The calcaneofibular ligament has distinct anatomic morphological variants: an anatomical cadaveric study

Anatomic Variations of the Calcaneofibular Ligament

BACKGROUND

The lateral ankle joint comprises the anterior talofibular ligament (ATFL), calcaneofibular ligament (CFL), and posterior talofibular ligament (PTFL). The purpose of this study was to propose a classification of CFL morphology.

METHODS

The material comprised 120 paired lower limbs from human cadavers (30 male, 30 female), mean age 62.3 years. The morphology was carefully assessed, and morphometric measurements were performed.

RESULTS

A 4-part method for anatomic classification can be suggested based on our study. Type 1 (48.3%), the most common type, was characterized by a bandlike morphology. Type 2 (9.2%) was characterized by a Y-shaped band, and type 3 (21.7%) by a V-shaped band. Type 4 (20.8%) was characterized by the presence of 2 or 3 bands. Type 2 and 4 were divided into further subtypes based on origin footprint.

CONCLUSION

The aim of our study was to describe variations of calcaneofibular ligament. Our proposed 4-part classification may be of value in clinical practice in future recognition of CFL injuries and in its repair or reconstruction.

CLINICAL RELEVANCE

The anatomy of the CFL plays an important role in stability of the ankle. Greater recognition of anatomical variation may help improve reconstructive options for patients with chronic lateral ankle instability.

Lateral Ankle Ligaments: An Insight Into Their Functional Anatomy, Variations, and Surgical Importance

BACKGROUND

Ankle sprains are prevalent injuries leading to functional impairment. The lateral ankle ligament complex (LLC), comprising the anterior talofibular ligament (ATFL), posterior talofibular ligament (PTFL), and calcaneofibular ligament (CFL), is weak and prone to injury. The morphometric data of these ligaments are essential for orthopedic practices, including techniques like direct repair or ATFL reconstruction with autograft/allograft, which are limited in the literature. The present study aims to document the anatomy and morphometry of the LLC.

METHODS

Fifteen adult Indian-origin embalmed cadavers were selected for the study. Ankles with antemortem or postmortem injuries or previous surgical interventions were excluded from the study. After precise dissection of the ankle's anterior and lateral aspects as per Cunningham's dissection manual, ligaments were exposed. Length and width were measured using a digital vernier caliper. Morphological attributes such as shape, orientation, and inter-fiber angles were documented.

RESULTS

The most common shape in ATFL was a single band (53.33%). Inner ATFL fibers merged with the ankle joint capsule in 73.33%. ATFL mean length and width were 14 ± 2.4 mm and 7.6 ± 2.0 mm. The angle between the fibula's long axis and ATFL fibers was 107 ± 22°, and the angle between tibiotalar joint lines and parallel ATFL fibers was 30 ± 9.5°. A single band of CFL was predominant (73.33%). The mean length and width of CFL were 18.4 ± 3.9 mm and 5.2 ± 1.3 mm; the angle between the anterior fibula border's long axes and parallel CFL line was 131°. PTFL length was 20.9 ± 3.3 mm and width was 6.2 ± 1.4 mm. The mean length and width of the anterior inferior talofibular ligament (AiTFL) were 11.7 ± 2.6 mm and 9.5 ± 1.6 mm, and of the posterior inferior talofibular ligament (PiTFL) were 12.8 ± 2.1 mm and 10.4 ± 2 mm.

CONCLUSION

Comprehensive knowledge of these ligaments' anatomy and relationships is vital for clinical examination and ultrasonography. Understanding LLC details aids radiologists and orthopedic surgeons in graft selection, sizing, and precise anatomical structure placement during surgical reconstruction.

The ATFL inferior fascicle, the CFL and the PTFL have a continuous footprint at the medial side of the fibula

PURPOSE

Knowledge of the complex anatomy of the lateral ankle ligaments is essential to understand its function, pathophysiology and treatment options. This study aimed to assess the lateral ligaments and their relationships through a 3D view achieved by digitally marking their footprints.

METHODS

Eleven fresh-frozen ankle specimens were dissected. The calcaneus, talus and fibula were separated, maintaining the lateral ligament footprints. Subsequently, each bone was assessed by a light scanner machine. Finally, all the scans were converted to 3D polygonal models. The footprint areas of the talus, calcaneus and fibula were selected, analysed and the surface area was quantified in cm2.

RESULTS

After scanning the bones, the anterior talofibular ligament inferior fascicle (ATFLif), calcaneofibular ligament (CFL) and posterior talofibular ligament (PTFL) footprints were continuous at the medial side of the fibula, corresponding to a continuous footprint with a mean area of 4.8 cm2 (± 0.7). The anterior talofibular ligament (ATFL) footprint on the talus consisted of 2 parts in 9 of the 11 feet, whilst there was a continuous insertion in the other 2 feet. The CFL insertion on the calcaneus was one single footprint in all cases.

CONCLUSION

The tridimensional analysis of the lateral ligaments of the ankle demonstrates that the ATFLif, CFL and PTFL have a continuous footprint at the medial side of the fibula in all analysed specimens. These data can assist the surgeon in interpreting the ligament injuries, improving the imaging assessment and guiding the surgeon to repair and reconstruct the ligaments in an anatomical position.

Anatomical variations of the calcaneofibular ligament in human foetuses

Ligaments anatomy often show a huge anatomy variations between species and individuals. For example calcaneofibular ligaments (CFL) characterize the great variability of morphological shape or presence of additional bands. The aim of this study was to propose first anatomical classification of CFL concerning on human fetuses. We investigated thirty spontaneously-aborted human fetuses aged 18-38 weeks of gestation at death. Sixty lower limbs (30 left and 30 right) fixed in 10% formalin solution were examined. The morphological variability of CFL was assessed. Four types of CFL morphology were observed. Type I was characterized by a band shape. This was the most common type, occurring in 53% of all cases. Based on our study we are proposing a classification based on four morphological types of CFL. Types 2 and 4 are further divided into subtypes. Present classification may be useful to better understand the anatomical development of ankle joint.

Clinical Relevance and Function of Anterior Talofibular Ligament Superior and Inferior Fascicles: A Robotic Study

BACKGROUND

Ankle lateral ligament sprains are common injuries in sports, and some may result in persistent ankle pain and a feeling of instability without clinical evidence of instability. The anterior talofibular ligament (ATFL) has 2 distinct fascicles, and recent publications have suggested that injury isolated to the superior fascicle might be the cause of these chronic symptoms. This study aimed to identify the biomechanical properties conferred by the fascicles in stabilizing the ankle in order to understand potential clinical problems that may follow when the fascicles are injured.

PURPOSE/HYPOTHESIS

The aim of this study was to determine the contribution of superior and inferior fascicles of the ATFL in restraining anteroposterior tibiotalar resistance, internal external tibial rotation resistance, and inversion eversion talar rotation resistance. It was hypothesized that an isolated injury of the ATFL superior fascicle would have a measurable effect on ankle stability and that the superior and inferior fascicles would restrain different motions of the ankle.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A robotic system with 6 degrees of freedom was used to test ankle instability in 10 cadavers. Serial sectioning following the most common injury pattern (from superior to inferior fascicles) was performed on the ATFL while the robot ensured reproducible movement through a physiological range of dorsiflexion and plantarflexion.

RESULTS

Sectioning of only the ATFL superior fascicle had a significant and measurable effect on ankle stability, resulting in increased internal rotation and anterior translation of the talus, especially in plantarflexion. Sectioning of the entire ATFL resulted in significantly decreased resistance in anterior translation, internal rotation, and inversion of the talus.

CONCLUSION

Rupture of only the superior fascicle of the ATFL may lead to minor instability or microinstability of the ankle joint, without objective clinical findings of gross clinical laxity.

CLINICAL RELEVANCE

Some patients develop chronic symptoms after an ankle sprain without overt signs of instability. This may be explained by an isolated injury to the ATFL superior fascicle, and diagnosis may require careful clinical evaluation and magnetic resonance imaging examination looking at the individual fascicles. It is possible that such patients may benefit from lateral ligament repair despite having no gross clinical instability.

Arthroscopic and Open Procedures Result in Similar Calcaneal Tunnels for Anatomical Reconstruction of Lateral Ankle Ligaments

Purpose

The purpose of this study was to validate the accuracy and reliability of arthroscopic markers of distal insertion of the calcaneofibular ligament (CFL), and to compare the calcaneus bone tunnels of the CFL that were made under arthroscopy and open procedures.

Methods

Fifty-seven patients who underwent lateral ankle ligament reconstruction procedures were enrolled and divided into open (n = 24) and arthroscopic groups (n = 33). Lateral ankle radiography was performed postoperatively, and the calcaneus bone tunnels referenced to several landmarks, including the subtalar joint, calcaneus superior edge, fibular tip, angulation with fibula axis, cross point of the fibular and tangential line of the fibular obscure tubercle cross point of the tangential lines of the talar posterior edge and deepest point of the subtalar joint, and cross point of the fibular axis and perpendicular line across fibular tip. These results were compared between the two groups.

Results

No significant intergroup differences were observed between the parameters. When the bone tunnels of the CFL were referenced to the cross point of tangential lines of the talar posterior edge and deepest point of the subtalar joint, and the cross point of the fibular axis and perpendicular line across fibular tip, the coefficient variations were very high, which indicated that the locations of the bone tunnels were scattered over a large area in both groups.

Conclusions

Arthroscopic and open procedures achieved similar results for calcaneus bone tunnel making of the CFL. However, large variations were observed in both groups.

Level of Evidence

Level III, retrospective cohort study.

Anatomy of the Ankle and Subtalar Joint Ligaments: What We Do Not Know About It?

Understanding of the ankle and subtalar joint ligaments is essential to recognize and manage foot and ankle disorders. The stability of both joints relies on the integrity of its ligaments. The ankle joint is stabilized by the lateral and medial ligamentous complexes while the subtalar joint is stabilized by its extrinsic and intrinsic ligaments. Most injuries to these ligaments are linked with ankle sprains. Inversion or eversion mechanics affect the ligamentous complexes. A profound knowledge of the ligament's anatomy allows orthopedic surgeons to further understand anatomic or nonanatomic reconstructions.

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.

Current Concepts on Subtalar Instability

Subtalar instability remains a topic of debate, and its precise cause is still unknown. The mechanism of injury and clinical symptoms of ankle and subtalar instabilities largely overlap, resulting in many cases of isolated or combined subtalar instability that are often misdiagnosed. Neglecting the subtalar instability may lead to failure of conservative or surgical treatment and result in chronic ankle instability. Understanding the accurate anatomy and biomechanics of the subtalar joint, their interplay, and the contributions of the different subtalar soft tissue structures is fundamental to correctly diagnose and manage subtalar instability. An accurate diagnosis is crucial to correctly identify those patients with instability who may require conservative or surgical treatment. Many different nonsurgical and surgical approaches have been proposed to manage combined or isolated subtalar instability, and the clinician should be aware of available treatment options to make an informed decision. In this current concepts narrative review, we provide a comprehensive overview of the current knowledge on the anatomy, biomechanics, clinical and imaging diagnosis, nonsurgical and surgical treatment options, and outcomes after subtalar instability treatment.

Connecting fibers between ATFL's inferior fascicle and CFL transmit tension between both ligaments

PURPOSE

The lateral ligament complex of the ankle has been extensively studied. Recently an anatomical study described a connection between anterior talofibular ligament inferior fascicle (ATFLif) and calcaneofibular ligament (CFL). The applicability and the mechanical role of these connections have not yet been studied and need to be clarified. The purpose of this study is to evaluate the connection between ATFLif and CFL through a dynamic measurement analysis.

METHODS

An anatomical study was performed in 13 fresh-frozen below-the-knee ankle specimens. Each specimen was dissected in a protocolized manner until the lateral ligaments were exposed. A complete injury to both ATFL's fascicles was created in the proximal third of the ligament. A displacement transducer specifically design was inserted in the CFL and in the lateral part of the calcaneus to test its lengthening. A traction of 1 kg weight (9.8 N) was applied to ATFLif while the transducer measured the lengthening that this force created in the CFL.

RESULTS

A total of 13 ankle specimens were carefully dissected. One specimen with signals of a prior traumatic injury of the ATFLif was excluded. A total of 12 specimens were included, 7 females and 5 males with an average age of 74 years (52-88 years). The right ankle was dissected in 6 specimens. ATFL was identified as a two-fascicled ligament in all cases. The fibers connecting the ATFLif and CFL were observed in all specimens. The displacement transducer showed lengthening in the CFL in all measurements with a median of 0.59 mm (SD ± 0.34).

CONCLUSION

Connecting fibers between ATFLif and CFL are robust enough to transmit tension from one structure to the other. In the case of associated proximal lesions of the ATFLif and CFL, ligaments repair with a single suture may be considered. This can be applied in surgical procedures in patients with lateral ankle instability.

A calcaneal tunnel for CFL reconstruction should be directed to the posterior inferior medial edge of the calcaneal tuberosity

PURPOSE

Anatomical reconstruction of the calcaneofibular ligament (CFL) is a common technique to treat chronic lateral ankle instability. A bone tunnel is used to fix the graft in the calcaneus. The purpose of this study is to provide some recommendations about tunnel entrance and tunnel direction based on anatomical landmarks.

METHODS

The study consisted of two parts. The first part assessed the lateral tunnel entrance for location and safety. The second part addressed the tunnel direction and safety upon exiting the calcaneum on the medial side. In the first part, 29 specimens were used to locate the anatomical insertion of the CFL based on the intersection of two lines related to the fibular axis and specific landmarks on the lateral malleolus. In the second part, 22 specimens were dissected to determine the position of the neurovascular structures at risk during tunnel drilling. Therefore, a method based on four imaginary squares using external anatomical landmarks was developed.

RESULTS

For the tunnel entrance on the lateral side, the mean distance to the centre of the CFL footprint was 2.8 ± 3.0 mm (0-10.4 mm). The mean distance between both observers was 4.2 ± 3.2 mm (0-10.3 mm). The mean distance to the sural nerve was 1.4 ± 2 mm (0-5.8 mm). The mean distance to the peroneal tendons was 7.3 ± 3.1 mm (1.2-12.4 mm). For the tunnel exit on the medial side, the two anterior squares always contained the neurovascular bundle. A safe zone without important neurovascular structures was found and corresponded to the two posterior squares.

CONCLUSION

Lateral landmarks enabled to locate the CFL footprint. Precautions should be taken to protect the nearby sural nerve. A safe zone on the medial side could be determined to guide safe tunnel direction. A calcaneal tunnel should be directed to the posterior inferior medial edge of the calcaneal tuberosity.