Associations Between the Size of Individual Plantar Intrinsic and Extrinsic Foot Muscles and Toe Flexor Strength

Background The size of the plantar intrinsic and extrinsic foot muscles has been shown to be associated with toe flexor strength (TFS). Previous studies adopted the size of a limited plantar intrinsic foot muscle or a compartment containing several muscles as an independent variable for TFS. Among the plantar intrinsic and extrinsic foot muscles, therefore, it is unclear which muscle(s) primarily contributes to TFS development. The present study aimed to clarify this subject. Methods In 17 young adult men, a series of anatomical cross-sectional area of individual plantar intrinsic and extrinsic foot muscles was obtained along the foot length and the lower leg length, respectively, using the magnetic resonance imaging. Maximal anatomical cross-sectional area (ACSAmax) and muscle volume (MV) for each constituent muscle of the plantar intrinsic foot muscles (flexor hallucis brevis; flexor digitorum brevis, FDB; abductor hallucis; adductor hallucis oblique head, ADDH-OH; adductor hallucis transverse head, ADDH-TH; abductor digiti minimi; quadratus plantae) and extrinsic foot muscles (flexor hallucis longus; flexor digitorum longus) were measured. TFS was measured with a toe grip dynamometry. Results TFS was significantly associated with the ACSAmax for each of the ADDH-OH (r = 0.674, p = 0.003), ADDH-TH (r = 0.523, p = 0.031), and FDB (r = 0.492, p = 0.045), and the MV of the ADDH-OH (r = 0.582, p = 0.014). As for the ADDH-OH, the correlation coefficient with TFS was not statistically different between ACSAmax and MV (p = 0.189). Stepwise regression analysis indicated that ACSAmax and MV of the ADDH-OH alone explained 42% and 29%, respectively, of the variance in TFS. Conclusion The ADDH-OH is the key muscle that primarily contributes to TFS development among the plantar intrinsic and extrinsic foot muscles.

Effect of Peroneus Longus Muscle Release on Abductor Hallucis Muscle Activity and Medial Longitudinal Arch before Toe-Tap Exercise in Participants with Flexible Pes Planus

Pes planus is a medical condition of the foot wherein there is a flattening or lowering of the medial longitudinal arch. The abductor hallucis muscle starts at the heel bone and attaches to the medial side of the first toe. Whenever it contracts, it plays a key role in elevating the medial longitudinal arch. Hence, the abductor hallucis muscle should be strong enough to control the depression on the medial longitudinal arch. The peroneus longus muscle plantarflexes the ankle and everts the ankle and subtalar joint. If this muscle contracts more than the abductor hallucis muscle does, the medial longitudinal arch of the foot is depressed. This study aimed to investigate the effect of myofascial release of the peroneus longus before performing the toe-tap exercise for strengthening the abductor hallucis muscle in participants with flexible pes planus. This cross-over study included 16 volunteers with flexible pes planus. The participants performed a toe-tap exercise before and after the myofascial release of the peroneus longus. During the toe-tap exercise, the muscle activity of the abductor hallucis and peroneus longus were measured using a Delsys Trigno Wireless Electromyography System. The angle of the medial longitudinal arch was measured using Image J software. Photos in the sagittal plane were used. The peroneus longus activity and medial longitudinal arch angles were significantly decreased. On the other hand, the activity of the abductor hallucis significantly increased after the myofascial release of the peroneus longus before performing the toe-tap exercise (p < 0.05). Individuals with flexible pes planus should be encouraged to perform myofascial release of the peroneus longus before the toe-tap exercise to improve the abductor hallucis activity and to elevate the medial longitudinal arch.

Stiffening the human foot with a biomimetic exotendon

Shoes are generally designed protect the feet against repetitive collisions with the ground, often using thick viscoelastic midsoles to add in-series compliance under the human. Recent footwear design developments have shown that this approach may also produce metabolic energy savings. Here we test an alternative approach to modify the foot–ground interface by adding additional stiffness in parallel to the plantar aponeurosis, targeting the windlass mechanism. Stiffening the windlass mechanism by about 9% led to decreases in peak activation of the ankle plantarflexors soleus (~ 5%, p < 0.001) and medial gastrocnemius (~ 4%, p < 0.001), as well as a ~ 6% decrease in positive ankle work (p < 0.001) during fixed-frequency bilateral hopping (2.33 Hz). These results suggest that stiffening the foot may reduce cost in dynamic tasks primarily by reducing the effort required to plantarflex the ankle, since peak activation of the intrinsic foot muscle abductor hallucis was unchanged (p = 0.31). Because the novel exotendon design does not operate via the compression or bending of a bulky midsole, the device is light (55 g) and its profile is low enough that it can be worn within an existing shoe.

Comparison of The Electrophysiological Characteristics of Tight Filum Terminale And Tethered Cord Syndrome

This study aims to characterize tight filum terminale (TFT) in motor evoked potential (MEP) testing by comparing TFT patients with both tether cord syndrome (TCS) patients and healthy subjects. Fifty TFT patients, 18 TCS patients, and 35 healthy volunteers participated in this study. We recorded MEPs following transcranial magnetic stimulation from the bilateral abductor hallucis muscles as well as compound muscle action potentials and F-waves evoked by electrical stimulation of the tibial nerve from the bilateral abductor pollicis brevis muscles. The peripheral conduction time (PCT) was calculated from the latency of the compound action potential and F-wave. Furthermore, the central motor conduction time (CMCT) was calculated by subtracting PCT from MEP latency. TFT and TCS patients had a significantly longer MEP latency than healthy subjects. PCT in TFT patients were significantly longer than those in TCS patients or healthy subjects. Using the cut-off values for PCT, we were able to diagnose patients with TFT patients with a sensitivity of 72.0% and a specificity of 91.4%. Prolonged PCT in the MEP test may be a useful indicator for TFT and suggests that MEP may be used as an adjunct diagnostic tool for TFT.

Evaluation of Skeletal Muscle Activity During Foot Training Exercises Using Positron Emission Tomography

The foot exercises “rock-paper-scissors” and “towel gathering” are widely used in patients with lower limb disorders; however, there are no detailed reports on muscle activity during such training. We quantitatively evaluated the difference in skeletal muscle activity between the two exercises using positron emission tomography. Eight university student athletes were included. Four participants each were assigned to the foot rock-paper-scissors and towel gathering groups. Participants in each group underwent continuous training for 15 min. They received an intravenous injection of 18F-fluorodeoxyglucose and retrained for 15 min, following which they rested for 45 min. Regions of interest were defined in 25 muscles. The standardized uptake value (SUV) in the trained limb was compared with that in the non-trained control limb. SUVs increased in four skeletal muscles (tibialis anterior, peroneus brevis, extensor hallucis brevis, and abductor hallucis) in the rock-paper-scissors group, and in four muscles (flexor digitorum longus, extensor hallucis brevis, extensor digitorum brevis, and quadratus plantae) in the towel gathering group. Thus, foot rock-paper-scissors and towel gathering affected skeletal muscles related to the medial longitudinal arch and toe grip strength, respectively. Given that the two exercises target different skeletal muscles, they should be taught and implemented according to their respective purposes.

Topographic-anatomical characteristics of artery tibialis posterior and its branches in the area of ankle canal

AIM: To clarify peculiarities of the anatomy and topography of the plantar vessels in the area of the ankle canal, to justify access to the bifurcation of the artery tibialis posterior and ultrasound examination of the plantar arteries. The results of anatomical preparations of 10 amputated lower limbs, and of ultrasound duplex angioscanning (DUS) of 30 healthy volunteers without pathology of the vascular system performed using a linear transducer with frequency of 7–12 MHz, were studied. According to the data of anatomical preparation and ultrasound examination, the bifurcation level of the artery tibialis posterior was 1.7 ± 0.4 cm (min 0.5 cm — max 2 cm) below the level of the posterior edge of the medial ankle and was slightly covered by the musculus abductor hallucis. The average diameter of the artery tibialis posterior above the bifurcation level was 2.56 ± 0.4 mm, of the medial plantar artery 1.4±0.44 mm, and of the lateral plantar artery 1.8 ± 0.5 mm. The lateral plantar artery was 90% larger in diameter than the medial plantar artery. In 7% of cases, the medial plantar artery was larger, and in 3% of cases, the diameters of both arteries were equal. When taking the bifurcation of the posterior tibial artery as the central point, the plantar vessels on the DUS can be traced distally down under the abdomen of the musculus abductor hallucis: the medial vessels lie more anteriorly at 2 o’clock position, and the lateral vessels lie somewhat posteriorly at 1 o’clock. Assessment of blood flow at this level gives an idea of the state of the foot vessels. The level of bifurcation of the artery tibialis posterior is located 1.7 ± 0.4 cm below the posterior edge of the medial malleolus, which makes it possible to identify the location of access to it. The location of the DUS probe from this point at 2 o'clock position corresponds to the projection of the medial plantar artery, at 1 o'clock — to the lateral plantar artery on the right lower limb, on the left lower limb — at 10 and 11 o'clock, respectively.

“Like For Like” Reconstruction of Heel Pad with Medial Plantar Artery Flap—Functional and Aesthetic Outcomes in A Series of 19 Cases

Heel pad loss can cause serious problems in weight-bearing and locomotion. The medial plantar artery (MPA) flap is a suitable “like for like” replacement. Nineteen patients whose heels were reconstructed with MPA flap between July 2015 and February 2020 were studied. All patients were assessed based on flap survival, functionality, and patient satisfaction. Loss of heel pad was due to diabetic ulcer (11), trauma (6), tumor (1), and unstable scar (1). The largest flap measured 9 × 7 cm. Sixteen flaps were done as fasciocutaneous flaps and three in combination with abductor hallucis muscle (AbdH). All the flaps survived. The average functional scores at 6, 12, 18, and 24 months were 86.86, 89.62, 89.38 and 97.33 based on AOSAS-AH score. Average patients' satisfaction was 8.7/10. To conclude, the MPA system is a versatile vascular axis providing “like for like” tissue for heel pad reconstruction which is reliable and durable.

Examining the efficacy of short foot exercises as an effective stand-alone treatment for mechanical low back pain associated with foot overpronation

BACKGROUND: Abnormal foot mechanics in foot over-pronation has an identified relationship with mechanical low back pain (MLBP). OBJECTIVE: To explore the use of short foot exercises (SFEs) as a standalone treatment for MLBP with foot over-pronation. METHODS: Forty-six patients with MLBP (PwMLBP) presenting with and foot over-pronation were analyzed. They were randomized into the SFE (short foot exercise), SFE plus traditional physical therapy treatment (SFE+TPT), and control (CG) groups. Functional disability and pain level were measured using the Oswestry Disability Index (ODI) and visual analog scale (VAS), respectively. Ultrasonography measured the cross-sectional area (CSA) of the abductor hallucis (AbdH) muscle. The foot posture and navicular drop (ND) were investigated using the foot posture index-6 (FPI) score and ND test, respectively. RESULTS: The CSA of the AbdH and VAS scores improved significantly (p< 0.001) between the groups, more in the SFE+TPT group than in the SFE group (p< 0.001). The ND, FPI, and ODI measures improved significantly among the groups (p< 0.001), with no significant difference (p> 0.002) between the SFE and SFE+TPT groups. The CG did not show significant differences in the outcome measures (p> 0.002). Based on the effect size, SFEs significantly improved all the variables of interest (d>1). CONCLUSION: SFEs, with or without TPT may offer an effective treatment for PwMLBP with foot over-pronation.