Tibialis posterior in health and disease: a review of structure and function with specific reference to electromyographic studies

Contribution of the tibialis posterior and peroneus longus to inter-segment coordination of the foot during single-leg drop jump

Abnormal foot motion is considered to be related to sports related injuries. This study aimed to identify the relationship between calf muscle activity and inter-segment coordination of the foot during single-leg drop jumps. Eleven healthy men participated and performed single-leg drop jumps from a 30-cm box. Muscle activity of the tibialis posterior (TP), flexor digitorum longus, peroneus longus (PL) and gastrocnemius were measured. The rearfoot and midfoot segment angle from landing to leaping were calculated according to the Rizzoli Foot Model and time scaled to 100%. A modified vector coding technique was employed to classify inter-segment coordination of every 1% into four patterns (in-phase, anti-phase, rearfoot phase,and midfoot phase). The relationship between percentage of each pattern and muscle activity levels were statistically analysed with correlation coefficient. The TP showed a significant positive correlation with percentage of in-phase in coronal plane (r = 0.61, p = 0.045). The PL also showed a trend of positive correlation to in-phase in coronal plane (r = 0.59, p = 0.058). TP and PL muscle activities may modulate the inter-segment coordination between the rearfoot and midfoot in coronal plane. Clinically, these muscles should be assessed for abnormal inter-segment foot motion.

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.

Functional relationship between the foot intrinsic and extrinsic muscles in walking

The intrinsic and extrinsic muscles are considered to stabilize the foot and contribute to propulsion during walking. This study aimed to clarify the functional relationship between intrinsic and extrinsic muscles during walking. Thirteen healthy men participated in this study. The muscle activities of the intrinsic muscles (quadratus plantae and abductor hallucis), and the extrinsic muscles (flexor hallucis longus, flexor digitorum longus, and tibialis posterior) were measured using fine-wire and surface electromyography during walking. The muscle onset timing after foot contact was calculated and compared among muscles using the one-way ANOVA. The stance phase was divided into early and late braking, and early and late propulsion phases. Muscle activity among phases was compared using repeated-measures ANOVA. The onset time of the abductor hallucis was significantly earlier than those of the flexor digitorum longus and tibialis posterior. The quadratus plantae demonstrated significantly earlier onset than that of the tibialis posterior. In the late propulsion phase, the activity of extrinsic muscles decreased, whereas intrinsic muscles were continuously active. Early activation of the intrinsic muscles may stabilize the foot for efficient torque production by the extrinsic muscles. Furthermore, the intrinsic muscles may contribute to the final push-off after the deactivation of extrinsic muscles.

Human skeletal muscle-specific atrophy with aging: a comprehensive review

Age-related skeletal muscle atrophy appears to be a muscle group-specific process, yet only a few specific muscles have been investigated and our understanding in this area is limited. This review provides a comprehensive summary of the available information on age-related skeletal muscle atrophy in a muscle-specific manner, nearly half of which comes from the quadriceps. Decline in muscle-specific size over ∼50 yr of aging was determined from 47 cross-sectional studies of 982 young (∼25 yr) and 1,003 old (∼75 yr) individuals and nine muscle groups: elbow extensors (-20%, -0.39%/yr), elbow flexors (-19%, -0.38%/yr), paraspinals (-24%, -0.47%/yr), psoas (-29%, -0.58%/yr), hip adductors (-13%, -0.27%/yr), hamstrings (-19%, -0.39%/yr), quadriceps (-27%, -0.53%/yr), dorsiflexors (-9%, -0.19%/yr), and triceps surae (-14%, -0.28%/yr). Muscle-specific atrophy rate was also determined for each of the subcomponent muscles in the hamstrings, quadriceps, and triceps surae. Of all the muscles included in this review, there was more than a fivefold difference between the least (-6%, -0.13%/yr, soleus) to the most (-33%, -0.66%/yr, rectus femoris) atrophying muscles. Muscle activity level, muscle fiber type, sex, and timeline of the aging process all appeared to have some influence on muscle-specific atrophy. Given the large range of muscle-specific atrophy and the large number of muscles that have not been investigated, more muscle-specific information could expand our understanding of functional deficits that develop with aging and help guide muscle-specific interventions to improve the quality of life of aging women and men.

Tibialis posterior muscle stiffness assessment in flat foot subjects by ultrasound based Shear-Wave Elastography

BACKGROUND

Few methodologies are used to assess Tibialis Posterior muscle stiffness. Those present limitations leading to a lack of evidence. Muscle stiffness assessment can help in the injuries risk factors identification while coupling with Ultrasound based Shear-Wave Elastography for its management. However, a precise and reliable methodology needs to be utilized to increase stiffness accuracy among the entire Tibialis Posterior muscle. Therefore, this study aims to investigate the stiffness association between Tibialis posterior deep and superficial layer and between flat and neutral footed subjects.

METHODS

The sample consisted of 18 participants, where 9 subjects represent the flatfoot group and 9 the neutral foot group. Only the subjects who presented a Navicular Drop Test value of > 9 mm were included in the flatfooted group. All participants were submitted to the Tibialis posterior stiffness assessment with the help of Ultrasound base Shear-Wave Elastography in a lying supine position. Association between Tibialis Posterior deep and superficial layers were determined by Pearson's correlation analysis and group differences were assessed using the U-Mann Whitney test in the comparison between flat foot and neutral foot group (p < 0.05).

RESULTS

No significant correlations between Tibialis Posterior layers stiffness were found (p = 0.194), nor in the comparison between both neutral and flat foot groups (p = 0.424/p = 0.258).

CONCLUSION

Among participants, no associations between tibialis posterior layers stiffness were found. Also, we did not find any differences in the stiffness between flat and neutral foot groups. In this study, the stiffness did not differentiate flat-footed subjects from neutral subjects.

Characteristics and Future Direction of Tibialis Posterior Tendinopathy Research: A Scoping Review

Background and Objectives: Tibialis posterior tendon pathologies have been traditionally categorized into different stages of posterior tibial tendon dysfunction (PTTD), or adult acquired flatfoot deformity (AAFD), and more recently to progressive collapsing foot deformity (PCFD). The purpose of this scoping review is to synthesize and characterize literature on early stages of PTTD (previously known as Stage I and II), which we will describe as tibialis posterior tendinopathy (TPT). We aim to identify what is known about TPT, identify gaps in knowledge on the topics of TPT, and propose future research direction. Materials and Methods: We included 44 studies and categorized them into epidemiology, diagnosis, evaluation, biomechanics outcome measure, imaging, and nonsurgical treatment. Results: A majority of studies (86.4%, 38 of 44 studies) recruited patients with mean or median ages greater than 40. For studies that reported body mass index (BMI) of the patients, 81.5% had mean or median BMI meeting criteria for being overweight. All but two papers described study populations as predominantly or entirely female gender. Biomechanical studies characterized findings associated with TPT to include increased forefoot abduction and rearfoot eversion during gait cycle, weak hip and ankle performance, and poor balance. Research on non-surgical treatment focused on orthotics with evidence mostly limited to observational studies. The optimal exercise regimen for the management of TPT remains unclear due to the limited number of high-quality studies. Conclusions: More epidemiological studies from diverse patient populations are necessary to better understand prevalence, incidence, and risk factors for TPT. The lack of high-quality studies investigating nonsurgical treatment options is concerning because, regardless of coexisting foot deformity, the initial treatment for TPT is typically conservative. Additional studies comparing various exercise programs may help identify optimal exercise therapy, and investigation into further nonsurgical treatments is needed to optimize the management for TPT.

Anatomical Study of Sites and Surface Area of the Attachment Region of Tibial Posterior Tendon Attachment

BACKGROUND

The purpose of this study was not only to examine the attachment site but also to quantify the effect of the tibialis posterior tendon (TPT) on each attachment site by examining the surface area of the attachment region.

METHODS

We examined 100 feet from 50 Japanese cadavers. The TPT attachment to the navicular bone (NB), medial cuneiform bone (MCB), and lateral cuneiform bone (LCB) were set as the main attachment sites (Type I). The attachment seen in Type I with the addition of one additional site of attachment was defined as Type II. Furthermore, surface area was measured using a three-dimensional scanner.

RESULTS

Attachment to the NB, MCB, and LCB was present in all specimens. The TPT attachment to the NB, MCB, and LCB comprised 75.1% of total attachment surface area. The ratio of the NB, MCB, and LCB in each type was about 90% in Types II and III, and 70-80% in Types IV-VII.

CONCLUSION

The quantitative results demonstrated the NB, MCB, and LCB to be the main sites of TPT attachment, although individual differences in attachment sites exist, further developing the findings of previous studies.

Effects of a 9-weeks arch support intervention on foot morphology in young soccer players: a crossover study

Background

A flat foot is a common cause of chronic sports injuries and therefore many opportunities for arch support interventions exist. However, young athletes change their foot morphology due to developmental influences even without intervention. Therefore, developmental influences need to be considered when examining the effects of arch support, but there have not been sufficient longitudinal studies to date. This study aimed to determine the effect of the arch support intervention by performing a 9-weeks arch support intervention on the foot morphology and cross-sectional area of the foot muscles in flat-footed young athletes. Thirty-one elementary school boys (Age 11.4 ± 0.5 years, Height 145.2 ± 7.4 cm, Weight 38.8 ± 8.3 kg, BMI 18.2 ± 2.2 kg/m²) with a decreased medial longitudinal arch in the foot posture index were selected as participants from a local soccer club and randomly divided into two groups.

Methods

In one group, in the intervention period, an existing arch supporter was used to provide arch support, while in the other group, no special intervention was provided in the observation period. To account for developmental effects, the intervention study was conducted as an 18-weeks crossover study in which the intervention and observational phases were switched at 9 weeks after the intervention. Foot morphology was assessed using a three-dimensional foot measuring machine, and the cross-sectional area (CSA) of the internal and external muscles of the foot was assessed using an ultrasound imaging device. We examined the effect of the intervention by comparing the amount of change in the measurement results between the intervention and observation periods using corresponding t-tests and Wilcoxon signed-rank sum test, analysis of covariance methods.

Results

After adapting the exclusion criteria, 14 patients (28 feet) were included in the final analysis. The CSA of the abductor hallucis muscle (ABH) increased 9.7% during the intervention period and 3.0% during the observation period (p = 0.01). The CSA of the flexor digitorum longus muscle (FDL) increased 7.7% during the intervention period and 4.2% during the observation period (p = 0.02).

Conclusion

A 9-weeks arch supporter intervention may promote the development of the ABH and FDL CSA in young flat-footed soccer players.

Posterior tibial tendon dysfunction alters the midfoot mechanics and energetics during gait

A comprehensive insight into the in vivo foot kinetics of patients with posterior tibial tendon dysfunction (PTTD) is lacking to support clinical decision making. Our goal was to study how PTTD alters the kinetic and kinematic characteristics of the foot and ankle with a special focus on the midfoot joints. Multisegment foot joint kinetics and kinematics were compared based on the Rizzoli Foot Model and inversed dynamics between a control group (n = 25), patients with PTTD Stage II (n = 21) and PTTD Stage III (n = 4) over the entire stance phase. Compared to controls, a mean decrease in power generation of 1.3 W/kg was found in the Ankle joint in PTTD II patients (p < 0.001) and PTTD III patients of 1.5 W/kg (p < 0.001). In the Chopart joint, there was a mean increase in power absorption of 0.4 W/kg in the PTTD III patients (p = 0.014) and a mean decrease in power generation of 0.6 W/kg (p < 0.001) in the PTTD II patients. The distribution of total negative work showed a shift from the Ankle and first metatarsal phalangeal joint towards the Chopart joint in both PTTD compared with the control subjects. A significant reduction in range of motion was observed among both PTTD groups. The outcome of this study will enable the possibility to customize the conservative and surgical treatment of each patient with PTTD, to improve or even restore the kinetic features. This will prevent the natural deterioration of function seen in this pathology.

The effect of texture under distinct regions of the foot sole on human locomotion

Sensory feedback from the foot sole plays an important role in shaping human locomotion. While net muscle activity and kinematic changes have been correlated with electrical stimulation to five topographical regions of the foot, it remains unknown if these responses are similar with tactile stimulation. The purpose of this study was to use texture in foot orthosis design, applied to five distinct regions under the foot sole, and measure joint kinematics, location of center of pressure, and muscle activity of eight lower leg muscles during level and incline walking. Fifty-five healthy adults completed 48 walking trials in textured and non-textured foot orthoses. Study results confirm that tactile stimulation is stimulation-site and gait-phase specific in modulating lower leg muscle activity during walking. For example, texture under the lateral forefoot consistently generated a suppression of EMG and texture under the lateral midfoot always generated a facilitation. In early stance, adding texture under the medial midfoot or calcaneus facilitated extensor muscle activity and suppressed flexor muscle activity. Texture under the lateral midfoot or medial forefoot facilitated tibialis posterior activation. These results support the topographical organization of cutaneous mechanoreceptors in foot sole skin while considering how texture can be used in foot orthosis design to target lower leg muscular changes during locomotion.

A smart insole system capable of identifying proper heel raise posture for chronic ankle instability rehabilitation

Heel raise is widely prescribed to patients with chronic ankle instability in order to strengthen the Peroneus Longus muscle (PL) which supports the weakened lateral collateral ligaments. While the exercise itself is intuitive, ankle orientation is of particular importance because heel raises performed with inversion do not well recruit the PL. This implies that proper execution is imperative and a means to assess heel raise training sessions is needed. In this study we present a smart insole system capable of identifying heel raise events and its corresponding rise, hold and drop phases, which allows for a more descriptive analysis. The results from our heel raise sessions, which consist of four different variants performed by five healthy subjects, suggest that medial–lateral foot pressure distribution and foot orientation are needed to differentiate heel raises performed with ankle eversion and inversion. We go further and substantiate that proper execution, detected by our system, indeed leads to increased PL activation by analyzing the electromyography signals. We believe that the proposed system may provide clinicians with invaluable information regarding onsite as well as at-home training and possibly, with biofeedback, serve as foundation for software as a medical device.

Ultrasonographic Validation for Needle Placement in the Tibialis Posterior Muscle

BACKGROUND

The tibialis posterior (TP) muscle plays an important role in normal foot function. Safe, efficacious therapeutic approaches addressing this muscle are necessary; however, the location of the muscle in the deep posterior compartment can create challenges.

PURPOSE

The purpose of this study was to assess the accuracy of needle placement in the TP muscle and determine the needle placement in relation to the neurovascular structures located within the deep compartment.

DESIGN

Cross Sectional Study.

METHODS

Needle placement and ultrasound imaging were performed on 20 healthy individuals. A 50 mm or 60 mm needle was inserted between 30 - 50% of the tibial length measured from the medial tibiofemoral joint. The needle was inserted in a medial to lateral direction into the right extremity with the patient in right side lying. Placement of the needle into the TP muscle was verified with ultrasound imaging, and the shortest distance from the needle to the posterior tibial artery and tibial nerve was measured. The depth from the skin to the superficial border of the TP muscle was also measured.

RESULTS

Ultrasonography confirmed the needle filament was inserted into the TP muscle in all 20 individuals and did not penetrate the neurovascular bundle in any individual. The mean distance from the needle to the tibial nerve and posterior tibial artery was 10.0 + 4.7 mm and 10.2 + 4.7 mm respectively. The superficial border of the TP muscle from the skin was at a mean depth of 25.8 + 4.9 mm.

CONCLUSION

This ultrasound imaging needle placement study supports placement of a solid filament needle into the TP muscle with avoidance of the neurovascular structures of the deep posterior compartment when placed from a medial to lateral direction at 30-50% of the tibial length.

LEVEL OF EVIDENCE

2b.

The immediate effects of foot orthosis geometry on lower limb muscle activity and foot biomechanics

Foot orthoses (FOs) are used to treat clinical conditions by altering the external forces applied to the foot and thereafter the forces of muscles and tendons. However, whether specific geometric design features of FOs affect muscle activation is unknown. The aim of this study was to investigate if medial heel wedging and increased medial arch height have different effects on the electromyography (EMG) amplitude of tibialis posterior, other muscles of the lower limb and the kinematics and kinetics at the rearfoot and ankle. Healthy participants (n = 19) walked in standardised shoes with i) a flat inlay; ii) a standard shape FOs, iii) standard FOs adjusted to incorporate a 6 mm increase in arch height, iv) and standard FOs adjusted to incorporate an 8° medial heel wedging and v) both the 6 mm increase in arch height and 8° increase in medial wedging. EMG was recorded from medial gastrocnemius, peroneus longus, tibialis anterior and in-dwelling tibialis posterior muscles. Motion and ground reaction force data were collected concurrently. Tibialis posterior EMG amplitude reduced in early stance with all FOs (ηp² = 0.23-1.16). Tibialis posterior EMG amplitude and external ankle eversion moment significantly reduced with FOs incorporating medial wedging. The concurrent reduction in external eversion moment and peak TP EMG amplitude in early stance with medial heel wedging demonstrates the potential for this specific FOs geometric feature to alter TP activation. Medial wedged FOs could facilitate tendon healing in tibialis posterior tendon dysfunction by reducing force going through the TP muscle tendon unit.

A New Anatomical Classification for Tibialis Posterior Tendon Insertion and Its Clinical Implications: A Cadaveric Study

The variations in the tibialis posterior tendon (TPT) could not be defined by previous classification; thus, this study used a larger-scale cadaver with the aim to classify the types of TPT insertion based on the combination of the number and location of TPT insertions. A total of 118 feet from adult formalin-fixed cadavers were dissected (68 males, 50 females). The morphological characteristics and measurements of TPT insertion were evaluated. Four types of TPT insertions were classified, wherein the most common type was type 4 (quadruple insertions, 78 feet, 66.1%), which was divided into four new subtypes that were not defined in the previous classification. The second most common type was type 3 (triple insertions, 25 feet, 21.2%) with three subtypes, including the new subtype. Type 2 was found in 13 feet (11%), and the rarest type was type 1 (2 feet, 1.7%), wherein the main tendon was only attached to the navicular bone and the medial cuneiform bone. We suggest high morphological variability of the TPT in relation to the insertion location, along with the possibility of significant differences according to race and gender. Moreover, this classification will help clinicians understand adult flatfoot deformity-related posterior tibial tendon dysfunction (PTTD).

Correlates of night-time and exercise-associated lower limb cramps in healthy adults

INTRODUCTION/AIMS

We explored correlates of night-time and exercise-associated lower limb cramps in participants of the 1000 Norms Project.

METHODS

A volunteer community sample of healthy people aged ≥18 y underwent assessment of motor function and physical performance, and were questioned about muscle cramps in the previous 3 mo.

RESULTS

Of 491 (221 female) participants age 18-101 y (mean: 59.12; SD: 18.03), about 1 in 3 experienced night-time lower limb cramps, and about 1 in 4 experienced exercise-associated lower limb cramps. For night-cramps, a one unit increase in Beighton score (greater whole-body flexibility) was associated with a 31% reduced odds of cramps (odds ratio [OR] = 0.69, 95% confidence interval [CI]:0.45, 0.99) and passing all three lesser-toe strength tests was associated with 50% reduced odds of cramps (OR = 0.50, 95% CI: 0.32, 0.78). For exercise-associated cramps, participants in the fourth (lowest arch) quartile of Foot Posture Index were 2.1 times (95% CI: 1.11, 3.95) more likely to experience cramps than participants in the first (highest arch) quartile. Odds of experiencing both types of cramps versus no cramps were lower with passing all three lesser-toe strength tests (OR = 0.40, 95% CI: 0.19, 0.85) and better performance in the six-minute walk test (OR = 0.997, 95% CI: 0.996, 0.998).

DISCUSSION

People who experienced both exercise-associated and night-time cramps were less functional. The association between night-time cramps with less whole-body flexibility and reduced lesser-toe flexor strength should be explored to determine causation. Planovalgus (low-arched) foot type was independently associated with exercise-associated cramps. The effectiveness of foot orthoses for secondary prevention of exercise-associated cramps in people with low-arched feet should be explored.

Extrinsic foot muscle forces and joint contact forces in flexible flatfoot adult with foot orthosis: A parametric study of tibialis posterior muscle weakness

BACKGROUND

The posterior tibialis tendon dysfunction (PTTD) is typically associated with progressive flatfoot deformity, which could be alleviated with foot orthosis. However, the evaluation of tibialis posterior (TP) weakness on lower limb mechanics of flatfoot adults with foot orthoses is scarce and requires further investigation.

RESEARCH QUESTION

This study aimed to examine the effects of TP weakness on lower limb mechanics in flatfoot adults with foot orthosis through gait analysis and musculoskeletal modelling.

METHODS

Fifteen young adults with flatfoot were recruited from University to perform a gait experiment with and without foot orthoses. Data collected from the motion capture system were used to drive the musculoskeletal modelling for the estimation of the joint force and extrinsic muscle forces of the lower limb. A parametric analysis was conducted by adjusting the TP muscle strength from 40 % to 100 %. Two-way repeated measures ANOVA was used to compare the peak extrinsic foot muscle forces and joint forces among different levels of TP weakness and insole conditions.

RESULTS

TP weakness significantly increased ankle joint force superoinferiorly (F = 125.9, p < 0.001) and decreased anteroposteriorly (F = 125.9, p < 0.001), in addition to a significant increase in the muscle forces of flexor hallucis longus (p < 0.001) and flexor digitorum longus (p < 0.001). Besides, the foot orthosis significantly reduced most peak muscle forces whilst significantly reduced the second peak knee force and peak ankle force compared to the control condition (F = 8.79-30.9, p < 0.05).

SIGNIFICANCE

The increased extrinsic foot muscle forces (flexor hallucis longus and flexor digitorum longus) and ankle joint forces in the TP weakness condition indicated that TP weakness may induce compensatory muscle activation and attenuated joint load. The abnormal muscle and joint mechanics in flatfoot adults with TP weakness might be restored by the orthosis.

Alterated ligamento-muscular reflex pattern after stimulation of the anterior talofibular ligament in functional ankle instability

PURPOSE

Ligamento-muscular reflex pattern following stimulation of the anterior talofibular ligament (ATFL) was examined.

METHODS

The peroneus longus (PL), the tibialis anterior (TA), and tibialis posterior (TP) muscles were investigated in sixteen patients with functional ankle instability (FAI) and 16 age- and gender-matched controls. The ATFL was stimulated with a fine wire electrode while electromyographic (EMG) activities were recorded during isometric foot contraction of 20% maximal force in plantarflexion, dorsiflexion, supination and pronation. The complete measurement was repeated after a peroneal block anesthesia.

RESULTS

Statistically significant changes in post-stimulus EMG activity were observed in all three muscles and all four tested foot positions. In supination, the PL showed no reactions in both groups before and after anesthesia. The post-stimulus inhibition of the TA seen after 80 and 180 ms disappeared in controls after anesthesia. The TP had similar inhibitory responses in both groups.

CONCLUSION

Ligamento-muscular reflex pattern is alterated in FAI. While early reactions are essential in protecting the ankle joint in sudden movements, the later responses indicate a supraspinal control of neuromuscular stability of the ankle joint. Proprioceptive rehabilitation of the PL, TA, and TP is crucial in FAI to compensate for post-traumatic ligamentomuscular reflex deficiencies.

LEVEL OF EVIDENCE

II.

Ultrasound Imaging Is Reliable for Tibialis Posterior Size Measurements

OBJECTIVES

The tibialis posterior (TP) is a vital muscle for controlling the medial longitudinal arch of the foot during weight-bearing activities. Dysfunction of this muscle is associated with a variety of pathologic conditions; thus, it is important to reliably assess its morphologic characteristics. Ultrasound (US) has been used to assess characteristics of TP tendons but not the muscle cross-sectional area (CSA). The purpose of this study was to establish a reliable US technique to measure the TP CSA and thickness.

METHODS

Twenty-three healthy volunteers participated. We evaluated the CSA and thickness at 4 measurement locations (anterior and posterior views at both 30% and 50% of the shank length).

RESULTS

The participants included 12 female and 11 male volunteers (mean age ± SD, 31.23 ± 14.93 years). Excellent reliability was seen for the CSA and thickness at all locations (intraclass correlation coefficients, 0.988-0.998). Limits of agreement (LoA) and standard errors of the measurement (SEMs) were slightly lower at the 30% locations (LoA at 30%, 4.6-9.2; LoA at 50%, 6.4-9.7; SEM at 30%, 0.03-0.05; SEM at 50%, 0.04-0.07). Strong correlations were seen between anterior and posterior measurements of the CSA (30%, r = 0.99; P < .0001; 50%, r = 0.94; P < .0001) and thickness (30%, r = 0.98; P < .0001; 50%, r = 0.95; P = .0001).

CONCLUSIONS

Based on these results, the TP can be measured accurately with US at any of the tested locations. Due to the ease of collection and the quality of the data, we recommend the anterior view at 30% of the shank length to measure the CSA. The ability to assess muscle size of the TP will aid in a variety of medical and research applications.

Posterior Tibial Tendon Integrity Can Be Screened With Plain Anteroposterior Foot Radiography

Posterior tibial tendon integrity is an important consideration when treating adult-acquired flatfoot caused by posterior tibial tendon dysfunction. The condition of this tendon traditionally has been evaluated with ultrasonography or magnetic resonance imaging, but recent advances in radiography have increased the resolution of radiographic soft tissue images. The authors examined whether the posterior tibial tendon could be screened with anteroposterior foot radiographs, based on interobserver agreement and accuracy. The authors retrospectively evaluated consecutive patients who underwent weight-bearing foot radiography and ultrasonography based on suspicion of posterior tibial tendinopathy. The integrity of the posterior tibial tendon was evaluated by 2 orthopedic surgeons with foot radiographs and scored as normal or abnormal. The authors evaluated interobserver agreement and compared the findings of ultrasonography and radiography to evaluate diagnostic accuracy. The study included 21 patients with a mean age of 51.5±15.7 years. Ultrasonography showed that 4 patients had normal tendon integrity, 6 patients had tenosynovitis and no tendinopathy, 8 patients had tendinopathy and tendon continuity, and 3 patients had loss of tendon continuity. The surgeons provided consistent radiographic findings for 81.0% of patients (17 of 21). On the basis of the ultrasonographic findings, the surgeons' accuracy was 76.2% (16 of 21) and 61.9% (13 of 21). The results indicate that weight-bearing anteroposterior foot radiography can be used to evaluate posterior tibial tendon integrity, which may allow orthopedic surgeons to predict the prognosis of patients with posterior tibial tendon dysfunction, determine the extent of surgical treatment, and evaluate tendon integrity postoperatively. [Orthopedics. 2020;43(6):e503-e507.].

A parametric study of effect of experimental tibialis posterior muscle pain on joint loading and muscle forces-Implications for patients with rheumatoid arthritis?

BACKGROUND

Foot pain and deformities are commonly encountered in patients with rheumatoid arthritis (RA). Likewise, Posterior tibial tendon dysfunction (PTTD) is commonly involved in development of foot and ankle abnormalities and has been reported with a prevalence in two-thirds of the RA patients.

RESEARCH QUESTION

Redundancy in the physiological function between different muscles provides the central nervous system multiple options to perform the same movement but which muscles compensate for the impairment of the tibialis posterior (TP) muscle? And how does these changes affect ankle joint loading?

METHODS

Experimental and computational disciplines were applied to investigate changes in muscle forces as result of induced pain in the right TP muscle. Twelve healthy subjects were enrolled in the study. Experimental pain was induced in the TP by a single ultrasound graphically guided injection of 1 mL hypertonic saline (5.0% Sodium Chloride). The participants' gait was assessed by skin marker-based motion capture and force plates. Musculoskeletal models were used to investigate compensation mechanisms systematically in the lower under extremity when TP muscle was recruited less as a consequence of the induced pain.

RESULTS

Experimental TP muscle pain and simulated reduced strength caused altered muscle recruitment and made the flexor digitorum longus and flexor hallucis longus muscles compensated for the impairment of the TP muscle. Further, the resultant ankle joint force was increased as the strength of the TP muscle was reduced.

SIGNIFICANCE

The compensation mechanism observed in the present study indicate that alterations in muscle recruitment and muscle force distribution as a result of the underlying disease inflammation itself may contribute to development of chronic foot pain and deformities in patients with RA. Further studies are required to understand the role of PTTD in occurrence of those late adverse musculoskeletal manifestations aiming at search for early preventive strategies.

Tibialis posterior muscle pain effects on hip, knee and ankle gait mechanics

BACKGROUND

Tibialis posterior (TP) dysfunction is a common painful complication in patients with rheumatoid arthritis (RA), which can lead to the collapse of the medial longitudinal arch. Different theories have been developed to explain the causality of tibialis posterior dysfunction. In all these theories, pain is a central factor, and yet, it is uncertain to what extent pain causes the observed biomechanical alterations in the patients. The aim of this study was to investigate the effect of experimental tibialis posterior muscle pain on gait mechanics in healthy subjects.

METHODS

Twelve healthy subjects were recruited for this randomized crossover study. Experimental pain was induced by ultrasound-guided injection of 1 mL hypertonic saline into the upper part of the right tibialis posterior muscle with the use of isotonic saline as non-pain-inducing control. Subsequently, kinematic data during three self-paced over ground walking for each condition were collected. Ground reaction forces and external moments were measured from force plates installed in the floor. Painful areas were evaluated using body charts and pain intensity scoring via a verbal numerical rating scale.

FINDINGS

Decreased hip internal rotation was observed during the pain condition at the end of the stance phase. There were no changes in gait velocity and duration of stand phase between the pain and no pain conditions. Reduced external joint moment was found for external knee rotation and for external hip rotation.

INTERPRETATION

The study has demonstrated that induced pain in the TP muscle evokes kinematic alteration in the hip and the knee joints, but not in the ankle, which suggest an underlying early stage joint compensatory mechanism. These findings suggest the need to include those joints in current physical evaluations of tibialis posterior dysfunction.

A proposal for a new classification for the tendon of insertion of tibialis posterior

Although the tendon of the tibialis posterior muscle (TPM) is high morphological variability, its insertion is not well defined in anatomy discussions. The aim of the work is to systematize the classification of tibialis posterior tendon insertion by anatomical dissection. Classical anatomical dissection was performed on 80 lower limbs (40 female, 40 male) fixed in 10% formalin solution. The morphology of the insertion of the tendon was evaluated, and the muscle was subjected to appropriate morphometric measurements. Four types of insertion were observed, the most common being Type III (35 cases - 43.75%): a triple distal attachment where the main tendon inserts to the navicular bone and the medial cuneiform bone, and two accessory bands insert to the medial, lateral, or intermediate cuneiform bone or to the metatarsal bones (II, III, IV, V) depending on subtypes (A-C). The second most common type was Type II (18 cases: 22.5%): a double distal attachment. Type IV (14 cases: 17.5%) was characterized by quadruple distal attachment and was also divided into three subtypes (A-B). The rarest type was Type I (13 cases: 16.25%), which was characterized by a single band: the main tendon inserts to the navicular bone and the medial cuneiform bone. The tendon of the TPM presents high morphological variability. Knowledge of the four particular types of insertions is essential for both clinicians and anatomists. Clin. Anat. 32:557-565, 2019. © 2019 Wiley Periodicals, Inc.

First ray mobility and posterior tibial tendon dysfunction (PTTD) in persons with flatfoot: A case control study

BACKGROUND

While posterior tibial tendon dysfunction (PTTD) commonly presents with flat feet and has been thought to be associated with first ray mobility, many flat-footed individuals are asymptomatic and do not experience any symptoms of PTTD. Thus, there is a need to control for foot type when studying factors related to PTTD. This study aimed to clarify if first ray mobility differed between flat-footed individuals with and without symptoms of PTTD. It was hypothesized that PTTD patients would display higher mobility of the first ray than asymptomatic flat-footed controls.

METHODS

Given that PTTD patients were often flat-footed, asymptomatic flat-footed individuals were chosen as controls to remove flatfoot as a potential confounding factor. We recruited 32 flat-footed subjects, of which 16 exhibiting PTTD symptoms and 16 asymptomatic controls matched for age, sex and body mass index. First ray mobility was assessed using subjective classification ("stiff", "normal" or "hypermobile") and maximum dorsal displacement using a ruler indicator. Mann-Whitney U was used to test for between-groups differences.

RESULTS

Subjective classification was similar between PTTD and control groups (both groups: 38% "normal" joint mobility). No significant differences were found between PTTD patients and asymptomatic controls in first ray displacement [median (IQR), PTTD: 6.00 (1.75) mm; control: 6.00 (1.00) mm; P=.31].

CONCLUSIONS

First ray mobility was not associated with PTTD in flat-footed persons. When evaluating symptoms of PTTD, clinicians should pay attention to factors other than first ray mobility.

Influence of tibialis posterior muscle activation on foot anatomy under axial loading: A biomechanical CT human cadaveric study

BACKGROUND

Collapse of the medial longitudinal arch and subluxation of the subtalar joint are common occurrences in adult flatfoot deformity. Controversy exists about the role of the tibialis posterior (TP) tendon as first and/or essential lesion. Subtle changes in the foot configuration can occur under weight bearing.

PURPOSE

This human cadaveric study is designed to investigate the effect that isolated actuation of the TP tendon has on the medial longitudinal arch and the hindfoot configuration under simulated weight bearing.

METHODS

A radiolucent frame was developed to apply axial loading on cadaveric lower legs during computer tomography (CT) examinations. Eight pairs of fresh-frozen specimens were imaged in neutral position under foot-flat loading (75N) and under single-leg stance weight bearing (700N) without and with addition of 150N pulling force on the TP tendon. Measurements of subtalar joint subluxation, forefoot arch angle and talo-first metatarsal angle were conducted on each set of CT scans.

RESULTS

Subtalar subluxation, talo-first metatarsal angle and talo-navicular coverage angle significantly increased under single-leg stance weight bearing, whereas forefoot arch angle significantly decreased. Actuation of the TP tendon under weight bearing did not restore the forefoot arch angle or correct subtalar subluxation and talo-metatarsal angle.

CONCLUSION

Significant effect that weight bearing has on the medial longitudinal arch and the subtalar joint configuration is demonstrated in an ex-vivo model. In absence of other medial column derangement, actuation of the TP tendon alone does not seem to reconstitute the integrity of the medial longitudinal arch or correct the hindfoot subluxation under weight bearing.

CLINICAL RELEVANCE

The findings of this study together with the developed model for ex-vivo investigation provide a further insight in foot anatomy.

Shoes alter the spring-like function of the human foot during running

The capacity to store and return energy in legs and feet that behave like springs is crucial to human running economy. Recent comparisons of shod and barefoot running have led to suggestions that modern running shoes may actually impede leg and foot-spring function by reducing the contributions from the leg and foot musculature. Here we examined the effect of running shoes on foot longitudinal arch (LA) motion and activation of the intrinsic foot muscles. Participants ran on a force-instrumented treadmill with and without running shoes. We recorded foot kinematics and muscle activation of the intrinsic foot muscles using intramuscular electromyography. In contrast to previous assertions, we observed an increase in both the peak (flexor digitorum brevis +60%) and total stance muscle activation (flexor digitorum brevis +70% and abductor hallucis +53%) of the intrinsic foot muscles when running with shoes. Increased intrinsic muscle activation corresponded with a reduction in LA compression (-25%). We confirm that running shoes do indeed influence the mechanical function of the foot. However, our findings suggest that these mechanical adjustments are likely to have occurred as a result of increased neuromuscular output, rather than impaired control as previously speculated. We propose a theoretical model for foot-shoe interaction to explain these novel findings.

Calf muscle activity alteration with foot orthoses insertion during walking measured by fine-wire electromyography

[Purpose] The purpose of the study was to assess the muscle activity change of the tibialis posterior, flexor digitorum longus, and peroneus longus during gait with orthoses. [Subjects and Methods] Sixteen healthy males participated in this study. Activity of each muscle was measured by using fine-wire and surface electromyography. Gait task was performed by the participants barefoot, with footwear and with orthoses. The electromyography data from a stance phase of each gait trial were used for analysis. The stance phase was divided into contact, midstance, and propulsion phases. The data from ten participants were extracted for final analysis, as electromyography measurements were unsuccessful for the other six. [Results] The results demonstrated that orthoses significantly reduced the tibialis posterior muscle activity in the propulsion phase compared to that in the barefoot condition. Although there was a significant difference in the midstance phase, post hoc analysis did not indicate significant differences among the phases. No significant electromyography amplitude change was detected in flexor digitorum longus and peroneus longus. [Conclusion] Orthothes reduced the tibialis posterior activity level during gait. This result may be beneficial for patients with injuries related to excessive activity of tibialis posterior.

MIDFOOT AND FOREFOOT INVOLVEMENT IN LATERAL ANKLE SPRAINS AND CHRONIC ANKLE INSTABILITY. PART 1: ANATOMY AND BIOMECHANICS

The modern human foot is the culmination of more than five million years of evolution. The ankle-foot complex absorbs forces during loading, accommodates uneven surfaces, and acts as a lever for efficient propulsion. The ankle-foot complex has six independent functional segments that should be understood for proper assessment and treatment of foot and ankle injuries: the shank, rearfoot, midfoot, lateral forefoot, and the medial forefoot. The compliance of the individual segments of the foot is dependent on velocity, task, and active and passive coupling mechanisms within each of the foot segments. It is also important to understand the passive, active, and neural subsystems that are functionally intertwined to provide structure and control to the multisegmented foot. The purpose of the first part of this clinical commentary and current concepts review was to examine foot and ankle anatomy, detail the roles of the intrinsic and extrinsic foot and ankle musculature from a multisegmented foot perspective, and discuss the biomechanics of the ankle-foot complex during function. The interplay of segmental joint mobility, afferent and efferent sensorimotor function, and movement and stabilization provided by the extrinsic and intrinsic musculature is required to coordinate and execute the complex kinematic movements in the ankle-foot complex during propulsion.

LEVEL OF EVIDENCE

5.

Development of a Robotic Assembly for Analyzing the Instantaneous Axis of Rotation of the Foot Ankle Complex

Ankle instantaneous axis of rotation (IAR) measurements represent a more complete parameter for characterizing joint motion. However, few studies have implemented this measurement to study normal, injured, or pathological foot ankle biomechanics. A novel testing protocol was developed to simulate aspects of in vivo foot ankle mechanics during mid-stance gait in a human cadaveric specimen. A lower leg was mounted in a robotic testing platform with the tibia upright and foot flat on the baseplate. Axial tibia loads (ATLs) were controlled as a function of a vertical ground reaction force (vGRF) set at half body weight (356 N) and a 50% vGRF (178 N) Achilles tendon load. Two specimens were repetitively loaded over 10 degrees of dorsiflexion and 20 degrees of plantar flexion. Platform axes were controlled within 2 microns and 0.008 degrees resulting in ATL measurements within ±2 N of target conditions. Mean ATLs and IAR values were not significantly different between cycles of motion, but IAR values were significantly different between dorsiflexion and plantar flexion. A linear regression analysis showed no significant differences between slopes of plantar flexion paths. The customized robotic platform and advanced testing protocol produced repeatable and accurate measurements of the IAR, useful for assessing foot ankle biomechanics under different loading scenarios and foot conditions.

Accuracy of needle placement in cadavers: non-guided versus ultrasound-guided

Objective

To compare the accuracy rates of non-guided vs. ultrasound-guided needle placement in four lower limb muscles (tibialis posterior, peroneus longus, and short and long heads of the biceps femoris).

Methods

Two electromyographers examined the four muscles in each of eight lower limbs from four fresh frozen cadavers. Each electromyographer injected an assigned dye into each targeted muscle in a lower limb twice (once without guidance, another under ultrasound guidance). Therefore, four injections were done in each muscle of one lower limb. All injections were performed by two electromyographers using 18 gauge 1.5 inch or 24 gauge 2.4 inch needles to place 0.5 mL of colored acryl solution into the target muscles. The third person was blinded to the injection technique and dissected the lower limbs and determined injection accuracy.

Results

A 71.9% accuracy rate was achieved by blind needle placement vs. 96.9% accuracy with ultrasound-guided needle placement (p=0.001). Blind needle placement accuracy ranged from 50% to 93.8%.

Conclusion

Ultrasound guidance produced superior accuracy compared with that of blind needle placement in most muscles. Clinicians should consider ultrasound guidance to optimize needle placement in these muscles, particularly the tibialis posterior.

Muscle-Activation Onset Times With Shoes and Foot Orthoses in Participants With Chronic Ankle Instability

CONTEXT

Participants with chronic ankle instability (CAI) use an altered neuromuscular strategy to shift weight from double-legged to single-legged stance. Shoes and foot orthoses may influence these muscle-activation patterns.

OBJECTIVE

To evaluate the influence of shoes and foot orthoses on onset times of lower extremity muscle activity in participants with CAI during the transition from double-legged to single-legged stance.

DESIGN

Cross-sectional study.

SETTING

Musculoskeletal laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 15 people (9 men, 6 women; age = 21.8 ± 3.0 years, height = 177.7 ± 9.6 cm, mass = 72.0 ± 14.6 kg) who had CAI and wore foot orthoses were recruited.

INTERVENTION(S)

A transition task from double-legged to single-legged stance was performed with eyes open and with eyes closed. Both limbs were tested in 4 experimental conditions: (1) barefoot (BF), (2) shoes only, (3) shoes with standard foot orthoses, and (4) shoes with custom foot orthoses (SCFO).

MAIN OUTCOME MEASURE(S)

The onset of activity of 9 lower extremity muscles was recorded using surface electromyography and a single force plate.

RESULTS

Based on a full-factorial (condition, region, limb, vision) linear model for repeated measures, we found a condition effect (F(3,91.8) = 9.39, P < .001). Differences among experimental conditions did not depend on limb or vision condition. Based on a 2-way (condition, muscle) linear model within each region (ankle, knee, hip), earlier muscle-activation onset times were observed in the SCFO than in the BF condition for the peroneus longus (P < .001), tibialis anterior (P = .003), vastus medialis obliquus (P = .04), and vastus lateralis (P = .005). Furthermore, the peroneus longus was activated earlier in the shoes-only (P = .02) and shoes-with-standard-foot-orthoses (P = .03) conditions than in the BF condition. No differences were observed for the hip muscles.

CONCLUSIONS

Earlier onset of muscle activity was most apparent in the SCFO condition for ankle and knee muscles but not for hip muscles during the transition from double-legged to single-legged stance. These findings might help clinicians understand how shoes and foot orthoses can influence neuromuscular control in participants with CAI.

Assessment of foot and ankle muscle strength using hand held dynamometry in patients with established rheumatoid arthritis

Background

The foot and ankle are frequently affected in patients with rheumatoid arthritis (RA). One of the negative consequences of RA on the physical function of patients is a decrease in muscle strength. However, little is known about foot and muscle strength in this population. The aim of the study was to evaluate significant differences in foot and ankle muscle strength between patients with established RA against age and sex-matched controls using hand-held dynamometry.

Methods

The maximal muscle strength of ankle plantarflexion, dorsiflexion, eversion and inversion was assessed in 14 patients with RA, mean (SD) disease duration of 22 (14.1) years, and 20 age and sex-matched control participants using hand-held dynamometry.

Results

Significant differences were observed in muscle strength between the two groups in plantarflexion (p = 0.00), eversion (p = 0.04) and inversion (p = 0.01). No significant difference was found in dorsiflexion (p > 0.05). The patients with RA displayed a significantly lower plantarflexion-dorsiflexion ratio than the control participants (p = 0.03).

Conclusions

The results from this study showed that the RA patients displayed a significant decrease in ankle dorsiflexion, eversion and inversion when compared to the non-RA control group suggesting that foot and ankle muscle strength may be affected by the pathological processes in RA. This study is a preliminary step for the measurement of muscle impairments within the RA population.

Reliability study of tibialis posterior and selected leg muscle EMG and multi-segment foot kinematics in rheumatoid arthritis associated pes planovalgus

OBJECTIVE

To determine within- and between-day reliability characteristics of electromyographic (EMG) activity patterns of selected lower leg muscles and kinematic variables in patients with rheumatoid arthritis (RA) and pes planovalgus.

METHODS

Five patients with RA underwent gait analysis barefoot and shod on two occasions 1 week apart. Fine-wire (tibialis posterior [TP]) and surface EMG for selected muscles and 3D kinematics using a multi-segmented foot model was undertaken barefoot and shod. Reliability of pre-determined variables including EMG activity patterns and inter-segment kinematics were analysed using coefficients of multiple correlation, intraclass correlation coefficients (ICC) and the standard error of the measurement (SEM).

RESULTS

Muscle activation patterns within- and between-day ranged from fair-to-good to excellent in both conditions. Discrete temporal and amplitude variables were highly variable across all muscle groups in both conditions but particularly poor for TP and peroneus longus. SEMs ranged from 1% to 9% of stance and 4% to 27% of maximum voluntary contraction; in most cases the 95% confidence interval crossed zero. Excellent within-day reliability was found for the inter-segment kinematics in both conditions. Between-day reliability ranged from fair-to-good to excellent for kinematic variables and all ICCs were excellent; the SEM ranged from 0.60° to 1.99°.

CONCLUSION

Multi-segmented foot kinematics can be reliably measured in RA patients with pes planovalgus. Serial measurement of discrete variables for TP and other selected leg muscles via EMG is not supported from the findings in this cohort of RA patients. Caution should be exercised when EMG measurements are considered to study disease progression or intervention effects.

Posterior tibial tendon dysfunction: a review

Posterior tibial tendon dysfunction is a progressive deformity that can result in the development of a pathologic flatfoot deformity. Numerous publications have studied the effects of clinical interventions at specific stages of progression of posterior tibial tendon dysfunction, but there is still uncertainty regarding the clinical identification of the condition. It is clear that more information regarding the etiology, progression, and risk factors of posterior tibial tendon dysfunction is required. Clear evidence exists that suggests that the quality of life for patients with posterior tibial tendon dysfunction is significantly affected. Furthermore, evidence suggests that early conservative intervention can significantly improve quality of life regarding disability, function, and pain. This would suggest that significant cost burden reductions could be made by improving awareness of the condition, which would improve early diagnosis. Early conservative intervention may help reduce the number of patients requiring surgery. This review focuses on the etiologic factors, epidemiologic features, and pathogenesis of posterior tibial tendon dysfunction. It aims to analyze, discuss, and debate the current understanding of this condition using the available literature. In addition, there is a discussion of the evidence base surrounding disease characteristics associated with the different clinical stages of posterior tibial tendon dysfunction.