Posterior Inferior Tibiofibular Ligament Research Articles

Effect of Distal Tibiofibular Destabilization and Syndesmosis Compression on the Flexibility Kinematics of the Ankle Bones: An In Vitro Human Cadaveric Model.

Overcompression of the distal tibiofibular syndesmosis during open reduction and internal fixation of ankle fracture may affect multidirectional flexibility of the ankle bones. Ten cadaveric lower limbs (78.3±13.0 years, 4 female, 6 male) underwent biomechanical testing in sagittal, coronal, and axial rotation with degrees of motion quantified. The intact force (100%) was the force needed to compress the syndesmosis just beyond the intact position, and overcompression was defined as 150% of the intact force. After intact testing, the anterior inferior tibiofibular ligament (AITFL), interosseus membrane (IOM), and posterior inferior tibiofibular ligament (PITFL) were sectioned and testing was repeated. The IOM and AITFL were reconstructed in sequence and tested at 100% and 150% compression. Overcompression of the syndesmosis did not significantly reduce ROM of the ankle bones for any loading modality (P > .05). IOM+AITFL reconstruction restored distal tibiofibular axial rotation to the intact condition. Axial rotation motion was significantly lower with AITFL fixation compared with IOM fixation alone (P < .05). The proximal tibiofibular syndesmosis demonstrated significantly higher motion in axial rotation with all distal reconstruction conditions. As assessed by direct visualization, overcompression of the distal tibiofibular syndesmosis did not reduce ROM of the ankle bones. Distal tibiofibular axial rotation was significantly lower with IOM+AITFL fixation compared with IOM augmentation alone. Distal tibiofibular axial rotation did not differ significantly from the intact condition after combined IOM+AITFL fixation. Dynamic fixation of the distal tibiofibular syndesmosis resulted in increased axial rotation at the proximal tibiofibular syndesmosis. These biomechanical data suggest that inadvertent overcompression of the distal tibiofibular syndesmosis when fixing ankle fractures does not restrict subsequent ankle bone ROM. The AITFL is an important stabilizer of the distal tibiofibular syndesmosis in external rotation. controlled laboratory study.

Unveiling Syndesmotic Malreduction: A Proof-of-Concept towards Portable Ultrasound Detection.

To evaluate the utility and diagnostic performance of portable handheld ultrasound for evaluating fibular rotation at the distal tibiofibular articulation after syndesmotic disruption. Four above-the-knee cadaveric specimens were included. Syndesmotic disruption was precipitated by transecting the Anterior Inferior Tibiofibular Ligament, Interosseous Ligament, and Posterior Inferior Tibiofibular Ligament. Thereafter, a proximal fibular osteotomy was performed, and three conditions were modeled at the distal syndesmosis: 1) reduced, 2) 5 degree internal rotation malreduction, and 3) 5 degree external rotation malreduction. Two blinded observers performed separate ultrasonographic examinations for each condition at the level of both the anterior and posterior distal tibiofibular articular surfaces. Syndesmotic gap penetrance, defined as the ability of the P-US to generate signal between the distal fibula and tibia at the level of the incisura, was graded positive if the sonographic waves penetrated between the distal tibiofibular joint and negative if no penetrating waves were detected. The accuracy measures of the anterior and posterior gap penetrance were evaluated individually. Our preliminary results showed that posterior gap penetrance showed good performance when detecting either internal or external rotational malreduction of the fibula with very good specificity (87.5%) and PPV (90.0%). On the other hand, the anterior gap penetrance showed limited performance when detecting either form of rotational malreduction. We introduced a novel sign, the "gap penetrance sign", best measured from the posterior ankle, which can accurately detect syndesmotic malreduction using P-US in a manner that does not require specific quantitative measurements and is readily accessible to early P-US users.

Posterior Ankle Impingement: It's Not Only About the Os Trigonum.

Os trigonum and Stieda process are common etiologies for posterior ankle impingement syndrome (PAIS), and diagnosis is typically made by radiographs, computed tomographic, or magnetic resonance imaging. However, these static tests may not detect associated soft tissue and bony pathologies. Posterior ankle and hindfoot arthroscopy (PAHA) is dynamic, providing at least ×8 magnification with full anatomical visualization. The primary aim of this study was to report the prevalence of associated conditions seen with trigonal impingement treated with PAHA. In this retrospective comparative study, patients who underwent PAHA for PAIS due to trigonal impingement, from January 2011 to September 2016, were reviewed. Concomitant open posterior procedures and other indications for PAHA were excluded. Demographic data were collected with pre- and postoperative diagnosis, arthroscopic findings, type of impingement, location, associated procedures, and anatomical etiologies. Trigonal impingements were divided in os trigonal or Stieda and subgrouped as isolated, with flexor hallucis longus (FHL) disorders, with FHL plus other impingement, and with other impingement lesions. A total of 111 ankles were studied-74 os trigonum and 37 Stieda. Isolated trigonal disorders accounted for 15.3% of PAIS (n = 17). Cases having associated conditions had a mode of 3 additional pathologies. FHL disorders were found in 69.4%, subtalar impingement in 32.4%, posteromedial ankle synovitis in 25.2%, posterolateral ankle synovitis in 22.5%, and posterior inferior tibiofibular ligament impingement in 19.8% of cases. Associated pathologies were observed in 58.6% of cases when FHL was not considered. Significant differences were noted comparing os and Stieda (isolated: 20.3% to 5.4%, P = .040; FHL plus others: 35.1% to 59.5%, P = .015). Trigonal bone (os trigonum or Stieda) was found to cause impingement in isolation in a small proportion of cases even when the FHL was considered part of the same disease spectrum. This should alert surgeons when considering removing trigonal impingement. Open approaches may limit the visualization and assessment of associated posterior ankle and subtalar pathoanatomy, thus possibly overlooking concomitant causes of PAIS. Level III, retrospective comparative study.

Radiological landmark of syndesmotic ligament complex by magnetic resonance imaging correlate with fibula free flap harvesting procedure

Preservation of syndesmotic ligaments is crucial for preventing adverse sequelae at the donor site following free fibula osteocutaneous flap harvesting. This study sought to determine the relationship between distal tibiofibular ligaments and the fibular segment to identify radiological landmarks that facilitate safe and precise flap. The distances between the distal tibiofibular ligaments (anterior inferior tibiofibular ligament [AITFL], posterior inferior tibiofibular ligament [PITFL]) and the fibular segment, as well as the lower border of the interosseous membrane, were measured on magnetic resonance imaging (MRI) scans of 296 patients without any perceivable ankle abnormalities. The mean distances (± SD) between the distal end of the fibula and the AITFL, PITFL, and lower interosseous membrane border were 3.0 ± 0.4 cm, 2.6 ± 0.4 cm, and 3.9 ± 0.6 cm, respectively. The distance between the talar dome and the PITFL exhibited a range of 0.0–0.5 cm. Our findings support preserving a distal fibular remnant of at least 4 cm to avoid injury to the syndesmotic ligament throughout fibula osteocutaneous flap harvesting. The talar dome could serve as a useful radiological landmark for identifying the upper border of PITFL during preoperative evaluation, and thus facilitating precise and safe flap procurement.

Should all Small Shell Posterior Malleolar Fractures be Considered for Fixation? Results from a 3D Fracture Mapping Study

Category: Ankle; Trauma Introduction/Purpose: Approximately 10-15% of posterior malleolar fractures (PMFs) are "small shell," extra-articular fragments. Current classification systems present difficulties to perform a uniform typification of PMFs and contain no consensus on whether they should be fixed. Anatomical studies have identified two distinct components of the posterior inferior tibiofibular ligament (PITFL); the superficial band is thought to be more important than its deep counterpart in imparting syndesmotic stability. However, the involvement of one or both bands of the PITFL by small shell PMFs has not been evaluated so far. Hence, we conducted this study to perform 3D mapping of small shell PMFs and to determine whether surgeons should fix these routinely. Methods: Ankle fracture patients with a ‘small shell’ PMF (Haraguchi 3/Mason 1/Bartoníček 1 or 2) were included. Demographics, radiological features, treatment, and outcomes were recorded. 3D models of the fractured tibiae were generated from CT scans and superimposed on a statistical shape model of the right tibia, which served as a template. Fracture lines along with footprints of superficial and deep PITFL were marked on the template. 3D fracture heat maps were generated. Size of the fracture fragments and involvement of the superficial and deep PITFL footprints were quantified using a custom MATLAB script (Figure 1). Sparing of the footprint was defined as an overlap of &lt; 1% between the fracture line and the footprint areas. Odds ratios (OR) with 95% confidence intervals (CI) were determined to determine which variables correlated with sparing of the PITFL footprint; P-values of &lt; 0.05 were considered significant. Results: Thirty-nine patients were included. The superficial PITFL footprint was spared in 15 (38%), deep PITFL in 10 (26%), and both in 4 cases (10%). Males and Weber C fractures had a higher likelihood of sparing the superficial and deep PITFL footprints, respectively (P = 0.04). Supination external rotation (SER) patterns were less likely to demonstrate syndesmotic widening if either PITFL footprint was spared. Direct fixation of the PMF was done in 1 case; syndesmotic fixation in 25 cases and in 14 cases, no syndesmotic fixation was done. Of these, 11 were SER injuries where stability was achieved after fixation of medial and lateral malleoli. In 1 SER and pronation external rotation (PER) injury case, the syndesmosis was stable after fixation of a large Chaput fragment. Conclusion: This study demonstrated that 48% of small shell PMFs spare either the superficial or deep footprint of the PITFL; in 10% both PITFL footprints were spared. Hence, 58 % of small-shell PMFs may not benefit from direct fixation. Additionally, SER injuries with small shell PMFs that spare either PITFL footprint may not demonstrate radiographic instability and may not need direct or indirect fixation after addressing other components of the ankle fracture. However, given the fact that syndesmotic stability is not dictated by the PITFL alone, it remains prudent to stress the syndesmosis per-operatively to determine if syndesmotic fixation is needed.

Effect of Distal Tibiofibular Syndesmosis Overcompression on the Biomechanical Properties of the Ankle Bones: An In Vitro Cadaveric Model

Category: Trauma; Ankle Introduction/Purpose: Overtightening of the distal tibiofibular syndesmosis during open reduction and internal fixation (ORIF) of ankle fractures remains a clinical concern, and there are limited data delineating the effect of syndesmosis overcompression on subsequent range of motion of the ankle joint bones. The primary objective of the current study was to determine the effect of syndesmotic overcompression on the relative range of motion (ROM) of the tibia, fibula, and talus, and to determine the syndesmotic fixation construct that most accurately restores native motion. Methods: Ten cadaveric lower limbs were utilized (78.3±13.0 yrs, 4F; 6M). A musculoskeletal simulator at ±7.5 Nm was used to test flexibility in dorsiflexion-plantarflexion, inversion-eversion, and internal-external rotation. After intact testing, syndesmotic probes were used to arthroscopically measure the intact position of the distal tibiofibular syndesmosis. The force needed to compress the syndesmosis just beyond the intact position represented the intact force (100%), and overcompression was defined as 150% of the intact force. The anterior inferior tibiofibular ligament (AITFL), interosseus membrane (IOM), and posterior inferior tibiofibular ligament (PITFL) were then sectioned. Testing was repeated for destabilized, IOM reconstruction at 100% compression and 150% overcompression, IOM reconstruction plus AITFL fixation at 100% compression and 150% overcompression, and AITFL fixation alone. ROM data was reported as a percentage of the intact condition. Repeated measures ANOVA and Bonferroni post hoc test were performed to assess differences between conditions with p&lt; 0.05. Results: Average force needed to compress the syndesmosis was 71.0 ± 22.2 N. There was a significant increase in distal tibiofibular ROM in internal and external rotation for all conditions compared to intact (Figure 1) (p &lt; 0.05). In the axial plane, reconstruction of the IOM membrane did not restore the intact condition and was similar to the destabilized treatment, regardless of compression force. The addition of AITFL fixation significantly reduced distal tibiofibular motion compared to IOM reconstructions alone, but still did not approach the intact condition. Overcompression of the syndesmosis did not significantly affect relative ROM of the ankle bones in any plane (p&gt;0.05). Changes in the proximal tibiofibular ROM were similar in magnitude and direction as the distal tibiofibular ROM for all conditions. Conclusion: In the current study, overcompression of the distal tibiofibular syndesmosis did not restrict relative ROM of the tibia, fibula, or talus. Reconstructing the AITFL in addition to the IOM decreased tibiofibular ROM, particularly in the axial plane. In the clinical setting, surgical reconstruction with dynamic fixation of the distal tibiofibular syndesmosis may result in increased ROM and mechanical stress at the proximal tibiofibular articulation.

Treatment of Intra-Articular Lesions After Posterior Inferior Tibiofibular Ligament Injury: A Case Series of Elite Rugby Players.

Surgical intervention is not typically used to treat symptoms after mild tibiofibular ligament injuries without ankle dislocation or subluxation. To describe outcomes in patients arthroscopically treated for unique intra-articular lesions after sustaining syndesmosis injury of the ankle. Case series; Level of evidence, 4. A total of 11 elite male rugby players with a mean age of 21.0 years (range, 17-28 years) were referred to our hospital for prolonged posterior ankle pain after a high ankle sprain during rugby football. The patients were examined using standing view radiography, computed tomography (CT) and magnetic resonance imaging (MRI) to determine the extent of ligament damage. Posterior ankle arthroscopy was performed to examine intra-articular lesions. The patients were evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) ankle/hindfoot rating scale and sports activity score of the Self-Administered Foot Evaluation Questionnaire (SAFE-Q). The average reduced tibiofibular overlap on the standing mortise view was 1.2 mm (range, 0.5-2.0 mm) compared with the opposite ankles. Mason type 1 fracture was detected on CT in 6 patients, and ossification of the interosseous membrane was detected in 2 patients. A bone bruise in the posterior malleolus was observed on MRI in all but 1 patient. Intra-articular fragments located in the posterior ankle were observed and removed arthroscopically. Symptoms improved rapidly after arthroscopic treatment in all patients. All patients returned to rugby games at a median of 11 weeks postoperatively. The median AOFAS scores improved from 77 preoperatively to 100 postoperatively (P < .01), and the median SAFE-Q sports activity subscale score improved from 49.4 to 100 (P < .01). All unique intra-articular lesions that developed in rugby football players after syndesmosis injury were able to be treated arthroscopically. Patients returned to playing rugby football without syndesmosis reduction. Posterior ankle arthroscopy was effective in patients with residual symptoms after syndesmosis injury.

Quantitative Evaluation of the Influence of Posterior Malleolus Fracture and Fixation on the Rotational Stability of the Ankle

BackgroundThis study aimed to analyze quantitative correlation between the posterior malleolus fracture and fixation and the rotational stability of the ankle and to explore supplementary surgical indications for posterior malleolus fracture.MethodsTwenty fresh frozen cadaver specimens were selected and dissected. Based on the tibial insertion of the ligament complex, the model for the supination external rotation stage 3 ankle fracture with a posterior malleolar fragment and syndesmosis diastasis was created. The area threshold of the posterior tibial insertion of posterior malleolus fracture was biomechanically assessed and the difference of the antirotating ability stiffness of the ankle between simple posterior malleolus fixation and simple syndesmotic fixation was analyzed statistically.ResultsThe tibial insertion of posterior inferior tibiofibular ligament and inferior transverse tibiofibular ligament complex was relatively broad, and its width decreased as the distance from the joint line increased. Biomechanical analysis showed that: the threshold of posterior area of posterior malleolus fracture was 1/4S; posterior malleolus fixation provided better rotational stability than syndesmotic fixation (P < 0.01).ConclusionThe surgical indications for posterior malleolus fracture should consider simultaneously the restoration of the axial and rotational stability of the ankle. Simple posterior malleolus fracture fixation is recommended when the syndesmosis is unstable and the area ratio of posterior tibial insertion of posterior malleolus fracture is greater than or equal to 1/4. Syndesmotic fixation is proposed to restore and maintain the rotational stability of the ankle when the syndesmosis is unstable and the area ratio is less than 1/4. Regardless of the area ratio, the surgical indication only depends on the impact of the posterior malleolus fracture on the axial stability of tibiotalar joint, the involved articular surface area, and the displacement degree of posterior malleolus fragment, when the syndesmosis is stable.

Role of Syndesmotic Ligaments in Lateral Ankle Instability

Category: Ankle; Sports; Trauma Introduction/Purpose: Despite the success of surgical intervention, about 13-35% of patients continue to have ankle symptoms after surgery for lateral ankle instability which could be due to presence of undetected and thus untreated injury to other ankle ligaments.Concomitant lateral ankle ligament and syndesmotic ligamentous injuries are common. It is unknown, however, whether syndesmotic ligaments directly contribute to lateral ankle stability. Therefore, the aim of this study was to fluoroscopically evaluate whether the syndesmotic ligaments contributes to lateral ankle stability. Methods: Twenty-four above-knee cadaveric specimens were divided into three groups that underwent fluoroscopic evaluation for lateral ankle stability. In all the groups, the assessment was first done with all syndesmotic and ankle ligaments intact. Thereafter, Group 1 underwent sequential transection of the lateral ankle ligaments: (1) anterior talofibular ligament (ATFL), (2)calcaneofibular ligament(CFL), and (3)posterior talofibular ligament (PTFL). Group 2 underwent sequential transection of the lateral ankle ligaments followed by the syndesmotic ligaments: (1) ATFL, (2) CFL, (3) PTFL, (4) anterior inferior tibiofibular ligament(AITFL), (5)interosseous ligament(IOL), and (6)posterior inferior tibiofibular ligament (PITFL). Group 3 alternating and sequential transection of the syndesmotic and lateral ankle ligaments: (1) AITFL, (2) ATFL, (3) CFL, (4) IOL, (5) PTFL, and (6) PITFL. In all scenarios, three loading conditions were considered:(1)An anterior drawer test at 50N and 80N of direct force, (2) talar tilt under 1.7Nm torque, and (2) lateral clear space (LCS) under 1.7Nm torque. Wilcoxon rank-sum test was used to compare the findings of each ligamentous transection state to the intact state. Results: The lateral ankle remained stable after transection of all syndesmotic ligaments (AITFL, IOL, PITFL). However, after additional transection of the ATFL, the lateral ankle became unstable in varus and anterior drawer testing conditions (p-values ranging from 0.036-0.012). Lateral ankle instability was also observed after transection of the ATFL and AITFL (p-values ranging from 0.036-0.012). Subsequent transection of the CFL worsened the lateral ankle instability. Conclusion: Our findings suggest that syndesmotic injuries can destabilize otherwise stable lateral ankle sprains. When treating lateral ankle instability, clinician should maintain a lower threshold for operative intervention for syndesmotic stabilization if there are any residual symptoms over the AITFL.

Biomechanical Study of Syndesmotic Stability in AITFL and PITFL Injury Models

Category: Basic Sciences/Biologics; Trauma Introduction/Purpose: Severe ankle syndesmotic injuries can cause not only anterior inferior tibiofibular ligament (AITFL) injury but also posterior inferior tibiofibular ligament (PITFL) injury. However, the biomechanical stability and the best surgical treatment method for PITFL injuries are unknown. This study aimed to evaluate the stability of AITFL and PITFL injury models and the treatment models with suture-button (SB) fixation, AITFL augmentation with suture-tape (aST), and PITFL augmentation with suture-tape (pST). We hypothesized that PITFL injury causes posterior instability of syndesmosis and that this can be stabilized with pST fixation Methods: This study was approved by our institution's ethics review board. Ten normal fresh-frozen cadaver legs (4 males and 6 females) that were donated to our university's department of anatomy were used. The specimens were tested with the application of traction and rotational forces for dorsiflexion and external and internal rotation of the ankle joint. The fibular rotational angle related to the tibia (FRA), anterior tibiofibular diastasis (aTFD), and posterior tibiofibular diastasis (pTFD) were measured using the magnetic tracking system. Intact, injured (AITFL, PITFL and IOM resection), SB fixation, SB + aST fixation, and SB + aST + pST fixation models were made and loaded with forces. One-way ANOVA was used to evaluate the relationship between the models. Post-hoc analysis of the differences between the models was performed using Dunnett's test. A p value of 0.05 was chosen as the level of significance. Results: In the injured model, both FRA and TFD were significantly increased compared with those of the intact model in all directions. In the SB fixation model, only FRA with an external rotation force was significantly increased compared with that of the intact model. In the SB+aST model, both FRA and aTFD were not significantly different from those in the intact model. Conclusion: The results of this study showed that there was external and internal rotational instability in the AITFL and PITFL injury models, while there was stability in the SB + aST model. SB fixation alone did not reduce FRA with an external rotation force and there was no significantly different FRA with an internal rotation force. With SB fixation alone, anterior instability was found to be greater than posterior stability, while aST fixation was associated with anterior stability. In this study, the change in syndesmosis stability after pST fixation was found to be restrictive.

Evaluation of Distal Tibiofibular Interosseous Ligament Angle and Its Relevance in Syndesmosis Fixation

Category: Ankle; Basic Sciences/Biologics Introduction/Purpose: The interosseous ligament (IOL) of the ankle, together with the anterior and posterior inferior tibiofibular ligament (ATFL and PITFL), are important structures which stabilizes the inferior tibiofibular joint. Besides securing the fibula tightly to tibia, these ligaments prevent excessive lateral fibular displacement and external talar rotation. Thus, any injury to either bone or ligaments at this level will result in instability and abnormal joint motion. Our study aims to evaluate the anatomical angle of the ankle interosseous ligament on magnetic resonance imaging (MRI) studies to better understand the biomechanical forces that act within the distal tibiofibular joint, relevance of assimilating the anatomical angle and its relevance in syndesmosis fixations. Methods: MRIs of ankles were chosen anonymously from the global PACS system database between the months September to October 2020. A total of 34 patients' MRIs were identified. Patients who sustained bone or soft tissue injury at the level of ankle syndesmosis were excluded to avoid any ambiguity in altered position of the IOL due to trauma. The angle of interosseous ligament from the tibial plafond was measured on the coronal plane. The axial plane was used as a reference to ensure correct position of measurement. This was done in collaboration with radiologists to ensure that IOL is correctly identified, prior to start of the study. The angle was measured separately by two different investigators and the average angle was obtained for each MRI. Data was tabulated and statistical analysis was done. Results: All of the 20 ankles identified during the study period were included in the analysis. There were 10 male and 10 female patients. Nine were left ankles and 11 were right ankles. The median age was 54 years (range 14 - 83). The mean IOL angle was 65.66 degrees. The standard error of difference between the 2 investigators was 0.567 and the two-tailed P value was 0.4980. By conventional criteria, this difference is considered to be not statistically significant. Conclusion: The ligament angle formed against tibial plafond bears theoretical relevance. We propose further cadaveric studies to confirm IOL anatomical ligament angle and carrying out implant failure stress test in a lab between the implant inserted parallel to the normal angle of IOL (65 degrees) vs 90 degrees. We also propose that such studies may show that all implants to stabilize the syndesmosis may be more effective if we try to reproduce nature by replicating as close to the IOL's anatomical angle rather than using a long held dogma of fixing syndesmosis to neutralize the forces as nature intended.

Arthroscopic Evaluation of Subtle Syndesmotic Instability: Are We Pulling Correctly in the Coronal Plane?

Category: Ankle; Sports; Trauma Introduction/Purpose: While the lateral hook test (LHT) has been widely used to arthroscopically evaluate syndesmotic instability in the coronal plane, it is unclear whether the angulation of the applied force has any impact on the degree of instability. The aim of this study was to determine if changing the direction of the force applied while performing the LHT impacts the amount of coronal diastasis observed in purely ligamentous syndesmotic injuries. Methods: In 10 cadaveric specimens, arthroscopic evaluation of the distal tibiofibular joint in the coronal plane was performed. Anterior and posterior third coronal plane diastasis were assessed in the intact state and repeated after sequential transection of the, 1) anterior inferior tibiofibular ligament (AITFL), 2) the interosseous ligament (IOL) and the 3) posterior inferior tibiofibular ligament (PITFL). In all scenarios, the lateral hook test (LHT) was performed under 100N of laterally directed force. Additionally, LHT was also performed under 1) anterior inclination of 15 degrees and 2) posterior inclination of 15 degrees in the intact and AITFL+IOL deficient state. One-way ANOVA with post hoc Tukey HSD was used to test for significant differences in coronal plane measurements between each stage of ligament transection, and to determine the effect of different directions of force application on coronal space measurements in the intact and AITFL+IOL transected states. Results: Compared to the intact state, the distal tibiofibular joint remained stable after transection of AITFL under laterally directed force with no angulation. However, after additional transection of the IOL, the syndesmosis became unstable in the coronal plane (p = 0.029 and 0.025 for anterior and posterior third diastasis, respectively). This instability worsened further with subsequent transection of the PITFL (p = &lt;0.001). Moreover, there was no statistical difference in anterior and posterior-third coronal diastasis in both intact and AITFL+IOL deficient states under neutral, anterior, and posteriorly directed force(p-values ranging from 0.816-0.993 and 0.396-0.80,respectively). However, in AITFL+IOL transected state, posteriorly directed forces resulted in greater diastasis than neutral or anteriorly directed forces. Conclusion: Angulation of the applied force ranging from 15 degrees anteriorly to 15 degrees posteriorly during intraoperative LHT has no effect on coronal plane measurements in patients with subtle syndesmotic instability. On the other hand, posteriorly directed forces result in more sizable diastasis, potentially increasing their sensitivity. When arthroscopically evaluating subtle syndesmotic instability, clinicians should assess coronal diastasis with the hook angled 15 degrees posteriorly.

Portable Ultrasound Equals Arthroscopy for Assessment of Syndesmotic Instability

Category: Ankle; Arthroscopy Introduction/Purpose: Syndesmotic instability, when subtle, can be challenging to diagnose-and often requires visualization of the syndesmosis during applied stress. Portable ultrasonography is increasingly used to evaluate ankle instability at the point of care. This study aims to evaluate 1) whether portable ultrasonography (P-US) can diagnose syndesmotic instability in the sagittal plane, and 2) how P-US measurements compare to arthroscopic evaluation. Methods: Eight fresh, above-knee cadaveric specimen were used. The syndesmosis was evaluated with P-US and arthroscopy in the intact state, and thereafter with progressive sectioning of, 1) anterior-inferior tibiofibular ligament (AITFL), 2) interosseous ligament (IOL), and 3) posterior-inferior tibiofibular ligament (PITFL). Sagittal plane translation was simulated with 100N of anterior to posterior (A to P) and posterior to anterior (P to A) directed force using a bone hook. Separately, a 50N manual force was applied to the fibular tip and measured with P-US to simulate a fibular 'shuck test' performed in the clinical setting. Results: When all three syndesmotic ligaments were transected, there was a significant increase in fibular motion in the sagittal plane when evaluated using portable ultrasonography with application of 50N of manual pressure and when applying a 100N hook test when measuring total sagittal plane motion (p=&lt;0.001 and p=0.009). Arthroscopy demonstrated significant increased motion with a 100N hook test when measuring total sagittal plane motion (p&lt;0.001). Conclusion: P-US performed similarly to arthroscopy when diagnosing syndesmotic instability in the sagittal plane. P-US also offers several advantages over arthroscopy, including availability, non-invasiveness, low cost, and affording contralateral comparison. The promise of this technique suggests it should be further explored as a potential future standard for the diagnostic assessment of occult syndesmotic instability in the sagittal plane.

Portable Dynamic Ultrasonography is a Useful Tool for the Evaluation of Suspected Syndesmotic Instability

Category: Ankle Introduction/Purpose: Portable ultrasonography (P-US) is increasingly used to diagnose syndesmotic instability. The aim of this study was to evaluate syndesmotic instability by measuring the distal tibiofibular clear space (TFCS) in a cadaveric model using P- US with progressive stages of syndesmotic ligamentous transection. Methods: Ten fresh lower leg cadaveric specimens amputated above the proximal tibiofibular joint were used. Using P-US, the TFCS was evaluated in the intact stage and after progressive sectioning of the 1) anterior-inferior tibiofibular ligament (AITFL), 2) interosseous ligament (IOL), and 3) posterior-inferior tibiofibular ligament (PITFL). The TFCS was measured in both the unstressed (0 Nm) state and with 4.5 Nm, 6.0 Nm, 7.5 Nm, and 9.0 Nm of external rotation stress at each stage of ligamentous transection stage using both P-US and fluoroscopy. Results: When assessed with P-US, partial syndesmotic injury encompassing the AITFL and IOL resulted in significant TFCS widening at 4.5 Nm of external rotation torque when compared to intact state with a TFCS-opening of 2.6 +- 2 mm, p = 0.01. In contrast, no significant differences in TFCS were detected using fluoroscopy. Only a moderate correlation was found between P- US and fluoroscopy. Conclusion: P-US is much more sensitive than fluoroscopy in diagnosing syndesmotic instability during external rotation stress examination. Extrapolated to the clinical setting, 4.5 Nm of force can be used when comparing to the stressed, uninjured side, and may be better tolerated by patients than higher torque values. When using P-US, a TFCS-opening of 2.6 mm is likely to correlate with syndesmotic instability. While absolute threshold values may vary between individuals, the ready availability of the contralateral, uninjured side overcomes this constraint.

Posterior Ankle Impingement: It is Not All About the Os Trigonum

Category: Arthroscopy; Ankle; Hindfoot; Sports Introduction/Purpose: Posterior ankle and hindfoot arthroscopy (PAHA) is a well described procedure used for treating posterior ankle impingement syndrome (PAIS). Os trigonum and trigonal process (Stieda) are common etiologies and diagnosis is typically made by radiographs, CT, or MRI. However, these static tests may not detect associated soft tissue and other bony pathologies, which are often dynamic. Physical examination and Ultrasound (US) are dynamic. US can be limited by depth. Traditional open treatment may not allow visualization and appreciation for these associated pathologies. PAHA is dynamic providing at least 8X magnification with full visualization of the posterior ankle and subtalar joints. The primary aim of this study is to report the incidence of associated pathologies seen with os trigonum or Stieda impingement when treated with PAHA. Methods: A retrospective case series of patients who underwent PAHA for PAIS due to trigonal impingement between January 2011 and September 2016 were reviewed. Surgeries were performed by three fellowship-trained orthopedic foot and ankle surgeons in 251 patients. Exclusions were those having concomitant open posterior procedures, other indications for PAHA (e.g., OCL, subtalar fusion) or other PAIS etiology (e.g., soft tissue impingement). After exclusions, 112 patients were studied, with a mean age of 30.5 (12-70) and a BMI of 29.93 (SD 9.23). Demographic data was collected along with pre and postoperative diagnosis, arthroscopic findings, type of impingement, location of the disorder, associated procedures, and anatomical etiologies. Trigonal impingements were allocated as os trigonal or Stieda and subgrouped as isolated, with other impingement lesions +/- FHL disorders. Differences between groups with isolated trigonal impingement and those with associated pathologies were determined by distribution comparison. Wilcoxon test was used to compare subgroups. Results: From the 112 cases, 75 were os trigonum and 37 Stieda. Isolated trigonal disorders accounted for 16% of the total PAIS patients (n=18). Those cases having pathologies other than trigonal impingement had a mode of 3 (1-5) additional pathologies with 41% of the treated cases having 3 or more adjunctive findings needing treatment during posterior arthroscopy. Flexor hallucis longus (FHL) disorders were found in 68% of cases, subtalar problems in 44%, and transverse posterior inferior tibiofibular ligament (tPITFL) in 19%. A 58% proportion of associated pathologies was observed when FHL disorders were not considered. Significant differences were noted when comparing os trigonum and Stieda subgroups (FHL: 29% to 18%, p&lt;0.001; FHL and others: 34% to 59%, p=0.046; other findings: 14% to 16%, p=0.025). Conclusion: Our study described a high prevalence of associated pathological structures involved with a trigonal disorder leading to PAI in a large cohort. Trigonal bone (os trigonum or Stieda) was found to cause impingement in isolation in a small proportion of cases (16%). Even when the FHL is removed from the equation, 58% of the total patients still presented other associated impingement pathologies. This should alert surgeons when considering removing trigonal impingement especially with an open approach. Open approaches may limit the visualization and assessment of associated posterior ankle and subtalar pathoanatomy, thus possibly overlooking concomitant causes of PAIS.

Arthroscopic assessment of syndesmotic instability: Are we pulling correctly in the coronal plane?

BackgroundWhile the lateral hook test (LHT) has been widely used to arthroscopically evaluate syndesmotic instability in the coronal plane, it is unclear whether the angulation of the applied force has any impact on the degree of instability. We aimed to determine if changing the direction of the force applied while performing the LHT impacts the amount of coronal diastasis observed in subtle syndesmotic injuries. MethodsIn 10 cadaveric specimens, arthroscopic evaluation of the syndesmotic joint was performed by measuring anterior and posterior-third coronal plane diastasis in the intact state, and repeated after sequential transection of the 1) anterior inferior tibiofibular ligament (AITFL), 2) interosseous ligament (IOL), and 3) posterior inferior tibiofibular ligament (PITFL). In all scenarios, LHT was performed under 100 N of laterally directed force. Additionally, LHT was also performed under: 1) anterior inclination of 15 degrees and 2) posterior inclination of 15 degrees in intact and AITFL+IOL deficient state. ResultsCompared to the intact state, the syndesmosis became unstable after AITFL +IOL transection under laterally directed force with no angulation (p = 0.029 and 0.025 for anterior and posterior-third diastasis, respectively), which worsened with subsequent PITFL transection (p = <0.001). Moreover, there was no statistical difference in anterior and posterior-third coronal diastasis in both intact and AITFL+IOL deficient states under neutral, anterior, and posteriorly directed force (p-values ranging from 0.816 to 0.993 and 0.396–0.80, respectively). However, in AITFL+IOL transected state, posteriorly directed forces resulted in greater diastasis than neutral or anteriorly directed forces. ConclusionsAngulation of the applied force ranging from 15 degrees anteriorly to 15 degrees posteriorly during intraoperative LHT has no effect on coronal plane measurements in patients with subtle syndesmotic instability. On the other hand, posteriorly directed forces result in more sizable diastasis, potentially increasing their sensitivity. Clinical relevanceWhen arthroscopically evaluating subtle syndesmotic instability, clinicians should assess coronal diastasis with the hook angled 15 degrees posteriorly.

A Systematic Review of the Routine Removal of Syndesmosis Screws in Traumatic Ankle Fractures

The ankle syndesmosis is a critical structure, conferring a great degree of stability to the ankle mortise comprising part of a complex framework of ligaments responsible for 90% of the resistance to lateral displacement of the fibula [1]. The components of the syndesmosis are the Anterior-Inferior Tibiofibular Ligament (AITFL), Posterior- Inferior Tibiofibular Ligament (PITFL), Transverse Tibiofibular Ligament (TTFL) and Interosseous Ligament (IOL). With approximately one in seven ankle fractures associated with a syndesmotic injury it is a common pattern [2]. The injury itself is most often found intra-operatively after stable fixation of malleolar fractures, indicated by persistent instability. This instability is often dealt with through the use of a bridging syndesmotic screw which restores the ankle mortise, confers stability but leaves the original syndesmotic injury relatively untouched.

Biomechanics comparison between endobutton fixation and syndesmotic screw fixation for syndesmotic injury ankle fracture; a finite element analysis and cadaveric validation study

IntroductionVarious syndesmotic fixation methods in ankle injury are recommended; however, a lack of biomechanical information persists regarding the stiffness of the fixation methods. The current study thus aimed to assess biomechanical cadaveric validation and perform a finite element analysis of syndesmotic fixation comparing endobutton vs. screw after syndesmotic injury with an ankle fracture. MethodFive pairs of ankles of fresh cadavers were used for the validity test for Anterior Inferior Tibiofibular Ligament (AITFL), Posterior Inferior Tibiofibular Ligament (PITFL), and Interosseous ligament biomechanics properties. Four finite element models (FEM) were created: an intact model, a fracture model with/without syndesmotic injury, an endobutton fixation model, and a syndesmotic screw fixation model. Each FEM was tested vis-à-vis external rotation force, anteroposterior translation force, and compression force until model failure. The primary outcomes were stiffness and force until failure. ResultThe respective anteroposterior translation force for the stiffness of the intact model, the screw fixation model, and the endobutton fixation was 8.14, 9.15, and 8.17 N/mm. The respective external rotation force for the stiffness of intact, screw fixation, and endobutton model was 0.927,0.949, and 0.940 Nm/degree. The respective stress under compression force in the intact, screw fixation, and endobutton model was 39.94,25.59, and 37.30 MPa. ConclusionBoth screw and endobutton fixation models provided more translation, compression, and rotation stability than normal syndesmosis, but the screw model provided greater translation and compression force stability than the endobutton model. There was no difference in rotational stability between the two models. We thus recommend the same rehabilitation protocol for both fixation methods; however, vigorous translation and compression should be avoided when using endobutton fixation.

Comparison of Treatment Methods for Syndesmotic Injuries With Posterior Tibiofibular Ligament Ruptures: A Cadaveric Biomechanical Study.

Background:Studies on ankle syndesmosis have focused on anterior inferior tibiofibular ligament (AITFL) and interosseous membrane injuries; however, the characteristics of posterior inferior tibiofibular ligament (PITFL) ruptures remain unclear.Purpose/Hypothesis:This study evaluated the biomechanical characteristics of syndesmotic instability caused by PITFL injury and compared various treatment methods. We hypothesized that PITFL injury would lead to syndesmotic internal rotational instability and that the stability would be restored with suture tape (ST) PITFL augmentation.Study Design:Controlled laboratory study.Methods:Ten uninjured fresh-frozen cadaveric leg specimens were tested via forces applied to the external and internal rotation of the ankle joint. The fibular rotational angle (FRA) related to the tibia, anterior tibiofibular diastasis (aTFD), and posterior tibiofibular diastasis (pTFD) were measured using a magnetic tracking system. Six models were created: (1) intact, (2) AITFL injury; (3) AITFL + PITFL injury; (4) suture button (SB) fixation; (5) SB + anterior ST (aST) fixation; and (6) SB + aST + posterior ST fixation. The FRA, aTFD, and pTFD were statistically compared between the intact ankle and each injury or fixation model.Results:In the intact state, the changes in FRA and aTFD were 1.09° and 0.33 mm when external rotation force was applied and were 0.57° and 0.41 mm when internal rotation force was applied. In the AITFL injury model, the changes in FRA and aTFD were 2.38° and 1.51 mm when external rotation force was applied, which were significantly greater versus intact (P = .032 and .008, respectively). In the AITFL + PITFL injury model, the changes in FRA and pTFD were 2.12° and 1.02 mm when internal rotation force was applied, which were significantly greater versus intact (P = .007 and .003, respectively). In the SB fixation model, the change in FRA was 2.98° when external rotation force was applied, which was significantly higher compared with intact (P < .001). There were no significant differences between the SB + aST fixation model and the intact state on any measurement.Conclusion:PITFL injury significantly increased syndesmotic instability when internal rotation force was applied. SB + aST fixation was effective in restoring syndesmotic stability.Clinical Relevance:These results suggest that SB + aST fixation is sufficient for treating severe syndesmotic injury with PITFL rupture.

Fluoroscopic Evaluation of the Role of Syndesmotic Injury in Lateral Ankle Instability in a Cadaver Model.

There is a high prevalence of concomitant lateral ankle ligament injuries and syndesmotic ligamentous injuries. However, it is unclear whether syndesmotic ligaments directly contribute toward the stability of the lateral ankle. Therefore, the aim of this study was to fluoroscopically evaluate the role of the syndesmotic ligaments in stabilizing the lateral ankle. Twenty-four cadaveric specimens were divided into 3 groups and fluoroscopically evaluated for lateral ankle stability with all syndesmotic and ankle ligaments intact and then following serial differential ligamentous transection. Group 1: (1) anterior talofibular ligament (ATFL), (2) calcaneofibular ligament (CFL), and (3) posterior talofibular ligament (PTFL). Group 2: (1) anterior inferior tibiofibular ligament (AITFL), (2) interosseous ligament (IOL), (3) posterior inferior tibiofibular ligament (PITFL), (4) ATFL, (5) CFL, and (6) PTFL. Group 3: (1) AITFL, (2) ATFL, (3) CFL, (4) IOL, (5) PTFL, and (6) PITFL. At each transection state, 3 loading conditions were used: (1) anterior drawer test performed using 50 and 80 N of direct force, (2) talar tilt <1.7 Nm torque, and (2) lateral clear space (LCS) <1.7 Nm torque. These measurements were in turn compared with those of the stressed intact ligamentous state. Wilcoxon rank-sum test was used to compare the findings of each ligamentous transection state to the intact state. A P value <.05 was considered statistically significant. The lateral ankle remained stable after transection of all syndesmotic ligaments (AITFL, IOL, PITFL). However, after additional transection of the ATFL, the lateral ankle became unstable in varus and anterior drawer testing conditions (P values ranging from .036 to .012). Lateral ankle instability was also observed after transection of the ATFL and AITFL in varus and anterior drawer testing conditions (P values ranging from .036 to .012). Subsequent transection of the CFL and PTFL worsened the lateral ankle instability. Our findings suggest that isolated syndesmosis disruption does not result in lateral ankle instability. However, the lateral ankle became unstable when the syndesmosis was injured along with ATFL disruption. When combined with ATFL release, disruption of the syndesmosis appeared to destabilize the lateral ankle.