Morphological and mechanical properties of plantar fascia and intrinsic foot muscles in individuals with and without flat foot

Ultrasound assessment of talar cartilage thickness measurements in asymptomatic subjects with pes planus and its relationship with anthropometric parameters

INTRODUCTION

Individuals with pes planus may have alterations in talar cartilage thickness due to changes in lower extremity alignment. The aim of this study was to measure the talar cartilage thickness of subjects with pes planus and compare the results with those of healthy controls. Another aim of the present study was to evaluate its relationship with anthropometric foot parameters.

METHODS

This cross-sectional study included 48 individuals (16 males and 32 females) in the pes planus group and 48 individuals in the healthy control group (14 males and 34 females) based on the Navicular Drop (ND) test and the Foot Posture Index (FPI). Talar cartilage thickness (TCT) was measured with ultrasound. Anthropometric foot parameters of the individuals, such as foot length and foot width, were evaluated using a podoscope.

RESULTS

TCT was higher in participants with pes planus compared to the control group (dominant side, p = 0.006; non-dominant side, p = 0.002). Foot width and length were similar in both groups for the dominant and non-dominant feet (p > 0.05). TCT on the dominant foot was positively correlated with the FPI score (r = 0.205, p = 0.045), ND score (r = 0.297, p = 0.003), foot width (r = 0.244, p = 0.017) and foot length (r = 0.253, p = 0.013). On the other hand, TCT on the non-dominant side was positively correlated with the FPI score (r = 0.235, p = 0.021), ND score (r = 0.363, p < 0.001), foot width (r = 0.270, p = 0.008) and length (r = 0.303, p = 0.003).

CONCLUSION

The talar cartilage of patients with pes planus seems to be thicker, and this is generally related to body weight, body mass index, foot anthropometrics, and posture characteristics.

LEVEL OF EVIDENCE

Level III, diagnostic comparative study.

Fatigue of the intrinsic foot core muscles had a greater effect on gait than extrinsic foot core muscles: A time-series based analyze

BACKGROUND

The Heel Rise endurance (HRE) which indicates the extrinsic foot core (ECO) muscle's performance and the paper grip endurance (PGE) which indicates the intrinsic foot core (ICO) muscle's performance are essential components of a healthy foot function. However, the foot core muscles' fatigue response on spatial and temporal gait parameters after the HRE and the PGE tests were not adequately investigated. The purpose of this study was to determine whether the fatigue of the ICO and the ECO muscles affect gait parameters.

MATERIAL AND METHODS

A prospective, cross-sectional study was conducted on 22 sedentary individuals (44 feet). Gait was investigated pre and after the Heel Rise (HR) endurance test and the paper grip (PG) endurance test by inertial sensors. At least 500 consecutive steps were collected for each individual. Spatial-temporal gait parameters were used as outcome measures.

RESULTS

ECO fatigue and ICO fatigue led to increases in the step length (p < 0.05) and the stride lengths (p < 0.05), the single support (p < 0.05), and the terminal stance durations (p < 0.05). It was also seen that ICO fatigue had a greater effect on gait than ECO fatigue. The ECO fatigue had a medium to large effect on the gait parameters (d=0.313-0.646). The ICO fatigue affected gait with a large effect (d=0.524-2.048).

CONCLUSION

The ECO fatigue and the ICO fatigue led to clinically important changes in long-range gait parameters and the ICO fatigue had a greater effect on gait than ECO fatigue. It was suggested that clinicians add ICO muscle endurance training to improve the physical performance of individuals.

Foot and Ankle Muscle Isometric Strength in Nonrearfoot Compared With Rearfoot Endurance Runners

Background

Transitioning to a forefoot strike pattern can be used to manage running-related knee injuries. However, adopting a nonrearfoot strike induces a higher load on foot and ankle structures than rearfoot strike. Sufficient foot muscle strength is also necessary to prevent excessive longitudinal arch (LA) deformation when running with nonrearfoot strike. The aim of this study was to investigate the potential differences in foot-ankle muscle strength between RF and NRF runners.

Methods

A cross-sectional study including 40 RF and 40 NRF runners was conducted. The foot posture and the maximal voluntary isometric strength (MVIS) of 6 foot-ankle muscles were measured. The footstrike pattern was determined using a 2-D camera during a self-paced run on a treadmill.

Results

NRF had higher MVIS for ankle plantar flexor (+12.5%, P = .015), ankle dorsiflexor (+17.7%, P = .01), hallux flexor (+11%, P = .04), and lesser toe flexor (+20.8%, P = .0031). We found a small positive correlation between MVIS of ankle plantar flexor with MVIS of hallux flexor (r = 0.26; P = .01) and lesser toe flexor (r = 0.28; P = .01).

Conclusion

In this cross-sectional study, we found that NRF runners on average have a higher MVIS of hallux and lesser toe flexor compared with RF runners. NRF runners also have a higher MVIS of ankle plantar flexor and dorsiflexor than RF runners. We found only a small correlation between ankle plantar flexor and foot muscle strength.

Level of Evidence

Level III, case-control study.

Current evidence regarding 2D ultrasonography monitoring of intrinsic foot muscle properties: A systematic review

Background

Ultrasonography can discriminate between intrinsic and extrinsic foot muscle properties and has therefore gained considerable popularity as an indirect strength evaluation. However, an overview on the use of ultrasound for assessing intrinsic foot musculature (IFM) is currently lacking.

Research question

What is the current evidence regarding (1) 2D ultrasonography protocols and its reliability? (2) Reference values for cross-sectional area and dorso-plantar thickness evaluation in asymptomatic and symptomatic persons?

Methods

The PRISMA guidelines were used to conduct this systematic review. Eight databases (PubMed, Embase, Web of Science, Cochrane Library, Scopus, CINAHL, SPORTDiscus and EuropePMC) were searched up to November 1, 2021. Studies reporting quantitative 2D ultrasound findings of the intrinsic foot muscles with no limitation to sex, BMI, ethnicity or physical activity were included. Studies were assessed for methodological quality using the Downs and Black checklist.

Results

Fifty-three studies were retained. Protocols showed an overall good to great reliability, suggesting limits of agreement between 8 and 30% of relative muscle size with minimal detectable changes varying from 0.10 to 0.29 cm² for cross-sectional area and 0.03-0.23 cm for thickness. Reference values are proposed for both cross-sectional area and thickness measurements of the abductor hallucis, flexor digitorum brevis, flexor hallucis brevis and quadratus plantae in asymptomatic persons. This could not be performed in the symptomatic studies due to a limited number of relevant studies addressing the symptomatic population, therefore a clinical overview is outlined. Clinically, IFM properties have been studied in ten distinct pathological conditions, predominantly pointing towards decreased muscle properties of the abductor hallucis.

Significance

We provide a clear and comprehensive overview of the literature regarding 2D ultrasonography of the IFM, making the available evidence more accessible to decision makers and researchers.

Effects of radial extracorporeal shockwave therapy versus high intensity laser therapy in individuals with plantar fasciitis: A randomised clinical trial

This study aimed to compare the effects of radial extracorporeal shockwave therapy (rESWT) to the effects of high-intensity laser therapy (HILT) in the treatment of individuals with plantar fasciitis. Thirty-two individuals with unilateral plantar fasciitis were randomized into two groups: rESWT and HILT. In each group, the individuals underwent the intervention two sessions per week, for three weeks. Outcome measures included morning pain, resting pain, pain at 80 newtons (N) pressure, skin blood flow and temperature, plantar fascia (PF) and flexor digitorum brevis (FDB) thickness, and Foot Function Index (FFI). There was no significant difference in baseline characteristics of the individuals in both groups. All outcome measures, except skin blood flow and temperature, and FDB thickness, were significantly different (p < 0.05) over time. Skin blood flow was significantly different between groups at the end of the program. Either HILT or rESWT could alleviate pain in individuals with plantar fasciitis significantly. However, HILT was better at reducing FFI (functional limitation domain) rather than rESWT. This study was a randomized clinical trial and was approved by Mahidol University-Central Institutional Review Board (MU-CIRB) following the Declaration of Helsinki, COA no. MU_CIRB 2020/207.0412, the Thai Clinical Trials Registry (TDTR) numbered TCTR2021012500.

Morphological and Mechanical Properties of Lower-Limb Muscles in Type 2 Diabetes: New Potential Imaging Indicators for Monitoring the Progress of DPN

The aim of this study was to explore changes in morphological and mechanical properties of lower-limb skeletal muscles in patients with diabetes with and without diabetic peripheral neuropathy (DPN) and seek to find a potential image indicator for monitoring the progress of DPN in patients with type 2 diabetes mellitus (T2DM). A total of 203 patients with T2DM, with and without DPN, were included in this study. Ultrasonography and ultrasound shear wave imaging (USWI) of the abductor hallux (AbH), tibialis anterior (TA), and peroneal longus (PER) muscles were performed for each subject, and the shear wave velocity (SWV) and cross-sectional area (CSA) of each AbH, TA, and PER were measured. The clinical factors influencing AbH_CSA and AbH_SWV were analyzed, and the risk factors for DPN complications were investigated. AbH_CSA and AbH_SWV in the T2DM group with DPN decreased significantly (P < 0.05), but no significant differences were found in the SWV and CSA of the TA and PER between the two groups. Toronto Clinical Scoring System (CSS) score and glycosylated hemoglobin (HbA1c) were independent predictors of AbH_CSA and AbH_SWV. As AbH_SWV and AbH_CSA decreased, Toronto CSS score and HbA1c increased and incidence of DPN increased significantly. In conclusion, the AbH muscle of T2DM patients with DPN became smaller and softer, while its morphological and mechanical properties were associated with the clinical indicators related to the progression of DPN. Thus, they could be potential imaging indicators for monitoring the progress of DPN in T2DM patients.

Associations of muscle volume of individual human plantar intrinsic foot muscles with morphological profiles of the foot

Human plantar intrinsic foot muscles consist of 10 muscles that originate and insert within the sole of the foot. It is known that the anatomical cross‐sectional area (ACSA) and muscle thickness of two plantar intrinsic foot muscles, the flexor hallucis brevis (FHB) and abductor hallucis (ABH), associate with morphological parameters of the foot, such as total and truncated foot length and navicular height. However, it is unclear how the size for each of the plantar intrinsic foot muscles associates with various morphological profiles of the foot. This study aimed to elucidate this subject. By using magnetic resonance imaging (MRI), serial images of the right foot were obtained in 13 young adult men without foot deformities. From the obtained MR images, ACSA for each of the individual plantar intrinsic foot muscles was analyzed along the foot length, and then its muscle volume (MV) was calculated. The analyzed muscles were the abductor digiti minimi (ABDM), ABH, adductor hallucis oblique head (ADDH‐OH), adductor hallucis transverse head (ADDH‐TH), flexor digitorum brevis (FDB), FHB, and quadratus plantae (QP). Furthermore, MV of the whole plantar intrinsic foot muscle (WHOLE) was defined as the total MVs of all the analyzed muscles. As morphological parameters, total foot length, truncated foot length, forefoot width, ball circumference, instep circumference, navicular height, great toe eversion angle, and little toe inversion angle were measured using a laser three‐dimensional foot scanner in standing and sitting conditions. In addition, navicular drop (ND) and normalized truncated navicular height (NTNH) were also calculated as medial longitudinal arch (MLA) height indices. The MV of WHOLE was significantly associated with the forefoot width, ball circumference, and instep circumference (r = 0.647–0.711, p = 0.006–0.013). Positive correlations were found between the forefoot width and MV of FHB, FDB, and QP (r = 0.564–0.653, p = 0.015–0.045), between the ball circumference and MV of QP (r = 0.559, p = 0.047), between the instep circumference and MV of FHB (r = 0.609, p = 0.027), and between the little toe inversion angle and MV of QP (r = 0.570, p = 0.042). The MVs of ABH, ABDM, and ADDH‐OH were not significantly correlated with any morphological parameters of the foot. Similarly, no significant correlations were found between MV of each muscle and either of the MLA height indices (ND and NTNH). Thus, the current results indicate that forefoot width and circumferential parameters (instep and ball circumference), not MLA height, associate with the size of the whole plantar intrinsic foot muscles, especially those specialized in toe flexion (FHB, FDB, and QP).

Anterior Tibial Tendon Side-to-Side Tenorrhaphy after Posterior Tibial Tendon Transfer: A Technique to Improve Reliability in Drop Foot after Common Peroneal Nerve Injury

Common peroneal nerve injury is present in 40% of knee dislocations, and foot drop is the principal complication. Posterior tibial tendon transfer is a viable solution to replace the function of the anterior tibial tendon (ATT) in the mid-foot. Several techniques for posterior tibial tendon transfer exist today, with variable results reported. However, adding augmentation with side-to-side tenorrhaphy of ATT to the transferred posterior tibial tendon (PTT) enhances anterior tissue balance and load sharing stress between native ATT enthesis and PTT tenodesis, allowing early rehabilitation and improving functional outcomes. Side-to-side tenorrhaphy is performed after PTT tenodesis in the lateral cuneiform to improve reliability in foot drop. This technique allows shorter immobilization time (from 6 to 2 weeks), earlier rehabilitation, sooner weight-bearing, and decreased risk of arthrofibrosis, scar formation, and muscle atrophy.

On the morphological relations of the Achilles tendon and plantar fascia via the calcaneus: a cadaveric study

Current treatments of plantar fasciitis are based on the premise that the Achilles tendon (AT) and plantar fascia (PF) are mechanically directly linked, which is an area of debate. The aim of this study was to assess the morphological relationship between the AT and PF. Nineteen cadaveric feet were x-ray imaged, serially sectioned and plastinated for digital image analyses. Measurements of the AT and PF thicknesses and cross-sectional areas (CSA) were performed at their calcaneal insertion. The fiber continuity was histologically assessed in representative subsamples. Strong correlations exist between the CSA of the AT and PF at calcaneal insertion and the CSA of PF's insertional length (r = 0.80), and between the CSAs of AT's and PF's insertional lengths. Further correlations were observed between AT and PF thicknesses (r = 0.62). This close morphological relationship could, however, not be confirmed through x-ray nor complete fiber continuity in histology. This study provides evidence for a morphometric relationship between the AT and PF, which suggests the presence of a functional relationship between these two structures following the biological key idea that the structure determines the function. The observed morphological correlations substantiate the existing mechanical link between the AT and PF via the posterior calcaneus and might explain why calf stretches are a successful treatment option for plantar heel pain.

Flat foot and spinal degeneration: Evidence from nationwide population-based cohort study

BACKGROUND/PURPOSE

Flat foot can alter the lower limb alignment and cause knee and back pain. To explore the association between flat foot and spinal degeneration.

METHODS

By using a claims dataset containing 1 million random samples, individuals with flat foot were identified between January 1, 2000, and December 31, 2013. The study assembled a flat foot group and a matched non-flat foot group. Definition of flat foot was according to International Classification of Diseases, Ninth Revision, Clinical Modification (ICD-9-CM) codes. The diagnosis date was defined as the index date for follow-up initiation. The follow-up period was defined as the duration from the index date (or nested index date for controls) to the occurrence of spinal degenerative joint disease (DJD), or December 31, 2013. The primary outcome was record of spinal DJD retrieved from the same database. Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% confidence intervals (CIs), with the control group as a reference.

RESULTS

We identified 13,965 patients (most aged <30 years, 88%); 2793 patients were assigned to the flat foot group and 11,172 individuals to the non-flat foot group matched by age, sex, and index year. The mean follow-up duration was approximately 74 months. In total, 329 (11.78%) patients in the study group and 931 (8.33%) patients in the comparison group developed spinal DJD. The adjusted HR (95% CI) of spinal DJD for study group was 1.423(1.250-1.619) compared with the control. Sensitivity analyses with propensity score match and different scenario about spinal DJD enrollment showed similar results. Subgroup analysis showed that in patients aged >45 years with history of flat foot, the adjusted hazard ratios were 1.434, 3.065, 3.110, and 2.061 in association with spondylosis, intervertebral disc disorder, cervical stenosis, thoracic-lumbar-sacral stenosis, respectively.

CONCLUSION

Flat foot was found to be an independent risk factor for subsequent spinal DJD.

Thickness, cross-sectional area, and stiffness of intrinsic foot muscles affect performance in single-leg stance balance tests in healthy sedentary young females

The purpose of this study was to investigate the effect of thickness, cross-sectional area and stiffness of intrinsic foot muscles on performance in single-leg stance balance tasks in healthy sedentary young females. This study included a total of 40 healthy sedentary young females between the ages of 19 and 35 years. Single-leg stance balance assessments were carried out using Biodex Balance Systems (Biodex Medical Systems, Shirley, NY, USA). Performance in the single-leg stance balance tests was assessed using the overall stability index (OSI), mediolateral stability index (MLSI) and the anteroposterior stability index (APSI). Lower scores indicated better postural stability. Stiffness, thickness and cross-sectional area measurements of the abductor hallucis (AbH), flexor digitorum brevis (FDB) and flexor hallucis brevis (FHB) muscles were performed using an ultrasonography device. Larger AbH and FHB muscles were correlated with higher OSI, APSI, and MLSI (r = 0.31-0.46, p < 0.05), whereas larger FDB muscle was correlated with higher OSI and MLSI (r = 0.28-0.38, p < 0.05). Higher stiffness of the AbH and FHB muscles were correlated with lower OSI, APSI, and MLSI (r = -0.32 to 0.58, p < 0.05), but stiffness of the FDB muscle was not significantly correlated with OSI, APSI, and MLSI (r = 0.03-0.22, p ˃ 0.05). These results suggest that larger AbH, FDB and FHB muscles are related to reduced performance in single-leg stance balance tests, whereas higher AbH and FHB stiffness are related to better performance in single-leg stance balance tests in healthy sedentary young females.

An investigation of the relationship between plantar pressure distribution and the morphologic and mechanic properties of the intrinsic foot muscles and plantar fascia

BACKGROUND

The purpose of this study was to investigate the relationship between plantar pressure distribution and the stiffness, thickness, and cross-sectional area of the plantar fascia (PF) and abductor hallucis (AbH), flexor hallucis brevis (FHB), and flexor digitorum brevis (FDB) muscles.

METHODS

The present study included a total of 41 healthy females between the ages of 20 and 34 years. Plantar pressure during static standing position was measured using a pedobarography system (MatScan, Tekscan, Inc., South Boston, Massachusetts, USA). Peak pressure, mean pressure, maximum force (Max-F), contact area (Con-A), pressure time integral, and force time integral (FTI) were measured. The thickness, cross-sectional area and stiffness of the intrinsic foot muscles and PF were measured using an ACUSON S3000 Ultrasound System and a 9L4 probe (4-9 MHz) (Siemens Medical Solution, Mountain View, CA, USA). Shear Wave Velocity (SWV) of the intrinsic foot muscles and PF was measured using a customized software program (Virtual Touch Imaging and Quantification; Siemens Medical Solution).

RESULTS

Con-A had a moderate correlation with the thickness and cross-sectional area of PF, AbH, FHB, and FDB. A fair to moderate correlation was found between heel Max-F and the thickness and cross-sectional area of PF, AbH, FHB, and FDB. There is no significant correlation between the SWV of the assessed tissues and plantar pressure distribution parameters. Body mass and BMI had a fair to good correlation with Mean-P, Con-A, heel Max-F, midfoot Max-F, metatarsal Max-F, FTI, thickness, and cross-sectional area of the PF and assessed muscles SIGNIFICANCE: The results suggest that abnormal force, contact area, and higher body mass may cause hypertrophy of the PF and foot intrinsic muscles.