Gliding resistance of the posterior tibial tendon

The Foot and Ankle Kinematics of a Simulated Progressive Collapsing Foot Deformity During Stance Phase: A Cadaveric Study

BACKGROUND

Progressive collapsing foot deformity (PCFD) is a complex pathology associated with tendon insufficiency, ligamentous failure, joint malalignment, and aberrant plantar force distribution. Existing knowledge of PCFD consists of static measurements, which provide information about structure but little about foot and ankle kinematics during gait. A model of PCFD was simulated in cadavers (sPCFD) to quantify the difference in joint kinematics and plantar pressure between the intact and sPCFD conditions during simulated stance phase of gait.

METHODS

In 12 cadaveric foot and ankle specimens, the sPCFD condition was created via sectioning of the spring ligament and the medial talonavicular joint capsule followed by cyclic axial compression. Specimens were then analyzed in intact and sPCFD conditions via a robotic gait simulator, using actuators to control the extrinsic tendons and a rotating force plate underneath the specimen to mimic the stance phase of walking. Force plate position and muscle forces were optimized using a fuzzy logic iterative process to converge and simulate in vivo ground reaction forces. An 8-camera motion capture system recorded the positions of markers fixed to bones, which were then used to calculate joint kinematics, and a plantar pressure mat collected pressure distribution data. Joint kinematics and plantar pressures were compared between intact and sPCFD conditions.

RESULTS

The sPCFD condition increased subtalar eversion in early, mid-, and late stance (P < .05), increased talonavicular abduction in mid- and late stance (P < .05), and increased ankle plantarflexion (P < .05), adduction (P < .05), and inversion (P < .05). The center of plantar pressure was significantly (P < .01) medialized in this model of sPCFD and simulated stance phase of gait.

DISCUSSION

Subtalar and talonavicular joint kinematics and plantar pressure distribution significantly changed with the sPCFD and in the directions expected from a PCFD foot. We also found that ankle joint kinematics changed with medial and plantar drift of the talar head, indicating abnormal talar rotation. Although comparison to an in vivo PCFD foot was not performed, this sPCFD model produced changes in foot kinematics and indicates that concomitant abnormal changes may occur at the ankle joint with PCFD.

CLINICAL RELEVANCE

This study describes the dynamic kinematic and plantar pressure changes in a cadaveric model of simulated progressive collapsing foot deformity during simulated stance phase.

[Etiology, pathogenesis, clinical features, diagnostics and conservative treatment of adult flatfoot]

BACKGROUND

On average, one in six adults is affected by an acquired flatfoot. This foot deformity is characterized by its progression of stages and in 10% of cases causes complaints that require treatment. Untreated, the loss of walking ability may result in the final stage. Correct staging is crucial to being able to offer a specific course of therapy including a wide spectrum of conservative and operative treatments.

MATERIAL AND METHODS

This review is based on pertinent publications retrieved from a selective search in PubMed and Medline and on the authors' clinical experience.

DIAGNOSTICS

The loss of function of static (spring ligament complex) and dynamic (tibialis posterior tendon) stabilizers causes the characteristic deformity with loss of the medial arch, hind foot valgus and forefoot abduction. In the late stage, severe secondary osteoarthritis in upper and lower ankle joints occurs and impedes walking ability. The essential physical examination is supplemented by weight-bearing dorsoplantar and lateral radiographs, which provide further information about axial malalignment (Meary's angle, Kite's angle). The long axis hind foot view allows analysis of the hindfoot valgus. MRI provides further information about the integrity of the tibialis posterior tendon, spring ligament complex and cartilage damage.

THERAPY

The therapy aims to reduce pain, regain function and avoid development of secondary osteoarthritis and degenerative tendon disorders. Progress of the deformity should be stopped. Therefore, the main aspects of the deformity-loss of medial arch, hindfoot valgus and forefoot abduction should be addressed and corrected. In the acute phase, tendovaginitis of the tibialis posterior tendon can be treated sufficiently by anti-inflammatory measures, relieving mechanical loads on the tendon and muscle and physiotherapy.

Biomechanics and Orthotic Treatment of the Adult Acquired Flatfoot

The adult acquired flatfoot deformity resulting from posterior tibial tendon dysfunction is the result of rupture of the posterior tibial tendon as well as key ligaments of the ankle and hindfoot. Kinematic studies have verified certain levels of deformity causing hindfoot eversion, lowering of the medial longitudinal arch and forefoot abduction. The condition is progressive and left untreated will cause significant disability. Bracing with ankle-foot orthoses has shown promising results in arresting progression of deformity and avoiding debilitating surgery. Various types of ankle-foot orthoses have been studied in terms of effects on gait as well as efficacy in treatment.

Can an insole for obese individuals maintain the arch of the foot against repeated hyper loading?

BACKGROUND

Insoles are often applied as preventive therapy of flatfoot deformity, but the therapeutic effects on obese individuals are still controversial. We aimed to investigate the effect of insole use on time-dependent changes in the foot arch during a repeated-loading simulation designed to represent 20,000 contiguous steps in individuals with a BMI value in the range of 30-40 kg/m2.

METHODS

Eighteen cadaveric feet were randomly divided into the following three groups: normal, obese, and insole. Ten thousand cyclic loadings of 500 N (normal group) or 1000 N (obese and insole groups) were applied to the feet. We measured time-dependent change in arch height and calculated the bony arch index (BAI), arch flexibility, and energy absorption.

RESULTS

The normal group maintained more than 0.21 BAI, which is the diagnostic criterion for a normal arch, throughout the 10,000 cycles; however, BAI was less than 0.21 at 1000 cycles in the obese group (mean, 0.203; 95% confidence interval [CI] 0.196-0.209) and at 6000 cycles in the insole group (mean, 0.200; 95% CI, 0.191-0.209). Although there was a significant time-dependent decrease in flexibility and energy absorption in both the obese and insole groups (P < 0.001), the difference between 1 and 10,000 cycles were significantly smaller in the insole group than in the obese group (P = 0.024).

CONCLUSIONS

Use of insoles for obese individuals may help to slow time-dependent foot structural changes. However, the effect was not enough to maintain the foot structure against repeated hyper loadings.

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.

Adult-Acquired Flatfoot Deformity

Adult-acquired flatfoot deformity (AAFD) comprises a wide spectrum of ligament and tendon failure that may result in significant deformity and disability. It is often associated with posterior tibial tendon deficiency (PTTD), which has been linked to multiple demographic factors, medical comorbidities, and genetic processes. AAFD is classified using stages I through IV. Nonoperative treatment modalities should always be attempted first and often provide resolution in stages I and II. Stage II, consisting of a wide range of flexible deformities, is typically treated operatively with a combination of soft tissue procedures and osteotomies. Stage III, which is characterized by a rigid flatfoot, typically warrants triple arthrodesis. Stage IV, where the flatfoot deformity involves the ankle joint, is treated with ankle arthrodesis or ankle arthroplasty with or without deltoid ligament reconstruction along with procedures to restore alignment of the foot. There is limited evidence as to the optimal procedure; thus, the surgical indications and techniques continue to be researched.

Ultrasound-guided hydrodissection decreases gliding resistance of the median nerve within the carpal tunnel

INTRODUCTION

The aim of this study was to assess alterations in median nerve (MN) biomechanics within the carpal tunnel resulting from ultrasound-guided hydrodissection in a cadaveric model.

METHODS

Twelve fresh frozen human cadaver hands were used. MN gliding resistance was measured at baseline and posthydrodissection, by pulling the nerve proximally and then returning it to the origin. Six specimens were treated with hydrodissection, and 6 were used as controls.

RESULTS

In the hydrodissection group there was a significant reduction in mean peak gliding resistance of 92.9 ± 34.8 mN between baseline and immediately posthydrodissection (21.4% ± 10.5%; P = 0.001). No significant reduction between baseline and the second cycle occurred in the control group: 9.6 ± 29.8 mN (0.4% ± 5.3%; P = 0.467).

DISCUSSION

Hydrodissection can decrease the gliding resistance of the MN within the carpal tunnel, at least in wrists unaffected by carpal tunnel syndrome. A clinical trial of hydrodissection seems justified. Muscle Nerve 57: 25-32, 2018.

Posterior tibial tendoscopy

The posterior tibial tendon (PTT) helps the triceps surae to work more efficiently during ambulation. Disorders of the PTT include tenosynovitis, acute rupture, degenerative tears, dislocation, instability, enthesopathies, and chronic tendinopathy with dysfunction and flat foot deformity. Open surgery of the PTT has been the conventional approach to deal with these disorders. However, tendoscopy has become a useful technique to diagnose and treat PTT disorders. This article focuses on PTT tendoscopy and tries to provide an understanding of the pathomechanics of the tendon, indications for surgery, surgical technique, advantages, complications, and limitations of this procedure.

Dynamic effect of the tibialis posterior muscle on the arch of the foot during cyclic axial loading

BACKGROUND

The most common cause of acquired flatfoot deformity is tibialis posterior tendon dysfunction. The present study compared the change in medial longitudinal arch height during cyclic axial loading with and without activated tibialis posterior tendon force.

METHODS

Fourteen normal, fresh frozen cadaveric legs were used. A total of 10,000 cyclic axial loadings of 500 N were applied to the longitudinal axis of the tibia. The 32-N tibialis posterior tendon forces were applied to the specimens of the active group (n=7). Specimens of another group (non-active group, n=7) were investigated without the tibialis posterior tendon force. The bony arch index was calculated from the displacement of the navicular height.

FINDINGS

The mean initial bony arch indexes with maximal weightbearing were 0.239 (SD 0.009) in active group and 0.239 (SD 0.014) in non-active group. After 7000 cycles, the bony arch indexes with maximal weightbearing were significantly greater in the active group (mean 0.214, SD 0.013) than in the non-active group (mean 0.199, SD 0.013). The mean bony arch indexes with maximal weightbearing after 10,000 cycles were 0.212 (SD 0.011) in the active group and 0.196 (SD 0.015) in the non-active group.

INTERPRETATION

The passive supportive structures were inadequate, and the tibialis posterior muscle was essential to maintain the medial longitudinal arch of the foot in the dynamic weightbearing condition. The findings underscore that physical therapy and arch supportive equipments are important to prevent flatfoot deformity in the condition of weakness or dysfunction of the tibialis posterior muscle.

Deep posterior compartment strength and foot kinematics in subjects with stage II posterior tibial tendon dysfunction

BACKGROUND

Tibialis posterior muscle weakness has been documented in subjects with Stage II posterior tibial tendon dysfunction (PTTD) but the effect of weakness on foot structure remains unclear. The association between strength and flatfoot kinematics may guide treatment such as the use of strengthening programs targeting the tibialis posterior muscle.

MATERIALS AND METHODS

Thirty Stage II PTTD subjects (age; 58.1 +/- 10.5 years, BMI 30.6 +/- 5.4) and 15 matched controls (age; 56.5 +/- 7.7 years, BMI 30.6 +/- 3.6) volunteered for this study. Deep Posterior Compartment strength was measured from both legs of each subject and the strength ratio was used to compare each subject's involved side to their uninvolved side. A 20% deficit was defined, a priori, to define two groups of subjects with PTTD. The strength ratio for each group averaged; 1.06 +/- 0.1 (range 0.87 to 1.36) for controls, 1.06 +/- 0.1 (range, 0.89 to 1.25), for the PTTD strong group, and 0.64 +/- 0.2 (range 0.42 to 0.76) for the PTTD weak group. Across four phases of stance, kinematic measures of flatfoot were compared between the three groups using a two-way mixed effect ANOVA model repeated for each kinematic variable.

RESULTS

Subjects with PTTD regardless of group demonstrated significantly greater hindfoot eversion compared to controls. Subjects with PTTD who were weak demonstrated greater hindfoot eversion compared to subjects with PTTD who were strong. For forefoot abduction and MLA angles the differences between groups depended on the phase of stance with significant differences between each group observed at the pre-swing phase of stance.

CONCLUSION

Strength was associated with the degree of flatfoot deformity observed during walking, however, flatfoot deformity may also occur without strength deficits.

CLINICAL RELEVANCE

Strengthening programs may only partially correct flatfoot kinematics while other clinical interventions such as bracing or surgery may also be indicated.

Effects of foot orthoses on the work of friction of the posterior tibial tendon

BACKGROUND

Posterior tibial tendon dysfunction is a significant contributor to flatfeet. Non-operative treatments, like in-shoe orthoses, have varying degrees of success. This study examined changes to the work of friction of the posterior tibial tendon under three conditions: intact, simulated flatfoot, and flatfoot with an orthosis. It was hypothesized that work of friction of the posterior tibial tendon would significantly increase in the flatfoot, yet return to normal with an orthosis. Changes to bone orientation were also expected.

METHODS

Six lower limb cadavers were mounted in a foot simulator, that applied axial and a posterior tibial tendon load. Posterior tibial tendon excursion, gliding resistance, and foot kinematics were monitored, and work of friction calculated. Each specimen moved through a range of motion in the coronal, transverse, and sagittal planes.

FINDINGS

Mean work of friction during motion in the coronal plane were 0.17 N cm (SD 0.07 N cm), 0.25 N cm (SD 0.09 N cm), and 0.23 N cm (SD 0.09 N cm) for the intact, flatfoot, and orthosis conditions, respectively. Motion in the transverse plane yielded average WoF of 0.36 N cm (SD 0.28 N cm), 0.64 N cm (SD 0.25 N cm), and 0.57 N cm (SD 0.38 N cm) in the same three conditions, respectively. The average tibio-calcaneal and tibio-metatarsal valgus angles significantly increased in the flatfoot condition (5.8 degrees and 9 degrees , respectively). However, the orthosis did slightly correct this angle.

INTERPRETATION

The prefabricated orthosis did not consistently restore normal work of friction, though it did correct the flatfoot visually. This implies that patients with flatfeet may be predisposed to developing posterior tibial tendon dysfunction due to abnormal gliding resistance, though bone orientations are restored.

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

Tibialis posterior has a vital role during gait as the primary dynamic stabiliser of the medial longitudinal arch; however, the muscle and tendon are prone to dysfunction with several conditions. We present an overview of tibialis posterior muscle and tendon anatomy with images from cadaveric work on fresh frozen limbs and a review of current evidence that define normal and abnormal tibialis posterior muscle activation during gait. A video is available that demonstrates ultrasound guided intra-muscular insertion techniques for tibialis posterior electromyography.Current electromyography literature indicates tibialis posterior intensity and timing during walking is variable in healthy adults and has a disease-specific activation profile among different pathologies. Flat-arched foot posture and tibialis posterior tendon dysfunction are associated with greater tibialis posterior muscle activity during stance phase, compared to normal or healthy participants, respectively. Cerebral palsy is associated with four potentially abnormal profiles during the entire gait cycle; however it is unclear how these profiles are defined as these studies lack control groups that characterise electromyographic activity from developmentally normal children. Intervention studies show antipronation taping to significantly decrease tibialis posterior muscle activation during walking compared to barefoot, although this research is based on only four participants. However, other interventions such as foot orthoses and footwear do not appear to systematically effect muscle activation during walking or running, respectively. This review highlights deficits in current evidence and provides suggestions for the future research agenda.

Revision of failed flatfoot surgery

Revision of failed flatfoot surgery presents a unique and challenging dilemma for the foot and ankle surgeon. Revision surgery is focused on establishing a plantigrade foot with correction of the hindfoot valgus, midfoot abduction, and forefoot varus. Successful reconstruction of failed flatfoot surgery begins with a proper evaluation. No treatment algorithm exists for the management of the malaligned flatfoot. Patient complaints, an understanding of the initial deformity and biomechanical problems, and surgeon experience play a role in correction of failed flatfoot surgery.

The effect of Stage II posterior tibial tendon dysfunction on deep compartment muscle strength: a new strength test

BACKGROUND

The purpose of this study was to compare isometric subtalar inversion and forefoot adduction strength in subjects with Stage II posterior tibial tendon dysfunction (PTTD) to controls.

MATERIALS AND METHODS

Twenty four subjects with Stage II PTTD and fifteen matched controls volunteered for this study. A force transducer (Model SML-200, Interface, Scottsdale, AZ) was connected with a resistance plate and oscilloscope (TDS 410A, Tektronix, Beaverton, OR) to the foot. Via the oscilloscope, subjects were given feedback on the amount of force produced and muscle activation of the anterior tibialis (AT) muscle. Subjects were instructed to maintain a plantar flexion force while performing a maximal voluntary subtalar inversion and forefoot adduction effort. A two-way ANOVA model with the factors including, side (involved/uninvolved) and group (control/PTTD) was used.

RESULTS

The PTTD group on the involved side showed significantly decreased subtalar inversion and foot adduction strength (0.70 +/- 0.24 N/Kg) compared to the uninvolved side (0.94 +/- 0.24 N/Kg) and controls (involved side = 0.99 +/- 0.24 N/Kg, uninvolved side = 0.97 +/- 0.21 N/Kg). The average AT activation was between 11% to 17% for both groups, however, considerable variability in subjects with PTTD.

CONCLUSION

These data confirm a subtalar inversion and forefoot adduction strength deficit by 20% to 30% in subjects with Stage II PTTD. Although isolating the PT muscle is difficult, a test specific to subtalar inversion and forefoot adduction demonstrated the weakness in this population.

Calcaneal osteotomies for the treatment of adult-acquired flatfoot

Calcaneal osteotomies are useful procedures for the treatment of stage 2 adult-acquired flatfoot. Often combined with adjunctive soft-tissue procedures, the posterior calcaneal displacement osteotomy and Evans procedure provide effective realignment of pes planovalgus deformity. Preoperative evaluation, indications, contraindications, surgical considerations and techniques are discussed.

Biomechanics and clinical analysis of the adult acquired flatfoot

The adult acquired flatfoot is a deformity that results from the loss of dynamic and static supportive structures of the medial longitudinal arch. The severity of the deformity is dependent upon the role of ligamentous disruption on the hindfoot that can be determined by careful clinical examination. Treatment of the adult flatfoot requires an understanding of the biomechanical effects of deforming forces, tendon dysfunction, ligament disruption, and joint sublaxation.