Evaluating the Function of the Foot Core System in the Elderly

The protocol proposes a comprehensive evaluation for the function of the foot core system, and it may provide increased awareness to explore the foot function among different populations. This study was aimed to evaluate the foot function from the perspective of three core subsystems of a human foot with particular attention to active components. The protocol might provide new insights into evaluation and treatment effects for the foot and ankle dysfunctions, such as flatfoot and chronic ankle instability.

Demonstrating the procedure will be Li Xu and Kun Dong, master students from Dr.Wang's laboratory. Begin evaluating the muscle morphology by turning on the musculoskeletal ultrasound system. Then click on the freeze button, and plug the sound head connector into the connection port on the rear side of the host before selecting the pro block option.

Click on the I station button and select the new patient tab to input the ID, name, gender, and date of birth of the participant. To image the abductor hallucis muscle, apply the ultrasound coupling gel to the participant at the middle of the scanning line of tuberosity and navicular tuberosity, and place the probe at the medial calcaneal tuberosity toward the navicular tuberosity. Move the probe slightly to capture the thickest part of the abductor hallucis, and click on the save button to save the still image.

Then rotate the probe 90 degrees to obtain the cross-sectional image of the muscle and save the image. For the flexor digitorum brevis muscle, line up the probe longitudinally on the line from the medial tubercle of the calcaneus to the third toe, and scan the muscle to measure the thickness. Rotate the probe 90 degrees to obtain the cross-sectional image.

Record the longitudinal and cross-sectional images of the quadratus plantae and flexor hallucis brevis muscle as described in the manuscript. Next, spot the fibular head and the inferior border of the lateral malleolus, along with 50%of the line connecting the two points. After applying the coupling gel, place the probe to record the thickness and the cross-sectional image of peroneus longus and brevis or BER.

Obtain the thickness of the tibialis anterior muscle as mentioned in the manuscript. Insert a dynamometer Bluetooth stick into the USB interface of the computer, followed by opening the dynamometer and FET data collection software. Click on the start gauge button and wait for automatic pairing To test toe flexion strength, instruct the participant to sit in a chair with 90 degree flexion of the knee and ankle joint.

Fix the dynamometer to the front side of the wooden frame and connect the great toe to the dynamometer by a carabiner. When done, interchange the panels behind the foot to ensure that the heel to the head of the first metatarsal is supported while allowing for unimpaired toe flexion. Then adjust the carabiner so that the toe produces a steady baseline force and click on the reset button to zero out the dynamometer.

In the software, select the start gauge option. Then give the instructions to the participant to remain stable until asked to flex the big toe. Then pull as hard as possible for three seconds and relax the grip.

Once done, click on the stop gauge button and save the data collected. Later, attach the T-shaped metal bars to the dynamometer and instruct the participant to flex the second to the third toe or second to the fifth toe to perform the toe flexion strength test as explained before. For the doming test, place the dynamometer against the scaphoid tubercle.

Then ask the participant to slide the forefoot toward the heel or raise the arch as much as possible without lifting or curling the toes, and do maximum voluntary contraction for three seconds and collect data as the toe flexion tests. Assemble the height vernier caliper as explained in the manuscript to carry out the navicular drop or ND test. Once the participant is rested on a height adjustable chair, turning sideways to view the medial longitudinal arch, palpate the navicular tuberosity and mark its location.

After asking the participant to sit in a position to make a 90 degree angle between the knee, hip, and ankle joints, palpate the medial and lateral aspects of the participant's talus head, then supinate and pronate the subtalar joint until the medial and lateral sides of the talus are equally positioned. Align the head of the scribing claw with the marked navicular tuberosity to record the height at the same non-weightbearing position. Instruct the participant to stand and keep the regular bilateral weight-bearing stance to record the height.

Instruct the participants to take several steps, march on the spot, and then stand in their relaxed stance position with double limb support. Palpate the talar head, followed by rating the head's position on the lateral and medial sides. Similarly, palpate the lateral malleolar to score the supra in infra lateral malleolar curvature.

Next, record the angle between the posterior aspect of the calcaneus and the long axis of the foot. Rate the bulge or concave in the talar navicular joint area and the height and congruence of the medial longitudinal arch. Score the relative position of the forefoot on the rear foot by observing the forefoot directly behind and in line with the long axis of the heel.

To study the planter light touch threshold, prepare a Semmes-Weinstein monofilament kit or SWM consisting of 20 pieces. Then mark the test regions in the planter sole, including the first toe, first metatarsal head, third metatarsal head, fifth metatarsal head, midfoot, and heel. At the target region, apply the SWM perpendicularly to the skin.

Apply pressure until the nylon SWM is bent to form a C shape. Then hold the SWM for one second before removal. After preparing the two point discriminator device for the two point discriminator test, start the test from the distance of eight millimeters, and then decrease the width distance by five millimeters until the participants report one point.

Later, move the device in one millimeter increments, applying randomization of one or two points until the participants can consistently identify two points at a test width. The muscle strength data showed that the foot muscle strengths were lower in the elderly for all tests compared with the young participants. As for the muscle morphology, there were significant thickness differences in most muscles except the tibialis anterior between the two groups.

Moreover, significant differences were observed in the cross-sectional area between the two groups. For the passive subsystem, the ND distance and FPI-6 scores were higher in the elderly than the young participants. The neural subsystem results showed that the planter light touch thresholds in the two point discriminator of six regions were higher in the elderly participants.

During the doming test, the tester must observe to check if the participant's toes are lifted or curled. The two testers are recommended, one to evaluate actions and one to collect data.