Applying the ICF model in adult spinal deformity: disability in terms of participation should be incorporated in the care pathway.

PURPOSE: To investigate the participation restriction of adult spinal deformity (ASD) patients, and its relation with the impairments in body structure and function, and activity limitation, as this important information regarding the individual's perspective on the social impact of the disease on their life is presently not captured. METHODS: Forty-three ASD patients participated in the study and completed the impact on participation and autonomy (IPA) questionnaire to assess the level of participation. Activity limitations and impairments were measured with the Balance Evaluation Systems Test (BESTest) and Scoliosis Research Society-22r (SRS-22). Also, age, body height, body weight, BMI, Mini-mental state examination and Cumulative Illness Rating Scale were assessed. A univariate linear regression analysis was conducted to investigate the relationship between the IPA and the independent variables, whereas a multivariate analysis identified the significant predictive variables for the IPA questionnaire. RESULTS: The univariate analysis identified performance on the BESTest and SRS-22 as significantly (p < 0.001) related to the IPA questionnaire. The multiple regression analysis revealed that the performance on BESTest (p = 0.073) and SRS-22 (p < 0.001) independently predicted the IPA questionnaire, explaining 73.5% of its variance. CONCLUSION: To fully understand the impact of ASD on the individual's functioning, disability and health-status, it is suggested that questionnaires on participation to society should be considered, together with clinical postural tests (e.g. the BESTest) and questionnaires related to HRQOL (e.g. the SRS-22), in the ASD care path. This additional information should allow the surgeon to make a more informed selection of surgical patients.

The Function Assessment Scale for Spinal Deformity: Validity and Reliability of a New Clinical Scale.

STUDY DESIGN: Cross-sectional study. OBJECTIVE: The aim of this study was to develop and validate the Function Assessment scale for Spinal Deformity (FASD). SUMMARY OF BACKGROUND DATA: Spinal malalignment impacts daily functioning. Standard evaluation of adult spinal deformity (ASD) is based on static radiography and patient-reported scores, which fail to assess functional impairments. A clinical scale, quantifying function and balance of patients with ASD, could increase our insights on the impact of ASD on functioning. METHODS: To develop the FASD, 70 ASD patients and 20 controls were measured to identify the most discriminating items of the Balance Evaluation Systems Test and Trunk Control Measurement Scale. Discussions between experts on the clinical relevance of selected items led to further item reduction. The FASD's discriminative ability was established between 43 patients and 19 controls, as well as between three deformity subgroups. For its responsiveness to treatment, 10 patients were reevaluated 6 months postoperatively. Concurrent validity was assessed through correlation analysis with radiographic parameters (pelvic tilt; sagittal vertical axis [SVA]; pelvic incidence minus lumbar lordosis [PI-LL]; coronal vertical axis) and patient-reported scores [Oswestry Disability Index]; Scoliosis Research Society outcome questionnaire; Falls Efficacy Scale-International). Test-retest and interrater reliability were tested on two groups of ten patients using intraclass correlation coefficients (ICC). RESULTS: Patients with ASD, mainly with sagittal malalignment, scored worse compared to controls on FASD (P < 0.001) and its subscales. No significant improvement was observed 6 months postoperatively (P = 0.758). FASD correlated significantly to all patient-reported scores and to SVA and PI-LL. Reliability between sessions (ICC = 0.97) and raters (ICC = 0.93) was excellent. Subscales also showed good to excellent reliability, except FASD 1 on "spinal mobility and balance" between sessions (ICC = 0.71). CONCLUSION: FASD proved to be a valid and reliable clinical scale for evaluation of functional impairments in ASD. Objective information on function and balance might ultimately guide physiotherapeutic treatment toward improved functioning.Level of Evidence: 2.

Spinopelvic movement strategies during sit-to-stand and stand-to-sit in adult spinal deformity.

BACKGROUND: Research interest on the impact of adult spinal deformity (ASD) on spinopelvic and whole body motion has increased over the past years. Studies focusing on overground walking, showed that patients with ASD indeed present with functional impairments. Functional tasks challenging the spinopelvic complex, such as sit-to-stand-to-sit, might identify clinically relevant biomechanical parameters and could further increase our insights on how ASD impacts functioning and disability. RESEARCH QUESTION: Do patients with ASD use different spinopelvic strategies during sit-to-stand (STSt) and stand-to-sit (StTS) compared to healthy controls? METHODS: In this prospective study, marker-based motion analysis and a subject-specific polynomial fit were used to assess spinopelvic kinematics (thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), trunk, pelvis) during STSt/StTS in 42 patients with ASD and 18 control subjects. All parameters were compared between controls and patients with ASD, divided in three groups based on their sagittal alignment (ASD 1: decompensated sagittal malalignment; ASD 2: compensated sagittal malalignment; ASD 3: scoliosis and normal sagittal alignment). Continuous kinematic and kinetic data were analyzed through statistical parametric mapping. RESULTS: Patients with ASD showed decreased LL and increased trunk flexion and SVA during STSt/StTS compared to controls. These differences were mainly observed in sagittal deformity patients (ASD 1 and 2). In contrast, coronal patients (ASD 3) did not differ from controls. Dynamic LL and SVA significantly correlated with radiographic LL and SVA, however these relations decreased during the middle third of the motion cycle. SIGNIFICANCE: Patients with ASD use aberrant spinopelvic strategies during STSt/StTS compared to healthy controls. Only partial correlation to static radiographic parameters suggests other mechanisms need to be identified in addition to spinal malalignment. These might include impaired neuromuscular control or muscle weakness. Further research on movement patterns during functional tasks might ultimately result in treatment strategies that aim to augment activity participation by targeting improvements in movement function.

Subject-Specific Spino-Pelvic Models Reliably Measure Spinal Kinematics During Seated Forward Bending in Adult Spinal Deformity.

Image-based subject-specific models and simulations are recently being introduced to complement current state-of-the-art mostly static insights of the adult spinal deformity (ASD) pathology and improve the often poor surgical outcomes. Although the accuracy of a recently developed subject-specific modeling and simulation framework has already been quantified, its reliability to perform marker-driven kinematic analyses has not yet been investigated. The aim of this work was to evaluate the reliability of this subject-specific framework to measure spine kinematics in ASD patients, in terms of 1) the overall test-retest repeatability; 2) the inter-operator agreement of spine kinematic estimates; and, 3) the uncertainty of those spine kinematics to operator-dependent parameters of the framework. To evaluate the overall repeatability 1], four ASD subjects and one control subject participated in a test-retest study with a 2-week interval. At both time instances, subject-specific spino-pelvic models were created by one operator to simulate a recorded forward trunk flexion motion. Next, to evaluate inter-operator agreement 2], three trained operators each created a model for three ASD subjects to simulate the same forward trunk flexion motion. Intraclass correlation coefficients (ICC's) of the range of motion (ROM) of conventional spino-pelvic parameters [lumbar lordosis (LL), sagittal vertical axis (SVA), thoracic kyphosis (TK), pelvic tilt (PT), T1-and T9-spino-pelvic inclination (T1/T9-SPI)] were used to evaluate kinematic reliability 1] and inter-operator agreement 2]. Lastly, a Monte-Carlo probabilistic simulation was used to evaluate the uncertainty of the intervertebral joint kinematics to operator variability in the framework, for three ASD subjects 3]. LL, SVA, and T1/T9-SPI had an excellent test-retest reliability for the ROM, while TK and PT did not. Inter-operator agreement was excellent, with ICC values higher than test-retest reliability. These results indicate that operator-induced uncertainty has a limited impact on kinematic simulations of spine flexion, while test-retest reliability has a much higher variability. The definition of the intervertebral joints in the framework was identified as the most sensitive operator-dependent parameter. Nevertheless, intervertebral joint estimations had small mean 90% confidence intervals (1.04°-1.75°). This work will contribute to understanding the limitations of kinematic simulations in ASD patients, thus leading to a better evaluation of future hypotheses.

Spinal Palpation Error and Its Impact on Skin Marker-Based Spinal Alignment Measurement in Adult Spinal Deformity.

Spinal alignment measurement in spinal deformity research has recently shifted from using mainly two-dimensional static radiography toward skin marker-based motion capture approaches, allowing three-dimensional (3D) assessments during dynamic conditions. The validity and accuracy of such skin marker-based methods is highly depending on correct marker placement. In this study we quantified, for the first time, the 3D spinal palpation error in adult spinal deformity (ASD) and compared it to the error in healthy spines. Secondly, the impact of incorrect marker placement on the accuracy of marker-based spinal alignment measurement was investigated. 3D, mediolateral and inferosuperior palpation errors for thoracolumbar and lumbar vertebral levels were measured on biplanar images by extracting 3D positions of skin-mounted markers and their corresponding anatomical landmarks in 20 ASD and 10 healthy control subjects. Relationships were investigated between palpation error and radiographic spinal alignment (lordosis and scoliosis), as well as body morphology [BMI and soft tissue (ST) thickness]. Marker-based spinal alignment was measured using a previously validated method, in which a polynomial is fit through the marker positions of a motion trial and which allows for radiograph-based marker position correction. To assess the impact of palpation error on spinal alignment measurement, the agreement was investigated between lordosis and scoliosis measured by a polynomial fit through, respectively, (1) the uncorrected marker positions, (2) the palpation error-corrected (optimal) marker positions, and (3) the anatomically corrected marker positions (toward the vertebral body), and their radiographic equivalents expressed as Cobb angles (ground truth), using Spearman correlations and root mean square errors (RMSE). The results of this study showed that, although overall accuracy of spinal level identification was similar across groups, mediolateral palpation was less accurate in the ASD group (ASDmean: 6.8 mm; Controlmean: 2.5 mm; p = 0.002). Significant correlations with palpation error indicated that determining factors for marker misplacement were spinal malalignment, in particular scoliotic deformity (r = 0.77; p < 0.001), in the ASD group and body morphology [i.e., increased BMI (r s = 0.78; p = 0.008) and ST thickness (r s = 0.66; p = 0.038)] in healthy spines. Improved spinal alignment measurements after palpation error correction, shows the need for radiograph-based marker correction methods, and therefore, should be considered when interpreting spinal kinematics.

A Dynamic Optimization Approach for Solving Spine Kinematics While Calibrating Subject-Specific Mechanical Properties.

This study aims to propose a new optimization framework for solving spine kinematics based on skin-mounted markers and estimate subject-specific mechanical properties of the intervertebral joints. The approach enforces dynamic consistency in the entire skeletal system over the entire time-trajectory while personalizing spinal stiffness. 3D reflective markers mounted on ten vertebrae during spine motions were measured in ten healthy volunteers. Biplanar X-rays were taken during neutral stance of the subjects wearing the markers. Calculated spine kinematics were compared to those calculated using inverse kinematics (IK) and IK with imposed generic kinematic constraints. Calculated spine kinematics compared well with standing X-rays, with average root mean square differences of the vertebral body center positions below 10.1 mm and below [Formula: see text] for joint orientation angles. For flexion/extension and lateral bending, the lumbar rotation distribution patterns, as well as the ranges of rotations matched in vivo literature data. The approach outperforms state-of-art IK and IK with constraints methods. Calculated ratios reflect reduced spinal stiffness in low-resistance zone and increased stiffness in high-resistance zone. The patterns of calibrated stiffness were consistent with previously reported experimentally determined patterns. This approach will further our insight into spinal mechanics by increasing the physiological representativeness of spinal motion simulations.

Dynamic sagittal alignment and compensation strategies in adult spinal deformity during walking.

BACKGROUND CONTEXT: Radiographic evaluation in adult spinal deformity (ASD) offers no information on spinopelvic alignment and compensation during dynamic conditions. Motion analysis offers the potential to bridge the gap between static radiographic and dynamic alignment measurement, increasing our understanding on how ASD impacts function. PURPOSE: This study aimed to explore the changes in sagittal alignment and compensation strategies in ASD between upright standing and walking, compared to control subjects and within different sagittal alignment groups. Ten patients were measured pre- and six months postoperatively to explore the impact of surgical alignment correction on gait. STUDY DESIGN: Prospective study. SAMPLE SIZE: Full protocol: 58 ASD and 20 controls; Spinal kinematic analysis: 43 ASD and 18 controls; Postoperative analysis: 10 ASD. OUTCOME MEASURES: Standing and walking sagittal spinopelvic (thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvis), and lower limb kinematics, spinopelvic changes between standing and walking (∆ ie, difference between mean dynamic and static angle), lower limb kinetics, spatiotemporal parameters, balance (BESTest), patient-reported outcome scores (SRS-22r, ODI, and FES-I) and radiographic parameters. METHODS: Motion analysis was used to assess the standing and walking spinopelvic and lower limb kinematics, as well as the lower limb kinetics during walking. All parameters were compared between controls and patients with ASD, divided in three groups based on their sagittal alignment (ASD 1: decompensated sagittal malalignment; ASD 2: compensated sagittal malalignment; ASD 3: scoliosis and normal sagittal alignment). Ten patients were reassessed 6 months after spinal corrective surgery. Continuous kinematic and kinetic data were analyzed through statistical parametric mapping. RESULTS: All patient groups walked with increased forward trunk tilt (∆SVA=41.43 mm, p<.001) in combination with anterior pelvic tilt (∆Pelvis=2.58°, p<.001) compared to standing, as was also observed in controls (∆SVA=37.86 mm, p<.001; ∆Pelvis=1.62°, p=.012). Patients walked with increased SVA, in combination with decreased LL and alterations in lower limb kinematics during terminal stance and initial swing, as well as altered spatiotemporal parameters. Subgroup analysis could link these alterations in gait to sagittal spinopelvic malalignment (ASD 1 and 2). After surgical correction, lower limb kinematics and spatiotemporal parameters during gait were not significantly improved. CONCLUSIONS: To compensate for increased trunk tilt and pelvic anteversion during walking, patients with sagittal malalignment show altered lower limb gait patterns, which have previously been associated with increased risk of falling and secondary lower limb pathology. Since surgical correction of the deformity did not lead to gait improvements, further research on the underlying mechanisms is necessary to improve our understanding of how ASD impacts function.

Development and validation of a modeling workflow for the generation of image-based, subject-specific thoracolumbar models of spinal deformity.

Quantitative dynamic evaluation of spino-pelvic motion in subjects with spinal deformity using optical motion analysis is currently lacking. The aim of this study was to develop and validate subject-specific, thoracolumbar spine multi-body skeletal models for evaluating spino-pelvic kinematics in a spinal deformity population. A new workflow for creating subject-specific spino-pelvic models in a weight-bearing position through computed tomography (CT) and biplanar radiography is described. As part of a two-step validation process the creation of such a model was first validated against a ground truth CT reconstruction of a plastinated cadaver. Secondly, biplanar radiographic images of one healthy and 12 adult spinal deformity subjects were obtained in two standing positions: upright and bent. Two subject-specific models for each of these subjects were then created to represent both standing positions. The result of inverse kinematics solutions, simulating the specific bending motion using the upright models, are compared with the models created in bent position, quantifying the marker-based spino-pelvic tracking accuracy. The workflow created spinal deformity models with mean accuracies between 0.71-1.95 mm and 1.25-2.27° for vertebral positions and orientations, respectively. In addition, the mean marker-based spino-pelvic tracking accuracies were between 0.9-1.8 mm and 2.9-5.6° for vertebral positions and rotations, respectively. This study presented the first validated biplanar radiography-based method to generate subject-specific spino-pelvic, rigid body models that allows the inclusion of subject-specific bone geometries, the personalization of the 3D weight-bearing spinal alignment with accuracy comparable to clinically used software for 3D reconstruction, and the localization of external markers in spinal deformity subjects. This work will allow new concepts of dynamic functionality evaluation of patients with spinal deformity.

A subject-specific method to measure dynamic spinal alignment in adult spinal deformity.

BACKGROUND CONTEXT: Two-dimensional static radiography currently forms the golden standard in spinal alignment measurement in adult spinal deformity (ASD). However, these static measurements offer no information on dynamic spinal behavior. To fully understand the functionality and compensation strategies of ASD patients, tools to assess dynamic spinal alignment are needed. PURPOSE: Therefore, the aim of this study was to introduce, validate and assess the reliability of a new kinematic model to measure dynamic spinal parameters in ASD based on a polynomial function, taking into account the subject-specific anatomy. STUDY DESIGN: Validation and reliability study OUTCOME MEASURES: Radiographic parameters, spinal kinematics and range of motion (ROM), Scoliosis Research Society Outcome Questionnaire (SRS-22), Core Outcome Measures Index (COMI). METHODS: Spinal alignment of 23 ASD patients and 18 controls was measured using both x-rays and motion capture. Marker positions were corrected to the underlying anatomy and a polynomial function was fitted through these corrected marker positions. By comparing the polynomial method to x-ray measurements concurrent validity was assessed. Test-retest, inter- and intrarater reliability during standing and sit-to-stand (STS) were assessed on a subsample of eight ASD patients and eight controls. RESULTS: The results showed good to excellent correlations (r>0.75) between almost all x-ray and anatomy-corrected polynomial parameters. Anatomy correction consistently led to better correlations than no correction. Intraclass correlation coefficients for the polynomial method were good to excellent (>0.75) between sessions and between and within raters and comparable or even better than radiographic measurements. Also, during STS reliability was excellent. Fair to moderate correlations were found between spinal ROM during STS and quality of life, measured with SRS-22 and COMI. CONCLUSIONS: The results of this study indicate the polynomial method, with subject-specific anatomy correction, can measure spinal alignment in a valid and reliable way using motion capture in both healthy and deformed spines. This method makes it possible to extend evaluation in ASD from mainly static, by means of x-ray measurements, to dynamic and functional assessments. CLINICAL SIGNIFICANCE: Eventually, this newly obtained dynamic spinal alignment information might lead to new insights in clinical decision-making and new treatment strategies, based and oriented on dynamic parameters and functionality.

The Transverse Gravitational Deviation Index, a Novel Gravity Line-Related Spinal Parameter, Relates to Balance Control and Health-Related Quality of Life in Adults With Spinal Deformity.

STUDY DESIGN: Prospective cross-sectional case-control study design. OBJECTIVE: This study aims to analyze the relation between balance control as well as health-related quality of life (HRQOL) in patients with adult spinal deformity (ASD), with a novel gravity line (GL)-related 3D spinal alignment parameter, the transverse gravitational deviation index (TGDI), defined to quantify the transverse plane position of any vertebra with respect to the GL. SUMMARY OF BACKGROUND DATA: Demographic data and balance control have both been identified as important determinants of HRQOL in ASD patients during a preoperative setting. Therefore, a better understanding of the relation between spinal alignment and balance is required. METHODS: After informed consent, 15 asymptomatic healthy volunteers (mean age 60.1 ±â€Š11.6 years old) and 55 ASD patients (mean age 63.5 ±â€Š10.1 years old) were included. Relation between performance on BESTest as well as core outcome measures index (COMI) with spinopelvic alignment was explored using General Linear Modeling (GLM). A P-value ≤0.05 was considered statistically significant. RESULTS: The L3 TGDI was identified to relate to balance control in the total ASD population after correction for confounding demographic factors (P = 0.001; adjusted R = 0.500) and explained 19% of the observed variance in balance performance. In addition, COMI is related to L3 TGDI in a subgroup of ASD patients with combined coronal and sagittal malalignment of L3 (P = 0.027; slope B = 0.047), despite significant influence of age (P = 0.020). CONCLUSION: In ASD patients with a combined coronal and sagittal malalignment of the L3 vertebra, both the level of balance impairment as well as HRQOL are related to the distance component of the L3 TGDI, that is, the offset between the center of the L3 vertebral body and the GL in the transverse plane. LEVEL OF EVIDENCE: 2.

Reliability of the balance evaluation systems test and trunk control measurement scale in adult spinal deformity.

OBJECTIVE: To test the reliability of the Balance Evaluation Systems Test (BESTest) and Trunk Control Measurement Scale (TCMS) between sessions and raters in the adult spinal deformity (ASD) population. SUMMARY OF BACKGROUND DATA: Up to now evaluation in ASD was mainly based on static radiographic parameters. Recently literature showed that dynamic balance was a better predictor of health-related quality of life than radiographic parameters, stressing the importance of balance assessment. However, to the best of our knowledge, reliability of balance assessment tools has not yet been investigated in the ASD population. METHODS: Twenty ASD patients participated in this study. Ten patients were included in the test-retest study, including repeated measurements. Ten patients were measured once, simultaneously but independently by three raters. Each participant performed two balance scales, namely the BESTest and the TCMS. Statistical analysis consisted of intra class correlations (ICC) on scale- and subscale level, and kappa scores on item-level. Cronbach's alpha on total scores, standard errors of measurement (SEM), smallest detectable differences and percentages of agreement were also calculated. Bland-altman plots were created to investigate systematic bias. RESULTS: ICC scores between sessions and raters for TCMS (0.76 and 0.88) and BESTest (0.90 and 0.94) total scores were good to excellent. SEM's between sessions and raters were also low for total scores on TCMS (1.66 and 2.35) and BESTest (2.99 and 2.32). However, on subscale- and item-level reliability decreased and ceiling effects were observed. No systematic bias was observed between sessions and raters. CONCLUSION: BESTest and TCMS showed to be reliable tools to measure balance in ASD on scale-level. However, on subscale- and item-level reliability decreased and ceiling effects were observed. Therefore, the question arises if there is need for an ASD-specific balance scale.

Performance on Balance Evaluation Systems Test (BESTest) Impacts Health-Related Quality of Life in Adult Spinal Deformity Patients.

STUDY DESIGN: Prospective single-center study. OBJECTIVE: Study investigates how dynamic balance performance complements 2D static radiographic measurements and demographics in terms of understanding health-related quality of life in adult spinal deformity (ASD) patients. SUMMARY OF BACKGROUND DATA: Recent insights suggest that demographic variables have a stronger impact on health-related quality of life than 2D radiographic spinopelvic parameters in ASD patients. METHODS: Nine healthy volunteers and 36 ASD patients following inclusion criteria were recruited. Demographics, Scoliosis Research Society Score-22r (SRS-22r), Oswestry Disability Index (ODI), Core Outcome Measures Index (COMI), 2D radiographic spinopelvic measurements, and performance on Balance Evaluation Systems Test (BESTest), and Trunk Control Measurement Scale (TCMS) were determined for each subject. Nonparametric tests, Spearman correlations, univariate, and stepwise-like linear multivariate regression analysis were performed. RESULTS: BESTest and TCMS had significant lower values in the ASD group versus the control group (P = 0.000). In the ASD group, Cumulative Illness Rating Scale (CIRS) correlated fair to ODI, COMI (0.441 ≥ r ≥ 0.383, P < 0.021) and to SRS-22-r (r = -0.335, P = 0.046), Mini Mental State Examination correlated fair to COMI (r = -0.352, P = 0.035), "Pelvic Incidence minus Lumbar Lordosis" correlated fair to ODI (r = 0.361, P = 0.031), BESTest correlated moderate to ODI and COMI (r ≤ -0.505; P ≤ 0.002), TCMS correlated fair to ODI (r = -0.356; P = 0.033). CIRS and BESTest were significant predictive variables for COMI based on univariate analysis in ASD patients. Multivariate regression analysis including demographics, 2D static radiographic parameters, and dynamic balance scales identified BESTest as single independent variable (P = 0.000) to predict COMI (adjusted R = 0.285) in ASD patients. CONCLUSION: BESTest has a higher potential than demographic and 2D radiographic spinopelvic parameters to predict quality of life in ASD patients. Further research is necessary to identify the impact of ASD on quality of life. LEVEL OF EVIDENCE: 3.

High-demand motor tasks are more sensitive to detect persisting alterations in muscle activation following total knee replacement.

Knee osteoarthritis is one of the most frequent indications for total knee replacement (TKR). Unfortunately, many patients still have difficulties during daily life activities after TKR. As the underlying causes of these difficulties are still not fully understood, especially with regard to the role of aberrant muscle activation profiles, the purpose of this study was to examine to what extent muscle activation patterns return to normal after TKR. Furthermore, we aimed to further discuss remaining differences by linking them to pre- and post-operative measurements of the knee and hip kinetics and kinematics during multiple functional motor tasks. Therefore, muscle activity, kinetics and kinematics of knee and hip were measured and analyzed in seven patients during a number of functional tasks by using electromyography and three-dimensional motion analysis. Measurements were performed one week before and one year after surgery. Results were compared to seven matched healthy controls. The analyzed functional tasks included walking at self-selected speed, walking followed by a crossover and a sidestep turn, step descent and ascent. This study suggested that, while muscle activation profiles in patients one year after TKR did return to normal during walking, this was not the case during more demanding motor tasks. These findings may have direct implications for the design of future rehabilitation programs in order to result in faster recovery and ultimately more functional patients after TKR.