Browsing by Author "Hamilton, David K"

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    ItemOpen Access
    Adult Spinal Deformity Surgery Is Associated with Increased Productivity and Decreased Absenteeism From Work and School.
    (Spine, 2022-02) Durand, Wesley M; Babu, Jacob M; Hamilton, David K; Passias, Peter G; Kim, Han Jo; Protopsaltis, Themistocles; Lafage, Virginie; Lafage, Renaud; Smith, Justin S; Shaffrey, Christopher; Gupta, Munish; Kelly, Michael P; Klineberg, Eric O; Schwab, Frank; Gum, Jeffrey L; Mundis, Gregory; Eastlack, Robert; Kebaish, Khaled; Soroceanu, Alex; Hostin, Richard A; Burton, Doug; Bess, Shay; Ames, Christopher; Hart, Robert A; Daniels, Alan H; International Spine Study Group (ISSG)

    Study design

    Retrospective cohort study.

    Objective

    We hypothesized that adult spinal deformity (ASD) surgery would be associated with improved work- and school-related productivity, as well as decreased rates of absenteeism.

    Summary of background data

    ASD patients experience markedly decreased health-related quality of life along many dimensions.

    Methods

    Only patients eligible for 2-year follow-up were included, and those with a history of previous spinal fusion were excluded. The primary outcome measures in this study were Scoliosis Research Society-22r score (SRS-22r) questions 9 and 17. A repeated measures mixed linear regression was used to analyze responses over time among patients managed operatively (OP) versus nonoperatively (NON-OP).

    Results

    In total, 1188 patients were analyzed. 66.6% were managed operatively. At baseline, the mean percentage of activity at work/school was 56.4% (standard deviation [SD] 35.4%), and the mean days off from work/school over the past 90 days was 1.6 (SD 1.8). Patients undergoing ASD surgery exhibited an 18.1% absolute increase in work/school productivity at 2-year follow-up versus baseline (P < 0.0001), while no significant change was observed for the nonoperative cohort (P > 0.5). Similarly, the OP cohort experienced 1.1 fewer absent days over the past 90 days at 2 years versus baseline (P < 0.0001), while the NON-OP cohort showed no such difference (P > 0.3). These differences were largely preserved after stratifying by baseline employment status, age group, sagittal vertical axis (SVA), pelvic incidence minus lumbar lordosis (PI-LL), and deformity curve type.

    Conclusion

    ASD patients managed operatively exhibited an average increase in work/school productivity of 18.1% and decreased absenteeism of 1.1 per 90 days at 2-year follow-up, while patients managed nonoperatively did not exhibit change from baseline. Given the age distribution of patients in this study, these findings should be interpreted as pertaining primarily to obligations at work or within the home. Further study of the direct and indirect economic benefits of ASD surgery to patients is warranted.Level of Evidence: 3.
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    ItemOpen Access
    Artificial Intelligence Models Predict Operative Versus Nonoperative Management of Patients with Adult Spinal Deformity with 86% Accuracy.
    (World neurosurgery, 2020-09) Durand, Wesley M; Daniels, Alan H; Hamilton, David K; Passias, Peter; Kim, Han Jo; Protopsaltis, Themistocles; LaFage, Virginie; Smith, Justin S; Shaffrey, Christopher; Gupta, Munish; Klineberg, Eric; Schwab, Frank; Burton, Doug; Bess, Shay; Ames, Christopher; Hart, Robert; International Spine Study Group

    Objective

    Patients with ASD show complex and highly variable disease. The decision to manage patients operatively is largely subjective and varies based on surgeon training and experience. We sought to develop models capable of accurately discriminating between patients receiving operative versus nonoperative treatment based only on baseline radiographic and clinical data at enrollment.

    Methods

    This study was a retrospective analysis of a multicenter consecutive cohort of patients with ASD. A total of 1503 patients were included, divided in a 70:30 split for training and testing. Patients receiving operative treatment were defined as those undergoing surgery up to 1 year after their baseline visit. Potential predictors included available demographics, past medical history, patient-reported outcome measures, and premeasured radiographic parameters from anteroposterior and lateral films. In total, 321 potential predictors were included. Random forest, elastic net regression, logistic regression, and support vector machines (SVMs) with radial and linear kernels were trained.

    Results

    Of patients in the training and testing sets, 69.0% (n = 727) and 69.1% (n = 311), respectively, received operative management. On evaluation with the testing dataset, performance for SVM linear (area under the curve =0.910), elastic net (0.913), and SVM radial (0.914) models was excellent, and the logistic regression (0.896) and random forest (0.830) models performed very well for predicting operative management of patients with ASD. The SVM linear model showed 86% accuracy.

    Conclusions

    This study developed models showing excellent discrimination (area under the curve >0.9) between patients receiving operative versus nonoperative management, based solely on baseline study enrollment values. Future investigations may evaluate the implementation of such models for decision support in the clinical setting.
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    ItemOpen Access
    Identifying Thoracic Compensation and Predicting Reciprocal Thoracic Kyphosis and Proximal Junctional Kyphosis in Adult Spinal Deformity Surgery.
    (Spine, 2018-11) Protopsaltis, Themistocles S; Diebo, Bassel G; Lafage, Renaud; Henry, Jensen K; Smith, Justin S; Scheer, Justin K; Sciubba, Daniel M; Passias, Peter G; Kim, Han Jo; Hamilton, David K; Soroceanu, Alexandra; Klineberg, Eric O; Ames, Christopher P; Shaffrey, Christopher I; Bess, Shay; Hart, Robert A; Schwab, Frank J; Lafage, Virginie; International Spine Study Group
    STUDY DESIGN:Retrospective analysis. OBJECTIVE:To define thoracic compensation and investigate its association with postoperative reciprocal thoracic kyphosis and proximal junctional kyphosis (PJK) SUMMARY OF BACKGROUND DATA.: Adult spinal deformity (ASD) patients recruit compensatory mechanisms like pelvic retroversion and knee flexion. However, thoracic hypokyphosis is a less recognized compensatory mechanism. METHODS:Patients enrolled in a multicenter ASD registry undergoing fusions to the pelvis with upper instrumented vertebra (UIV) between T9 and L1 were included. Patients were divided into those with postoperative reciprocal thoracic kyphosis (reciprocal kyphosis [RK]: change in unfused thoracic kyphosis [TK] ≥15°) with and without PJK and those who maintained thoracic alignment (MT). Thoracic compensation was defined as expected thoracic kyphosis (eTK) minus preoperative TK. RESULTS:For RK (n = 117), the mean change in unfused TK was 21.7° versus 6.1° for MT (n = 102) and the mean PJK angle change was 17.6° versus 5.7° for MT (all P < 0.001). RK and MT were similar in age, body mass index (BMI), sex, and comorbidities. RK had larger preoperative PI-LL mismatch (30.7 vs. 23.6, P = 0.008) and less preoperative TK (22.3 vs. 30.6, P < 0.001), otherwise sagittal vertical axis (SVA), pelvic tilt (PT), and T1 pelvic angle (TPA) were similar. RK patients had more preoperative thoracic compensation (29.9 vs. 20.0, P < 0.001), more PI-LL correction (29.8 vs. 17.3, P < 0.001), and higher rates of PJK (66% vs. 19%, P < 0.001). There were no differences in preoperative health-related quality of life (HRQOL) except reciprocal kyphosis (RK) had worse Scoliosis Research Society questionnaire (SRS) appearance (2.2 vs. 2.5, P = 0.005). Using a logistic regression model, the only predictor for postoperative reciprocal thoracic kyphosis was more preoperative thoracic compensation. Postoperatively the RK and MT groups were well aligned. Both younger and older (>65 yr) RK patients had greater thoracic compensation than MT counterparts. The eTK was not significantly different from the postoperative TK for the RK group without PJK (P = 0.566). CONCLUSION:The presence of thoracic compensation in adult spinal deformity is the primary determinant of postoperative reciprocal thoracic kyphosis and these patients have higher rates of proximal junctional kyphosis. LEVEL OF EVIDENCE:3.
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    ItemOpen Access
    Lateral Thoracolumbar Listhesis as an Independent Predictor of Disability in Adult Scoliosis Patients: Multivariable Assessment Before and After Surgical Realignment.
    (Neurosurgery, 2021-11) Daniels, Alan H; Durand, Wesley M; Lafage, Renaud; Zhang, Andrew S; Hamilton, David K; Passias, Peter G; Kim, Han Jo; Protopsaltis, Themistocles; Lafage, Virginie; Smith, Justin S; Shaffrey, Christopher; Gupta, Munish; Klineberg, Eric; Schwab, Frank; Burton, Doug; Bess, Shay; Ames, Christopher; Hart, Robert A

    Background

    Lateral (ie, coronal) vertebral listhesis may contribute to disability in adult scoliosis patients.

    Objective

    To assess for a correlation between lateral listhesis and disability among patients with adult scoliosis.

    Methods

    This was a retrospective multi-center analysis of prospectively collected data. Patients eligible for a minimum of 2-yr follow-up and with coronal plane deformity (defined as maximum Cobb angle ≥20º) were included (n = 724). Outcome measures were Oswestry Disability Index (ODI) and leg pain numeric scale rating. Lateral thoracolumbar listhesis was measured as the maximum vertebral listhesis as a percent of the superior endplate across T1-L5 levels. Linear and logistic regression was utilized, as appropriate. Multivariable analyses adjusted for demographics, comorbidities, surgical invasiveness, maximum Cobb angle, and T1-PA. Minimally clinically important difference (MCID) in ODI was defined as 12.8.

    Results

    In total, 724 adult patients were assessed. The mean baseline maximum lateral thoracolumbar listhesis was 18.3% (standard deviation 9.7%). The optimal statistical grouping for lateral listhesis was empirically determined to be none/mild (<6.7%), moderate (6.7-15.4%), and severe (≥15.4%). In multivariable analysis, listhesis of moderate and severe vs none/mild was associated with worse baseline ODI (none/mild = 33.7; moderate = 41.6; severe = 43.9; P < .001 for both comparisons) and leg pain NSR (none/mild = 2.9, moderate = 4.0, severe = 5.1, P < .05). Resolution of severe lateral listhesis to none/mild was independently associated with increased likelihood of reaching MCID in ODI at 2 yr postoperatively (odds ratio 2.1 95% confidence interval 1.2-3.7, P = .0097).

    Conclusion

    Lateral thoracolumbar listhesis is associated with worse baseline disability among adult scoliosis patients. Resolution of severe lateral listhesis following deformity correction was independently associated with increased likelihood of reaching MCID in ODI at 2-yr follow-up.
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    ItemOpen Access
    Low-Density Pedicle Screw Constructs Are Associated with Lower Incidence of Proximal Junctional Failure in Adult Spinal Deformity Surgery.
    (Spine, 2022-03) Durand, Wesley M; DiSilvestro, Kevin J; Kim, Han Jo; Hamilton, David K; Lafage, Renaud; Passias, Peter G; Protopsaltis, Themistocles S; Lafage, Virginie; Smith, Justin S; Shaffrey, Christopher I; Gupta, Munish C; Klineberg, Eric O; Schwab, Frank J; Gum, Jeffrey L; Mundis, Gregory M; Eastlack, Robert K; Kebaish, Khaled M; Soroceanu, Alexandra; Hostin, Richard A; Burton, Douglas C; Bess, Shay; Ames, Christopher P; Hart, Robert A; Daniels, Alan H; International Spine Study Group

    Study design

    Retrospective cohort study.

    Objective

    Determine whether screws per level and rod material/diameter are associated with incidence of proximal junctional kyphosis (PJF).

    Summary of background data

    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.

    Methods

    Patients with ASD and 2-year minimum follow-up were included. Only patients undergoing primary fusion of more than or equal to five levels with lower instrumented vertebrae (LIV) at the sacro-pelvis were included. Screws per level fused was analyzed with a cutoff of 1.8 (determined by receiver operating characteristic curve (ROC) analysis). Multivariable logistic regression was utilized, controlling for age, body mass index (BMI), 6-week postoperative change from baseline in lumbar lordosis, number of posterior levels fused, sex, Charlson comorbidity index, approach, osteotomy, upper instrumented vertebra (UIV), osteoporosis, preoperative TPA, and pedicle screw at the UIV (as opposed to hook, wire, etc.).

    Results

    In total, 504 patients were included. PJF occurred in 12.7%. The mean screws per level was 1.7, and 56.8% of patients had less than 1.8 screws per level. No differences were observed between low versus high screw density groups for T1-pelvic angle or magnitude of lordosis correction (both P > 0.15). PJF occurred in 17.0% versus 9.4% of patients with more than or equal to 1.8 versus less than 1.8 screws per level, respectively (P < 0.05). In multivariable analysis, patients with less than 1.8 screws per level exhibited lower odds of PJF (odds ratio (OR) 0.48, P < 0.05), and a continuous variable for screw density was significantly associated with PJF (OR 3.87 per 0.5 screws per level, P < 0.05). Rod material and diameter were not significantly associated with PJF (both P > 0.1).

    Conclusion

    Among ASD patients undergoing long-segment primary fusion to the pelvis, the risk of PJF was lower among patients with less than 1.8 screws per level. This finding may be related to construct rigidity. Residual confounding by other patient and surgeon-specific characteristics may exist. Further biomechanical and clinical studies exploring this relationship are warranted.Level of Evidence: 3.
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    ItemOpen Access
    Predicting the Magnitude of Distal Junctional Kyphosis Following Cervical Deformity Correction.
    (Spine, 2023-02) Ayres, Ethan W; Protopsaltis, Themistocles S; Ani, Fares; Lafage, Renaud; Walia, Arnaav; Mundis, Gregory M; Smith, Justin S; Hamilton, David K; Klineberg, Eric O; Sciubba, Daniel M; Hart, Robert A; Bess, Shay; Shaffrey, Christopher I; Schwab, Frank J; Lafage, Virginie; Ames, Christopher P; International Spine Study Group (ISSG)

    Study design

    Retrospective review of a cervical deformity database.

    Objective

    This study aimed to develop a model that can predict the postoperative distal junctional kyphosis angle (DJKA) using preoperative and postoperative radiographic measurements.

    Summary of background data

    Distal junctional kyphosis (DJK) is a complication following cervical deformity correction that can reduce of patient quality of life and functional status. Although researchers have identified the risk factors for DJK, no model has been proposed to predict the magnitude of DJK.

    Materials and methods

    The DJKA was defined as the Cobb angle from the lower instrumented vertebra (LIV) to LIV-2 with traditional DJK having a DJKA change >10°. Models were trained using 66.6% of the randomly selected patients and validated in the remaining 33.3%. Preoperative and postoperative radiographic parameters associated with DJK were identified and ranked using a conditional variable importance table. Linear regression models were developed using the factors most strongly associated with postoperative DJKA.

    Results

    A total of 131 patients were included with a mean follow-up duration of 14±8 months. The mean postoperative DJKA was 14.6±14° and occurred in 35% of the patients. No significant differences between the training and validation cohort were observed. The variables most associated with postoperative DJK were: preoperative DJKA (DJKApre), postoperative C2-LIV, and change in cervical lordosis (∆CL). The model identified the following equation as predictive of DJKA: DJKA=9.365+(0.123×∆CL)-(0.315×∆C2-LIV)-(0.054×DJKApre). The predicted and actual postoperative DJKA values were highly correlated ( R =0.871, R2 =0.759, P <0.001).

    Conclusions

    The variables that most increased the DJKA were the preoperative DJKA, postoperative alignment within the construct, and change in cervical lordosis. Future studies can build upon the model developed to be applied in a clinical setting when planning for cervical deformity correction.
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    ItemOpen Access
    Sexual Dysfunction Secondary to Lumbar Stiffness in Adult Spinal Deformity Patients before and after Long-Segment Spinal Fusion.
    (World neurosurgery, 2020-04-17) Daniels, Alan H; Reid, Daniel; Durand, Wesley; Disilvestro, Kevin; Hamilton, David K; Passias, Peter; Kim, Han Jo; Protopsaltis, Themistocles; LaFage, Virginie; Smith, Justin S; Shaffrey, Christopher; Gupta, Munish; Klineberg, Eric; Schwab, Frank; Burton, Doug; Bess, Shay; Ames, Christopher; Hart, Robert; International Spine Study Group
    OBJECT:Sexual function is an important factor which contributes to quality of life. ASD patients may have sexual limitations due to lumbar spinal stiffness which may be affected by long-segment fusion. METHODS:This study utilized a multi-center, prospectively defined, consecutive cohort of ASD patients. The primary outcome in this study was the LSDI question 10: "Choose the statement that best describes the effect of low back stiffness on your ability to engage in sexual intercourse". RESULTS:In total, 368 patients were included in this study, including 76 males and 292 females of which 80.7% (n=293) underwent 9 or more level fusion and 74.4% (n=270) had pelvic fixation. Baseline LSDI sexual function scores averaged 1.7 (SD 1.3), which improved to 1.3 (SD 1.2) at 2-year follow-up (p = 0.0008). After adjusting for confounding factors, worse LSDI sexual function score was strongly associated with worse ODI, SRS total, and SF-36 PCS and MCS scores at both baseline and 2-year follow-up (p<0.05 for all comparisons). Predictors of poorer baseline sexual function included older age, increased SVA, and increased back pain (p<0.05 for all comparisons). Predictors of improvement in sexual function at 2-year follow-up included SVA improvement (p=0.0032) and decreased postoperative back pain (p<0.0001). CONCLUSIONS:This study found that sexual dysfunction scores due to lumbar stiffness significantly improved following surgery for ASD. Additionally, lumbar stiffness related sexual dysfunction is strongly related to overall outcome measured by ODI and SRS total score, highlighting the importance of sexual health on overall outcome in ASD patients.
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    ItemOpen Access
    Stiffness After Pan-Lumbar Arthrodesis for Adult Spinal Deformity Does Not Significantly Impact Patient Functional Status or Satisfaction Irrespective of Proximal Endpoint.
    (Spine, 2017-08) Hart, Robert A; Hiratzka, Jayme; Kane, Marie S; Lafage, Virginie; Klineberg, Eric; Ames, Christopher P; Line, Breton G; Schwab, Frank; Scheer, Justin K; Bess, Shay; Hamilton, David K; Shaffrey, Christopher I; Mundis, Greg; Smith, Justin S; Burton, Douglas C; Sciubba, Daniel M; Deviren, Vedat; Boachie-Adjei, Oheneba; International Spine Study Group

    Study design

    Prospective, multicenter.

    Objective

    To determine if stiffness significantly affects function or satisfaction after pan-lumbar arthrodesis.

    Summary of background data

    The Lumbar Stiffness Disability Index (LSDI) is a validated measure of the effect of lumbar stiffness on functional activities. Data suggests that patients undergoing fusion of the entire lumbar spine are at greatest risk of functional limitations from stiffness.

    Methods

    The LSDI, Short Form 36, Scoliosis Research Society-22, and Oswestry Disability Index were administered preoperatively and at 2-year minimum follow-up to 103 spinal deformity patients from 11 centers. Patients were separated according to the proximal arthrodesis level; upper thoracic (T2-5) to pelvis (UT-Pelvis) or thoraco-lumbar (T10-T12) to pelvis (TL-Pelvis). Outcome scores were compared using Student t test or Tukey-Kramer Honest Significant Difference Analysis of Variance. Regression analysis of final LSDI scores versus Scoliosis Research Society-22 Satisfaction scores was performed.

    Results

    Mean ages, baseline values, and final scores of all outcome parameters were statistically equivalent in the two groups. Final LSDI scores did not change significantly from baseline in the UT-Pelvis (P = 0.478) or TL-Pelvis (P = 0.301) groups. In contrast, highly significant improvements (P ≤ 0.0001) from baseline were seen in both groups for other health-related QoL measures. The 2-year Satisfaction scores were statistically equivalent in the two groups, and the correlation between final LSDI and Satisfaction scores in the entire cohort was not significant (R = 0.013, P = 0.146).

    Conclusion

    Patients undergoing pan-lumbar arthrodesis for adult spinal deformity did not experience substantial increases in disability due to stiffness of the low back, although they did report significant improvements in other health-related QoL measures. Further, LSDI scores did not correlate with patient satisfaction. There were no significant differences in perceived stiffness effects whether arthrodesis stopped in the thoracolumbar or upper thoracic regions. We hope these results will be useful to spine surgeons and patients during preoperative planning and discussions.

    Level of evidence

    2.
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    ItemOpen Access
    The Case for Operative Efficiency in Adult Spinal Deformity Surgery: Impact of Operative Time on Complications, Length of Stay, Alignment, Fusion Rates, and Patient Reported Outcomes.
    (Spine, 2023-11) Daniels, Alan H; Daher, Mohammad; Singh, Manjot; Balmaceno-Criss, Mariah; Lafage, Renaud; Diebo, Bassel G; Hamilton, David K; Smith, Justin S; Eastlack, Robert K; Fessler, Richard G; Gum, Jeffrey L; Gupta, Munish C; Hostin, Richard; Kebaish, Khaled M; Klineberg, Eric O; Lewis, Stephen J; Line, Breton G; Nunley, Pierce D; Mundis, Gregory M; Passias, Peter G; Protopsaltis, Themistocles S; Buell, Thomas; Scheer, Justin K; Mullin, Jeffrey P; Soroceanu, Alex; Ames, Christopher P; Lenke, Lawrence G; Bess, Shay; Shaffrey, Christopher I; Burton, Douglas C; Lafage, Virginie; Schwab, Frank J; International Spine Study Group

    Study design

    Retrospective review of prospectively collected data.

    Objective

    To analyze the impact of operative room (OR) time in adult spinal deformity (ASD) surgery on patient outcomes.

    Background

    It is currently unknown if OR time in ASD patients matched for deformity severity and surgical invasiveness is associated with patient outcomes.

    Methods

    ASD patients with baseline and 2-year postoperative radiographic and patient reported outcome measures (PROM) data, undergoing posterior only approach for long fusion (> L1- Ilium) were included. Patients were grouped into Short OR Time (<40 th percentile: <359 min) and Long OR Time (>60 th percentile: > 421 min). Groups were matched by age, baseline deformity severity, and surgical invasiveness. Demographics, radiographic, PROM data, fusion rate, and complications were compared between groups at baseline and 2-years follow-up.

    Results

    In total, 270 patients were included for analysis: mean OR time was 286 minutes in the Short OR group vs 510 minutes in the Long OR group ( P <0.001). Age, gender, percent of revision cases, surgical invasiveness, PI-LL, SVA and PT were comparable between groups ( P >0.05). Short OR had a slightly lower BMI than the short OR group ( P <0.001) and decompression was more prevalent in the long OR time ( P =0.042). Patients in the Long group had greater hospital length of stay (LOS) ( P =0.02); blood loss ( P <0.001); proportion requiring ICU ( P =0.003); higher minor complication rate ( P =0.001); with no significant differences for major complications or revision procedures ( P >0.5). Both groups had comparable radiographic fusion rates ( P =0.152) and achieved improvement in sagittal alignment measures, ODI and SF36 ( P <0.001).

    Conclusion

    Shorter OR time for ASD correction is associated with lower minor complication rate, lower EBL, fewer ICU admissions, and shorter hospital LOS without sacrificing alignment correction or PROMS. Maximizing operative efficiency by minimizing OR time in ASD surgery has the potential to benefit patients, surgeons, and hospital systems.
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    ItemOpen Access
    The spino-pelvic ratio: a novel global sagittal parameter associated with clinical outcomes in adult spinal deformity patients.
    (European spine journal : official publication of the European Spine Society, the European Spinal Deformity Society, and the European Section of the Cervical Spine Research Society, 2020-09) Durand, Wesley M; Daniels, Alan H; Hamilton, David K; Passias, Peter; Kim, Han Jo; Protopsaltis, Themistocles; LaFage, Virginie; Smith, Justin S; Shaffrey, Christopher; Gupta, Munish; Kelly, Michael P; Klineberg, Eric; Schwab, Frank; Burton, Doug; Bess, Shay; Ames, Christopher; Hart, Robert; International Spine Study Group (ISSG)

    Purpose

    Analysis of interactions of spinal alignment metrics may uncover novel alignment parameters, similar to PI-LL. This study utilized a data-driven approach to hypothesis generation by testing all possible division interactions between spinal alignment parameters.

    Methods

    This study was a retrospective cohort analysis. In total, 1439 patients with baseline ODI were included for hypothesis generation. In total, 666 patients had 2-year postoperative follow-up and were included for validation. All possible combinations of division interactions between baseline metrics were assessed with linear regression against baseline ODI.

    Results

    From 247 raw alignment metrics, 32,398 division interactions were considered in hypothesis generation. Conceptually, the TPA divided by PI is a measure of the relative alignment of the line connecting T1 to the femoral head and the line perpendicular to the sacral endplate. The mean TPA/PI was 0.41 at baseline and 0.30 at 2 years postoperatively. Higher TPA/PI was associated with worse baseline ODI (p < 0.0001). The change in ODI at 2 years was linearly associated with the change in TPA/PI (p = 0.0172). The optimal statistical grouping of TPA/PI was low/normal (≤ 0.2), medium (0.2-0.4), and high (> 0.4). The R-squared for ODI against categorical TPA/PI alone (0.154) was directionally higher than that for each of the individual Schwab modifiers (SVA: 0.138, PI-LL 0.111, PT 0.057).

    Conclusion

    This study utilized a data-driven approach for hypothesis generation and identified the spino-pelvic ratio (TPA divided by PI) as a promising measure of sagittal spinal alignment among ASD patients. Patients with SPR > 0.2 exhibited inferior ODI scores.

    Level of evidence

    III.
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    ItemOpen Access
    Younger Patients Are Differentially Affected by Stiffness-Related Disability Following Adult Spinal Deformity Surgery.
    (World neurosurgery, 2019-08-31) Durand, Wesley M; Daniels, Alan H; Hamilton, David K; Passias, Peter G; Kim, Han Jo; Protopsaltis, Themistocles; Lafage, Virginie; Smith, Justin S; Shaffrey, Christopher; Gupta, Munish; Kelly, Michael P; Klineberg, Eric; Schwab, Frank; Burton, Doug; Bess, Shay; Ames, Christopher; Hart, Robert; International Spine Study Group
    OBJECT:The LSDI assesses the impact of lumbar stiffness on activities of daily living. We hypothesized that patients <60 years-old would perceive greater lumbar stiffness-related functional limitation following fusion for adult spinal deformity. METHODS:Patients completed the LSDI and SRS-22r questionnaires preoperatively and at 2 years postoperatively. The primary independent variable was patient age <60 vs. ≥60 years-old. Multivariable regression analyses were utilized. RESULTS:In total, 267 patients were analyzed. Patients <60 years-old (51.3%) and ≥60 years-old (48.7%) were evenly represented. In bivariable analysis, patients <60 years-old exhibited lower LSDI at baseline vs. patients ≥60 years-old (25.7 vs. 35.5, β -9.8, p<0.0001), but a directionally smaller difference at 2-years (26.4 vs. 32.3, β -5.8, p=0.0147). LSDI was associated with lower SRS-22r total score among both patients <60 and ≥60 years-old, at both baseline and 2-years (all p<0.0001); the association was stronger among patients <60 vs. ≥60 years-old at 2 years. LSDI was associated with SRS satisfaction scores at 2 years among patients <60 years-old (p<0.0001), but not patients ≥60 years-old (p=0.2250). The difference in SRS satisfaction per unit LSDI between patients <60 years-old and >60 years-old was significant (p=0.0021). CONCLUSIONS:Among ASD patients managed operatively, higher LSDI was associated with inferior SRS-22r total score and satisfaction at 2 years postoperatively. The association between increased LSDI and worse PROMs was greater among patients <60 vs. ≥60 years old. Pre-operative counseling is needed for patients <60 undergoing ASD surgery regarding the effects that lumbar stiffness may have on post-operative function and satisfaction.