Shih-Wun Hong

Symmetrical kinematic changes in highly functioning older patients post-stroke during obstacle-crossing

With the advances in stroke care, the number of high-functioning patients after stroke is increasing. However, existing clinical tools may not be sensitive enough to identify the residual deficits in these patients. The current study aimed to investigate the control of the pelvis, and the joints and end-point of the lower limbs in high-functioning older patients post-stroke during obstacle-crossing using motion analysis techniques. Twenty-four high-functioning older patients following unilateral stroke and fifteen healthy controls walked and crossed obstacles of three different heights. End-point variables (leading toe-clearance and trailing toe-obstacle distance) and crossing pelvic and joint angles were obtained for both limbs during leading limb crossing. Whether leading with the contralesional or ipsilesional limb, the stroke group exhibited significantly different joint kinematics from the controls mainly in the frontal and transverse planes, with greater leading toe-clearance, trailing toe-obstacle distance, and posterior pelvic tilt. None of the end-point and joint variables were significantly different between limbs. High-functioning patients post-stroke appeared to have acquired a specific symmetric kinematic strategy with increased leading toe-clearance during obstacle-crossing, most likely in order to prevent tripping. This symmetric strategy, possibly a consequence of brain reorganization, may help in performing functional activities during which symmetric performance between the contralesional and ipsilesional sides is required. Obstacle-crossing training with both limbs leading alternately may be helpful for the development of this symmetric strategy. It is suggested that computerized motion analysis of obstacle-crossing can be a sensitive assessment tool for distinguishing the motor performance between normal and high-functioning patients post-stroke.

Leg and Joint Stiffness in Children with Spastic Diplegic Cerebral Palsy during Level Walking

Individual joint deviations are often identified in the analysis of cerebral palsy (CP) gait. However, knowledge is limited as to how these deviations affect the control of the locomotor system as a whole when striving to meet the demands of walking. The current study aimed to bridge the gap by describing the control of the locomotor system in children with diplegic CP in terms of their leg stiffness, both skeletal and muscular components, and associated joint stiffness during gait. Twelve children with spastic diplegia CP and 12 healthy controls walked at a self-selected pace in a gait laboratory while their kinematic and forceplate data were measured and analyzed during loading response, mid-stance, terminal stance and pre-swing. For calculating the leg stiffness, each of the lower limbs was modeled as a non-linear spring, connecting the hip joint center and the corresponding center of pressure, with varying stiffness that was calculated as the slope (gradient) of the axial force vs. the deformation curve. The leg stiffness was further decomposed into skeletal and muscular components considering the alignment of the lower limb. The ankle, knee and hip of the limb were modeled as revolute joints with torsional springs whose stiffness was calculated as the slope of the moment vs. the angle curve of the joint. Independent t-tests were performed for between-group comparisons of all the variables. The CP group significantly decreased the leg stiffness but increased the joint stiffness during stance phase, except during terminal stance where the leg stiffness was increased. They appeared to rely more on muscular contributions to achieve the required leg stiffness, increasing the muscular demands in maintaining the body posture against collapse. Leg stiffness plays a critical role in modulating the kinematics and kinetics of the locomotor system during gait in the diplegic CP.

A method for measuring three-dimensional mandibular kinematics in vivo using single-plane fluoroscopy

OBJECTIVES Accurate measurement of the three-dimensional (3D) motion of the mandible in vivo is essential for relevant clinical applications. Existing techniques are either of limited accuracy or require the use of transoral devices that interfere with jaw movements. This study aimed to develop further an existing method for measuring 3D, in vivo mandibular kinematics using single-plane fluoroscopy; to determine the accuracy of the method; and to demonstrate its clinical applicability via measurements on a healthy subject during opening/closing and chewing movements. METHODS The proposed method was based on the registration of single-plane fluoroscopy images and 3D low-radiation cone beam CT data. It was validated using roentgen single-plane photogrammetric analysis at static positions and during opening/closing and chewing movements. RESULTS The method was found to have measurement errors of 0.1 ± 0.9 mm for all translations and 0.2° ± 0.6° for all rotations in static conditions, and of 1.0 ± 1.4 mm for all translations and 0.2° ± 0.7° for all rotations in dynamic conditions. CONCLUSIONS The proposed method is considered an accurate method for quantifying the 3D mandibular motion in vivo. Without relying on transoral devices, the method has advantages over existing methods, especially in the assessment of patients with missing or unstable teeth, making it useful for the research and clinical assessment of the temporomandibular joint and chewing function.

Effects of bilateral medial knee osteoarthritis on intra- and inter-limb contributions to body support during gait.

Patients with knee OA show altered gait patterns, affecting their quality of living. The current study aimed to quantify the effects of bilateral knee OA on the intra-limb and inter-limb sharing of the support of the body during gait. Fifteen patients with mild, 15 with severe bilateral knee OA, and 15 healthy controls walked along a walkway while the kinematic and kinetic data were measured. Compared with the controls, the patients significantly reduced their knee extensor moments and the corresponding contributions to the total support moment in the sagittal plane (p<0.05). For compensation, the mild OA group significantly increased the hip extensor moments (p<0.05) to maintain close-to-normal support and a more symmetrical inter-limb load-sharing during double-limb support. The severe OA group involved compensatory actions of both the ankle and hip, but did not succeed in maintaining a normal sagittal total support moment during late stance, nor a symmetrical inter-limb load-sharing during double-limb support. In the frontal plane, the knee abductor moments and the corresponding contributions to the total support moment were not affected by the changes in the other joints, regardless of the severity of the disease. The observed compensatory changes suggest that strengthening of weak hip muscles is essential for body support during gait in patients with knee OA, but that training of weak ankle muscles may also be needed for patients with severe knee OA.

KINEMATIC AND KINETIC ADAPTATIONS IN THE LOWER EXTREMITIES OF EXPERIENCED WEARERS DURING HIGH-HEELED GAIT

High-heeled shoes are associated with falling, leading to injuries such as fracture and ankle sprain. The study aimed to investigate the kinematic and kinetic adaptations in the lower extremities resulting from habitual use of high-heeled shoes. A total of 15 female experienced wearers and 15 matched controls walked with high-heeled shoes (7.3 cm) while kinematic and ground reaction force data were measured and used to calculate the joint angles and moments, as well as the temporal-distance parameters. Compared with inexperienced wearers, experienced wearers appeared to adopt a specific control strategy to improve the stability of the support ankle and knee while preventing excessive loading at the knee and hip. Increased hip abduction during early stance phase and increased pelvis rotation toward the ipsilateral side at contralateral heel-strike appeared to contribute toward the reduced step width for a better adjustment of the medio-lateral motion of the bodys center of mass in order to maintain stability. At the hip, increased abductor moments may help to increase the pelvis stability and prevent excessive loading at the knee, and reduced internal rotator moments may reduce the torsional loading at the hip. At the knee, reduced ranges of flexion-extension and adduction-abduction motions may increase its stability. At the ankle, increased external rotation angles, together with increased pronator and external rotator moments through increased ground reaction force, may enhance the ankle stability. The current results identified the changes in the kinematics and kinetics of the lower extremities in females after long-term use of high-heeled shoes, providing a basis for future development of training programs and design of new high-heeled shoes to help those who have higher risks of falling and injuries during high-heeled gait.

TRUNK FLEXION STRATEGY AND THE LOADS IN THE LOWER LIMBS WHEN WALKING UP SURFACES OF DIFFERENT SLOPES

Walking inclined ground surfaces presents a number of challenges to the human locomotor system, especially for those with neuromusculoskeletal injuries or diseases. The purpose of the current study was to perform a complete 3D kinetics analysis of the locomotor system during uphill walking on surfaces of di®erent inclinations in order to reveal interactions of the joints and the trunk motion, and the related mechanical demands for future clinical applications. Fifteen young adults were asked to walk on inclined sloped walkways with 0, 5, 10, 15 degrees of slopes while kinematic and kinetic data were collected and analyzed. The results showed that the subjects increased the anterior tilt of the pelvis and the °exion of the trunk with increased inclination angles, maintaining more or less constant moments at the ankle,

BALANCE CONTROL DURING LEVEL WALKING IN CHILDREN WITH SPASTIC DIPLEGIC CEREBRAL PALSY

Children with cerebral palsy (CP) have been reported to have various levels of deficits in balance control, which can be described using the relationship between the bodys centre of mass (COM) and the centre of pressure (COP). This study aimed to investigate the balance control of children with spastic diplegic CP during level walking. The COM-COP inclination angles and angular velocities, as well as temporal-spatial variables from 12 children with spastic diplegic CP (seven girls and five boys, aged 12.4 ± 4.4 years) and 12 normal controls (eight girls and four boys, aged 11.2 ± 4.4 years) were obtained using a motion analysis system and two forceplates. With compromised balance control as a result of neuromusculoskeletal pathologies, the CP group walked with reduced walking speed and stride length (p < 0.05), but increased stride time and step width (p < 0.05), indicating reduced gait efficiency. They also showed significantly reduced anterioposterior COM-COP inclination angles and angular velocities (p < 0.05), but increased mediolateral COM-COP inclination angles and angular velocities (p < 0.05) when compared to the normal controls. The latter phenomenon may be related to an increased risk of falling in these patients. Therefore, it appears that programs and/or devices for preventing falls are needed for children with spastic diplegic CP.

Loading rates during walking in adolescents with type II osteonecrosis secondary to pelvic osteotomy.

Although Pemberton osteotomy has shown a high success rate even in older children, the occurrence of osteonecrosis (ON) remains one of the most severe complications, leading to premature osteoarthritis. Patients with type II ON are characterized by a valgus deformity of the proximal femur with altered musculoskeletal conditions, affecting the ability to attenuate or sustain the impulsive loading from the ground reaction force. It remains unclear whether these conditions also predispose these patients to harmful impulsive loadings. This study aimed to bridge the gap by measuring the loading rates in the lower limbs during level walking in adolescents who were treated during their infancy for unilateral developmental dysplasia of the hip by a pelvic osteotomy, with or without having developed type II ON. Patients with type II ON were found to display increased loading rates, not only at both the affected and unaffected hip, but also at other joints of the affected limb during level walking when compared to patients without ON changes (p < 0.05). These results suggest that patients with type II ON may be at a higher risk of developing premature hip osteoarthritis that is closely related to abnormal loading rates during gait. It is suggested that regular monitoring of joint loading rates in patients with type II ON is necessary for early identification of damaging loadings, and that early intervention aimed at reducing these loadings should be considered.

BIOMECHANICAL STRATEGIES AND THE LOADS IN THE LOWER LIMBS DURING DOWNHILL WALKING WITH DIFFERENT INCLINATION ANGLES

Downhill walking places greater demands on the lower limb joints with a greater risk of falling when compared with level walking. The current study aimed to quantify the 3D joint kinematics and kinetics of the locomotor system, and their interactions with the trunk during downhill walking. Fifteen young adults walked at a self-selected pace on a 3-m walkway with slopes of 0°, 5°, 10°, and 15° while their kinematic and kinetic data were measured. A complete 3D biomechanical analysis of the locomotor system was performed on these data. The results showed that with increasing downhill angles young healthy adults increased the posterior tilt of the pelvis and lateral trunk bending towards the stance limb, as well as the peak dorsiflexor and extensor moments at the ankle and knee, respectively, during the first half of the stance phase (SP), and increased the peak moments at the hip during the second half of the SP. The associated joint forces also varied with increasing slopes over the SP. When the overall mechanical demands were considered over the SP, the angular extensor and plantarflexor impulses at the knee and ankle were found to increase linearly with increasing slopes. The current results may serve as baseline data for future studies on downhill walking, and for clinical applications in various patient groups.

INFLUENCE OF LONG-TERM TAI-CHI CHUAN TRAINING ON STANDING BALANCE IN THE ELDERLY

Tai-Chi Chuan (TCC) is thought to be a low-impact and effective exercise to improve balance capability in the elderly. However, the effects of TCC exercise on balance improvement remain controversial. The purpose of the current study was to investigate the effects of long-term Yang-Style TCC training on balance variables such as stable standing time and center of pressure (COP) movement patterns. Fifteen long-term Yang-Style TCC practitioners and fifteen age-matched adults performed different static balance tests each for 30 seconds. For each test, the time-varying COP positions were measured by two forceplates. The sway area of the COP was described by an equivalent ellipse, the two principal axes of which were obtained by using principal component analysis. The results showed that elderly subjects with long-term Yang-Style TCC training were able to maintain stable standing longer than those without TCC training, with reduced COP sway area during challenging tasks such as single-leg stance and tandem stance. It is suggested that long-term TCC exercise is a good choice in a training program aimed at reducing the risk of falling in the elderly.