The tensile strength of the anterior talofibular ligament

[Treatment of acute ankle distortion in footballers : Are we doing it particularly right or particularly wrong?]

BACKGROUND

Despite the high incidence of ankle sprains, the ideal treatment is controversial and a significant percentage of patients who have suffered an ankle sprain never fully recover. Even professional athletes are affected by this post-traumatic complication. There is strong evidence that permanent impairment after an ankle injury is often due to an inadequate rehabilitation and training program and too early return to sport.

THERAPY AND REHABILITATION

Therefore, athletes should start a criteria-based rehabilitation after ankle sprain and gradually progress through the programmed activities, including e.g. cryotherapy, edema reduction, optimal load management, range of motion exercises to improve ankle dorsiflexion and digital guidance, stretching of the triceps surae with isometric exercises and strengthening of the peroneus muscles, balance and proprioception training, and bracing/taping. The fact that this is professional sport does not exempt it from consistent, stage-appropriate treatment and a cautious increase in load. However, there are a number of measures and tools that can be used in the intensive care of athletes to improve treatment and results.

Acute Ankle Sprain in Elite Athletes: How to Get Them Back to the Game?

Despite the high frequency of ankle sprains, the ideal management is controversial, and a significant percentage of patients sustaining an ankle sprain never fully recover. There is strong evidence that residual disability of ankle joint injury is often caused by an inadequate rehabilitation and training program and early return to sports. Therefore, the athlete should start their criteria-based rehabilitation and gradually progress through the programmed activities, including cryotherapy, edema relief, optimal weight-bearing management, range of motion exercises for ankle dorsiflexion improvement, triceps surae stretching, isometric exercises and peroneus muscles strengthening, balance and proprioception training, and bracing/taping.

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.

Anatomic reconstruction of the lateral ligaments using allograft tendon and suspensory fixation for chronic lateral ankle instability with poor remnant quality: results and complications

PURPOSE

Treatment of chronic lateral ankle instability (CLAI) with poor remnant quality is challenging. The aim of the present study was to evaluate clinical results and complications of anatomic reconstruction of the lateral ligaments using allograft tendon and suspensory fixation in the treatment of such patients.

METHODS

One hundred and eight patients with CLAI, who were treated surgically using anatomic reconstruction with allograft tendon and suspensory fixation between April 2016 and January 2018 at our hospital, were retrospectively analysed. None of the patients had sufficient ligament remnants for the modified Broström procedure during the intraoperative evaluation. Eighteen patients were excluded. Seventeen patients were lost to follow-up and 73 patients completed the study. The mean duration of instability symptoms was 39.1 months (range, 6-480 months). The mean follow-up time was 57.5 months (range, 48-69 months). Clinical results were evaluated using the Karlsson scoring scale, American Orthopaedic Foot and Ankle Society-Ankle and Hindfoot (AOFAS-AH) score, visual analogue scale (VAS), patients' subjective satisfaction, and incidence of complications. Mechanical stability was evaluated using the varus talar tilt angle (TTA) and anterior talar displacement (ATD).

RESULTS

The AOFAS-AH scores significantly improved from 67.7 ± 8.5 points to 89.8 ± 9.5 (p < 0.001). The Karlsson scoring scales evolved from 58.8 ± 16.5 to 88.4 ± 11.2 (p < 0.001). VAS scores significantly decreased from 2.9 ± 1.3 to 1.1 ± 1.0 (p < 0.001). On stress radiographs, TTA decreased from 15.1 ± 2.5 degrees to 5.8 ± 2.1 degrees (p < 0.001), whereas ATD reduced from 13.4 ± 2.9 mm to 5.7 ± 1.5 mm (p < 0.001). Patients' subjective satisfaction indicated 46 excellent, 20 good, 5 fair, and 2 bad results. Postoperatively, 15 cases (20.5%) did not achieve complete relief of discomfort or swelling, 9 cases (12.3%) experienced joint stiffness or decreased range of motion, and 6 cases (8.2%) had soft tissue irritation. Residual instability and reoperation are rare. Allograft rejection or wound infection was not observed.

CONCLUSION

For the CLAI patients with poor remnant quality, anatomic reconstruction of the lateral ligaments using allograft tendon and suspensory fixation is an effective procedure, while the top three complications in incidence were residual discomfort, joint stiffness, and soft tissue irritation.

LEVELS OF EVIDENCE

Level IV, retrospective case series.

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.

Use of portable ultrasonography for the diagnosis of lateral ankle instability

Portable ultrasonography is increasingly used to evaluate ankle stability at the point of care. This study aims to determine the correlation of portable-ultrasonographic and fluoroscopic measurements of ankle laxity in a cadaveric ligament transection model of ankle ligament injury. We hypothesize that there is an association between portable-ultrasonographic and fluoroscopic measurements when performing stress evaluation of lateral ankle instability. Eight fresh-frozen below-knee amputated cadaveric specimens with intact proximal fibula underwent ultrasound and fluoroscopic evaluation of the ankle during anterior drawer and talar tilt testing. The assessment was first performed with all lateral ankle ligaments intact and thereafter with sequential transection of the anterior talofibular ligament, calcaneofibular ligament, and posterior talofibular ligament. The anterior drawer test was performed with both 50N and 80N of force, and talar tilt test was performed with 1.7 Nm of torque. Correlations between (1) portable-ultrasonographic and fluoroscopic measurements and (2) sequential transection of lateral ankle ligaments were evaluated using Spearman's rank correlations. The same statistical test was used to investigate the correlation between the ultrasonographic and the fluoroscopic measurements. The inter- and intra-observer agreement was assessed using the intraclass correlation coefficient through a two-way mixed-effects model with absolute agreement. Portable-ultrasonographic and fluoroscopic measurements increased as additional ligaments of the lateral ankle were transected (Spearman's rank correlation ranged from 0.74 to 0.81, 0.74 to 0.81, p-values < 0.001). Strong positive correlations between ultrasonographic and fluoroscopic measurements were found during the lateral ankle stability evaluation using anterior drawer and talar tilt testing (Spearman's rank correlation ranged from 0.81 to 0.85, 0.81 to 0.85, p-values < 0.001). Inter-rater (0.99, 95% CI: 0.98-0.99) and intra-rater reliability (0.97, 95% CI: 0.95-0.99) for the ultrasonographic measurements were substantial. In conclusion, there was a strong correlation found between ultrasonographic and fluoroscopic values measured during simulated anterior drawer and talar tilt test in a cadaveric ligament transection model. In this model, the portable-ultrasonographic measurement was found to be reliable for repeated measurements of the talar translation and the lateral clear space distance. Based on these data, ultrasonography is likely to become a valuable point of care diagnostic tool due to its ability to readily and dynamically evaluate suspected lateral ankle instability. Clinical Significance: The use of dynamic stress ultrasound to assess the anterior translation of the talus and the lateral clear space distance appears to be a reliable and repeatable technique to evaluate lateral ankle stability with a radiation-free, noninvasive, and low-cost manner.

Suture button fixation method used in the treatment of syndesmosis injury: A biomechanical analysis of the effect of the placement of the button on the distal tibiofibular joint in the mid-stance phase with finite elements method

PURPOSE

The purpose of this study is to research the effect of suture button (SB) fixation, a method used at the treatment of ankle syndesmosis injury, which was applied in various angles, pretension force, and levels, on the distal tibiofibular joint (DTFJ) in the mid-stance phase, with the help of three-dimensional finite elements method (FEM) METHOD: The ankle of a healthy individual was digitally analyzed by a finite element method-based package computer program. Then, anterior inferior tibiofibular ligament (AITFL), interosseous ligament, posterior inferior tibiofibular ligament (PITFL) and deltoid ligament (DL) were cut and force and rotation has been applied to the proximal tibia, resulting in syndesmosis injury. Then, various suture button applications on the injured model have been analyzed. Three parameters have been changed; which were divergence in the axial plane (20°, 30°, 40°), distance from the ankle (2, 3, 4 cm), and pretension force (200, 300, 600 N) RESULTS: As the result of this study, the rotation, change in the gap between the distal tibia and distal fibula, and the displacements of the fibula in the x and y axes have been obtained, and numerical results were evaluated. As the force increased, rotation, change in the gap between the distal tibia and distal fibula, and the displacements of the fibula decreased. As suture button application rotation increased, change in the gap between the distal tibia and distal fibula, and displacements of the fibula increased. As the distance from the ankle increases and reaches a certain level, the results converge to those of the healthy model; in the proximal, it diverges from healthy results.

CONCLUSION

In the study, it has been shown that abnormal tibiofibular joint movements can be prevented with suture button application, and optimum application parameters (divergence in the axial plane, distance from the ankle, and pretension force) are given for proper reduction.

A Critical Biomechanical Evaluation of Foot and Ankle Soft Tissue Repair

The objective of this article is to review the biomechanical stresses that occur during normal physiologic function of lower extremity soft tissue anatomic structures and to use this as a baseline for a critical analysis of the medical literature because it relates to surgical reconstruction following injury. The Achilles tendon, anterior talofibular ligament, plantar plate, and spring ligament are specifically evaluated.

Diagnosis and Treatment of Chronic Lateral Ankle Instability: Review of Our Biomechanical Evidence

Definitive diagnosis and optimal surgical treatment of chronic lateral ankle instability remains controversial. This review distills available biomechanical evidence as it pertains to the clinical assessment, imaging work up, and surgical treatment of lateral ankle instability. Current data suggest that accurate assessment of ligament integrity during physical examination requires the ankle to ideally be held in 16° of plantar flexion when performing the anterior drawer test and 18° of dorsiflexion when performing the talar tilt test, respectively. Stress radiographs are limited by their low sensitivity, and MRI is limited by its static nature. Surgically, both arthroscopic and open repair techniques appear biomechanically equivalent in their ability to restore ankle stability, although sufficient evidence is still lacking for any particular procedure to be considered a superior construct. When performing reconstruction, grafts should be tensioned at 10 N and use of nonabsorbable augmentations lacking viscoelastic creep must factor in the potential for overtensioning. Anatomic lateral ligament surgery provides sufficient biomechanical strength to safely enable immediate postoperative weight bearing if lateral ankle stress is neutralized with a boot. Further research and comparative clinical trials will be necessary to define which of these ever-increasing procedural options actually optimizes patient outcome for chronic lateral ankle instability.

Assessment of plantaris and peroneus tertius tendons as graft materials for ankle ligament reconstructions - A cadaveric biomechanical study

Both the plantaris tendon and the peroneus tertius tendon are used as auto- and allogenous graft materials to reconstruct the ankle ligament complex. However, it is unclear to what extent these graft materials resemble the load-deformation behavior of the ankle ligaments. A total of 34 human ankle ligaments and 35 tendons were assessed mechanically deploying a quasi-static tensile testing setup. Tendons were significantly stiffer (median elastic moduli: plantaris tendon = 465.7 MPa, peroneus tertius tendon = 338.5 MPa, medial ligament = 61.4 MPa, lateral ligament = 49.3 MPa; p ≤ 0.035), but more distensible (median strain at maximum force: plantaris tendon = 15.1%, peroneus tertius tendon = 15.3%, medial ligament = 9.3%, lateral ligament = 9.6%; p ≤ 0.008) and mechanically tougher (median ultimate tensile strength: plantaris tendon = 51.0 MPa, peroneus tertius tendon = 40.5 MPa, medial ligament = 4.1 MPa, lateral ligament = 3.5 MPa; p ≤ 0.033) when compared to medial and lateral ankle ligaments. The lateral ligaments of the right ankle were significantly tougher compared to the left side (p = 0.015). The elastic modulus of the medial ligament (r = 0.489, p = 0.045) and the peroneus tertius tendon (r = 0.517, p = 0.014) yielded an age-dependent increase. Both tendons seem biomechanically suitable graft materials to replace the medial and lateral ankle ligaments during physiological loading. The age-dependent increase in tissue elastic properties of the medial vs. lateral ankle ligaments, and differences in ultimate tensile strength between the lateral ligaments left vs. right, may reflect the complex asymmetric loading behavior of both ankle ligaments.

Return to Play After a Lateral Ligament Ankle Sprain

Purpose of Review

The purpose of this review is to describe the current evidence on the most common sports-related ankle injuries. Joint anatomy, epidemiology, clinical findings, diagnostic approach, and treatment are presented with a specific focus on the available evidence towards return to play.

Recent Findings

Recent findings show that ankle sprain is the most common injury in the world of sports. Bony fractures, cartilage defects, and syndesmotic lesions are frequently seen in association with the more severe type of ankle sprains.

Summary

In summary, the majority of the athletes’ ankle sprains are managed conservatively with excellent outcomes and full return to their pre-injury level of play. However, it is essential to differentiate the single ligament sprain from a more complex injury to the ankle joint. The evidence-based treatment and rehabilitation programmes are associated with a better prognosis and a faster time to return to sport participation.

Avulsion fracture of anterior talofibular ligament from talus: A case report

Anterior talofibular ligament (ATFL) injuries can occur in three different distinct patterns; rupture of the ligament as a pure soft tissue injury, an avulsion fracture at the ATFL's attachment to either the fibula or the talus. Although fibular avulsion fractures are common, avulsion fracture of ATFL from talus is extremely rare with a single previously reported case in the current literature. A 34-year-old female with ATFL talar avulsion fracture associated with medial malleolar fracture was presented to the emergency department. Fixation of the fragment resulted with excellent functional outcome without a residual instability. Besides more common injury patterns such as mid-substance ATFL rupture and ATFL fibular avulsion fracture, talar avulsion fracture pattern should also be kept in mind in a patient presented with lateral ankle sprain. When a fragment is seen on the ankle radiographs at the tip of fibula, previously described special oblique views should be performed to reveal the correct origin of the fragment.

Function of anterior talofibular and calcaneofibular ligaments during in-vivo motion of the ankle joint complex

Background

Despite the numerous in-vitro studies on the mechanical properties and simulated injury mechanisms of the anterior talofibular ligament (ATFL) and calcaneofibular ligament (CFL), the in-vivo biomechanical behavior of these two ligaments has not yet been described.

Methods

Apparent length of the ATFL and CFL was measured in four ankles in healthy male subjects between 32 and 45 years of age (two left and two right) during a dorsiflexion-plantarflexion and supination-pronation arc of motion using a combined dual-orthogonal fluoroscopic and magnetic resonance imaging technique.

Results

The ATFL elongated from the neutral position at 16.3 +/- 3.0 mm to 20.8 +/- 2.7 mm at maximal plantarflexion and shortened significantly from the neutral position to 13.9 +/- 2.9 mm at maximal dorsiflexion (p = 0.01). The CFL shortened from the neutral position at 28.0 +/- 2.9 mm to 26.6 +/- 2.2 mm at maximal plantarflexion (p = 0.08) and elongated significantly from the neutral position to 29.9 +/- 3.0 mm at maximal dorsiflexion (p = 0.003). The ATFL elongated significantly from 14.8 +/- 2.5 mm at maximal pronation to 17.4 +/- 3.0 mm at maximal supination (p = 0.08). At the same time, the CFL shortened from 31.0 +/- 3.8 mm at maximal pronation to 26.9 +/- 3.6 mm at maximal supination (p = 0.02).

Conclusion

The results showed that the ATFL elongates more during plantarflexion and supination whereas the CFL increases in length with dorsiflexion and pronation. Concurrently, these data also demonstrated the reciprocal function between the two ligaments. While one shortens, the other one elongates. The different elongation of the ATFL and CFL during the same motion arc suggests that under excessive loading conditions the ATFL might be more vulnerable in plantarflexion and supination while the CFL might be more susceptible to injury in dorsiflexion and pronation. Furthermore, in the case of surgical reconstruction the grafts used to reconstruct the two ligaments may need to be tensioned at different positions of the ankle in order to reproduce their natural in vivo function.

The anatomy in relation to injury of the lateral collateral ligaments of the ankle: a current concepts review

Injuries to the lateral ligament complex of the ankle are common problems in acute care practice. We believe that a well-developed knowledge of the anatomy provides a foundation for understanding the basic mechanism of injury, diagnosis, and treatment, especially surgical treatment, of lateral collateral ankle ligament injury. To address this issue we performed this review with regard to the anatomy of the lateral collateral ankle ligaments.

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.

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.

The skeletal attachment of tendons--tendon "entheses"

Tendon entheses can be classed as fibrous or fibrocartilaginous according to the tissue present at the skeletal attachment site. The former can be "bony" or "periosteal", depending on whether the tendon is directly attached to bone or indirectly to it via the periosteum. At fibrocartilaginous entheses, the uncalcified fibrocartilage dissipates collagen fibre bending and tendon narrowing away from the tidemark; calcified fibrocartilage anchors the tendon to the bone and creates a diffusion barrier between the two. Where there are additional fibrocartilaginous specialisations in the tendon and/or bone next to the enthesis, an "enthesis organ" is created that reduces wear and tear. Little attention has been paid to bone at entheses, despite the obvious bearing this has on the mechanical properties of the interface and the clinical importance of avulsion fractures. Disorders at entheses (enthesopathies) are common and occur in conditions such as diffuse idiopathic skeletal hyperostosis and the seronegative spondyloarthropathies. They are also commonly seen as sporting injuries such as tennis elbow and jumper's knee.

The functional anatomy of the human anterior talofibular ligament in relation to ankle sprains

The anterior talofibular ligament is the most commonly injured ligament in the ankle. Despite considerable interest in the clinical outcome of treatment protocols, we do not know whether the distinctive pattern of localization of the injuries relates to regional differences in the structure and molecular composition of the ligament. To address this issue, ligaments were examined by histology and immunohistochemistry. Differences in the structure of its two attachments (i.e. entheses) were evaluated with quantitative, morphometric techniques, and regional differences in the distribution of collagens, glycosaminoglycans and proteoglycans were determined qualitatively by immunolabelling. Morphometric analyses showed that bone density was less at the fibular attachment, but that enthesis fibrocartilage was more prominent. Immunohistochemistry revealed the presence of a fibrocartilage (containing type II collagen and aggrecan) at the site where the ligament wraps around the lateral talar articular cartilage in a plantarflexed and inverted foot: the fibrocartilage is regarded as an adaptation to resisting compression. We propose that avulsion fractures are less common at the talar end of the ligament because (1) bone density is greater here than at the fibular enthesis, and (2) stress is dissipated away from the talar enthesis by the 'wrap-around' fibrocartilaginous character of the ligament near the talar articular facet.

Biomechanics of the unstable ankle joint and clinical implications

PURPOSE

The aim of this paper is to provide fundamental information about the biomechanics of the unstable ankle joint and to establish a rational for the daily clinic when dealing with patients in both, the acute and chronic unstable condition of the ankle joint complex.

METHODS

The problem of the unstable ankle joint is worked up by analyses of the basic anatomy and biomechanics followed by an overview of its clinical manifestation including a differential diagnosis.

RESULTS

The ankle joint and its surrounding ligaments represent a complex mechanical structure whose mechanical properties highly depend on ligament integrity. Recent in vitro studies have supported the hypothesis that, besides maintaining lateral ankle stability, the lateral ankle ligaments play a significant role in maintaining rotational ankle stability and in transferring movement between leg and foot. Instability of the ankle results from acute ligament injuries and may become chronic when complete ligament healing does not occur. Chronic instability syndrome may manifest with recurrent injuries with chronic lateral pain, tenderness, swelling, or induration with great difficulties in sports and daily activities. Symptomatic instability can be caused by mechanical instability with demonstrable instability, but it can be also present with no demonstrable instability. Impairment of ankle proprioception has been shown to be a major cause of symptomatic ankle instability. Other conditions may mimic ankle instability.

CONCLUSIONS

The cause of chronic functional instability is often not mechanical instability but impairment of ankle proprioception. A history of insecurity, instability, and giving way is far more important in diagnosis than the physical and radiographic examination. If surgical treatment is advised, anatomical reconstruction of the ankle ligaments is mandatory for fear of altering the biomechanics.

Effectiveness of external ankle support. Bracing and taping in rugby union

Ankle inversion sprain is common in rugby. This review outlines research evidence relating to the effects of external ankle support by means of bracing and taping, on the incidence of ankle injuries, how performance is affected by support, how support may act at the joint (with respect to end range of motion, strength, resistive torque, muscle activation patterns and proprioception) to prevent injury, and how exercise changes the effectiveness of support. In addition, the implications of the laws of rugby for the use of external support are discussed. Prospective epidemiological studies have shown a decrease in the incidence of ankle injury with external ankle support use. The effectiveness of external ankle support was dependent upon the material properties and application method of the tape or brace, and on the athlete's status of ankle stability or previous injury. Experimental studies have indicated that the degree of ankle inversion restriction provided, and the degree of loss of restriction after exercise, were dependent upon the external support tested. External ankle support has been reported to have no effect on performance, or to have an adverse effect on performance in a variety of movement tasks. No prophylactic external ankle support has been shown to improve performance. If an external support is to provide mechanical support to a ligament it should exceed the strength of the ligament, which for the anterior fibular ligament is a force limit of between 6 and 56 kg. Tape can provide only limited mechanical support of the ankle joint complex, but it may have proprioceptive effects. Taping may work as a psychological reminder, so that the athlete consciously moderates lower limb-loading behaviour. There is equivocal evidence of the effect of brace use on ground reaction force excursions, balance ability and ankle strength. It is concluded that while there have been many investigations of the effects of tape and some forms of brace on ankle range of motion with and without exercise, there is equivocal evidence regarding the mechanism by which an external support acts. It is recommended that future research address the effects of external ankle support during dynamic exercise and that brace manufacturers utilise the information in the development of future brace designs to help reduce the risk of ankle inversion sprain injury. As external support can decrease the incidence of ankle inversion sprain the International Rugby Board should consider the use of ankle braces in rugby, allowing for stiff lateral components of the brace.

The stabilizing role of the lateral ligament complex around the ankle and subtalar joints

The stabilizing role of various ligaments in the lateral side of the ankle and hindfoot was examined experimentally and sequentially using 10 fresh amputated lower limbs. The anterior talofibular ligament contributed to ankle stability in plantarflexion and the calcaneofibular, the fibulotalocalcaneal, and posterior talofibular ligament in all positions. The lateral root of the inferior extensor retinaculum contributed to subtalar stability in neutral and dorsiflexion. The calcaneofibular, fibulotalocalcaneal, and cervical ligaments and the ligament of the anterior capsule of the posterior talocalcaneal joint and the interosseous ligaments contributed to subtalar stability in all positions. The subtalar joint accounted for upward of 50% of ankle/hindfoot inversion after ligament division in the intermalleolar plane.

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

The purposes of this study were: (1) to measure the distances between the insertion sites of selected ankle ligament fibers, (2) to measure the force-elongation characteristics of isolated bone-ligament-bone preparations, and (3) to relate the force measurements to angular positions of the ankle. The findings can be used to discuss clinically the correlation between possible ligament injuries and associated foot movement. Three fresh cadaveric ankles were dissected to expose the anterior talofibular ligament, the calcaneofibular ligament, and the superficial deltoid ligament. The ankles were first mounted on a fixture, and insertion to insertion distances of the ligament fibers were measured for selected positions of the ankle/subtalar joint. Bone-ligament-bone preparations were then removed, returned to their anatomical length and uniaxial force-extension testing was performed. The forces in each ligament were recorded for distances corresponding to those measured in situ for various ankle positions. These results allowed: (1) estimation of the forces in these three ligaments in various ankle positions, (2) identification of positions where ligaments were carrying no force, and (3) identification of positions where they carry large forces. The clinical analysis reveals that the anterior talofibular ligament is sensitive to excessive plantarflexion or dorsiflexion, the calcaneofibular ligament is sensitive to excessive inversion or eversion as well as dorsiflexion or plantarflexion, and that the deltoid ligament appears to be sensitive to plantarflexion, external rotation, and eversion. The fact that all three ligaments tested demonstrated different ranges of tension supports the view that there are optimal positions for testing ankle ligament integrity.

The mechanical characteristics of the collateral ligaments of the human ankle joint

In the present study, the tensile mechanical properties of all of the collateral ligaments of the human ankle joint were determined, in vitro, from tensile tests conducted on 120 ligaments obtained from 20 fresh lower limbs. The ultimate load of the lateral collateral ligaments increased in an anteroposterior sequence, with the anterior fibulotalar ligament less than the fibulocalcaneal ligament and less than the posterior fibulotalar ligament. For the medial collateral ligaments, the increasing order of ultimate load was found to be tibiocalcaneal ligament, tibionavicular ligament, tibiospring ligament, posterior tibiotalar ligament. The posterior tibiotalar ligament and tibiospring ligament, so frequently neglected in the anatomical and orthopaedic literature, demonstrated the highest yield force and ultimate load of all of the collateral ligaments of the ankle. Additionally, the tibiospring ligament showed high yield and ultimate elongation properties probably related to its distal attachment to the spring ligament. The fibulocalcaneal ligament was found to have high linear elastic modulus suggesting some type of unique material properties or internal fiber organization. Knowledge of the mechanical characteristics of the ligaments of the ankle joint contributes to an understanding of their normal function, pathomechanics of injury, and their optimal surgical reparative procedure and reconstructive material. A knowledge of the normal mechanical properties of the ankle ligaments provides a data base to evaluate which of the multiplicity of present tendon graft materials has mechanical properties similar to those of the ligaments to be replaced. Those tendon grafts will be the most suitable for replacement of specific ligaments. Finally, data on the mechanical properties of these ligaments offer the possibility for evaluating any future biological or prosthetic grafts.

A biomechanical study of human lateral ankle ligaments and autogenous reconstructive grafts

The purpose of this study was to investigate the biomechanical behavior of human anterior talofibular and calcaneofibular ligaments, as well as peroneus brevis, split peroneus brevis, and toe extensor tendon grafts. This article represents the first published data comparing the most frequently injured ankle ligaments to the most commonly used autogenous reconstructive grafts. Twenty fresh human ankles provided the bone-ligament-bone and tendon graft specimens for biomechanical testing on a Minneapolis Testing System. Protocol consisted of cyclic loading at physiologic deflections, followed by several load-deflection tests at varying velocities, followed by a final extremely rapid load to failure test. The load-deflection data for all ligaments and tendons demonstrated nonlinearity and strain rate dependence. The maximum load to failure for the anterior talofibular ligament was the lowest of all specimens tested, while its strain to failure was the highest. The loads to failure of the peroneus brevis and split peroneus tendons were significantly greater than the anterior talofibular ligament and approximately equal to the calcaneofibular ligament. Strains to failure for all tendons were significantly less than ligament strains. The high strain to failure of the anterior talofibular ligament demonstrates its physiologic function of allowing increased ankle plantar flexion-internal rotation, while its low load to failure shows its propensity for injury. The greater strength of the tendon grafts explains the success of most reconstructive procedures in reestablishing stability in chronic ankle sprains; at the same time, the data presented suggest that those surgical procedures sacrificing the entire peroneus brevis tendon are unnecessary.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical characteristics of human ankle ligaments

The purpose of this study was to define the biomechanical characteristics of the isolated, individual bone-ligament-bone complexes of the human ankle. Twenty human ankles were dissected of all soft tissues to leave only the tibia, fibula, talus, and calcaneus with their intact anterior talofibular, calcaneofibular, posterior talofibular, and deep deltoid ligaments. Specimens were mounted and tested in a Minneapolis Testing System. Protocol consisted of cyclic loading of each isolated bone-ligament-bone preparation, followed by several constant velocity load-deflection tests at varying deflection rates, followed by a final, extremely rapid load to failure test. All ligaments exhibited nonlinearity and strain rate dependence in their load-deflection data. These properties were correlated with ligament function and trauma. The anterior talofibular ligament, the most commonly injured ankle ligament, had the lowest mean maximum load of the specimens tested, whereas the deep deltoid ligament, the least frequently completely disrupted ankle ligament, had the highest load to failure.