Posterior Pelvic Rotation Research Articles

Factors related to T1 slope: spinopelvic balance and thoracic compensation

ObjectiveTo identify factors associated with T1 slope (T1S).MethodsA total of 215 patients over 18 years old who underwent whole-spine X-rays to evaluate lower back pain were enrolled in this study. T1S, pelvic tilt (PT), sacral slope (SS), pelvic incidence (PI), thoracic kyphosis (TK), lumbar lordosis (LL), cervical lordosis (CL), thoracolumbar kyphosis (TLK), and sagittal vertical axis (SVA) were measured. Patients were divided into balance, compensatory balance, thoracic compensation, and thoracic decompensation groups.ResultsTK (p < 0.001), SVA (p < 0.001), and CL (p = 0.020) were significantly related to high T1S. The balance group had the smallest PT, largest SS and largest LL of the four groups (p < 0.001). The thoracic compensation group had the smallest TK of all groups (p < 0.001). There was no significant difference in T1S between the balance and thoracic compensation groups (p = 0.099). The thoracic decompensation group had a larger T1S than the balance group (p = 0.023).ConclusionsCaudal spine segments had a sequential effect on cranial spine segments. T1S reflected the compensation ability of the spine. The absence of balance tended to increase the T1S. Pelvic posterior rotation and thoracic compensation were two crucial factors protecting against increased T1S in patients with ASD.

Kinematic and Kinetic Predictors of Y-Balance Test Performance.

BackgroundThe Y-Balance Test (YBT) assesses dynamic stability and neuromuscular control of the lower extremity. Several authors have analyzed kinematic predictors of YBT performance with conflicting results, but the influence of kinetic factors is not well understood.PurposeTo examine kinematic predictors of YBT performance and determine the joint kinetics which predict YBT performance.Study DesignCross-sectional study.MethodsThirty-one physically active individuals performed YBT trials on a force plate while whole body kinematics were recorded using a motion capture system. Sagittal, frontal, and transverse plane joint kinematics and joint moments were calculated at maximum reach in each YBT reach direction. Variables correlated with reach distances at the p < 0.2 level were entered into a stepwise linear regression.ResultsIn the anterior direction, knee flexion and torso rotation (R2=0.458, p<0.001) and knee extensor and hip abductor moments (R2=0.461, p<0.001) were the best kinematic and kinetic predictors of reach distance. In the posterior medial direction, hip flexion, ankle dorsiflexion, and ankle rotation accounted for 45.8% of the variance in reach direction (p<0.001) while hip and knee extensor, and hip abductor moments explained 72.6% of the variance in reach distance (p<0.001). In the posterior lateral direction, hip flexion and pelvic rotation (R2=0.696, p<.001) and hip extensor moments (R2=0.433, p=0.001) were the best kinematic and kinetic predictors of reach distance.ConclusionThe ability to generate large hip and knee joint moments in the sagittal and frontal plane are critical for YBT performance.Level of Evidence3.

Reliability of hip range of motion measurement among experienced arthroscopic hip preservation surgeons

The aim of this study was to determine (i) the reliability of hip range of motion measurement among experienced arthroscopic hip preservation surgeons and (ii) the magnitude of hip flexion change with posterior pelvic tilt. Five experienced arthroscopic hip preservation surgeons (5–18 years of hip surgery experience) performed passive hip range of motion (internal and external rotation), flexion (contralateral hip extended) and flexion with posterior pelvic tilt (contralateral hip maximally flexed) on five young healthy asymptomatic volunteers (three males, two females; 34.4 ± 10.7 years of age). Motion was measured via digital photography and goniometry. Inter-observer reliability was calculated via two-way mixed, single measures, intra-class correlation coefficient. Paired t-test was utilized to compare hip flexion (with contralateral hip extended) to hip flexion with posterior pelvic tilt (with contralateral hip in forced flexion). The reliabilities of measurements of hip flexion with posterior pelvic tilt and external rotation were excellent, that of hip flexion was fair, and that of hip internal rotation was poor. The magnitude of hip flexion increase with posterior pelvic tilt was 17.0° ± 3.0° (P < 0.001). The reliability of hip range of motion measurement by five experienced arthroscopic hip preservation surgeons was excellent for measures of hip flexion with posterior pelvic tilt and external rotation. Contralateral maximal hip flexion significantly increased ipsilateral hip flexion (approximately 17°). Level of Evidence: Diagnostic, level III (without consistently applied reference standard)

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±10.9kg, height, 167±9.5cm) 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.

Wheelchair Seating: Peak Pressure Distribution in Young versus Elderly Healthy Controls

Background: People may use a wheelchair when they need assistance with mobility. Some users have to remain seated in their wheelchair for most of their awake time and for a lot of activities. The need for a well fitted and supportive wheelchair is important and, for those who use the wheelchair for many hours, peak pressure distribution is of interest to prevent pressure ulcers and discomfort. Aim: To describe how high local peak pressures may be distributed over risk areas for pressure ulcers in different wheelchair settings. Methods: Two groups of healthy adults were recruited (40 elderly and 30 younger individuals). Two standard models of manual wheelchairs were used together with two types of wheelchair cushions. Results: The elderly group had a higher peak pressure over the ischial tuberosity and increased posterior pelvic rotation in the shaped seat cushion. Both groups had higher peak pressure over the trochanter in the shaped seat cushion. Peak pressure was also higher over the coccyx for the elderly in the shaped seat cushion compared with the plain cushion; this was lower for the younger group. Discussion: The results indicate that age might influence the important physical prerequisites when fitting a wheelchair to an individual.

Inter/Intraobserver Reliability of T1 Pelvic Angle (TPA), a Novel Radiographic Measure for Global Sagittal Deformity.

Reliability analysis. To assess intra- and interobserver agreement of the T1 pelvic angle (T1PA), a novel radiographic measure of spinal sagittal alignment. Orthopedic surgeons of various levels of experience measured the T1PA in a series of healthy adult volunteers. The relationship of the TIPA to pelvic position was also assessed. Recent literature suggests that the T1PA is a more reliable measure of global sagittal alignment than traditional measurements (i.e., sagittal vertical axis). Previous research focuses on postoperative patients with known spinal deformity. No published research exists evaluating the use of T1PA on healthy subjects without spinal deformity. The purpose of this study is: (1) to assess the reliability of measurements of the T1PA, (2) to examine its relationship to pelvic position. Seven evaluators of varying orthopedic experience measured the T1PA in 50 healthy adult volunteers. Subjects were radiographed in each of three pelvic positions: resting, maximal anterior pelvic rotation, and maximal posterior pelvic rotation. After a washout period, the measurement was repeated. Using intraclass correlation coefficients, the intra- and inter-rater agreement for the T1PA was measured. The collected data was also used to determine the accuracy of this measurement and its relationship to pelvic position. A very high level of agreement was found in measurements of the T1PA (intraclass correlation coefficients r = 0.98). At each pelvic position, all examiners had excellent intrarater reliability, > 0.85. The inter-rater reliability, compared with a gold standard, consistently measured the T1PA within ± 2°. The data also shows that the T1PA changes with pelvic rotation. T1PA is a reproducible and reliable measure of global sagittal alignment regardless of the level of training. The T1PA varies based on pelvic rotation; this variation must be taken into account when assigning an absolute target for correction. 4.

Effects of fresh lumbar osteoporotic vertebral compression fracture on spinopelvic sagittal parameters and distribution of Roussouly types

Objective To investigate the effects of fresh lumbar osteoporotic vertebral compression fracture (OVCF) on spinopelvic sagittal parameters and distribution of Roussouly types. Methods One hundred and eight patients with one-level fresh lumbar OVCF and 110 patients with simple osteoporosis (OP) were diagnosed and treated at Department of Orthopedic Surgery, Shougang Hospital from January 2016 to August 2017. The basic clinical data of all the patients were documented and their lumber spines were classified by Roussouly types. The 2 groups were compared in terms of spinopelvic sagittal parameters such as pelvic incidence (PI), pelvic tilt (PT), sacral slope (SS), and lumbar lordosis (LL) and Roussouly types. The correlation between Roussouly types and fracture segments was observed in OVCF group. Results There was no sig- nificant different in PI between OVCF and OP groups (50.35°±11.00° versus 51.96°±11.73°) (P>0.05). PT in OVCF group (18.79°±9.51°) was significantly larger than that (16.19°±9.03°) in OP group while SS (31.56°±7.88°) and LL (40.22°±12.29°) in the former significantly smaller than those in the latter (35.77°±8.82° and 47.89°±13.20°, respectively) (P< 0.05). Roussouly types Ⅰ, Ⅱ, Ⅲ and Ⅳ in OVCF group were 35, 40, 28 and 5 cases, respectively, with types Ⅰ and Ⅱ accounting for 69.5%; Roussouly types Ⅰ, Ⅱ, Ⅲ and Ⅳ in OP group were 17, 30, 49 and 14 cases, respectively, with type Ⅲ being predominant (44.5%). There was a significant difference between the 2 groups in distribution of Roussouly types (P<0.05). In OVCF group, fractures of L1 and L2 vertebrae accounted for 82.4%. There was a significant correlation between fracture segments and lumbar Roussouly types (P=0.034). Conclusions Patients with fresh lumbar OVCF tend to have a forward gravity and sagittal disequilibrium, leading to posterior pelvic rotation, increased PT, decreased SS, and downward shift of the apex of the lumbar curve. Their Roussouly classification is mainly type Ⅰor type Ⅱ. Key words: Lumbar vertebrae; Osteoporosis; Fractures, compression; Roussouly classification; Spinopelvic sagittal parameters

Postoperative changes in sagittal spinopelvic alignment in sitting position in adolescents with idiopathic thoracic scoliosis treated with posterior fusion: an initial analysis.

OBJECTIVE Previous studies have reported spinal straightening and pelvic retroversion when changing from erect to sitting posture in patients with adolescent idiopathic scoliosis (AIS), which were thought to be related to low-back pain after sitting for long periods. However, the sitting sagittal alignment after posterior spinal fusion has not been evaluated. This study aims to assess the influence of posterior fusion surgery upon sitting sagittal spinopelvic alignment in adolescents with idiopathic thoracic curves (thoracic AIS [T-AIS]). METHODS A total of 44 T-AIS patients (30 Lenke I and 14 Lenke II) from the authors' center were included in this study. Preoperative and postoperative long-cassette lateral radiographs of the spine and pelvis were obtained with the patients in standing and sitting positions. Thoracic kyphosis (TK), lumbar lordosis (LL), pelvic incidence (PI), sacral slope (SS), and pelvic tilt (PT) were measured on standing and sitting lateral radiographs. Patients were divided into selective thoracic fusion (STF) and nonselective thoracic fusion (NSTF) groups. RESULTS At baseline, TK, LL, and SS decreased by 27.5%, 42.1%, and 31.1%, respectively, from the standing to the sitting position, while PT increased by 193.6%. After posterior spinal fusion, increased TK, LL, and SS and corresponding decreased PT were observed compared to baseline parameters in the sitting position. Comparison of postoperative sitting and standing values for the whole cohort showed that the mean LS and SS values were significantly lower in the sitting position (decreased by 14.0% and 13.9%, respectively, compared to standing), whereas the mean PT value was significantly greater (increased by 39.0%, compared to standing). Similar changes were also observed in the STF group: postoperatively the mean LL value was 15.6% lower in sitting than in standing, while the mean SS value was 11.5% lower. However, no obvious changes of the postoperative values in sitting were found in the NSTF group. CONCLUSIONS Nonselective thoracic fusion surgery in T-AIS patients diminished spinal straightening and pelvic retroversion during sitting. Reducing distal fusion levels was of special value in not only saving more lumbar mobility, but also preserving the function of pelvic posterior rotation.

The effect of pelvic motion on spinopelvic parameters

Background ContextTo date, many studies have examined how pelvic position affects the spinal curvature and spinopelvic parameters. However, these studies focus on a static relationship, comparing pelvis and spine in a relaxed or baseline position only. Indeed, the spinopelvic connection is dynamic, as subjects can easily be taught to rotate their pelvis anteriorly or posteriorly on the femoral head, all while maintaining an erect posture. Therefore, for a true understanding of pelvic influence on the spinal column, it is necessary to examine spinopelvic parameters in multiple pelvic positions within the same subject. PurposeThe objective of this study was to examine the dynamic effect of pelvic motion on the spine and associated radiographic parameters. Study DesignThis is a single-center, cross-sectional study of 50 healthy, asymptomatic volunteers. Patient SampleSubjects were recruited and screened based on the following criteria: between 18 and 79 years of age; no known spinal, pelvic, or lower extremity pain lasting for >48 hours; no history of spinal, pelvic, or lower extremity dysfunction requiring medical care; no radiographic evidence of spinal or pelvic abnormality, scoliosis deformity, or other associated spinal pathologies; not currently pregnant and with no possibility of being pregnant; and a body mass index of <30. 64. The subjects were screened and 14 were excluded for a total of 50 subjects. Outcome MeasuresThe outcome measures included thoracic kyphosis (TK), lumbar lordosis (LL), sagittal vertical axis (SVA), pelvic tilt (PT), sacral slope (SS), and pelvic incidence (PI). Materials and MethodsThis study was funded by a Small Exploratory Research Grant from the Scoliosis Research Society. Each subject was instructed and observed to stand in three different positions: pelvic resting, anterior pelvic rotation, and posterior pelvic rotation. Lateral standing radiographs were taken in each position and each image was examined by an orthopedic spine surgeon who digitally measured the TK, LL, SVA, PT, SS, and PI. The data were then statistically examined to determine the affect of pelvic position on each parameter. ResultsSubjects demonstrated a measurable, statistically significant change in each parameter with pelvic rotation. There was a clear pattern of change for LL, PT, and SS with the anterior and posterior pelvic rotations. A change in LL demonstrated a strong correlation with changes in all measured parameters with pelvic rotation. ConclusionsIn asymptomatic subjects, pelvic motion affects the position of the spinal column and resultant spinopelvic parameters. The results of this study demonstrate that one can intentionally change the position of the pelvis and the adjacent spinal column in space. Knowledge of this relationship is important to the understanding of sagittal balance and could influence the treatment of patients with spinal deformity.

Pelvic incidence: a fixed value or can you change it?

Background ContextThere has been renewed interest in the pelvic vertebrae by spinal surgeons recently. Those involved in working with patients with adult spinal deformity focus on the position of the fused spine as it relates to the pelvis, and determine success or failure by specific numbers for given pelvic parameters. The pelvic parameters that are commonly measured for these patients are pelvic tilt, sacral slope, and pelvic incidence (PI). Out of the three, PI has always been considered to be the fixed measurement, whereas pelvic tilt and sacral slope have the capacity to change in relation to external forces. The assumption that the PI does not change has not been proven in a healthy, asymptomatic population. PurposeThis study aimed to investigate the differences in PI between three pelvic positions used in common functional activities: resting baseline pelvic posture, maximal anterior pelvic rotation, and maximal posterior pelvic rotation. Study Design/SettingThis was a randomized, prospective study of 50 healthy, asymptomatic, individuals who were recruited from the vicinity of our institution. Patient SampleFifty patients (16 men with a mean age of 26.5±12.1 years; 34 women with a mean age of 27.2±10.8 years) were recruited for this study. Initial screening occurred by telephone. The inclusion criteria consisted of participants being between 18 and 79 years of age, no previous history of spine, pelvic, or lower extremity pain which had lasted longer than 48 hours, or history of any disorder in the spine, pelvis, or lower extremity that had required medical care. Female patients could not be pregnant at the time of participation. Outcome MeasuresChanges in PI were assessed by examining the differences between the values of the PI with each change in pelvic position: resting to maximal anterior pelvic rotation and resting to maximal posterior pelvic rotation. Inter-rater reliability was assessed using Cronbach's alpha. MethodsThis study was funded by a Small Exploratory Grant from the Scoliosis Research Society. All subjects had an initial posterior-anterior and lateral radiograph taken in their resting pelvic position. If no spinal deformity was noted, each subject was instructed to maximally rotate their pelvis anteriorly and an immediate lateral radiograph was taken. The subject was then instructed to maximally rotate their pelvis posteriorly and an immediate lateral radiograph was again taken. Radiographic measurements of PI were independently measured by a board-certified, fellowship trained orthopedic spine surgeon and a board-certified musculoskeletal radiologist after defining and agreeing to the specific manner of measurement. ResultsPelvic incidence values changed in 44 of 50 subjects (88%) when they maximally anteriorly rotated their pelvis from the resting pelvic position. The mean change was 2.9°, with 23 of 50 subjects (46%) changing ≥3°. Pelvic incidence values changed in 40 of 50 subjects (80%) when they maximally posteriorly rotated their pelvis from the resting position. The mean change was 2.82° with 27 of 50 subjects (54%) changing by ≥3°. ConclusionsThis study demonstrated that for a high percentage of the healthy subjects who participated, the PI changed when the subjects varied their pelvic position. This questions the assumption that PI is a fixed parameter and suggests a potential functional motion at the sacroiliac joint. It also supports the idea that intentionally changing one's posture could lead to a change in PI, an idea that could have ramifications in surgical cases.

Pelvic Rotation in Femoroacetabular Impingement Is Decreased Compared to Other Symptomatic Hip Conditions.

Study Design Cross-sectional, case-control design. Background Pelvic movement has been considered a possible discriminating parameter associated with femoroacetabular impingement (FAI) symptom onset. Decreased pelvic rotation has been found during squatting in people with FAI when compared to people with healthy hips. However, it is possible that changes in pelvic movement may occur in other hip conditions because of pain and may not be specific to FAI. Objectives To compare sagittal pelvic rotation during hip flexion and in sitting between people with FAI and people with other symptomatic hip conditions. Methods Thirty people with symptomatic FAI, 30 people with other symptomatic hip conditions, and 20 people with healthy hips participated in the study. Sagittal pelvic rotation was calculated based on measures of pelvic alignment in standing, hip flexion to 45° and 90°, and sitting. Results There were significant differences in sagittal pelvic rotation among the 3 groups in all conditions (P<.05). Post hoc analyses revealed that participants in the symptomatic FAI group had less pelvic rotation during hip flexion to 45° and 90° compared to participants in the other symptomatic hip conditions group and the hip-healthy group (mean difference, 1.2°-1.9°). In sitting, participants in the other symptomatic hip conditions group had less posterior pelvic rotation compared to those in the hip-healthy group (mean difference, 3.9°). Conclusion People with symptomatic FAI have less posterior pelvic rotation during hip flexion when compared to people with other symptomatic hip conditions and those with healthy hips. Level of Evidence Diagnosis, level 4. J Orthop Sports Phys Ther 2016;46(11):957-964. Epub 29 Sep 2016. doi:10.2519/jospt.2016.6713.

Postural changes and their effects in elite riders when actively influencing the horse versus sitting passively at trot

The objectives were to compare sagittal plane posture of the pelvis, trunk and head of elite dressage riders when they ride actively to train the horse versus sitting passively and following the horses’ movements at trot, and to evaluate the effects of these changes in rider posture on load distribution on the horse’s back. Synchronised motion capture and saddle mat data of seven elite dressage riders were used to measure minimal and maximal angles and range of motion (ROM) for the pelvic, trunk and head segments, the angle between pelvis and trunk segments, phase-shift between pitching motions of pelvis and trunk, and pelvic translation relative to the saddle. Non-parametric statistical tests compared variables between the two rider postures. In the passive rider posture the pelvis, trunk and head showed two pitching cycles per stride. Maximal posterior and anterior pelvic rotation occurred, respectively, early and late in the horse’s diagonal stance phase. Compared with pelvic movements, trunk movements were slightly delayed and head movements were out-of-phase. In the active rider posture the pelvis and trunk pitched further posteriorly throughout the stride. Most of the riders showed similar sagittal plane movements of the axial body segments but with some notable individual variations.

A quantitative measurement method for comparison of seated postures

This technical note proposes a method to measure and compare seated postures. The three-dimensional locations of palpable anatomical landmarks corresponding to the anterior superior iliac spines, clavicular notch, head, shoulders and knees are measured in terms of x, y and z co-ordinates in the reference system of the measuring apparatus. These co-ordinates are then transformed onto a body-based axis system which allows comparison within-subject. The method was tested on eleven unimpaired adult participants and the resulting data used to calculate a Least Significant Difference (LSD) for the measure, which is used to determine whether two postures are significantly different from one another.The method was found to be sensitive to the four following standardised static postural perturbations: posterior pelvic tilt, pelvic obliquity, pelvic rotation, and abduction of the thighs. The resulting data could be used as an outcome measure for the postural alignment aspect of seating interventions in wheelchairs.

Kinematic gait deficits at the trunk and pelvis: characteristic features in children with hereditary spastic paraplegia.

To examine the kinematic gait deviations at the trunk and pelvis of children with hereditary spastic paraplegia (HSP). This exploratory observational study quantified gait kinematics for the trunk and pelvis from 11 children with HSP (7 males, 4 females) using the Gait Profile Score and Gait Variable Scores (GVS), and compared the kinematics to data from children with typical development using a Mann-Whitney U test. Children with HSP (median age 11y 4mo, interquartile range 4y) demonstrated large deviations in the GVS for the trunk and pelvis in the sagittal and coronal planes when compared to the gait patterns of children with typical development (p=0.010-0.020). Specific deviations included increased range of movement for the trunk in the coronal plane and increased excursion of the trunk and pelvis in the sagittal plane. In the transverse plane, children with HSP demonstrated later peaks in posterior pelvic rotation. The kinematic gait deviations identified in this study raise questions about the contribution of muscle weakness in HSP. Further research is warranted to determine contributing factors for gait dysfunction in HSP, especially the relative influence of spasticity and weakness.

Comparison of EMG Activity of the Posterior Oblique Sling Muscles and Pelvic Rotation During Prone Hip Extension With and Without Lower Trapezius Pre-Activation

Background: Prone hip extension (PHE) can be performed to measure the lumbopelvic motor patterns and motions. Imbalances in lumbopelvic muscle activity and muscle weakness can result in instability including pain in lumbopelvic region. The posterior oblique sling (POS) muscles contribute to dynamic lumbopelvic stability. In addition, POS are anatomically aligned with the trapezius muscle group according to shoulder positions. Objects: This study compared the electromyography (EMG) activity of POS and pelvic compensations during PHE with and without pre-activation of lower trapezius muscle (lowT). Methods: Sixteen healthy males were recruited. PHE was performed in randomized order: PHE with and without lowT pre-activation. Surface EMG signals were recorded for biceps femoris (BF), gluteus maximus (GM) (ipsilateral), lumbar multifidus (MF) (bilateral), and the lowT (contralateral). An electromagnetic tracking motion analysis was used to measure the angle of pelvic rotation and anterior tilting. Results: The ipsilateral GM and bilateral MF EMG amplitudes were greater during PHE with lowT pre-activation compared to PHE without lowT pre-activation (p<.05). The BF amplitude during PHE without lowT pre-activation was significantly greater than that during PHE with lowT pre-activation (p<.05). The angles of pelvic rotation and anterior tilting during PHE with lowT pre-activation were significantly smaller compared to PHE without lowT pre-activation (p<.05). Conclusion: PHE with lowT pre-activation, which is aligned with the POS, showed more increased MF and GM muscular activity with smaller lumbopelvic compensations in rotation and anterior tilting compared to PHE without lowT pre-activation.

The Effect of Wallet Thickness on Spine Posture, Seat Interface Pressure, and Perceived Discomfort During Sitting

OCCUPATIONAL APPLICATIONS Occupational sitting has been associated with an increased risk for developing low back pain. The present investigation examined the effects of asymmetrical sitting surfaces induced by a wallet on acute changes in spine/pelvis posture, interface pressure, and discomfort. Compared to level sitting, sitting on a wallet resulted in greater sagittal and lateral spine flexion, a smaller total contact area with the seat pan, and greater gluteal discomfort. At wallet thicknesses of 22 mm and thicker, seat pan contact pressure area decreased and thoracic spine and pelvic angles deviated laterally compared to the no-wallet condition. At a 32-mm wallet thickness, gluteal discomfort increased. These results indicate that sitting for brief periods (15 minutes) on an uneven seating surface greater than 32 mm in thickness causes postural deviations from neutral spine positions and increases gluteal discomfort. This study supports the removal of rear pocket items, especially larger ones, during sitting.TECHNICAL ABSTRACT Background: Occupations in mobile or office settings can involve prolonged seated exposures, increasing the likelihood of low back pain development. The seat-occupant interface can be impeded by wallets or other objects (cell phones, paper documents, etc.) placed in the rear pocket, potentially increasing the risk of developing low back pain directly (nerve compression) or indirectly (altered kinematics). However, there are no published studies that have examined the effect of an uneven seating surface. Purpose: This study aimed to quantify the outcomes of a non-level sitting surface on trunk kinematics, seat pan pressure distribution, and discomfort. Gender differences in responses were also examined. Methods: Twelve males and 12 females sat for 15 minutes each on 4 wallet thicknesses (0, 12, 22, and 32 mm). Sagittal and frontal plane angles of the thoracic, lumbar spine and the pelvis were measured. Seat pressure distribution (total pressure area) and discomfort using a 100-mm visual analogue scale were also collected for each thickness. Results: In the 22- and 32-mm conditions, there was greater pelvic posterior rotation, pelvic left lateral bending, thoracic flexion, and thoracic right lateral bending compared to the 0-mm condition. Males and females showed differences in the magnitude of lateral bend angles at all spine levels; however, both genders demonstrated the same directions of postural compensation. Total pressure area decreased and gluteal discomfort increased with thicker wallets, reaching significance in the 22- and 32-mm conditions, respectively. Conclusions: Sitting on wallets greater than 32 mm in thickness increased gluteal discomfort reporting after short duration exposures. Asymmetrical sitting promotes non-neutral spine postures and reduces seat pan contact area. Asymmetrical sitting is therefore not recommended, even for short duration exposures.

The influence of changes in trunk and pelvic posture during single leg standing on hip and thigh muscle activation in a pain free population

BackgroundThigh muscle injuries commonly occur during single leg loading tasks and patterns of muscle activation are thought to contribute to these injuries. The influence trunk and pelvis posture has on hip and thigh muscle activation during single leg stance is unknown and was investigated in a pain free population to determine if changes in body posture result in consistent patterns of changes in muscle activation.MethodsHip and thigh muscle activation patterns were compared in 22 asymptomatic, male subjects (20–45 years old) in paired functionally relevant single leg standing test postures: Anterior vs. Posterior Trunk Sway; Anterior vs. Posterior Pelvic Rotation; Left vs. Right Trunk Shift; and Pelvic Drop vs. Raise. Surface EMG was collected from eight hip and thigh muscles calculating Root Mean Square. EMG was normalized to an “upright standing” reference posture. Repeated measures ANOVA was performed along with associated F tests to determine if there were significant differences in muscle activation between paired test postures.ResultsIn right leg stance, Anterior Trunk Sway (compared to Posterior Sway) increased activity in posterior sagittal plane muscles, with a concurrent deactivation of anterior sagittal plane muscles (p: 0.016 - <0.001). Lateral hip abductor muscles increased activation during Left Trunk Shift (compared to Right) (p :≤ 0.001). Lateral Pelvic Drop (compared to Raise) decreased activity in hip abductors and increased hamstring, adductor longus and vastus lateralis activity (p: 0.037 - <0.001).ConclusionChanges in both trunk and pelvic posture during single leg stance generally resulted in large, predictable changes in hip and thigh muscle activation in asymptomatic young males. Changes in trunk position in the sagittal plane and pelvis position in the frontal plane had the greatest effect on muscle activation. Investigation of these activation patterns in clinical populations such as hip and thigh muscle injuries may provide important insights into injury mechanisms and inform rehabilitation strategies.

The pelvifemoral rhythm in cam-type femoroacetabular impingement

BackgroundThere is growing evidence that femoroacetabular impingement is a potentially important risk factor for the development of early idiopathic osteoarthritis in the nondysplastic hip. Understanding of affected joint kinematics is a basic prerequisite in the evaluation of mechanical disorders in a clinical and research oriented setting. The aim of the present study was to compare pelvifemoral kinematics between subjects diagnosed with femoroacetabular impingement and healthy controls. MethodsThe authors collected motion data of the femur and pelvis on a total of 43 hips – 19 cam impingement hips and 24 healthy controls – using a validated electromagnetic tracking device. The pelvifemoral rhythm in supine position was defined during both active and passive hip flexion and statistically compared between both groups. FindingsA significant increase in posterior pelvic rotation was observed during active hip flexion in the femoroacetabular impingement group compared with the control group (P<0.001). During passive hip flexion, however, posterior pelvic rotation between the impingement group and the controls did not differ significantly (P=0.628). InterpretationPosterior pelvic rotation during active high-end hip flexion is increased in femoroacetabular impingement, indicating the presence of an active compensational mechanism that decreases the extent of harmful joint conflict during high-flexion activities.

The Impact of Mobile Data Terminal Use on Posture and Low-Back Discomfort When Combined With Simulated Prolonged Driving in Police Cruisers

The introduction of mobile computing within a constrained vehicle environment has led to changes in the task demands of occupational groups such as professional drivers and law enforcement officers. The purpose of this study was to examine how mobile data terminal (MDT) use interacts with prolonged driving to induce postural changes or low-back discomfort. Eighteen participants (9 male, 9 female) completed two 120-min simulated driving sessions. Time-varying lumbar spine and pelvis postures, seat pan interface pressures and ratings of perceived discomfort were recorded at 15-min intervals. The introduction of a computer interface decreased pelvic posterior rotation by an average of 15° with respect to upright standing and increased peak average discomfort in the neck (5.9 mm), left shoulder (6.8 mm), midback (10.9 mm), low back (10.6 mm) and pelvis (11.5 mm) compared to driving alone. The incorporation of mobile computing warrants consideration in the design of vehicle work environments.

Gender Differences in Trunk and Pelvic Kinematics During Prolonged Ergometer Rowing in Adolescents

The trunk and pelvis kinematics of 20 healthy male and female adolescent rowers were recorded during an ergometer trial using an electromagnetic tracking system (Fastrak). The kinematics of each drive phase were collected during the 1st and 20th minute, respectively. The mean and range of the kinematics, stroke rate and stroke length were compared between genders and over time. Male rowers postured their pelvis with more posterior tilt and their thoracic spine in more flexion than female rowers (P < .05). Both genders postured their pelvis in more posterior pelvic rotation and upper trunk in more flexion over time. Male rowers were found to have a significantly shorter drive phase than female rowers (P = .001). Differences in trunk and pelvic kinematics between adolescent male and female rowers suggest potentially various mechanisms for biomechanical stress. Assessment and training of rowers should take gender differences into consideration.