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Biomechanical measures may identify patients with OA who can benefit from lateral wedge insoles
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The coronal plane and subtalar joint complex biomechanical measures affect the way lateral wedge insoles benefit or harm a patient, and the assessing the angle of the ankle at peak external knee adduction moment and peak eversion angle helped predict which patients with osteoarthritis would benefit from lateral wedge insoles, according to recently published research.
Researchers studied 70 participants between the ages of 40 and 85 years who reported at least mild knee pain when walking on a flat surface and met Kellgren Lawrence criteria for osteoarthritis (OA). Patients were given a lateral wedge insole for the affected knee and participated in tests to compare the results.
To measure lower-limb kinetics and kinematics, patients participated in a 3-D gait analysis with a 16-camera motion-analysis system collected at 100 Hz and fitted over four embedded force plates, which collected at 200 Hz. Patients were blinded to the awareness of the force plates to avoid targeting.
Reflective markers were placed over the first and fifth metatarsal heads. The center of ankle and knee joints were calculated as midpoints between the malleoli and femoral epicondyles, and regression modeling was used to calculate the hip joint center according to the anterior and posterior superior iliac spine markers.
Calculations of joint kinematics were made using Visual 3D (C-Motion) by employing an X-Y-Z Euler rotation sequence. Joint kinetic data was assessed using 3-D inverse dynamics. External knee adduction moment (EKAM) was normalized to the participant’s mass, and knee adduction angular impulse (KAAI) was normalized to mass and time. The position of the center of force pressure (COFP) with respect to the foot, the ankle angle and external ankle eversion moment were used to calculate the related coronal plane biomechanical measures. The known location of the shoe on the force plate was used to calculate COFP.
The distance of the center of force in relation to the midline of the foot was used to calculate the mediolateral COFP, and peak EKAM during early stance and knee adduction angular impulse (KAAI) were calculated using a custom Matlab program.
The difference in coronal plane biomechanical variables between the control shoe and the shoe fitted with a lateral wedge insole were compared. An immediate and significant decrease in peak EKAM (5.85%) and KAAI (7.95%) was observed overall, but 33% of patients experienced an increase in peak EKAM with the intervention. Peak EKAM in these participants was 0.028 Nm/kg, an increase of 8.15% compared with the control shoe. Mean reduction in peak EKAM in the other 67% participants was 11.39% compared with the control shoe, according to the researchers.
A more everted position in the ankle and subtalar joint complex was caused by the lateral wedge insole, and a lateral shift in COFP at peak EKAM was observed. At peak EKAM, ankle eversion moment was greater. Peak angle eversion moment was also greater with the lateral wedge insole compared with the control shoe.
Further analysis showed that a higher peak eversion angle or a higher ankle angle at peak EKAM under control conditions were associated with a positive response to the lateral wedge insole. No differences were found by gender, according to the researchers. - by Shirley Pulawski
Disclosures: Chapman reports no relevant financial disclosures. Please see the full study for a list of all other authors’ relevant financial disclosures.
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