Range of Normal and Abnormal Syndesmotic Measurements Using Weightbearing CT

Automation improves the efficiency of weightbearing CT scan 3D volumetric assessments of the syndesmosis

BACKGROUND

Weight-bearing CT (WBCT) 3D volumetric measurement has shown promising accuracy for the diagnosis of syndesmotic instability. However, these measurements are rather complex and time-consuming, rendering them a clinically unfavorable option. We hypothesized that automatized measurements would be more accurate and time-efficient than manual ones.

METHODS

Thirty cases of intraoperatively confirmed syndesmotic instability along with thirty individuals with no injuries to the ankle joint were recruited as cases and controls, retrospectively. Two observers conducted the manual volumetric measurements two times, at a one-week interval. An automated algorithm for 3D WBCT measurements was developed to conduct the measurements on the axial images. The time spent on each method was recorded. Mann-Whitney U test was used to compare the values between human raters and computers. Inter- and intra-class reliability were calculated.

RESULTS

The intra-class correlation coefficient was found to be "excellent" for the automated measurements (0.97) and "good" for the observers (0.75). Similarly, the Cronbach's alpha was shown to be higher for the computer (0.88) than the observers (0.60 and 0.62). The mean time spent on the measurements was different between human raters and the computer-assisted method (p < 0.001).

CONCLUSION

Automated volumetric assessment of syndesmosis seems to be a faster and more reliable option than the manual one. We suggest future larger-scale prospective studies conducted under actual clinical circumstances for more definitive conclusions.

LEVEL OF EVIDENCE

Retrospective case-control study - Level 3.

The role of computed tomography with external rotation and dorsiflexion in decision making for acute isolated non-displaced posterior malleolar fractures Bartoníček and Rammelt type II: a prospective study

PURPOSE

Our objective was to evaluate the syndesmotic and fracture instability using conventional ankle computed tomography (CT) with stress maneuvers.

METHODS

A consecutive sample of 123 individuals with an ankle sprain was assessed for eligibility. In total, 33 patients met the inclusion criteria. All patients underwent a magnetic resonance imaging (MRI) and CT scan with stress maneuvers (CTSM). The patterns of ligament tears f were classified using West Point grades I, IIA, IIB, III. Mann-Whitney test was used to test the differences in the numerical variables between injured and uninjured syndesmoses. The Spearman correlation tested the strength of the association between the tibial joint surface involved in posterior malleolus fracture and syndesmotic instability.

RESULTS

In MRI, two patterns of syndesmotic ligament injury predominated. A completely torn anterior inferior tibiofibular (AITFL) and interosseous tibiofibular ligaments (ITFL) and a completely torn AITFL were combined with a partially torn ITFL. In the neutral phase CTSM and during the stress phase the median difference of the narrowest tibiofibular distance between injured and uninjured syndesmoses was 0.2 mm (P = 0.057) and 2.3 mm (P < 0.0001), respectively. There was no association between the percentage of involvement of the posterior tibial joint surface in the posterior malleolar fracture and syndesmotic instability as measured with CTSM.

CONCLUSION

The conventional computed tomography with external rotation and dorsiflexion represents a reproducible and accurate diagnostic option for detecting syndesmosis instability and fracture instability in acute isolated non-displaced posterior malleolar fractures Bartoníček and Rammelt type II.

LEVEL OF EVIDENCE

Prospective study among consecutive patients (Diagnosis); Level of evidence, 2.

Bilateral External Torque CT Reliably Detects Syndesmotic Lesions in an Experimental Cadaveric Study

BACKGROUND

If tibiofibular syndesmotic injury is undetected, chronic instability may lead to persistent pain and osteoarthritis. So far, no reliable diagnostic method has been available. The primary objectives of this study were to determine whether defined lesions of the syndesmosis can be correlated with specific tibiofibular joint displacements caused by external rotational torque and to compare the performance of bilateral external torque computed tomography (BET-CT) and arthroscopy. Secondary objectives included an evaluation of the reliability of CT measurements and the suitability of the healthy contralateral ankle as a reference.

METHODS

Seven pairs of healthy, cadaveric lower legs were tested and assigned to 2 groups: (1) supination-external rotation (SER) and (2) pronation-external rotation (PER). In the intact state and after each surgical step, an ankle arthroscopy and 3 CT scans were performed. During the scans, the specimens were placed in an external torque device with 2.5, 5.0, and 7.5 Nm of torque applied.

RESULTS

The arthroscopic and CT parameters showed significant correlations in all pairwise comparisons. The receiver operating characteristic (ROC) curve analyses yielded the best prediction of syndesmotic instability with the anterior tibiofibular distance on CT, with a sensitivity of 84.1% and a specificity of 95.2% (area under the curve [AUC], 94.8%; 95% confidence interval [CI], 0.916 to 0.979; p < 0.0001) and with the middle tibiofibular distance on arthroscopy, with a sensitivity of 76.2% and specificity of 92.3% (AUC, 91.2%; 95% CI, 0.837 to 0.987; p < 0.0001). Higher torque amounts increased the rate of true-positive results.

CONCLUSIONS

BET-CT reliably detects experimental syndesmotic rotational instability, compared with the healthy side, with greater sensitivity and similar specificity compared with the arthroscopic lateral hook test. Translation of these experimental findings to clinical practice remains to be established.

LEVEL OF EVIDENCE

Diagnostic Level III . See Instructions for Authors for a complete description of levels of evidence.

Normal Values for Distal Tibiofibular Syndesmotic Space With and Without Subject-Driven External Rotation Stress

BACKGROUND

The diagnosis and treatment of distal tibiofibular syndesmosis (DTFS) injury can be challenging, especially in cases of subtle instability that may be masked on 2-dimensional conventional radiographs. Weightbearing computed tomography (WBCT) has recently emerged as a useful diagnostic tool allowing direct assessment of distal tibiofibular area widening. The purpose of the current study was to examine and report normal threshold values for DTFS area measurements in a cohort of healthy volunteers, assessing the ankles in natural weightbearing position and under subject-driven external rotation stress.

METHODS

In this prospective study, we enrolled 25 healthy volunteers without a history of DTFS injury or high ankle sprain, previous foot and ankle surgery, or current ankle pain. Subjects with any prior ankle injuries were excluded. Study participants underwent bilateral standing nonstress and external rotation stress WBCT scans. The DTFS area (mm2) was semiautomatically quantified on axial-plane WBCT images 1 cm proximal to the apex of the talar dome using validated software. Syndesmosis area values were compared between "unstressed" and "stressed" ankles, as well as left and right ankles. Statistical analysis was performed using independent t tests/Wilcoxon analysis with statistical significance defined as P <.05.

RESULTS

The study cohort consisted of 50 ankles in 25 patients (12 males, 48%) with a mean age of 28.7 ± 9.3 years. In the unstressed ankle, the mean pooled DTFS area was determined to be 103.8 + 20.8 mm2. The mean syndesmosis area of unstressed left ankles (104.2 + 19.5 mm2) was similar to unstressed right ankles (109.2 + 17.2 mm2) in the cohort (P = .117). With external rotation stress, the DTFS area of left ankles (mean difference -0.304 mm2, CI -12.1 to 11.5; P = .082), right ankles (mean difference -5.5 mm2, CI 16.7-5.7; P = .132), and all ankles (mean difference -2.9 mm2, CI -10.8 to 5.1; P = .324) remained similar.

CONCLUSION

This study presents normal values and range for DTFS area calculation. In uninjured ankles with expected intact ligaments, subject-driven external rotation stress did not result in significant widening of the DTFS space as imaged on with WBCT.

LEVEL OF EVIDENCE

Level II, cross-sectional study.

The use of deep learning enables high diagnostic accuracy in detecting syndesmotic instability on weight-bearing CT scanning

PURPOSE

Delayed diagnosis of syndesmosis instability can lead to significant morbidity and accelerated arthritic change in the ankle joint. Weight-bearing computed tomography (WBCT) has shown promising potential for early and reliable detection of isolated syndesmotic instability using 3D volumetric measurements. While these measurements have been reported to be highly accurate, they are also experience-dependent, time-consuming, and need a particular 3D measurement software tool that leads the clinicians to still show more interest in the conventional diagnostic methods for syndesmotic instability. The purpose of this study was to increase accuracy, accelerate analysis time, and reduce interobserver bias by automating 3D volume assessment of syndesmosis anatomy using WBCT scans.

METHODS

A retrospective study was conducted using previously collected WBCT scans of patients with unilateral syndesmotic instability. One-hundred and forty-four bilateral ankle WBCT scans were evaluated (48 unstable, 96 control). We developed three deep learning models for analyzing WBCT scans to recognize syndesmosis instability. These three models included two state-of-the-art models (Model 1-3D Convolutional Neural Network [CNN], and Model 2-CNN with long short-term memory [LSTM]), and a new model (Model 3-differential CNN LSTM) that we introduced in this study.

RESULTS

Model 1 failed to analyze the WBCT scans (F1 score = 0). Model 2 only misclassified two cases (F1 score = 0.80). Model 3 outperformed Model 2 and achieved a nearly perfect performance, misclassifying only one case (F1 score = 0.91) in the control group as unstable while being faster than Model 2.

CONCLUSIONS

In this study, a deep learning model for 3D WBCT syndesmosis assessment was developed that achieved very high accuracy and accelerated analytics. This deep learning model shows promise for use by clinicians to improve diagnostic accuracy, reduce measurement bias, and save both time and expenditure for the healthcare system.

LEVEL OF EVIDENCE

II.

Combining radiographic and CT measurements to rival MRI for the diagnosis of acute isolated syndesmotic injury

BACKGROUND

Acute isolated syndesmotic injuries (AISIs) have a high potential to be misdiagnosed or underdiagnosed at initial presentation to the hospital. Although magnetic resonance imaging (MRI) is the gold standard in noninvasive diagnostics, it is not always available immediately and is much more expensive than other imaging modalities. This study identifies improvements in conventional radiography and computed tomography (CT) to diagnose AISI and aims to reduce the number of MRI scans needed to verify the diagnosis.

METHODS

A retrospective case match control study was conducted by searching our trauma database between 2008 and 2022. A study group of patients with AISI (n = 64) and a control group of patients without AISI (n = 76) were formed to generate an equal number of images from both groups (62 radiographs and 22 CT scans). A total of 16 parameters that quantify the distal tibiofibular relation in injured and uninjured ankles were analyzed. For statistical analysis, a two-sided t-test was applied to calculate significant differences (p < 0.05). In a further step, a receiver operating characteristic curve (ROC) was used to determine cut-off values for the most significant parameters.

RESULTS

The most significant measurement (p < 0.001) on axial CT scans was the syndesmotic area (SA). The ROC curve revealed an area under the curve (AUC) of 0.94 (95% CI 0.86-1.0) and a cut-off value of 71.68 mm2 that shows a sensitivity and specificity of 95.5% and 81.8%, respectively.

CONCLUSION

This study suggests that radiographic imaging could represent an equally accurate alternative to MRI. These methods might generate the correct diagnosis faster due to their availability and inexpensiveness. By applying our new cut-off values in a clinical setting, the number of underdiagnosed and untreated unstable syndesmotic injuries could be reduced.

LEVEL OF EVIDENCE

III, retrospective comparative study.

Diagnosis of subtle syndesmotic instability using conventional CT-imaging and axial force in different foot positions

BACKGROUND

Currently, there is no available method that can objectively and reliably detect subtle instability of the distal tibiofibular joint. The purpose of this study is to diagnose, using computerized axial tomography and an adjustable simulated loading device, subtle instability of the tibiofibular syndesmosis.

METHODS

Fifteen healthy individuals and 15 patients with clinical suspicion of subtle instability of the tibiofibular syndesmosis (total 60 ankles) were studied using an adjustable simulated loading device (ASLD). This device allows to perform bilateral ankle CT scans in two forced foot and ankle positions (30° of plantar flexion, 15° of inversion, 20° of internal rotation and 15° of dorsal flexion, 15° of eversion, 30° of external rotation). Axial load was applied simultaneously in a controlled manner (70% body weight). Measurements on the axial image of computed tomography were: syndesmotic area (SA), fibular rotation (FR), position of the fibula in the sagittal plane (FPS), depth of the incisura (ID), anterior direct difference (ADD), middle direct difference (MDD) and posterior direct difference (PDD).

RESULTS

Statistically significant differences were observed in the variable syndesmotic area between healthy (mean=-0.14, SD=4.33) and diseased (mean=16.82, SD=12.3)(p < 0.001). No statistically significant differences were found in the variables ADD, MDD, PDD, ID, FPS and FR.

CONCLUSIONS

Measurement of syndesmotic area employing axial force and forced foot positions using the ASLD may be useful for the diagnosis of subtle tibiofibular syndesmosis instability.

The Emerging Role of Automation, Measurement Standardization, and Artificial Intelligence in Foot and Ankle Imaging: An Update

In the past few years, advances in clinical imaging in the realm of foot and ankle have been consequential and game changing. Improvements in the hardware aspects, together with the development of computer-assisted interpretation and intervention tools, have led to a noticeable improvement in the quality of health care for foot and ankle patients. Focusing on the mainstay imaging tools, including radiographs, computed tomography scans, and ultrasound, in this review study, the authors explored the literature for reports on the new achievements in improving the quality, accuracy, accessibility, and affordability of clinical imaging in foot and ankle.

Implementing automated 3D measurements to quantify reference values and side-to-side differences in the ankle syndesmosis

Detection of syndesmotic ankle instability remains challenging in clinical practice due to the limitations of two-dimensional (2D) measurements. The transition to automated three-dimensional (3D) measurement techniques is on the verge of a breakthrough but normative and side-to-side comparative data are missing. Therefore, our study aim was two-fold: (1) to establish 3D anatomical reference values of the ankle syndesmosis based on automated measurements and (2) to determine to what extent the ankle syndesmosis is symmetric across all 3D measurements. Patients without syndesmotic pathology with a non-weight-bearing CT scan (NWBCT; N = 38; Age = 51.6 ± 17.43 years) and weight-bearing CT scan (WBCT; N = 43; Age = 48.9 ± 14.3 years) were retrospectively included. After training and validation of a neural network to automate the segmentation of 3D ankle models, an iterative closest point registration was performed to superimpose the left on the right ankle. Subsequently, 3D measurements were manually and automatically computed using a custom-made algorithm and side-to-side comparison of these landmarks allowed one to investigate symmetry. Intra-observer analysis showed excellent agreements for all manual measurements (ICC range 0.85-0.99) and good (i.e. < 2.7° for the angles and < 0.5 mm for the distances) accuracy was found between the automated and manual measurements. A mean Dice coefficient of 0.99 was found for the automated segmentation framework. The established mean, standard deviation and range were provided for each 3D measurement. From these data, reference values were derived to differ physiological from pathological syndesmotic alignment. Furthermore, side-to-side symmetry was revealed when comparing left to right measurements (P > 0.05). In clinical practice, our novel algorithm could surmount the current limitations of manual 2D measurements and distinguish patients with a syndesmotic ankle lesion from normal variance.

High-Ankle Sprain and Syndesmotic Instability: How Far Have We Come with Diagnosis and Treatment?

Probably one of the most controversial subjects in the orthopedic field is the distal tibiofibular articulation. Even though its most primary knowledge can be a matter of enormous debate, it is in the diagnosis and treatment most of the disagreements reign. Distinguishing between injury and instability remains challenging as well as an optimal clinical decision regarding surgical intervention. The last years presented technology and that was able to bring body to an already well-developed scientifical rationale. In this review article, we aim to demonstrate the current data behind syndesmotic instability in the ligament scenario, whereas using few fracture concepts.

Can Weight-Bearing Computed Tomography Be a Game-Changer in the Assessment of Ankle Sprain and Ankle Instability?

Ankle sprain and chronic lateral ankle instability are complex conditions and challenging to treat. Cone beam weight-bearing computed tomography is an innovative imaging modality that has gained popularity, with a body of literature reporting reduced radiation exposure and operating time, and shortened examination time and a decreased time interval between injury and diagnosis. In this article, we make clearer the advantages of this technology and encourage researchers to investigate the area, and clinicians to use it as a primary mode of investigation. We also present clinical cases provided by the authors to illustrate those possibilities using advanced imaging tools.

Diagnostic Accuracy of Conventional Ankle CT Scan With External Rotation and Dorsiflexion in Patients With Acute Isolated Syndesmotic Instability

BACKGROUND

Syndesmotic injury in an athletic population is associated with a prolonged ankle disability after an ankle sprain and often requires a longer recovery than a lateral collateral ligament injury. Although several imaging tests are available, diagnosing syndesmotic instability remains challenging.

PURPOSE

To determine the diagnostic accuracy of conventional ankle computed tomography (CT) scans with the joint in external rotation and dorsiflexion and compare it with that of conventional ankle CT scans in a neutral position.

STUDY DESIGN

Cohort study (Diagnosis); Level of evidence, 2.

METHODS

Between September 2018 and April 2021, this prospective study consecutively included adults visiting the foot and ankle outpatient clinic with a positive orthopaedic examination for acute syndesmotic injury. Participants underwent 3 CT scan tests. First, ankles were scanned in a neutral position. Second, ankles were scanned with 45° of external rotation, dorsiflexion, and extended knees. Third, ankles were scanned with 45° of external rotation, dorsiflexion, and flexed knees. Three measurements, comprising rotation (measurement a), lateral translation (measurement c), and anteroposterior translation (measurement f) of the fibula concerning the tibia, were used to diagnose syndesmotic instability in the 3 CT scans. Magnetic resonance imaging was used as a reference standard. The area under the curve (AUC) was used to compare the diagnostic accuracy, and Youden's J index was calculated to determine the ideal cutoff point.

RESULTS

Images obtained in 68 participants (mean age, 36.5 years; range, 18-69 years) were analyzed, comprising 36 syndesmotic injuries and 32 lateral collateral ligament injuries. The best diagnostic accuracy occurred with the rotational measurement a, in which the second and third CT scans with stress maneuvers presented greater AUCs (0.97 and 0.99) than did the first CT scan in a neutral position (0.62). The ideal cutoff point for the stress maneuvers was 1.0 mm in the rotational measurement a and reached a sensitivity and specificity of 83% and 97% for the second CT scan with extended knees and 86% and 100% for the third CT scan with flexed knees, respectively. The ideal cutoff point for the first CT scan with a neutral position was 0.7 mm in the rotational measurement a, with a sensitivity of 25% and specificity of 97%.

CONCLUSION

Conventional ankle CT with stress maneuvers has excellent performance for diagnosing subtle syndesmotic rotational instability, as it shows a greater AUC and enhanced sensitivity at the ideal cutoff point compared with ankle CT in the neutral position.

Syndesmosis Malposition Assessed on Weight-Bearing CT Is Common After Operative Fixation of Intra-articular Distal Tibia Plafond Fracture

OBJECTIVES

To evaluate reliability of measurement techniques for syndesmosis position after operative fixation of distal tibia plafond fracture on weight-bearing computed tomography (WBCT), identify risk factors for syndesmosis malposition, and determine if syndesmosis malposition is associated with higher pain and lower physical function.

DESIGN

Prospective cohort study.

SETTING

Three Level 1 trauma centers.

PARTICIPANTS

Twenty-six subjects who underwent open reduction and internal fixation of distal tibia plafond fractures with bilateral ankle WBCT 1 year or greater after injury were included in the study.

INTERVENTION

Operative fixation of distal tibia plafond fracture.

MAIN OUTCOME MEASUREMENT

Fibula position in the tibia incisura, injury characteristics, and patient-reported outcomes were the main outcome measurements.

RESULTS

Interrater reliability for syndesmosis position measurements were excellent for the Phisitkul technique on both injured and healthy ankles (intraclass correlation coefficients [ICCs]: 0.93-0.98). The Nault technique demonstrated moderate-to-excellent interrater reliability (ICCs: 0.67-0.98), apart from the angle of rotation measurement (ICCs: 0.18-0.67). Sixteen of 26 subjects (62%) had syndesmosis malposition defined as >2 mm difference comparing the tibial-fibular relationship in injured and uninjured ankles using these 2 methods. Patients with syndesmosis malposition reported lower Foot and Ankle Ability Measure: Activities of Daily Living scores; other recorded patient-reported outcomes were not significantly different.

CONCLUSIONS

Measurement techniques for syndesmosis position on WBCT were reliable after operative fixation of distal tibia plafond fracture. Syndesmosis malposition is common after these injuries and predicted impaired physical function.

LEVEL OF EVIDENCE

Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Statistical shape model-based tibiofibular assessment of syndesmotic ankle lesions using weight-bearing CT

Forced external rotation is hypothesized as the key mechanism of syndesmotic ankle injuries, inducing a three-dimensional deviation from the normal distal tibiofibular joint (DTFJ) alignment. However, current diagnostic imaging modalities are impeded by a two-dimensional assessment, without considering ligamentous stabilizers. Therefore, our aim is threefold: (1) to construct an articulated statistical shape model of the normal DTFJ with the inclusion of ligamentous morphometry, (2) to investigate the effect of weight-bearing on the DTFJ alignment, and (3) to detect differences in predicted syndesmotic ligament length of patients with syndesmotic lesions with respect to normative data. Training data comprised non-weight-bearing CT scans from asymptomatic controls (N = 76), weight-bearing CT scans from patients with syndesmotic ankle injury (N = 13), and their weight-bearing healthy contralateral side (N = 13). Path and length of the syndesmotic ligaments were predicted using a discrete element model, wrapped around bony contours. Statistical shape model evaluation was based on accuracy, generalization, and compactness. The predicted ligament length in patients with syndesmotic lesions was compared with healthy controls. With respect to the first aim, our presented skeletal shape model described the training data with an accuracy of 0.23 ± 0.028 mm. Mean prediction accuracy of ligament insertions was 0.53 ± 0.12 mm. In accordance with the second aim, our results showed an increased tibiofibular diastasis in healthy ankles after weight-bearing. Concerning our third aim, a statistically significant difference in anterior syndesmotic ligament length was found between ankles with syndesmotic lesions and healthy controls (p = 0.017). There was a significant correlation between the presence of syndesmotic injury and the positional alignment between the distal tibia and fibula (r = 0.873, p < 0,001). Clinical Significance: Statistical shape modeling combined with patient-specific ligament wrapping techniques can facilitate the diagnostic workup of syndesmosic ankle lesions under weight-bearing conditions. In doing so, an increased anterior tibiofibular distance was detected, corresponding to an "anterior open-book injury" of the ankle syndesmosis as a result of anterior inferior tibiofibular ligament elongation/rupture.

Weight-bearing cone-beam CT: the need for standardised acquisition protocols and measurements to fulfill high expectations-a review of the literature

Weight bearing CT (WBCT) of the lower extremity is gaining momentum in evaluation of the foot/ankle and knee. A growing number of international studies use WBCT, which is promising for improving our understanding of anatomy and biomechanics during natural loading of the lower extremity. However, we believe there is risk of excessive enthusiasm for WBCT leading to premature application of the technique, before sufficiently robust protocols are in place e.g. standardised limb positioning and imaging planes, choice of anatomical landmarks and image slices used for individual measurements. Lack of standardisation could limit benefits from introducing WBCT in research and clinical practice because useful imaging information could become obscured. Measurements of bones and joints on WBCT are influenced by joint positioning and magnitude of loading, factors that need to be considered within a 3-D coordinate system. A proportion of WBCT studies examine inter- and intraobserver reproducibility for different radiological measurements in the knee or foot with reproducibility generally reported to be high. However, investigations of test-retest reproducibility are still lacking. Thus, the current ability to evaluate, e.g. the effects of surgery or structural disease progression, is questionable. This paper presents an overview of the relevant literature on WBCT in the lower extremity with an emphasis on factors that may affect measurement reproducibility in the foot/ankle and knee. We discuss the caveats of performing WBCT without consensus on imaging procedures and measurements.

Can Weightbearing Cone-beam CT Reliably Differentiate Between Stable and Unstable Syndesmotic Ankle Injuries? A Systematic Review and Meta-analysis

BACKGROUND

Ankle injuries are common presentations to the emergency department and may lead to syndesmotic instability. These have a high socioeconomic burden due to prolonged rehabilitation, chronic pain, and posttraumatic arthritis. Early diagnosis is essential to minimize these complications, and the assessment of instability in the clinical setting is often limited by pain and clinician experience. Cross-sectional imaging of the distal syndesmosis accurately evaluates the syndesmosis through abnormal bony relationships, which in the presence of instability, worsens during physiological loading. Cone-beam CT (CBCT) has gained popularity in the diagnosis of these injuries because it enables syndesmotic assessment under weightbearing conditions, it mitigates the high radiation dose, and it is time-efficient.

QUESTIONS/PURPOSES

The purposes of this systematic review were: (1) to establish normal values for weightbearing CBCT of the syndesmosis in uninjured ankles and ascertain interobserver reliability and (2) to identify the impact of weightbearing on the syndesmosis in patients with occult ankle injuries and assess the effect of patient demographics on these metrics.

METHODS

This systematic review was reported in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines and registered in PROSPERO (ID CRD42021248623). MEDLINE, PubMed, Embase, and Emcare databases were searched for studies assessing for syndesmotic instability, of which 307 studies were screened and 11 studies with 559 ankles in 408 uninjured patients and 151 patients with syndesmotic instability were included. All patients 18 years of age or older presenting with unilateral ankle injuries who underwent weightbearing CBCT for the diagnosis of an occult fracture or syndesmotic instability compared with the uninjured contralateral side were included. A control group of uninjured ankles was identified during weightbearing CBCT performed for other indications such as forefoot or midfoot injuries. Methodological assessment of the studies was performed using the Risk of Bias In Non-randomized Studies (ROBINS-1) tool and most included studies had a low risk of bias. Thus, a random-effects restricted maximum likelihood ratio model was used.

RESULTS

In the uninjured ankle, the mean area of the tibiofibular syndesmosis was 112.5 ± 7.1 mm 2 , which increased to 157.5 ± 9.6 mm 2 after injury when compared with uninjured ankles with a standardized mean difference of 29.5 (95% confidence interval 19.5 to 39.5; p < 0.01), and an excellent interobserver agreement (κ = 1.0 [95% CI 0.9 to 1.0]). However, syndesmosis volume decreased with age (β = -0.76; p = 0.04), and therefore, has a negative association with increasing age.

CONCLUSION

Our study has shown that the syndesmotic area is the most reliable parameter in the assessment of syndesmotic injuries because it increases in the presence of instability during weightbearing status. It is a composite measurement that could potentially allow clinicians to use weightbearing CBCT as an adjunct when there is a clinical suspicion of syndesmotic instability. Thus, weightbearing CBCT has the potential of being diagnostic of syndesmotic instability and should be evaluated against current radiological modalities to evaluate its accuracy.

LEVEL OF EVIDENCE

Level IV, prognostic study.

Portable dynamic ultrasonography is a useful tool for the evaluation of suspected syndesmotic instability: a cadaveric study

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 under external rotation stress.

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, 6.0, 7.5, and 9.0 Nm of external rotation stress using a bone hook placed on the first metatarsal bone 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 a useful tool in diagnosing syndesmotic instability during external rotation stress examination. TFCS-opening increased as additional ligaments of the syndesmosis were transected, and application of 4.5 Nm torque was sufficient to detect a difference of 2.6 mm after the IOL cut.

Analysis of the uninjured tibiofibular syndesmosis using conventional CT-imaging and axial force in different foot positions

BACKGROUND

Syndesmosis measurments and indices have been controversial and showed interindividual variability. The purpose of this study was to analyze, by conventional axial computed tomography images and a simulated load device, the uninjured tibiofibular syndesmosis under axial force and forced foot positions.

METHODS

A total of 15 healthy patients (30 ankles) were studied using adjustable simulated load device (ASLD). This device allowed to perform bilateral ankle CT scans in two forced foot and ankle positions (30° of plantar flexion, 15° of inversion, 20° of internal rotation and 15° of dorsal flexion, 15° of eversion, 30° of external rotation). Axial load was applied simultaneously in a controlled manner (70% body weight). Measurements on the axial image of computed tomography were: syndesmotic area (SA), fibular rotation (FR), position of the fibula in the sagittal plane (FPS), depth of the incisura (ID) and direct anterior difference (ADD), direct middle difference (MDD) and direct posterior difference (PDD).

RESULTS

In patients without injury to the tibiofibular syndesmosis, the application of axial load and forced foot and ankle positions showed statistically significant differences on the distal tibiofibular measurements between the stressed and the relaxed position, it also showed interindividual variability : SA (median = 4.12 [IQR = 2.42, 6.63]) (p < 0.001), ADD (0.67 [0.14, 0.67]) (p < 0.001), MDD(0.45, [0.05, 0.9]) (p < 0.001), PDD (0.73 [-0.05, 0.73]) (p < 0.002). However, it did not detect statistically significant differences when the tibiofibular differences between the stressed and the relaxed position in one ankle were compared with the contralateral side: SA (-0.14, SD = 4.33 [95% CI = -2.53, 2.26]), ADD (-0.42, 1.08 [-1.02, 0.18]), MDD (0.29, 0.54 [-0.01, 0.59]), PDD (-0.1, 1.42 [-0.89, 0.68]). Interobserver reliability showed an Intraclass correlation coefficient of 0.990 [95% CI = 0.972, 0.997].

CONCLUSIONS

Wide interindividual variability was observed in all syndesmotic measurements, but no statistically significant differences were found when comparing one ankle to the contralateral side. Measuring syndesmosis alignment parameters, may only be of value, if those are compared to the contralateral ankle.

Effect of weightbearing and foot positioning on 3D distal tibiofibular joint parameters

The aim of this study was to investigate the effect of different loading scenarios and foot positions on the configuration of the distal tibiofibular joint (DTFJ). Fourteen paired human cadaveric lower legs were mounted in a loading frame. Computed tomography scans were obtained in unloaded state (75 N) and single-leg loaded stand (700 N) of each specimen in five foot positions: neutral, 15° external rotation, 15° internal rotation, 20° dorsiflexion, and 20° plantarflexion. An automated three-dimensional measurement protocol was used to assess clear space (diastasis), translational angle (rotation), and vertical offset (fibular shortening) in each foot position and loading condition. Foot positioning had a significant effect on DTFJ configuration. Largest effects were related to clear space increase by 0.46 mm (SD 0.21 mm) in loaded dorsal flexion and translation angle of 2.36° (SD 1.03°) in loaded external rotation, both versus loaded neutral position. Loading had no effect on clear space and vertical offset in any position. Translation angle was significantly influenced under loading by - 0.81° (SD 0.69°) in internal rotation only. Foot positioning noticeably influences the measurements when evaluating DTFJ configuration. Loading seems to have no relevant effect on native ankles in neutral position.

Tibial torsion correlates with talar morphology

BACKGROUND

There is limited literature on axial rotation of the ankle or variations in anatomy of the talus. We aim to evaluate the rotational profile of the distal tibia and its relationship to talus morphology, radiographic foot-type, and tibiotalar tilt in arthritic ankles.

METHODS

Preoperative imaging was reviewed in 173 consecutive patients with ankle arthritis. CT measurements were used to calculate tibial torsion and the talar neck-body angle (TNBA). Tibiotalar tilt and foot-type were measured on weightbearing plain radiographs.

RESULTS

Measurements indicated mean external tibial torsion of 29.2±9.1˚ and TNBA of 35.2±7.5˚ medial. Tibiotalar tilt ranged from 48˚ varus to 23.5˚ valgus. A moderate association between increasing external tibial torsion and decreasing TNBA was found (ρ=-0.576, p<.0001). Weak relationships were found between external tibial torsion and varus tibiotalar tilt (ρ=-0.239, p=.014) and plantarflexion of the talo-first metatarsal angle (ρ=-0.218, p<.025).

CONCLUSION

We observed a statistically significant correlation between tibial torsion and morphology of the talus, tibiotalar tilt, and first ray plantarflexion. This previously unreported association may provide information regarding the development of foot and ankle deformity and pathology.

LEVEL OF EVIDENCE

Level III.

Syndesmotic instability can be assessed by measuring the distance between the tibia and the fibula using an ultrasound without stress: a cadaver study

Background

Ultrasound examinations for syndesmosis injury might be useful for the quantitative evaluation of syndesmotic instability. The purpose of this study was to evaluate the efficacy of ultrasound assessment by measuring the tibiofibular distance of syndesmosis injuries in various ligament-injured models and stress load conditions.

Methods

Five normal ankles from Thiel-embalmed cadavers were used. Ultrasound assessment was performed by placing a probe in parallel with the ligament running just above the anterior inferior tibiofibular ligament (AITFL). The distance between the anterior border of the tibia and the fibula was measured in the intact condition. Next, Bassett’s ligament was cut arthroscopically to reduce damage to soft tissues as much as possible and measurement was performed in the same way. After that, the AITFL, interosseous membrane (IOM), deltoid ligament, and posterior inferior tibiofibular ligament (PITFL) were macroscopically cut and measured in that order. Ankle positions were without stress (natural plantar flexion without applying stress to the ankle joint), dorsiflexion stress, inversion stress, and external rotation stress. All stress to the ankle joint was carried out manually to the maximum extent.

Results

As with the without-stress condition, significant increases in tibiofibular distances after AITFL dissection were seen compared with the intact state under all stress conditions (intact: 4.9 ± 1.0 mm without stress, 5.6 ± 1.2 mm with dorsiflexion, 5.9 ± 1.0 mm with inversion, and 6.7 ± 1.3 mm with external rotation; AITFL dissection: 6.7 ± 1.5 mm without stress, 7.3 ± 1.2 mm with dorsiflexion, 7.5 ± 1.4 mm with inversion, and 8.7 ± 1.6 mm with external rotation). AITFL dissection with external rotation stress significantly increased the tibiofibular distance compared to without stress.

Conclusion

Changes in tibiofibular distance with the severity of syndesmosis injury were measured by ultrasound using cadavers. No significant change was seen with Bassett’s ligament injury, but tibiofibular distance increased significantly with injuries of equal to or greater severity than AITFL injury. Results were similar not only for external rotation stress, but also for dorsiflexion stress and inversion stress, and even in unloaded states, significant tibiofibular widening was confirmed with injuries of equal to or greater severity than AITFL injury.

The Assessment of Ankle Osteoarthritis with Weight-Bearing Computed Tomography

The standard for diagnostic radiographic imaging in foot and ankle surgery was until 2012 radiographs with full weight-bearing without any useful alternative. Weight-bearing cone-beam computed tomography (WBCT) was introduced 2012 for foot and ankle use as a new technology that allows 3D imaging with full weight-bearing which should be not influenced by projection and/or foot orientation. The assessment of ankle osteoarthritis with WBCT including the description of healthy status, effect of alignment and7or (in)stability is extensively illustrated in this review article.

Volume measurements on weightbearing computed tomography can detect subtle syndesmotic instability

While weightbearing computed tomography (WBCT) allows three-dimensional (3D) visualization of the distal syndesmosis, image interpretation has largely relied on one-dimensional (1D) distance and, more recently, two-dimensional (2D) area measurements. This study aimed to (1) determine the sensitivity and specificity of 2D area and 3D volume WBCT measurements towards detecting subtle syndesmotic instability, (2) evaluate whether the patterns of changes in the 3D shape of the syndesmosis can be attributed to the type of ligament injury. A total of 24 patients with unilateral subtle syndesmotic instability and 24 individuals with uninjured ankles (controls) with bilateral ankle WBCT were assessed retrospectively. First, 2D areas at 0, 1, 3, 5, and 10 cm, and 3D volumes at 1, 3, 5, and 10 cm above the tibial plafond were measured bilaterally. Secondly, the 3D model of the distal tibiofibular space was created based on WBCT in a subset of 8 out of 24 patients in whom the type of ligament injury was recognized via magnetic resonance imaging. The 3D model of the injured side was superimposed on the uninjured contralateral side to visualize the pattern of changes in different planes. Volume measurement up to 5 cm above the tibial plafond showed the lowest p-value (<0.001 vs. other methods), higher sensitivity (95.8%, 95% confidence interval [CI]: 87.8-100), and specificity (83.3%, 95% CI: 68.4-98.2) for detection of syndesmotic instability. No specific pattern of changes in the 3D shape could be attributed to a type of ligament rupture. We suggest 3D volume measurements, best measured up to 5 cm proximal to the plafond, as a promising means of diagnosing syndesmotic instability, particularly for subtle cases that are hard to detect. Clinical significance: The ability to compare the ankle joints bilaterally in a 3D manner under physiologic weight provided by weightbearing CT has led to a more accurate diagnostic method. Using volumetric measurement up to 5 cm above the tibial plafond showed higher sensitivity and specificity for recognizing an unstable syndesmosis, especially in subtle cases. However, our preliminary investigations showed that the pattern of 3D alterations in the distal tibiofibular joint space based on WBCT images does not indicate the type of syndesmotic ligamentous injury. Our results can also help image viewing programs to improve their measurement tools to facilitate 3D measurement for the syndesmosis as well as other conditions that may benefit from 3D evaluation of the clinical images.

Utility of WBCT to Diagnose Syndesmotic Instability in Patients With Weber B Lateral Malleolar Fractures

BACKGROUND

Diagnosing syndesmotic instability accompanying Weber B ankle fractures can be challenging. This study aimed to evaluate the ability of weight-bearing computed tomography (WBCT) to diagnose syndesmotic instability using one-dimensional, two-dimensional, and three-dimensional measurements among patients with unilateral Weber B lateral malleolar fractures with symmetric medial clear space (MCS) on initial radiographs and yet demonstrated operatively confirmed syndesmotic instability.

METHODS

The treatment group included 23 patients with unilateral surgically confirmed syndesmotic instability accompanying Weber B ankle fractures who underwent preoperative bilateral foot and ankle WBCT. The control group included 18 unilateral Weber B ankle fracture patients without syndesmotic instability who underwent bilateral WBCT. Measurements on WBCT images included the following: (1) syndesmotic area, (2) anterior, middle, and posterior distal tibiofibular distance, (3) fibular rotation, (4) distance from fibular tip to plafond, (5) fibular fracture displacement, and (6) MCS distance. In addition, the following volumetric measurements were calculated: (1) syndesmotic joint volume from the tibial plafond extending to 3 and 5 cm proximally, (2) MCS volume, and (3) lateral clear space volume. Area under the receiver operating characteristic curve analysis and Delong test were used, and optimal cutoff values to distinguish between stable and unstable syndesmosis were determined using Youden J statistic.

RESULTS

Among patients with unilateral syndesmotic instability and Weber B ankle fractures, all WBCT measurements were significantly greater than uninjured side, except MCS distance, syndesmotic area, and anterior and posterior tibiofibular distances (P values <0.001 to 0.004). Moreover, syndesmosis volume spanning from the tibial plafond to 5 cm proximally had the largest area under the curve of 0.96 (sensitivity = 90%; specificity = 95%), followed by syndesmosis volume up to 3 cm proximally (area under the curve = 0.91; sensitivity = 90%; specificity = 90%). Except for MCS volume and distal fibular tip to tibial plafond distance, the control group showed no side-to-side difference in any parameter.

CONCLUSION

Syndesmotic joint volume measurements seem to be best suited to diagnose syndesmotic instability among patients with Weber B ankle fractures, compared with other two-dimensional and three-dimensional WBCT measurements.

LEVEL OF EVIDENCE

Level III, comparative diagnostic study.

Diagnosis and Treatment of Syndesmotic Unstable Injuries: Where We Are Now and Where We Are Headed

Up to 10% of ankle sprains are considered "high ankle" sprains with associated syndesmotic injury. Initial diagnosis of syndesmotic injury is based on physical examination, but further evaluation of the distal tibiofibular joint in the sagittal, coronal, and rotational planes is necessary to determine instability. Imaging modalities including weight-bearing CT and ultrasonography allow a physiologic and dynamic assessment of the syndesmosis. These modalities in turn provide the clinician useful information in two and three dimensions to identify and consequently treat syndesmotic instability, especially when subtle. Because there is notable variability in the shape of the incisura between individuals, contralateral comparison with the uninjured ankle as an optimal internal control is advised. Once syndesmotic instability is identified, surgical treatment is recommended. Several fixation methods have been described, but the foremost aspect is to achieve an anatomic reduction. Identifying any associated injuries and characteristics of the syndesmotic instability will lead to the appropriate treatment that restores the anatomy and stability of the distal tibiofibular joint.

Assessment of Hindfoot Alignment Comparing Weightbearing Radiography to Weightbearing Computed Tomography

BACKGROUND

Hindfoot alignment view (HAV) radiographs are widely utilized for 2-dimensional (2D) radiographic assessment of hindfoot alignment; however, the development of weightbearing computed tomography (WBCT) may provide more accurate methods of quantifying 3-dimensional (3D) hindfoot alignment. The aim of this study was to compare the 2D calcaneal moment arm measurements on HAV radiographs with WBCT.

METHODS

This retrospective cohort study included 375 consecutive patients with both HAV radiographs and WBCT imaging. Measurement of the 2D hindfoot alignment moment arm was compared between both imaging modalities. The potential confounding influence of valgus/varus/neutral alignment, presence of hardware, and motion artifact were further analyzed.

RESULTS

The intraclass correlation coefficients (ICCs) of interobserver and intraobserver reliability for measurements with both imaging modalities were excellent. Both modalities were highly correlated (Spearman coefficient, 0.930; P < .001). HAV radiographs exhibited a mean calcaneal moment arm difference of 3.9 mm in the varus direction compared with WBCT (95% CI, -4.9 to 12.8). The difference of hindfoot alignment between both modalities was comparable in subgroups with neutral/valgus/varus alignment, presence of hardware, and motion artifact.

CONCLUSION

Both HAV radiographs and WBCT are highly reliable and highly correlated imaging methods for assessing hindfoot alignment. Measurements were not influenced by severe malalignment, the presence of hardware, or motion artifact on WBCT. On average, HAV radiographs overestimated 3.9 mm of varus alignment as compared with WBCT.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

Four-Dimensional CT Analysis of Normal Syndesmotic Motion

BACKGROUND

The syndesmosis ligament complex stabilizes the distal tibiofibular joint while allowing for small amounts of physiologic motion. When injured, malreduction of the syndesmosis is the most important factor that contributes to inferior functional outcomes. Syndesmotic reduction is a dynamic measure, which is not adequately captured by conventional computed tomography (CT). Four-dimensional CT (4DCT) can image joints as they move through range of motion (ROM). The aim of this study was to employ 4DCT to determine in vivo syndesmotic motion with ankle ROM in uninjured ankles.

METHODS

Uninjured ankles were analyzed in patients who had contralateral syndesmotic injuries, as well as a cohort of healthy volunteers with bilateral uninjured ankles. Bilateral ankle 4DCT scans were performed as participants moved their ankles between maximal dorsiflexion and plantarflexion. Multiple measures of syndesmotic width, as well as sagittal translation and fibular rotation, were automatically extracted from 4DCT using a custom program to determine the change in syndesmotic position with ankle ROM.

RESULTS

Fifty-eight ankles were analyzed. Measures of syndesmotic width decreased by 0.7 to 1.1 mm as the ankle moved from dorsiflexion to plantarflexion (P < .001 for each measure). The fibula externally rotated by 1.2 degrees with ankle ROM (P < .001), but there was no significant motion in the sagittal plane (P = .43). No participants with bilateral uninjured ankles had a side-to-side difference in syndesmotic width of 2 mm or greater.

CONCLUSION

4DCT allows accurate, in vivo syndesmotic measurements, which change with ankle ROM, confirming prior work that was limited to biomechanical studies. Side-to-side syndesmotic measurements are consistent within subjects, validating the method of templating syndesmotic reduction off the contralateral ankle, in a consistent ankle position, to achieve anatomic reduction of syndesmotic injury.

LEVEL OF EVIDENCE

Level II, prospective cohort study.

Using area and volume measurement via weightbearing CT to detect Lisfranc instability

Weightbearing CT (WBCT) allows evaluation of the Lisfranc joint under physiologic load. We compared the diagnostic sensitivities of one-dimensional (1D) distance, two-dimensional (2D) area, and three-dimensional (3D) volumetric measurement of the injured Lisfranc joint complex (tarsometatarsal, intertarsal, and intermetatarsal) on WBCT among patients with surgically-confirmed Lisfranc instability. The experimental group comprised of 14 patients having unilateral Lisfranc instability requiring operative fixation who underwent preoperative bilateral foot and ankle WBCT. The control group included 36 patients without foot injury who underwent similar imaging. Measurements performed on WBCT images included: (1) Lisfranc joint (medial cuneiform-base of second metatarsal) area, (2) C1-C2 intercuneiform area, (3) C1-M2 distance, (4) C1-C2 distance, (5) M1-M2 distance, (6) first tarsometatarsal (TMT1) angular alignment, (7) second tarsometatarsal (TMT2) angular alignment, (8) TMT1 dorsal step off distance, and (9) TMT2 dorsal step-off distance. In addition, the volume of the Lisfranc joint in the coronal and axial plane were calculated. Among patients with unilateral Lisfranc instability, all WBCT measurements were increased on the injured side as compared to the contralateral uninjured side (p values:  <.001-.008). Volumetric measurements in the coronal and axial plane had a higher sensitivity (92.3%; 91.6%, respectively) and specificity (97.7%; 96.5%, respectively) than 2D and 1D Lisfranc joint measurements, suggesting them to be the most accurate in diagnosing Lisfranc instability. The control group showed no difference in any of the measurements between the two sides. WBCT scan can effectively differentiate between stable and unstable Lisfranc injuries. Lisfranc joint volume measurements demonstrate high sensitivity and specificity, suggesting that this new assessment has high clinical implications for diagnosing subtle Lisfranc instability.

The Syndesmosis, Part I: Anatomy, Injury Mechanism, Classification, and Diagnosis

Ankle fractures are common injuries to the lower extremity with approximately 20% sustaining a concomitant injury to the syndesmosis. Although the deltoid ligament is not formally included in the syndesmotic complex, it plays an important role in the mortise stability. Therefore, its integrity should be always evaluated when syndesmotic injury is suspected. Given the anatomic variability of the syndesmosis between individuals, bilateral ankle imaging is recommended, especially in cases of subtle instability. Diagnostic tests that allow dynamic assessment of the distal tibiofibular joint in the 3 planes are the most reliable in determining the presence of syndesmotic injury.

The Syndesmosis, Part II: Surgical Treatment Strategies

Syndesmotic injuries in the setting of ankle fracture are critically important to diagnosis and treat to restore an anatomic tibiotalar relationship. Physical examination and clinical suspicion remain critically important for diagnosis. Ultrasound examination and weight-bearing computed tomography scans are evolving to help diagnosis more subtle injuries. Although flexible syndesmotic fixation may decrease malreduction rates, the benefits over rigid fixation is the subject of ongoing study. Anatomic reduction remains critical regardless of fixation choice. Routine removal of rigid syndesmotic hardware does not seem to offer substantial clinical improvement in pain or range of motion; however, broken hardware may cause irritation.

APKASS Consensus Statement on Chronic Syndesmosis Injury, Part 1: Clinical Manifestation, Radiologic Examination, Diagnosis Criteria, Classification, and Nonoperative Treatment

Background

Clinical manifestation, radiologic examination, diagnostic criteria, classification, and nonoperative treatment strategies regarding chronic syndesmosis injury remain unclear.

Purpose

An international group of experts representing the fields of sports injuries in the foot and ankle area were invited to collaboratively advance toward consensus opinions based on the best available evidence regarding chronic syndesmosis injuries. All were members of the Asia-Pacific Knee, Arthroscopy and Sports Medicine Society (APKASS).

Study Design

Consensus statement.

Methods

From November to December 2020, a total of 111 international experts on sports medicine or ankle surgery participated in a 2-stage Delphi process that included an anonymous online survey and an online meeting. A total of 13 items with 38 statements were drafted by 13 core authors. Of these, 4 items with 15 clinical questions and statements were related to the clinical manifestation, radiologic examination, diagnostic criteria, classification, and nonoperative treatment strategies for chronic syndesmosis injury and are presented here. Each statement was individually presented and discussed, followed by a general vote. The strength of consensus was characterized as follows: consensus, 51% to 74%; strong consensus, 75% to 99%; unanimous, 100%.

Results

Of the 15 questions and statements, 5 reached unanimous support and 10 achieved strong consensus.

Conclusion

This APKASS consensus statement, developed by international experts in the field, will assist surgeons and physical therapists with diagnosis, classification, and nonoperative treatment strategies for chronic syndesmosis injury.

Distal Tibiofibular Syndesmotic Widening in Progressive Collapsing Foot Deformity

BACKGROUND

Lateral overload in progressive collapsing foot deformity (PCFD) takes place as hindfoot valgus, peritalar subluxation, and valgus instability of the ankle increase. Fibular strain due to chronic lateral impingement may lead to distraction forces over the distal tibiofibular syndesmosis (DTFS). This study aimed to assess and correlate the severity of the foot and ankle offset (FAO) as a marker of progressive PCFD with the amount of DTFS widening and to compare it to controls.

METHODS

In this case-control study, 62 symptomatic patients with PCFD and 29 controls who underwent standing weightbearing computed tomography (WBCT) examination were included. Two fellowship-trained blinded orthopedic foot and ankle surgeons performed FAO (%) and DTFS area measurements (mm²). DTFS was assessed semiautomatically on axial-plane WBCT images, 1 cm proximal to the apex of the tibial plafond. Values were compared between patients with PCFD and controls, and Spearman correlation between FAO and DTFS area measurements was assessed. P values of less than .05 were considered significant.

RESULTS

Patients with PCFD demonstrated significantly increased FAO and DTFS measurements in comparison to controls. A mean difference of 6.9% (P < .001) in FAO and 10.4 mm² (P = .026) in DTFS was observed. A significant but weak correlation was identified between the variables, with a Þ of 0.22 (P = .03). A partition predictive model demonstrated that DTFS area measurements were highest when FAO values were between 7% and 9.3%, with mean (SD) values of 92.7 (22.4) mm².

CONCLUSION

To our knowledge, this was the first study to assess syndesmotic widening in patients with PCFD. We found patients with PCFD to demonstrate increased DTFS area measurements compared to controls, with a mean difference of approximately 10 mm². A significantly weak positive correlation was found between FAO and DTFS area measurements, with the highest syndesmotic widening occurring when FAO values were between 7% and 9.3%. Our study findings suggest that chronic lateral impingement in patients with PCFD can result in a negative biomechanical impact on syndesmotic alignment, with increased DTFS stress and subsequent widening.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.

State of the Art in Treatment of Chronic Medial Ankle Instability

Chronic deltoid instability (CDI), or medial ankle instability, can happen following traumas of the foot and ankle, predominantly rotational injuries. CDI is frequently underdiagnosed or misdiagnosed. Long-term residual instability can lead to ankle posttraumatic arthritis. Adequate assessment of patients with suspected CDI is paramount. Conservative treatment can be tried for stable or mildly unstable cases, but surgical treatment is usually needed for the more severely unstable patients, or when conservative measures fail. Few reconstruction techniques have been proposed in the setting of posttraumatic CDI. This article describes our preferred technique for reconstruction of the deep components of the deltoid ligament.

Screw versus suture button in treatment of syndesmosis instability: Comparison using weightbearing CT scan

BACKGROUND

The superiority of screw or suture button fixation for syndesmotic instability remains debatable. Our aim is to compare radiographic outcomes of screw and suture button fixation of syndesmotic instability using weight bearing CT scan (WBCT).

METHODS

Twenty patients with fixation of unilateral syndesmotic instability were recruited and divided among two groups (screw = 10, suture button = 10). All patients had WBCT of both ankles ≥12 months postoperatively.

RESULTS

In suture button group, injured side measurements were significantly different from normal side for syndesmotic area (P = 0.003), fibular rotation (P = 0.004), anterior difference (P = 0.025) and direct anterior difference (P = 0.035). In screw group, syndesmotic area was the only significantly different measurement (P = 0.006).

CONCLUSION

While both screw and suture button didn't completely restore the syndesmotic area as compared to the contralateral uninjured ankle, external malrotation of the fibula was uniquely associated with suture button fixation.

LEVEL OF EVIDENCE

III Retrospective Cohort Study.

Weightbearing Computed Tomography for Assessment of Foot and Ankle Deformities: The Iowa Experience

BACKGROUND

Weightbearing computed tomography (WBCT) is a reliable and precise modality for the measurement and analysis of bone position in the foot and ankle, as well as associated deformities. WBCT to assess three dimensional relationships among bones allowed the development of new measurements, as the Foot and Ankle Offset (FAO), which has high inter and intra-rater reliability. This study reports the University of Iowa's experience utilizing WBCT for the care of foot and ankle patients by describing its utility across different orthopedic diseases in improving diagnostic assessment, aiding surgical planning, and expanding the use for objective clinical follow-up.

METHODS

The medical records of consecutive patients with various foot and ankle disorders that underwent WBCT examination as part of the standard of care at a single institution between November 2014 and August 2020 were retrospectively reviewed. Patient factors, including body mass index (BMI), sex, and patient comorbidities were collected. 3D coordinates for calculation of FAO were harvested using the Multiplanar Reconstruction (MPR) views were calculated from the obtained exams. Descriptive statistics were performed with Shapiro-Wilk test and the Anderson-Darling tests.

RESULTS

1175 feet and ankles (820 patients) had a WBCT performed over the studied 68 months. 53% of the subjects were male and 47% female. 588 of the acquisitions were from the right side (50.04%) and 587 from the left side (49.96%). Diabetes was present in 15.47% of, Rheumatic diagnoses in 4.52% and smoking habits in 44.10% of patients. Mean BMI of the sample was found to be 32.47 (32.03-32.90, 95% CI). The mean Foot and Ankle Offset (FAO) encountered in the study's population was 2.43 (2.05-2.82, 95% CI; min -30.8, max 37.65; median 2.39).

CONCLUSION

This study contains the largest cohort of WBCTs with accompanied FAO measurements to date, which can aid with establishing a new baseline FAO measurement for multiple pathological conditions. Acquiring WBCTs resulted in a variety of more specific diagnoses for patient with foot and ankle complaints. The ability to utilize WBCT for presurgical planning, the capability to provide a 3D reconstruction of patient anatomy, and its use for assessment of advanced relational foot and ankle measurements, such as FAO, demonstrate how WBCT may serve as a remarkable utility in clinical practice and has become a standard of care in our practice at the University of Iowa.Level of Evidence: IV.

Chronic Syndesmotic Injuries: Arthrodesis versus Reconstruction

"Chronic syndesmotic injury covers a broad range of symptoms and pathologies. Anterolateral ankle impingement without instability is treated by arthroscopic debridement. Subacute, unstable, syndesmotic injuries are treated by arthroscopic or open debridement followed by secondary stabilization using suture button device or permanent screw placement. Chronic syndesmotic instability is treated by a near-anatomic ligamentoplasty supplemented by screw fixation. In case of poor bone stock, failed ligament reconstruction, or comorbidities, tibiofibular fusion with bone grafting is preferred. Malleolar malunions and particularly anterior or posterior syndesmotic avulsions must be corrected in order to achieve a stable and congruent ankle mortise."

Diagnosing syndesmotic instability with dynamic ultrasound - establishing the natural variations in normal motion

BACKGROUND

Syndesmotic instability, when subtle, is challenging to diagnose and often requires visualization of the syndesmosis during applied stress. The primary aim was to assess normal distal tibiofibular motion in the sagittal plane using dynamic ultrasound under stress conditions. The secondary aim was to evaluate the reliability of dynamic stress ultrasonography.

METHODS

Twenty-eight participants without history of ankle injury were included. Sagittal fibular translation was generated by applying a manual force to the fibula from anterior to posterior and from posterior to anterior. Distance between the ultrasound probe and the fibula was taken at two predefined points: 1) no force applied and, 2) during maximum force application. Each participant was scanned twice by two independent examiners, and each scan was analysed by two independent examiners. Three participants were scanned a second time by the same examiner who analysed these films twice to assess for intraobserver agreement. Means of exam 1 versus exam 2 were compared using a mixed linear model. Agreement among observers was calculated using intraclass correlation coefficients (ICC) interpreted as 0.4, poor; 0.4 〈 ICC < 0.59, acceptable; 0.6 < ICC < 0.74, good; ICC 〉 0.74, excellent.

RESULTS

Fifty-six ankles were included in the study, including 16 (57%) males and 12 (42%) females. Average anterior to posterior fibular sagittal translation was 0.89 ± 0.6 mm and posterior to anterior fibular sagittal translation was 0.49 ± 1.1 mm. Anterior to posterior translation means of exam 1 versus exam 2 showed no significant differences, means of 0.81 mm [0.7-0.9] versus 0.77 mm [0.7-1.0], and posterior to anterior means [95% CI] of 0.42 mm [0.3-0.5] versus 0.44 mm [0.2-0.6] (p-values 0.416 and 0.758, respectively). Excellent Inter- and intraobserver agreement was found for all measurements taken.

CONCLUSION

Dynamic ultrasound allows one to effectively and readily evaluate sagittal translation of the distal tibiofibular joint. It is able to afford bilateral comparisons, which becomes critical as the amount of syndesmotic instability approaches greater degrees of subtlety.

Acute and Chronic Syndesmotic Instability: Role of Surgical Stabilization

Acute and chronic syndesmotic injuries significantly impact athletic function and activities of daily living. Patient history, examination, and judicious use of imaging modalities aid diagnosis. Surgical management should be used when frank diastasis, instability, and/or chronic pain and disability ensue. Screw and suture-button fixation remain the mainstay of treatment of acute injuries, but novel syndesmotic reconstruction techniques hold promise for treatment of acute and chronic injuries, especially for athletes. This article focuses on anatomy, mechanisms of injury, diagnosis, and surgical reduction and stabilization of acute and chronic syndesmotic instability. Fixation methods with a focus on considerations for athletes are discussed.

Utility of Volumetric Measurement via Weight-Bearing Computed Tomography Scan to Diagnose Syndesmotic Instability

BACKGROUND

Weight-bearing computed tomography (WBCT) allows evaluation of the distal syndesmosis under physiologic load. We hypothesized that WBCT volumetric measurement of the distal syndesmosis would be increased on the injured as compared to the contralateral uninjured side and that these 3-dimensional (3D) calculations would be a more sensitive determinant than 2-dimensional (2D) methodology among patients with syndesmotic instability.

METHODS

Twelve patients with unilateral syndesmotic instability requiring operative fixation who underwent preoperative bilateral foot and ankle WBCT were included in the study group. The control group consisted of 24 patients without ankle injury who underwent similar imaging. On WBCT scan, 2D measurements of the syndesmosis joint were first measured 1 cm above the joint line in the axial plane via syndesmotic area and distances between the anterior, middle, and posterior quadrants. Thereafter, comparative 3D volumetric measurements of the syndesmotic joint were also calculated: (1) from the tibial plafond extending until 3 cm proximally, (2) 5 cm proximally, and (3) 10 cm proximally.

RESULTS

In patients with unilateral syndesmotic instability, all 3 weight-bearing volumetric measurements were significantly larger on the injured side as compared to the contralateral, uninjured side (P < .001). In the control group, there was no difference between syndesmotic volumes at any level. Of these 3 anatomic reference points, the 3D measurement spanning from the tibial plafond to a level 5 cm proximally had the highest relative volumetric ratio between the injured and uninjured side, suggesting it is the most sensitive in distinguishing between stable and unstable syndesmotic injury (P < .001). Notably, this 3D volumetric measurement was also more sensitive than 2D measurements (P = .001).

CONCLUSION

3D volumetric measurement of the syndesmosis joint appears to be the most effective way to diagnose syndesmotic instability, compared with more traditional 2D syndesmosis measurement.

LEVEL OF EVIDENCE

Level III, retrospective comparative study.