Posterior Inferior Tibiofibular Ligament Research Articles

Posterior Translation of the Fibula is a Critical Factor in the Stability of the Syndesmosis After Injury and Repair

Objectives:Anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and interosseous membrane (IOM) disruption is a predictive measure of residual symptoms after an ankle injury. Unstable syndesmotic injuries are typically treated surgically with cortical screw or suture button fixation. Previous studies have shown contradicting findings regarding the effects of partial syndesmotic injuries and different surgical fixation methods on tibiofibular kinematics. Thus, the objective of this study was to quantify tibiofibular joint motion with sequential disruption of the syndesmosis and with syndesmotic screw and suture button fixation compared to the intact ankle.Methods:Nine fresh-frozen human cadaveric specimens (mean age 60 yrs.; range 38-73 yrs.) were tested using a six degree-of-freedom robotic testing system. The subtalar joint was fused and the tibia and calcaneus were rigidly fixed to a robotic manipulator, while complete fibular length was maintained and fibular motion was unconstrained. A 5 Nm external rotation moment and 5 Nm inversion moment were independently applied to the ankle at 0°, 15°, and 30° plantarflexion and 10° dorsiflexion. Fibular motion with respect to the tibia was tracked by a 3D optical tracking system. Outcome variables included fibular medial-lateral (ML) translation, anterior-posterior (AP) translation, and external rotation (ER) in the following states: 1) intact ankle, 2) AITFL transected, 3) AITFL, PITFL, and IOM transected (complete injury), 4) 3.5 mm cannulated tricortical screw fixation, 5) suture button fixation. An ANOVA with a post-hoc Tukey analysis was performed for statistical analysis (*p < 0.05).Results:All significant differences in fibular motion between ankle states occurred during the inversion moment. An isolated AITFL injury caused significant increases in fibular posterior translation at 15° and 30° plantarflexion compared to the intact ankle. A complete syndesmotic injury caused significant increases in fibular posterior translation in all 4 ankle positions and in fibular ER at 0° flexion and 15° plantarflexion compared to the intact ankle. No significant differences were detected in fibular motion between an isolated AITFL injury and complete injury at any ankle positions. No significant differences existed between the tricortical screw fixation and the intact ankle. Significantly higher fibular posterior translation was observed with the suture button compared to the intact ankle at 0° flexion, 30° and 15° plantarflexion. (Figure 1)Conclusion:An isolated AITFL injury resulted in a significant increase in fibular posterior translation relative to the tibia, comparable to that a complete injury, especially in positions of plantarflexion. Current diagnostic protocols after injury focus on the evaluation of fibular ML translation. However, these findings show that it is important to also evaluate syndesmotic stability in the sagittal plane and at different ankle positions. Restoration of native tibiofibular kinematics is essential to prevent post-traumatic arthritis. Tricortical screw fixation was able to restore tibiofibular kinematics in all planes. However, suture button fixation was not able to restore tibiofibular AP translation, which suggests that physicians should critically evaluate fibular AP translation and individualize treatment of unstable ankle injuries when reconstructing the syndesmosis with suture button fixation.Figure 1.Posterior translation of the fibula relative to the tibia (mean ± standard deviation) during a 5Nm inversion moment at 0° flexion, 15° and 30° plantarflexion, and 10° dorsiflexion in different ankle states: intact ankle, isolated AITFL injury, complete injury, tricortical screw flixation using a 3.5mm screw, suture button fixation. *p < 0.05

Talar Motion is Constrained by Tricortical Screw Fixation of the Syndesmosis: A Cadaveric Robotic Study

Objectives:High ankle sprains are a common injury that occur in up to 11% of ankle sprains. Injury to the structures of the syndesmosis, the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and interosseous membrane (IOM), has been shown to be predictive of residual symptoms after ankle injury. When the syndesmosis is unstable, it is typically treated surgically with cortical screw fixation or suture button fixation. Studies have shown that a 1 mm lateral shift of the talus relative to the tibia significantly decreases the tibiotalar contact area by 42%. Thus, restoring the tibiotalar kinematics to those of the intact ankle with appropriate fixation is important to avoid accelerated tibiotalar arthritis. The objective of this study was to quantify tibiotalar joint motion after syndesmotic screw and suture button fixation compared to the intact ankle.Methods:Nine fresh-frozen human cadaveric specimens (mean age 60 yrs.; range 38-73 yrs.) were tested using a six degree-of-freedom robotic testing system. The subtalar joint was fused and the tibia and calcaneus were rigidly fixed to a robotic manipulator, while fibular length was maintained and fibular motion was unconstrained. Talar motion with respect to the tibia was measured using the robotic testing system. A 5 Nm external rotation moment and 5 Nm inversion moment were applied independently to the ankle at 0°, 15°, and 30° plantarflexion and 10° dorsiflexion. Outcome variables included talar medial-lateral (ML) translation, anterior-posterior (AP) translation, and internal/external rotation relative to the tibia in the following syndesmosis states: 1) intact, 2) AITFL transected, 3) AITFL, PITFL, and IOM transected, 4) 3.5 mm cannulated tricortical screw fixation, and 5) suture button fixation. An ANOVA with a post-hoc Tukey analysis was performed for statistical analysis. Statistical significance was set at p < 0.05.Results:There were significant differences in ML translation of the talus relative to the tibia between the tricortical screw fixation and the intact ankle. These significant changes were only present during states with no loads applied. Tricotical screw fixation resulted in a significant decrease in medial translation of the talus compared to the intact ankle at 30° plantarflexion and increased lateral translation at 0° flexion (p < 0.05) (Figure 1). The talus moved 1.1 mm less medially at 30° plantarflexion and 0.4 mm more laterally at 0° flexion in the tricortical screw fixation state compared to the intact ankle. The total medial translation of the talus relative to the tibia during plantarflexion decreased from 1.1 mm to only 0.4 mm. No significant difference in AP translation or external rotation of the talus existed between the tricortical screw fixation and the intact ankle. No significant differences existed in translation or rotation of the talus between the suture button fixation and intact ankle at any ankle positions.Conclusion:Suture button fixation restored tibiotalar motion in all planes, with no significant differences compared to the intact ankle. Tricortical screw fixation significantly increased lateral shift of the talus in a neutral ankle position and constrained motion during plantarflexion compared to the intact ankle, which can lead to accelerated tibiotalar arthritis. Thus, physicians should consider hardware removal after tricortical screw fixation for syndesmotic repair to avoid post-traumatic arthritis.Figure 1.Medial-lateral translation of the talus relative to the tibia with no loads applied. (Mean ± Standard Deviation), *p < 0.05

Anatomy of the Insertion of the Posterior Inferior Tibiofibular Ligament and the Posterior Malleolar Fracture

Category: Ankle Introduction/Purpose: The treatment of posterior malleolar fractures is developing. Our previous study on the anatomy of the posterior malleolar fracture identified only 49% of rotational push off fractures of the posterior malleolus had syndesmotic instabilities. This was against general thinking that fixation of such a fragment would stabilize the syndesmosis. Our aim in this study was to identify the extent of the posterior inferior tibiofibular ligament insertion on the posterior tibia and its relation to push off fractures. Methods: We examined 10 cadaveric lower limbs that had been preserved for dissection at the Human Anatomy and Resource Centre at Liverpool University in a solution of formaldehyde. The lower limbs were carefully dissected to identify the ligamentous structures on the posterior aspect of the ankle. Results: In all specimens, the tibial insertion of the PITFL encompassed 1/3 of the distal posterior tibia. In addition, the posterior intermalleolar ligament inserted onto the posterior tibia just medial to the tibialis posterior groove. Thus a rotational push off fracture would only cause syndesmotic injury if greater than a 3 rd of the posterior tibia was injured or occurred in combination with a ligamentous injury. This is in keeping with the clinical findings of only 49% syndesmotic instabilities with Haraguchi type 1 posterior malleolar fractures. Conclusion: Haraguchi type 1 posterior malleolar fractures (less than a 3 rd of the width of the posterior tibia) are unlikely to cause syndesmotic instabilities without the addition of a ligamentous injury.

Arthroscopic Characterization of Syndesmotic Instability

Category: Arthroscopy, Sports, Trauma, Other, Syndesmosis Introduction/Purpose: Ankle arthroscopy is increasingly used to diagnose syndesmostic instability by visualizing the distal tibiofibular articulation and applying a lateral fibular stress. Precisely where in the incisura one should measure potential diastasis, however, remains unclear. The purpose of this study was to determine where within the incisura one should assess coronal plane instability in purely ligamentous syndesmotic injuries when performing a lateral hook stress test (LHT). Methods: Twenty-two above-knee cadaveric specimens underwent ankle arthroscopy, first with intact ligaments and thereafter after each sequential step of syndesmotic and deltoid ligament transection. At each step, a standard 100 N hook test was applied through a lateral incision 5 cm proximal to the ankle joint and the coronal plane diastasis in the stressed and unstressed states were measured at both anterior and posterior third of the distal tibiofibular joint using calibrated probes ranged from 0.1 to 6.0 mm, with 0.1 mm of increments. Results: Anterior third diastasis did not change significantly when applying a LHT, neither in the intact state nor after any stage of ligament transection (P values ranging from p=0.61 to p=0.94). In contrast, posterior third diastasis increased significantly by applying stress at the intact state at the following stages of transection: posterior-inferior tibiofibular ligament (PITFL), PITFL plus interosseous ligament, all syndesmosis ligaments, and all syndesmosis ligaments plus superficial and deep deltoid ligament (P values ranging p=0.001 to p=0.031). Interobserver agreement was substantial (ICC = 0.81; 95% confidence interval, 0.44-0.92), and moderate (ICC = 0.73; 95% confidence interval, 0.36-0.87) for anterior and posterior third diastasis measurements, respectively. Conclusion: Syndesmotic ligament injury results in coronal plane instability of the distal tibiofibular articulation that is readily identified arthroscopically with a LHT and when measured in the posterior third of the incisura. Measurement at the anterior third of the incisura may miss such injuries.

Strain Distribution in the Anterior Inferior Tibiofibular Ligament, Posterior Inferior Tibiofibular Ligament, and Interosseous Membrane Using Digital Image Correlation.

Ligament repair and augmentation techniques can stabilize syndesmosis injuries. However, little is known about the mechanical behavior of syndesmotic ligaments. The aim of this study was to analyze full-field strain, strain trend under foot rotation, and subregional strain differences of the anterior inferior tibiofibular ligament (AITFL), posterior inferior tibiofibular ligament (PITFL), and interosseous membrane (IOM). Eleven fresh-frozen lower limbs were dissected to expose the AITFL, PITFL, and IOM. The foot underwent rotation from 0° to 25° internal and 35° external, with 3 ankle positions (neutral, 15° dorsiflexion, and 25° plantarflexion) and a vertical load of 430 N. Ligament strain was recorded using digital image correlation. The mean strain on the AITFL with 35° external rotation was greater in the proximal portion compared with distal portion in the neutral position ( P = .009) and dorsiflexion ( P = .003). The mean strain in the tibial insertion and midsubstance near tibial insertion were greater when compared with other regions ( P = .018 and P = .009). The subregions of mean strain in the PITFL and IOM groups were not significantly different. The strain trend of AITFL, PITFL, and IOM showed common transformation, just when the foot was externally rotated. The findings of this study show that a significantly high strain was observed on the proximal part and the midsubstance near the Chaput tubercle of the AITFL when the ankle was externally rotated. All 3 ligaments resisted the torque in the syndesmosis by external rotation of the foot. This study allows for better understanding of the mechanical behavior of the syndesmosis ligaments, which could influence the repair technique and AITFL augmentation techniques.

Role of the Deltoid Ligament in Syndesmotic Instability.

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. 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. 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). 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. Disruption of the DL appeared to destabilize the syndesmosis in the coronal plane when associated with partial disruption of the syndesmosis (AITFL and IOL).

Posterior Inferior Tibiofibular Ligament Release to Achieve Anatomic Reduction of Posterior Malleolar Fractures

We assessed the clinical and radiographic outcomes of posterior inferior tibiofibular ligament (PITFL) release to achieve anatomic reduction of posterior malleolar fractures (PMFs). Nineteen PMFs (>25% of tibial plafond) that could not be reduced after anatomic reduction of distal fibula fractures were managed by PITFL release. The syndesmosis was stressed intraoperatively and by 2 surgeons unaware of the postoperative measurements to increase reliability. The pre- and postoperative fracture gaps and articular step-offs were measured on lateral radiographs of all patients and computed tomography (CT) scans of 12. Tibiofibular clear space and overlap measures at the final follow-up visit were used to evaluate postoperative syndesmotic stability. Postoperative function was assessed using the American Orthopaedic Foot and Ankle Society (AOFAS) scale score. The mean pre- and postoperative fracture gap and step-off of the PMFs was 4.9 mm and 0.4 mm and 2.8 mm and 0.4 mm, respectively. On CT scan, the mean pre- and postoperative fracture gap and step-off was 5.2 mm and 0.5 mm and 3.3 mm and 0.6 mm, respectively. The preoperative and final follow-up tibiofibular clear space and overlap did not differ significantly. The mean follow-up period was 26.7 months, and the mean AOFAS scale score was 90.6 points at the final follow-up. Direct visualization and reduction of PMFs through PITFL release led to satisfactory clinical and radiographic outcomes without causing ankle instability.

The predictive value of MRI in the syndesmotic instability of ankle fracture.

Although many types of ankle fracture can be combined with syndesmosis injury, preoperative imaging studies rarely reveal instability of the syndesmosis. This study assessed the use of magnetic resonance imaging (MRI) for syndesmotic instability in patients with unstable ankle fracture. A total of 74 patients who were treated for Lauge-Hansen supination external rotation/Weber B type fracture or pronation external rotation/Weber C type fracture and who underwent MRI for preoperative assessment were enrolled. The MRI findings of the syndesmotic ligament and the results of an intraoperative stress test were evaluated. Twenty-six patients had a positive result on the intraoperative stress test for syndesmotic instability. The MRI findings of the syndesmotic ligaments revealed that complete tear of the posterior inferior tibiofibular ligament (PITFL) was the most reliable predictor of syndesmotic instability (sensitivity, 74%; specificity, 78%; positive predictive value, 54%). Interobserver agreement for the intraoperative stress test and MRI assessment was excellent, except for the MRI findings of the interosseous ligament (62% agreement; kappa, 0.3). Complete tear of the PITFL on MRI has additional diagnostic value for syndesmotic instability in ankle fracture. However, because the sensitivity might not be sufficient to justify the costs associated with MRI, cost-effectiveness should be considered.

Significant Increases in Sagittal Translation and Transverse Rotation of the Fibula Occur with Sequential Disruption of the Syndesmosis

This study demonstrates that significant fibular motion occurs with isolated AITFL disruption and only minimally increases with sequential PITFL and IOM transection. Clinical diagnostic protocol should be expanded to evaluate beyond ML translation of the fibula and account for sagittal and rotational displacements as well. Injury to the Anterior inferior tibiofibular ligament (AITFL), Posterior inferior tibiofibular ligament (PITFL) and Interosseus membrane (IOM) predicts residual symptoms in ankle sprains. Limited kinematic knowledge of the tibiofibular joint results in missed diagnosis and poor clinical outcomes. Lateral fibular displacement on radiologic assessment signifies syndesmotic disruption which dictates operative management. Previous studies demonstrated that fibular motion is multiplanar after injury. The purpose of this study is to determine increases in fibular motion with sequential syndesmotic injury and the contribution of the AITFL. Five fresh-frozen human cadaveric tibial plateau-to-toe specimens with a mean age of 58 years (range 38-73 years) were tested using a 6-degree-of-freedom robotic testing system. The tibia and calcaneus were rigidly fixed. The subtalar joint was fused. The full fibular length was maintained and fibular motion was unconstrained. A 5Nm external rotation moment and 5Nm inversion moment were applied to the ankle at 0°, 15°, and 30° plantarflexion and 10° dorsiflexion. The motion of the fibula was tracked by a 3D optical tracking system. Outcome variables included fibular medial-lateral (ML) translation, anterior-posterior (AP) translation, and external rotation (ER) during each max moment and flexion angle in the following conditions: 1) intact ankle, 2) AITFL transected, 3) PITFL and IOM transected. Statistical analysis included an ANOVA with a post-hoc Tukey analysis to compare the changes in fibular motion between the intact and injury models at each applied moment and flexion angle (*p<0.05). The only significant differences in fibular motion were during the 5Nm inversion moment. The posterior translation of the fibula was significantly greater with AITFL injury compared to the intact ankle at 15° and 30° plantarflexion. Significant increases in posterior translation between the intact ankle and AITFL, PITFL, and IOM injury exists at 0°, 15°, and 30° plantarflexion. No significant motion differences were observed between the AITFL injury and combined injury at any condition. When comparing the intact ankle and combined injury, significant increases in ER exist at 0° and 30° plantarflexion and 10° dorsiflexion. The only significant difference in ER between the intact ankle and AITFL injury exists at 0° plantarflexion. The data from this study showed that transecting the AITFL resulted in the largest increases fibular motion with only minimal further fibular displacement with transection of the PITFL and IOM. Total syndesmotic disruption creates significant fibular motion compared to the intact ankle but, a significant portion of the displacement of the fibula already occurs after isolated AITFL injury. A previous study demonstrated no measureable fibular ML displacement with syndesmosis injury but this was not supported by the current findings. This study utilized a novel setup with unconstrained motion in a full length, intact fibula. Basing clinical syndesmotic stability on ML translation alone could underestimate sagittal and rotation instability in AITFL injuries. Evaluating fibular AP translation and ER are not part of current standard diagnostic protocols. Physicians may consider more aggressive treatment of isolated AITFL injuries.

The effect of ankle distraction on arthroscopic evaluation of syndesmotic instability: A cadaveric study

BackgroundTo assist with visualization, orthopaedic surgeons often apply ankle distraction during arthroscopic procedures. The study aimed to investigate whether ankle distraction suppresses fibular motion in cadaveric specimens with an unstable syndesmotic injury. MethodsFourteen fresh-frozen above knee specimens underwent arthroscopic assessment with 1) intact ligaments, 2) after sectioning of the anterior inferior tibiofibular ligament, the interosseous ligament, and the posterior inferior tibiofibular ligament, and 3) after sectioning of the deep and superficial deltoid ligament. In all scenarios, the lateral hook test, anterior-posterior hook test, and posterior-anterior hook test were applied. Each test was performed with and without ankle distraction. Coronal plane anterior and posterior tibiofibular diastasis as well as sagittal plane tibiofibular translation due to the applied load were arthroscopically measured. FindingsTibiofibular diastasis in the coronal plane, as measured at both the anterior and posterior third of the incisura, was found to be significantly less when ankle distraction was applied, as compared to arthroscopic evaluation in the absence of distraction. In contrast, measurement of sagittal plane tibiofibular translation was not affected by ankle distraction. InterpretationSince arthroscopic findings of syndesmotic instability are subtle the differential values of the syndesmotic measurements taken on and off distraction are clinically relevant. To optimally assess syndesmotic instability one should evaluate the syndesmosis without distraction or focus on fibular motion in the sagittal plane when distraction is required.

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

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. 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. 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). 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. 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.

Anterior-Posterior Translation and Axial Rotation of the Fibula are Significantly Increased with Sequential Disruption of the Syndesmosis

Category: Ankle, Sports, Trauma Introduction/Purpose: Injury to the Anterior inferior tibiofibular ligament (AITFL), Posterior inferior tibiofibular ligament (PITFL) and Interosseus membrane (IOM) predicts residual symptoms in ankle sprains. Limited kinematic knowledge of the tibiofibular joint results in missed diagnosis and poor clinical outcomes. Lateral fibular displacement on radiologic assessment signifies syndesmotic disruption which dictates operative management. Previous studies demonstrated that fibular motion is multiplanar after injury. The objective of this study is to determine increases in fibular motion with sequential syndesmotic injury and the contribution of the AITFL. Methods: Five fresh-frozen human cadaveric tibial plateau-to-toe specimens with a mean age of 58 years (range 38-73 years) were tested using a 6-degree-of-freedom robotic testing system. The tibia and calcaneus were rigidly fixed. The subtalar joint was fused. The full fibular length was maintained and fibular motion was unconstrained. A 5 Nm external rotation and 5 Nm inversion moment were applied to the ankle at 0°, 15°, and 30° plantarflexion and 10° dorsiflexion. The motion of the fibula was tracked by a 3D optical tracking system. Outcome variables included fibular medial-lateral (ML) translation, anterior-posterior (AP) translation, and external rotation (ER) during each applied moment and flexion angle in the following conditions: 1) intact ankle, 2) AITFL transected, 3) PITFL and IOM transected. Statistical analysis included an ANOVA with a post-hoc Tukey analysis to compare the changes in fibular motion between the intact and injury models at each applied moment and flexion angle (*p&lt;0.05). Results: The only significant differences in fibular motion were during the 5 Nm inversion moment. The posterior translation of the fibula was significantly greater with AITFL injury compared to the intact ankle at 15° and 30° plantarflexion. Significant increases in posterior translation between the intact ankle and AITFL, PITFL, and IOM injury existed at 0°, 15°, and 30° plantarflexion. No significant motion differences were observed between the AITFL injury and combined injury at any condition. When comparing the intact ankle and combined injury, significant increases in ER existed at 0° and 30° plantarflexion and 10° dorsiflexion. The only significant difference in ER between the intact ankle and AITFL injury existed at 0° plantarflexion. Conclusion: This study showed that transecting the AITFL resulted in the largest increases in fibular motion with only minimal further increases after complete syndesmotic injury. Fibular displacement was primarily in the sagittal plane. This study utilized a novel setup with unconstrained motion in a full length, intact fibula. Measuring ML translation alone could underestimate sagittal and rotational instability of the syndesmosis in AITFL injuries. Evaluating fibular AP translation and ER are not part of current standard diagnostic protocols. Physicians may consider more aggressive treatment of isolated AITFL injuries.

Restoration of Tibiofibular Kinematics with a Tricortical Screw or Suture Button Fixation After Syndesmotic Ankle Injuries

Category: Ankle, Sports, Trauma Introduction/Purpose: Anterior inferior tibiofibular ligament (AITFL), Posterior inferior tibiofibular ligament (PITFL) and Interosseous membrane (IOM) disruption is a predictive measure of residual symptoms after ankle injury. In unstable injuries, the syndesmosis is treated operatively with cortical screw fixation or a suture button apparatus. Biomechanical analyses of suture button versus cortical screw fixation methods show contradicting results regarding suture button integrity and maintenance of fixation. The objective of this study is to quantify tibiofibular joint motion in syndesmotic screw and suture button fixation models compared to the intact ankle. Methods: Five fresh-frozen human cadaveric specimens (mean age 58 yrs.; range 38-73 yrs.) were tested using a 6-degree-of- freedom robotic testing system. The tibia and calcaneus were rigidly fixed to the robotic manipulator and the subtalar joint was fused. The full fibular length was maintained and fibular motion was unconstrained. Fibular motion with respect to the tibia was tracked by a 3D optical tracking system. A 5 Nm external rotation moment and 5 Nm inversion moment were applied to the ankle at 0°, 15°, and 30° plantarflexion and 10° dorsiflexion. Outcome variables included fibular medial-lateral (ML) translation, anterior-posterior (AP) translation, and external rotation (ER) in the following states: 1) intact ankle, 2) AITFL transected, 3) PITFL and IOM transected, 4) 3.5 mm cannulated tricortical screw fixation, 5) suture button fixation. An ANOVA with a post-hoc Tukey analysis was performed for statistical analysis (*p&lt;0.05). Results: Significant differences in fibular motion were only during the inversion moment. Fibular posterior translation was significantly higher with complete syndesmosis injury compared to the intact ankle at 0°, 15°, and 30° plantarflexion and the tricortical screw at 15° and 30°. Significantly higher fibular posterior translation was observed with the suture button compared to the intact ankle at 15° and 30 plantarflexion and to the tricortical screw at 15°. ER was significantly increased with complete injury compared to the tricortical screw at 0° and 30° plantarflexion. The suture button demonstrated significantly greater ER at 0° plantarflexion and 10° dorsiflexion compared to the intact ankle. The only significant difference in ML translation exists between the tricortical screw and complete injury at 30° plantarflexion. Conclusion: The suture button did not restore physiologic motion of the syndesmosis. It only restored fibular ML translation. Significant differences in AP translation and ER persisted compared to the intact ankle. The tricortical screw restored fibular motion in all planes. No significant differences were observed compared to the intact ankle. These findings are consistent with previous studies. This study utilized a novel setup to measure unconstrained motion in a full length, intact fibula. Physicians should evaluate AP translation and ER as critical fibular motions when reconstructing the syndesmosis with suture button fixation.

The Predictive Value of MRI for Syndesmotic Instability of Ankle Fracture

Category: Ankle, Trauma Introduction/Purpose: Although many ankle fractures are combined with syndesmosis injury, preoperative imaging studies rarely reveal instability of the syndesmosis. This study assessed the use of magnetic resonance imaging (MRI) for syndesmotic instability in patients who have an unstable ankle fracture. Methods: A total of 74 patients who were treated for Lauge-Hansen supination external rotation, Weber B type fracture or pronation external rotation, Weber C type fracture and who underwent MRI before surgery to evaluate syndesmosis injury were enrolled. The MRI findings of the syndesmotic ligament and the results of an intraoperative stress test were assessed. Results: Twenty-six patients had a positive result on the intraoperative stress test. Regarding the MRI findings of the syndesmotic ligaments, complete tear of the posterior inferior tibiofibular ligament (PITFL) was the most reliable predictor of syndesmotic instability (sensitivity, 0.62; specificity, 0.94; positive predictive value, 0.84). Interobserver agreements for the intraoperative stress test and MRI assessment were excellent, except for the MRI findings of the interosseous ligament (62% agreement; kappa, 0.3). Conclusion: On the basis of the study results, complete tear of the PITFL on MRI has additional diagnostic value for syndesmotic instability in ankle fracture.

Intraoperative Assessment of Syndesmotic Injury and How to Assess if the Syndesmosis is Reduced

Injuries to the tibiofibular syndesmosis are common, both as isolated injuries and as a component of rotational ankle fractures. Recent evidence suggests a high incidence of tibiofibular syndesmosis malreduction with poor clinical outcomes associated with syndesmotic malreduction. Despite the notable clinical consequences of malreduction and heightened awareness surrounding the issue of syndesmotic malreduction, intraoperative methods to assess the adequacy of syndesmotic reduction remain imperfect. Although postoperative axial computed tomographic (CT) scans are often used to assess the adequacy of syndesmotic reduction postoperatively, the routine use of intraoperative CT is limited by the availability of technology as well as the limited ability to perform side-by-side comparison with the uninjured ankle intraoperatively. Although more readily available for intraoperative assessment, fluoroscopy has consistently demonstrated shortcomings with respect to assessment of syndesmotic reduction. Although the literature clearly suggests that there is no perfect method to consistently obtain anatomic reduction of the syndesmosis, several intraoperative methods to optimize syndesmotic malreduction, including the importance of anatomic fracture fixation, open visualization of syndesmotic reduction, posterior inferior tibiofibular ligament repair or anatomic posterior malleolar fracture fixation, and deep deltoid ligament repair, have been suggested. The following will include a review of these concepts as well as relevant recent literature to provide a basis for improving methods to assess the adequacy of syndesmotic reduction intraoperatively.

Gravity Stress Radiographs and the Effect of Ankle Position on Deltoid Ligament Integrity and Medial Clear Space Measurements.

External rotation and gravity stress radiographs have been described to distinguish stable supination-external rotation-II (SER-II) ankle fractures from unstable SER-IV fractures. It has been previously shown that both external rotation and gravity stress views are equivalent in their ability to diagnose deltoid ligament injury. It has also been shown that the position of the ankle influences the external rotation stress radiograph. However, no data of ankle position exist for gravity stress radiographs. Eight fresh-frozen cadaveric ankles were dissected and destabilized sequentially according to the SER mechanism of ankle fractures, starting with the anterior inferior tibiofibular ligament, distal fibula osteotomy at the level of the syndesmosis, posterior inferior tibiofibular ligament, superficial deltoid ligament, and finally the deep deltoid ligament. Fluoroscopic radiographs were taken with gravity stress views in both neutral and plantarflexion. Measurements of both dorsal and the medial clear space were taken for each stage. The difference between the dorsal and medial clear space was measured. Positive predictive value (PPV) with a medial clear space cutoff of 5 mm was 80% in plantarflexion and 72.72% in neutral with a negative predictive value (NPV) of 100% in both positions. Using a 6-mm cutoff, the PPV improved to 100% and NPV remained 100% for both neutral and plantarflexion. When the difference measurement is used, a 1.0-mm difference yielded a PPV of 72% and an NPV of 100% in both neutral and plantarflexion. With a 1.5-mm cutoff, the PPV and NPV were 100% for both positions. The position of the ankle during gravity stress radiographs does not influence the clinical effectiveness of the images. Using larger references for stability, the PPV can be improved.

Arthroscopic Correlates of Subtle Syndesmotic Injury.

Arthroscopic criteria for identifying syndesmotic disruption have been variable and subjective. We aimed to quantify syndesmotic disruption arthroscopically using a standardized measurement device. Ten cadaveric lower extremity specimens were tested in intact state and after serial sectioning of the syndesmotic structures (anterior inferior tibiofibular ligament [AiTFL], interosseous ligament [IOL], posterior inferior tibiofibular ligament [PiTFL], deltoid). Diagnostic ankle arthroscopy was performed after each sectioning. Manual external rotational stress was applied across the tibiofibular joint. Custom-manufactured spherical balls of increasing diameter mounted on the end of an arthroscopic probe were inserted into the tibiofibular space to determine the degree of diastasis of the tibiofibular joint under each condition. A ball 3 mm in diameter reliably indicated a high likelihood of combined disruption of the AiTFL and IOL. Disruption of the AiTFL alone could not be reliably distinguished from the intact state. Use of a spherical probe placed into the tibiofibular space during manual external rotation of the ankle provided an objective measure of syndesmotic instability. Passage of a 2.5-mm probe indicated some disruption of the syndesmosis, but the test had poor negative predictive value. Passage of a 3.0-mm spherical probe indicated very high likelihood of disruption of both the AiTFL and the IOL. The findings challenge the previously used but unsupported standard of a 2-mm diastasis of the tibiofibular articulation for diagnosis of subtle syndesmotic instability.

Biomechanical Analysis of the Individual Ligament Contributions to Syndesmotic Stability.

Biomechanical data and contributions to ankle joint stability have been previously reported for the individual distal tibiofibular ligaments. These results have not yet been validated based on recent anatomic descriptions or using current biomechanical testing devices. Eight matched-pair, lower leg specimens were tested using a dynamic, biaxial testing machine. The proximal tibiofibular joint and the medial and lateral ankle ligaments were left intact. After fixation, specimens were preconditioned and then biomechanically tested following sequential cutting of the tibiofibular ligaments to assess the individual ligamentous contributions to syndesmotic stability. Matched paired specimens were randomly divided into 1 of 2 cutting sequences: (1) anterior-to-posterior: intact, anterior inferior tibiofibular ligament (AITFL), interosseous tibiofibular ligament (ITFL), deep posterior inferior tibiofibular ligament (PITFL), superficial PITFL, and complete interosseous membrane; (2) posterior-to-anterior: intact, superficial PITFL, deep PITFL, ITFL, AITFL, and complete interosseous membrane. While under a 750-N axial compressive load, the foot was rotated to 15 degrees of external rotation and 10 degrees of internal rotation for each sectioned state. Torque (Nm), rotational position (degrees), and 3-dimensional data were recorded continuously throughout testing. Testing of the intact ankle syndesmosis under simulated physiologic conditions revealed 4.3 degrees of fibular rotation in the axial plane and 3.3 mm of fibular translation in the sagittal plane. Significant increases in fibular sagittal translation and axial rotation were observed after syndesmotic injury, particularly after sectioning of the AITFL and superficial PITFL. Sequential sectioning of the syndesmotic ligaments resulted in significant reductions in resistance to both internal and external rotation. Isolated injuries to the AITFL resulted in the most substantial reduction of resistance to external rotation (average of 24%). However, resistance to internal rotation was not significantly diminished until the majority of the syndesmotic structures had been sectioned. The ligaments of the syndesmosis provide significant contributions to rotary stability of the distal tibiofibular joint within the physiologic range of motion. This study defined normal motion of the syndesmosis and the biomechanical consequences of injury. The degree of instability was increased with each additional injured structure; however, isolated injuries to the AITFL alone may lead to significant external rotary instability.

Gravity Stress Radiographs and Effect of Ankle Position on Deltoid Ligament Integrity &amp; Medial Clear Space

Category: Trauma Introduction/Purpose: External rotation and gravity stress radiographs have been described to distinguish stable Supination External Rotation-II (SER-II) ankle fractures from unstable SER-IV fractures. It has been previously shown both external rotation and gravity stress views are equivalent in their ability to diagnose deltoid ligament injury. It has also been shown that the position of the ankle influences the external rotation stress radiograph. However, no data of ankle position exists for gravity stress radiographs. Methods: 8 fresh-frozen cadaveric ankles were dissected and destabilized sequentially according to the SER mechanism of ankle fractures, starting with the anterior inferior tibiofibular ligament, distal fibula osteotomy at the level of the syndesmosis, posterior inferior tibiofibular ligament, superficial deltoid ligament, and finally the deep deltoid ligament. Fluoroscopic radiographs were taken with gravity stress views in both neutral and plantarflexion. Measurements of both dorsal and the medial clear space were taken for each stage. The difference between the dorsal and medial clear space was measured. Results: Positive predictive value (PPV) with a medial clear space cut off of 5 mm was 80% in plantar flexion and 72.72% in neutral with a negative predictive value (NPV) of 100% in both positions. Using 6 mm cutoff the PPV improved to 100% and NPV remained 100% for both neutral and plantar flexion. When the difference measurement is used a 1.0 mm difference yielded a PPV of 72% and a NPV of 100% in both neutral and plantarflexion. With a 1.5 mm cutoff the PPV and NPV was 100% for both positions Conclusion: The position of the ankle during gravity stress radiographs does not influence the clinical effectiveness of the images. By using larger references for stability, the PPV can be improved.

Effect of Posterior Malleolus Fracture on Syndesmosis Reduction

Category: Trauma Introduction/Purpose: Syndesmotic malreduction and the presence of posterior malleolus fractures negatively influence outcomes in rotational ankle fractures. While there are no universally accepted criteria for posterior malleolar fixation, it has recently been shown that posterior malleolar fixation contributed to the stability of the syndesmosis. However, little is known if and how anatomic or non-anatomic fixation of the posterior malleolus affects syndesmotic reduction. A study analyzing syndesmotic reduction in specimens with varying in size and quality of reduction of the posterior malleolus was conducted. Methods: Nine through-knee cadaveric specimens were randomized into two groups with small (a third of the fibular notch, n=4) and large (two-third of the fibular notch, n=5) posterior malleolar fragments. A model of stage IV supination external rotation injury after fibular repair was created by sharply releasing anterior inferior tibiofibular ligament, superficial and deep deltoid ligaments, and interosseous membrane. Posterior malleolar fracture with predefined sizing was created with preservation of posterior inferior tibiofibular ligament. High resolution CT scan was obtained in each specimen at the four stages; intact, neutral- axis syndesmotic clamping only, with anatomic fixation of the posterior malleolus, and with non-anatomic fixation of the posterior malleolus using a 4.8 mm interposed spacer. Measurement of syndesmotic reduction in both anteroposterior and mediolateral planes was made automatically using a validated technique assisted by custom-developed software at 1 cm proximal to the ankle joint. Results: The presence of either a neutral-axis clamping alone or with an anatomically reduced fracture fragment caused a slight anterior shift of the fibula that was more pronounced in the smaller fragment group. Two-way ANOVA indicated no significant effects of fragment size (p=0.73) or reduction (p=0.09) on AP fibular movement. However, presence of non-anatomical fixation caused the fibula to move significantly posteriorly in the presence of a large posterior malleolar fragment (p=0.03 and p=0.01 relative to the intact and clamping only states). In the mediolateral direction, a neutral-axis clamping alone and clamping with an anatomically reduced fracture fragment both increased medial translation of the distal fibula. The non-anatomic reduction model of the posterior malleolus associated with corresponding lateral displacement of the distal fibula. Conclusion: The overall anteroposterior reduction of the syndesmosis using neutral-axis clamping was generally not affected by posterior malleolar fracture except in a non-anatomic fixation of large fragments. Mediolateral syndesmotic reduction was affected by the conditions of posterior malleolar fixation with best results in anatomic fixation but the intact state was still not replicated. Malreduction of the posterior malleolus led to a corresponding syndesmotic malreduction. When a posterior malleolar fixation is indicated in cases with syndesmotic injury, anatomic fracture fixation is paramount as it can affect syndesmotic reduction especially with larger fragments.