Elongation and forces of ankle ligaments in a physiological range of motion

Joint synergy and muscle activity in the motion of the ankle-foot complex

The movement of the ankle-foot complex joints is coupled as a result of various physiological and physical constraints. This study introduces a novel approach to the analysis of joint synergies and their physiological basis by focusing on joint rotational directions and the types of muscle contractions. We developed a biomimetic model of the ankle-foot complex with seven degrees of freedom, considering the skeletal configuration and physiological axis directions. Motion capture experiments were conducted with eight participants performing dorsiflexion and plantarflexion in open-chain states, as well as various walking tasks in closed-chain states, across different ground inclinations (±10, ±5, 0 deg) and walking speeds (3 and 4 km h-1). Hierarchical cluster analysis identified joint synergy clusters and motion primitives, revealing that in open-chain movements, plantarflexion of the ankle, tarsometatarsal and metatarsophalangeal joints exhibited synergy with the inversion of the remaining joints in the complex; meanwhile, dorsiflexion was aligned with eversion. During closed-chain movements, the synergies grouping was exchanged in the subtalar, talonavicular and metatarsophalangeal joints. Further analysis showed that in open-chain movements, synergy patterns influenced by multi-joint muscles crossing oblique joint axes contribute to foot motion. In closed-chain movements, these changes in synergistic patterns enhance the propulsion of the center of mass towards the contralateral leg and improve foot arch compliance, facilitating human motion. Our work enhances the understanding of the physiological mechanisms underlying synergistic motion within the ankle-foot complex.

In vivo analysis of ankle joint kinematics and ligament deformation of chronic ankle instability patients during level walking

Introduction: Chronic ankle instability (CAI) carries a high risk of progression to talar osteochondral lesions and post-traumatic osteoarthritis. It has been clinically hypothesized the progression is associated with abnormal joint motion and ligament elongation, but there is a lack of scientific evidence. Methods: A total of 12 patients with CAI were assessed during level walking with the use of dynamic biplane radiography (DBR) which can reproduce the in vivo positions of each bone. We evaluated the uninjured and CAI side of the tibiotalar and subtalar joint for three-dimensional kinematics differences. Elongation of the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL) were also calculated bilaterally. Results: For patients with CAI, the dorsiflexion of the tibiotalar joint had reduced (21.73° ± 3.90° to 17.21° ± 4.35°), displacement of the talus increased (2.54 ± 0.64 mm to 3.12 ± 0.55 mm), and the inversion of subtalar joint increased (8.09° ± 2.21° to 11.80° ± 3.41°). Mean ATFL elongation was inversely related to mean dorsiflexion angle (CAI: rho = -0.82, P < 0.001; Control: rho = -0.92, P < 0.001), mean ATFL elongation was related to mean anterior translation (CAI: rho = 0.82, P < 0.001; Control: rho = 0.92, P < 0.001), mean CFL elongation was related to mean dorsiflexion angle (CAI: rho = 0.84, P < 0.001; Control: rho = 0.70, P < 0.001), and mean CFL elongation was inversely related to mean anterior translation (CAI: rho = -0.83, P < 0.001; Control: rho = -0.71, P < 0.001). Furthermore, ATFL elongation was significantly (CAI: rho = -0.82, P < 0.001; Control: rho = -0.78, P < 0.001) inversely correlated with CFL elongation. Discussion: Patients with CAI have significant changes in joint kinematics relative to the contralateral side. Throughout the stance phase of walking, ATFL increases in length during plantarflexion and talar anterior translation whereas the elongation trend of CFL was the opposite. This understanding can inform the development of targeted therapeutic exercises aimed at balancing ligament tension during different phases of gait. The interrelationship between two ligaments is that when one ligament shortens, the other lengthens. The occurrence of CAI didn't change this trend. Surgeons might consider positioning the ankle in a neutral sagittal plane to ensure optimal outcomes during ATFL and CFL repair.

Role of the intrinsic subtalar ligaments in subtalar instability and consequences for clinical practice

Subtalar instability (STI) is a disabling complication after an acute lateral ankle sprain and remains a challenging problem. The pathophysiology is difficult to understand. Especially the relative contribution of the intrinsic subtalar ligaments in the stability of the subtalar joint is still controversial. Diagnosis is difficult because of the overlapping clinical signs with talocrural instability and the absence of a reliable diagnostic reference test. This often results in misdiagnosis and inappropriate treatment. Recent research offers new insights in the pathophysiology of subtalar instability and the importance of the intrinsic subtalar ligaments. Recent publications clarify the local anatomical and biomechanical characteristics of the subtalar ligaments. The cervical ligament and interosseous talocalcaneal ligament seem to play an important function in the normal kinematics and stability of the subtalar joint. In addition to the calcaneofibular ligament (CFL), these ligaments seem to have an important role in the pathomechanics of subtalar instability (STI). These new insights have an impact on the approach to STI in clinical practice. Diagnosis of STI can be performed be performed by a step-by-step approach to raise the suspicion to STI. This approach consists of clinical signs, abnormalities of the subtalar ligaments on MRI and intraoperative evaluation. Surgical treatment should address all the aspects of the instability and focus on a restoration of the normal anatomical and biomechanical properties. Besides a low threshold to reconstruct the CFL, a reconstruction of the subtalar ligaments should be considered in complex cases of instability. The purpose of this review is to provide a comprehensive update of the current literature focused on the contribution of the different ligaments in the stability of the subtalar joint. This review aims to introduce the more recent findings in the earlier hypotheses on normal kinesiology, pathophysiology and relation with talocrural instability. The consequences of this improved understanding of pathophysiology on patient identification, treatment and future research are described.

The different subtalar ligaments show significant differences in their mechanical properties

BACKGROUND

Today, the relative contribution of each ligamentous structure in the stability of the subtalar joint is still unclear. The purpose of this study is to assess the material properties of the different ligamentous structures of the subtalar joint.

METHODS

Eighteen paired fresh-frozen cadaveric feet were used to obtain bone-ligament-bone complexes of the calcaneofibular ligament (CFL), the cervical ligament (CL) and the anterior capsular ligament-interosseous talocalcaneal ligament complex (ACaL-ITCL). The samples were subjected to uniaxial testing to calculate their respective stiffness and failure load.

RESULTS

The stiffness of ACaL-ITCL complex (mean: 150 ± 51 N/mm, 95% confidence interval (CI): 125.0-176.6 N/mm) was significantly higher than both CFL (mean: 55.8 ± 23.0 N/mm, CI: 43.8-67.7 N/mm) and CL (mean: 63.9 ± 38.0 N/mm, CI: 44.4-83.3 N/mm). The failure load of both the ACaL-ITCL complex (mean:382.5 ± 158 N, CI: 304.1-460.8 N) and the CFL (mean:320.4 ± 122.0 N, CI: 257.5-383.2 N) were significantly higher than that of the CL (mean:163.5 ± 58.0 N, CI: 131.3-195.7 N). The injury pattern demonstrated a partial rupture in all CFL and ACaL-ITCL specimens and in 60% of the CL specimens.

CONCLUSION

The CFL, CL and ACaL-ITCL show significant differences in their intrinsic mechanical properties. Both the CFL and CL are more compliant ligaments and seem to be involved in the development of subtalar instability. Based on the material properties, a gracilis tendon graft seems more appropriate than a synthetic ligament to reconstruct a CL or CFL. A partial rupture was the most commonly seen injury pattern in all ligaments. A fibular avulsion of the CFL was only rarely seen. The injury patterns need further investigation as they are important to optimize diagnosis and treatment.

Length change pattern of the ankle deltoid ligament during physiological ankle motion

BACKGROUND

Length change pattern of the ankle deltoid ligament during physiological ankle motion is still confused currently and had not been studied in vivo.

METHODS

The deltoid ligaments from 7 cadaveric specimens were dissected. Lengths of each band during 30° plantarflexion to 20° dorsiflexion were measured. A dual fluoroscopy imaging system was utilized to capture the images of hindfoot joint of 7 healthy subjects during the stance phase of walking. 3D bone models were reconstructed from CT images. Lengths of each band were calculated after model-image registration utilizing a solid modeling software. Percentage of length variation and poses when the bands were in maximum extension were documented among each band.

RESULTS

The anterior border of tibiocalcaneal ligament (TCL) had only 1.7% length variation in vitro and 5.7% length variation in vivo. The tibionavicular ligament, tibiospring ligament, and deep anterior tibiotalar ligament were in maximum extension at 30° plantarflexion, however, superficial posterior tibiotalar ligament, deep posterior tibiotalar ligament, and the posterior border of TCL were in maximum extension at 20° dorsiflexion. The tibionavicular ligament, tibiospring ligament, and deep anterior tibiotalar ligament were in maximum extension during foot flat. The TCL was in maximum extension during midstance. The superficial posterior tibiotalar ligament and deep posterior tibiotalar ligament were in maximum extension during heel off and toe off.

CONCLUSION

The length of TCL did not change during ankle dorsiflexion and plantarflexion. The bands anterior to and posterior to the TCL showed different length change pattern during physiological ankle dorsiflexion and plantarflexion.

Effects of the Ankle Flexion Angle During Anterior Talofibular Ligament Reconstruction on Ankle Kinematics, Laxity, and In Situ Forces of the Reconstructed Graft

BACKGROUND

This study aimed to evaluate the effects of the ankle flexion angle during anterior talofibular ligament (ATFL) reconstruction on ankle kinematics, laxity, and in situ force of a graft.

METHODS

Twelve cadaveric ankles were evaluated using a 6-degrees of freedom robotic system to apply passive plantar flexion and dorsiflexion motions and multidirectional loads. A repeated measures experiment was designed using the intact ATFL, transected ATFL, and reconstructed ATFL. During ATFL reconstruction (ATFLR), the graft was fixed at a neutral position (ATFLR 0 degrees), 15 degrees of plantar flexion (ATFLR PF15 degrees), and 30 degrees of plantar flexion (ATFLR PF30 degrees) with a constant initial tension of 10 N. The 3-dimensional path and reconstructed graft tension were simultaneously recorded, and the in situ force of the ATFL and reconstructed grafts were calculated using the principle of superposition.

RESULTS

The in situ forces of the reconstructed grafts in ATFLR 0 degrees and ATFLR PF 15 degrees were significantly higher than those of intact ankles. The ankle kinematics and laxity produced by ATFLR PF 30 degrees were not significantly different from those of intact ankles. The in situ force on the ATFL was 19.0 N at 30 degrees of plantar flexion. In situ forces of 41.0, 33.7, and 21.9 N were observed at 30 degrees of plantar flexion in ATFLR 0, 15, and 30 degrees, respectively.

CONCLUSION

ATFL reconstruction with the peroneus longus (PL) tendon was performed with the graft at 30 degrees of plantar flexion resulted in ankle kinematics, laxity, and in situ forces similar to those of intact ankles. ATFL reconstructions performed with the graft fixed at 0 and 15 degrees of the plantar flexion resulted in higher in situ forces on the reconstructed graft.

CLINICAL RELEVANCE

Fixing the ATFL tendon graft at 30 degrees of plantar flexion results in an in situ force closest to that of an intact ankle and avoids the excessive tension on the reconstructed graft.

Biomechanics of Medial Ankle and Peritalar Instability

The deltoid and spring ligaments are the primary restraints against pronation and valgus deformity of the foot, and in preserving the medial arch. The posterior tibial tendon has a secondary role in plantar arch maintenance, and its biomechanical stress increases considerably when other tissues fail. A thorough understanding of the anatomy and biomechanics of the deltoid-spring ligament is crucial for successful reconstruction of the tibiocalcanealnavicular ligament, hence, to restore ankle and medial peritalar stability. Although effective in correcting the deformity, tibionavicular tenodesis might be critical, as it blocks physiologic pronation of the hindfoot, which may result in dysfunction and pain.

Imaging Techniques for Assessment of Dynamically Unstable Sports Related Foot and Ankle Injuries

Foot and ankle instability can be seen both in acute and chronic settings, and isolating the diagnosis can be difficult. Imaging can contribute to the clinical presentation not only by identifying abnormal morphology of various supporting soft tissue structures but also by providing referring clinicians with a sense of how functionally incompetent those structures are by utilizing weight-bearing images and with comparison to the contralateral side. Loading the affected joint and visualizing changes in alignment provide clinicians with information regarding the severity of the abnormality and, therefore, how it should be managed.

Physical Examination of the Ankle: A Review of the Original Orthopedic Special Test Description and Scientific Validity of Common Tests for Ankle Examination

OBJECTIVES

To review the literature, identify and describe commonly used special tests for diagnosing injury to the ligaments of the ankle complex, present the distinguishing characteristics and limitations of each test, and discuss the current evidence for the clinical use of each test.

DATA SOURCES

Multiple PubMed (1920-2018) and CINAHL (1920-2018) searches were conducted and various musculoskeletal examination textbooks were reviewed to examine common orthopedic tests used to assess the ankle. The articles were reviewed for additional references and the search continued until the original description was found when possible.

STUDY SELECTION

All articles discussing the performance of the test or its validity (ie, sensitivity and specificity) were reviewed and summarized.

DATA EXTRACTION

Articles were reviewed for additional references and the search continued until the original description was found when possible.

DATA SYNTHESIS

The literature was reviewed, commonly used special tests for diagnosing ankle injuries were identified and described, distinguishing characteristics and limitations of each test were presented, and the current evidence for the clinical use of each test was discussed.

CONCLUSIONS

A complete physical examination is critical in the diagnosis of ankle injuries. The combination of available information such as mechanism of injury, all signs and symptoms, and changes in gait, is key to a conclusive and correct diagnosis. Clinicians should be aware of the severely limited evidence supporting the use of many commonly used special tests. Applying evidence from the literature will improve diagnostic accuracy. Further research is needed to understand the performance ability of special tests, both individually and when grouped as part of a test battery.

Influence of population variability in ligament material properties on the mechanical behavior of ankle: a computational investigation

Biomechanical behavior of ankle ligaments varies among individuals, with the underlying mechanism at multiple scales remaining unquantified. The present probabilistic study investigated how population variability in ligament material properties would influence the joint mechanics. A previously developed finite element ankle model with parametric ligament properties was used. Taking the typical external rotation as example loading scenario, joint stability of the investigated population was consistently shared by specific ligaments within a narrow tolerance range, i.e. 62.8 ± 8.2 Nm under 36.1 ± 5.7° foot rotation. In parallel, the inherent material variability significantly alters the consequent injury patterns. Three most vulnerable ligaments and the consequent rupture sequences were identified, with the structural weak spot and the following progressive stability loss dominated by the relative stiffness among ligaments. This study demonstrated the feasibility of biofidelic models in investigating individual difference at the material level, and emphasized the importance of probabilistic description of individual difference when identifying the injury mechanism of a broad spectrum.

Reliability of ultrasonography measurement of the anterior talofibular ligament (ATFL) length in healthy subjects (in vivo), based on examiner experience and patient positioning

BACKGROUND

The most common cause of ankle injury is the supination trauma, inflicting a partial or complete rupture of the anterior talofibular ligament (ATFL). Among conventional diagnostic tools and procedures of sports injuries, the method of stress-ultrasonography is reportedly a promising diagnostic tool for examining injuries of the lateral ligaments of the ankle. Preceding studies predominantly examined the comparability of stress-ultrasonography and other established diagnostic tools in terms of efficacy, viability and quality. The purpose of this study was to assess the reliability of stress-ultrasonography of the ATFL based on varying examiner experience and patient positioning.

METHOD

Sixteen healthy subjects were examined by four examiners with differing levels of skill and experience in ultrasonography, ranging from laymen to specialist. Measurements were recorded and interrater correlation coefficient (ICC) was applied in four positions, including a neutral position (A), medial rotation (B), plantar flexion (C) and inversion of the foot (D).

RESULTS

The length of the ATFL was 14.958 ± 2.145 mm in position A, 15.886 ± 1.994 mm in position B, 16.270 ± 1.858 mm in position C and 15.170 ± 1.781 mm in position D. The average length change was 0.928 ± 0.804 mm (6.656 ± 6.299%) in position B, 1.313 ± 1.266 mm (9.746 ± 9.484%) in position C and 0.213 ± 1.807 mm (2.604 ± 12.308%) in position D. The correlation of the combined results of all four investigators was 0.333 for position A, 0.386 for position B, 0.320 for position C and 0.517 for position D. The highest ICC (0.811) was recorded between the orthopedic specialist and the radiology specialist. The lowest ICC (0.299) was recorded between the laymen and the radiology specialist.

CONCLUSION

The reliability of the ATFL examination seems to be exceedingly dependent on the examiner's experience and skill in ultrasonographic (US) diagnostic. Moreover, the inversion positioning of the foot, described by the European Society of Musculoskeletal Radiology (ESSR) yielded the highest measurement reliability.

Morphological evaluation of the calcaneofibular ligament in different ankle positions using a three-dimensional MRI sequence

PURPOSE

Evaluating images of the lateral ligament of the ankle is not easy, and evaluation of the calcaneofibular ligament (CFL) in particular is difficult. We prospectively conducted morphological measurements of the CFL in different ankle positions and obtain basic data for use in functional assessment of the CFL, diagnosis of CFL injury, and determination of treatment effects.

METHODS

The subjects were ten healthy volunteers (ten ankles) with a mean age of 27.8 years and no history of ankle disease. Imaging was done using a 3-T magnetic resonance imaging (MRI) machine and fast imaging employing steady-state acquisition cycled phases (FIESTA-C), a three-dimensional (3D) sequence, with the ankle in a neutral position, maximum dorsiflexion, and maximum plantar flexion. 3D images of the CFL, peroneal muscle tendons, fibula, and calcaneus were prepared at a workstation, and morphological measurements of the CFL were made.

RESULTS

In all positions, the CFL showed a gently curving course with the peroneal muscle tendons as a fulcrum. The tortuosity angle was significantly smaller in plantar flexion (30.0° ± 7.4°) than in the neutral position (41.7° ± 8.3°).

CONCLUSIONS

3D MRI sequences showed that, in all positions, the CFL curved due to the influence of the peroneal muscle tendons. With maximum plantar flexion, the CFL tortuosity angle was small, which was thought to have been due to the tension in the CFL.

Propagation of Syndesmotic Injuries During Forced External Rotation in Flexed Cadaveric Ankles

Background

Forced external rotation of the foot is a mechanism of ankle injuries. Clinical observations include combinations of ligament and osseous injuries, with unclear links between causation and injury patterns. By observing the propagation sequence of ankle injuries during controlled experiments, insight necessary to understand risk factors and potential mitigation measures may be gained.

Hypothesis

Ankle flexion will alter the propagation sequence of ankle injuries during forced external rotation of the foot.

Study Design

Controlled laboratory study.

Methods

Matched-pair lower limbs from 9 male cadaveric specimens (mean age, 47.0 ± 11.3 years; mean height, 178.1 ± 5.9 cm; mean weight, 94.4 ± 30.9 kg) were disarticulated at the knee. Specimens were mounted in a test device with the proximal tibia fixed, the fibula unconstrained, and foot translation permitted. After adjusting the initial ankle position (neutral, n = 9; dorsiflexed, n = 4; plantar flexed, n = 4) and applying a compressive preload to the tibia, external rotation was applied by rotating the tibia internally while either lubricated anteromedial and posterolateral plates or calcaneal fixation constrained foot rotation. The timing of osteoligamentous injuries was determined from acoustic sensors, strain gauges, force/moment readings, and 3-dimensional bony kinematics. Posttest necropsies were performed to document injury patterns.

Results

A syndesmotic injury was observed in 5 of 9 (56%) specimens tested in a neutral initial posture, in 100% of the dorsiflexed specimens, and in none of the plantar flexed specimens. Superficial deltoid injuries were observed in all test modes.

Conclusion

Plantar flexion decreased and dorsiflexion increased the incidence of syndesmotic injuries compared with neutral matched-pair ankles. Injury propagation was not identical in all ankles that sustained a syndesmotic injury, but a characteristic sequence initiated with injuries to the medial ligaments, particularly the superficial deltoid, followed by the propagation of injuries to either the syndesmotic or lateral ligaments (depending on ankle flexion), and finally to the interosseous membrane or the fibula.

Clinical Relevance

Superficial deltoid injuries may occur in any case of hyper-external rotation of the foot. A syndesmotic ankle injury is often concomitant with a superficial deltoid injury; however, based on the research detailed herein, a deep deltoid injury is then concomitant with a syndesmotic injury or offloads the syndesmosis altogether. A syndesmotic ankle injury more often occurs when external rotation is applied to a neutral or dorsiflexed ankle. Plantar flexion may shift the injury to other ankle ligaments, specifically lateral ligaments.

[Injuries of the medial collateral ligament and spring ligament complexes]

The medial collateral ligament (MCL) complex is characterized by a complex anatomical arrangement of the individual ligamentous structures including three joints and the spring ligament complex. Biomechanically it serves as the main stabilizing structure in the ankle region against rotational and pronating forces. Lesions in the region of the MCL complex are more frequent than previously thought and like lesions of the spring ligament complex can lead to pain and instability. A thorough examination including the patient history with possible injury mechanisms often yields valuable information on the diagnosis of injuries to the MCL or spring ligament complex. In many cases these are primarily overlooked and concomitant lesions, such as fractures, syndesmotic and lateral ligament lesions frequently occur; however, the clinical assessment of stability is often primarily impossible in an acute setting. High-resolution magnetic resonance imaging (MRI) plays a key role in identifying the ligamentous components. In addition, MRI plays a supportive role in the preoperative planning before reconstruction of acute and especially chronic lesions. In most cases the surgical treatment of acute ruptures of the MCL is not indicated. Various options for treatment of acute and chronic lesions of the MCL and spring ligament complex are available including the use of free tendon grafts. Controversy exists regarding the operative treatment of MCL lesions in the case of ankle fractures. It is recommended for cases with impinging tissue in the medial gutter serving as a barrier to adequate reduction of the joint and in cases of unstable fractures after reduction.

Achilles tendon moment arm in humans is not affected by inversion/eversion of the foot: a short report

The triceps surae primarily acts as plantarflexor of the ankle joint. However, the group also causes inversion and eversion at the subtalar joint. Despite this, the Achilles tendon moment arm is generally measured without considering the potential influence of inversion/eversion of the foot during plantarflexion. This study investigated the effect of foot inversion and eversion on the plantarflexion Achilles tendon moment arm. Achilles tendon moment arms were determined using the centre-of-rotation method in magnetic resonance images of the left ankle of 11 participants. The foot was positioned at 15° dorsiflexion, 0° or 15° plantarflexion using a Styrofoam wedge. In each of these positions, the foot was either 10° inverted, neutral or 10° everted using an additional Styrofoam wedge. Achilles tendon moment arm in neutral foot position was 47.93 ± 4.54 mm and did not differ significantly when the foot was positioned in 10° inversion and 10° eversion. Hence, inversion/eversion position of the foot may not considerably affect the length of the Achilles tendon moment arm. This information could be useful in musculoskeletal models of the human lower leg and foot and when estimating Achilles tendon forces during plantarflexion with the foot positioned in inversion or eversion.

Transient and long-time kinetic responses of the cadaveric leg during internal and external foot rotation

The purpose of this study was to determine the long-time and transient characteristics of the moment generated by external (ER) and internal (IR) rotation of the calcaneus with respect to the tibia. Two human cadaver legs were disarticulated at the knee joint while maintaining the connective tissue between the tibia and fibula. An axial rotation of 21° was applied to the proximal tibia to generate either ER or IR while the fibula was unconstrained and the calcaneus was permitted to translate in the transverse plane. These boundary conditions were intended to allow natural motion of the fibula and for the effective applied axis of rotation to move relative to the ankle and subtalar joints based on natural articular motions among the tibia, fibula, talus, and calcaneus. A load cell at the proximal tibia measured all components of force and moment. A quasi-linear model of the moment along the tibia axis was developed to determine the transient and long-time loads generated by this ER/IR. Initially neutral, everted, inverted, dorsiflexed, and plantarflexed foot orientations were tested. For the neutral position, the transient elastic moment was 16.5N-m for one specimen and 30.3N-m for the other in ER with 26.3 and 32.1N-m in IR. The long-time moments were 5.5 and 13.2N-m (ER) and 9.0 and 9.5N-m (IR). These loads were found to be transient over time similar to previous studies on other biological structures where the moment relaxed as time progressed after the initial ramp in rotation.

Determination of the in situ mechanical behavior of ankle ligaments

The mechanical behavior of ankle ligaments at the structural level can be characterized by force-displacement curves in the physiologic phase up to the initiation of failure. However, these properties are difficult to characterize in vitro due to the experimental difficulties in replicating the complex geometry and non-uniformity of the loading state in situ. This study used a finite element parametric modeling approach to determine the in situ mechanical behavior of ankle ligaments at neutral foot position for a mid-sized adult foot from experimental derived bony kinematics. Nine major ankle ligaments were represented as a group of fibers, with the force-elongation behavior of each fiber element characterized by a zero-force region and a region of constant stiffness. The zero-force region, representing the initial tension or slackness of the whole ligament and the progressive fiber uncrimping, was identified against a series of quasi-static experiments of single foot motion using simultaneous optimization. A range of 0.33-3.84mm of the zero-force region was obtained, accounting for a relative length of 6.7±3.9%. The posterior ligaments generally exhibit high-stiffness in the loading region. Following this, the ankle model implemented with in situ ligament behavior was evaluated in response to multiple loading conditions and proved capable of predicting the bony kinematics accurately in comparison to the cadaveric response. Overall, the parametric ligament modeling demonstrated the feasibility of linking the gross structural behavior and the underlying bone and ligament mechanics that generate them. Determination of the in situ mechanical properties of ankle ligaments provides a better understanding of the nonlinear nature of the ankle joint. Applications of this knowledge include functional ankle joint mechanics and injury biomechanics.

Novel stress radiography technique for avulsion fracture of the lateral malleolus in children: a report of three cases

This study reports a novel stress radiography technique to evaluate an avulsion fracture at the lateral malleolus in children. Radiographs in the stress anteroposterior view or the Haraguchi calcaneofibular ligament or anterior tarofibular ligament (ATFL) projection could not detect any fracture; only manual inversion stress radiography in the Haraguchi ATFL projection could identify the avulsion fracture.

Preventive lateral ligament tester (PLLT): a novel method to evaluate mechanical properties of lateral ankle joint ligaments in the intact ankle

PURPOSE

To construct and evaluate an ankle arthrometer that registers inversion joint deflection at standardized inversion loads and that, moreover, allows conclusions about the mechanical strain of intact ankle joint ligaments at these loads.

METHODS

Twelve healthy ankles and 12 lower limb cadaver specimens were tested in a self-developed measuring device monitoring passive ankle inversion movement (Inv-ROM) at standardized application of inversion loads of 5, 10 and 15 N. To adjust in vivo and in vitro conditions, the muscular inactivity of the evertor muscles was assured by EMG in vivo. Preliminary, test-retest and trial-to-trial reliabilities were tested in vivo. To detect lateral ligament strain, the cadaveric calcaneofibular ligament was instrumented with a buckle transducer. After post-test harvesting of the ligament with its bony attachments, previously obtained resistance strain gauge results were then transferred to tensile loads, mounting the specimens with their buckle transducers into a hydraulic material testing machine.

RESULTS

ICC reliability considering the Inv-ROM and torsional stiffness varied between 0.80 and 0.90. Inv-ROM ranged from 15.3° (±7.3°) at 5 N to 28.3° (±7.6) at 15 N. The different tests revealed a CFL tensile load of 31.9 (±14.0) N at 5 N, 51.0 (±15.8) at 10 N and 75.4 (±21.3) N at 15 N inversion load.

CONCLUSIONS

A highly reliable arthrometer was constructed allowing not only the accurate detection of passive joint deflections at standardized inversion loads but also reveals some objective conclusions of the intact CFL properties in correlation with the individual inversion deflections. The detection of individual joint deflections at predefined loads in correlation with the knowledge of tensile ligament loads in the future could enable more individual preventive measures, e.g., in high-level athletes.

A framework for parametric modeling of ankle ligaments to determine the in situ response under gross foot motion

Ligament sprains account for a majority of injuries to the foot and ankle complex, but ligament properties have not been understood well due to the difficulties in replicating the complex geometry, in situ stress state, and non-uniformity of the strain. For a full investigation of the injury mechanism, it is essential to build up a foot and ankle model validated at the level of bony kinematics and ligament properties. This study developed a framework to parameterize the ligament response for determining the in situ stress state and heterogeneous force-elongation characteristics using a finite element ankle model. Nine major ankle ligaments and the interosseous membrane were modeled as discrete elements corresponding functionally to the ligamentous microstructure of collagen fibers and having parameterized toe region and stiffness at the fiber level. The range of the design variables in the ligament model was determined from existing experimental data. Sensitivity of the bony kinematics to each variable was investigated by design of experiment. The results highlighted the critical role of the length of the toe region of the ligamentous fibers on the bony kinematics with the cumulative influence of more than 95%, while the fiber stiffness was statistically insignificant with an influence of less than 1% under the given variable range and loading conditions. With the flexibility of variable adjustment and high computational efficiency, the presented ankle model was generic in nature so as to maximize its applicability to capture the individual ligament behaviors in future studies.

Muscle Reaction Time During a Simulated Lateral Ankle Sprain After Wet-Ice Application or Cold-Water Immersion

CONTEXT

Cryotherapy is used widely in sport and exercise medicine to manage acute injuries and facilitate rehabilitation. The analgesic effects of cryotherapy are well established; however, a potential caveat is that cooling tissue negatively affects neuromuscular control through delayed muscle reaction time. This topic is important to investigate because athletes often return to exercise, rehabilitation, or competitive activity immediately or shortly after cryotherapy.

OBJECTIVE

To compare the effects of wet-ice application, cold-water immersion, and an untreated control condition on peroneus longus and tibialis anterior muscle reaction time during a simulated lateral ankle sprain.

DESIGN

Randomized controlled clinical trial.

SETTING

University of Hertfordshire human performance laboratory.

PATIENTS OR OTHER PARTICIPANTS

A total of 54 physically active individuals (age = 20.1 ± 1.5 years, height = 1.7 ± 0.07 m, mass = 66.7 ± 5.4 kg) who had no injury or history of ankle sprain.

INTERVENTION(S)

Wet-ice application, cold-water immersion, or an untreated control condition applied to the ankle for 10 minutes.

MAIN OUTCOME MEASURE(S)

Muscle reaction time and muscle amplitude of the peroneus longus and tibialis anterior in response to a simulated lateral ankle sprain were calculated. The ankle-sprain simulation incorporated a combined inversion and plantar-flexion movement.

RESULTS

We observed no change in muscle reaction time or muscle amplitude after cryotherapy for either the peroneus longus or tibialis anterior (P > .05).

CONCLUSIONS

Ten minutes of joint cooling did not adversely affect muscle reaction time or muscle amplitude in response to a simulated lateral ankle sprain. These findings suggested that athletes can safely return to sporting activity immediately after icing. Further evidence showed that ice can be applied before ankle rehabilitation without adversely affecting dynamic neuromuscular control. Investigation in patients with acute ankle sprains is warranted to assess the clinical applicability of these interventions.

Residual mechanical effectiveness of external ankle tape before and after competitive professional soccer performance

OBJECTIVE

To evaluate the presupposed preventive residual mechanical effectiveness of the widespread use of adhesive elastic ankle tape after a nonlaboratory, realistic soccer-specific outfield intervention reflecting a soccer halftime.

DESIGN

A prospective nonrandomized test-retest design was used.

SETTING

Laboratory.

PARTICIPANTS

Seventeen professional male outfield players (mean age, 25.5) without any signs of chronic ankle instability.

INTERVENTION

Participants were investigated before and after a 45-minute soccer-specific field intervention.

MAIN OUTCOME MEASURES

The passive inversion range of motion (ROM) of the ankle was tested unloaded on a self-developed inversion device with and without a standardized ankle tape before and after the intervention. Additionally, electromyography signal was taken to assure the inactivity of the protective evertor muscles, and reliability tests for the inversion device (test-retest and trial to trial) were conducted in 12 healthy controls.

RESULTS

Tape restricted the maximum passive inversion ROM of the uninjured ankle significantly to 50.3%. The protection declined nearly completely after 45 minutes of outfield soccer performance to a negligible nonsignificant ROM restriction of 9.7%. Pearson correlation coefficient for the reliability was 0.931 (P ≤ 0.001) for the test-retest and 0.983 (P ≤ 0.001) for the trial-to-trial test.

CONCLUSIONS

The initial significant protection of external ankle-tape support declines almost completely without relevant remaining residual mechanical effect after 45 minutes, reflecting a soccer halftime. The so far presupposed residual mechanical effectiveness of tape to prevent injury is increasingly irrelevant during soccer performance and consequently antidromic to the increasing injury risk toward the end of a soccer halftime.

The jump shot - a biomechanical analysis focused on lateral ankle ligaments

Handball is one of the top four athletic games with highest injury risks. The jump shot is the most accomplished goal shot technique and the lower extremities are mostly injured. As a basis for ankle sprain simulation, the aim of this study was to extend the ankle region of an existing musculoskeletal full-body model through incorporation of three prominent lateral ankle ligaments: ligamentum fibulotalare anterius (LFTA), ligamentum fibulotalare posterius (LFTP), ligamentum fibulocalcaneare (LFC). The specific objective was to calculate and visualise ligament force scenarios during the jumping and landing phases of controlled jump shots. Recorded kinematic data of performed jump shots and the corresponding ground reaction forces were used to perform inverse dynamics. The calculated peak force of the LFTA (107 N) was found at maximum plantarflexion and of the LFTP (150 N) at maximum dorsiflexion. The peak force of the LFC (190 N) was observed at maximum dorsiflexion combined with maximum eversion. Within the performed jump shots, the LFTA showed a peak force (59 N to 69 N) during maximum plantarflexion in the final moment of the lift off. During landing, the force developed by the LFTA reached its peak value (61 N to 70 N) at the first contact with the floor. After that, the LFTP developed a peak force (70 N to 118 N). This model allows the calculation of forces in lateral ankle ligaments. The information obtained in this study can serve as a basis for future research on ankle sprain and ankle sprain simulation.

A composite athletic tape with hyperelastic material properties improves and maintains ankle support during exercise

STUDY DESIGN

Controlled laboratory testing using a single-group, prospective, repeated-measures design.

OBJECTIVES

To compare the material properties of a hyperelastic athletic tape to a conventional tape and to compare the passive ankle support of these tapes before and after exercise.

BACKGROUND

The near-linear material properties of conventional athletic tape may interfere with ankle motion, resulting in reduced athletic performance. Conventional athletic tape is also known to lose much of its initial support during exercise. It was assumed that a tape constructed of Kevlar fibers embedded in a silicon matrix would possess hyperelastic material properties that would improve ankle support.

METHODS

A tensile testing machine was used to determine the tensile material properties of 11 samples of conventional and hyperelastic tape. The ankles of 11 young, healthy athletes were taped, one ankle with conventional tape and the other ankle with hyperelastic tape. The passive ankle support of each tape was measured with an instrumented linkage (the ankle flexibility tester) before and after 30 minutes of exercise.

RESULTS

The composite tape had a significantly higher load to failure than the conventional tape. It had significantly lower initial stiffness and higher late stiffness than conventional tape, thus demonstrating highly hyperelastic behavior. The hyperelastic tape maintained a significantly higher portion of its support during the 30 minutes of exercise than the conventional tape.

CONCLUSIONS

Composite athletic tape with highly hyperelastic properties can be constructed and maintains a larger portion of its support during short-duration exercises (less than 30 minutes) than conventional athletic tape.

Effects of surgical correction for the treatment of adult acquired flatfoot deformity: a computational investigation

Computational models of the foot/ankle complex were developed to predict the biomechanical consequences of surgical procedures that correct for stage II adult acquired flatfoot deformity. Cadaveric leg and foot bony anatomy was captured by CT imaging in neutral flexion and imported to the modeling software. Ligaments were approximated as tension only springs attached at insertion sites. Muscle contraction of the gastrocnemius/soleus complex was simulated through force vectors and desired external loads applied to the model. Ligament stiffnesses were modified to reflect stage II flatfoot damage, followed by integration of corrective osteotomies-medializing calcaneal osteotomy (MCO) and Evans and calcaneocuboid distraction arthrodesis (CCDA)--to treat flatfoot. Joint angles, tissue strains, calcaneocuboid contact force, and plantar loads were analyzed. The flatfoot simulation demonstrated clinical signs of disease evidenced by degradation of joint alignment. Repair states corrected these joint misalignments with MCO having greatest impact in the hindfoot, and Evans/CCDA having greatest effect in the mid- and forefoot. The lateral procedures unevenly strained plantar structures, while offloading the medial forefoot, and increased loading on the lateral forefoot, which was amplified by combining with MCO. The Evans procedure raised calcaneocuboid joint contact force to twice intact levels. Computational results are in agreement with clinical and experimental findings. The model demonstrated potential precursors to such complications as lateral tightness and arthritic development and may thus be useful as a predictor of surgical outcomes.

Determination of optimal screw positioning in flexor hallucis longus tendon transfer for chronic tendoachilles rupture

BACKGROUND

Neglected ruptures of the tendoachilles pose a difficult surgical problem. There are no data to determine the optimal positioning of the FHL tendon to the calcaneus.

METHODS

Two computer programmes (MSC.visualNastran Desktop 2002™ and Solid Edge(®) V19) were used to generate a human ankle joint model. Different attachment points of FHL tendon transfer to the calcaneus were investigated.

RESULTS

The lowest muscle force to produce plantarflexion (single stance heel rise) was 1355 N. Plantarflexion increased for a more anterior attachment point. The maximum range of plantarflexion was 33.4° for anterior attachment and 24.4° for posterior attachment. There was no significant difference in range of movement when the attachment point was moved to either a medial or lateral position.

CONCLUSIONS

A more posterior attachment point is advantageous in terms of power and the arc of motion (24.4°) is physiological. We recommend that FHL is transferred to the calcaneus in a posterior position.

The relation between geometry and function of the ankle joint complex: a biomechanical review

This review deals with the relation between the anatomy and function of the ankle joint complex. The questions addressed are how high do the forces in the ankle joint get, where can the joints go (range of motion) and where do they go during walking and running. Finally the role of the ligaments and the articular surfaces is discussed, i.e. how does it happen. The magnitude of the loads on the ankle joint complex are primarily determined by muscle activity and can be as high as four times the body weight during walking. For the maximal range of motion, plantar and dorsiflexion occurs in the talocrural joint and marginally at the subtalar joint. In-eversion takes place at both levels. The functional range of motion is well within the limits of the maximal range of motion. The ligaments do not contribute to the forces for the functional range of motion but determine the maximal range of motion together with the articular surfaces. The geometry of the articular surfaces primarily determines the kinematics. Clinical studies must include these anatomical aspects to better understand the mechanism of injury, recovery, and interventions. Models can elucidate the mechanism by which the anatomy relates to the function. The relation between the anatomy and mechanical properties of the joint structures and joint function should be considered for diagnosis and treatment of ankle joint pathology.

Computational Model of the Lower Leg and Foot/Ankle Complex: Application to Arch Stability

The aim of this work was the design and evaluation of a computational model to predict the functional behavior of the lower leg and foot/ankle complex whereby joint behavior was dictated by three-dimensional articular contact, ligamentous constraints, muscle loading, and external perturbation. Three-dimensional bony anatomy was generated from stacked CT images after which ligament mimicking elements were attached and muscle/body loading added to recreate the experimental conditions of selected cadaveric studies. Comparisons of model predictions to results from two different experimental studies were performed for the function of the medial arch in weight bearing stance and the contributions of soft tissue structures to arch stability. Sensitivity simulations evaluated selected in situ strain and stiffness values for ligament tissue. The greatest contributor to arch stability was the plantar fascia, which provided 79.5% of the resistance to arch collapse, followed by the plantar ligaments (12.5%), and finally the spring ligament (8.0%). Strains measured after plantar fasciotomy increased in the remaining plantar ligament by ∼300% and spring ligament by ∼200%. Sensitivity tests varying both in situ strain and stiffness across reported standard deviations showed that functional trends remained the same and true to experimental data, although absolute magnitudes changed. While not measured experimentally, the model also predicted that load can increase dramatically in the remaining plantar tissues when one of such tissues is removed. Overall, computational predictions of stability and soft tissue load sharing compared well with experimental findings. The strength of this simulation approach lies in its capacity to predict biomechanical behavior of modeled structures and to capture physical parameters of interest not measurable in experimental simulations or in vivo.

Understanding acute ankle ligamentous sprain injury in sports

This paper summarizes the current understanding on acute ankle sprain injury, which is the most common acute sport trauma, accounting for about 14% of all sport-related injuries. Among, 80% are ligamentous sprains caused by explosive inversion or supination. The injury motion often happens at the subtalar joint and tears the anterior talofibular ligament (ATFL) which possesses the lowest ultimate load among the lateral ligaments at the ankle. For extrinsic risk factors to ankle sprain injury, prescribing orthosis decreases the risk while increased exercise intensity in soccer raises the risk. For intrinsic factors, a foot size with increased width, an increased ankle eversion to inversion strength, plantarflexion strength and ratio between dorsiflexion and plantarflexion strength, and limb dominance could increase the ankle sprain injury risk. Players with a previous sprain history, players wearing shoes with air cells, players who do not stretch before exercising, players with inferior single leg balance, and overweight players are 4.9, 4.3, 2.6, 2.4 and 3.9 times more likely to sustain an ankle sprain injury. The aetiology of most ankle sprain injuries is incorrect foot positioning at landing – a medially-deviated vertical ground reaction force causes an explosive supination or inversion moment at the subtalar joint in a short time (about 50 ms). Another aetiology is the delayed reaction time of the peroneal muscles at the lateral aspect of the ankle (60–90 ms). The failure supination or inversion torque is about 41–45 Nm to cause ligamentous rupture in simulated spraining tests on cadaver. A previous case report revealed that the ankle joint reached 48 degrees inversion and 10 degrees internal rotation during an accidental grade I ankle ligamentous sprain injury during a dynamic cutting trial in laboratory. Diagnosis techniques and grading systems vary, but the management of ankle ligamentous sprain injury is mainly conservative. Immobilization should not be used as it results in joint stiffness, muscle atrophy and loss of proprioception. Traditional Chinese medicine such as herbs, massage and acupuncture were well applied in China in managing sports injuries, and was reported to be effective in relieving pain, reducing swelling and edema, and restoring normal ankle function. Finally, the best practice of sports medicine would be to prevent the injury. Different previous approaches, including designing prophylactice devices, introducing functional interventions, as well as change of games rules were highlighted. This paper allows the readers to catch up with the previous researches on ankle sprain injury, and facilitate the future research idea on sport-related ankle sprain injury.

Biomechanical comparison of the interosseous tibiofibular ligament and the anterior tibiofibular ligament

BACKGROUND

The mechanical importance of the interosseous tibiofibular ligament of the ankle is unclear. The purpose of the current study was to compare the stiffness and strength of the interosseous tibiofibular ligament to that of the anterior tibiofibular ligament.

METHODS

Twelve pairs of ankles were obtained from the Maryland State Anatomy Board. All soft tissue was removed except for the interosseous tibiofibular ligament in one ankle of each pair and the anterior tibiofibular ligament in the contralateral ankle. The assignment of which ligament would be excised in the right or left ankle of each pair was random. The specimens were potted as bone-ligament-bone preparations and mounted in a servohydraulic testing machine so that the ligament's long axis was coincident with the actuator. Specimens were elongated at 0.5 mm/s until rupture. Failure load and failure site were recorded, and stiffness was calculated. Stiffness and failure loads were compared with a paired t-test. Significance was set at p < 0.05.

RESULTS

The interosseous ligament was significantly stiffer (234 +/- 122 N/mm) than the anterior tibiofibular ligament (162 +/- 64 N/mm). The mean failure load of the interosseous tibiofibular ligament (822 +/- 298 N) was significantly greater than that of the anterior tibiofibular ligament (625 +/- 255 N).

CONCLUSIONS

The interosseous tibiofibular ligament is stiffer and stronger than the anterior tibiofibular ligament. CLINICAL RELEVANCE. The current study suggests that the interosseous ligament plays an important role in the stability of the ankle, and its status should be part of the diagnostic evaluation in syndesmotic instability.

Periosteal repair of the dorsal calcaneocuboid ligament: a comparative biomechanical study

BACKGROUND

Isolated lateral calcaneocuboid joint instability rarely is described. Missed or delayed diagnosis resulting in inadequate treatment may lead to chronic instability, followed by sports inability and handicap in daily life. Besides arthrodesis, anatomic repair augmenting the elongated dorsal calcaneocuboid ligament with a local periosteal flap has recently been described for treatment.

METHODS

In a controlled laboratory study, eight isolated fresh-frozen human cadaver calcaneocuboid specimens were strained in a varus direction until failure of the dorsal calcaneocuboid ligaments. Then the dorsal calcaneocuboid ligaments were reconstructed with free periosteal flaps and tensile testing was repeated.

RESULTS

Compared to native dorsal calcaneocuboid ligaments, free single layer periosteal flap reconstructions were found to have inferior load to failure (-52%, p = 0,028), ultimate stress (-44%, p = 0.024), stiffness (-50%, p = 0.063), and strain energy density to failure (-37.5%, p = 0.111).

CONCLUSIONS

In vitro data demonstrate that isolated single-layer periosteal flap replacement offers inferior stability as compared to native dorsal calcaneocuboid ligaments. To obtain sufficient initial stability, the elongated native ligament should, therefore, be reefed and a single-layer periosteal flap augmentation should be added. This combined procedure can be recommended for stabilization of isolated chronic dorsolateral calcaneocuboid joint instability.

Ankle ligament tensile forces at the end points of passive circumferential rotating motion of the ankle and subtalar joint complex

BACKGROUND

Ankle ligament injuries and instability are commonly observed. Knowledge of the relationship between the foot position and tensile forces of the ankle ligaments could be useful for treatment of ankle ligament disorders. The aim of this study was to measure the tensile forces of the ankle ligaments at the end points of passive circumferential rotating motion of the ankle and subtalar joint complex in various foot positions.

METHODS

Ligament tensile forces of the anterior talofibular (ATF), calcaneofibular (CF), posterior talofibular (PTF), and tibiocalcaneal (TC) ligaments were measured simultaneously in eight cadaver specimens, with a force probe in each ligament in a custom-made ankle ligament testing device. Weights of 0.5 kg and 1 kg were applied to the foot through a loading arm to provide axial compression and a bending moment to the foot and ankle. The position of the loading arm was changed circumferentially in 10-degree increments.

RESULTS

Maximal tensile force in the ATF ligament was observed in supination with plantarflexion (108 +/- 62.8 N at 0.5 kg and 130 +/- 39.1 N at 1 kg). The maximal tensile force in the CF ligament was observed in pronation with plantarflexion (68 +/- 48.6 N at 0.5 kg and 135 +/- 92.9 N at 1 kg). The maximal tensile force in the PTF ligament was observed in dorsiflexion (131 +/- 80.1 N at 0.5 kg and 109 +/- 36.3 N at 1 kg). The maximal tensile force of the TC ligament was observed in pronation with plantarflexion (49.0 +/- 80.1 N at 0.5 kg and 67.4 +/- 69.6 N at 1 kg). Relatively high magnitudes of tensile force were observed in the ankle ligaments, and the peak forces were related to the anatomic position of individual ligaments.

CONCLUSIONS

The ATF ligament has an important role in the supination position in plantarflexion, CF and TC ligaments also are important for pronation in plantarflexion, and the PTF is an important stabilizer in dorsiflexion. This study provides baseline information for further research related to ligament instability and reconstruction operations.

Operative management of chronic ankle instability: plantaris graft

Precise knowledge of lateral ankle ligaments anatomy and biomechanics is mandatory for successful surgical reconstruction. The displayed reconstruction procedure fulfilled these requirements, and showed excellent clinical outcome. The described harvesting of the plantaris tendon at the proximal calf allows the use of a relatively long tendon autograft compared with the traditional harvesting procedure at the os calcis. Consequently, this procedure gives the surgeon a more efficient access to a local tendon autograft for numerous surgical procedures in the field of foot and ankle surgery.

Deltoid ligament injuries: diagnosis and management

The medial ligaments of the ankle are injured more often than generally believed. Complete deltoid ligament tears are occasionally seen in association with lateral malleolar fractures or bimalleolar fractures. Chronic deltoid ligament insufficiency can be seen in several conditions, including posterior tibial tendon disorder, trauma- and sports-related deltoid disruptions, and valgus talar tilting in patients who have a history of triple arthrodesis or total ankle arthroplasty. This article focuses on the anatomy and function of the medial ligaments of the ankle and establishes a rationale for the diagnosis and treatment of incompetent deltoid ligament.

Tensile engagement of the peri-ankle ligaments in stance phase

BACKGROUND

Development of reconstructive operative procedures to restore normal ankle kinematics after injury requires an understanding of the biomechanics of the ankle during gait. The contribution of the peri-ankle ligaments to ankle motion control is not yet well understood. Knowledge of the tensile engagement of the peri-ankle ligaments during stance phase is necessary to achieve physiologic motion patterns.

METHODS

Eleven fresh-frozen cadaver ankles were subjected to a dynamic loading sequence simulating the stance phase of normal level gait. Simultaneously, ligament strain was continuously monitored in the anterior talofibular, calcaneofibular, and posterior talofibular ligaments, as well as in the anterior, middle, and posterior superficial deltoid ligaments. Eight of these specimens underwent further quasi-static range-of-motion testing, where ligament tension recruitment was assessed at 30 degrees plantarflexion and 30 degrees dorsiflexion.

RESULTS

In the dynamic loading tests, none of the ligaments monitored showed a reproducible strain pattern indicating a role in ankle stabilization. However, in the extended range-of-motion tests, most ligaments were taut in plantarflexion or dorsiflexion.

CONCLUSIONS

A consistent combination of individual ligament strain patterns that principally control ankle motion was not identified; none of the ligaments studied were reproducibly recruited to be a primary stabilizing structure. The peri-ankle ligaments are likely to be secondary restraining structures that serve to resist motion to avoid extreme positions. Stance phase ankle motion appears to be primarily controlled by articular congruity, not by peri-ankle ligament tension.

Use of a Torque-Range-of-Motion device for objective differentiation of diabetic from normal feet in adults

BACKGROUND

The ability of the foot and ankle complex to act as an energy absorber is reflected in its viscoelastic properties. The Torque-Range-of-Motion (TROM) device was designed to provide an effective objective assessment of foot and ankle passive mechanical function. The hypothesis of this study was that mechanical parameters derived from passive TROM curves of otherwise normal feet of adults with diabetes would be significantly different from those of adults without diabetes.

METHODS

The TROM device is a single-degree-of-freedom hinge transducer system that is manually rotated through plantarflexion and dorsiflexion. The device was rotated manually with the muscles relaxed during a 50-second data acquisition period. A strain gauge provided the torque signal and a precision single-turn potentiometer provided plantarflexion-dorsiflexion angle to a two-channel portable data acquisition system. With the TROM device connected to a computer, input for instantaneous torque and range of motion was acquired and displayed as angle (degrees) versus torque (Newton-meters) on an output screen. The period provided sufficient data to average 16 to 20 cycles of motion. The study included 41 feet in adults without diabetes and 42 age-matched feet in adults with diabetes but no known foot problems.

RESULTS

For a probability level of.0001 there were significant differences in hysteresis area (normal: 91.1 +/- 46.9 Nm-deg and diabetic: 161.7 +/- 65.7 Nm-deg) and both dorsiflexion (normal: 0.4 +/- 0.1 Nm/deg and diabetic: 0.9 +/- 0.3 Nm/deg) and plantarflexion stiffness (normal: 0.3 +/- 0.1 Nm/deg and diabetic: 0.7 +/- 0.3 Nm/deg).

CONCLUSIONS

The feet of adults with diabetes absorb more energy during cyclic motion (thus must dissipate more energy per cycle) and are stiffer in the terminal regions (where muscle-tendon-ligament properties prevail) than are the feet of adults without diabetes. These results suggest that this passive TROM method may be a sensitive, objective measurement of the viscoelastic properties of the foot and ankle, which may be an early indicator of diabetic patients who are at risk for the development of foot problems.

Mechanical response of ankle ligaments at low loads

BACKGROUND

The aim of this study was to examine the mechanical behavior of human ankle ligaments at low forces. Predominantly, ankle ligaments have been studied under the auspices of ligament injury. While the mechanical properties of a ligament when tested to failure provide a basis for comparisons, the loads and displacement do not reflect normal physiologic loading.

METHODS

Eight fresh-frozen ankles (mean age 65) were dissected to expose the ligaments surrounding the talocrural joint. Eight ankle ligaments were studied and included: medially-anterior tibiotalar (ATTL), posterior tibiotalar (PTTL), tibiocalcaneal (TCL); laterally-anterior tibiofibular (ATiFL), posterior tibiofibular (PTiFL), anterior talofibular (ATFL), posterior talofibular (PTFL), and calcaneofibular (CFL). Stress relaxation tests were carried out at 30% and 10% strain. The peak load and area under the curve were assessed for all experiments.

RESULTS

Significant differences were found for the average peak loads of the elastic response between 30% and 10% strain for each ligament (p < .05). At 10% strain the relationship between the ligaments on the medial and lateral side revealed a Pearson R value of .991 (p = .087). No significant difference was found between the strain energies of the various ligaments (p > .05). The anterior talofibular ligament was found to possess similar relaxation results to the medial ligaments. The calcaneofibular ligament relaxed up to 10% more compared to the anterior talofibular for the same relaxation period. The mechanical testing was performed in uniaxial tension and did not consider off-axis loading that may occur in vivo during ankle motion.

CONCLUSIONS

The stress relaxation experiments revealed all ligaments to relax even when loaded to less than 5 N, reflecting the viscoelastic nature of ligaments. The stress relaxation results show that the anterior talofibular ligament does not relax to the same extent as the other lateral ligaments. Examining the properties of human ankle ligaments at low loads has revealed some new findings.

CLINICAL RELEVANCE

This study highlights the need to understand the synergistic effects of the ligaments. This is important for reconstruction and arthroplasty procedures.

Deltoid ligament integrity in lateral malleolar fractures: a comparative analysis of arthroscopic and radiographic assessments

Foot and ankle surgeons often rely on the medial clear space to evaluate competency of the deep deltoid ligament when evaluating ankle fractures. This investigation assesses the integrity of the deep deltoid ligament after lateral malleolar fracture by using direct arthroscopic visualization and medial clear-space separation on plain film radiographs. The objectives of this study were to test the reliability of medial clear-space separation and the Lauge-Hansen classification scheme in predicting deep deltoid rupture in displaced lateral malleolar fractures. The medial clear space was measured on injury radiographs of 40 patients with an isolated displaced lateral malleolar fracture who underwent open reduction and internal fixation. Injury radiographs were classified according to the Lauge-Hansen scheme. Direct arthroscopic visualization was used to evaluate the deep deltoid ligament under manual stress before fracture reduction. The mean preoperative medial clear space in patients with a deep deltoid rupture (n = 13) was 6.6 +/- 2.4 mm (range, 4 to 12 mm), and in patients without a deep deltoid rupture (n = 26), it was 4.0 +/- 1.0 mm (range, 2.5 to 6 mm) (P =.002, 2-sample t test). At an injury medial clear space > or =3 mm, the false positive rate for deltoid rupture was 88.5% (P =.54, Fisher's exact test). At > or =4 mm, the false positive rate was 53.6% (P =.007). All fractures were rotational injuries according to the Lauge-Hansen system. Three fractures were not classifiable; another 3 fractures showed deltoid ligament integrity opposite the expected finding. The results indicate that, in isolated displaced fractures of the lateral malleolus, radiographic widening of the medial clear space is not a reliable indicator for deep deltoid rupture. Some fractures considered stable by the Lauge-Hansen classification may require careful scrutiny to rule out deep deltoid injury.

Medial ankle instability

Medial instability is suspected on the basis of a patient's ankle feeling like it is "giving way," especially medially, when walking on uneven ground, downhill, or down stairs, pain at the anteromedial aspect of the ankle, and sometimes pain in the lateral ankle, especially during dorsiflexion of the foot. A history of a chronically unstable feeling that is manifested by recurrent injuries with pain, tenderness, and sometimes bruising over the medial and lateral ligaments, is considered to indicate combined medial and lateral instability that is believed to result in rotational instability of the talus in the ankle mortise. Pain on the medial gutter of the ankle and a valgus and pronation deformity of the foot are hallmarks of the disorder. The deformity typically can be corrected by the activation of the posterior tibial muscle. In contrast to stress radiographs, arthroscopy is a helpful diagnostic tool in verifying medial instability; it proved that the lateral ankle ligaments also can be involved. The treatment for symptomatic medial instability of the ankle might include reconstruction of all involved ligaments at the medial, and, if necessary, the lateral ankle. In the case of progressed foot deformity or bilateral long-standing valgus and pronation deformity of the foot, an additional calcaneal lengthening osteotomy might be considered. A classification of the instability into three types has been helpful for determining surgical treatment and the after treatment. This treatment concept provides high patient satisfaction and reliable clinical results.

A biomechanical evaluation of the tibiofibular and tibiotalar ligaments of the ankle

The purpose of this ex vivo biomechanical study was to determine the strength and stiffness of the anterior and posterior syndesmotic tibiofibular ligaments and the posterior tibiotalar component of the deltoid ligament. Injuries to these ligaments are a prevalent clinical problem, yet little is known about their mechanical behavior. Ten fresh-frozen cadaver lower extremities (average age at death, 72 +/- 8 years) were harvested. The anterior and posterior tibiofibular ligaments and the posterior tibiotalar component of the deltoid were isolated and prepared as bone-ligament-bone complexes for tensile testing to determine strength, stiffness, and mode of failure. The posterior tibiofibular ligament exhibited greater strength, but not significantly so (p < .05), than the anterior tibiofibular ligament and the posterior tibiotalar component of the deltoid ligament. There were no significant differences in stiffness between the three ligaments tested. The dominant mode of failure for the anterior tibiofibular ligament was ligament substance rupture, primarily near its fibular insertion, whereas the failure modes of the posterior tibiofibular ligament were evenly split between substance ruptures and fibular avulsions. The posterior tibiotalar component of the deltoid ligament ruptured most often near the talar insertion. The tibiofibular ligaments showed greater strength than the lateral collateral and deltoid ligaments, as mentioned in literature. The greater strength of the tibiofibular ligaments relative to the lateral collateral and deltoid ligaments suggests that these ligaments play an important role in ankle constraint.

Inversion injury biomechanics in functional ankle instability: a cadaver study of simulated gait

The purpose of this study was to test pathogenetic models for the "unprovoked" ankle inversion injuries seen in functional ankle unstable subjects. The consequence of spatial mal-alignment of the ankle/foot complex on the risk of producing an ankle inversion torque at heel-strike and during swing-phase follow through was analyzed in cadaver simulations. Heel-strike was simulated using a 5 degrees of freedom rig in a material testing machine. A set-up capable of accelerating lower limb specimens towards a support surface simulated swing-phase follow through. Joint excursions were monitored with flexible wire goniometers. The unloaded ankle/foot complex was placed in increasing positions of talar and subtalar joint excursions. The consequences of these settings on the behavior of the ankle/foot complex at heel-strike and when the lateral part of the foot "caught" the ground during swing-phase follow through were monitored. An inversion torque at heel-strike was first seen when the unloaded foot was set in positions exceeding 30 degrees of inversion combined with full plantar flexion and 10 degrees of internal tibial rotation. A collision between the lateral border of a 20 degrees inverted, but otherwise neutral ankle/foot complex and the ground surface during swing-phase follow through forced the foot into the full limit of inversion, plantar flexion and internal tibial rotation measurable in this set-up. Clinical consequence: The study showed that the foot/ankle complex exhibits a high degree of intrinsic stability at heel-strike. The foot will thus stabilize itself and move into normal eversion at the beginning of the stance-phase even though it is set to the ground in a substantial degree of mal-alignment. In contrast, the swing-phase collision model provides a link that can connect the small deficits in inversion angle awareness measured in chronic functional ankle unstable subjects with an increased risk in this group of sustaining ankle inversion injuries.

The effects of axial preload and dorsiflexion on the tolerance of the ankle/subtalar joint to dynamic inversion and eversion

Forced inversion or eversion of the foot is considered a common mechanism of ankle injury in vehicle crashes. The objective of this study was to model empirically the injury tolerance of the human ankle/subtalar joint to dynamic inversion and eversion under three different loading conditions: neutral flexion with no axial preload, neutral flexion with 2 kN axial preload, and 30 degrees of dorsiflexion with 2 kN axial preload. 44 tests were conducted on cadaveric lower limbs, with injury occurring in 30 specimens. Common injuries included malleolar fractures, osteochondral fractures of the talus, fractures of the lateral process of the talus, and collateral ligament tears, depending on the loading configuration. The time of injury was determined either by the peak ankle moment or by a sudden drop in ankle moment that was accompanied by a burst of acoustic emission. Characteristic moment-angle curves to injury were generated for each loading configuration. Neutrally flexed ankles with no applied axial preload sustained injury at 21 +/- 5 Nm and 38 degrees +/- 8 degrees in inversion, and 47 +/- 21 Nm and 28 degrees +/- 4 degrees in eversion. For ankles tested in neutral flexion with 2 kN of axial preload, inversion failure occurred at 77 +/- 27 Nm and 40 degrees +/- 12 degrees , and eversion failure occurred at 142 +/- 100 Nm and 41 degrees +/- 14 degrees . Ankles dorsiflexed 30 degrees and axially preloaded to 2 kN sustained inversion injury at 62 +/- 31 Nm and 33 degrees +/- 4 degrees , and eversion injury at 140 +/- 53 Nm and 40 degrees +/- 6 degrees . Survival analyses were performed to generate injury risk curves in terms of joint moment and rotation angle.

Simultaneous strain measurement with determination of a zero strain reference for the medial and lateral ligaments of the ankle

The strain changes of the central part of the anterior talofibular ligament (ATFL), the posterior talofibular ligament (PTFL), the calcaneofibular ligament (CFL), and the tibiocalcaneal ligament (TCL) were measured simultaneously for a full range of ankle motion. Twelve fresh frozen amputated ankles were used. To measure the strain changes of the ligaments, a Galium-Indium-filled silastic strain transducer was implanted in the center of each ligament. The zero strain reference was determined immediately after the measurement of strain changes in five of the 12 ankles by tensile testing of each bone-ligament-bone preparation. The maximum strain change of the ATFL, the PTFL, the CFL and the TFL were 7.9%, 5.9%, 5.3% and 5.2%, respectively. The ATFL was elongated in plantar flexion and shortened in dorsiflexion. The PTFL and the CFL were shortened in plantar flexion and elongated in dorsiflexion. The TCL was the longest around the neutral position and became shorter in planter flexion and dorsiflexion. The results showed that the ATFL was taut in plantar flexion over 16.2 degrees, the PTFL and the CFL were taut in dorsiflexion over 18 degrees and 17.8 degrees respectively, and the TCL was taut between 9.5 degrees of dorsiflexion and 9.5 degrees of plantar flexion. The length change pattern was different among the ankle ligaments, although there was only a slight difference between that of the PTFL and the CFL. This study provides fundamental data useful in studying ankle ligament reconstruction.

Elongation behavior of calcaneofibular and cervical ligaments in a closed kinetic chain: pathomechanics of lateral hindfoot instability

Numerous reconstructive procedures are performed to correct both ankle and subtalar instability after trauma although the precise pathology which results in this chronic instability and pain is not yet known. This study examined the role of the calcaneofibular (CLFL) and cervical ligaments (CRVL) during physiologic loading and demonstrated the effect of CLFL deficiency on the CRVL. Talar and subtalar tilt as well as inversion range of motion before and after CLFL sectioning were studied. Eleven osteoligamentous fresh frozen cadaver legs were used in which each foot was taken through six positions: neutral, 35 degrees plantarflexion, dorsiflexion, inversion, plantarflexion-inversion, and dorsiflexion-inversion. The CLFL and CRVL stretched the greatest in dorsiflexion-inversion. The most interesting finding was that the CRVL was elongated relative to neutral in all other test positions of the foot. However, the CLFL was shortened relative to neutral in plantarflexion and plantarflexion-inversion. In the CLFL deficient state, CRVL ratios demonstrated significant increases in length of the CRVL. Talar tilt increased on average more than 9 degrees with CLFL deficiency (p < 0.008) while subtalar tilt did not change significantly. The maximum tibiocalcaneal angle, recorded for dorsiflexion-inversion, increased more than 5 degrees after sectioning the CLFL (p < 0.05).

Intra-rater and inter-rater reliability of a weight-bearing lunge measure of ankle dorsiflexion

This study aimed to evaluate the inter-rater and intra-rater reliability of a weight-bearing dorsiflexion (DF) lunge in 13 healthy subjects. Our raters with varying clinical experience tested all subjects in random order. Two of the raters repeated the measurements one week later. Two methods were used to assess the DF lunge: (i) the distance from the great toe to the wall and (ii) the angle between the tibial shaft and the vertical using an inclinometer. The average of three trials was used in data analysis. Intra-rater intraclass correlation coefficients (iccs) ranged from 0.97 to 0.98. Inter-rater ICC values were 0.97 (angle) and 0.99 (distance). results indicate excellent reliability for both methods of assessing a DF lunge.

The role of the passive structures in the mobility and stability of the human ankle joint: a literature review

The mobility and stability of the ankle joint have been extensively investigated, but many critical important issues still need to be elucidated. However, there seems to be a general agreement on several important observations. A more isometric pattern of rotation for the calcaneofibular and the tibiocalcaneal ligaments with respect to all the others has been reported. Many recent studies have found changing positions of the instantaneous axis of rotation, suggesting that the hinge joint concept is an oversimplification for the ankle joint. A few recent works have also claimed anterior shift of the contact area at the tibial mortise during dorsiflexion, which would imply combined rolling and sliding motion at this joint. Many findings from the literature support the view of a close interaction between the geometry of the ligaments and the shapes of the articular surfaces in guiding and stabilizing motion at the ankle joint.