Continuous and Connective Fibers of the Lateral Ankle Ligament Complex

The calcaneofibular ligament groove at the inferior fibula, an ultrasonographic anatomical landmark

PURPOSE

Calcaneofibular ligament (CFL) injuries are harder to diagnose than anterior talofibular ligament (ATFL) ones. This study aimed to clarify the fibular attachment of the CFL and verify the bony landmark for evaluating the CFL on ultrasonography.

METHODS

Fifty-nine ankles were used in this anatomical study. To confirm the control function of the CFL, we performed passive movement manually using cadaveric ankles and observed the ankle positions where the CFLs were tense. Histological observation of CFL attachment of the fibula was performed using Masson's trichrome stain. The ATFL and CFL were removed, and the bone morphology of the CFL attachment and inferior fibular end was imaged using a stereomicroscope and a 3D scanner. Using ultrasonography, we evaluated the bone morphology of the fibular attachment of the CFL in short-axis images of 27 healthy adult ankles.

RESULTS

The CFL was tensed according to ankle motions: supination, maximum dorsi flexion, maximum plantar flexion, and mild plantar flexion-external rotation. Below the CFL attachment of the fibula was a slight groove between the inferior tip and the obscure tubercle of the fibula. This groove was observed in 81.5% of cases using short-axis ultrasonography.

CONCLUSION

The CFL was tensed in various ankle positions to control the movements of the talocrural and subtalar joints. There was a slight groove at the inferior end of the fibula where the CFL coursed downward. We called it the CFL groove and proposed that it could serve as a landmark for the short-axis image of ultrasonography.

Difference in the fibular attachment structure between the superior and inferior fascicles of the anterior talofibular ligament using ultrasonography and histological examinations

PURPOSE

The anterior talofibular ligament (ATFL) is divided into superior (SB) and inferior bands (IB). Although the differences in length and width are known, the structure of the fibular attachment had not been elucidated. The present study aimed to clarify the differences in the fibular attachment structure between ATFL's SB and IB using cross-sectional images along the ligament.

METHODS

An anatomical study using 15 formalin-fixed ankles was performed. The lateral ankle ligament complex was collected after a longitudinal image of SB/IB was visualized by ultrasonography. The specimens were decalcified and sectioned longitudinally at the center of SB/IB using a microtome. Histological evaluation of the enthesis structure at the fibular attachment of SB/IB was performed using hematoxylin-eosin and Masson's trichrome stains.

RESULTS

A fibrillar pattern could not be observed in the longitudinal image at the IB level by ultrasonography. The lengths of ATFL's SB and IB were 20.6 ± 1.6 and 15.3 ± 1.3 mm, respectively, with thicknesses of 1.8 ± 0.4 and 1.0 ± 0.4 mm, respectively. The ATFL's IB was significantly shorter and thinner than the ATFL's SB. The fibular attachment of ATFL's SB had distinct enthesis structure, whereas in the attachment structure of the ATFL's IB, there were several variations including a type with a narrower enthesis structure than the ATFL's SB and a type that merged with or wrapped around the calcaneofibular ligament.

CONCLUSION

The fibular attachment structure between ATFL's SB and IB differs. Our results could be useful information when performing ultrasonography and MRI diagnosis.

Straight Form of Calcaneofibular Ligament as a Three-Dimensional Magnetic Resonance Imaging Sign in Diagnosis of Calcaneofibular Ligament and Anterior Talofibular Ligament Inferior Fascicle Injury

The present study was performed to investigate the morphological characteristics of the calcaneofibular ligament (CFL) and evaluate its relationship to the anterior talofibular ligament (ATFL) in patients with lateral ankle ligament injury using 3-dimensional magnetic resonance imaging (3D-MRI). This retrospective study involved 35 patients with lateral ankle ligament injury and 24 patients without a history of ankle trauma and a bone abnormality as controls. Reconstructed 3D-MRI was used to classify the form of the CFL as curved, wavy, or straight. The presence/absence of continuity between the fibula and CFL was evaluated in the 35 patients with injury, who were divided into 2 groups (continuity and discontinuity groups). The number of fascicles in the ATFL and the continuity between the distal end of the fibula and the proximal end of the ATFL were then evaluated. Among the patients with injury, 54.3% had the curve type of CFL, 34.3% had the wave type, and 11.4% had the straight type. In the control group, 62.5% had the curve type, 37.5% had the wave type, and none had the straight type. Continuity between the fibula and CFL was seen in 88.6%, and discontinuity was seen in 11.4%. Additionally, 85.7% had double fascicles in the ATFL. Inferior fascicle discontinuity between the ATFL and fibula was found in 13.3% with a double-fascicle ATFL; in all of these patients, the form of the CFL was straight and exhibited inferior fascicle discontinuity. The straight form of CFL could be a 3D-MRI sign in the diagnosis of CFL and ATFL inferior fascicle injury.

Relationship between inferior fascicle of anterior talofibular ligament and articular capsule in lateral ankle ligament complex

PURPOSE

The lateral ankle ligament complex (LALC) is composed of anterior talofibular (ATFL), calcaneofibular (CFL), and posterior talofibular (PTFL) ligaments, all of which have a connection/continuous fiber. However, the structural link between the LALC and the articular capsule remains unknown. The goal of our study was to determine the connection between ATFL's inferior fascicle and the articular capsule.

METHODS

In this study, we utilized 84 formalin-fixed ankles to elucidate the structure of LALC. Between ATFL and CFL, the bundle number of ATFL and arciform fiber was investigated. The specimens were decalcified and sectioned coronally using a freezing microtome, in the case of double bundles of ATFL, to study the connection between the inferior fascicle of ATFL and the articular capsule.

RESULTS

ATFL had a single (25%), double (74%), and triple (1%) bundle number, respectively. The arciform fiber connecting the ATFL and the CFL was found in the superficial layer of all ankles (100%). There were two types of relationships between the inferior fascicle of ATFL and the articular capsule: 36 ankles (58%) were extracapsular, and 26 of 62 ankles (42%) were integrated with the inferior-lateral articular capsule. There are two kinds of relationships between the inferior fascicle of the ATFL and the articular capsule: extracapsular and integrated-capsular.

CONCLUSIONS

The inferior fascicle of ATFL has a variant and integrated-capsular type is reinforced inferior-lateral articular capsule and enters the joint to form continuous fibers with PTFL, making LALC. These anatomical findings are helpful in ultrasonography diagnosis and arthroscopic ankle surgery.