Koichi Shinkoda

Contribution of knee adduction moment impulse to pain and disability in Japanese women with medial knee osteoarthritis.

BACKGROUND An increase in the knee adduction moment is one of the risk factors of medial knee osteoarthritis. This study examined the relationship between knee adduction moment and self-reported pain and disability. We also investigated the influence of pain on the relationships between knee adduction moment and gait performance and disability. METHODS Thirty-eight Japanese women with medial knee osteoarthritis participated in this study (66.37 years (41-79 years)). Gait analysis involved the measurement of the external knee adduction moment impulse in the stance duration and during 3 subdivisions of stance. The total, pain and stiffness, and physical function Japanese Knee Osteoarthritis Measure scores were determined. FINDINGS The pain and stiffness, physical function, and total scores were positively correlated with the knee adduction moment impulses in the stance duration, and initial and second double support interval, and single limb support interval. The knee adduction moment impulse during the stance duration was related to the pain and stiffness subscale and gait velocity. The pain and stiffness subscale was related to the physical function subscale. INTERPRETATION Our results suggest that increasing in the knee adduction moment impulse, a proxy for loading on the medial compartment of the knee, is related to increased pain during weight-bearing activities such as walking, thereby restricting walking performance and causing disability by reducing gait velocity. Thus, the reduction in the knee adduction moment impulse during gait may result in pain relief and may serve as a conservative treatment option with disease-modifying potential.

Total surface bearing below-knee prosthesis: Advantages disadvantages and clinical implications

OBJECTIVE To investigate the total surface bearing (TSB) prosthesis for below-knee amputee patients and to determine its clinical indications. DESIGN Case series. SETTING University hospital and the Welfare Center for the Disabled. PATIENTS Thirty-two subjects who could walk with the TSB prosthesis and had already used the patellar-tendon bearing (or Kondylen-Bettung Münster) socket. MAIN OUTCOME MEASURE Subjective assessment of the TSB socket, consisting of an overall rating and ratings of 13 individual items, was performed, and results were analyzed with Fishers exact test. RESULTS Seventy-five percent of the subjects were satisfied overall with the TSB socket. Of the 13 items, comfort, ease to swing, pain, piston movement, tightness, skin irritation, appearance, and durability were regarded as good by more than 75% of the patients. Donning, perspiration, odor, and staining were regarded as poor by more than 20%. Items that were significantly related with overall satisfaction with the TSB socket were comfort, ease to swing, and piston movement, while donning was significantly related to dissatisfaction. CONCLUSION The TSB socket is suitable for and preferred by many amputee subjects, but some problems remain to be solved.

Do patients with knee osteoarthritis perform sit-to-stand motion efficiently?

The sit-to-stand motion (STS) is a frequently executed activity that is affected by weakness in the quadriceps femoris muscle and knee joint pain in patients with knee osteoarthritis (OA). We investigated whether patients with knee OA can efficiently perform STS through mechanical energy transfer assessments. Participants were 20 women with knee OA and 17 age-matched asymptomatic controls. The center of mass (COM), segment angles, joint moments, and powers during STS were measured. The negative mechanical work in the proximal portion of the shank, negative mean powers in the distal portion of the pelvis and proximal portion of the shank, and the positive mean power in the proximal and distal portions of the thigh were significantly lower in the knee OA group than in the control group. Patients with knee OA primarily performed thoracic forward lean movement, shifting their COM closer to the base of support provided by the feet alone, in an attempt to achieve stability at and after buttocks-off. However, control ability, which generates and absorbs kinetic energy quickly, was not enhanced in these patients, and their motion was unable to increase absorption of the mechanical energy in hip extensors and reduce the load on knee extensors. Furthermore, STS in patients with knee OA had reduced energy absorption in the knee extensors from the shank forward lean movement after buttocks-off, had reduced knee extensor efficiency, and made greater use of physiological energy. These findings suggest that, from the standpoint of mechanical energy transfer, patients with knee OA do not perform STS efficiently.

The influence of the distance between the backrest of a chair and the position of the pelvis on the maximum pressure on the ischium and estimated shear force

Purpose. For some people with leg disorders, the alternative to becoming bedridden is sitting in a wheelchair for long periods of time. The purpose of this study was to investigate the relation between the backrest of a chair and the position of the pelvis on the maximum pressure at the ischium and the estimated shear force encountered while sitting in a chair. Methods. Ten healthy males aged 22.4 ± 2.3 years without pathologies in the leg and/or trunk participated in this study. The subjects were instructed to sit in a chair and the pressure and shear forces were measured under three sitting conditions: In the standard position, a 5 cm forward position and a 10 cm forward position. The effects of the positions of the pelvis on the maximum pressure at the ischium were measured by an instrument for measuring pressure distribution and the shear forces were estimated using an experimental model proposed by us. Results. Comparisons were made among the three sitting positions; the range of displacement of the maximum pressure point was not significant. The estimated shear force on the seat was 15.5 ± 12.4 N in the standard position, 34.4 ± 8.5 N in the 5-cm forward position, and 53.2 ± 16.7 N in the 10 cm forward position. There were significant differences among the three values (p < 0.01). Conclusions. Displacing the pelvis forward and leaning against the backrest tends to increase the shear force and raise the risk of decubitus ulcers.

Biomechanics of rising from a chair and walking in pregnant women.

The present study aimed to assess the changes in the pattern of rising from a chair and walking forward as pregnancy progressed. Twelve pregnant women and 10 nulliparous women were included in this study. Participants were videotaped with a digital video camera in the sagittal plane, and the coordinates of the markers attached to the subjects were identified using image analysis software. The peak trunk-flexion angle in pregnant women during rising was smaller, but the hip-extension angle during the stance phase was larger than in controls. Also, the peak horizontal and vertical velocities of the center of mass were lower, and appeared earlier, in pregnant women than in controls. During rising, pregnant women dampened the propulsion attributable to increased uterus volume, and they enhanced the forward propulsion at gait initiation. To ensure safe motion, pregnant women should not initiate gait until reaching a stable standing position after rising.

Foot alignments influence the effect of knee adduction moment with lateral wedge insoles during gait.

Lateral wedge insoles (LWIs) reduce the peak external knee adduction moment (KAM). However, the efficacy of LWIs is limited in certain individuals for whom they fail to decrease KAM. Possible explanations for a lack of desired LWI response are variations in foot alignments. The purpose of this study was to evaluate whether the immediate biomechanical effects of LWIs depend on individual foot alignments during gait. Fifteen healthy adults participated in this study. Their feet were categorized as normal, pronated, and supinated using the foot posture index. All subjects were subsequently requested to perform a normal gait under barefoot and LWI conditions. A three-dimensional motion analysis system was used to record the kinematic and kinetic data, included peak KAM, KAM impulse (KAAI), center of pressure displacement, and knee-ground reaction force lever arm (KLA). Furthermore, lower limb frontal plane kinematic parameters at the rear foot, ankle, knee, and hip were evaluated. Among all feet, there was no significant difference in the peak KAM and KAAI between the conditions. In contrast, the peak KAM was significantly reduced under the LWI condition relative to the barefoot condition in the normal foot group. Reductions in the peak KAM were correlated with a more lateral center of pressure and reduced KLA. In addition, a reduced KLA was correlated with decreased hip adduction. LWIs significantly reduced the peak KAM in normal feet, indicating that biomechanical effects of LWIs vary between individual foot alignments. Our findings suggest that it is helpful to assess individual foot alignment to ensure adequate insole treatment for patients with knee osteoarthritis.

Investigation of validity of model for estimating shear force applied to buttocks in elderly people with kyphosis while sitting comfortably on a chair

Purpose. The purpose of the present study was to investigate the validity of a model for estimating shear force on the buttocks of elderly people with kyphosis. Method. The subjects with kyphosis were 10 elderly people in a facility providing health care services for the elderly. The shear force was measured using a force plate and, simultaneously, the position of the resultant centre of mass of the upper body and the inclination angle of the trunk were measured. The estimated shear force was calculated by substituting these values in the model. Results. The average value of the measured shear force was 8.4 SD 1.4 [%BW], and the average value of the estimated shear force was 5.8 SD 1.0 [%BW]. Although there was a significant difference between these two values (p < 0.01), there was a strong positive correlation between them (r = 0.786, p < 0.01). The regression line between the two values was y = 1.097x + 1.96, where x = estimated value, y = measured value. Conclusions. These results suggest that the estimated shear force was close to the measured shear force and thus is approximately known by substituting the calculated values for the linear regression.

Properties of the flexible pressure sensor under laboratory conditions simulating the internal environment of the total surface bearing socket.

The purpose of this study was to investigate the properties of the flexible pressure sensor under laboratory conditions simulating the internal environment of the total surface bearing (TSB) socket to determine optimal conditions for measuring normal stresses on the stump. The equipment used in the study was the Pressure Distribution Sensor System for Sockets. In a climatic chamber maintained at 37d`C and 70% humidity the sensor sheet was mounted on a measuring apparatus loaded with three 10 kg weights, and output from the sensor was records after loading was adopted as the measured output. Output was greater when weight was decreased than when weight was increased because of hysteresis (paired t-test, p<0.05). The sensor had temperature sensitivity but differences in output were not statistically significant (paired t-test, 0.10>p>0.05). There were no significant differences in output among five sensor sheets or among five sections of four sensor sheets (two-way ANOVA, p>0.05), but repeated loading on the same section of the sensor sheet increased output (two-way ANOVA, p<0.05). Reproducibility and sensitivity distribution of the sensor are considered satisfatory under laboratory conditions, but measurements of rapid and repetitive movements may not be accurate and comparing subtle changes in output from a single sensor is not suitable. The reliability of the sensor in a clinical setting for measuring normal stresses on the stump with the TSB socket should be examined.

Biomechanical effects of lateral and medial wedge insoles on unilateral weight bearing

[Purpose] Lateral wedge insoles reduce the peak external knee adduction moment and are advocated for patients with knee osteoarthritis. However, some patients demonstrate adverse biomechanical effects with treatment. In this study, we examined the immediate effects of lateral and medial wedge insoles under unilateral weight bearing. [Subjects and Methods] Thirty healthy young adults participated in this study. The subjects were assessed by using the foot posture index, and were divided into three groups: normal foot, pronated foot, and supinated foot groups. The knee adduction moment and knee-ground reaction force lever arm under the studied conditions were measured by using a three-dimensional motion capture system and force plates. [Results] In the normal and pronated groups, the change in knee adduction moment significantly decreased under the lateral wedge insole condition compared with the medial wedge insole condition. In the normal group, the change in the knee-ground reaction force lever arm also significantly decreased under the lateral wedge insole condition than under the medial wedge insole condition. [Conclusion] Lateral wedge insoles significantly reduced the knee adduction moment and knee-ground reaction force lever arm during unilateral weight bearing in subjects with normal feet, and the biomechanical effects varied according to individual foot alignment.

Estimation of inertial parameters of the lower trunk in pregnant Japanese women: A longitudinal comparative study and application to motion analysis.

We aimed to quantify the inertial parameters of the lower trunk segment in pregnant Japanese women and compare kinetic data during tasks calculated with parameters estimated in this study to data calculated with standard parameters. Eight pregnant women and seven nulliparous women participated. Twenty-four infrared reflective markers were attached to the lower trunk, and the standing position was captured by eight infrared cameras. The lower trunk was divided into parts, and inertial parameters were calculated. Pregnant women performed a movement task that involved standing from a chair, picking up plates, and walking forward after turning to the right. Kinetic analysis was performed using standard inertial parameters and the newly calculated parameters. There were more significant differences between methods in the kinetic data at the latter stages of pregnancy. The inertial parameters calculated in this study should be used to ensure the validity of biomechanical studies of pregnant Japanese women.