Sex-dependent evolution of whole-body postural alignment with age.

PURPOSE: The goal of this study was to explore sex-related variations of global alignment parameters and their distinct evolution patterns across age groups. METHODS: This multicentric retrospective study included healthy volunteers with full-body biplanar radiographs in free-standing position. All radiographic data were collected from 3D reconstructions: global and lower limb parameters, pelvic incidence (PI) and sacral slope (SS). Lumbar lordosis (LL), thoracic kyphosis (TK) and cervical lordosis (CL) were also assessed as well as the lumbar and thoracic apex, and thoracolumbar inflexion point. The population was divided into five 5 age groups: Children, Adolescents, Young, Middle-Aged and Seniors. RESULTS: This study included 861 subjects (53% females) with a mean age of 34 ± 17 years. Mean PI was 49.6 ± 11.1 and mean LL was - 57.1 ± 11.6°. Females demonstrated a PI increase between Young and Middle-Aged groups (49 ± 11° vs. 55 ± 12°, p < 0.001) while it remained stable in males. SS and LL increased with age in females while remaining constant in males between Children and Middle-aged and then significantly decreased for both sexes between Middle-Aged and Seniors. On average, lumbar apex, inflexion point, and thoracic apex were located one vertebra higher in females (p < 0.001). After skeletal maturity, males had greater TK than females (64 ± 11° vs. 60 ± 12°, p = 0.04), with significantly larger CL (-13 ± 10° vs. -8 ± 10°, p = 0.03). All global spinal parameters indicated more anterior alignment in males. CONCLUSION: Males present more anteriorly tilted spine with age mainly explained by a PI increase in females between Young and Middle-Aged, which may be attributed to childbirth. Consequently, SS and LL increased before decreasing at senior age.

Assessment of malalignment at early stage in adolescent idiopathic scoliosis: a longitudinal cohort study.

INTRODUCTION: Our objective was to assess abnormalities of the odontoid-hip axis (OD-HA) angle in a mild scoliotic population to determine whether screening for malalignment would help predict the distinction between progressive and stable adolescent idiopathic scoliosis (AIS) at early stage. MATERIALS AND METHODS: All patients (non-scoliotic and AIS) underwent a biplanar X-ray between 2013 and 2020. In AIS, inclusion criteria were Cobb angle between 10° and 25°; Risser sign lower than 3; age higher than 10 years; and no previous treatment. A 3D spine reconstruction was performed, and the OD-HA was computed automatically. A reference corridor for OD-HA values in non-scoliotic subjects was calculated as the range [5th-95th percentiles]. A severity index, helping to distinguish stable and progressive AIS, was calculated and weighted according to the OD-HA value. RESULTS: Eighty-three non-scoliotic and 205 AIS were included. The mean coronal and sagittal OD-HA angles in the non-scoliotic group were 0.2° and -2.5°, whereas in AIS values were 0.3° and -0.8°, respectively. For coronal and sagittal OD-HA, 27.5% and 26.8% of AIS were outside the reference corridor compared with 10.8% in non-scoliotic (OR = 3.1 and 3). Adding to the severity index a weighting factor based on coronal OD-HA, for thoracic scoliosis, improved the positive predictive value by 9% and the specificity by 13%. CONCLUSION: Analysis of OD-HA suggests that AIS patients are almost three times more likely to have malalignment compared with a non-scoliotic population. Furthermore, analysis of coronal OD-HA is promising to help the clinician distinguish between stable and progressive thoracic scoliosis.

Towards a better understanding of knee angular deformities: discrepancies between clinical examination and 2D/3D assessments.

INTRODUCTION: Discrepancy between the clinical examination and the 2D/3D radiographs is a common concern in patients with angular or rotational deformities of the lower limbs, as it may alter clinical judgment and subsequent treatment. The aim was to identify such discrepancies and assess determinants that may contribute to their existence. MATERIALS AND METHODS: A retrospective chart review was conducted on 329 consecutive patients (658 lower limbs) who underwent physical examination and long-leg biplanar radiographs in our institution between 2013 and 2018 for limb length discrepancy or angular deformity of the knees (varus/valgus). Eleven parameters were measured on 2D and 3D images. 3D measurements were based on standing biplanar X-rays and their 3D reconstructions and were considered the gold standard. Contingency tables and multiple linear regression were used to assess discrepancies between the three modalities and their determinants respectively. RESULTS: Significant mismatches were found between physical examination and 2D images (1% in varus and 1% in valgus), between physical examination and 3D assessment (1% in varus and 4.6% in valgus) as well as between 2 and 3D assessments (1.9% in varus and 7.6% in valgus). The significant determinants of the mismatch between 2 and 3D modalities were frontal pelvic obliquity, neck shaft angle, knee flexion, femoral torsion, and tibial mechanical angle. CONCLUSION: In the presence of positional and/or morphological deformities, physical examination and 2D assessment of knee alignment could be biased due to axes projection errors. A better understanding of 3D alignment of the knee as part of the entire lower limb from pelvis to toes, may lead to a better diagnosis and subsequently a better treatment of knee angular deformities.

Femoral neck version in the spinopelvic and lower limb 3D alignment: a full-body EOS® study in 400 healthy subjects.

BACKGROUND: The goal of this study was to better understand the variation of femoral neck version according to spinopelvic and lower limb 3D alignment using biplanar X-rays in standing position. METHODS: This multicentric study retrospectively included healthy subjects from previous studies who had free-standing position biplanar radiographs. Subjects were excluded if they presented spinal or any musculo-skeletal deformity, and reported pain in the spine, hip or knee. Age, sex, and the following 3D-reconstructed parameters were collected: spinal curvatures, pelvic parameters, sagittal vertical axis (SVA), T1 pelvic angle (TPA), spino-sacral angle (SSA), femoral torsion angle (FTA), sacro-femoral angle (SFA), knee flexion angle (KA), ankle angle (AA), pelvic shift (PS) and ankle distance. Femoral neck version angle (FVA) was calculated between horizontal plane projection of the bi-coxo-femoral axis and the line passing through the femoral neck barycenter and femoral head center. Analysis according to age subsets was performed. RESULTS: A total of 400 subjects were included (219 females); mean age was 29 ± 18 years (range: 4-83). Subjects with high pelvic tilt values presented significantly higher FVA than average and low-PT individuals, respectively, 7.8 ± 7.1°, 2 ± 9° and 2.1 ± 9.5° (p < 0.001). These subjects also presented lower lumbar lordosis values and higher acetabulum anteversion in the horizontal plane than the two other groups. SVA correlation with FVA was weaker (r = 0.1, p = 0.03) than SSA and TPA (r = - 0.3 and r = 0.3, respectively, p < 0.001). A strong correlation was found with femoral torsion (r = 0.5, p < 0.001). SFA (r = - 0.3, p < 0.001), pelvic shift (r = 0.2, p < 0.001) and ankle distance (r = 0.3, p < 0.001) were also significantly correlated. Multivariate analysis confirmed significant association of age, pelvic tilt, lumbar lordosis, pelvic shift, ankle distance and femoral torsion with FVA. CONCLUSION: Patients with lower lumbar lordosis present pelvic retroversion which induces a higher femoral neck version. This finding may help positioning implants in total hip replacement procedures. Higher pelvic shift, age, male gender and increased femoral torsion were also correlated with higher FVA. LEVEL OF EVIDENCE: II (Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding).

Kyphectomy in myelomeningocele revisited: risk factors for failure.

PURPOSE: Lumbar kyphosis occurs in approximately 8-20% of patients with myelomeningocele (MMC). The purpose of this article is to analyze the risks and benefits of vertebrectomy and spinal stabilization in MMC children with severe lumbar kyphosis and to establish treatment guidelines. METHODS: This is an IRB-approved retrospective analysis of 59 patients with MMC who underwent kyphectomy and posterior instrumentation in three centers. Average age at surgery was 7.9 years (2 weeks-17 years). Sitting trunk position, skin status, kyphosis angle, and thoracic lordosis were analyzed preoperatively, postoperatively, and at an average follow-up of 8.2 years (range 2.5-16). The correction was maintained by applying a short posterior instrumentation in 6 patients, and extending to the pelvis in 53 cases. Pelvic fixation was achieved using the Warner and Fackler technique in 24 patients, the Dunn-McCarthy in 8, Luque-Galveston in 8, sacral screws in 2, and ilio-sacral screws in 11. RESULTS: Sitting position improved postoperatively in 47 of the 53 patients who underwent pelvic fixation and only in one patient with short instrumentation. All 6 patients with long instrumentation and poor postoperative sitting balance were in the Dunn-McCarthy fixation group. Skin sores at the apex of the deformity disappeared postoperatively in all patients but recurred in two patients with short instrumentations. Kyphosis angle improved from 109° (45°-170°) preoperatively to 10° (0°-45°) postoperatively and 21° (0°-55°) at last follow-up. The best results were seen in cases where a cross-k-wire fixation of the kyphectomy site was used, augmented with a long thoraco-pelvic instrumentation consisting of Luque sublaminar wires in the thoracic region and a Warner-Fackler type of pelvic fixation. Good results were also found with the bipolar technique and ilio-sacral screw fixation. Six over 24 patients with the Warner and Fackler technique showed gradual dislodgment or hardware failure, with subsequent nonunion of the kyphectomy site in four. Infection, with or without wound dehiscence and/or hardware exposure, occurred in 17 cases, necessitating hardware removal in 9 patients. CONCLUSION: Lumbar kyphosis in MMC children is best managed by resection of enough vertebrae from the apex to produce a flat lumbar spine, with perfect bone-to-bone contact and long thoraco-pelvic instrumentation using the Warner and Fackler technique through the S1 foramina or the bipolar technique with ilio-sacral screw fixation. Additional local fixation of the osteotomy site using cross-wires with or without cerclage increases the stability of the construct. The majority of complications occurred in patients with short instrumentations or where residual kyphosis persisted postoperatively regardless of the type of pelvic fixation or hardware density. The Dunn-McCarthy technique for pelvic fixation following kyphectomy in MMC was less successful in producing stable pelvic fixation and should not be considered in this patient category.

The rib cage: a new element in the spinopelvic chain.

INTRODUCTION: This study analyzes anatomical variations of the thoracic cage (TC) according to spinopelvic alignment, age and gender using stereoradiography in erect position. METHODS: This retrospective multicentric study analyzed computed parameters collected from free-standing position bi-planar radiographs, among healthy subjects. Collected data were: age, gender, pelvic parameters (Pelvic Incidence, Pelvic Tilt (PT) and Sacral Slope), T1-T12 Kyphosis (TK), L1-S1 Lordosis (LL), curvilinear spinal length, global TC parameters (maximum thickness and width, rib cage volume, mean Spinal Penetration Index (SPI)), 1st-10th rib parameters (absolute and relative (to the corresponding vertebra) sagittal angles). RESULTS: Totally, 256 subjects were included (140 females). Mean age was 34 (range: 8-83). Significant correlations were found between TK and TC thickness (0.3, p < 0.001) and with TC Volume (0.3, p = 0.04), as well as rib absolute sagittal angle for upper and middle ribs (0.2, p = 0.02). Conversely, a -0.3 correlation has been exhibited between SPI and TK. Similar correlations were found with LL. PT significantly correlated with TC thickness (0.4, p = 0.003), SPI (-0.3, p = 0.03), and all rib relative sagittal angles. Among global TC parameters, only thickness and SPI significantly changed after 20 years (respectively, 0.39 and -0.52, p < 0.001). Ribs relative sagittal angle showed negative correlation with age in skeletally mature subjects (p < 0.001). CONCLUSION: This study demonstrates the correlation between TC anatomy and spinopelvic parameters, confirming its part of the spinopelvic chain of balance. Indeed, higher spinal curvatures were associated with lower SPI and higher TC thickness, TC volume and rib absolute sagittal angles.

Assessment of dynamic balance during walking in patients with adult spinal deformity.

PURPOSE: To assess dynamic postural alignment in ASD during walking using a subject-specific 3D approach. METHODS: 69 ASD (51 ± 20 years, 77%F) and 62 controls (34 ± 13 years, 62%F) underwent gait analysis along with full-body biplanar Xrays and filled HRQoL questionnaires. Spinopelvic and postural parameters were computed from 3D skeletal reconstructions, including radiographic odontoid to hip axis angle (ODHA) that evaluates the head's position over the pelvis (rODHA), in addition to rSVA and rPT. The 3D bones were then registered on each gait frame to compute the dynamic ODHA (dODHA), dSVA, and dPT. Patients with high dODHA (> mean + 1SD in controls) were classified as ASD-DU (dynamically unbalanced), otherwise as ASD-DB (dynamically balanced). Between-group comparisons and relationship between parameters were investigated. RESULTS: 26 patients were classified as ASD-DU having an average dODHA of 10.4° (ASD-DB: 1.2°, controls: 1.7°), dSVA of 112 mm (ASD-DB: 57 mm, controls: 43 mm), and dPT of 21° (ASD-DB: 18°, controls: 14°; all p < 0.001). On static radiographs, ASD-DU group showed more severe sagittal malalignment than ASD-DB, with more altered HRQoL outcomes. The ASD-DU group had an overall abnormal walking compared to ASD-DB & controls (gait deviation index: 81 versus 93 & 97 resp., p < 0.001) showing a reduced flexion/extension range of motion at the hips and knees with a slower gait speed and shorter step length. Dynamic ODHA was correlated to HRQoL scores. CONCLUSION: Dynamically unbalanced ASD had postural malalignment that persist during walking, associated with kinematic alterations in the trunk, pelvis, and lower limbs, making them more prone to falls. Dynamic-ODHA correlates better with HRQoL outcomes than dSVA and dPT.

Global malalignment in adolescent idiopathic scoliosis: the axial deformity is the main driver.

PURPOSE: To evaluate the global alignment of non-operated subjects with adolescent idiopathic scoliosis. METHOD: A total of 254 subjects with AIS and 64 controls underwent low dose biplanar X-rays and had their spine, pelvis, and rib cage reconstructed in 3D. Global alignment was measured in the sagittal and frontal planes by calculating the OD-HA angle (between C2 dens to hip axis with the vertical). Subjects with AIS were classified as malaligned if the OD-HA was > 95th percentile relative to controls. RESULTS: The sagittal OD-HA in AIS remained within the normal ranges. In the frontal plane, 182 AIS were normally aligned (Group 1, OD-HA = 0.9°) but 72 were malaligned (Group 2, OD-HA = 2.9°). Group 2 had a more severe spinal deformity in the frontal and horizontal planes compared to Group 1 (Cobb: 42 ± 16° vs. 30 ± 18°; apical vertebral rotation AVR: 19 ± 10° vs. 12 ± 7°, all p < 0.05). Group 2 subjects were mainly classified as Lenke 5 or 6. 19/72 malaligned subjects had a mild deformity (Cobb < 30°) but a progressive scoliosis (severity index ≥ 0.6). The frontal OD-HA angle was found to be mainly determined (adjusted-R2 = 0.22) by the apical vertebral rotation and secondarily by the Lenke type. CONCLUSIONS: This study showed that frontal malalignment is more common in distal major structural scoliosis and its main driver is the apical vertebral rotation. This highlights the importance of monitoring the axial plane deformity in order to avoid worsening of the frontal global alignment.

Alterations of gait kinematics depend on the deformity type in the setting of adult spinal deformity.

PURPOSE: To evaluate 3D kinematic alterations during gait in Adult Spinal Deformity (ASD) subjects with different deformity presentations. METHODS: One hundred nineteen primary ASD (51 ± 19y, 90F), age and sex-matched to 60 controls, underwent 3D gait analysis with subsequent calculation of 3D lower limb, trunk and segmental spine kinematics as well as the gait deviation index (GDI). ASD were classified into three groups: 51 with sagittal malalignment (ASD-Sag: SVA > 50 mm, PT > 25°, and/or PI-LL > 10°), 28 with only frontal deformity (ASD-Front: Cobb > 20°) and 40 with only hyperkyphosis (ASD-HyperTK: TK > 60°). Kinematics were compared between groups. RESULTS: ASD-Sag had a decreased pelvic mobility compared to controls with a decreased ROM of hips (38 vs. 45°) and knees (51 vs. 61°). Furthermore, ASD-Sag exhibited a decreased walking speed (0.8 vs. 1.2 m/s) and GDI (80 vs. 95, all p < 0.05) making them more prone to falls. ASD-HyperTK showed similar patterns but in a less pronounced way. ASD-Front had normal walking patterns. GDI, knee flex/extension and walking speed were significantly associated with SVA and PT (r = 0.30-0.65). CONCLUSION: Sagittal spinal malalignment seems to be the driver of gait alterations in ASD. Patients with higher GT, SVA, PT or PI-LL tended to walk slower, with shorter steps in order to maintain stability with a limited flexibility in the pelvis, hips and knees. These changes were found to a lesser extent in ASD with only hyperkyphosis but not in those with only frontal deformity. 3D gait analysis is an objective tool to evaluate functionality in ASD patients depending on their type of spinal deformity. LEVEL OF EVIDENCE I: Diagnostic: individual cross-sectional studies with consistently applied reference standard and blinding.

Effect of curve location on the severity index for adolescent idiopathic scoliosis: a longitudinal cohort study.

OBJECTIVES: Adolescent idiopathic scoliosis (AIS) is the most common spinal disorder in children. A severity index was recently proposed to identify the stable from the progressive scoliosis at the first standardized biplanar radiographic exam. The aim of this work was to extend the validation of the severity index and to determine if curve location influences its predictive capabilities. METHODS: AIS patients with Cobb angle between 10° and 25°, Risser 0-2, and no previous treatment were included. They underwent standing biplanar radiography and 3D reconstruction of the spine and pelvis, which allowed to calculate their severity index. Patients were grouped by curve location (thoracic, thoracolumbar, lumbar). Patients were followed up until skeletal maturity (Risser ≥ 3) or brace prescription. Their outcome was compared to the prediction made by the severity index. RESULTS: In total, 205 AIS patients were included; 82% of them (155/189, 95% confidence interval [74-90%]) were correctly classified by the index, while 16 patients were unclassified. Positive predictive ratio was 78% and negative predictive ratio was 86%. Specificity (78%) was not significantly affected by curve location, while patients with thoracic and lumbar curves showed higher sensitivity (≥ 89%) than those with thoracolumbar curves (74%). CONCLUSIONS: In this multicentric cohort of 205 patients, the severity index was used to predict the risk of progression from mild to moderate scoliosis, with similar results of typical major curve types. This index represents a novel tool to aid the clinician and the patient in the modulation of the follow-up and, for progressive patients, their decision for brace treatment. KEY POINTS: • The severity index of adolescent idiopathic scoliosis has the potential to detect patients with progressive scoliosis as early as the first exam. • Out of 205 patients, 82% were correctly classified as either stable or progressive by the severity index. • The location of the main curve had small effect on the predictive capability of the index.

Toward understanding the underlying mechanisms of pelvic tilt reserve in adult spinal deformity: the role of the 3D hip orientation.

PURPOSE: To explore 3D hip orientation in standing position in subjects with adult spinal deformity (ASD) presenting with different levels of compensatory mechanisms. METHODS: Subjects with ASD (n = 159) and controls (n = 68) underwent full-body biplanar X-rays with the calculation of 3D spinopelvic, postural and hip parameters. ASD subjects were grouped as ASD with knee flexion (ASD-KF) if they compensated by flexing their knees (knee flexion ≥ 5°), and ASD with knee extension (ASD-KE) otherwise (knee flexion < 5°). Spinopelvic, postural and hip parameters were compared between the three groups. Univariate and multivariate analyses were then computed between spinopelvic and hip parameters. RESULTS: ASD-KF had higher SVA (67 ± 66 mm vs. 2 ± 33 mm and 11 ± 21 mm), PT (27 ± 14° vs. 18 ± 9° and 11 ± 7°) and PI-LL mismatch (20 ± 26° vs - 1 ± 18° and - 13 ± 10°) when compared to ASD-KE and controls (all p < 0.05). ASD-KF also had a more tilted (34 ± 11° vs. 28 ± 9° and 26 ± 7°), anteverted (24 ± 6° vs. 20 ± 5° and 18 ± 4°) and abducted (59 ± 6° vs. 57 ± 4° and 56 ± 4°) acetabulum, with a higher posterior coverage (100 ± 6° vs. 97 ± 7° for ASD-KE) when compared to ASD-KE and controls (all p < 0.05). The main determinants of acetabular tilt, acetabular abduction and anterior acetabular coverage were PT, SVA and LL (adjusted R2 [0.12; 0.5]). CONCLUSIONS: ASD subjects compensating with knee flexion have altered hip orientation, characterized by increased posterior coverage (acetabular anteversion, tilt and posterior coverage) and decreased anterior coverage which can together lead to posterior femoro-acetabular impingement, thus limiting pelvic retroversion. This underlying mechanism could be potentially involved in the hip-spine syndrome.

Spine slenderness and wedging in adolescent idiopathic scoliosis and in asymptomatic population: an observational retrospective study.

PURPOSE: The origin of the deformity due to adolescent idiopathic scoliosis (AIS) is not known, but mechanical instability of the spine could be involved in its progression. Spine slenderness (the ratio of vertebral height to transversal size) could facilitate this instability, thus playing a role in scoliosis progression. The purpose of this work was to investigate slenderness and wedging of vertebrae and intervertebral discs in AIS patients, relative to their curve topology and to the morphology of control subjects. METHODS: A total of 321 AIS patients (272 girls, 14 ± 2 years old, median Risser sign 3, Cobb angle 35° ± 18°) and 83 controls were retrospectively included (56 girls, median Risser 2, 14 ± 3 years). Standing biplanar radiography and 3D reconstruction of the spine were performed. Geometrical features were computed: spinal length, vertebral and disc sizes, slenderness ratio, frontal and sagittal wedging angles. Measurement reproducibility was evaluated. RESULTS: AIS girls before 11 years of age had slightly longer spines than controls (p = 0.04, Mann-Whitney test). AIS vertebrae were significantly more slender than controls at almost all levels, almost independently of topology. Frontal wedging of apical vertebrae was higher in AIS, as expected, but also lower junctional discs showed higher wedging than controls. CONCLUSION: AIS patients showed more slender spines than the asymptomatic population. Analysis of wedging suggests that lower junctional discs and apex vertebra could be locations of mechanical instability. Numerical simulation and longitudinal clinical follow-up of patients could clarify the impact of wedging, slenderness and growth on the biomechanics of scoliosis progression. These slides can be retrieved under Electronic Supplementary Material.

Alterations of 3D acetabular and lower limb parameters in adolescent idiopathic scoliosis.

PURPOSE: To evaluate the 3D deformity of the acetabula and lower limbs in subjects with adolescent idiopathic scoliosis (AIS) and their relationship with spino-pelvic alignment. METHODS: Two hundred and seventy-four subjects with AIS (frontal Cobb: 33.5° ± 18° [10°-110°]) and 84 controls were enrolled. All subjects underwent full-body biplanar X-rays with subsequent 3D reconstructions. Classic spino-pelvic and lower limb parameters were collected as well as acetabular parameters: acetabular orientation in the 3 planes (tilt, anteversion and abduction), center-edge angle (CEA) and anterior and posterior sector angles. Subjects with AIS were represented by both lower limb sides and classified by elevated (ES) or lowered (LS), depending on the frontal pelvic obliquity. Parameters were then compared between groups. Determinants of acetabular and lower limb alterations were investigated among spino-pelvic parameters. RESULTS: Acetabular abduction was higher on the ES in AIS (59.2° ± 6°) when compared to both LS (55.6° ± 6°) and controls (57.5° ± 3.9°, p < 0.001). CEA and acetabular anteversion were higher on the LS in AIS (32° ± 6.1°, 20.5° ± 5.7°) when compared to both ES (28.7° ± 5.1°, 19.8° ± 5.1°) and controls (29.8° ± 4.8°, 19.1° ± 4°, respectively, p < 0.001). Anterior sector angle was lower on both ES and LS in AIS when compared to controls. CEA, acetabular abduction and acetabular anteversion were found to be mostly determined (adjusted R2: 0.08-0.32) by pelvic tilt and less by frontal pelvic obliquity, frontal Cobb and T1T12. CONCLUSIONS: Subjects with AIS had a more abducted acetabulum at the lowered side, more anteverted acetabulum and a lack of anterior coverage of both acetabula. These alterations were strongly related to pelvic tilt.

Quasi-automatic early detection of progressive idiopathic scoliosis from biplanar radiography: a preliminary validation.

PURPOSE: To validate the predictive power and reliability of a novel quasi-automatic method to calculate the severity index of adolescent idiopathic scoliosis (AIS). METHODS: Fifty-five AIS patients were prospectively included (age 10-15, Cobb 16° ± 4°). Patients underwent low-dose biplanar X-rays, and a novel fast method for 3D reconstruction of the spine was performed. They were followed until skeletal maturity (stable patients) or brace prescription (progressive patients). The severity index was calculated at the first examination, based on 3D parameters of the scoliotic curve, and it was compared with the patient's final outcome (progressive or stable). Three operators have repeated the 3D reconstruction twice for a subset of 30 patients to assess reproducibility (through Cohen's kappa and intra-class correlation coefficient). RESULTS: Eighty-five percentage of the patients were correctly classified as stable or progressive by the severity index, with a sensitivity of 92% and specificity of 74%. Substantial intra-operator agreement and good inter-operator agreement were observed, with 80% of the progressive patients correctly detected at the first examination. The novel severity index assessment took less than 4 min of operator time. CONCLUSIONS: The fast and semiautomatic method for 3D reconstruction developed in this work allowed for a fast and reliable calculation of the severity index. The method is fast and user friendly. Once extensively validated, this severity index could allow very early initiation of conservative treatment for progressive patients, thus increasing treatment efficacy and therefore reducing the need for corrective surgery. These slides can be retrieved under Electronic Supplementary Material.

Are changes in radiological leg alignment and femoral parameters after total hip replacement responsible for joint loading during gait?

BACKGROUND: Gait kinematics after total hip replacement only partly explain the differences in the joint moments in the frontal plane between hip osteoarthritis patients after hip replacement and healthy controls. The goal of this study was to determine if total hip replacement surgery affects radiological leg alignment (Hip-Knee-Shaft-Angle, femoral offset, Neck-Shaft-Angle and varus/valgus alignment) and which of these parameters can explain the joint moments, additionally to the gait kinematics. METHODS: 22 unilateral hip osteoarthritis patients who were scheduled for total hip replacement were included in the study. Preoperatively and 1 year postoperatively all patients had biplanar radiographic examinations and 3D gait analysis. RESULTS: The operated leg showed significantly (P < 0.05) more varus (1.1°) as well as a larger femoral offset (+ 8 mm) and a larger Hip-Knee-Shaft-Angle (+ 1.3°) after total hip replacement; however no significant differences in the joint moments in the frontal plane compared to healthy controls were found. The hip moment (first half of stance) and the knee moments (first and second half of stance) were mostly determined by the varus/valgus alignment (29% and respectively 36% and 35%). The combination with a kinematic parameter (knee range of motion, foot progression angle) increased the predictive value for the knee moments. CONCLUSION: In our patient group the joint moments after total hip replacement did not differ from healthy controls, whereas radiological leg alignment parameters changed significantly after the total hip replacement. A combination of these radiological leg parameters, especially the varus alignment, and the deviating kinematics explain the joint moments in the frontal plane during gait after total hip replacement surgery. For surgeons it is important not to create too much of a structural varus alignment by implanting the new hip joint as varus alignment can increase the knee adduction moment and the risk for osteoarthritis of the medial knee compartment. TRIAL REGISTRATION: This study was retrospectively registered with DRKS (German Clinical Trials Register) under the number DRKS00015053. Registered 1st of August 2018.

Cervical and postural strategies for maintaining horizontal gaze in asymptomatic adults.

PURPOSE: To investigate the different cervical strategies for maintaining horizontal gaze in asymptomatic subjects. METHODS: One hundred and forty-four asymptomatic adults filled the SF-36 quality of life questionnaire and underwent full-body biplanar radiographs. Chin brow vertical angle (CBVA) and postural and cervical parameters were measured. Subjects were grouped according to cervical spine curvature (C2-C7 angle): kyphotic (< - 5°), straight [- 5°, 5°], lordotic (> 5°). Demographics, SF-36 component scores and CBVA were compared between groups. All other parameters were compared between groups, while controlling for confounding factors (ANCOVA). A correlation test was conducted between all cervical parameters. RESULTS: 32% of subjects had kyphotic (- 12° ± 7°), 27% straight (0° ± 3°) and 41% lordotic (12° ± 7°) cervical spines. While demographic and SF-36 data did not differ between groups, CBVA differed between lordotic and kyphotic groups (2° vs. 6.5°, p = 0.002). Sagittal vertical axis (SVA) and thoracic kyphosis (TK) were lower in the kyphotic group (SVA: K = - 26 ± 20 mm vs. L = - 2 ± 21 mm, p < 0.001; TK: K = 40° ± 6° vs. L = 51° ± 8°, p < 0.001). C2 slope (K = 29° ± 6° vs. L = 18° ± 6°, p < 0.001), C0-C2 (K = 42° ± 8° vs. L = 30° ± 8°, p < 0.001) and C1-C2 (K = 33° ± 6° vs. L = 28° ± 6°, p = 0.004) were higher in the kyphotic group. Significant correlations were found between almost all cervical parameters and C2-C7 angle. CONCLUSIONS: Subjects with cervical kyphosis presented with more posterior global alignment and lower TK than subjects with lordosis. In order to maintain horizontal gaze, subjects with cervical kyphosis presented with a more lordotic upper cervical spine than subjects with cervical lordosis. Subjects with straight cervical curvature presented with an intermediate sagittal alignment. These slides can be retrieved under Electronic Supplementary Material.

Influence of patient axial malpositioning on the trueness and precision of pelvic parameters obtained from 3D reconstructions based on biplanar radiographs.

OBJECTIVES: Radiographs are often performed to assess pelvic and hip parameters, but results depend upon correct pelvis positioning. Three-dimensional (3D) reconstruction from biplanar-radiographs should provide parameters that are less sensitive to pelvic orientation, but this remained to be evaluated. METHODS: Computerized-tomographic scans of six patients were used both as a reference and for generating simulated frontal and lateral radiographs. These simulated radiographs were generated while introducing axial rotations of the pelvis ranging from 0° to 20°. Simulated biplanar-radiographs were utilized by four operators, three times each, to perform pelvic 3D-reconstructions. These reconstructions were used to assess the trueness, precision and global uncertainty of radiological pelvic and hip parameters for each position. RESULTS: In the neutral position, global uncertainty ranged between ± 2° for pelvic tilt and ± 9° for acetabular posterior sector angle and was mainly related to precision errors (ranging from 1.5° to 7°). With increasing axial rotation, global uncertainty increased and ranged between ± 5° for pelvic tilt and ± 11° for pelvic incidence, sacral slope and acetabular anterior sector angle, mainly due to precision errors. CONCLUSION: Radiological parameters obtained from 3D-reconstructions, based on biplanar-radiographs, are less sensitive to axial rotation compared to plain radiographs. However, the axial rotation should nonetheless not exceed 10°. KEY POINTS: • Pelvic radiological parameters could be affected by patient malpositioning. • Biplanar radiograph-based 3D reconstructions were performed at increments of axial rotation. • Trueness, precision and global uncertainty were evaluated for pelvic and hip radiological parameters. • Hip parameters were less affected by rotation compared to pelvic parameters. • Maintaining the pelvis close to the neutral position is recommended to ensure the highest possible accuracy.

A NEW APPROACH IN THE CLINICAL DECISION-MAKING FOR CEREBRAL PALSY USING THREE-DIMENSIONAL SUBJECT-SPECIFIC MUSCULOSKELETAL RECONSTRUCTIONS.

Cerebral palsy (CP) is a neurological disorder which can cause muscular spasticity. Children with this condition suffer from a combination of gait deviations, skeletal deformities and muscular abnormalities. Precise evaluation of each of these three components is crucial for management planning in children with CP. The aim of this study is to review the latest innovative methods used for three-dimensional (3D) gait analysis and musculoskeletal modeling in children with cerebral palsy. 3D gait analysis is a quantitative objective method based on the use of infrared cameras. It allows the evaluation of dynamic joint angles, forces and moments applied on joints and is usually coupled with dynamic electromyography. Skeletal evaluation is usually based on two-dimensional X-rays and physical examination in clinical practice. However, a novel method based on stereoradiographic 3D reconstruction of biplanar low dose X-rays allows a more thorough evaluation of skeletal deformities, and in particular torsional anomalies. Muscular evaluation of children with CP is most commonly based on magnetic resonance imaging, whereby delimitation of lower limb muscles on axial slices allows 3D reconstruction of these muscles. Novel innovative techniques allow similar reconstructions by extrapolation, thus limiting the necessary quantity of axial slices that need to be manually delimitated.

Kinematic evaluation of 4 pediatric collars and distribution of cervical movement between primary and coupled angles.

BACKGROUND: Primary and coupled angle restrictions, when neck collars are used, have been investigated mainly in adults and not yet in children. PURPOSE: To evaluate the efficiency of 4 pediatric collars in reducing cervical range of motion (ROM) in primary and coupled planes. METHODS: Thirty asymptomatic children (16 boys and 14 girls) aged 6 to 12 years participated in the study. A motion analysis system was used to evaluate the ROM of the cervical spine during flexion/extension, left and right lateral bending, and left and right axial rotation. Primary and coupled ROM were evaluated in unbraced and braced conditions. Four cervical collars were tested: Philadelphia, Miami Jr, Necloc, and the conventional Hard Collar. Thirteen subjects were tested 2 times to evaluate the repeatability of the parameters. The ROM in each plane was normalized to the sum of the ROM in the 3 planes, for each movement, to estimate the percentage of the movement in each plane (normalized ROM), in braced and unbraced conditions. The analysis of variance and post hoc Benferroni tests were applied on raw and normalized ROM. RESULTS: ROM collected in collars showed a significant difference compared with the unbraced condition. ROM obtained in Necloc and Miami Jr showed a significant difference compared with Philadelphia and conventional Hard Collar. The primary plane is activated at 80% during flexion-extension and left-right axial rotation; however, 55% of the total movement was completed in the frontal plane during left-right lateral bending in unbraced condition. Statistical differences in the normalized ROM were found between the braced and unbraced conditions and among collars. CONCLUSIONS: Necloc and Miami Jr presented the highest limitation of movement in the primary and secondary planes. The distribution strategy of a movement, between primary and coupled angles, is different between the braced and unbraced conditions.