Faculty Bibliography

STUDY DESIGN/SETTING/METHODS:Retrospective review of a prospectively collected database. OBJECTIVE:The objective of this study was to determine the relationship between paracervical muscle area, density, and fat infiltration and cervical alignment among patients presenting with cervical spine pathology. BACKGROUND CONTEXT/BACKGROUND:The impact of cervical spine alignment on clinical outcomes has been extensively studied, but little is known about the association between spinal alignment and cervical paraspinal musculature. METHODS:We examined computed tomography scans and radiographs for patients presenting with cervical spine pathology. The posterior paracervical muscle area, density, and fat infiltration was calculated on axial slices at C2, C4, C6, and T1. We measured radiographic parameters including cervical sagittal vertical axis, cervical lordosis, T1 slope (T1S), range of motion of the cervical spine. We performed Pearson correlation tests to determine if there were significant relationships between muscle measurements and alignment parameters. RESULTS:The study included 51 patients. The paracervical muscle area was higher for males at C2 (P=0.005), C4 (P=0.001), and T1 (P=0.002). There was a positive correlation between age and fat infiltration at C2, C4, C6, and T1 (all P<0.05). The cervical sagittal vertical axis positively correlated with muscle cross-sectional area at C2 (P=0.013) and C4 (P=0.013). Overall cervical range of motion directly correlated with muscle density at C2 (r=0.48, P=0.003), C4 (r=0.41, P=0.01), and C6 (r=0.53. P<0.001) and indirectly correlated with fat infiltration at C2 (r=-0.40, P=0.02), C4 (r=-0.32, P=0.04), and C6 (r=-0.35, P=0.02). Muscle density correlated directly with reserve of extension at C2 (r=0.57, P=0.009), C4 (r=0.48, P=0.037), and C6 (r=0.47, P=0.033). Reserve of extension indirectly correlated with fat infiltration at C2 (r=0.65, P=0.006), C4 (r=0.47, P=0.037), and C6 (r=0.48, P=0.029). CONCLUSIONS:We have identified specific changes in paracervical muscle that are associated with a patient's ability to extend their cervical spine.

STUDY DESIGN/METHODS:Retrospective review of a multicenter comprehensive cervical deformity (CD) database. OBJECTIVE:To develop a novel risk index specific to each patient to aid in patient counseling and surgical planning to minimize postop DJK occurrence. BACKGROUND:Distal junctional kyphosis(DJK) is a radiographic finding identified after patients undergo instrumented spinal fusions which can result in sagittal spinal deformity, pain and disability, and potentially neurological compromise. DJK is considered multifactorial in nature and there is a lack of consensus on the true etiology of DJK. METHODS:CD pts with baseline(BL) and at least 1-year postoperative(1Y) radiographic follow-up were included. A patient-specific DJK score was created through use of unstandardized Beta weights of a multivariate regression model predicting DJK(end of fusion construct to the 2nd distal vertebra change in this angle by<-10° from BL to postop). RESULTS:110 CD pts included(61yrs, 66.4%F, 28.8kg/m2). 31.8% of these pts developed DJK (16.1% 3M, 11.4% 6M, 62.9% 1Y). At BL, DJK pts were more frail and underwent combined approach more (both P<0.05). Multivariate model regression analysis identified individualized scores through creation of a DJK equation: -0.55+0.009(BL Inclination) -0.078(Pre Inflection)+5.9×10-5(BL LIV angle) + 0.43(combine approach) - 0.002(BL TS-CL)- 0.002(BL PT)- 0.031(BL C2-C7)+ 0.02(∆T4-T12)+ 0.63(Osteoporosis)- 0.03(anterior approach) - 0.036( Frail) - 0.032(3 column osteotomy). This equation has a 77.8% accuracy of predicting DJK. A score ≥81 predicted DJK with an accuracy of 89.3%. The BL reference equation correlated with 2Y outcomes of NSR-Back percentage(P=0.003), reoperation(P=0.04), and MCID for EQ. 5D(P=0.04). CONCLUSIONS:This study proposes a novel risk index of DJK development that focuses on potentially modifiable surgical factors as well as established patient-related and radiographic determinants. The reference model created demonstrated strong correlations with relevant two year outcome measures, including axial pain-related symptoms, occurrence of related reoperations, and the achievement of minimal clinically importance differences for EQ. 5D.

BACKGROUND CONTEXT: Surgical correction of adult spinal deformity (ASD) has been associated with superior alignment and functional outcomes. However, postoperative complication rates remain relatively high. The extent to which potentially modifiable patient-related factors can influence complication rates in adult spinal deformity patients has not been effectively evaluated. PURPOSE: Evaluate the association between modifiable patient-related factors on complications following ASD corrective surgery. STUDY DESIGN/SETTING: Retrospective. PATIENT SAMPLE: A total of 689 ASD patients. OUTCOME MEASURES: Complication and reoperation rates.
METHOD(S): ASD patients with 2-year (2Y) data were included. Complication groups were defined as follows: 1) any complication; 2) major; 3) medical (cardiac event, ileus, etc.); surgical (site infection, wound dehiscence, etc.); 5) major mechanical (implant failure, rod fracture); 6) major radiographic (PJF [proximal junctional failure], pseudarthrosis, adjacent segment disease); and 7) reoperation. Modifiable risk factors included current smoker, obesity (BMI >30kg/m²), osteoporosis, alcohol use, depression (BL SF-36 MCS <35, perMatcham), psychiatric diagnosis and hypertension. Patients were stratified by BL deformity severity in T1PA (LowDef/HighDef) and age above or below 65 (Young/Older). Means comparison tests assessed prevalence of modifiable risk factors present in those developing specified complications. Binary logistic regression analysis was used to adjust for confounders.
RESULT(S): A total of 480 ASD patients met inclusion criteria (age 59+/-15 yrs, 77%F, BMI 27+/-5 kg/m², CCI: 1.7+/-1.7). By 2Y, comp rates: 72% one complication, 28% major, 21% medical, 27% surgical, 11% major radiographic, and 8% had a major mechanical complication. A total of 106 patients (22%) required reoperation. Overall, 318 patients (66%) had at least one of the preoperative risk factors. Age-Deformity Groups: 32% Young LowDef, 19% Young HighDef, 18% Older LowDef, 31% Older HighDef. Within Young LowDef, patients with osteoporosis were more likely to suffer either a major mechanical or radiographic comp (both OR >6, p<.05), although this trend was not seen in the overall cohort. Young HighDef patients were much more likely to develop complications if obese, especially major mechanical complications (OR: 2.8, [1.04-8.6]; p=.045), while patients with depression or a psychiatric diagnosis suffered major radiographic comps and underwent reoperation more often. Older patients with HighDef developed significantly more complications when diagnosed with depression, including major radiographic comps (23% vs 8%, OR: 3.5, [1.1-10.6]; p=.03). Overall, when controlling for baseline deformity, frailty, and osteoporosis, a diagnosis of depression proved to be a significant risk factor for development of major radiographic complications (OR: 2.4, [1.3-4.5]; p=.005).
CONCLUSION(S): Certain modifiable patient-related factors, especially mental health status, are associated with increased risk for complications following spinal deformity surgery. Therefore, with consideration to clinical presentation, elaborate on the utility in medical intervention prior to undergoing spinal deformity corrective surgery. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Bone Morphogenetic Protein-2 (BMP-2) has not shown superior benefit in terms of overall cost-effectiveness after implementation during adult spinal deformity (ASD) surgery. However, it remains to be shown whether certain discrete populations do obtain cost-utility from use of BMP-2. PURPOSE: Generate a score to determine usage of BMP-2 and correlate with rates of pseudarthrosis. STUDY DESIGN/SETTING: Retrospective cohort study of a single-center ASD database. PATIENT SAMPLE: A total of 689 ASD patients. OUTCOME MEASURES: Cost utility, pseudarthrosis.
METHOD(S): ASD patients with BL and 2-year(2Y) data included. BMP-2 kit size and cost: small - 4.2 mg ($21,800), medium - 8.4 mg ($23,667), large - 12 mg ($25,617). Published methods converted ODI to SF-6D. QALYs utilized a 3% discount rate for residual decline. Cost was calculated using the PearlDiver database and assessed for Complications and Comorbidities and Major Complications and Comorbidities according to CMS.gov definitions. Binary logistic regression analyses determined significant predictors for development of pseudarthrosis. Established weights were generated for predictive variables via back-step logistic regression for a risk score to predict development of pseudarthrosis. Risk score was then validated via Receiver Operating Characteristic (ROC) curve method analysis. Categories via conditional inference tree (CIT) analysis-derived thresholds were tested for cost-utility of BMP-2 usage. Marginalized means for utility gained and Cost per QALY were calculated within each risk score category, controlling for age, history of prior fusion, and baseline deformity and disability.
RESULT(S): Included: 387 ASD patients. Of 387, 64% received BMP-2 (1% small, 4% medium, 59% large). There were 17 (4.4%) of patients that developed pseudarthrosis by two years, 9 (2.3%) of which underwent reoperation. BMP-2 use, regardless of kit size, did not significantly lower pseudarthrosis rates overall (OR: 0.4, [0.2-1.04]). A predictive risk score for development of pseudarthrosis was formed by the following preoperative variables: age, frailty, history of diabetes, osteoporosis, depression, ASA grade, and baseline L4-S1 and T1PA. Via ROC method, this predictive risk score generated an AUC of 0.87. Following CIT machine learning, thresholds for the BMP Risk Score were derived: >5 No Risk (NoR), 3-5 Low Risk (LowR), 2-3 Moderate Risk (ModR), and <2 High Risk (HighR). The rates of pseudarthrosis for each category were: NoR - 0%; LowR - 1.6%; ModR - 9.3%; HighR - 24.3%. When assessing BMP-2 use and its cost-utility within each group, patients receiving BMP-2 had similar QALYs to those that did not receive BMP-2 (0.163 vs 0.171, p=.65). BMP-2 usage had significantly worse cost-utility in both NoR and LowR cohorts (both p<.05). In ModR patients, BMP-2 usage had equivocal cost-utility ($680,532.35 vs $580,380.21, p=.14). In the HighR cohort, the cost-utility difference narrowed even further (BMP-2 use: $743,155.21 vs $719,628.79, p=.82).
CONCLUSION(S): Our study shows BMP-2 has equivocal cost-utility within those at moderate and high risk for developing pseudarthrosis within two years following spinal deformity correction. The generated predictive score can better aid spine surgeons assess risk and enhance justification for the use of BMP-2 during surgical intervention for adult spinal deformity. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: The durability of adult spinal deformity (ASD) surgery is key for cost-effective treatment. Malalignment is one of the main reasons for revision surgery. PURPOSE: To investigate risk factors for loss of correction within the instrumented lumbar spine following ASD surgery. STUDY DESIGN/SETTING: Retrospective cohort study of a prospective database. PATIENT SAMPLE: This study included 321 ASD patients with minimum 3 -year follow-up. OUTCOME MEASURES: L1-S1, L4-S1 and L1-L4 lumbar lordosis.
METHOD(S): A total of 321 patients who underwent fusion of the lumbar spine (=5 levels, LIV S1/ilium) with a revision-free follow-up =3 years were identified. Patients were stratified by the change in PI-LL from 6 weeks to 3 years postop as Maintained vs Loss > 5degree. Those with a loss due to instrumentation failure (broken rod, screw pullout, etc.) were excluded before comparisons. Changes in regional and focal lordosis over time were investigated with repeated measures ANOVA and factor comparison.
RESULT(S): Mean age 64 yrs, BMI 28 kg/m², 80% female. The baseline alignment (PI-LL=21+/-19degree, T1PA=26+/-12degree) was corrected to PI-LL=3+/-13degree, and T1PA=18+/-10degree at 3 yrs (mean 3Y follow-up: 45+/-11m, with 44+/-11 mo between early and late follow-up). Eighty-two patients (25.5%) lost >5degree of PI-LL correction (mean loss 10+/-5degree). After exclusion of patients with instrumentation failure, 52 patients (Loss) with a mean loss of correction of 8.6+/-2.9 were compared to 222 controls with maintained LL correction. Demographics were similar between groups (age: 63 vs 61 p=0.15; Sex: 78.4% F vs 88.5% p=0.10). There were no significant differences in use of osteotomy, 3CO, and IBF between Loss and Maintained LL (all p >0.1). There was no significant difference in number of levels fused (11 vs 12 p=0.39), rod material (CoCr 59.4% vs 58.8% p=0.34), and BMP use (88.7% vs 84.6% p=0.41) but Loss had less supplemental rod use (5.8% vs 23.4% p=0.004). Comparison between Maintained and Loss revealed a similar PI-LL mismatch at pre-op (16.7+/-18.7 vs 20.9+/-18.3 p=0.14) and final postop (1.8+/-12.5 vs 5.1+/-14.5 p=0.11) but a significantly smaller PI-LL for Loss at early postop (0.6+/-12.8 vs -3.5+/-13.7 p=0.41). Distally, Maintained had a significant improvement in L4-S1 lordosis from preop to early postop (p=0.013), with no significant difference from early to final follow-up. In contrast, patients in the Loss group had no difference in L4-S1 from preop to early postop (p=0.14), but showed a significant loss of correction at 3 years (p <0.001). Proximally, significant increase between pre and early postop in L1-L4 (all p <0.001), with Loss and Maintained reaching similar early postop value (p=0.34). However, from early postop to final follow up, Loss showed a significant decrease in proximal lordosis (p <0.001) while Maintained did not (p=0.08), corresponding with a smaller absolute L1-L4 in the Loss cohort at 3 yrs (p=0.002). Screw orientation showed a significant decrease from early to late follow-up between the L1 and S1 screws for Loss (1.3+/-4.1 p=0.031), without any changes across the L4-S1 segment (-0.1+/-2.9 p=0.97).
CONCLUSION(S): Approximately a quarter of patients lose an average of 10degree of their 6-week correction by 3 years. Lordosis is lost proximally through the instrumentation (ie, tulip/shank angle shifts and/or rod bending), but lost distally through bone "settling" through the instrumentation itself. The use of supplemental rods and avoiding sagittal overcorrection may help mitigate this loss. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Preoperative risk stratification is critical to determining which adult spinal deformity (ASD) patients may develop postop complications and to maximize surgical success. Currently it is unknown if a preoperative inflammatory state results in a higher risk for postop complications. This information can be used in risk stratification models to aid in complication avoidance. PURPOSE: To determine if patients with preoperative elevated serum markers for inflammation have higher rates of postoperative complications STUDY DESIGN/SETTING: Retrospective review of multicenter prospective ASD database. PATIENT SAMPLE: ASD patients. OUTCOME MEASURES: C-reactive protein (CRP), Erythrocyte sedimentation rate (ESR), complications by type and by severity of intervention: none, mild, moderate and severe. Demographic and surgical variables: age, estimated blood loss (EBL), operating room (OR) time, body mass index (BMI), America Society of Anesthesia physical classification scale (ASA), Charlson comorbidity index (CCI), Edmonton frailty scale (EF), 3-column osteotomy (3CO), number of post fusion levels.
METHOD(S): Preoperative labs were drawn on ASD patients and the inflammatory markers were CRP and ESR. CRP thresholds for cardiac risk: normal = 3. The CRP moderate and elevated values were combined into one group named elevated. Normal ESR thresholds: Male age 50, =20, Female >50, =30. Patients were stratified by having normal or elevated markers and rates of complications were compared between the groups. A multivariate model with CRP/ESR and demographic/surgical variables for postoperative complications. Health-related quality of life (HRQOL) metrics were compared RESULTS: The total number of patients with preoperative CRP was 159 and ESR was 158. CRP: normal=114 patients (71.7%), moderate elevation=28 (17.6%), severe elevation=17 (10.7%). Combined elevated=45/159(28.3%). Elevated ESR=25(15.8%), normal=133(84.2%). The elevated CRP group had significantly higher rate of moderate complication 13/45(28.9%) vs 16/114(14.0%), p=0.03 and severe complication 15/45 (33.3%) vs 17/114(14.9%, p=0.009. Elevated ESR patients had significantly higher rate of moderate complication 9/25 (36.0%) vs 20/133 (15.0%), p=0.01. In multivariable logistic regression elevated CRP had odds ratio for moderate complication of 3.3 (95% CI 1.4-7.6, p=0.006), and for severe complication of 2.3 (95% CI 1.05-5.1, p=0.037). Multivariable logistic regression for elevated ESR and moderate complication had odds ratio of 2.9 (95%CI 1.04-7.8, p=0.041). Elevated CRP also had significantly higher rate of wound complications (15.6% vs 3.5%, p=0.007) and MSK complications (11.1% vs 1.8%, p=0.01). Elevated ESR had significantly higher rate of cardiac complications (32.0% vs 13.5%, p=0.02) and neurological complications (24.0% vs 9.0%, p=0.03). Elevated CRP had worse preoperative leg pain, SRS Activity and VR12 PCS(p<0.05). Elevated ESR had worse baseline ODI (p=0.03).
CONCLUSION(S): A preoperative inflammatory state as defined by elevated CRP and ESR is an independent risk factor for the development of moderate and severe postop complications. Having elevated preop CRP is 3.3 and 2.3 times more likely to have a moderate and severe complication, respectively. Elevated ESR is 2.9 times more likely to have a moderate complication. This data can be used in risk stratification models to aid in minimizing postoperative complications. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: As surgical techniques for deformity correction evolve towards minimizing tissue trauma, further clarity is warranted to define differences in complication profiles between cMIS and open surgeries. PURPOSE: To compare cMIS and open surgery reoperation rates and identify contributing etiologies to reoperation in each cohort. STUDY DESIGN/SETTING: Prospective multicenter observational series. PATIENT SAMPLE: Database enrollment required age =18 years, adult spinal deformity and circumferential minimally invasive spine surgery. OUTCOME MEASURES: Reoperation rate, patient reported outcomes (PROMS), spinopelvic parameters, mechanical failures (defined as rod breakage/dislocation, screw breakage/loosening, set screw loosening, proximal/distal junctional kyphosis, pseudoarthrosis) and other factors contributing to re-operation such as wound infection, medial breach, nerve impingement by screw, vertebral body fracture, sagittal/coronal imbalance, and wound infection.
METHOD(S): A total of 85 patients (pts) with cMIS for ASD with 2-year follow-up (2YFU) were identified and propensity matched to 85 patients in open cohort. Propensity matching was performed based on pre-operative PT, PI-LL, BMI, and SVA. Patient demographic variables, reoperation rate, and complications contributing to reoperation were compared with uni- and multi-variate analysis at any time in each cohort (33 open, 17 cMIS). PROMS at 2YFU were compared in the reoperated cohorts.
RESULT(S): Total of 33 reoperation in the open cohort vs 17 in cMIS were identified. The reoperation rate was significantly higher in the open cohort at 39% (33/85) compared to 20% (17/85) in the cMIS cohort (P= 0.012). The reoperation rate in open cohort related to mechanical failure was 52% (17/33) compared to 35% (6/17) in cMIS cohort (P= 0.43). No significant difference was found in rates of specific etiologies contributing to complications in the cMIS vs open reoperation cohorts under uni- and multivariate analysis. The change in spinopelvic parameters among the two reoperation cohorts at 2YFU were statistically not significant (deltaCVA, deltaSVA, deltaPI-LL, deltaPT, deltaLL CA, deltaTL CA). Under univariate analysis, the following PROMS were similar: ODI, NRS Leg and Back Pain, EQ5D, EQ5D-VAS, SF-36 PCS,SF-36 MCS. However, SRS-22 in open cohort was significantly higher at 2YFU (3.55 +/- 0.73 open vs. 3,10 +/- 0.56 MIS, p = 0.029).
CONCLUSION(S): Findings in our ongoing study show that cMIS procedures were associated with a significantly lower reoperation rate compared to open surgical approaches. PROMS and the change in spinopelvic parameters were similar at 2YFU in both reoperated cohorts (except for SRS-22 favored open cohort). FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Preoperative rehabilitation programs have recently been implemented to prepare patients for surgery and to promote patient health. In this cohort, preoperative rehabilitation consisted of physical and mental components. Patients were referred for physical therapy for 3 months, 3 days a week for core, paraspinal and leg strengthening, with a review of postop protocols to do at home, including gait and balance training. Patients were also referred for cognitive behavioral therapy for 2 weeks to prepare for the stress of surgery. Patients were excluded if they presented with any of the following at baseline (BL): severe neurological deficit (<3/5), minimal ambulation or current depression/anxiety. PURPOSE: Identify if preoperative rehabilitation influences patients' ability to recover and adult spinal deformity correction cost-effectiveness. STUDY DESIGN/SETTING: Retrospective cohort. PATIENT SAMPLE: This study included 689 adult spinal deformity patients. OUTCOME MEASURES: Preoperative rehabilitation, recovery kinetics, cost effectiveness.
METHOD(S): Adult spinal deformity patients with baseline (BL) and two-year (2Y) follow-up, and available preoperative rehabilitation and economic data were included. Patients were divided on whether or not they completed a preoperative rehabilitation assignment (Prehab) or not (no Prehab). Normalized HRQL scores at BL and follow-up intervals (6W, 1Y, 2Y) were generated. Normalized HRQLs were plotted and area under the curve was calculated, generating one number describing overall recovery (Integrated Health State [IHS]). Cost was calculated using the PearlDiver database. This data is representative of national average Medicare cost differentiated by complication/comorbidity outcome, surgical approach, and revision status. Cost per quality-adjusted life year (QALY) at 2Y were calculated. Multivariate logistic regression analysis assessed patient reported outcomes and cost adjusting for baseline and surgical characteristics.
RESULT(S): A total of 100 patients were included (36 Prehab, 64 no Prehab). Age (59.2 vs 56.2), gender (F: 58% vs 45%), body mass index (32.9 vs 31.4), and Charlson Comorbidity Index (3.8 vs 3.9) were similar between groups (P >0.05). OpTime, EBL, and length of construct were similar between groups (p >0.05). Normalized HRQLs determined Prehab patients to exhibit better ODI than no Prehab patients at 2Y follow-up, p 0.05. Cost effectiveness was determined via cost per QALY: Prehab = $14,463 and not Prehab = $45,515, p <0.05.
CONCLUSION(S): Patients who had a preoperative rehabilitation prior to corrective surgery were in a better state of postoperative back disability at two-year follow-up. While both patient cohorts had improvement following surgery, patients with preoperative rehabilitation had greater utility gained at two-year follow-up. Costs by procedure and cost effectiveness were better for patients who had preoperative rehabilitation. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Adaptation of age-adjusted alignment has gained popularity for its correlation with clinical improvement and lowering rates of proximal junctional kyphosis. Age-adjusted parameters correlate with outcomes. However, frailty may be a better predictor of each following ASD surgery. PURPOSE: To adjust the Sagittal Age-Adjusted Score (SAAS) to accommodate frailty in alignment considerations will increase the predictability of clinical outcomes and junctional failure. STUDY DESIGN/SETTING: Retrospective. PATIENT SAMPLE: A total of 689 ASD Patients. OUTCOME MEASURES: Mechanical complications, PJF, PJK and ODI.
METHOD(S): Included: surgical ASD pts with 2Y data. Frailty assessed by ASD modified Frailty Index (ASD-mFI).
Outcome(s): proximal junctional kyphosis (PJK) and failure (PJF), major mechanical complications, and Smith et al Best Clinical Outcome (BCO), defined as ODI 4.5. Linear regression analysis established a 6W score based on SAAS component scores, frailty and ODI US norms per published by Lafage et al. Logistic regression followed by conditional inference tree (CIT) analysis generated categorical thresholds. Logistic regression analysis controlling for age, baseline deformity and revision status generated odds ratios for the continuous score. Thirty percent of the cohort was used as a random sample for internal validation.
RESULT(S): There were 412 pts included. BL frailty categories: 57% not frail, 30% frail and 14% severely frail. Overall, by 2Y, 39% of patients developed PJK, 8% PJF, 21% mechanical complications, 22% underwent reoperation and 15% met BCO. SAAS only correlated with development of PJF. The ASD-mFI demonstrated correlation with all outcomes except PJK (all p1.4, offset: 0.75-1.4, sseverely offset:.05). Internal validation saw these outcomes maintain significance between categories, with significant adjusted correlation to meeting BCO (OR: 3.8, 1.1-13.5; p=.037).
CONCLUSION(S): Consideration of physiologic age, in addition to chronological age, may be beneficial in management of operative goals to maximize clinical outcomes while minimizing junctional failure. This combination enables the spine surgeon to fortify a surgical plan for even the most challenging patients undergoing adult spinal deformity surgery. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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BACKGROUND CONTEXT: Adult spinal deformity (ASD) patients maintain upright posture by compensating through their spine, pelvis and lower extremities. Little data exist quantifying the contribution of lower extremity compensation through the hips, knees, and ankles to maintain upright posture. PURPOSE: Evaluate the effect of the lower limb compensation by numerically unfolding patients. STUDY DESIGN/SETTING: Multicenter, prospective cohort. PATIENT SAMPLE: A total of 288 patients surgically treated for complex ASD with preoperative full body images. OUTCOME MEASURES: Horizontal distance between vertebra centroid and ankle.
METHOD(S): Surgical ASD patients were enrolled into a prospective study based on three criteria deformity severity (PI-LL>25degree, TPA>30degree, SVA>15cm, TCobb>70degree or TLCobb>50degree), procedure complexity (>12 levels fused, 3CO or ACR) and/or age (>65 and >7 levels fused). Preop full-body images were evaluated and age and PI-adjusted normative values were used to model spine alignment based upon three configurations: COMP (all lower extremity compensatory mechanisms maintained), PARTIAL (removal of ankle dorsiflexion and knee flexion, maintained hip extension), UNCOMP (ankle, knee, and hip compensation eliminated by reset PT to the age and PI norms). The three configurations were compared, and COMP alignment was stratified by TPA percentiles to investigate the offsets from each vertebra to the ankle joint acting as a surrogate of the gravity line in free-standing position.
RESULT(S): A total of 288 patients met inclusion criteria (60+/-15yo, 70.5% female, 27.4+/-5.9 BMI). COMP spine deformity magnitude included PI-LL 15+/-24, TPA 24+/-14, and SVA 65+/-69mm. As the model transitioned from COMP to UNCOMP alignment, the initial posterior translation of the pelvis decreased significantly to an anterior translation vs the ankle (P.Shift 30 to -7.6 mm). This was associated with a decrease in pelvic retroversion (PT 24.1 to 16.1), hip extension (SFA 203 to 200), knee flexion (KA 5.5 to -0.4), and ankle dorsiflexion (AA 5.3 to 3.7). As a result, the anterior malalignment of the trunk significantly increased SVA (65 to 120mm) and G-SVA (C7-Ankle from 36 to 127 mm), leading to a three-fold increase in bending moments sustained by the ankle joint. The stratification of the COMP position by TPA percentiles revealed that as the deformity increases, the vertebrae above T8 translate anteriorly, those below T10 move posteriorly, with the T8-T10 segment remaining ~3cm posterior to the ankle joint independently of the deformity severity.
CONCLUSION(S): Removal of lower limbs' compensation revealed an unsustainable truncal malalignment with a three-fold increase of bending moments at the ankle joints. Combined, lower limb compensations permit "reducing" the SVA by two-fold and the C7-ankle SVA by three-fold. From a mechanical point of view, this compensation permits maintaining the trunk center of mass (T9) at a fixed offset of ~3 cm from the ankle joint. FDA DEVICE/DRUG STATUS: This abstract does not discuss or include any applicable devices or drugs.
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