Physiological elongation of ligamentous complex surrounding the hindfoot joints: in vitro biomechanical study

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.

The horizontal calcaneofibular ligament: a sign of hindfoot valgus on ankle MRI

OBJECTIVE

Hindfoot valgus malalignment has been assessed on coronal MRI by the measurement of the tibio-calcaneal (TC) angle and apparent moment arm (AMA). This study aimed to determine if the calcaneofibular ligament (CFL) angle could be used as a further marker of hindfoot valgus malalignment on routine non-weight-bearing ankle MRI.

MATERIAL AND METHODS

One hundred ninety-five consecutive 3-T ankle MRI studies were identified from the hospital PACS system. The TC and CFL angles could be measured in 155 cases (78%), and the AMA on 153 cases.

RESULTS

The study group comprised 56 males and 72 females with a mean age of 46 years (range 4-89 years). In 27 patients, both ankles had been imaged. The Pearson correlation between the TC and CFL angles was -0.43, with a corresponding p value of 0.001 indicating a strong negative correlation between the TC and CFL angles. The CFL angle was significantly lower in those with hindfoot valgus (113 ± 14) compared with those without (123° ± 15°) (p = 0.001). The optimal cut-off point of the CFL angle for hindfoot valgus was ≤119°, with a sensitivity and specificity of 66% and 63% respectively. The Pearson correlation between the CFL angle and AMA was -0.10, with a corresponding p value of 0.21 indicating a weak negative correlation that did not reach statistical significance.

CONCLUSION

Hindfoot valgus as estimated by the increased TC angle on coronal non-weight-bearing ankle MRI is associated with a reduced CFL angle on sagittal MR images, but is not associated with AMA. Therefore, a horizontal orientation of the CFL on sagittal MR images may be a further useful sign of hindfoot valgus.

Three-Dimensional (3D) Computed Tomographic (CT) Assessment of the Sustentaculum Tail to Find Distinctive Characteristics: Implications for Surgery

Background

With the complexity of calcaneal fracture (CF) increasing, its treatment has changed to include inserting the screw used to secure the facies articular posterior into the sustentaculum tail (ST). Some research progress has been made in this area, but there has been little in-depth research on the anatomical morphology of the sustentaculum tail, which is necessary for clinical surgery, and more information about Chinese anatomic characteristics and improved surgical techniques for CF are needed.

Material/Methods

This anatomical study, based on a three-dimensional (3D) computed tomographic (CT) reconstruction technique, included 287 dry calcaneus, consisting of 144 left and 143 right calcaneus. The images were reconstructed in 3D after CT scanning. Seven subjects were enrolled (L and R): (1) The vertical distance from inside the sustentaculum tail (IST) to inside the facies articularis talaris posterior; (2) The vertical distance from IST to the outside facies articularis talaris posterior; (3) The thickness of sulcus calcaneal nadir; (4) The distance from IST to processus medislis tuberis calcaneus; (5) The distance from IST to calcaneal posterosuperior tuber; (6) The angle of the prolate axial intersection between ST and calcaneus on the normal superior as ∠α; and (7) The angle of the prolate axial intersection between ST and calcaneus on the normal posterior as ∠β. All measurement results were analyzed by SPSS 22.0.

Results

Based on morphological classification, the average length of AB, AC, AE, and AF on left ST were 16.956±1.391 mm, 37.803±2.525 mm, 43.244±3.617 mm, and 51.113±4.455 mm, respectively. Among the others, ∠β was 81.227±6.317 mm on the left and 74.581±9.008 mm on the right (P<0.05).

Conclusions

These results suggest better ways to treat the special characteristics and to reduce the risk of CF surgery.

The effects on calcaneofibular ligament function of differences in the angle of the calcaneofibular ligament with respect to the long axis of the fibula: a simulation study

Background

In the present study, CFLs harvested from cadavers were categorized according to the differences in the angle of the CFL with respect to the long axis of the fibula and their shape, and then three-dimensional reconstructions of the CFLs were used to simulate and examine the differences in the angles of the CFLs with respect to the long axis of the fibula and how they affect CFL function.

Methods

The study sample included 81 ft from 43 Japanese cadavers. CFLs were categorized according to their angle with respect to the long axis of the fibula and the number of fiber bundles. Five categories were subsequently established: CFL20° (angle of the CFL with respect to the long axis of the fibula from 20° to 29°); CFL30° (range 30–39°); CFL40° (range 40–49°); CFL50° (range 50–59°); and CFL2 (CLFs with two crossing fiber bundles). Three-dimensional reconstructions of a single specimen from each category were then created. These were used to simulate and calculate CFL strain during dorsiflexion (20°) and plantarflexion (30°) on the talocrural joint axis and inversion (20°) and eversion (20°) on the subtalar joint axis.

Results

In terms of proportions for each category, CFL20° was observed in 14 ft (17.3%), with CFL30° in 22 ft (27.2%), CFL40° in 29 ft (35.8%), CFL50° in 15 ft (18.5%), and CFL2 in one foot (1.2%). Specimens in the CFL20° and CFL30° groups contracted with plantarflexion and stretched with dorsiflexion. In comparison, specimens in the CFL40°, CFL50°, and CFL2 groups stretched with plantarflexion and contracted with dorsiflexion. Specimens in the CFL20° and CFL2 groups stretched with inversion and contracted with eversion.

Conclusions

CFL function changed according to the difference in the angles of the CFLs with respect to the long axis of the fibula.

Investigation of the biomechanical behaviour of hindfoot ligaments

The aim of this work is to provide a computational tool for the mechanical characterization of the hindfoot ligaments. The investigation is performed by a coupled numerical and experimental approach. For this purpose, a numerical model that represents the complex structural configuration of the hindfoot and the typical features of the mechanical behaviour of the ligament tissue is developed. The geometrical analysis of the anatomical site is performed starting from the processing of computed tomography and magnetic resonance images. Accounting for morphometric measurements, the virtual solid model provides an averaged configuration of the hindfoot structure. In order to specify the mechanical behaviour of the ligament tissue, a fibre-reinforced visco-hyperelastic model is adopted. The formulation accounts for the anisotropic configuration, geometric non-linearity, non-linear elasticity and time-dependent phenomena. Numerical analyses are performed to evaluate the biological tissues and structure mechanics with regard to physiological boundary conditions, accounting for dorsiflexion and plantarflexion movements. In order to evaluate the reliability of the numerical model developed, the experimental data are compared with the numerical results. The numerical results are in agreement with the range of values obtained by experimental test confirming the accuracy of the procedure adopted.

Finite element analysis of the foot: model validation and comparison between two common treatments of the clawed hallux deformity

BACKGROUND

Clawed hallux is defined by first metatarsophalangeal joint extension and first interphalangeal joint flexion; it can increase plantar pressures and ulceration risk. We investigated two corrective surgical techniques, the modified Jones and flexor hallucis longus tendon transfer.

METHODS

A finite element foot model was modified to generate muscle overpulls, including extensor hallucis longus, flexor hallucis longus and peroneus longus. Both corrective procedures were simulated, predicting joint angle and plantar pressure changes.

FINDINGS

The clawed hallux deformity was generated by overpulling: 1) extensor hallucis longus, 2) peroneus longus + extensor hallucis longus, 3) extensor hallucis longus + flexor hallucis longus and 4) all three together. The modified Jones reduced metatarsophalangeal joint angles, but acceptable hallux pressure was found only when there was no flexor hallucis longus overpull. The flexor hallucis longus tendon transfer reduced deformity at the metatarsophalangeal and interphalangeal joints but may extended the hallux due to the unopposed extensor hallucis longus. Additionally, metatarsal head pressure increased with overpulling of the extensor hallucis longus + flexor hallucis longus, and all three muscles together.

INTERPRETATION

The modified Jones was effective in correcting clawed hallux deformity involving extensor hallucis longus overpull without flexor hallucis longus overpull. The flexor hallucis longus tendon transfer was effective in correcting clawed hallux deformity resulting from the combined overpull of both extensor and flexor hallucis longus, but not with isolated extensor hallucis longus overpull. An additional procedure to reduce the metatarsal head pressure may be required concomitant to the flexor hallucis longus tendon transfer. However this procedure avoids interphalangeal joint fusion.

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.

J. Leonard Goldner Award 2010. Ligament balancing for total ankle arthroplasty: an in vitro evaluation of the elongation of the hind- and midfoot ligaments

BACKGROUND

The changes in length of the hindfoot ligaments in response to alterations in ankle and subtalar joint orientation under physiologic load in eight fresh-frozen cadaver limbs were documented.

RESULTS

In eversion, the tibiocalcaneal (11% ± 4%, mean ± SD], calcaneofibular (6% ± 4%), posterior talofibular (7% ± 4%), posterolateral talocalcaneal (21% ± 9%), posteromedial talocalcaneal (33% ± 45%) and calcaneonavicular (bifurcate) (8% ± 7%) ligaments were elongated relative to their lengths in inversion. In inversion, the anterior capsular (talocalcaneal) (5% ± 3%) and the plantar cuboidnavicular (5% ± 6%) ligaments were elongated relative to their everted lengths. In dorsiflexion, the superficial (26% ± 8%) and deep posterior tibiotalar (30% ± 13%), calcaneofibular (8% ± 4%), tibiocalcaneal (4% ± 2%) and lateral talocalcaneal (cervical) (2% ± 1%) ligaments were elongated. In plantarflexion, the tibionavicular (26% ± 5%) and the anterior talofibular (7% ± 4%) ligaments were lengthened. No statistically significant elongation was documented in any ankle position for the anterior tibiotalar, talocalcaneal interosseous, plantar calcaneocuboid, calcaneocuboid (bifurcate), all components of the spring ligament, and the dorsal cuboidnavicular ligaments.

CONCLUSION

Components of the deltoid ligament complex elongated largest at the ankle joint with any hindfoot movement but inversion. Therefore, selective release of components of the deltoid ligament complex may provide a means for achieving optimal ligament balancing in total ankle arthroplasty. Specifically, release of the superficial and deep posterior tibiotalar ligament may improve range of motion in total ankle arthroplasties, whereas the release of the tibiocalcaneal ligament may correct a varus talar tilt.

Dynamic loading of the plantar aponeurosis in walking

BACKGROUND

The plantar aponeurosis is known to be a major contributor to arch support, but its role in transferring Achilles tendon loads to the forefoot remains poorly understood. The goal of this study was to increase our understanding of the function of the plantar aponeurosis during gait. We specifically examined the plantar aponeurosis force pattern and its relationship to Achilles tendon forces during simulations of the stance phase of gait in a cadaver model.

METHODS

Walking simulations were performed with seven cadaver feet. The movements of the foot and the ground reaction forces during the stance phase were reproduced by prescribing the kinematics of the proximal part of the tibia and applying forces to the tendons of extrinsic foot muscles. A fiberoptic cable was passed through the plantar aponeurosis perpendicular to its loading axis, and raw fiberoptic transducer output, tendon forces applied by the experimental setup, and ground reaction forces were simultaneously recorded during each simulation. A post-experiment calibration related fiberoptic output to plantar aponeurosis force, and linear regression analysis was used to characterize the relationship between Achilles tendon force and plantar aponeurosis tension.

RESULTS

Plantar aponeurosis forces gradually increased during stance and peaked in late stance. Maximum tension averaged 96% +/- 36% of body weight. There was a good correlation between plantar aponeurosis tension and Achilles tendon force (r = 0.76).

CONCLUSIONS

The plantar aponeurosis transmits large forces between the hindfoot and forefoot during the stance phase of gait. The varying pattern of plantar aponeurosis force and its relationship to Achilles tendon force demonstrates the importance of analyzing the function of the plantar aponeurosis throughout the stance phase of the gait cycle rather than in a static standing position.

CLINICAL RELEVANCE

The plantar aponeurosis plays an important role in transmitting Achilles tendon forces to the forefoot in the latter part of the stance phase of walking. Surgical procedures that require the release of this structure may disturb this mechanism and thus compromise efficient propulsion.

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.

Ligament fibre recruitment and forces for the anterior drawer test at the human ankle joint

Although the anterior drawer test at the ankle joint is commonly used in routine clinical practice, very little is known about the sharing of load between the individual passive structures and the joint response at different flexion angles.A mathematical model of the ankle joint was devised to calculate ligament fibre recruitment and load/displacement curves at different flexion angles. Ligaments were modelled as three-dimensional arrays of fibres, and their orientations at different flexion angles were taken from a previously validated four-bar-linkage model in the sagittal plane. A non-linear stress/strain relationship was assumed for ligament fibres and relevant mechanical parameters were taken from two reports in the literature. Talus and calcaneus were assumed to move as a single rigid body. Antero/distal motion of the talus relative to the tibia was analysed. The ankle joint was found to be stiffer at the two extremes of the flexion range, and the highest laxity was found around the neutral position, confirming previous experimental works. With a first dataset, a 20N anterior force produced 4.3, 5.5, and 4.4mm displacement respectively at 20 degrees plantarflexion, at neutral, and at 20 degrees dorsiflexion. At 10 degrees plantarflexion, for a 6mm displacement, 65% of the external force was supported by the anterior talofibular, 11% by the deep anterior tibiotalar and 5.5% by the tibionavicular ligament. Corresponding results from a second dataset were 1.4, 2.4 and 1.8mm at 40N force, and 80%, 0% and 2% for a 3mm displacement. A component of the contact force supported the remainder.

The geometric architecture of the subtalar and midtarsal joints in rheumatoid arthritis based on magnetic resonance imaging

OBJECTIVE

To compare in vivo the 3-dimensional (3-D) geometric architecture of the subtalar and midtarsal joints in normal and rheumatoid arthritic (RA) feet, using magnetic resonance imaging (MRI) analysis.

METHODS

MRI was performed on 23 patients with RA, all of whom had disease activity in the subtalar and/or midtarsal joints. Image processing techniques were used to create 3-D reconstructions of the calcaneus (C), cuboid (c), navicular (N), and talus (T) bones. Twenty-four standard architectural parameters were measured from the reconstructions and were compared with data from 10 normal subjects. These parameters defined both 3-D distance and angular relationships among the 4 bones studied. Pattern classification techniques were used to establish a geometric architecture foot profile for the RA patients. The degree of individual patient fit to the new RA foot profile and to profiles for normal, pes planus, and pes cavus foot types was derived. Logistic regression was used to examine the relationship of foot architecture to inflammatory disease characteristics and physical examination variables.

RESULTS

Subtalar or midtarsal pain was reported by all 23 patients, and 22 of the 23 patients presented with >/=1 clinical feature of pes planovalgus deformity. In 21 patients, ultrasonography revealed synovitis at >/=1 tarsal joint or surrounding tendon. In the RA group, the normalized distances between the geometric centroids were significantly closer for bone pairs Cc and cT and significantly distracted for bone pair CN compared with the distances in normal subjects. In RA patients (versus normal subjects), the angles subtended at the bone centroids were significantly decreased in 3 bone groups (CNc, TCN, and TNc) and significantly increased in 3 bone groups (CcN, CcT, NTc). The angles formed between the major principal axes of bone pairs CT and cT were significantly increased in RA patients compared with those in normal subjects. Pattern classification defined 11 RA feet as having normal structure and 12 as having abnormal structure. However, the abnormal feet did not fit consistently with structures defined for RA, pes planus, or pes cavus foot types. Logistic regression demonstrated that subtalar joint synovitis was the only predictive factor for abnormal subtalar and midtarsal architecture (odds ratio 19.2, 95% confidence interval 1.77-200.0).

CONCLUSION

This unique 3-D MRI-based technique successfully quantified the effects of RA on the geometric architecture of the foot and the patient-specific nature of these changes. This technique can be used to provide logical therapy for correction.

Effect of foot orthoses on 3-dimensional kinematics of flatfoot: a cadaveric study

OBJECTIVE

To test in cadaveric feet the hypothesis that prefabricated foot orthoses will improve arch alignment in flatfoot deformity.

DESIGN

Experimental, paired comparisons.

SETTING

Biomechanics laboratory.

CADAVERS

Nine cadaveric lower-extremity specimens with no abnormalities.

INTERVENTIONS

To evaluate the performance of 2 orthoses specimens were tested in 4 combinations: intact, flatfoot, flatfoot with shoe and orthosis 1, and flatfoot with shoe and orthosis 2. To simulate the midstance phase of gait, loads were applied to 5 tendons and an axial load equivalent to two thirds of the standing load was applied to the foot's plantar surface.

MAIN OUTCOME MEASURES

Arch height and tarsal bone positions before and after a flatfoot deformity created by ligament sectioning; tarsal bone positions determined with a magnetic tracking system.

RESULTS

After ligament sectioning, the average decrease in arch height with a shoe applied was 4.6+/-1.6mm (8%); with orthosis 1, mean arch height increased 0.7+/-0.6mm (P=.008); with orthosis 2, it increased 0.3+/-0.5mm (P=.05). With both orthoses, arch height after sectioning was significantly less than that of the normal arch. Compared with the flatfoot condition, metatarsal-talar alignment improved in plantar flexion and inversion with both orthoses but did not approximate normal with either orthosis. Calcaneal-tibial position did not improve with either orthosis and was markedly different from that in the intact foot with either orthosis. No difference was found between the 2 orthoses except for metatarsal-talar motion in external rotation (P=.014) and eversion (P=.026).

CONCLUSIONS

Arch alignment improved significantly but to a limited degree (<2%) in cadaveric feet with the use of orthoses. Hindfoot valgus malalignment did not consistently improve by the use of shoe inserts.

Anatomical study of the medial ankle ligament complex

The purpose of this in vitro study was to determine insertion area, length and thickness of the various bundles and their anatomical relationship with inter-individual differences. Twelve ankles from human cadavers (ages 56 to 95 years, from nine men and three women) were dissected to the capsuloligamentous structures. Marked inter-individual differences were found for the five main ligaments (tibiospring, tibiocalcaneal, posterior and anterior deep tibiotalar and superficial posterior tibiotalar). The tibionavicular ligament is a thickened fibrous layer of the ankle capsule. The tibiocalcaneal and tibiospring ligaments are the longest, and the tibiocalcaneal and posterior deep tibiotalar ligaments are the thickest of these ligaments. Fibrils run in the direction of the tibia or dorsally. Knowledge of the deltoid ligament complex is necessary for anatomically and biomechanically correct reconstruction that provides stability without hazard to biomechanics of function.

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.