Role of Lateral Ankle Ligaments in Vertical Stability of the Fibula: A Cadaveric Model.

BACKGROUND: In unstable ankle fractures, the role of the deltoid and syndesmosis ligaments has been widely studied. However, it is uncertain what the importance of the lateral ankle ligament complex (LALC) is in the vertical stability of the fibula. Given its anatomical position, it should prevent the proximal translation of the fibula. This study aims to evaluate the role of the LALC in stabilizing the fibula in the vertical plane. METHODS: Eleven below-knee cadaveric specimens were used in this study. Proximal traction of the fibula was performed by applying 50 N in the intact state and after sequential transection of the syndesmotic ligaments, anterior talofibular ligament (ATFL), and the calcaneofibular ligament (CFL). At each stage, the proximal displacement of the fibula was measured. One-way repeated measures analysis of variance with post hoc Bonferroni correction was carried out to determine any significant differences between the groups. A P value <.05 was considered statistically significant. RESULTS: The vertical displacement of the fibula in the intact state, and after sequential transection of syndesmotic ligaments, ATFL, and CFL was 1.96 ± 1.19 mm, 3.96 ± 1.33 mm, 5.9 ± 1.73 mm, and 10.22 ± 2.76 mm, respectively. There was no significant difference in the proximal displacement of the fibula between the intact and the syndesmotic ligaments groups (P < .05). However, when the syndesmotic ligaments were transected in conjunction with ATFL ± CFL, a significant difference was observed compared to the intact state (P < .001). CONCLUSION: The complete disruption of syndesmotic ligaments did not significantly increase the proximal displacement of the fibula. However, when the ATFL ± CFL were additionally disrupted, there was a significant increase in the vertical translation of the fibula. CLINICAL RELEVANCE: To our knowledge, this is the first study describing that LALC plays a paramount role in the vertical stability of the fibula. Concomitant syndesmosis and LALC should be suspected in an axially unstable fibular fracture with a significant proximal displacement.

Posterior Malleolar Fracture Assessment: An Independent Interobserver and Intraobserver Validation of Three Computed Tomography-Based Classifications.

BACKGROUND: Posterior malleolus fractures occur in up to 50% of all ankle fractures. Several classification systems exist for their characterization, especially under CT. However, those classifications do not report the level of agreement or do it incompletely. This study aims to independently assess three posterior malleolus fracture classifications (Haraguchi, Bartonícek/Rammelt, and Mason). METHODS: This study was designed according to the Guidelines for Reporting Reliability and Agreement Studies. Ninety-four CT scans of patients with ankle fractures that had posterior malleolus fractures were included. Posterior malleolus fractures were assessed by six evaluators (three attending foot and ankle surgeons and three orthopaedic surgery residents) according to Haraguchi, Bartonícek/Rammelt, and Mason classifications. All images were reassessed by the same evaluators in a random sequence 3 weeks later. The kappa (k) coefficient was used to determine the interobserver and intraobserver agreement. Statistical significance was established using P < 0.05 with a 95% confidence interval (CI). RESULTS: The interobserver agreement was moderate for Haraguchi, Bartonícek/Rammelt, and Mason classifications with a global k value of 0.52 (95% CI, 0.43 to 0.60), 0.53 (95% CI, 0.46 to 0.61), and 0.54 (95% CI, 0.47 to 0.62), respectively. The intraobserver agreement was substantial for Haraguchi, Bartonícek/Rammelt, and Mason classifications, with an overall k value of 0.70 (95% CI, 0.64 to 0.74), 0.73 (95% CI, 0.68 to 0.78), and 0.73 (95% CI, 0.69 to 0.78), respectively. Interobserver and intraobserver agreement among orthopaedic surgeons and residents had no significant difference. CONCLUSION: The current classifications for posterior malleolus fractures showed a substantial intraobserver agreement. Nevertheless, the interobserver agreement obtained was just moderate for all classifications, independent of the level of expertise of the evaluators.

Arthroscopic characterization of syndesmotic instability in the coronal plane: Exactly what measurement matters?

BACKGROUND: Although ankle arthroscopy is increasingly used to diagnose syndesmotic instability, precisely where in the incisura one should measure potential changes in tibiofibular space or how much tibiofibular space is indicative of instability, however, remains unclear. The purpose of this study was to determine where within the incisura one should assess coronal plane syndesmotic instability and what degree of tibiofibular space correlates with instability in purely ligamentous syndesmotic injuries under condition of lateral hook stress test (LHT) assessment. METHODS: Ankle arthroscopy was performed on 22 cadaveric specimens, first with intact ankle ligaments and then after sequential sectioning of the syndesmotic and deltoid ligaments. At each step, a 100N lateral hook test was applied through a lateral incision 5 cm proximal to the ankle joint and the coronal plane tibiofibular space in the stressed and unstressed states were measured at both anterior and posterior third of the distal tibiofibular joint, using calibrated probes ranging from 0.1 to 6.0 mm, in 0.1 mm of increments. The anterior and posterior points of measurements were defined as the junction between the anterior and middle third, and junction between posterior and middle third of the incisura, respectively. RESULTS: Anterior third tibiofibular space measurements did not correlate significantly with the degree of syndesmotic instability after transection of the ligaments, neither before nor after applying LHT at all the three groups of different sequences of ligament transection (P range 0.085-0.237). In contrast, posterior third tibiofibular space measurements correlated significantly with the degree of syndesmotic instability after transection of the ligaments, both with and without applying stress in all the groups of different ligament transection (P range <0.001-0.015). Stressed tibiofibular space measurements of the posterior third showed higher sensitivity and specificity when compared to the stressed anterior third measurements. Using 2.7 mm as a cut off for posterior third stressed measurements has both sensitivity and specificity about 70 %. CONCLUSION: Syndesmotic ligament injury results in coronal plane instability of the distal tibiofibular articulation that is readily identified arthroscopically with LHT when measured in the posterior third of the incisura. CLINICAL RELEVANCE: When applying LHT, tibiofibular space measurement for coronal plane instability along the anterior third of the incisura is less sensitive for identifying syndesmotic instability and may miss this diagnosis especially when subtle.

Do Coronal or Sagittal Plane Measurements Have the Highest Accuracy to Arthroscopically Diagnose Syndesmotic Instability?

BACKGROUND: To compare the accuracy of arthroscopic sagittal versus coronal plane distal tibiofibular motion toward diagnosing syndesmotic instability. METHODS: Arthroscopic assessment of the syndesmosis was performed on 21 above-knee cadaveric specimens, first with all ligaments intact and subsequently with sequential transection of the anterior inferior tibiofibular ligament, the interosseous ligament, the posterior inferior tibiofibular ligament, and the deltoid ligament. A lateral hook test, an anterior-to-posterior (AP) translation test, and a posterior-to-anterior (PA) translation test were performed under 100 N of applied force. Anterior and posterior third coronal plane diastasis and AP and PA sagittal plane fibular translations were measured relative to the static tibia. RESULTS: Receiver operating characteristic (ROC) curve analysis revealed that the area under the curve (AUC) was higher for the combined AP and PA sagittal measurements (AUC, 0.91; accuracy, 83.5%; sensitivity, 78%; specificity, 89%) than the coronal plane measurements (anterior third: AUC, 0.65; accuracy, 60.5%; sensitivity, 63%; specificity, 59%; posterior third: AUC, 0.73; accuracy, 68.5%; sensitivity, 80%; specificity, 57%) (P < .001), underscoring the higher accuracy of sagittal plane measurements. CONCLUSION: Arthroscopic measurement of sagittal plane fibular translation is more accurate than coronal plane diastasis for evaluating syndesmotic instability. CLINICAL RELEVANCE: Clinicians should focus on distal tibiofibular motion in the sagittal plane when arthroscopically evaluating suspected syndesmotic instability. LEVEL OF EVIDENCE: Biomechanical cadaveric study.

Arthroscopic Assessment of Syndesmotic Instability in the Sagittal Plane in a Cadaveric Model.

BACKGROUND: Syndesmotic instability is multidirectional, occurring in the coronal, sagittal, and rotational planes. Despite the multitude of studies examining such instability in the coronal plane, other studies have highlighted that syndesmotic instability may instead be more evident in the sagittal plane. The aim of this study was to arthroscopically assess the degree of syndesmotic ligamentous injury necessary to precipitate fibular translation in the sagittal plane. METHODS: Twenty-one above-knee cadaveric specimens underwent arthroscopic evaluation of the syndesmosis, first with all syndesmotic and ankle ligaments intact and subsequently with sequential sectioning of the anterior inferior tibiofibular ligament (AITFL), the interosseous ligament (IOL), the posterior inferior tibiofibular ligament (PITFL), and deltoid ligament (DL). In all scenarios, an anterior to posterior (AP) and a posterior to anterior (PA) fibular translation test were performed under a 100-N applied force. AP and PA sagittal plane translation of the distal fibula relative to the fixed tibial incisura was arthroscopically measured. RESULTS: Compared with the intact ligamentous state, there was no difference in sagittal fibular translation when only 1 or 2 ligaments were transected. After transection of all the syndesmotic ligaments (AITFL, IOL, and PITFL) or after partial transection of the syndesmotic ligaments (AITFL, IOL) alongside the DL, fibular translation in the sagittal plane significantly increased as compared with the intact state (P values ranging from .041 to <.001). The optimal cutoff point to distinguish stable from unstable injuries was equal to 2 mm of fibular translation for the total sum of AP and PA translation (sensitivity 77.5%; specificity 88.9%). CONCLUSION: Syndesmotic instability appears in the sagittal plane after injury to all 3 syndesmotic ligaments or after partial syndesmotic injury with concomitant deltoid ligament injury in this cadaveric model. The optimal cutoff point to arthroscopically distinguish stable from unstable injuries was 2 mm of total fibular translation. CLINICAL RELEVANCE: These data can help surgeons arthroscopically distinguish between stable syndesmotic injuries and unstable ones that require syndesmotic stabilization.

Role of the Deltoid Ligament in Syndesmotic Instability.

BACKGROUND: The deltoid ligament (DL) is the principal ligamentous stabilizer of the medial ankle joint. Little is known, however, about the contribution of the DL toward stabilizing the syndesmosis. The aim of this study was to arthroscopically evaluate whether the DL contributes to syndesmotic stability in the coronal plane. METHODS: Eight above-knee cadaveric specimens were used in this study. A lateral hook test was performed by applying 100 N of lateral force to the fibula in the intact state and after sequential transection of the DL, anterior-inferior tibiofibular ligament (AITFL), interosseous ligament (IOL), and posterior-inferior tibiofibular ligament (PITFL). At each stage, distal tibiofibular diastasis was measured arthroscopically at both the anterior and posterior third of the incisura and compared to stress measurements of the intact syndesmosis. Measurements were performed using probes ranging from 0.1 to 6.0 mm, with 0.1-mm increments. RESULTS: There was no significant increase in diastasis at either the anterior or posterior third of the tibiofibular articulation after isolated DL disruption, nor when combined with AITFL transection. In contrast, a significant increase in diastasis was observed following additional disruption of the IOL (anterior and posterior third diastasis, P= .012 and .026, respectively), and after transection of all 3 syndesmotic ligaments (anterior and posterior third diastasis, P=.001 and .001, respectively). CONCLUSION: When evaluating the syndesmosis arthroscopically in a cadaveric model under lateral stress, neither isolated disruption of the DL nor combined DL and AITFL injuries destabilized the syndesmosis in the coronal plane. In contrast, the syndesmosis became unstable if the DL was injured in conjunction with partial syndesmotic disruption that included the AITFL and IOL. CLINICAL RELEVANCE: Disruption of the DL appeared to destabilize the syndesmosis in the coronal plane when associated with partial disruption of the syndesmosis (AITFL and IOL).

Effect of Sequential Sectioning of Ligaments on Syndesmotic Instability in the Coronal Plane Evaluated Arthroscopically.

BACKGROUND: Arthroscopic evaluation of the syndesmosis allows direct visualization of syndesmotic instability. The purpose of this study was to determine the minimum degree of ligamentous injury necessary to destabilize the syndesmosis in the coronal plane when assessed arthroscopically and pinpoint where such instability should be measured within the incisura. METHODS: Fourteen cadaveric specimens were divided into 2 groups and arthroscopically assessed first with the syndesmosis intact and then following serial differential ligamentous transection. Group 1 (n = 7): anterior-inferior tibiofibular (AITFL), interosseous (IOL), posterior-inferior tibiofibular (PITFL), and deltoid (DL) ligament. Group 2 (n = 7): PITFL-IOL-AITFL-DL. At each step, a standard 100-N lateral hook test was applied and tibiofibular coronal plane diastasis measured arthroscopically at both the anterior and posterior third of the incisura. These measurements were in turn compared with those of the stressed intact ligamentous state. RESULTS: There was no significant syndesmotic instability measured at either the anterior or posterior margin of the incisura after transection of a singular ligament (AITFL or PITFL) or after the IOL was additionally transected. Diastasis at the posterior margin was significantly increased when all syndesmotic ligaments were sectioned (group 1: P = .018; group 2: P = .008), but this was not noted along the anterior margin. Diastasis at the anterior margin reached significance only with complete transection of syndesmosis and DL (group 1: P < .001; group 2: P = .044). CONCLUSION: Under arthroscopic evaluation, the syndesmosis becomes unstable in the coronal plane only when all syndesmotic ligaments are transected, which should preferentially be measured at the posterior margin of the incisura. Anteriorly, diastasis becomes apparent only with addition of DL disruption, although this added finding may aid in diagnosis of occult deltoid injury. CLINICAL RELEVANCE: AITFL, IOL, and PITFL need to be injured to produce coronal plane syndesmotic instability. Arthroscopic assessment of such instability should occur along the posterior margin of the incisura. When they exist, similar findings anteriorly suggest concomitant deltoid injury.