.11; p=002), SRS-22r Appearance (3.3+/- 0.16 vs 3.9+/- 0.12, p=.001), SRS-22r total (3.6+/- 0.12 vs 4.1+/- 0.11, p=.004), SF-36 Physical Component Summary (40.8+/- 1.3 vs 46.8+/- 1.6; p=.005), SF-36 Physical Function (40.5+/- 1.7 vs 46.0+/- 1.5, p=.01), SF-36 Bodily Pain (41.7+/- 1.6 vs 47.8+/- 1.5, p=.006), SF-36 General Health (47.2+/- 1.8 vs 52.2+/- 1.4, p=.03), SF-36 Social Functioning (45.9+/- 2.1 vs 51.7+/- 1.4, p=.03), SF-36 Mental Health (48.9+/- 1.9 vs 54.2+/- 1.8, p=.048) 2 years following index surgery.
CONCLUSION(S): Patients with coronal malalignment and little sagittal plane deformity experience worse improvement in pain and disability, with under-correction of their coronal plane deformity. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright

BACKGROUND CONTEXT: Thoracolumbar malalignment is often seen in patients presenting with cervical deformities. For operative cervical deformity (CD) patients, it is unknown whether certain thoracolumbar parameters play a large role in poor outcomes (complications, distal junctional kyphosis, reoperation) and whether addressment of such parameters is warranted. PURPOSE: To investigate the impact of cervical to thoracolumbar ratios on poor outcomes in CD corrective surgery. STUDY DESIGN/SETTING: Retrospective cohort study. PATIENT SAMPLE: 110 CD patients. OUTCOME MEASURES: Radiographic parameters: regionally and globally; complications; distal junctional kyphosis (DJK); reoperations; health-related quality-of-life (HRQLs): NDI, EQ5D, mJOA.
METHOD(S): Included: surgical CD pts (C2-C7 Cobb >10degree, CL>10degree, cSVA >4cm, or CBVA >25degree) with full baseline and 1-year data. Patients were assessed for ratios of preop cervical and global parameters including: C2 slope/T1 slope, TS-CL/PI-LL, cSVA/SVA. Deformity classification ratios of cervical (Ames-ISSG) to spinopelvic (SRS-Schwab) were investigated: cSVA modifier/SVA modifier, TS-CL modifier/PI-LL modifier. Cervical to thoracic ratios included C2-C7 lordosis/T4-T12 kyphosis. Correlations assessed the relationship between ratios and poor outcome (major complication, reoperation, HRQL decline or failure to meet MCID). Decision tree analysis through multiple iterations of multivariate regressions assessed cut-offs for ratios for acquiring suboptimal outcomes.
RESULT(S): A total of 110 cervical deformity patients were included in the present analysis (61.5+/-9.9 years, 66% female, 28.8+/-7.5 kg/m2). By approach, 18.2% underwent anterior-only procedures, 46.4% posterior, and 35.4% combined. Average levels fused: 7.7+/-3.7 levels (anterior: 3.5, posterior: 8.5). The average preoperative radiographic ratios assessed included a C2 slope/T1 slope 1.56, TS-CL/PI-LL of 11.1, cSVA/SVA of 5.4, CL/TK of 0.26. Ames-ISSG and SRS-Schwab modifier ratios of cSVA/SVA 0.1 and TS-CL/PI-LL of 0.35. Pearson correlations demonstrated a significant relationship between major complications and the baseline TS-CL/PI-LL with a cutoff of >12.72 (p=0.034), >0.482 Ames TS-CL/Schwab PI-LL modifiers (p=0.019), and the CL/TK ratios (>0.814, p=0.050). Reoperation had a significant correlation with the TS-CL/PI-LL (>5.819, p=0.009) and the cSVA/SVA (>3.79, p=0.002) ratios. Postoperative DJK had a correlation with the C2 slope/T1 slope (>1.59, p=0.017) and CL/TK (>0.692, p=0.0629) ratios. Not meeting MCID for NDI correlated with the CL/TK ratio (>1.402, p=0.016) and not meeting MCID for EQ5D correlated with the Ames TS-CL/Schwab PI-LL (>0.564, p=0.010).
CONCLUSION(S): Consideration of the ratio of distal regional to global alignment is a critical determinant of outcomes in cervical deformity corrective surgery. Several key ratios of cervical to global alignment were found to correlate with the occurrence of suboptimal realignment parameters, or poor clinical outcomes. A larger cervical lordosis to thoracic kyphosis was most representative of this risk, which predicted a complication, DJK, and not meeting MCID for NDI. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright

BACKGROUND CONTEXT: Lateral lumbar interbody fusion (LLIF) provides indirect decompression of the neural elements while minimizing the potential vascular complications associated with anterior lumbar interbody fusion (ALIF). Posterior fixation may be applied through various techniques such as conventional minimally invasive surgery (CMIS), requiring the patient to be repositioned prone to provide access to both pedicles. Conversely, robot-assisted navigation (RAN) of pedicle screws can be utilized from a single position without flipping the patient. RAN is theorized to reduce patient surgical time, radiation, and blood loss due to positioning and workflow effects. PURPOSE: To evaluate the effect of robot-assisted navigation in comparison to CMIS methods in terms of surgical time, radiation exposure, and pedicle screw accuracy. STUDY DESIGN/SETTING: Cadaveric study. PATIENT SAMPLE: N/A OUTCOME MEASURES: N/A METHODS: Twelve unembalmed human torsos were implanted with 2-level static LLIF cages, followed by posterior bilateral pedicle screw fixation using either CMIS (n=6) or RAN (n=6). Preoperative computed tomography (CT) RAN workflow utilized CT scans of the specimen taken offsite and transferred to the robotic system during setup. Screw planning was performed using these CT scans, and then was merged with intraoperative fluoroscopy. Surgical times, surgeon radiation exposure, and screw accuracy were measured. Patient flip time from a consecutive patient series was included.
RESULT(S): Significant differences in surgical times and radiation dosages were found between groups. Surgical time for preoperative RAN and CMIS was 64.7 min+/-4.1 min and 123.0 min+/-13.7 min, respectively. Time per screw for RAN and CMIS workflows was 2.7+/-0.6 min and 4.3+/-1.3 min, respectively. RAN was significantly different for total operative time and time per screw in comparison to CMIS (p<0.05). Radiation dosages and times were separated into interbody and posterior fixation procedures separately, and sorted by imaging workflow. RAN and CMIS radiation dosages during posterior fixation were 0.4+/-0.2 rad and 2.7+/-1.6, respectively (p<0.05). Screw accuracy was as follows: CMIS resulted in 4 breaches (11% breach rate), while RAN resulted in a single breach (3% breach rate).
CONCLUSION(S): Significant differences were found in both surgical time and radiation exposure between CMIS and RAN, with RAN resulting in shorter surgical times and less radiation exposure to the surgeon than CMIS. Consideration should be given to single-position LLIF procedures that utilize RAN to instrument the spine with bilateral pedicle screws. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright

BACKGROUND CONTEXT: Age-adjusted alignment targets for adult spinal deformity (ASD) patients have the potential to reduce the incidence of PJK while ensuring optimal HRQL. Previous studies demonstrated the interplay between lumbar lordosis (LL) and thoracic kyphosis (TK) and their relationship with pelvic morphology as measured by the plevic incidence (PI). In clinical practice, reaching this ideal alignment remains challenging as the relationship between lordosis and kyphosis is not clearly elucidated. PURPOSE: This study aimed at developing a pragmatic formula on how much lumbar lordosis is needed based on the patient age, PI and exiting thoracic kyphosis. STUDY DESIGN/SETTING: Multicenter retrospective review of a prospective database. PATIENT SAMPLE: A total of 347 adult spinal deformity patients reaching age-adjusted alignment at 1-year post surgery. OUTCOME MEASURES: Sagittal alignment and internal validation of predictive formula.
METHOD(S): Surgical ASD patients reaching an age-adjusted ideal alignment at one year were identified. Multilinear regressions analysis was used to identify the relationship between regional curvatures (LL &TK) permitting to reach a given global alignment (TPA) based on pelvic incidence.
RESULT(S): The 347 patients included (60 years old, 72% female, BMI 29+/-6.2) had a significant improvement in all sagittal parameters from pre-op to 1Y (p<0.001 except PI). Multilinear regression predicting L1-S1 based on TK, TPA and PI demonstrated excellent results (R2=0.85). Similar results were found when regressions were conducted for each TPA percentile group (R2 ranging from 0.83 to 0.87). Simplification of the coefficients of prediction led to the following equation: LL = PI + 0.3

BACKGROUND CONTEXT: Although researchers have extensively studied factors predicting clinical outcomes at static time points, assessing rate of recovery after adult spinal deformity (ASD) surgery has largely been ignored. This study aims to address this gap in knowledge by evaluating the impact of frailty and invasiveness on recovery kinetics, using area-under-the-curve (AUC) methodology. PURPOSE: To assess the impact of patient specific and surgical factors on postoperative recovery kinetics. STUDY DESIGN/SETTING: Retrospective review of a prospective, multicenter database. PATIENT SAMPLE: A total of 320 patients were identified from a multicenter database who had minimum 2-year HRQOL follow-up, with preoperative, 6-week and 1-year data available. OUTCOME MEASURES: Our primary outcome measure was integrated health state (IHS) score, a marker of postoperative recovery.
METHOD(S): ASD patients with minimum 2-year follow-up were stratified by frailty and surgical invasiveness. Previously validated ASD-FI scores were used to separate non-frail (<.3) patients from those that there were frail (.3 to.5) and severely frail (>.5). Patients were also stratified by surgical inverness, using ASD-SR, into four quartiles, Q1: <65, Q2: 66-89, Q3: 90-119, Q4: >120. Patient demographics, BMI, CCI and surgical parameters were also collected. To assess recovery kinetics, SRS-22r and ODI scores at 6-weeks, 1-year and 2-year were normalized against preoperative values and graphed as a function of time. AUC was summed across all time points to generate a single IHS score. Multivariate linear regression was used with IHS scores as primary outcome variable.
RESULT(S): A total of 320 patients met the inclusion and exclusion criteria. The mean (SD) patient age was 58.6 (14.7) with 79% female. Overall, 139 were non-frail, 131 frail and 46 severely frail. On univariate analysis, frail and severely frail patients were noted to have worse baseline and 2-year HRQOL scores for SRS pain, activity and ODI; however, when comparing differences in HRQOL across this 2-year period, F and SF were noted to have greater improvements in both SRS and ODI (p<.05). On multivariate regression, frail and severely frail patients, compared to those non-frail, were found to have better IHS scores for ODI, SRS-22r pain, and SRS-22r activity, indicating more favorable recovery (p<.05). In particular, for SRS-22r activity, frail (adjusted beta: 0.37, p=<.01) and severely frail (adjusted beta: 0.74, p=<.01) patients were found to have higher IHS compared to their non-frail counterparts. Similarly, for SRS-22r pain, frail and severely frail patients showed improved recovery with higher IHS scores in comparison to non-frail patients. In contrast to frailty, operative variables, including surgical invasiveness and EBL, were insignificant predictors of IHS scores for either ODI or SRS-22r domains.
CONCLUSION(S): Our results suggest that patient-specific factors, namely frailty, play a larger role in predicting postoperative recovery kinetics, in comparison to surgical factors, which appear to have limited if any impact. Despite frail patients having lower preoperative and 2-year HRQOL scores, they were noted to have higher IHS scores SRS pain, activity, and ODI indicating more favorable recovery. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright

BACKGROUND CONTEXT: The choice of surgical approach in CD surgery is often dictated by surgeon preference and experience. This choice could significantly impact the costs and outcomes of an operation, therefore the approaches should be analyzed in order to determine the optimal approach from a cost-utility perspective. The cost utility of different surgical approaches in cervical deformity (CD) has not been investigated in the literature. PURPOSE: Investigate the cost utility of differing approaches in operative CD patients. STUDY DESIGN/SETTING: Retrospective review of a prospective multicenter cervical deformity database. PATIENT SAMPLE: A total of 105 CD patients. OUTCOME MEASURES: Costs, EuroQol-5D (EQ-5D), Quality adjusted life years (QALYs), Cost per quality adjusted life years.
METHOD(S): Included CD patients (C2-C7 Cobb>10degreeor CK>10degree, cSVA>4cm or CBVA>25degree) >18yr with follow-up (1-year) surgical and health related quality of life scores. Costs were calculated using the PearlDiver database, which reflects both private insurance and Medicare reimbursement claims. QALYs and cost per QALY were calculated using a 3% discount rate to account for residual decline to life expectancy (78.7 years). After accounting for complications, LOS, revisions, and death, cost per QALY at 1Y and life expectancy [LE] were calculated for surgical approach (anterior-only, posterior-only [excluding PSO and VCR to account for differences in instrumentation], combined). In a subanalysis, approach groups were propensity-score matched for TS-CL to account for baseline (BL) deformity.
RESULT(S): A total of 105 CD patients met inclusion criteria (61.9 yrs, 63% female, 28.6kg/m2, CCI: 0.97). By approach, 21.9% underwent anterior only, 37.1% posterior only and 41% combined approaches. Average number of levels fused was 6.9, with a mean EBL of 948 ml and total operative time of 544.2 minutes. Mean EQ5D at BL was 0.74+/-0.07 and at 1Y was 0.79+/-0.08 (a difference of 0.05+/-0.08). Average difference in EQ5D from BL to 1Y was significant (p=0.002) across approach: 0.093 anterior-only, 0.021 posterior-only, 0.044 combined. 13% (3) of anterior-only patients underwent a revision, 10.3% (4) of posterior and 13.9% (6) of combined approaches. The average costs per surgery for CD patients at 1-year undergoing surgery by anterior approach was $27,640.75, $38,499.44 posterior-only, and $36,553.41 combined approach (p>0.05).The cost per QALY was higher for posterior-only patients at 1-year ($948,946.81) compared to anterior-only ($152,616.65) and combined ($424,110.14), p<0.001. If the utility gained was sustained to life expectancy, the cost per QALY for the anterior-only group was $21,665.87, posterior-only was $134,715.06 and combined approach was $60,207.82., p<0.001. After PSM for TS-CL, 15 patients remained in each group. The cost per QALY remained higher for posterior-only patients at 1-year and LE (both p<0.050).
CONCLUSION(S): After accounting for comorbidities, complications, revisions, and death, all surgical approaches showed improvement in postoperative EQ5D scores, however posterior approach demonstrated overall lower cost effectiveness. CD patients who underwent anterior-only approach had the lowest average costs for CD corrective surgery, as well as the lowest cost per QALY (best cost-effectiveness) compared to posterior and combined approaches. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright

BACKGROUND CONTEXT: Proximal junctional failure (PJF) is a common and particularly adverse complication of adult spinal deformity (ASD) surgery. There is evidence that the rigidity of posterior spinal constructs may impact risk of PJF. PURPOSE: We hypothesized that lower mean screws per level and decreased rod stiffness would be associated with lower incidence of PJF. STUDY DESIGN/SETTING: Retrospective cohort study. PATIENT SAMPLE: Patients with ASD and 2-year minimum follow-up were included. Only patients undergoing fusion of >=5 levels, and with LIV at the sacro-pelvis were included. Patients undergoing revision surgery were excluded. In total, 420 patients were analyzed. OUTCOME MEASURES: The primary outcome variable was PJF, defined using previously published radiographic criteria (PJ angle >28degreeand PJ angle >22degree, and >=8mm/>=3mm listhesis at upper thoracic / thoracolumbar levels, respectively).
METHOD(S): The primary independent variables were the mean number of screws per level fused analyzed with a cutoff of 1.8 (determined by ROC analysis) and rod material/diameter. Multivariable logistic regression was utilized to investigate confounding factors, including age, history of osteoporosis, BMI, gender, CCI, preoperative Schwab modifiers, preoperative TPA, postoperative change in lumbar lordosis, upper instrumented vertebra, osteotomy, approach, UIV type (ie, pedicle screw vs other), and number of levels fused.
RESULT(S): Of the total patients, 78.8% were female. PJF occurred in 14.1% of patients. The mean screws per level was 1.7 (SD 0.2), and 57.6% of patients had <1.8 screws per level. PJF occurred in 19.4% vs 9.8% of patients with >=1.8 vs <1.8 screws per level, respectively (p<0.01). In multivariable analysis, patients with <1.8 screws per level exhibited lower odds of PJF (OR 0.39, p<0.01). Rod material and diameter (both p>0.2) were not significantly associated with PJF. Screw density specifically adjacent to the UIV was not related to PJF (p>0.2).
CONCLUSION(S): Among ASD patients undergoing long-segment primary fusion to the pelvis, the risk of PJF was lower among patients with <1.8 screws per level. Rod diameter and material, however, were not significantly associated with PJF. This finding may be related to construct rigidity. It is possible that residual confounding by other patient and surgeon-specific characteristics may exist. Further biomechanical and clinical studies exploring the relationship between screw density and PJK/PJF are warranted. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
Copyright