Faculty Bibliography

BACKGROUND CONTEXT: Surgeons may preferentially limit fusion levels for younger vs older ASD patients to maintain motion segments and optimize postoperative function. Few data exist comparing the functional impact of upper thoracic (UT) vs thoracolumbar (TL) upper instrumented vertebra (UIV) in younger vs older ASD patients undergoing long fusion to the pelvis. PURPOSE: Evaluate patient reported functional impact of UT vs TL UIV in younger vs older ASD patients undergoing long fusion to the pelvis. STUDY DESIGN/SETTING: Propensity score matched (PSM) analysis of ASD patients prospectively enrolled into a multicenter study. PATIENT SAMPLE: Surgically treated ASD patients prospectively enrolled into multicenter study. OUTCOME MEASURES: Numeric rating scale (NRS) back and leg pain, Scoliosis Research Society-22r questionnaire (SRS-22r), Short Form-36v2 questionnaire (SF-36), Oswestry Disability Index (ODI), estimated blood loss, duration of hospital stay, postoperative complications, revision spine surgery.
METHOD(S): Surgically treated ASD patients prospectively enrolled into a multicenter ASD study were divided into 2 age groups (younger= <65 years, older= > 65 years) and separated according to UIV (TL= L2-T7; UT= T6-T1). Study inclusion criteria; 1) surgery for Lumbar (L), Sagittal (S), or Mixed (M) deformities (as per SRS-Schwab ASD classification), 2) fusion to the pelvis, 3) minimum 5 levels fused, and 4) minimum 2 year postop follow up. Surgery for double major or thoracic scoliosis were excluded. PSM was used to match preop patient demographics, scoliosis, and sagittal spinopelvic parameters including PI-LL, TK, SVS, and TPA. Surgical data evaluated and impact of UIV upon patient reported functional outcomes compared for UT vs TL for younger vs older.
RESULT(S): From 2008-2018, 435 of 717 eligible surgically treated patients were evaluated; younger (n=193; mean age 57.6 years) and older (n=242; mean age 72.3 years), mean levels fused UT=17.4, TL=10.7 (p<0.05). Preop spine deformity, demographics, and performance of osteotomies were similar for matched UT vs TL in younger and older (p>0.05). Surgical blood loss, duration of SICU and hospital stay was greater for UT vs TL in younger and older (p<0.05). UT had more revision surgery than TL due to implant failures in younger (20% vs 3%) and older (16% vs 1%), respectively (p<0.05). Older UT had more major complications than older TL (65% vs 30%). At minimum 2 year postoperative follow up spine deformity correction and all PROMs (including improvements and final values) including SRS-22r activity, SF-36 physical function, SF-36 role physical, SF-36 social function and SF-36 vitality were similar UT vs TL in younger and older (p>0.05).
CONCLUSION(S): Younger ASD patients fused to the pelvis do not report more physical restrictions for UT vs TL UIV compared to older ASD patients, however blood loss, SICU and hospital stay and complications were greater for UT vs TL in younger and older cohorts. When deciding upon UIV for ASD patients, the minimal impact of UT vs TL UIV upon patient reported outcomes must be offset by cognizance of a longer hospital stay and potential for greater postoperative complications for UT fusions especially in older patients. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Reoperations following adult spinal deformity (ASD) surgery place a significant burden on patient quality of life and overall health care costs. Despite the common knowledge of frequently occurring complications following ASD surgery that require reoperation, little is known on the cost and timing of these complications. Attempts to optimize the cost effectiveness of ASD surgery requires careful examination of the overall impact, frequency and timing of complications requiring reoperation on total cost of care. PURPOSE: The primary aim of our study was to ascertain the percentage of total cost of care attributed to reoperations, identify the costliest complications requiring reoperation following index surgery and to determine the timing of these complications. STUDY DESIGN/SETTING: Retrospective analysis of a prospective, multicenter study. PATIENT SAMPLE: ASD patients with >4 level fusion and eligible for minimum 2-year follow-up were included. OUTCOME MEASURES: Reoperation rates, Total cost of care.
METHOD(S): ASD patients with >4 level fusion with 2-year follow-up were included. Index and total episode of care (EOC) costs were calculated using Medicare's inpatient prospective payment system (IPPS) for MS-DRGs 453-460 and adjusted for inflation to 2020 real dollars. QALYs gained were calculated using baseline, 1-year, and 2-year SF-6D scores. Complication categories included: PJK (proximal junctional kyphosis), adjacent segment disease, pseudarthrosis, neurologic complications, malignment, implant malposition, and infections.
RESULT(S): DRG data for index and revision surgery was available for 505/889 patients. Mean age was 62.5+12.4 years, 76% women. Eighty-nine patients (18%) required a total of 114 reoperations (range 1-5 per patient). The mean index EOC for the whole cohort was $72,718, compared to a mean cost of $59,130 for each reoperation. Accounting for all reoperations, the tEOC in the revision group was 2.1-times higher than the non-revision group ($151,913 vs $71,978, p<0.0001). The 2-year QALY gain in the revision group was significantly higher than the non-revision group (0.08 vs 0.03, p<0.01). The two most common complications requiring reoperations were PJK (41.2%) and pseudarthrosis (36.8%). Reoperations for PJK and pseudoarthrosis collectively accounted for 77% of reoperation costs, but the majority (53%) occurred after 2 years of index surgery. Infections, implant malposition, or neurologic complications (33% each) were most common requiring reoperations within 30 days of index surgery.
CONCLUSION(S): PJK and pseudarthrosis were the two most common complications requiring reoperation and most occurred most frequently over 2 years after index surgery. Collectively, they contributed to 77% of the total reoperation costs. Efforts to optimize the cost effectiveness of ASD surgery should focus on effective methods to mitigate risk of PJK and pseudarthrosis. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Few studies investigate fractional curve correction after long fusion with transforaminal (TLIF) vs anterior lumbar interbody fusion (ALIF) for adult symptomatic thoracolumbar/lumbar scoliosis (ASLS). PURPOSE: Our objective was to compare fractional correction, health-related quality-of-life (HRQL), and complications associated with L4-S1 TLIF vs ALIF in ASLS operative treatment. STUDY DESIGN/SETTING: Retrospective review of a prospectively collected multicenter consecutive case registry. PATIENT SAMPLE: Database enrollment required age >=18 years, scoliosis >=20, sagittal vertical axis (SVA) >=5cm, pelvic tilt >=25, or thoracic kyphosis >=60. OUTCOME MEASURES: Radiographic correction (including L4-S1 fractional curve), HRQL (Oswestry Disability Index [ODI], Short Form-36 [SF-36] scores, Scoliosis Research Society-22 [SRS-22r] scores), and complications.
METHOD(S): Prospective multicenter data was reviewed. Study inclusion required fractional curve >=10degree, thoracolumbar/lumbar curve >=30degree, index TLIF vs ALIF at L4-L5 and/or L5-S1, and minimum 2-year follow-up. TLIF and ALIF patients were propensity-matched using number and type of interbody fusion at L4-S1.
RESULT(S): Of 135 potentially eligible consecutive patients, 106 (78.5%) achieved minimum 2-year follow-up (age=60.6+/-9.3years, women=85.8%, TLIF=44.3%, ALIF=55.7%). Index operations had 12.2+/-3.6 posterior levels, iliac fixation=86.8%, and TLIF/ALIF at L4-L5 (67.0%) and L5-S1 (84.0%). ALIF had greater cage height (10.9+/-2.1 vs 14.5+/-3.0mm, p=0.001) and lordosis (6.3degree+/-1.6degree vs 17.0degree+/-9.9degree, p=0.001) and longer operative duration (6.7+/-1.5 vs 8.9+/-2.5hrs, p<0.001). Final alignment improved significantly (p<0.05): fractional curve (20.2degree+/-7.0degree to 6.9degree+/-5.2degree), maximum coronal Cobb (55.0degree+/-14.8degree to 23.9degree+/-14.3degree), C7-sagittal vertical axis (5.1+/-6.2 to 2.3+/-5.4cm), pelvic tilt (24.6degree+/-8.1degree to 22.7degree+/-9.5degree), and lumbar lordosis (32.3degree+/-18.8degree to 51.4degree+/-14.1degree). Matched analysis demonstrated comparable fractional correction (TLIF=-13.6degree+/-6.7degree vs ALIF=-13.6degree+/-8.1degree, p=0.982). Final HRQL improved significantly (p<0.05): ODI (42.4+/-16.3 to 24.2+/-19.9), SF-36 Physical Component Summary (PCS, 32.6+/-9.3 to 41.3+/-11.7), SRS-22r (2.9+/-0.6 to 3.7+/-0.7). Matched analysis demonstrated worse ODI (30.9+/-21.1 vs 17.9+/-17.1, p=0.017) and PCS (38.3+/-12.0 vs 45.3+/-10.1, p=0.020) for TLIF at last follow-up (despite no difference in these parameters at baseline). Total complication rate per patient was not different (TLIF=76.6% vs ALIF=71.2%, p=0.530), but significantly more TLIF patients had rod fractures (RF) (TLIF=28.6% vs ALIF=7.1%, p=0.036). Multiple regression demonstrated 1-mm increase in L4-L5 TLIF cage height lead to 2.2degree reduction in L4 coronal tilt (p=0.011), and 1degree increase in L5-S1 ALIF cage lordosis lead to 0.4degree increase in L5-S1 segmental lordosis (p=0.045).
CONCLUSION(S): Operative ASLS treatment with L4-S1 TLIF vs ALIF demonstrated comparable fractional curve correction (66.7% vs 64.8%) despite significantly larger, more lordotic ALIF cages. TLIF cage height had significant impact on leveling L4 coronal tilt, whereas ALIF cage lordosis had significant impact on lumbosacral lordosis restoration. Advantages of TLIF may include reduced operative duration; however, associated HRQL was inferior and more RFs were detected in this study. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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OBJECTIVE:Malalignment of the cervical spine can result in cord compression, leading to a myelopathy diagnosis. Whether deformity or myelopathy severity is stronger predictors of surgical outcomes is understudied. METHODS:Surgical cervical deformity (CD) patients with baseline (BL) and up to 1-year data were included. Modified Japanese Orthopaedic Association (mJOA) score categorized BL myelopathy (mJOA = 18 excluded), with moderate myelopathy mJOA being 12 to 17 and severe myelopathy being less than 12. BL deformity severity was categorized using the mismatch between T1 slope and cervical lordosis (TS-CL), with CL being the angle between the lower endplates of C2 and C7. Moderate deformity was TS-CL less than or equal to 25° and severe deformity was greater than 25°. Categorizations were combined into 4 groups: group 1 (G1), severe myelopathy and severe deformity; group 2 (G2), severe myelopathy and moderate deformity; group 3 (G3), moderate myelopathy and moderate deformity; group 4 (G4), moderate myelopathy and severe deformity. Univariate analyses determined whether myelopathy or deformity had greater impact on outcomes. RESULTS:One hundred twenty-eight CD patients were included (mean age, 56.5 years; 46% female; body mass index, 30.4 kg/m2) with a BL mJOA score of 12.8 ± 2.7 and mean TS-CL of 25.9° ± 16.1°. G1 consisted of 11.1% of our CD population, with 21% in G2, 34.6% in G3, and 33.3% in G4. At BL, Neck Disability Index (NDI) was greatest in G2 (p = 0.011). G4 had the lowest EuroQol-5D (EQ-5D) (p < 0.001). Neurologic exam factors were greater in severe myelopathy (p < 0.050). At 1-year, severe deformity met minimum clinically important differences (MCIDs) for NDI more than moderate deformity (p = 0.002). G2 had significantly worse outcomes compared to G4 by 1-year NDI (p = 0.004), EQ-5D (p = 0.028), Numerical Rating Scale neck (p = 0.046), and MCID for NDI (p = 0.001). CONCLUSION/CONCLUSIONS:Addressing severe deformity had increased clinical weight in improving patient-reported outcomes compared to addressing severe myelopathy.

BACKGROUND CONTEXT: Few guidelines exist regarding appropriate upper instrumented vertebra (UIV) selection for adult spinal deformity (ASD) patients undergoing long fusion to the pelvis. Fusion to upper thoracic (UT) spine may provide greater deformity correction and reduce proximal junctional failure (PJF) rates compared to fusions terminating at the thoracolumbar (TL) spine. Previous reports comparing outcomes for UT vs TL UIV for ASD surgery are confounded by discrepant patient cohorts. PSM analyses can be used to reduce selection bias and mimic patient randomization. PURPOSE: Use a propensity score matched (PSM) analysis to compare surgical and hospital data, deformity correction, complication rates, and patient reported outcomes (PROs) for demographically and radiographically matched ASD patients receiving TL vs UT UIV. STUDY DESIGN/SETTING: PSM analysis of ASD patients prospectively enrolled into a multicenter study. PATIENT SAMPLE: Surgically treated ASD patients. OUTCOME MEASURES: Numeric rating scale (NRS) back and leg pain, Scoliosis Research Society-22r questionnaire (SRS-22r), Short Form-36v2 questionnaire (SF-36), Oswestry Disability Index (ODI), estimated blood loss, duration of hospital stay, postoperative complications, revision spine surgery, PJF.
Method(s): ASD patients prospectively enrolled into a multicenter study from 2009-2018 were classified according to SRS-Schwab ASD Types. Study inclusion; 1) surgery for lumbar (L), sagittal (S) or mixed (M) deformities, 2) fusion to pelvis, 3) >=5 levels fused, 4) >=2 year follow up. Study exclusion; double major or thoracic scoliosis, thoracic hyperkyphosis (>70degree). UIV cohorts formed based on bimodal UIV distribution (TL=L2-T8 vs UT=T6-T1). PSM matched TL and UT for preop demographics, scoliosis, PI-LL, TK, SVA, TPA and osteotomies. Postop deformity correction, complications, and PROs were compared for UT vs TL in L, M, S deformities.
Result(s): Of 699 eligible patients, 417 (L [n=70], S [n=166] and M [n=198]) were evaluated. UT and TL had similar preop age, frailty, spine deformity, follow up, osteotomies performed (p>0.05). UT had greater blood loss in L and M deformities, greater SICU admissions for L and S, longer hospital and greater revision surgery for implant failures for all deformities than TL (p<0.05). UT had fewer PJF for L deformities (p<0.05). Deformity correction and PROM improvement was similar UT vs TL for all cohorts at last follow up (p>0.05).
Conclusion(s): The theoretical benefits of UT fusion were not demonstrated for matched L, S and M patients receiving long fusion to the pelvis. UT had greater blood loss, hospital stay and revision surgery for implant failures than TL. For select deformities surgeons should consider TL UIV rather than UT; however, more research is needed to determine best outcomes for fusion levels for ASD. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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OBJECTIVE:To prioritize the cervical parameter targets for alignment. METHODS:Included: cervical deformity (CD) patients (C2-7 Cobb angle > 10°, cervical lordosis > 10°, cervical sagittal vertical axis [cSVA] > 4 cm, or chin-brow vertical angle > 25°) with full baseline (BL) and 1-year (1Y) radiographic parameters and Neck Disability Index (NDI) scores; patients with cervical [C] or cervicothoracic [CT] Primary Driver Ames type. Patients with BL Ames classified as low CD for both parameters of cSVA ( < 4 cm) and T1 slope minus cervical lordosis (TS-CL) ( < 15°) were excluded. Patients assessed: meeting minimum clinically important differences (MCID) for NDI ( < -15 ΔNDI). Ratios of correction were found for regional parameters categorized by primary Ames driver (C or CT). Decision tree analysis assessed cutoffs for differences associated with meeting NDI MCID at 1Y. RESULTS:Seventy-seven CD patients (mean age, 62.1 years; 64% female; body mass index, 28.8 kg/m2). Forty-one point six percent of patients met MCID for NDI. A backwards linear regression model including radiographic differences as predictors from BL to 1Y for meeting MCID for NDI demonstrated an R2 of 0.820 (p = 0.032) included TS-CL, cSVA, McGregor's slope (MGS), C2 sacral slope, C2-T3 angle, C2-T3 SVA, cervical lordosis. By primary Ames driver, 67.5% of patients were C, and 32.5% CT. Ratios of change in predictors for MCID NDI patients for C and CT were not significant between the 2 groups (p > 0.050). Decision tree analysis determined cutoffs for radiographic change, prioritizing in the following order: ≥ 42.5° C2-T3 angle, > 35.4° cervical lordosis, < -31.76° C2 slope, < -11.57-mm cSVA, < -2.16° MGS, > -30.8-mm C2-T3 SVA, and ≤ -33.6° TS-CL. CONCLUSION/CONCLUSIONS:Certain ratios of correction of cervical parameters contribute to improving neck disability. Prioritizing these radiographic alignment parameters may help optimize patient-reported outcomes for patients undergoing CD surgery.

BACKGROUND CONTEXT: A previous study by Pellise et al identified that a lowest instrumented vertebrae (LIV) at the pelvis, frailty, and sagittal deformity (global sagittal alignment [SVA], lordosis gap [PI-LL], T1 sagittal tilt [T1Slope]) were strong preoperative predictors of major complications. In addition to the preoperative predictors, blood loss and surgical time were strong predictors that occur operatively. It is unknown whether being at risk by these criteria has an effect on cost of surgery. PURPOSE: To determine whether previously established risk stratification criteria will reduce operative costs. STUDY DESIGN/SETTING: Retrospective cohort study of a prospectively collected multicenter ASD database. PATIENT SAMPLE: This study included 952 ASD patients. OUTCOME MEASURES: Health-related quality of life measures (HRQLs), quality adjusted life years (QALYs), utility gained, ODI, total cost.
METHOD(S): Adult spinal deformity (ASD) patients with complete baseline (BL) and 2-year (2Y) HRQLs and radiographic data were included. Frailty score, sagittal deformity measures, blood loss, and surgical time were divided into tertiles, with the highest tertile being high risk. Published methods converted ODI to SF-6D. QALYs utilized a 3% discount rate for residual decline to life expectancy (LE, 78.7 years). Cost was calculated using the PearlDiver database and assessed for complications/major complications and comorbidities according to CMS.gov definitions. Cost per QALY at 2Y and LE were calculated for additive risk factors (LIV at pelvis, high frailty, any high sagittal deformity measure, high blood loss, high surgical time). These costs represented national averages of Medicare pay-scales for services within a 30-day window including length of stay and death differentiated by complication/comorbidity, revision, and surgical approach. Internal cost data were based on individual patient DRG codes.
RESULT(S): Of 926 patients included, 118 did not meet any risk criteria, 171 met 1, 207 met 2, 151 met 3, 56 met 4, and 3 met 5 (these 3 patients were excluded due to small sample size). There was a significant trend (R2=0.897) in terms of national average cost at 2-years with increasing amount of risk measures met, as cost increased by $11,566 with each additional risk factor. Amount of risk factors met had a positive correlation to baseline ODI (0: 30.89; 1: 39.66; 2: 46.96; 3: 51.59; 4: 54.69; p<0.001) and 2Y ODI (0: 18.06; 1: 22.55; 2: 27.53; 3: 34.23; 4: 38.54; p<0.001). When analyzing initial surgical cost by DRG code, there was a $3,844 increase in cost per risk factor (R2=0.8703). Patients meeting 2 risk factors had the highest ODI improvement from BL to 2Y (p=0.06). QALYs gained at LE decreased by 0.0756 per risk factor (R2=0.8153). National average cost per QALY at 2Y increased by $45,852 per risk factor (R2=0.4151), and cost per QALY at LE increased by $15,759 per risk factor (R2=0.8822).
CONCLUSION(S): Increasing risk factors involving frailty, baseline deformity, and operative factors reduce cost effectiveness by increasing total cost and reducing QALYs. Preoperative or intraoperative measures to reduce a patient's amount of applicable risk factors would concurrently reduce operative cost and improve cost-effectiveness. Awareness of non-modifiable risk factors may also help educate surgical approach. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Since circumferential adult spinal deformity (ASD) surgery can lead to high surgical burden for the patient, surgeons may elect to stage these procedures during the same hospitalization. As a result, there is a trend toward planning same-hospitalization staged ASD surgeries by performing an anterior lumbar interbody fusion (ALIF) prior to a subsequent staged posterior fusion. PURPOSE: The aim of this study was to determine optimal timing for staging (early vs delayed) thoracolumbar ASD surgery within the same hospitalization. STUDY DESIGN/SETTING: Retrospective review of a multicenter database. PATIENT SAMPLE: A total of 158 surgical ASD patients undergoing anterior and staged posterior spinal fusion >=5 levels. OUTCOME MEASURES: Our outcome measures were 90-day complication rates, postoperative alignment, and 2-year ODI.
METHOD(S): Using a prospective, multicenter database, we identified 158 surgical ASD patients undergoing first an anterior surgery followed by a staged posterior spinal fusion >=5 levels during the same hospitalization. Stratum-specific likelihood ratio (SSLR) analysis was performed to calculate a cutoff point beyond which 90-day complications were increased. The cutoff generated through SSLR were confirmed with multivariable logistic regression analysis controlling for age, gender, levels fused for each stage, preoperative alignment, three-column osteotomy, and Charlson Comorbidity Index. The outcome measures were 90-day complication rates, postoperative alignment, and 2-year ODI. Multivariable analyses were performed with logistic, Poisson and linear regressions where appropriate.
RESULT(S): Utilization of staged procedures increased 4x from 2008-2019, and the mean staging interval was 3 days (range 1-8). On SSLR analysis, patients were divided into two staging categories based on complication risk: early (<6 days, range 1-5, N=139) versus delayed (>= 6 day, range 6-8, N=19). On bivariate analysis, the delayed group had higher 90-day complication rates (68.4% vs 32.4%, p=0.002) and longer operative times (638 min vs 739 min, p=0.020) relative to the early group. Adjusting for covariates on multivariable analysis, patients with delayed staging had significantly greater odds of 90-day complications (OR=7.57, p=0.006), and longer total operative time (beta=119, p=0.035). With respect to specific complications, delayed staging carries increased odds of infection compared to early staging (OR=11.8 p=0.031). There were no significant differences in postoperative alignment or 2-year ODI between the groups (p>0.05 for all).
CONCLUSION(S): Compared to early staging (< 6 days) of ALIF and subsequent staged posterior fusion, delayed staging (>= 6 days) is associated with greater odds of 90-day complications, particularly infection. With the growing trend toward staged ASD surgeries, efforts should be made to shorten the interval between ALIF and subsequent posterior fusion. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: As ASD prevalence increases in our ever-aging population there is a hypothetical concomitant increase in poor bone quality, especially if not recognized and not treated. ASD surgery is expensive and carries a high complication profile. It is important to optimize surgical outcomes and reduce complications especially if modifiable preoperative risk factors can be identified, such as osteoporosis. Additional diagnostic modalities such as a DEXA can add cost, delay diagnosis, and can be an additional insurance hurdle. PURPOSE: Our goal was to examine the utility of HU measurement on preoperative CTs for bone health assessment. STUDY DESIGN/SETTING: Retrospective cross-sectional review of a prospective, multicenter ASD cohort. PATIENT SAMPLE: Surgical ASD patients. OUTCOME MEASURES: Hounsfield Units, history of osteoporosis, DEXA results.
METHOD(S): Operative ASD patients (scoliosis >20, SVA>5cm, PT>25, or TK>60) were included if they had a preoperative CT. HU were measured by each participating site from axial views within the cancellous body (x3: top, middle, bottom) at both L1 and future UIV. Reliability of the measurement between the 3 acquisitions was performed using instar-class correlation for absolute agreement. Association between HU and patient demographics was assess using Pearson's correlation. Finally, correlation between DEXA measurement and HU was conducted to evaluate relationship between bone quality and HU values.
RESULT(S): There were 694/1493 (46%) patients who had a CT including either L1 or UIV. And 521 patients were identified as having both L1 and UIV measurement. Also, 71.8% were female with a mean age of 63years+/-12.5, 52.6% were revision with mean levels fused of 10.5+/-4.5. The intraclass correlation coefficient (ICC) for UIV and L1 were 0.767 (95CI 0.737-0.796]) and 0.802 (95CI [0.774 0.827]), respectively. Previous instrumentation did not affect L1 HU ICC (r=0.798 vs r=0.809) and showed no significant difference in HU value (p=0.232). Comparison of L1 HU between different sites demonstrated no significant difference (p=0.43). Comparison of L1 and UIV did show a significant difference (L1:151+/-77 vs 160+/-62 p<0.001) although there was a significant correlation (r=0.631 p<0.001). The mean HU value at L1 was consistent with previously published values (p=0.542). There were 116 (22.5%) patients who had a DEXA and 97 (18.6%) patients reported a history of osteoporosis. Comparison of DEXA and HU between patients with and without history of osteoporosis showed a significant difference in HU (155+/-76 vs 134+/-79 p<0.001) and but not in DEXA (p=0.07). A significant but weak association between DEXA and HU measurements (r=0.286 & 0.285 p<0.002). HU did not correlate with baseline demographic parameters such as BMI, CCMI, or frailty but did correlate with age (p<0.009 r=-0.215). Similarly, DEXA did not correlate with baseline demographic parameters except for BMI (p<0.002,r=0.298).
CONCLUSION(S): In this large cohort of surgical ASD patients, bone quality assessment was available for 18% of patients via DEXA or 46% via HU on CT. HU measured from an axial image of L1 and UIV appears to be a reliable assessment of bone quality. Previous instrumentation did not alter the measurements. There was a significant but weak correlation when comparing HU to DEXA. Patients with a reported history of osteoporosis had lower HU. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: In asymptomatic individuals, two-thirds of the lordosis comes from the L4-S1 level. It is commonly believed that the majority of loss of lordosis in adult spinal deformity (ASD) is attributable to the distal (L4-S1) levels. PURPOSE: This study aims to investigate the location of loss of lordosis in a cohort of ASD patients prior to surgical intervention. STUDY DESIGN/SETTING: Retrospective review of prospective databases. PATIENT SAMPLE: This study included 119 symptomatic adult volunteer and 357 adult spinal deformity patients. OUTCOME MEASURES: Regional and focal alignment. Lordosis distribution.
METHOD(S): A registry of asymptomatic volunteers was used to build age and pelvic incidence (PI) adjusted normative models of PI-LL, L1-L4 lordosis, L4-S1 lordosis, TL kyphosis (T10-L2), and thoracic kyphosis (T1-T12). Our study cohort was a registry of surgical primary ASD patients without coronal malalignment (SRS-Schwab Type=N). The formulas developed in the asymptomatic population were applied to the ASD group to calculate normative values for each patient. The ASD population was divided into four groups based on quartiles of PI-LL: no, mild, moderate, and severe PI-LL mismatch. Within each group, paired t-tests were performed to compare actual and calculated normative sagittal alignment; actual alignment was also expressed in percentage of normative values. The level of significance was p<0.05.
RESULT(S): The asymptomatic cohort used included 119 asymptomatic volunteers (50.7yo+/-17, PI: 52degree+/-11.4) with the following regional alignment: L4-S1=34degree, L1-L4=23degree, TKL=3degree, and TK=49degree. The study cohort included 357 ASD patients (64.6yo, 58.5%F). The PI-LL of the 4 quartiles were -10degree, 10degree, 20degree, and 40degree. There were no significant differences in PI or in any of the coronal Cobb angles. Comparing each ASD group to the calculated normative values; the "no mismatch" group had a greater L4-S1 (+8degree), a greater T10-L2 kyphosis (+14degree) and T1-T12 kyphosis (+8degree), but no difference in L1-L4. The "mild mismatch" group had a smaller L1-L4 (-12degree), greater TLK (+5degree), smaller TK (-7degree) and no difference in L4-S1. The "moderate mismatch" had a smaller L4-S1 (-7degree), L1-L4 (-15degree), TK (-15degree) but no difference in TLK. Finally, the "severe mismatch" group had a smaller L4-S1 (-15degree), L1-L4 (-26degree), and TK (-27degree) but no difference in TKL (all with p<0.001). The analysis by percentage of actual alignment vs the calculated age and PI matched normative values permitted to identify the driver(s) of the sagittal malalignment. The "no mismatch" had an excess of TLK (+510%) compensated by an excess in L4-S1 (+27%). The "mild mismatch" had a loss of L1-L4 (-48%) with a normal L4-S1, while the "moderate mismatch" had mainly a deficit in L1-L4 (-66%) associated to a 22% loss on L4-S1. Finally, "severe-mismatch" presented a kyphotic L1-L4 (-115% vs norm) with a 46% deficit in L4-S1
CONCLUSION(S): In this cohort of ASD patients with limited coronal deformity, the majority of the loss of lordosis is attributable to the proximal segment. As the deformity worsened, the loss of lordosis also involved the distal lumbar segments. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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