Sagittal Motion Research Articles

Measurement Error of Lumbar Total Disc Replacement Range of Motion

A retrospective review of lumbar total disc replacement (TDR) radiographs. To determine the error and variability in measuring TDR radiographic range of motion (ROM). Motion preservation is the driving force behind lumbar TDR technology. In the recent literature, sagittal radiographic TDR ROM as low as 2 degrees has been reported. In these studies, ROM was determined by using the Cobb method to measure TDR sagittal alignment angles in flexion-extension lateral radiographs. However, previous studies in the spinal deformity literature have shown that the Cobb method is very susceptible to measurement error. There were 5 observers, including 2 attending orthopedic spine surgeons, 1 spine fellow, 1 fifth-year resident, and 1 fourth-year resident, who measured the ROM of 50 ProDisc II (Synthes Spine Solutions, New York, NY) TDRs on standard flexion-extension lumbar spine radiograph sets. Repeated measurements were made on 2 occasions using the Cobb method. Measurement variability was calculated using 3 statistical methods. The 3 statistical methods resulted in extremely similar values for TDR ROM observer variability. Overall, the intraobserver variability of TDR ROM measurement was +/-4.6 degrees, and interobserver variability was +/-5.2 degrees . To be 95% certain that an implanted TDR prosthesis has any sagittal motion, a ROM of at least 4.6 degrees must be observed, which is the upper limit of intraobserver measurement variability for a TDR with a true ROM of 0 degrees. To be 95% certain that a change in TDR ROM has occurred between 2 measurements by the same observer, a change in ROM of at least 9.6 degrees must be observed (the entire range of +/-4.6 degrees intraobserver variability). ROM measurement variability should be considered when evaluating the success or failure of motion preservation in lumbar TDR.

Effects of Ankle-Foot Orthoses on Ankle and Foot Kinematics in Patient With Ankle Osteoarthritis

Huang Y-C, Harbst K, Kotajarvi B, Hansen D, Koff MF, Kitaoka HB, Kaufman KR. Effects of ankle-foot orthoses on ankle and foot kinematics in patient with ankle osteoarthritis. Objective To determine if different foot orthoses have a similar effect on foot kinematics in subjects with ankle osteoarthritis (OA) when walking on various ground conditions. Design Within-subject comparisons study. Setting Biomechanics research laboratory. Participants Thirteen subjects with unilateral ankle OA. Interventions Custom-made ankle-foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A) were used by subjects when walking on level, ascending and descending ramp, and side-slope conditions. Main Outcome Measures The range of motion of the hindfoot (calcaneus relative to tibia) and forefoot (metatarsal relative to calcaneus) was measured using an 8-camera motion analysis system. Results The AFO and HFO-R provided the best sagittal plane hindfoot motion restriction over all ground conditions ( P<.001). The HFO-R allowed the greatest sagittal plane forefoot motion when walking over level ( P=.01) and side-slope ( P<.02) conditions, the greatest frontal plane forefoot motion walking down the ramp ( P=.003), and the greatest transverse plane forefoot motion when walking over level ( P=.011) and ramp-ascending conditions ( P=.005). The HFO-A restricted motion of the unaffected joint and did not effectively restrict hindfoot motion. Conclusions The HFO-R not only provides selective restriction to the ankle-hindfoot motion, but also allows sufficient forefoot motion compared with the AFO. We consider the HFO-R to be the best option of all tested orthoses for treating patients with ankle OA pain arising from ankle motion.

Effect of bilateral facetectomy of thoracolumbar spine T11–L1 on spinal stability

Spinal stenosis can be found in any part of the spine, though it is most commonly located on the lumbar and cervical areas. It has been documented in the literature that bilateral facetectomy in a lumbar motion segment to increase the space induces an increase in flexibility at the level at which the surgery was performed. However, the result of bilateral facetectomy on the stability of the thoracolumbar spine has not been studied. A nonlinear three-dimensional finite element (FE) model of thoracolumbar T11-L1 was built to explore the influence of bilateral facetectomy. The FE model of T11-L1 was validated against published experimental results under various physiological loadings. The FE model with bilateral facetectomy was evaluated under flexion, extension, lateral bending and axial rotation to determine alterations in kinematics. Results show that bilateral facetectomy causes increase in motion, considerable increase in axial rotation and least increase in lateral bending. Removal of facets did not result in significant change in the sagittal motion in flexion and extension.

Dependence of joint stiffness on the conditions of visual control in upright undisturbed stance in humans

We recorded the sagittal and frontal components of the stabilogram of healthy humans in upright undisturbed stance under five conditions of visual control: (i) open eyes (OE); (ii) closed eyes (CE); (iii) visual inversion (VI); (iv) central vision (CV), and (v) diffused light (DL). Through a low-pass filter of trajectories of the center of pressure of feet (CPF), the vertical projection of the center of gravity (CG) and, consequently, the difference CPF-CG were estimated. The former represents the controlled variable, while the latter is proportional to the horizontal acceleration and assumed to express the resultant joint stiffness (mostly in the ankle joints). The stiffness was characterized through a method based on spectral analysis of the CPF-CG variable and subsequent calculations of the median frequency (MF) and the root mean square (RMS) of the spectra. The median frequencies of the spectra of the CPF-CG variable changed slightly under various visual conditions. At standing on a rigid support, they varied from 0.97 to 0.99 Hz and from 0.93 to 0.97 Hz for the CPF-CG, calculated from the sagittal and frontal components of the stabilogram, respectively. Under conditions of a pliable support, the corresponding frequencies varied within the limits of 0.79–0.83 Hz and 0.74–0.78 Hz. In contrast to the median frequencies, the RMSs demonstrated greater variability depending on different visual conditions. At standing on a rigid support, paired comparisons showed significant differences between the RMSs of the spectra of the CPF-CG variable of the sagittal direction under CE and OE conditions (0.14 ± 0.030 and 0.09 ± 0.020 mm, respectively) and under DL and OE conditions (0.130 ± ± 0.025 and 0.090 ± 0.020 mm, respectively). The RMS of the CPF-CG variable calculated for the frontal stabilogram differed significantly from each other for the VI and OE conditions (0.115 ± 0.020 and 0.075 ± ± 0.015 mm, respectively). In case of standing on a pliable support, a greater variability of visual influences on the CPF-CG variable was found. The RMS for its sagittal motion was the greatest under CE conditions (0.19 ± 0.03 mm); it was significantly greater than the respective values under OE, CV, and DL conditions (0.097 ± ± 0.020, 0.110 ± 0.020, and 0.140 ± 0.030 mm, respectively). The means of RMSs of the spectra of the frontal CPF-CG was also the greatest under CE conditions (0.20 ± 0.03 mm) and the smallest under OE conditions (0.095 ± 0.020 mm). In addition, the value of the RMS fluctuations under CE conditions (0.150 ± 0.025 mm) differed significantly from the respective values under OE conditions (0.095 ± 0.020 mm) and CV conditions (0.110 ± 0.020 mm). Thus, our findings support the statement that the influence of visual conditions on the maintenance of vertical stance is mediated (at least partially) by the mechanisms controlling the ankle joint stiffness. This regulation is mostly manifested in changes of a single parameter, the amplitude of fluctuations of the CPF-CG variable. We also found that the joint stiffness can be modulated by both nonspecific visual influences (which, in particular, reflect the perception of illumination) and specific visual influences, related to information on the position of the body and on its movements with respect to external objects.

Finite element analysis of head–neck kinematics during motor vehicle accidents: Analysis in multiple planes

In this study, a detailed three-dimensional head–neck (C0–C7) finite element (FE) model developed previously based on the actual geometry of a human cadaver specimen was used. Five simulation analyses were performed to investigate the kinematic responses of the head–neck complex under rear-end, front, side, rear- and front-side impacts. Under rear-end and front impacts, it was predicted that the global and intervertebral rotations of the head–neck in the sagittal plane displayed nearly symmetric curvatures about the frontal plane. The primary sagittal rotational angles of the neck under direct front and rear-end impact conditions were higher than the primary frontal rotational angles under other side impact conditions. The analysis predicted early S-shaped and subsequent C-shaped curvatures of the head–neck complex in the sagittal plane under front and rear-end impact, and in the frontal plane under side impact. The head–neck complex flexed laterally in one direction with peak magnitude of larger than 22° and a duration of about 130 ms before flexing in the opposite direction under both side and rear-side impact, compared to the corresponding values of about 15° and 105 ms under front-side impact. The C0–C7 FE model has reasonably predicted the effects of impact direction in the primary sagittal and frontal segmental motion and curvatures of the head–neck complex under various impact conditions.

Kinematics of stair descent in young and older adults and the impact of exercise training

Stair descent is a challenging task in old age. This study firstly investigated lower extremity kinematics during stair descent in young (YOU) and healthy, community dwelling older adults (OLD). Secondly, the impact of an exercise training intervention on age-related differences in stair descent was assessed. At baseline, a motion analysis system was used to determine spatio-temporal gait variables and lower extremity kinematics as YOU (n=23, age=27+/-3 years) and OLD (n=34, age=73+/-4 years) descended a three step staircase. The older adults were then divided into training (TRA) and control (CON) groups. For 12 months, TRA performed resistance, aerobic, balance, and flexibility exercises under supervision in a class environment (twice per week) and unsupervised at home (once per week). CON carried on with normal daily activities. Following the intervention, baseline measurements were repeated in TRA and CON. At baseline, total descent, stride cycle, and single support times were longer in OLD than in YOU. In addition, sagittal plane knee motion was lower in OLD whilst frontal and transverse plane pelvis and hip motion were higher in OLD. Exercise training did not reduce the age-related differences observed. In conclusion healthy older adults perform stair descent at a slower speed and with greater motion outside the plane of progression than young adults. We found no evidence that these differences are reduced by generic exercise training, at least in non-frail older adults.

The Effect of Custom-Made Braces for the Ankle and Hindfoot on Ankle and Foot Kinematics and Ground Reaction Forces

Kitaoka HB, Crevoisier XM, Harbst K, Hansen D, Kotajarvi B, Kaufman K. The effect of custom-made braces for the ankle and hindfoot on ankle and foot kinematics and ground reaction forces. Objective To assess the effects on gait of custom-made polypropylene orthoses: ankle-foot orthosis (AFO), rigid hindfoot orthosis (HFO-R), and articulated hindfoot orthosis (HFO-A). Design Experimental assessment. Setting Institutional practice, motion analysis laboratory. Participants Twenty asymptomatic normative subjects. Interventions Not applicable. Main Outcome Measures Three-dimensional kinematics, ground reaction force, and time-related factors in 4 conditions: shoe only, and shod with the AFO, HFO-R, and HFO-A. Results The AFO and HFO-R limited sagittal and coronal plane ankle-hindfoot motion. The HFO-A limited hindfoot coronal motion while allowing normal sagittal motion. At the midfoot, the AFO and HFO-A limited transverse motion, but the HFO-A also limited sagittal and coronal motion. Use of the HFO-R resulted in exaggerated midfoot sagittal and coronal motion. Braces that limited motion to a greater degree were associated with more atypical kinetic variables, indicative of less dynamic gait. The HFO-A resulted in ground reaction forces most similar to unbraced conditions. Conclusions Alteration in gait was affected by orthosis design. Orthoses with a rigid component crossing a joint restricted motion at that joint, but potentially compromised typical gait kinetic factors. For immobilizing the hindfoot, the HFO-A may be more comfortable and still provide more stability than the HFO-R or AFO.

Tibialis Anterior Tendon Transfer for Calcaneus Deformity in Children with Myelomeningocele: A Preliminary Report

Purpose : To examine the results of tibialis anterior tendon transfer for the treatment of a calcaneus deformity in children with a myelomeningocele. Materials and Methods : Twenty-seven feet in sixteen children were examined in this study. The mean age at the time of surgery was 7+2 years (range, 4+11-14+9) and the mean follow up duration was 25 months (range, 15-50). Three-dimensional gait analysis and dynamic foot-pressure measurement were performed to analyze the results of the index operation. Results : There was no recurrence or aggravation of the deformity. The sagittal kinematics of the ankle improved, and the relative impulse of the calcaneus decreased postoperatively. Those patients with an increased range of motion of the pelvic rotation during gait showed less improvement in the relative impulse of the calcaneus than those with a good range of pelvic rotation. They also had a lower range of knee sagittal motion and an increased range of abduction of the hip, and up-obliquity of the pelvis. Conclusion : A good range of motion of the hip and pelvis in coronal and transverse planes, and of the knee in the sagittal plane are important predictors of the functional transfer of tibialis anterior tendon in patients with a calcaneal gait in a myelomeningocele.

Correlation between respiration-induced thoracic expansion and a shift of central structures

The fusion of computed tomography (CT) and positron emission tomography (PET) may improve diagnostic accuracy, but is limited by different breathing protocols. This study aimed at quantifying respiration-induced alignment errors. PET-CT was acquired in 24 patients. Contrast-enhanced whole-body CT was obtained in a single breath hold in the expiratory state of a normal breathing cycle. An inspiratory low-dose CT of the thorax was acquired in the same session, and comparison of the two CT scans was used to assess the potential mismatch of PET and CT fusion. The largest craniocaudal expansion was found in the area of the diaphragm. A considerable sagittal expansion was found in the anterior parts of the lungs. Central tracheo-bronchial structures were displaced during inspiration mainly in the anterior and caudal directions. The craniocaudal shift of central structures showed a linear correlation with the diaphragmatic expansion, whereas the sagittal shift correlated with the sagittal pleural expansion. There was, however, no correlation between craniocaudal and sagittal respiratory motion. Alignment errors are most severe in the base of the lung, but central structures are affected, too. Understanding of the main vectors of respiratory motion may help in image interpretation when PET and CT are acquired separately.

Lumbar segmental instability: a criterion-related validity study of manual therapy assessment

BackgroundMusculoskeletal physiotherapists routinely assess lumbar segmental motion during the clinical examination of a patient with low back pain. The validity of manual assessment of segmental motion has not, however, been adequately investigated.MethodsIn this prospective, multi-centre, pragmatic, diagnostic validity study, 138 consecutive patients with recurrent or chronic low back pain (R/CLBP) were recruited. Physiotherapists with post-graduate training in manual therapy performed passive accessory intervertebral motion tests (PAIVMs) and passive physiological intervertebral motion tests (PPIVMs). Consenting patients were referred for flexion-extension radiographs. Sagittal angular rotation and sagittal translation of each lumbar spinal motion segment was measured from these radiographs, and compared to a reference range derived from a study of 30 asymptomatic volunteers. Motion beyond two standard deviations from the reference mean was considered diagnostic of rotational lumbar segmental instability (LSI) and translational LSI. Accuracy and validity of the clinical assessments were expressed using sensitivity, specificity, and likelihood ratio statistics with 95% confidence intervals (CI).ResultsOnly translation LSI was found to be significantly associated with R/CLBP (p < 0.05). PAIVMs were specific for the diagnosis of translation LSI (specificity 89%, CI 83–93%), but showed poor sensitivity (29%, CI 14–50%). A positive test results in a likelihood ratio (LR+) of 2.52 (95% CI 1.15–5.53). Flexion PPIVMs were highly specific for the diagnosis of translation LSI (specificity 99.5%; CI 97–100%), but showed very poor sensitivity (5%; CI 1–22%). Likelihood ratio statistics for flexion PPIVMs were not statistically significant. Extension PPIVMs performed better than flexion PPIVMs, with slightly higher sensitivity (16%; CI 6–38%) resulting in a likelihood ratio for a positive test of 7.1 (95% CI 1.7 to 29.2) for translation LSI.ConclusionThis study provides the first evidence reporting the concurrent validity of manual tests for the detection of abnormal sagittal planar motion. PAIVMs and PPIVMs are highly specific, but not sensitive, for the detection of translation LSI. Likelihood ratios resulting from positive test results were only moderate. This research indicates that manual clinical examination procedures have moderate validity for detecting segmental motion abnormality.

An Adaptive System Identification Model of the Biomechanical Response of the Human Trunk During Sudden Loading

Sudden loading injuries to the low back are a concern. Current models are limited in their ability to quantify the time-varying nature of the sudden loading event. The method of approach used six males who were subjected to sudden loads. Response data (EMG and kinematics) were input into a system identification model to yield time-varying torso stiffness estimates. The results show estimates of system stiffness in good agreement with values in the literature. The average root mean square error of the model's predictions of sagittal motion was equal to 0.1 deg. In conclusion, system identification can be implemented with minimal error and used to gain more insight into the time-dependent trunk response to sudden loads.

A Comparison of Device Measures of Dorsal First Ray Mobility

Devices built by Glasoe and Klaue have been used in several studies to measure first ray mobility. Both devices measure sagittal motion of the first ray in a dorsal direction. The primary difference in the devices is the method of the load imposed. This study investigates whether first ray mobility measured with the Glasoe device is similar to the amount of mobility measured with the Klaue device. Using the devices described by Glasoe and Klaue, dorsal first ray mobility was measured in 39 patients who had foot and ankle problems. Paired t-tests were computed to assess for differences between device measures of dorsal mobility. Intraclass correlation coefficient (ICC) and absolute difference values were computed to further assess the agreement in measures. Dorsal mobility measured with the Glasoe device averaged 4.9 mm (1.8 to 9.3 mm). Dorsal mobility measured with the Klaue device averaged 5.2 mm (2.5 to 8.5 mm). Paired t-tests (p = 0.12) revealed no significant difference in measures. An ICC of 0.70 and a mean absolute difference of 0.9 mm (SD 0.8) were found between the two clinical measures further suggesting agreement. Results indicated that the two devices possess similar diagnostic accuracy in the measurement of dorsal first ray mobility.

The repeatablity of spinal motion of normal and scoliotic adolescents during walking

The main aim of this study was to assess the within-day repeatability of measuring trunk and spinal motion during walking using external markers and a motion analysis system. A secondary aim was to compare the repeatability of motion between the scoliotic and normal spine. The sagittal and coronal plane trunk and spinal motion, three-dimensional pelvic and shoulder motion of 9 normal and 19 scoliotic adolescents was assessed. Intra-subject within-day repeatability was evaluated using waveform similarity statistics. Trunk sagittal and coronal plane motion was fairly repeatable. Repeatability of spinal frontal plane motion was fair, but that of sagittal plane motion is poor. Pelvic coronal and transverse plane motion was very reproducible but pelvic sagittal plane motion was very variable. Shoulder motion in all three planes was found to have a poor level of repeatability. A relationship possibly exists between the range of motion and repeatability values. Although the scoliotic adolescents had less variable spinal motion, differences from the normal subjects were not statistically significant. However, the scoliotic subjects had significantly more repeatable sagittal and coronal plane pelvic motion and coronal plane shoulder motion. The results of this study suggest that trunk sagittal and coronal plane motion and spinal coronal plane motion of normal and scoliotic adolescents can be reliably measured within a single test session.

Comparing precision of distortion-compensated and stereophotogrammetric Roentgen analysis when monitoring fusion in the cervical spine

Two methods to measure sagittal plane segmental motion in the cervical spine are compared. Translational and rotational motion was measured in nine cervical motion segments of nine patients by distortion-compensated (DCRA) as well as by stereophotogrammetric Roentgen analysis (RSA). To compare measurement precision of the new DCRA protocol with the established RSA technique under realistic clinical conditions and to discuss advantages and disadvantages of both methods in clinical studies. RSA constitutes the most precise method available to assess segmental motion or to monitor fusion in the cervical spine. Due to the invasive nature of the procedure there is an interest in alternative, non-invasive protocols, based on conventional, lateral radiographic views. In nine patients, segmental motion of nine cervical segments with spinal surgery and fusion had previously been assessed from stereo views by RSA. From the archive radiographs, sagittal plane segmental motion was re-assessed by DCRA. Results for sagittal plane translational and rotational motion obtained by both methods are compared. With respect to RSA, sagittal plane rotation was determined by DCRA with an error of 2.4 degrees and a mean difference not significantly different from zero. Sagittal plane translation was determined by DCRA with an error of less than 0.78 mm and a mean difference not significantly different from zero. As two methods are compared, these errors represent the combined (propagated) errors of RSA and DCRA. Averaged over the cohort investigated, measurement of sagittal plane segmental motion exhibited no significant difference between DCRA and RSA.

The Role of the Sternum, Costosternal Articulations, Intervertebral Disc, and Facets in Thoracic Sagittal Plane Biomechanics

Eighteen human torsos were used in three experiments (A, B, and C) to determine the changes in sagittal motion due to three different sequences of three surgical releases. To investigate the relative effects of releasing the intervertebral disc, the costosternal joint, the sternum, and the facet joints on sagittal thoracic motion and the consequences of altering the sequence of the releases. The biomechanics of the thoracic spine are different from the cervical and lumbar spine particularly due to the ribs and sternum, which contribute to stability and control motion. The role of the sternum and costosternal articulation in the biomechanics of thoracic sagittal motion has not been well studied. The effects of releasing each of these structures, whether alone or with discectomy and/or facetectomy, is potentially relevant in the surgical correction of thoracic deformities, such as severe kyphosis, and in the biomechanics of thoracic fracture. In Experiment A, the release sequence was back to front: total facetectomy (T4-T8), then radical discectomy (T4-T8), then costosternal release, then sternal osteotomy. In Experiment B, the release sequence was front to back: sternal osteotomy, then costosternal release, then radical discectomy, and finally total facetectomy. In Experiment C, the release sequence was: radical discectomy, then sternal osteotomy, then costosternal release, then total facetectomy. The different sequences allowed separate analysis of each component and the synergistic patterns. In each of the three experiments, the torso was flexed then extended each time by an applied force (25 N) before and after each release. The extent of flexion and the extent of extension were measured each time and compared with the intact condition, after each release. The results obtained for sternal osteotomy were combined with the results obtained for costosternal release to give "sternal release." Radical discectomy provided the greatest increase (P < 0.05) in range of motion (ROM) compared with the other two single releases, no matter what the sequence. For paired release combinations, the radical discectomy and sternal release (as in Experiments B and C) provided a significant (P < 0.05) increase in total sagittal ROM compared with the combination of radical discectomy and total facetectomy (Experiment A). In Experiment A, sternal release accounted for 42% of the total sagittal ROM compared with only 26% related to the total facetectomy (Experiment B). In general, all of the releases allowed more extension than flexion. Sagittal plane motion in the thoracic spine is influenced by all three structures tested in this experiment. Overall, the radical discectomy provides the greatest increase in total ROM and in extension compared with the other two releases. The second most influential release is the combination of sternal osteotomy plus costosternal release (i.e., sternal release), particularly in extension (correction of kyphosis). When two releases are done in sequence, radical discectomy plus sternal release provides the greatest increase in total ROM and in extension. Overall, total facetectomy is the least effective release. These data have relevance for surgical strategies in the correction of thoracic kyphosis or lordosis and suggest a potential role for sternal osteotomy and costosternal release in severe and rigid upper thoracic kyphosis.

5:05 44. Residual angular motion after simulated solid lumbar fusion—a finite element analysis with implications on interpreting flexion-extension radiographs

BACKGROUND CONTEXT: Use of flexion-extension (F-E) views is required for FDA trials of new fusion methods. Their utility is based on the presumption that solid fusion would allow little sagittal motion, while pseudarthrosis would permit a greater amount. Despite widespread use, there remains little agreement of the optimal F-E criteria, as recommendations range from 0 to 5 degrees. Though astute estimates are based on clinical experience, these values have not been derived by objective methods. In review of the literature, no experimental validation of any criteria concerning residual sagittal motion after solid lumbar fusion could be found.

P59. Assessing lumbar sagittal motion using videography in an in vivo pilot study

P59. Assessing lumbar sagittal motion using videography in an in vivo pilot study

The influence of occupation on lumbar sagittal motion and posture

The aim of this study was to determine whether sheep shearers have clinically hypothesized adaptive postural and sagittal mobility parameters of the lumbar spine and pelvis. Sixty-four shearers and 64 non-shearers, matched by age and anthropometry and surveyed for present and previous low back pain, participated in a study to determine the effects of occupation on sagittal spinal motion and posture. Lumbar and hip mobility measurements were made with a geometric CAD analysis of lateral photographs using surface reflective markers. Sagittal range of motion demonstrated similar ranges of lumbar flexion between the two groups; however, there was a marked gain in hip flexion in the shearers as well as a marked loss of lumbar extension. The shearers also demonstrated a more lordotic lower lumbar curvature compensated by a flatter (less kyphotic) mid to lower thoracic region. Shearers appear to lose lumbar extension, gain hip flexion and develop an adaptive normal stance. This adaptation appears to be independent of previous or current back pain. Conversely, lumbar extension loss in non-shearers correlates with previous back injury. A stepwise linear regression of all participants indicated that the occupation is the predominant influence on motion and posture followed by age. The implications are one of structural adaptation in this occupational group that does not appear to be correlated with back pain.

Alterations In Cycling Mechanics Resulting From Core Fatigue

Core stability has been reported to influence lower extremity alignment during functional activities. As a result of the fixed pelvis and feet in relation to the bicycle, lower extremity alignment during cycling is critical. Core fatigue may result in abnormal movement patterns and suboptimal force transmission. Limited research has described the influence of core fatigue on cycling mechanics and pedaling forces. PURPOSE To determine the influence of core fatigue on cycling mechanics and pedaling forces. METHODS Fifteen competitive cyclists (Age: 34.5 ± 9.8 years; Height: 1.77 ± 0.11 m; Mass: 76.3 ± 11.1 kg) participated. Subjects performed two incremental ramp protocols (separated by a minimum of one week) while cycling untethered on a high speed treadmill. The cycling protocol consisted of 1% increments every three minutes at 25.75 kilometers · hour−1, until exhaustion. Kinematic data were collected with a 3D motion analysis system. Pedal forces were collected with custom designed pedals integrated with a 6-degrees-of-freedom load cell. A core fatigue workout to diminish core stability was performed prior to the second test. Four sets of an eight exercise core fatigue circuit were completed as each individual exercise was performed for 40 seconds with a 20-second rest. Separate dependent t-tests were used to compare differences for joint kinematics (hip, knee, ankle, torso) and pedaling forces (effective, anterioposterior, mediolateral) between incline levels of the two tests. An a priori statistical significance was set at p < 0.05. RESULTS Total frontal plane knee motion (15.1 ± 6.0°; 23.3 ± 12.5°) increased following the core fatigue protocol. Total sagittal plane knee motion (69.9 ± 4.9°; 79.3 ± 10.1°) and ankle motion (29.0 ± 8.5°; 43.0 ± 22.9°) increased following the core fatigue protocol. No significant differences were demonstrated for the pedal force data (p > 0.05). CONCLUSIONS Core fatigue resulted in altered cycling mechanics that may increase the risk of injury as the knee joint is exposed to abnormal positioning. Improved core stability endurance may promote greater alignment of the lower extremity when riding for extended time periods as the core is more resistant to fatigue.

The Pisotriquetral Joint: Anatomic, Biomechanical, and Radiographic Analysis

To examine anatomically and radiographically the ligaments stabilizing the pisotriquetral (PT) joint and to determine the contribution of each ligament to the stability of this joint. Twelve cadaver arms were used. The study had 3 components: (1) anatomic dissection of the PT joint ligaments and patterns of degenerative changes, (2) biomechanical sequential sectioning of the supporting ligaments, and (3) radiographic assessment of PT joint motion in several planes both before and after ligament sectioning. The ligaments that attached to the pisiform were the pisometacarpal (PM), pisohamate (PH), radial PT, ulnar PT, and transverse carpal ligament. The PH ligament was shorter, wider, and thicker than the PM ligament. The transverse carpal ligament attachment in the pisiform was insubstantial. In 10 limbs degenerative changes were present, most of them peripheral. Biomechanical testing showed that the primary stabilizers of the PT joint were the PM, PH, and ulnar PT ligaments and that these were responsible for resisting proximal, ulnar, and radial forces, respectively. The PH distance increased along with the pisiform sagittal motion during wrist flexion on oblique x-rays after transection of the PM and ulnar PT ligaments. Concomitantly this distance decreased on the anteroposterior x-rays during radial deviation. The PH distance increased along with the pisiform frontal motion after transection of the PH and radial PT ligaments. The pisiform ligament complex has primary and secondary stabilizers to the PT joint. The primary stabilizers are the PH, PM, and ulnar PT ligaments. The transverse carpal and radial PT ligaments are secondary stabilizers. Injuries of the primary stabilizers of the PT joint may lead to instability that predisposes to degenerative joint disease.