Full-Body Radiographic Analysis of Postoperative Deviations From Age-Adjusted Alignment Goals in Adult Spinal Deformity Correction and Related Compensatory Recruitment.

BACKGROUND: Full-body stereographs for adult spinal deformity (ASD) have enhanced global deformity and lower-limb compensation associations. The advent of age-adjusted goals for classic ASD parameters (sagittal vertical axis, pelvic tilt, spino-pelvic mismatch [PI-LL]) has enabled individualized evaluation of successful versus failed realignment, though these remain to be radiographically assessed postoperatively. This study analyzes pre- and postoperative sagittal alignment to quantify patient-specific correction against age-adjusted goals, and presents differences in compensation in patients whose postoperative profile deviates from targets. METHODS: Single-center retrospective review of ASD patients ≥ 18 years with biplanar full-body stereographic x-rays. Inclusion: ≥ 4 levels fused, complete baseline and early (≤ 6-month) follow-up imaging. Correction groups generated at postoperative visit for actual alignment compared to age-adjusted ideal values for pelvic tilt, PI-LL, and sagittal vertical axis derived from clinically relevant formulas. Patients that matched exact ± 10-year threshold for age-adjusted targets were compared to unmatched cases (undercorrected or overcorrected). Comparison of spinal alignment and compensatory mechanisms (thoracic kyphosis, hip extension, knee flexion, ankle flexion, pelvic shift) across correction groups were performed with ANOVA and paired t tests. RESULTS: The sagittal vertical axis, pelvic tilt, and PI-LL of 122 patients improved at early postoperative visits (P < .001). Of lower-extremity parameters, knee flexion and pelvic shift improved (P < .001), but hip extension and ankle flexion were similar (P > .170); global sagittal angle decreased overall, reflecting global postoperative correction (8.3° versus 4.4°, P < .001). Rates of undercorrection to age-adjusted targets for each spino-pelvic parameter were 30.3% (sagittal vertical axis), 41.0% (pelvic tilt), and 43.6% (PI-LL). Compared to matched/overcorrections, undercorrections recruited increased posterior pelvic shift to compensate (P < .001); knee flexion was recruited in undercorrections for sagittal vertical axis and pelvic tilt; thoracic hypokyphosis was observed in PI-LL undercorrections. All undercorrected groups displayed consequentially larger global sagittal angle (P < .001). CONCLUSIONS: Global alignment cohort improvements were observed, and when comparing actual to age-adjusted alignment, undercorrections recruited pelvic and lower-limb flexion to compensate. LEVEL OF EVIDENCE: 3.

Spinal Fusion in Parkinson's Disease Patients: A Propensity Score-Matched Analysis With Minimum 2-Year Surveillance.

STUDY DESIGN: Retrospective analysis. OBJECTIVE: To compare outcomes and complication rates between patients with and without Parkinson's disease (PD) patients undergoing surgery for adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: There is limited literature evaluating the impact of PD on long-term outcomes after thoracolumbar fusion surgery for ASD. METHODS: Patients admitted from 2009 to 2011 with diagnoses of ASD who underwent any thoracolumbar fusion procedure with a minimum 2-year follow-up surveillance were retrospectively reviewed using New York State's Statewide Planning and Research Cooperative System. A 1:1 propensity score-match by age, Deyo score, and number of fused vertebral levels was conducted before comparing surgical outcomes of patients with ASD with and without PD. Univariate analysis compared demographics, complications, and subsequent revision. Multivariate binary stepwise logistic regression models identified independent predictors of these outcomes (covariates: age, sex, Deyo Index score, and PD diagnosis). RESULTS: A total of 576 propensity score-matched patients were identified (PD: n = 288; no-PD: n = 288), with a mean age of 69.7 years (PD) and 70.2 years (no-PD). Each cohort had comparable distributions of age, sex, race, insurance provider, Deyo score, and number of levels fused (all P > 0.05). Patients with PD incurred higher total charges across ASD surgery-related visits ($187,807 vs. $126,610, P < 0.001), yet rates of medical complications (35.8% PD vs. 34.0% no-PD, P = 0.662) and revision surgery (12.2% vs. 10.8%, P > 0.05) were comparable. Postoperative mortality rates were comparable between PD and no-PD cohorts (2.8% vs. 1.4%, P = 0.243). Logistic regression identified nine-level or higher spinal fusion as a significant predictor for an increase in total complications (odds ratio = 5.64); PD was not associated with increased odds of any adverse outcomes. CONCLUSION: Aside from higher hospital charges incurred, patients with PD experienced comparable overall complication and revision rates to a propensity score-matched patient cohort without PD from the general population undergoing thoracolumbar fusion surgery. These results can support management of concerns and postoperative expectations in this patient cohort. LEVEL OF EVIDENCE: 3.

Location of correction within the lumbar spine impacts acute adjacent-segment kyphosis.

OBJECTIVEThe surgical correction of adult spinal deformity (ASD) often involves modifying lumbar lordosis (LL) to restore ideal sagittal alignment. However, corrections that include large changes in LL increase the risk for development of proximal junctional kyphosis (PJK). Little is known about the impact of cranial versus caudal correction in the lumbar spine on the occurrence of PJK. The goal of this study was to investigate the impact of the location of the correction on acute PJK development.METHODSThis study was a retrospective review of a prospective multicenter database. Surgically treated ASD patients with early follow-up evaluations (6 weeks) and fusions of the full lumbosacral spine were included. Radiographic parameters analyzed included the classic spinopelvic parameters (pelvic incidence [PI], pelvic tilt [PT], PI-LL, and sagittal vertical axis [SVA]) and segmental correction. Using Glattes' criteria, patients were stratified into PJK and noPJK groups and propensity matched by age and regional lumbar correction (ΔPI-LL). Radiographic parameters and segmental correction were compared between PJK and noPJK patients using independent t-tests.RESULTSAfter propensity matching, 312 of 483 patients were included in the analysis (mean age 64 years, 76% women, 40% with PJK). There were no significant differences between PJK and noPJK patients at baseline or postoperatively, or between changes in alignment, with the exception of thoracic kyphosis (TK) and ΔTK. PJK patients had a decrease in segmental lordosis at L4-L5-S1 (-0.6° vs 1.6°, p = 0.025), and larger increases in segmental correction at cranial levels L1-L2-L3 (9.9° vs 7.1°), T12-L1-L2 (7.3° vs 5.4°), and T11-T12-L1 (2.9° vs 0.7°) (all p < 0.05).CONCLUSIONSAlthough achievement of an optimal sagittal alignment is the goal of realignment surgery, dramatic lumbar corrections appear to increase the risk of PJK. This study was the first to demonstrate that patients who developed PJK underwent kyphotic changes in the L4-S1 segments while restoring LL at more cranial levels (T12-L3). These findings suggest that restoring lordosis at lower lumbar levels may result in a decreased risk of developing PJK.

Lumbosacral stress and age may contribute to increased pelvic incidence: an analysis of 1625 adults.

PURPOSE: While there is a consensus that pelvic incidence (PI) remains constant after skeletal maturity, recent reports argue that PI increases after 60 years. This study aims to investigate whether PI increases with age and to determine potential associated factors. METHODS: 1510 patients with various spinal degenerative and deformity pathologies were enrolled, along with an additional 115 asymptomatic volunteers. Subjects were divided into six age subgroups with 10-year intervals. RESULTS: PI averaged 54.1° in all patients. PI was significantly higher in the 45-54-year age group than 35-44-year age group (55.8° vs. 49.7°). There were significant PI differences between genders after age 45. Linear regression revealed age, gender and malalignment as associated factors for increased PI with R 2 of 0.22 (p < 0.001). CONCLUSIONS: PI is higher in female patients and in older patients, especially those over 45 years old. Spinal malalignment also may have a role in increased PI due to increased L5-S1 bending moment.

Under Correction of Sagittal Deformities Based on Age-adjusted Alignment Thresholds Leads to Worse Health-related Quality of Life Whereas Over Correction Provides No Additional Benefit.

STUDY DESIGN: Retrospective review of prospectively-collected database. OBJECTIVE: This study aims to compare 2-year clinical outcomes of patients who underwent surgical reconstructions based on their achievement to age-adjusted alignment ideals. SUMMARY OF BACKGROUND DATA: Recent research in sagittal plane has proposed age-adjusted alignment thresholds. However, the impact of these thresholds on postoperative health-related quality of life (HRQOL) is yet to be investigated. METHODS: Patients were included if they were more than 18-years old and underwent surgical correction of adult spinal deformity with a complete 2-year follow-up. Patients were stratified into three groups based on achievement of age-adjusted thresholds in pelvic tilt (PT), pelvic incidence minus lumbar lordosis (PI-LL), and sagittal vertical axis (SVA). First group included patients who reached the exact age-adjusted threshold ±â€Š10 years (MATCHED), other two groups included patients who were over corrected (OVER), and under corrected (UNDER). Clinical outcomes including actual value and offset from age-adjusted Oswestry Disability Index, Short-Form-36 (SF-36) -physical component summary, and Scoliosis Research Society-22r (SRS-22r) were compared between groups at 2 years follow-up. RESULTS: A total of 343 patients (mean, 57 yrs and 83% females) were included. Sagittal profile of the population was: PT = 23.6°, SVA = 65.8 mm, and PI-LL = 15.6°. At 2-year follow-up, there was significant improvement in all sagittal modifiers with 25.7%, 24.3%, and 33.1% of the patients matching their age alignment targets in terms of PT, PI-LL, and SVA, respectively. For PT and PI-LL, the three groups (MATCHED, OVER, and UNDER) had comparable values and offsets from age-adjusted patient reported outcome. However, for SVA groups, patients in UNDER had significantly worse HRQOL than the two other groups. Patients in PT, PI-LL, and SVA UNDER groups were significantly younger than the other groups, P < 0.05. CONCLUSION: At 2 years after adult spinal deformity surgical treatment, only 24.3% to 33.1% of the patients reached age-adjusted alignment thresholds. Those under corrected in SVA demonstrated worse clinical outcomes. No significant improvements were found between matched and overcorrected patients, with overcorrection being an established risk for proximal junctional kyphosis. These results further emphasize the need for patient specific operative planning. LEVEL OF EVIDENCE: 3.

Three types of sagittal alignment regarding compensation in asymptomatic adults: the contribution of the spine and lower limbs.

PURPOSE: A comprehensive understanding of normative sagittal profile is necessary for adult spinal deformity. Roussouly described four sagittal alignment types based on sacral slope, lumbar lordosis, and location of lumbar apex. However, the lower limb, a newly described component of spinal malalignment compensation, is missing from this classification. This study aims to propose a full-body sagittal profile classification in an asymptomatic population based on full-body imaging. METHODS: This is a retrospective analysis of a prospective single-center study of 116 asymptomatic volunteers. Cluster analysis including all sagittal parameters was first performed, and then ANOVA was performed between sub-clusters to eliminate the non-significantly different parameters. This loop was repeated until all parameters were significantly different between each sub-cluster. RESULTS: Three types of full-body sagittal profiles were finalized according to cluster analysis with ten radiographic parameters: hyperlordosis type (77 subjects), neutral type (28 subjects), and compensated type (11 subjects). Radiographic parameters included knee angle, pelvic shift, pelvic angle, PT, PI-LL, C7-S1 SVA, TPA, T1 slope, C2-C7 angle, and C2-C7 SVA. Age was significantly different across compensation types, while BMI and gender were comparable. Age-matched subjects were randomly selected with 11 subjects in each type. ANOVA analysis revealed that all parameters but PT and C2-C7 angle remained significantly different. CONCLUSIONS: The current three compensation types of full-body sagittal profiles in asymptomatic adults included significant changes from cervical region to knee, indicating that subjects should be evaluated with full-length imaging. All three types exist regardless of age, but the distribution may vary.

Sagittal alignment and complications following lumbar 3-column osteotomy: does the level of resection matter?

OBJECTIVE Three-column osteotomy (3CO) is a demanding technique that is performed to correct sagittal spinal malalignment. However, the impact of the 3CO level on pelvic or truncal sagittal correction remains unclear. In this study, the authors assessed the impact of 3CO level and postoperative apex of lumbar lordosis on sagittal alignment correction, complications, and revisions. METHODS In this retrospective study of a multicenter spinal deformity database, radiographic data were analyzed at baseline and at 1- and 2-year follow-up to quantify spinopelvic alignment, apex of lordosis, and resection angle. The impact of 3CO level and apex level of lumbar lordosis on the sagittal correction was assessed. Logistic regression analyses were performed, controlling for cofounders, to investigate the effects of 3CO level and apex level on intraoperative and postoperative complications as well as on the need for subsequent revision surgery. RESULTS A total of 468 patients were included (mean age 60.8 years, mean body mass index 28.1 kg/m2); 70% of patients were female. The average 3CO resection angle was 25.1° and did not significantly differ with regard to 3CO level. There were no significant correlations between the 3CO level and amount of sagittal vertical axis or pelvic tilt correction. The postoperative apex level significantly correlated with greater correction of pelvic tilt (2° per more caudal level, R = -0.2, p = 0.006). Lower-level 3CO significantly correlated with revisions for pseudarthrosis (OR = 3.88, p = 0.001) and postoperative motor deficits (OR = 2.02, p = 0.026). CONCLUSIONS In this study, a more caudal lumbar 3CO level did not lead to greater sagittal vertical axis correction. The postoperative apex of lumbar lordosis significantly impacted pelvic tilt. 3CO levels that were more caudal were associated with more postoperative motor deficits and revisions.

Orientation of the Upper-most Instrumented Segment Influences Proximal Junctional Disease Following Adult Spinal Deformity Surgery.

STUDY DESIGN: Retrospective review of a prospective database. OBJECTIVE: The aim of this study was to define the role of sagittal orientation of the construct at the upper instrumented levels in the development of proximal junctional kyphosis (PJK) in adult spinal deformity (ASD) patients. SUMMARY OF BACKGROUND DATA: PJK following ASD surgery remains challenging. The final alignment of the upper instrumented vertebral segments has been proposed as a risk factor for PJK, but has not been fully investigated. METHODS: ASD patients with 2-year follow-up and long posterior fusion to the pelvis were analyzed. Radiographic measurements included pelvic incidence (PI), lumbar lordosis (LL), pelvic tilt (PT), sagittal vertical axis, and two upper-most instrumented vertebra (UIV) parameters: UIV slope (UIV vs. horizontal) and inclination of the proximal-end of the construct. UIV parameters were secondarily evaluated with regard to the compensatory impact of post-PJK increased PT (PREF). A comparison between PJK and non-PJK patients was performed, according to the UIV location (upper thoracic [UT] or thoracolumbar). RESULTS: A total of 252 patients (mean age, 61.5 years, 83% females) were included. PJK incidence was 56% at 2-years. PJK patients had a greater change in LL and thoracic kyphosis than non-PJK patients. In the UT group, there was no difference in UIV slope for PJK versus non-PJK. However, PJK patients had a smaller inclination of the upper instrumented segments versus vertical (P < 0.001) and the PREF (P = 0.005). Similarly, in the LT group, PJK patients had a posterior inclination versus the vertical (P < 0.001) and the PREF (P = 0.041). CONCLUSION: Analysis revealed that a more posterior construct inclination was present in patients who developed PJK. These results support previous hypotheses suggesting that PJK may develop in response to excessive spinal realignment. Proper rod contouring, especially at the proximal end, may reduce the risk of PJK. LEVEL OF EVIDENCE: 3.

Principal Radiographic Characteristics for Cervical Spinal Deformity: A Health-related Quality-of-life Analysis.

STUDY DESIGN: Retrospective study. OBJECTIVE: The aim of this study was to propose radiographic characteristics of patients with cervical disability and to investigate the relevant parameters when assessing cervical alignment. SUMMARY OF BACKGROUND DATA: Although cervical kyphosis is traditionally recognized as presentation of cervical deformity, an increasing number of studies demonstrated that cervical kyphosis may not equal cervical deformity. Therefore, several other differentiating criteria for cervical deformity should be investigated and supported with quality of life scores. METHODS: A database of full-body radiographs was retrospectively reviewed. Patients without previous cervical surgery, with a well-aligned thoracolumbar profile (defined as T1 pelvis angle <15°), and with an available Neck Disability Index (NDI) score were reviewed in this study. Subjects were stratified into an asymptomatic (64 subjects with NDI ≤15, Visual Analogue Scale [VAS] neck ≤3, and VAS arm ≤3) and a symptomatic group (107 subjects with NDI >15, VAS neck >3, or VAS arm >3). Independent t tests were performed to investigate differences between two groups. Logistic regressions and principal component analyses were then performed. RESULTS: NDI averaged 5.43 in asymptomatic group, significantly smaller than symptomatic group (5.43 vs. 41.25). t Test revealed that C2-C7 sagittal vertical axis (SVA), McGregor slope, and the slope of line of sight (SLS) were significantly different while C2-C7 angle (cervical curvature, CC) did not show statistical difference (P = 0.09). Logistic regressions were performed using the significantly different parameters as well as CC. Results identified C2-C7 SVA and SLS as independent risk factors for low health-related quality of life. The principal component analysis leads to a new factor (0.55 × C2C7SVA + 0.34 × COC2 + 0.77 × CC) with strong correlations with NDI, VAS, and EQ5D measurements. CONCLUSION: The traditional concept of cervical kyphosis should not be regarded as a standalone criterion of cervical deformity. The most clinically relevant components of cervical analysis are the C2-C7 SVA, C0C2 angle, and C2C7 angle. In addition, the three components should be assessed together in harmony and not individually. LEVEL OF EVIDENCE: 4.

Complication rates associated with 3-column osteotomy in 82 adult spinal deformity patients: retrospective review of a prospectively collected multicenter consecutive series with 2-year follow-up.

OBJECTIVE Although 3-column osteotomy (3CO) can provide powerful alignment correction in adult spinal deformity (ASD), these procedures are complex and associated with high complication rates. The authors' objective was to assess complications associated with ASD surgery that included 3CO based on a prospectively collected multicenter database. METHODS This study is a retrospective review of a prospectively collected multicenter consecutive case registry. ASD patients treated with 3CO and eligible for 2-year follow-up were identified from a prospectively collected multicenter ASD database. Early (≤ 6 weeks after surgery) and delayed (> 6 weeks after surgery) complications were collected using standardized forms and on-site coordinators. RESULTS Of 106 ASD patients treated with 3CO, 82 (77%; 68 treated with pedicle subtraction osteotomy [PSO] and 14 treated with vertebral column resection [VCR]) had 2-year follow-up (76% women, mean age 60.7 years, previous spine fusion in 80%). The mean number of posterior fusion levels was 12.9, and 17% also had an anterior fusion. A total of 76 early (44 minor, 32 major) and 66 delayed (13 minor, 53 major) complications were reported, with 41 patients (50.0%) and 45 patients (54.9%) affected, respectively. Overall, 64 patients (78.0%) had at least 1 complication, and 50 (61.0%) had at least 1 major complication. The most common complications were rod breakage (31.7%), dural tear (20.7%), radiculopathy (9.8%), motor deficit (9.8%), proximal junctional kyphosis (PJK, 9.8%), pleural effusion (8.5%), and deep wound infection (7.3%). Compared with patients who did not experience early or delayed complications, those who had these complications did not differ significantly with regard to age, sex, body mass index, Charlson Comorbidity Index, American Society of Anesthesiologists score, smoking status, history of previous spine surgery or spine fusion, or whether the 3CO performed was a PSO or VCR (p ≥ 0.06). Twenty-seven (33%) patients had 1-11 reoperations (total of 44 reoperations). The most common indications for reoperation were rod breakage (n = 14), deep wound infection (n = 15), and PJK (n = 6). The 24 patients who did not achieve 2-year follow-up had a mean of 0.85 years of follow-up, and the types of early and delayed complications encountered in these 24 patients were comparable to those encountered in the patients that achieved 2-year follow-up. CONCLUSIONS Among 82 ASD patients treated with 3CO, 64 (78.0%) had at least 1 early or delayed complication (57 minor, 85 major). The most common complications were instrumentation failure, dural tear, new neurological deficit, PJK, pleural effusion, and deep wound infection. None of the assessed demographic or surgical parameters were significantly associated with the occurrence of complications. These data may prove useful for surgical planning, patient counseling, and efforts to improve the safety and cost-effectiveness of these procedures.

Defining the Role of the Lower Limbs in Compensating for Sagittal Malalignment.

MINI: Despite differences in sagittal malalignment, antero-posterior pelvic translation maintained the position of T9 in line with the ankles, independently of sagittal vertical axis. Pelvic tilt was directly predicted by lower limb compensatory mechanisms. Therefore, these adaptation mechanisms being included in pelvic tilt analysis, it does not need additional consideration in the surgical planning. STUDY DESIGN: Retrospective review. OBJECTIVE: To investigate the role of lower limbs compensation with progressive sagittal malalignment. SUMMARY OF BACKGROUND DATA: Although lower limb compensatory mechanisms are established response to progressive sagittal malalignment, their specific role and potential impact on surgical planning has not been evaluated. METHODS: Single center retrospective review of full body x-rays was performed in patients of age >20 years. Parameters were measured with dedicated software. Population was stratified by 50 mm intervals of sagittal vertical axis (SVA) and one-way ANOVA was performed to compare P.shift (P.shift = anteroposterior translation of the pelvis vs. the feet) across SVA groups. Anteroposterior offset of each vertebra in relation to a vertical line extended from the distal tibial metaphysis (TM) was investigated. Linear regression was performed to predict pelvic tilt (PT) using Knee angle (KA) and P.shift, whereas controlling for pelvic incidence minus lumbar lordosis mismatch (PI-LL) and SVA. RESULTS: A total of 2124 patient visits were included (PI = 55.1 ±â€Š14.1°, PT=21.0 ±â€Š11°, PI-LL=6.3 ±â€Š17.3°, SVA = 29 ±â€Š51 mm). With progressively increased SVA, P.shift decreased from 30 to -100 mm (all P < 0.005). Analysis of vertebral offset from the distal tibial metaphysis revealed that T9 was aligned with the TM line across all SVA groups. Prediction of PT based on PI-LL and SVA yielded R=0.76 (P < 0.001). Subsequent addition of KA and P.shift as independent parameters using hierarchical multiple regression led to significant improvement in R, demonstrating the independent role of lower limbs parameters in PT prediction. KA and P.shift had a positive standardized coefficient (all P < 0.05). CONCLUSION: Lower limb compensatory mechanisms increase with progressive sagittal malalignment. Anteroposterior translation of pelvis allows the T9 vertebra to remain in line with the ankle ("conus of economy"). Lower limb compensatory mechanisms are positive predictors of PT and thus do not require additional consideration in surgical realignment planning. LEVEL OF EVIDENCE: 3.

Adult Scoliosis Deformity Surgery: Comparison of Outcomes Between One Versus Two Attending Surgeons.

STUDY DESIGN: Retrospective review of prospectively collected data. OBJECTIVE: Assess outcomes of adult spinal deformity (ASD) surgery performed by one versus two attending surgeons. SUMMARY OF BACKGROUND DATA: ASD centers have developed two attending teams to improve efficiency; their effects on complications and outcomes have not been reported. METHODS: Patients with ASD with five or more levels fused and more than 2-year follow-up were included. Estimated blood loss (EBL), length of stay (LOS), operating room (OR) time, complications, quality of life (Health Related Quality of Life), and x-rays were analyzed. Outcomes were compared between one-surgeon (1S) and two-surgeon (2S) centers. A deformity-matched cohort was analyzed. RESULTS: A total of 188 patients in 1S and 77 in 2S group were included. 2S group patients were older and had worse deformity based on the Scoliosis Research Society-Schwab classification (P < 0.05). There were no significant differences in levels fused (P = 0.57), LOS (8.7 vs 8.9 days), OR time (445.9 vs 453.2 min), or EBL (2008 vs 1898 cm; P > 0.05). 2S patients had more three-column osteotomies (3CO; P < 0.001) and used less bone morphogenetic protein 2 (BMP-2; 79.9% vs 15.6%; P < 0.001). The 2S group had fewer intraoperative complications (1.3% vs 11.1%; P = 0.006). Postoperative (6 wk to 2 yr) complications were more frequent in the 2S group (4.8% vs 15.6%; P < 0.002). After matching for deformity, there were no differences in (9.1 vs 10.1 days), OR time (467.8 vs 508.4 min), or EBL (3045 vs 2247 cm; P = 0.217). 2S group used less BMP-2 (20.6% vs 84.8%; P < 0.001), had fewer intraoperative complications (P = 0.015) but postoperative complications due to instrumentation failure/pseudarthrosis were more frequent (P < 0.01). CONCLUSION: No significant differences were found in LOS, OR time, or EBL between the 1S and 2S groups, even when matching for severity of deformity. 2S group had less BMP-2 use, fewer intraoperative complications but more postoperative complications. LEVEL OF EVIDENCE: 2.

Full-Body Analysis of Age-Adjusted Alignment in Adult Spinal Deformity Patients and Lower-Limb Compensation.

STUDY DESIGN: Single-center retrospective review. OBJECTIVE: The present study evaluates the effect of increasing spinal deformity deviation from age-adjusted alignment ideals on lower extremity compensation. SUMMARY OF BACKGROUND DATA: Although current understanding of compensatory mechanisms in adult spinal deformity (ASD) is progressing due to full-body stereographic assessment, the effect of age-adjusted deformity targets on lower-limb compensation remains unexamined. METHODS: ASD patients 18 years or older with biplanar full-body stereographic x-rays were included. Patients were stratified into age cohorts: younger than 40 years, 40-65 years, 65 years or older. Age-specific alignment goals (IDEAL) for pelvic tilt (PT), spinopelvic mismatch (PI-LL), sagittal vertical axis (SVA), and T1 pelvic angle (TPA) were calculated for each patient using published formulas and compared to patients' real (ACTUAL) radiographic parameters. The difference between ACTUAL and IDEAL alignment (OFFSET) was calculated. Analysis of variance compared ACTUAL, IDEAL, and OFFSET between age groups, and OFFSET was correlated with lower-limb compensation (sacrofemoral angle, pelvic shift, knee angle, ankle angle). RESULTS: Seven hundred seventy-eight patients with (74.1% female) were included. ACTUAL and IDEAL alignments matched for PT (P = 0.37) in patients younger than 40 years, SVA (P = 0.12) in patients 40 to 65 years and PT, SVA, and TPA (P > 0.05) in patients 65 years or older. SVA and TPA OFFSETs decreased significantly with increasing age (P < 0.001). Hip extension correlated with all OFFSETs in patients younger than 40 years (positively with PT, PI-LL, TPA; negatively with SVA). Knee flexion correlated with PI-LL, SVA, and TPA, across all age groups with strongest correlations (0.525 < r < 0.605) in patients 40 to 65 years. Ankle dorsiflexion only correlated positively with PT and PI-LL offsets in older (older than 40 years) age groups. Posterior pelvic displacement correlated positively with all OFFSET groups, and was highest (0.526 < r <0.712) in patients ages 40 to 65 years. CONCLUSION: Age-adjusted ideals for sagittal alignment provide targets for patients with ASD. Offsets from actual alignment (more severe sagittal deformity) revealed differential recruitment of lower-limb extension, which varied significantly with age. LEVEL OF EVIDENCE: 3.

Thoracolumbar Realignment Surgery Results in Simultaneous Reciprocal Changes in Lower Extremities and Cervical Spine.

STUDY DESIGN: A retrospective, clinical, and radiographic single-center study. OBJECTIVE: The aim of this study was to assess simultaneous cervical spine and lower extremity compensatory changes with changes in thoracolumbar spinal alignment. SUMMARY OF BACKGROUND DATA: Full-body stereoradiographic imaging allows better understanding of reciprocal changes in cervical and lower extremity alignment in the setting of thoracolumbar malalignment. Few studies describe the simultaneous effect of alignment correction on these mechanisms. METHODS: Patients aged ≥18 years undergoing instrumented thoracolumbar fusion without previous cervical spine fusion, hip, knee, or ankle arthroplasty were included. Spinopelvic, lower extremity, and cervical alignment were assessed from full-body standing stereoradiographs using validated software. Patients were matched for pelvic incidence and stratified on the basis of baseline T1-pelvic angle (TPA) as: TPA-Low <14°, TPA-Moderate = 14° to 22°, and TPA-High >22°. Perioperative changes between baseline and first postoperative visit <6 months in lower extremity alignment (pelvic shift: P Shift, sacrofemoral angle: SFA, knee angle: KA, ankle angle: AA, global sagittal axis: GSA) and cervical alignment (C0-C2 angle, C2-slope, C2-C7 lordosis and C2-C7 SVA:cSVA) were correlated with change in magnitude of TPA and sagittal vertical axis (SVA) correction. RESULTS: After matching, 87 patients were assessed. Increasing baseline TPA severity was associated with a progressive increase in all regional spinopelvic parameters except thoracic kyphosis, in addition to increased SFA, P Shift, KA, GSA, and C2-C7 lordosis. As TPA correction increased, there was a reciprocal reduction in SFA, KA, P Shift, GSA, and C2-C7 lordosis. Change in SVA correlated most with change in GSA (r = 0.886), P Shift (r = 0.601), KA (r = 0.534), and C2-C7 lordosis (r = 0.467). Change in TPA correlated with change in SFA (r = 0.372), while SVA did not. CONCLUSION: Patients with thoracolumbar malalignment exhibit compensatory changes in cervical spine and lower extremity simultaneously in the form of cervical hyperlordosis, pelvic shift, knee flexion, and pelvic retroversion. These compensatory mechanisms resolve reciprocally in a linear fashion following optimal surgical correction. LEVEL OF EVIDENCE: 3.

Is There a Gender-Specific Full Body Sagittal Profile for Different Spinopelvic Relationships? A Study on Propensity-Matched Cohorts.

DESIGN: Retrospective review. OBJECTIVE: To evaluate gender-related differences in compensatory recruitment to progressive sagittal malalignment. SUMMARY OF BACKGROUND DATA: Recent research has elucidated compensatory mechanisms recruited in response to sagittal malalignment, but gender-specific differences in compensatory recruitment patterns is unknown. METHODS: Single-center study of patients with full body x-rays. A female group was propensity matched by age, body mass index (BMI), and pelvic incidence (PI) to a male group. Patients were then stratified into five groups of progressive PI-lumbar lordosis (LL) mismatch (<0°, 0°-10°, 10°-20°, 20°-30°, >30°). Differences between PI-LL groups were assessed with analysis of variance, and between genders by unpaired t test. Knee flexion to pelvic tilt (PT) ratio was computed and compared between genders. Multivariate regression to develop predictive models for PT was performed for each gender, first with spinopelvic parameters and subsequently with inclusion of lower limb parameters. RESULTS: A total of 942 patient visits were included: 471 females (mean age 54 years, BMI 27, PI 51°) and 471 males (mean age 52 years, BMI 27, PI 51°). At the lowest level of malalignment, females had greater PT and less knee flexion. With progressive malalignment, females continued to exhibit a pattern of greater pelvic retroversion and less knee flexion compared to males. Hip extension was higher in females with progressive PI-LL mismatch groups. Both genders progressively recruited knee flexion and pelvic retroversion with increased PI-LL mismatch, except that at the higher PI-LL mismatch groups, only males continued to recruit knee flexion (all p < .05). Inclusion of lower limbs in the regression for PT markedly improved correlation coefficients for females but not for males. CONCLUSIONS: With progressive sagittal malalignment, men recruit more knee flexion and women recruit more pelvic tilt and hip extension. Knee flexion is a possible mechanism to gain pelvic tilt for females whereas for males, knee flexion is an independent compensatory mechanism.

Global sagittal axis: a step toward full-body assessment of sagittal plane deformity in the human body.

OBJECTIVE Sagittal malalignment requires higher energy expenditure to maintain an erect posture. Because the clinical impact of sagittal alignment is affected by both the severity of the deformity and recruitment of compensatory mechanisms, it is important to investigate new parameters that reflect both disability level and compensatory mechanisms for all patients. This study investigated the clinical relevance of the global sagittal axis (GSA), a novel measure to evaluate the standing axis of the human body. METHODS This is a retrospective review of patients who underwent full-body radiographs and completed health-related quality of life (HRQOL) questionnaires: Oswestry Disability Index (ODI), Scoliosis Research Society-22, EuroQol-5D (EQ-5D), and the visual analog scale for back and leg pain. The GSA was defined as the angle formed by a line from the midpoint of the femoral condyles to the center of C-7, and a line from the midpoint between the femoral condyles to the posterior superior corner of the S-1 sacral endplate. After evaluating the correlation of GSA/HRQOL with sagittal parameters, linear regression models were generated to investigate how ODI and GSA related to radiographic parameters (T-1 pelvic angle, pelvic retroversion, knee flexion, and pelvic posterior translation). RESULTS One hundred forty-three patients (mean age 44 years) were included. The GSA correlated significantly with all HRQOL (up to r = 0.6 with EQ-5D) and radiographic parameters (up to r = 0.962 with sagittal vertical axis). Regression between ODI and sagittal radiographic parameters identified the GSA as an independent predictor (r = 0.517, r2 = 0.267; p < 0.001). Analysis of standardized coefficients revealed that when controlling for deformity, the GSA increased with a concurrent decrease in pelvic retroversion (-0.837) and increases in knee flexion (+0.287) and pelvic posterior translation (+0.193). CONCLUSIONS The GSA is a simple, novel measure to assess the standing axis of the human body in the sagittal plane. The GSA correlated highly with spinopelvic and lower-extremities sagittal parameters and exhibited remarkable correlations with HRQOL, which exceeded other commonly used parameters.

Predicting Cervical Alignment Required to Maintain Horizontal Gaze Based on Global Spinal Alignment.

STUDY DESIGN: A retrospective cohort. OBJECTIVE: The aim of this study was to investigate the cervical alignment necessary for the maintenance of horizontal gaze that depends on underlying thoracolumbar alignment. SUMMARY OF BACKGROUND DATA: Cervical Sagittal Curve (CC) is affected by thoracic and global alignment. Recent studies suggest large variability in normative CC ranging from lordotic to kyphotic alignment. No previous studies have assessed the effect of global spinal alignment on CC in maintenance of horizontal gaze. METHODS: Patients without previous history of spinal surgery and able to maintain their horizontal gaze while undergoing full body imaging were included. Patients were stratified on the basis of thoracic kyphosis (TK) into (<30, 30-40, 40-50, and >50) and then by SRS-Schwab sagittal vertical axis (SVA) modifier into (posterior alignment SVA <0, aligned 0-50, and malaligned >50 mm). Cervical alignment was assessed among SVA grade in TK groups. Stepwise linear regression analysis was applied on random selection of 60% of the population. A simplified formula was developed and validated on the remaining 40%. RESULTS: In each TK group (n = 118, 137, 125, 197), lower CC (C2-C7) was significantly more lordotic by increased Schwab SVA grade. T1 slope and cervical SVA significantly increased with increased thoracolumbar (C7-S1) SVA. Upper CC (C0-C2) and mismatch between T1 slope and CC (T1-CL) were similar. Regression analysis revealed LL minus TK (LL-TK) as an independent predictor (r = 0.640, r = 0.410) with formula: CC = 10- (LL-TK)/2. Validation revealed that the absolute difference between the predicted CC and the actual CC was 8.5°. Moreover, 64.2% of patients had their predicted C2-C7 values within 10° of the actual CC. CONCLUSION: Cervical kyphosis may represent normal alignment in a significant number of patients. However, in patients with SVA >50 and greater thoracic kyphosis, cervical lordosis is needed to maintain the gaze. Cervical alignment can be predicted from underlying TK and lumbar lordosis, which may be clinically relevant when considering correction for thoracolumbar or cervical deformityLevel of Evidence: 3.

A comparative analysis of the prevalence and characteristics of cervical malalignment in adults presenting with thoracolumbar spine deformity based on variations in treatment approach over 2 years.

PURPOSE: Characteristics specific to cervical deformity (CD) concomitant with adult thoracolumbar deformity (TLD) remains uncertain, particularly regarding treatment. This study identifies cervical malalignment prevalence following surgical and conservative TLD treatment through 2 years. METHODS: Retrospective analysis of a prospective, multicenter adult spinal deformity (ASD) database. CD was defined in operative and non-operative ASD patients according to the following criteria: T1 Slope minus Cervical Lordosis (T1S-CL) ≥20°, C2-C7 Cervical Sagittal Vertical Axis (cSVA) ≥40 mm, C2-C7 kyphosis >10°. Differences in rates, demographics, health-related quality of life (HRQoL) scores for Oswestry Disability Index (ODI) and Scoliosis Research Society Questionnaire (SRS-22r), and radiographic variables were assessed between treatment groups (Op vs. Non-Op) and follow-up periods (baseline, 1-year, 2-year). RESULTS: Three hundred and nineteen (200 Op, 199 Non-Op) ASD patients were analyzed. Op patients' CD rates at 1 and 2 years were 78.9, and 63.0 %, respectively. Non-Op CD rates were 21.1 and 37.0 % at 1 and 2 years, respectively. T1S-CL mismatch and cSVA malalignment characterized Op CD at 1 and 2 years (p < 0.05). Op and Non-Op CD groups had similar cervical/global alignment at 1 year (p > 0.05 for all), but at 2 years, Op CD patients had worse thoracic kyphosis (TK), T1S-CL, CL, cSVA, C2-T3 SVA, and global SVA compared to Non-Ops (p < 0.05). Op CD patients had worse ODI, and SRS Activity at 1 and 2 years post-operative (p < 0.05), but had greater 2-year SRS Satisfaction scores (p = 0.019). CONCLUSIONS: In the first study to compare cervical malalignment at extended follow-up between ASD treatments, CD rates rose overall through 2 years. TLD surgery, resulting in higher CD rates characterized by T1S-CL and cSVA malalignment, produced poorer HRQoL. This information can aid in treatment method decision-making when cervical deformity is present concomitant with TLD.

When is compensation for lumbar spinal stenosis a clinical sagittal plane deformity?

BACKGROUND CONTEXT: Degenerative lumbar stenosis (DLS) patients have been reported to lean forward in an attempt to provide neural decompression. Spinal alignment in patients with DLS may resemble that of adult spinal deformity (ASD). No previous studies have compared and contrasted the compensatory mechanisms of DLS and ASD patients. PURPOSE: This study aimed to determine the differences in compensatory mechanisms between DLS and ASD patients with increasing severity of sagittal spinopelvic malalignment. Contrasting these compensatory mechanisms may help determine at what severity sagittal malalignment represents a clinical sagittal deformity rather than a compensation for neural compression. STUDY DESIGN/SETTING: This is a retrospective clinical and radiological review. PATIENT SAMPLE: Baseline x-rays in patients without spinal instrumentation, with the clinical radiological and diagnoses of DLS or ASD, were assessed for patterns of spinopelvic compensatory mechanisms. Patients were stratified by sagittal vertical axis (SVA) according to the Scoliosis Research Society-Schwab [SRS-Schwab] classification. OUTCOME MEASURES: Radiographic spinopelvic parameters were measured in the DLS and ASD groups, including SVA, pelvic incidence-lumbar lordosis mismatch (PI-LL), T1 spinopelvic inclination (T1SPi), T1 pelvic angle (TPA), and pelvic tilt (PT). METHODS: The two diagnosis cohorts were propensity-matched for PI and age. Each group contained 125 patients and was stratified according to the SRS-Schwab classification. Regional spinopelvic,lower limb, and global alignment parameters were assessed to identify differences in compensatory mechanisms between the two groups with differing degrees of deformity. No funding was provided by any third party in relation to carrying out this study or preparing the manuscript. RESULTS: With mild to moderate malalignment (SRS-Schwab groups "0," or "+" for PT, PI-LL, or SVA), DLS patients permit anterior truncal inclination and recruit posterior pelvic shift instead of pelvic tilt to maintain balance, while providing relief of neurologic symptoms. Adult spinal deformity patients with mild to moderate deformity recruit pelvic tilt earlier than DLS patients. With moderate to severe malalignment, no significant difference was found in compensatory mechanisms between DLS and ASD patients. CONCLUSIONS: Patients with DLS permit mild to moderate deformity without recruiting compensatory mechanisms of PT, reducing truncal inclination and thoracic hypokyphosis to achieve neural decompression. However, with moderate to severe deformity, their desire for upright posture overrides the desire for neural decompression, evident by the adaptation of compensatory mechanisms similar to that of ASD patients.

Variability Over Time of Preoperative Sagittal Alignment Parameters: Radiographic and Clinical Considerations.

STUDY DESIGN: Retrospective review. OBJECTIVE: To evaluate preoperative variability in radiographic sagittal parameters in adult spinal deformity (ASD). SUMMARY OF BACKGROUND DATA: In ASD surgical planning, deformity magnitude is determined from preoperative radiographs. There are no studies evaluating the clinical relevance and timing to repeat radiographs during interval clinic visits and timing to repeat radiograph for preoperative planning. METHODS: A total of 139 patients with ASD with minimum two preoperative full-body spine x-rays were included. Cervical, thoracic, lumbar, pelvic, and hip/knee sagittal alignment parameters were analyzed using dedicated spine measurement software. Patients were grouped by time intervals between x-rays: A: 8 weeks or lesser, B: 10 to 20 weeks, and C: 21 weeks or more. Changes in sagittal parameters were correlated to age and deformity magnitude (T1 pelvic angle or pelvic tilt [PT] >20°). RESULTS: The cohort had mean age 59 years, mean body mass index 27, 30% men, 95 patients with no prior spine surgery, and 44 patients at minimum 9 months since prior spine surgery. There were 25 patients in group A, 38 in B, and 71 in C. All radiographic measures showed good time-based consistency at intervals less than 21 weeks (groups A and B). Group C had significant increases in PT (1.5°) and hip extension (2.1°) (P < 0.05). These changes were greater in group C patients with previous surgery (PT 3.7°; P < 0.006, hip extension 3.2°; P < 0.025). Greater interval changes in parameters were also associated with higher magnitudes of deformity and younger patient ages. CONCLUSION: All sagittal radiographic parameters were statistically consistent at intervals of less than 21 weeks. In patients with more than 21 weeks between interval x-rays, change in PT was greater than the standard error of measurement for patients with prior surgery or severe deformity. Consideration should be made to obtain new x-rays for patients with ASD when the interval between clinical visits exceeds 5 months. LEVEL OF EVIDENCE: 4.