Gender difference of shoulder-pelvic kinematic integration for trunk rotation directions in healthy older adults

BackgroundThe trunk coordination pattern has been extensively studied, and there is a higher pain prevalence and asymmetry in female older adults. However, there is a lack of investigation of different directions of trunk rotation and asymmetrical compensatory strategies of motor control between genders. The purpose of this study was to investigate shoulder and pelvic ranges of motion (ROM) as well as relative phases (RP) for the different directions of trunk rotation between genders in healthy older adults.MethodsThere were 62 right hand dominant older adults in this study (31 female subjects (68.4 [5.62] years) and 31 male subjects (68.7 [5.68] years)). The participants performed trunk axial rotation from the left to the right direction (RP1) and then returned to the left side (RP2), three times repeatedly in standing. The measurements included shoulder and pelvic ROM, RP1, and RP2. The RP was defined as the average absolute relative phase, which was the difference between the phase angle of the shoulder and the phase angle of the pelvis during trunk rotation.FindingsThe female group demonstrated significantly greater pelvic rotation compared to the male group (98.64 [24.67] vs. 86.96 [18.97]; t = 2.09, p = 0.04) during trunk rotation. The pelvic ROM demonstrated a significant positive correlation with shoulder ROM in both genders; however, the RP was negatively correlated with the pelvis. For pelvic rotation, the male group demonstrated a negative correlation with RP1 (r = − 0.68, p < 0.01) and RP2 (r = − 0.60, p < 0.01) while the female group demonstrated a negative correlation with RP2 (r = − 0.53, p < 0.01). The ageing factor demonstrated negative correlations with ROM for the shoulder and pelvis in both genders.InterpretationAlthough no gender difference was indicated on the direction of RP, the pelvic ROM was significantly lesser in the male group. The male group demonstrated lesser pelvic rotation in both directions of rotation; however, the female group showed lesser pelvic rotation in RP2. The male group demonstrated stiffened pelvic rotation and greater shoulder rotation in both directions while the female group demonstrated pelvic stiffness only in the direction from right to left rotation. Clinicians need to consider this directional asymmetry of trunk rotation to enhance integrated shoulder-pelvic coordination in female older adults.Mini abstractA coordinative pattern of different directions of trunk rotation was investigated in healthy older adults. The pelvic range of motion was lesser in the male group compared with the female group. The female group demonstrated pelvic stiffness only in the direction from right to left rotation, while the male group demonstrated pelvic stiffness in both directions. Clinicians need to understand the gender difference of directional coordination as integrated coordination in female older adults.     

The Functional Reach Test: Strategies,performance and the influence of age

BackgroundThe Functional Reach Test (FRT) is a clinical assessment of the risk of falls in elderly or disabled subjects. However, the FRT is complex (involving the leg, hip and trunk joints) and previous studies have shown that several different strategies can be used to complete the test.ObjectivesTo describe the strategies used by healthy, adult subjects when performing the FRT and to assess the influence of age on choice of the strategy.MethodThis was a pilot study in which 29 non-fallers (18 under-50s and 11 over-75s) were asked to perform the FRT on a force platform in a motion analysis laboratory. A total of 18 reflective markers were placed on the body. The main outcome measures were the FRT score, the centre of pressure (CoP) excursion, and kinetic and kinematic test data. The two age groups were compared using a non-parametric, two-sample Mann-Whitney U test. A cluster analysis of the entire population grouped subjects together according to their functional similarities.ResultsThe older subjects displayed a smaller CoP anteroposterior displacement (P < 0.01), greater backwards displacement of the pelvis (P < 0.05) and less trunk rotation during the FRT (P = 0.024) than the younger subjects. The cluster analysis split the population into two groups, which differed in terms of age, FRT score, pelvis translation, and CoP displacement.ConclusionOur results suggest that at the moment of trunk flexion, elderly subjects use pelvic translation in order to limit forward displacement of the CoP and prevent forward imbalance.     

Differences in lumbar spine and lower extremity kinematics during a step down functional task in people with and people without low back pain

BackgroundWhen functional movements are impaired in people with low back pain, they may be a contributing factor to chronicity and recurrence. The purpose of the current study was to examine lumbar spine, pelvis, and lower extremity kinematics during a step down functional task between people with and without a history of low back pain.MethodsA 3-dimensional motion capture system was used to analyze kinematics during a step down task. Total excursion of the lumbar spine, pelvis, and lower extremity segments in each plane were calculated from the start to end of the task. Separate analysis of variance tests (α = 0.05) were conducted to determine the effect of independent variables of group and plane on lumbar spine, pelvis, and lower extremity kinematics. An exploratory analysis was conducted to examine kinematic differences among movement-based low back pain subgroups.FindingsSubjects with low back pain displayed less lumbar spine movement than controls across all three planes of movement (P-values = 0.001–0.043). This group difference was most pronounced in the sagittal plane. For the lower extremity, subjects with low back pain displayed more frontal and axial plane knee movement than controls (P-values = 0.001). There were no significant differences in kinematics among movement-based low back pain subgroups.InterpretationPeople with low back pain displayed less lumbar region movement in the sagittal plane and more off-plane knee movements than the control group during a step down task. Clinicians can use this information when assessing lumbar spine and lower extremity movement during functional tasks, with the goal of developing movement-based interventions.     

Trunk kinetic effort during step ascent and descent in patients with transtibial amputation using angular momentum separation

BackgroundPatients with transtibial amputation adopt trunk movement compensations that alter effort and increase the risk of developing low back pain. However, the effort required to achieve high-demand tasks, such as step ascent and descent, remains unknown.MethodsKinematics were collected during bilateral step ascent and descent tasks from two groups: 1) seven patients with unilateral transtibial amputation and 2) seven healthy control subjects. Trunk kinetic effort was quantified using translational and rotational segmental moments (time rate of change of segmental angular momentum). Peak moments during the loading period were compared across limbs and across groups.FindingsDuring step ascent, patients with transtibial amputation generated larger sagittal trunk translational moments when leading with the amputated limb compared to the intact limb (P = 0.01). The amputation group also generated larger trunk rotational moments in the frontal and transverse planes when leading with either limb compared to the healthy group (P = 0.01, P < 0.01, respectively). During step descent, the amputation group generated larger trunk translational and rotational moments in all three planes when leading with the intact limb compared to the healthy group (P < 0.017).InterpretationThis investigation identifies how differing trunk movement compensations, identified using the separation of angular momentum, require higher kinetic effort during stepping tasks in patients with transtibial amputation compared to healthy individuals. Compensations that produce identified increased and asymmetric trunk segmental moments, may increase the risk of the development of low back pain in patients with amputation.     

The effect of within-session instruction on lumbopelvic motion during a lower limb movement in people with and people without low back pain

The purpose of the current study was to examine how effectively people with and people without low back pain (LBP) modify lumbopelvic motion during a limb movement test. Nineteen subjects with LBP and 20 subjects without LBP participated. Kinematic data were collected while subjects performed active hip lateral rotation (HLR) in prone. Subjects completed trials (1) using their natural method (Natural condition) of performing HLR, and (2) following standardized instructions to modify lumbopelvic motion while performing HLR (Modified condition). Variables of interest included (1) the amount of HLR completed prior to the start of lumbopelvic motion, and (2) the maximum amount of lumbopelvic motion demonstrated during HLR. Compared to the Natural Condition, all subjects improved their performance during the Modified condition by (1) completing a greater amount of HLR prior to the start of lumbopelvic motion, and (2) demonstrating less lumbopelvic motion (P < 0.01 for all comparisons). There was a tendency for people without LBP to demonstrate a greater difference in maximal lumbopelvic rotation between the Natural and Modified conditions (P = 0.07). In conclusion, people are able to modify lumbopelvic motion following instruction. Further study is needed to determine if people without LBP improve lumbopelvic motion following instruction to a greater extent than people with LBP.     

Analysis of the upper cervical spine stiffness during axial rotation: A comparative study among patients with tension-type headache or migraine and asymptomatic subjects

BackgroundMany studies reported the implication of the cervical musculoskeletal system in patients with tension type headache and migraine. The objective of this study is to investigate the upper cervical spine stiffness features in axial rotation among headache patients in comparison with a healthy population.Methods48 subjects including 30 migraine patients with/without aura and 18 patients with tension-type headache, aged between 18 and 60 years (mean 36, SD 11 years) have been evaluated. Stiffness measurements were carried out for passive axial rotation using a torque meter device. The flexion-rotation test was used to emphasize assessment of the upper cervical spine.FindingsNeither the stiffness nor the neutral zone varies between different populations studied. Passive range of motion in axial rotation is unilaterally reduced in symptomatic subjects (p = 0.001). Considering the elastic zone, right and left motion magnitude was significantly lower for clinical groups compared to the control group.InterpretationStiffness seems not to be altered among tension type headache and migraine patients. However, patients seem prone to display a larger right-left asymmetry of axial rotation and a reduction in the motion range tolerance, emphasizing the likely link between the cervical discomfort and these pathologies. Any difference is observed in the elastic behavior of the upper cervical spine between the two primary headache populations. However, further investigations are needed to confirm these previous results taking various specific clinical characteristics into consideration.     

Hip kinematics and kinetics in persons with and without cam femoroacetabular impingement during a deep squat task

BackgroundPrevious studies have indicated that hip and pelvis kinematics may be altered during functional tasks in persons with femoroacetabular impingement. The purpose of this study was to compare hip and pelvis kinematics and kinetics during a deep squat task between persons with cam femoroacetabular impingement and pain-free controls.MethodsFifteen persons with cam femoroacetabular impingement and 15 persons without cam femoroacetabular impingement performed a deep squat task. Peak hip flexion, abduction, and internal rotation, and mean hip extensor, adductor, and external rotator moments were quantified. Independent t-tests (α < 0.05) were used to evaluate between group differences.FindingsCompared to the control group, persons with cam femoroacetabular impingement demonstrated decreased peak hip internal rotation (15.2° (SD 9.5°) vs. 9.4° (SD 7.8°); P = 0.041) and decreased mean hip extensor moments (0.56 (SD 0.12) Nm/kg vs. 0.45 (SD 0.15) Nm/kg; P = 0.018). In addition persons in the cam femoroacetabular impingement group demonstrated decreased posterior pelvis tilt during squat descent compared to the control group, resulting in a more anteriorly tilted pelvis at the time peak hip flexion (12.5° (SD 17.1°) vs. 23.0° (SD 12.4°); P = 0.024).InterpretationThe decreased hip internal rotation observed in persons with cam femoroacetabular impingement may be the result of bony impingement. Furthermore, the decrease in posterior pelvis tilt may contribute to impingement by further approximating the femoral head–neck junction with the acetabulum. Additionally, decreased hip extensor moments suggest that diminished hip extensor muscle activity may contribute to decreased posterior pelvis tilt.     

Effects of hip and trunk muscle strengthening on hip function and lower limb kinematics during step-down task

BackgroundStrengthening of the hip and trunk muscles has the potential to change lower limb kinematic patterns, such as excessive hip medial rotation and adduction during weight-bearing tasks. This study aimed to investigate the effect of hip and trunk muscles strengthening on hip muscle performance, hip passive properties, and lower limb kinematics during step-down task in women.MethodsThirty-four young women who demonstrated dynamic knee valgus during step-down were divided into two groups. The experimental group underwent three weekly sessions of strengthening exercises for eight weeks, and the control group continued their usual activities. The following evaluations were carried out: (a) isokinetic maximum concentric and eccentric work of hip lateral rotators, (b) isokinetic hip passive torque of lateral rotation and resting transverse plane position, and (c) three-dimensional kinematics of the lower limb during step-down.FindingsThe strengthening program increased concentric (P < 0.001) and eccentric (P < 0.001) work of hip lateral rotators, and changed hip resting position toward lateral rotation (P < 0.001). The intervention did not significantly change hip passive torque (P = 0.089, main effect). The program reduced hip (P = 0.002), thigh (P = 0.024) and shank (P = 0.005) adduction during step-down task. Hip, thigh and knee kinematics in transverse plane and foot kinematics in frontal plane did not significantly modify after intervention (P ≥ 0.069, main effect).InterpretationHip and trunk strengthening reduced lower limb adduction during step-down. The changes in hip maximum work and resting position may have contributed to the observed kinematic effects.     

Quantitative indices of dynamics in concentrations of lipopolysaccharide-binding protein (LBP) as prognostic factors in severe sepsis/septic shock patients--comparison with CRP and procalcitonin

ObjectivesTo devise and evaluate quantitative indices of dynamics in lipopolysaccharide-binding protein (LBP), CRP, and procalcitonin concentrations as prognostic markers in sepsis.Design and methodsProspective observational cross-sectional study with 5-day follow-up. Simple (Δ_5 ? 1) and relative (chain indices-based) rates for LBP (ELISA), procalcitonin (immunoluminometry), and CRP were devised.ResultsAdmission concentrations of all markers were higher in septic patients than controls. Not the admission levels but markers' time-courses differed between survivors (declining) and non-survivors (persistently high). Simple and relative rates were greater in survivors than non-survivors. Their accuracies as outcome predictors were comparable, higher for LBP and CRP than PCT. At ~ 95% sensitivity, the highest specificity had LBP relative and simple rates. Except for sepsis severity scores, only LBP was independently associated with lethal outcome.ConclusionsFor outcome prediction, the evaluation of dynamics of sepsis mediators, expressed by simple or relative rates, is a more suitable alternative to markers' peak values.     

Scapular-focused exercise treatment protocol for shoulder impingement symptoms: Three-dimensional scapular kinematics analysis

BackgroundThe present study aimed to describe the effects of a periscapular strengthening and neuromuscular training protocol in three-dimensional scapular kinematics and resting positioning in participants with shoulder impingement symptoms. Self-reported function was also evaluated.MethodThe study group comprised 50 subjects with shoulder impingement syndrome (control group, n = 25; treatment group, n = 25). The treatment group underwent 8 weeks of neuromuscular training and periscapular strengthening. Scapular kinematics was measured using an electromagnetic tracking device, and the Brazilian version of the Shoulder Pain and Disability Index (SPADI-Br) questionnaire was carried out before and after the treatment.FindingsIn the resting position, treated subjects had lower (p < 0.01) internal rotation of the scapula compared to the control group, with a large effect size (2.4). On the coronal plane, the treated group had less scapular upward rotation (p < 0.01) and less internal rotation (p < 0.05), with a medium effect size. On the sagittal plane, the treated group had less internal rotation (p < 0.01), less upward rotation (p < 0.05), and less scapular anterior tilt (p < 0.01), with a medium effect size. On the scapular plane, a reduction in upward rotation (p < 0.01) after the intervention was observed, with a large effect size. Moreover, a reduction in the total SPADI-Br score was found, with a mean difference of 32.4 [24.4; 40.4] points (p < 0.01) after the implementation of the protocol and a large effect size (2.0).InterpretationThe results provide biomechanical support for the clinical rationale for indicating therapeutic exercises focused on the periscapular muscles to improve scapular dynamics.     

Influence of reducing anterior pelvic tilt on shoulder posture and the electromyographic activity of scapular upward rotators

BackgroundModifications of posture in a segment may influence the posture of adjacent and nonadjacent segments and muscular activity. The spine–shoulder and spine–pelvis relationships suggest that the pelvis may influence shoulder posture.ObjectiveTo investigate the effect of the active reduction of the anterior pelvic tilt on shoulder and trunk posture during static standing posture and on the electromyographic activity of the scapular upward rotators during elevation and lowering of the arm.MethodsThirty-one young adults were assessed in a relaxed standing position and a standing position with 30% active reduction of the anterior pelvic tilt. The pelvic tilt, trunk posture, and forward shoulder posture during the static standing posture and the electromyographic activity during elevation and lowering of the arm were assessed.ResultsPaired t-tests indicated that the active reduction of the anterior pelvic tilt reduced the trunk extension (MD = 1.09; 95%CI = −2.79 to −1.03). There were no effects on the forward shoulder posture (MD = 0.09; 95%CI = −0.92 to 1.09). Repeated measures of analyses of variance indicated an increase in lower trapezius electromyographic activity (MD = 3.6; 95%CI = 1.28 to 5.92). There was a greater reduction in upper trapezius activity after pelvic tilt reduction during arm elevation (MD = 1.52%; 95%CI = −2.79 to −0.25) compared to that during the lowering phase. There were no effects of pelvic tilt reduction on the electromyographic activity of the serratus anterior (MD = 3.26; 95%CI = −3.36 to 9.87).ConclusionThe influence of pelvic posture on the trunk posture and lower trapezius activation should be considered when assessing or planning exercise for individuals with shoulder or trunk conditions.     

Nucleus pulposus deformation in response to rotation at L1–2 and L4–5

BackgroundSpinal rotation couples with lateral flexion as a composite movement. Few data report the in vivo mechanical deformation of the nucleus pulposus following sustained rotation. MRI provides a non-invasive method of examining nucleus pulposus deformation by mapping the hydration signal distribution within the intervertebral disc.MethodsT1 weighted coronal and sagittal lumbar images and T2 weighted axial images at L1–2 and L4–5 were obtained from 10 asymptomatic subjects (mean age 29, range: 24–34 years) in sustained flexed and extended positions plus combined positions of left rotation with flexion and extension. Nucleus pulposus deformation was tracked by mapping the change in hydration profiles from coronal and sagittal pixel measurements.FindingsAn average sagittal change in position of 44° (SD 14.5°) from flexion to extension was recorded between L1 and S1 (range: 18°– 60°) resulting in a mean anterior nucleus pulposus deformation of 16% of disc hydration profile (range: 3.5%–19%) in 19/20 discs. When rotation was combined with either flexion or extension, mean coronal deformation was 4.8% (SD—5.1%; range: 0.4%–15%). Lateral nucleus pulposus deformation direction varied in rotation (44% deformed left and 56% deformed right). Intersegmental lateral flexion direction more strongly predicted nucleus pulposus deformation direction with 75% deforming contralaterally.InterpretationNucleus pulposus deformation direction in young subjects was more predictable following sagittal position change than in rotation combined with flexion or extension. Deformation magnitude was reduced in rotated positions. Intersegmental lateral flexion was a stronger predictor of nucleus pulposus deformation direction.     

Does trunk and hip muscles strength predict performance during a core stability test?

BackgroundA better understanding about the relationship between trunk and hip muscles strength and core stability may improve evaluation and interventions proposed to improve core stability.ObjectivesTo investigate if trunk and hip muscles strength predict pelvic posterior rotation during the bridge test with unilateral knee extension.MethodsThis is a cross-sectional study. Sixty-one healthy individuals of both sexes (age, 28 ± 6.4 years, weight, 66.5 ± 10.9 kg, height, 167 ± 9.5 cm) performed the bridge test with unilateral knee extension. The pelvic posterior rotation during the bridge test was obtained with two-dimensional video analysis. Isometric strength of the trunk extensors and rotators, and hip abductors, external and internal rotators and extensors were measured with a hand-held dynamometer. Multiple linear regression analysis was performed to identify if the strength variables could explain the pelvic posterior rotation during the test.ResultsMuscle strength predicted pelvic posterior rotation during the bridge test (r = 0.54; p = 0.003). Strength of the trunk rotators (p = 0.045) and hip internal rotators (p = 0.015) predicted reduced magnitude of pelvic posterior rotation during the bridge test, and strength of the hip extensors (p = 0.003) predicted increased magnitude of pelvic posterior rotation.ConclusionsTrunk rotators and hip internal rotators and extensors strength predict 29% of the performance during the bridge test with unilateral knee extension. The strength of these muscles should be evaluated in individuals with increased pelvic posterior rotation during the bridge test with unilateral knee extension.     

The effect of anterior longitudinal ligament resection on lordosis correction during minimally invasive lateral lumbar interbody fusion: Biomechanical and radiographic feasibility of an integrated spacer/plate interbody reconstruction device

BackgroundLateral lumbar interbody fusion is powerful for correcting degenerative conditions, yet sagittal correction remains limited by anterior longitudinal ligament tethering. Although lordosis has been restored via ligament release, biomechanical consequences remain unknown. Investigators examined radiographic and biomechanical of ligament release for restoration of lumbar lordosis.MethodsSix fresh-frozen human cadaveric spines (L3–S1) were tested: (Miller et al., 1988) intact; (Battie et al., 1995) 8 mm spacer with intact anterior longitudinal ligament; (Cho et al., 2013) 8 mm spacer without intact ligament following ligament resection; (Galbusera et al., 2013) 13 mm lateral lumbar interbody fusion; (Goldstein et al., 2001) integrated 13 mm spacer. Focal lordosis and range of motion were assessed by applying pure moments in flexion-extension, lateral bending, and axial rotation.FindingsCadaveric radiographs showed significant improvement in lordosis correction following ligament resection (P < 0.05). The 8 mm spacer with ligament construct provided greatest stability relative to intact (P > 0.05) but did little to restore lordosis. Ligament release significantly destabilized the spine relative to intact in all modes and 8 mm with ligament in lateral bending and axial rotation (P < 0.05). Integrated lateral lumbar interbody fusion following ligament resection did not significantly differ from intact or from 8 mm with ligament in all testing modes (P > 0.05).InterpretationLordosis corrected by lateral lumbar interbody fusion can be improved by anterior longitudinal ligament resection, but significant construct instability and potential implant migration/dislodgment may result. This study shows that an added integrated lateral fixation system can significantly improve construct stability. Long-term multicenter studies are needed.     

Kinematics and load-sharing of an anterior thoracolumbar spinal reconstruction construct with PEEK rods: An in vitro biomechanical study

BackgroundPolyetheretherketone rod constructs provide adequate spinal stability. Kinematics and load sharing of anterior thoracolumbar reconstruction with polyetheretherketone rods under preload remains unknown.MethodsEight human cadaveric specimens (T11-L3) were subjected to a pure moment of 5.0 Nm in flexion-extension, lateral bending and axial rotation, and flexion-extension with a compressive preload of 300 N. An anterior reconstruction of L1 corpectomy was conducted with a surrogate bone graft and anterior rod constructs (polyetheretherketone or titanium rods). An axial load-cell was built in the surrogate bone graft to measure the compressive force in the graft. Range of motion, neutral zone and compressive force in the graft were compared between constructs.FindingsThe polyetheretherketone rod construct resulted in more motion than the titanium rod construct, particularly in extension (P = 0.011) and axial rotation (P = 0.001), but less motion than the intact in all directions except in axial rotation. There was no difference in range of motion or neutral zone between constructs in flexion-extension under preload. The polyetheretherketone rod construct kept the graft compressed 52 N which was similar to the titanium rod construct (63 N), but allowed the graft compressed more under the preload (203 N vs. 123 N, P = 0.003). The compressive forces fluctuated in flexion-extension without preload, but increased in flexion and decreased in extension under preload.InterpretationThe polyetheretherketone rod construct allowed more motion compared to the titanium rod construct, but provided stability in flexion and lateral bending without preload, and flexion and extension under preload. The anterior graft shared higher load under preload, particularly for the polyetheretherketone rod construct. The results of this study suggest that rigidity of rods in the anterior reconstruction affects kinematic behavior and load sharing.     

Are we simplifying balance evaluation in adolescent idiopathic scoliosis?

BackgroundClinical evaluation of the postural balance in adolescent idiopathic scoliosis has been measured by sagittal vertical axis and frontal balance. The impact of the scoliotic deformity in three planes on balance has not been fully investigated.Methods47 right thoracic and left lumbar curves adolescent idiopathic scoliosis and 10 non-scoliotic controls were registered prospectively. 13 spinopelvic postural parameters were calculated from the 3-dimantional reconstructions of X-rays. 7 balance variables describing the position and sway of the center of pressure were recorded using a pressure mat. A regression analysis was used to predict sagittal vertical axis and frontal balance from the 7 balance variables. A canonical correlation analysis was performed between all the postural parameters and balance variables and the significant associations between the postural and balance variables were determined.Findingssagittal vertical axis and frontal balance were not significantly associated with the position or sway of the center of pressure (p > 0.05). Canonical correlation analysis showed significant associations between the postural variables in the 3 planes and center of pressure position (R² = 0.81) and sway (R² = 0.62), p < 0.05.InterpretationFrontal Cobbs, apical rotations, distal kyphosis, pelvic incidence, sacral slope, sagittal vertical axis, and frontal balance contributed to the postural balance in the cohort. The compensatory role of the pelvis and distal kyphosis in sagittal plane was underlined. Multidimensional analyses between the postural and balance variables showed the alignment of the thoracic, lumbar, and pelvis in the 3 planes, in addition to the global head-pelvic position impact on adolescent idiopathic scoliosis balance.     

Comparative analysis of posterior fusion constructs as treatments for middle and posterior column injuries: An in vitro biomechanical investigation

BackgroundTitanium pedicle screw–rod instrumentation is considered a standard treatment for spinal instability; however, the advantages of cobalt-chromium over titanium is generating interest in orthopedic practice. The aim of this study was to compare titanium versus cobalt–chromium rods in posterior fusion through in vitro biomechanical testing.MethodsPosterior and middle column injuries were simulated at L3–L5 in six cadaveric L1-S1 human spines and different pedicle screw constructs were implanted. Specimens were subjected to flexibility tests and range of motion, intradiscal pressure and axial rotation energy loss were statistically compared among five conditions: intact, titanium rods (with and without transverse connectors) and cobalt–chromium rods (with and without transverse connectors).FindingsAll fusion constructs significantly (P < 0.01) decreased range of motion in flexion–extension and lateral bending with respect to intact, but no significant differences (P > 0.05) were observed in axial rotation among all conditions. Intradiscal pressure significantly increased (P ≤ 0.01) after fusion, except for the cobalt–chrome conditions in extension (P ≥ 0.06), and no significant differences (P > 0.99) were found among fixation constructs. In terms of energy loss, differences became significant P ≤ 0.05 between the cobalt ? chrome with transverse connector condition with respect to the cobalt–chrome and titanium conditions.InterpretationThere is not enough evidence to support that the cobalt–chrome rods performed biomechanically different than the titanium rods. The inclusion of the transverse connector only increased stability for the cobalt–chromium construct in axial rotation.     

Lower limb kinematics and hip extensors strengths are associated with performance of runners at high risk of injury during the modified Star Excursion Balance Test

BackgroundReduced trunk and lower limb movement and hip and trunk muscles weakness may compromise the athletes’ performance on the modified Star Excursion Balance Test (mSEBT).ObjectiveTo investigate the relationship of trunk and lower limb kinematics and strength with the performance on the mSEBT of runners at high risk of injury.MethodsThirty-nine runners performed the mSEBT with the dominant limb as the support limb. An Inertial System was used to capture the trunk, hip, knee and ankle movement during the mSEBT. A handheld dynamometer was used to measure the strength of trunk extensors and lateral flexors muscles, and hip extensors, lateral rotators and abductors of the support limb. Multiple regressions were used to investigate if trunk and lower limbs kinematics and trunk and hip muscles strength are associated with performance during the mSEBT.ResultsReduced hip flexion and greater knee flexion range of motion (ROM) were associated with anterior reach in the mSEBT (r² = 0.45; p < .001), greater hip flexion ROM was associated with posteromedial reach (r² = 0.15; p = .012) and greater knee flexion ROM was associated with posterolateral reach (r² = 0.23; p < .001). Hip extensor strength was associated with posteromedial (r² = 0.14; p = .017), posterolateral (r² = 0.10; p = .038) and composite reaches (r² = 0.16; p = .009).ConclusionHip and knee kinematics in the sagittal plane explained 15–45% of the runners’ performance on the mSEBT and hip extensor strength explained 10–16% of the mSEBT performance. These findings provide useful information on the contribution of joints kinematics and strength when evaluating dynamic postural control in runners at high risk of injury.     

3D correction over 2 years with anterior vertebral body growth modulation: A finite element analysis of screw positioning,cable tensioning and postoperative functional activities

BackgroundAnterior vertebral body growth modulation is a fusionless instrumentation to correct scoliosis using growth modulation. The objective was to biomechanically assess effects of cable tensioning, screw positioning and post-operative position on tridimensional correction.MethodsThe design of experiments included two variables: cable tensioning (150/200 N) and screw positioning (lateral/anterior/triangulated), computationally tested on 10 scoliotic cases using a personalized finite element model to simulate spinal instrumentation, and 2 years growth modulation with the device. Dependent variables were: computed Cobb angles, kyphosis, lordosis, axial rotation and stresses exerted on growth plates. Supine functional post-operative position was simulated in addition to the reference standing position to evaluate corresponding growth plate’s stresses.FindingsSimulated cable tensioning and screw positioning had a significant impact on immediate and after 2 years Cobb angle (between 5°–11°, p < 0.01). Anterior screw positioning significantly increased kyphosis after 2 years (6°–8°, p = 0.02). Triangulated screw positioning did not significantly impact axial rotation but significantly reduced kyphosis (8°–10°, p = 0.001). Growth plates' stresses were increased by 23% on the curve's convex side with cable tensioning, while screw positioning rather affected anterior/posterior distributions. Supine position significantly affected stress distributions on the apical vertebra compared to standing position (respectively 72% of compressive stresses on convex side vs 55%).InterpretationThis comparative numerical study showed the biomechanical possibility to adjust the fusionless instrumentation parameters to improve correction in frontal and sagittal planes, but not in the transverse plane. The convex side stresses increase in the supine position may suggest that growth modulation could be accentuated during nighttime.     

Sex differences in trunk,pelvis, hip and knee kinematics and eccentric hip torque in adolescents

BackgroundAdolescents have a high incidence of knee joint dysfunctions, with up to 28% of adolescents reporting knee pain. Although adolescent females have a greater incidence of knee injuries in comparison to males, few studies conducted biomechanical evaluations in this population aiming to identify sex differences. If trunk and/or lower limb biomechanical impairments are identified in female adolescents, the implementation of early interventions for injury prevention will be better justified. The purpose of this study was to compare the trunk, pelvis, hip and knee kinematics during a single-leg squat task, as well as the isokinetic eccentric hip torque, between male and female healthy adolescents.MethodsForty-four healthy adolescents were divided into two groups, group of males (n = 22) and group of females (n = 22). Kinematics during single-leg squat were assessed using a electromagnetic tracking system. For the evaluation of eccentric hip torque in the three planes an isokinetic dynamometer was used. Group differences were assessed using a one-way multivariate analysis of variance.FindingsResults showed that adolescent females presented greater hip adduction, hip external rotation and knee abduction, as well as smaller trunk flexion during single-leg squat in comparison to males. Additionally, adolescent females showed smaller isokinetic eccentric hip torque normalized by body mass in all planes in comparison to males.InterpretationThese sex differences in terms of trunk/lower limb kinematics and eccentric hip torque generation might play an important role in the greater incidence of overuse knee injuries observed in adolescent females.