A simplified, validated protocol for measuring fibular reduction on ankle CT

Syndesmotic Malreduction Prevention, Assessment, and Treatment

Syndesmotic instability or malreduction is an independent risk factor for an impaired patient-rated outcome. If a syndesmotic injury is suspected, a stepwise diagnostic approach including plane radiographs, MRI, and bilateral stress radiographs should be conducted to differentiate stable from latent unstable and frank diastasis cases. The basic requirement for any surgical treatment approach is a stable and anatomically reduced distal tibio-fibula joint. The best treatment approach for a 2-ligament injury (anterior inferior tibio-fibular ligament [AiTFL] + interosseous ligament [IOL]) seems to be the suture-button system, for a 3-ligament injury (AiTFL + IOL + posterior inferior tibio-fibular ligament), 2 fixation devices.

Radiologic evaluation of ankle fracture malunions of the fibula

Ankle fractures involving the distal fibula are common injuries. Malreductions and subsequent malunions of the distal fibula can result in worse clinical outcomes and posttraumatic arthritis. The ability to accurately evaluate and identify malreductions and malunions of the distal fibula is important. A number of different radiographic and CT measurements have been described to assess fibular length and rotation. This review highlights various radiologic measures and discusses their advantages and limitations.

A 3-Ligament Syndesmotic Injury Is at Higher Risk for Malreduction Than a 2-Ligament Injury: A CT-Based Analysis

BACKGROUND

Syndesmotic malreduction is common and has been associated to an impaired outcome. Various risk factors for DTFJ malreduction have been postulated. The aims of this study were to assess the DTFJ malreduction rate based on (1) the severity of the syndesmotic injury, (2) the anatomy of the tibial incisura, and (3) the fixation device used in patients treated with suture-button systems.

METHODS

This retrospective, radiographic study included all adult patients who were treated for an acute, unilateral, and unstable syndesmotic injury with a suture-button system and postoperative bilateral CT imaging. Included were isolated syndesmotic injuries and fracture cases. The number of syndesmotic ligaments injured, that is, 2-ligament (AiTFL+IOL) and 3-ligament (AiTFL+IOL+PiTFL), was rated for each patient. The quality of DTFJ reduction, as well as the anatomy of the tibial incisura, was rated based on the postoperative, bilateral CT images and the intraoperative DTFJ reduction was recalculated based on the drilling-tunnel deviation. The possible influence on the DTFJ malreduction rate was assessed.

RESULTS

A total of 147 patients were included, and 94 and 53 patients had a 2- and 3-ligament syndesmotic injury, respectively. In addition, 113 patients were treated with a single-button system, 26 with a double suture-button system, and 8 with a hybrid fixation (suture-button + screw). Malreduction was significantly higher in 3-ligament compared with 2-ligament injuries, both intraoperatively (51% vs 27%; P = .003) and postoperatively (28% vs 11%; P = .006). The tibial anatomy had no significant influence on the malreduction rates. No significant differences were seen per the different fixation devices used independent of the number of ligaments injured.

CONCLUSION

This study did not find an influence of the incisura's anatomy on the DTFJ malreduction rate. However, we did find that 3-ligament syndesmotic injuries carried a higher risk of intra- and postoperative malreduction compared with 2-ligament injuries.

Measuring External Rotation of the Fibula and Fibular Length in Bilateral Computed Tomography Scans: How Reliable Is This Method?

OBJECTIVES

During ankle fracture surgery, goals include accurate reduction and fixation of the fibula regarding rotation and fibular length. Bilateral postoperative computed tomography (CT) can be performed to assess fibular rotation using the talar dome angle, and fibular length. The aim of this study was to compare side-to-side differences of the fibular rotation and fibular length using bilateral CT scans of uninjured ankles.

METHODS

DESIGN

Retrospective.

SETTING

Single center, Level I Academic Trauma Center.

PATIENT SELECTION CRITERIA

Patients with bilateral CT scans of uninjured ankles.

OUTCOME MEASURES AND COMPARISONS

External rotation using the Nault talar dome method and fibular length using the coronal method of Prior et al. The average, difference, and ratio (injured side/healthy side) and interobserver variability were calculated.

RESULTS

There were 83 patients included (166 ankles, mean age 47 years, 77.1% male). A random set of 66 ankles (33 CT scans) were used to measure interobserver variability. The mean degrees of external rotation ranged from 6.6 to 7.7, mean difference ranged from 1.4 to 3.4 degrees, mean ratio ranged from 1.1 to 1.5, and interobserver variability ranged from 0.27 to 0.65. For fibular length, the mean ranged from 24.6 to 25.8 mm, mean difference in fibular length ranged from 0.5 to 2.1 mm, mean ratio ranged from 1.0 to 1.1 mm, and interobserver variability ranged from 0.45 to 0.73.

CONCLUSIONS

Using bilateral ankle CT scans, mean differences in fibular rotation using the Nault talar dome method were 1.4-3.4 degrees. The distal fibular length had a mean difference between both sides of 0.5-2.1 mm. Although the intraclass correlation's were low, the interleg differences between patients were small, making them useful for clinical practice.

LEVEL OF EVIDENCE

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

Value of Intraoperative 3D Imaging on the Quality of Reduction of the Distal Tibiofibular Joint When Using a Suture-Button System

BACKGROUND

The quality of reduction of the distal tibiofibular joint (DTFJ) has a major impact on the outcome. Novel suture-button systems as well as intraoperative 3D imaging can be applied to increase the quality of DTFJ reduction intraoperatively. The individual effect of either remains unknown. The aim of this study was to investigate the value of intraoperative 3D imaging on the quality of reduction of the DTFJ when using a suture-button system.

METHODS

Retrospective, radiographic study including adult patients who underwent surgical stabilization of the syndesmosis with a suture-button system for acute, unilateral, unstable syndesmotic injuries with postoperative bilateral CT imaging. The use of an intraoperative 3D scan was the individual surgeon's choice. Assessed was whether the intraoperative 3D imaging had an influence on the postoperative quality of DTFJ reduction and revision rates. These findings were put in perspective to the correction potential of the suture-button system.

RESULTS

A total of 147 patients were included; 76 of these received an intraoperative 3D imaging. Neither the rate of formal malreduction (17% vs 17%) nor the postoperative revision rate (4% vs 3%) differed significantly between patients with or without intraoperative 3D imaging. Intraoperative 3D imaging revealed a false-negative rate of 14%. The intrinsic correction potential of the suture-button system reduced the number of formally malreduced DTFJs in both groups by 51%.

CONCLUSION

The additional value of intraoperative 3D imaging to assess the quality of DTFJ reduction in our series did not improve syndesmotic reduction when using a flexible suture-button system.

LEVEL OF EVIDENCE

Level III, retrospective comparative cohort study.

Restoration of Anatomic Parameters and Syndesmotic Reduction After Intramedullary Nailing of Distal Fibular Fractures

Background:

Intramedullary nailing of the fibula (FN) is a method of fixation that has proven to be useful for treating distal fibular fractures (DFs). FN minimizes soft tissue complications and provides similar stability to plating, with fewer hardware-related symptoms. Nevertheless, FN has been associated with syndesmotic malreduction and the incapacity of restoring length and rotation of the fibula. We aimed to evaluate the fibular position and syndesmotic reduction after fixation with FN compared with the uninjured ankle in the immediate postoperative period.

Methods:

Prospective cohort study. Patients with DF fractures treated with IN between January 2017 and January 2020 were included. Immediate postoperative bilateral ankle CT was obtained in all cases. Fibular rotation, length, and translation as well as syndesmotic diastasis were measured on both ankles and compared by 3 independent observers.

Results:

Twenty-eight patients were included (16 women). The mean age was 46 years (range 16-91). Fracture type distribution according to AO/ASIF classification included 19 patients with 44.B (67.9%), 8 patients with 44.C (28.6%), and 1 patient with a 44.A fracture (3.6%). No significant differences were identified considering fibular rotation (P = .661), syndesmotic diastasis (P = .147), and fibular length (P = .115) between the injured and uninjured ankle. Fibular translation had statistical differences (P = .01) compared with the uninjured ankle. The intraclass correlation coefficient showed an excellent concordance between observers except for fibular translation on the injured ankle.

Conclusion:

In this cohort, fixation of DF fractures with FN allows restoration of anatomical parameters of the ankle in terms of fibular rotation, length, and syndesmotic diastasis. However, fibular translation had significant differences compared with the uninjured ankle based on bilateral CT scan evaluation.

Level of Evidence:

Level II, prospective cohort study.

Compensation of Dynamic Fixation Systems in the Quality of Reduction of Distal Tibiofibular Joint in Acute Syndesmotic Complex Injuries: A CT-Based Analysis

BACKGROUND

There is an ongoing discussion on how to best stabilize syndesmotic injuries. Previous studies have indicated a better quality of reduction of the distal tibiofibular joint (DTFJ) for the suture button systems compared to syndesmotic screw fixation. Still, the reason for this superiority remains unclear. The aims of this retrospective study were to (1) analyze the deviation of the tibial and fibular drilling tunnels of the suture button system and (2) to compare these to the quality of reduction of the DTFJ assessed on bilateral postoperative CT images.

METHODS

Included were all adult patients who underwent syndesmotic stabilization for an acute injury using a suture button system, with postoperative, bilateral CT imaging over a 10-year period. A total of 147 patients were eligible. Based on individually reconstructed axial CT slices, the postoperative quality of reduction of the DTFJs was rated on bilateral CT images. Furthermore, the rotation and translation of the suture button drilling tunnels were analyzed. Based on these measurements, the intraoperative reduction of the DTFJ was recalculated and again rated. Using these values, the correction potential of suture button systems on the reduction of the DTFJ was analyzed.

RESULTS

(1) The drilling tunnel deviated considerably for both rotation |2.3±2.1 degrees| (range: |0.0-13.1 degrees|) and translation |0.9±0.8 mm| (range: |0-4.3 mm|). Based on the deviation of the drilling tunnels in fibula and tibia, the calculated intraoperative reduction of the DTFJ was classified as malreduced in 35.4%. (2) The DTFJ was postoperatively identified as malreduced in 17% of patients. Overall, the suture button system tended to compensate toward a more anatomical reduction both in the axial and sagittal plane.

CONCLUSION

A suture button system postoperatively deviates and apparently has the capacity to compensate for intraoperative malreduction. Analysis of the drilling tunnels revealed that the use of a rigid fixation system would have doubled the postoperative malreduction rate.

Detection of fibular rotational changes in cone beam CT: experimental study in a specimen model

Background

In syndesmotic injuries, incorrect reduction leads to early arthrosis of the ankle joint. Being able to analyze the reduction result is therefore crucial for obtaining an anatomical reduction. Several studies that assess fibular rotation in the incisura have already been published. The aim of the study was to validate measurement methods that use cone beam computed tomography imaging to detect rotational malpositions of the fibula in a standardized specimen model.

Methods

An artificial Maisonneuve injury was created on 16 pairs of fresh-frozen lower legs. Using a stable instrument, rotational malpositions of 5, 10, and 15° internal and external rotation were generated. For each malposition of the fibula, a cone beam computed tomography scan was performed. Subsequently, the malpositions were measured and statistically evaluated with t-tests using two measuring methods: angle (γ) at 10 mm proximal to the tibial joint line and the angle (δ) at 6 mm distal to the talar joint line.

Results

Rotational malpositions of ≥ 10° could be reliably displayed in the 3D images using the measuring method with angle δ. For angle γ significant results could only be displayed for an external rotation malposition of 15°.

Conclusions

Clinically relevant rotational malpositions of the fibula in comparison with an uninjured contralateral side can be reliably detected using intraoperative 3D imaging with a C-arm cone beam computed tomography. This may allow surgeons to achieve better reduction of fibular malpositions in the incisura tibiofibularis.

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.

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.

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.

Intraoperative chertsey test, is it a reliable alternative to computed tomography scan for diagnosing syndesmotic injuries of the ankle?

Background:

The present study aims to evaluate the diagnostic exactitude of the intraoperative Chertsey test in tibiofibular syndesmotic injuries in patients with malleolar fractures, in comparison with a computed tomography (CT) scan.

Materials and Methods:

In this study, patients with malleolar fractures operated between 2018 and 2020 were examined. Thirty-nine patients were enrolled in the study. A three-dimensional preoperative CT scan was obtained. The opposite unfractured ankle was also scanned and considered as the control group. The Chertsey test was performed during the operation to assess the syndesmosis injury. Then, patients were partitioned into two distinct groups, considering the condition of their ankle, namely the Chertsey positive (unstable syndesmosis) group and the Chertsey negative (stable syndesmosis) group.

Results:

The outcomes of the present survey illustrated that the Chertsey test was positive in 16 patients (41.03%) and negative in 23 patients (59.07%). The median of all CT scan parameters (anterior tibiofibular distances (TFD), middle TFD, posterior TFD, and maximal TFD and volume) before surgery in the group of patients with a positive Chertsey test was significantly higher, measured against the unfractured control group (P < 0.001 for all parameters). Furthermore, a comparison of CT scan parameters and syndesmosis space volume before surgery between the two groups of patients with positive and negative Chertsey test results showed that the measurement of parameters in Chertsey-positive patients was significantly higher than the Chertsey-negative patients (P < 0.001).

Conclusion:

Chertsey test could be used to diagnose syndesmosis injuries in patients with malleolar fractures due to its high importance in the outcome of patients.

Influence of unstable ankle fracture (type Weber C), osteosynthesis and syndesmotic transfixation on position of fibula in tibiofibular notch: a cadaveric study

PURPOSE

The aim of the cadaveric study was to determine the effects of an unstable ankle fracture on the position of the fibula in the incisural notch and subsequently to evaluate the alterations resulting from the individual steps of a guideline-based osteosynthesis.

METHODS

In a specimen model with 20 uninjured fresh-frozen lower legs with induced unstable fracture of the fibula (type Weber C), a guideline-based osteosynthesis was performed. The distances between the anterior and posterior edges of the tibia and fibula and in the center of the incisural notch, as well as the rotation angle of the fibula, were measured in the acquired 3D image data sets and were compared with the intact condition of the ankle mortise.

RESULTS

The dissection of the syndesmosis and osteotomy of the fibula results in an external rotation the fibula by 3.6° (p = 0.000), while the distance between the anterior edge of the tibia and the fibula widens by 1.86 mm (p = 0.000). After osteosynthesis of the fibula and transfixation of the syndesmotic region using a positioning screw, the posterior distance is no longer substantially increased by 0.22 mm (p = 0.103) but also reduced by 0.1 mm (p = 0.104) in the tibiofibular notch. The external rotation of the fibula remains slightly increased by just 0.45° (p = 0.009).

CONCLUSION

The results indicate that there is a tendency for over-compression when adjusting the tibiofibular distance and that the fibula in the tibiofibular notch tends to remain slightly rotated externally.

A standardized approach for exact CT-based three-dimensional position analysis in the distal tibiofibular joint

Background

Assessment of tibiofibular reduction presents an intra- and postoperative challenge. Numerous two-dimensional measurement methods have been described, most of them highly dependent on leg orientation and rater. Aim of the present work was to develop a standardized and orientation-independent 3D based method for the assessment of syndesmotic joint position.

Methods

In a retrospective single center study, 3D models of bilateral ankle joints, either after unilateral syndesmosis stabilization (operative group) or with no injury (native group) were superimposed (best fit matching) and aligned uniformly. Based on center of gravity calculations three orientation- and rater-independent parameters were determined: tibiofibular clears space (CS), vertical offset between both fibulae, and translation angle of the fibulae about tibia axis.

Results

Bilateral CT datasets of 57 native and 47 postoperative patients were analyzed. In the native group mean CS was 2.7 (SD, 0.8; range, 0.7–4.9) mm, mean CS side difference was 0.62 (SD, 0.45) mm and mean translation angle was 1.6 (SD, 1.4) degrees regarding absolute values. The operative group was found to show a significantly higher CS side difference of 0.88 (SD, 0.75) mm compared to native group (P = .046). Compared to the healthy contralateral side, operated fibulae showed mean proximal displacement of 0.56 (SD, 1.67) mm (P = .025), dorsal displacement of 1.5 (SD 4.1) degrees (P = .017).

Conclusion

By using 3D best fit matching, orientation- and rater-dependent errors can be minimized. Large interindividual and small intraindividual differences of uninjured couples support previous recommendations for bilateral imaging.

Trial registration: AZ 131/18-ek; AZ 361/19-ek

Level of evidence

Level III.

The Valid Diagnostic Parameters in Bilateral CT Scan to Predict Unstable Syndesmotic Injury with Ankle Fracture

The purpose of this study is to evaluate the reasonable parameters to predict unstable syndesmotic injuries in ankle fractures. Seventy consecutive patients who underwent preoperative bilateral computed tomography (CT) scans were enrolled. Group A consisted of 20 patients intraoperatively diagnosed with syndesmotic injuries according to an intraoperative stress test and group B consisted of 50 patients who had nosyndesmotic injuries. The tibiofibular overlap (TFO) and tibiofibular clear space (TFCS) were measured using preoperative ankle radiographs. Measuring the anterior fibular distance (AFD), posterior fibular distance (PFD), anterior translation distance (AT), fibular diastasis (FD), anterior-posterior translation (APT), fibular length (FL), and surface area of syndesmosis (SAS) 1.0 and 1.5 which 1.0 cm and 1.5 cm above the tibial plafond was done via preoperative CT scan. The ratio of measurements (Injured/Intact) of the TFO, PFD, APD, and SAS 1.0 showed statistically significant differences. The researchers identified the SAS 1.0 as the most reasonable parameter to predict transfixation using receiver-operating characteristic (ROC) curve analysis. The SAS 1.0 is most valid parameter to predict syndesmotic injuries in this study and these results show that performing a bilateral CT scan on an ankle fracture may provide substantial information in measuring valid parameters.

Comparison of External Torque to Axial Loading in Detecting 3-Dimensional Displacement of Syndesmotic Ankle Injuries

BACKGROUND

Current imaging techniques try to quantify 3-dimensional displacement of syndesmotic ankle injuries using 2-dimensional measurements, which may obscure an exact diagnosis. Therefore, our aim was to determine 3-dimensional displacement of syndesmotic ankle injuries under load and torque using a weightbearing computed tomography (WBCT) and to assess the relation with previously established 2-dimensional measurements.

METHODS

Seven paired cadaver specimens were mounted into a radiolucent frame. WBCT scans were obtained to generate 3-dimensional models after different patterns of axial load (0 kg, 85 kg) combined with external torque (0, 10 Nm). Sequential imaging was repeated in ankles containing intact syndesmotic ligaments, sectioning of the anterior inferior tibiofibular ligament (AITFL; condition 1A), deltoid ligament (DL; condition 1B), combined AITFL+DL (condition 2), and AITFl+DL+interosseous membrane (condition 3). Reference anatomical landmarks were established relative to the intact position of the fibula to quantify displacement. A subsequent correlation analysis was performed between the obtained 2- and 3-dimensional measurements.

RESULTS

Axial load increased lateral translation (mean = -0.9 mm, 95% confidence interval [CI]: 1.3, -0.1) significantly in condition 2 relative to the intact ankle (P < .05) but did not demonstrate other significant displacements. External torque increased displacement significantly in all directions (P < .05), except for dorsal translation of the fibula (P > .05). The highest displacement could be detected when external torque was applied in condition 3 and consisted of posterior translation (mean = -3.1 mm; 95% CI: -4.8, -2.7) and external rotation (mean = -4.7 degrees; 95% CI: -5.6, -2.9). Pearson correlation coefficients between the 2-dimensional and 3-dimensional measurements were moderate and ranged from 0.31 to 0.56 (P < .05).

CONCLUSION

External torque demonstrated superiority over axial load in detecting syndesmotic ankle instability. Axial load increased lateral translation; however, differences were submillimeter in magnitude until torque was applied. A moderate correlation was found with previously established 2-dimensional measurements.

CLINICAL RELEVANCE

In clinical practice these findings substantiate application of external torque in current imaging modalities to improve detection of syndesmotic ankle injuries.

Accuracy of cone-beam computed tomography for syndesmosis injury diagnosis compared to conventional computed tomography

BACKGROUND

Syndesmosis injury can lead to ankle mortise instability and early osteoarthritis. Several multiple detector computed tomography (MDCT) methods for measurement have been developed. Weight-bearing cone beam CT (WB CBCT) is an emerging technique that offers the possibility of upright-position scanning and lower doses. This study sought to assess the diagnostic accuracy of WB CBCT in syndesmose injury compared to MDCT, with instability confirmed via manual testing upon arthroscopic examination.

METHODS

Three musculoskeletal radiologists with different levels of expertise prospectively analyzed 11 MDCT and eight WB CBCT scans of the same trauma-afflicted ankles with clinical suspicion of syndesmosis lesion over a period of 5 months. They evaluated 10 methods of measurement in both sides. Syndesmosis was considered pathological on arthroscopic examination in four patients. Correlation between readers was evaluated with intra-class correlation testing (p < 0.05 was considered significant). Capacity of discrimination was assessed by area under the curve (AUC) for all methods.

RESULTS

Inter-observer agreement was near excellent for both WB CBCT and MDCT for the anterior tibio-fibular (TF) distance (ICC = 0.781 and 0.831, respectively), posterior TF distance (ICC = 0.841 and 0.826), minimal TF distance (ICC = 0.899 and 0.875), and TF surface (ICC = 0.93 and 0.84). AUC were better for MDCT than WB CBCT in assessing syndesmosis instability for: anterior TF distance (ROC = 0.869 vs. 0.555, p = 0.01), minimal TF distance (ROC = 0.883 vs. 0.608, p = 0.02) and antero-posterior fibular translation (ROC = 0.894 vs. 0.467, p = 0.006).

CONCLUSIONS

MDCT demonstrated better ability to distinguish pathological syndesmosis than WB CBCT, with the antero-posterior fibular translation the best discriminating measurement. The physiological widening of the contralateral syndesmosis occurring with the WB CBCT upright position may explain these results.

Validation of radiological reduction criteria with intraoperative cone beam CT in unstable syndesmotic injuries

Purpose

Acute unstable syndesmotic lesions are regularly treated with closed or open reduction and fixation with either a positioning screw or tight rope. Conventional fluoroscopy is limited to identify a malreduction of the ankle mortise. The aim of the study was to validate the reduction criteria of intraoperative cone beam CT in unstable syndesmotic injuries by analyzing the clinical outcome.

Methods

Acute unstable syndesmotic injuries were treated with a positioning screw fixation, and the reduction in the ankle mortise was evaluated with intraoperative cone beam CT. The patients were grouped postoperatively according to the radiological reduction criteria in the intraoperative 3D images. The reduction criteria were unknown to the surgeons. Malreduction was assumed if one or more reduction criteria were not fulfilled.

Results

Seventy-three of the 127 patients could be included in the study (follow-up rate 57.5%). For 41 patients (56.2%), a radiological optimal reduction was achieved (Group 1), and in 32 patients (43.8%) a radiological adverse reduction was found (Group 2). Group 1 scored significantly higher in the Olerud/Molander score (92.44 ± 10.73 vs. 65.47 ± 28.77) (p = 0.003), revealed a significantly higher range of motion (ROM) (53.44 vs. 24.17°) (p = 0.001) and a significantly reduced Kellgren/Lawrence osteoarthritis score (1.24 vs. 1.79) (p = 0.029). The linear regression analysis revealed a correlation for the two groups with the values scored in the Olerud/Molander score (p < 0.01).

Conclusion

The reduction criteria in intraoperative cone beam CT applied to unstable syndesmotic injuries could be validated. Patients with an anatomic reduced acute unstable syndesmotic injury according to the criteria have a significantly better clinical outcome.

Reliability of distal tibio-fibular syndesmotic instability measurements using weightbearing and non-weightbearing cone-beam CT

BACKGROUND

To investigate the reliability and reproducibility of syndesmosis measurements on weightbearing (WB) cone-beam computed tomography (CBCT) images and compare them with measurements obtained using non-weightbearing (NWB) images.

METHODS

In this IRB-approved, retrospective study of 5 men and 9 women with prior ankle injuries, simultaneous WB and NWB CBCT scans were taken. A set of 21 syndesmosis measurements using WB and NWB images were performed by 3 independent observers. Pearson/Spearman correlation and intra-class correlation (ICC) were used to assess intra- and inter-observer reliability, respectively.

RESULTS

We observed substantial to perfect intra-observer reliability (ICC=0.72-0.99) in 20 measurements. Moderate to perfect agreement (ICC=0.45-0.97) between observers was noted in 19 measurements.

CONCLUSION

Measurements evaluating the distance between tibia and fibula in the axial plane 10mm above the plafond had high intra- and inter-observer reliability. Mean posterior tibio-fibular distance, diastasis, and angular measurement were significantly different between WB and NWB images.

Evaluation of Syndesmosis Reduction on CT Scan

BACKGROUND

Computed tomography (CT) imaging has traditionally been considered the gold standard for evaluation of syndesmostic reduction, but there is no uniformly accepted method to assess reduction. The aim of this study was to evaluate the intra- and interobserver reliability of published measurement techniques for evaluation of syndesmotic reduction on weightbearing CT scan (WBCT) in hopes of determining which method is best.

METHODS

Medical records were reviewed to identify patients who underwent operative stabilization of unilateral syndesmotic injuries. Exclusion criteria included patients younger than 18 years, ipsilateral fractures extending to the tibial plafond, any contralateral ankle fracture or syndesmotic injury, and body mass index greater than 40 kg/m². Twenty eligible patients underwent WBCT evaluation of both ankles at an average of 3 years after syndesmotic fixation. The anatomic accuracy of syndesmotic reduction was evaluated by 2 observers using axial CT images at a level 1 cm proximal to the tibial plafond using 9 previously published radiological measurement techniques. Inter- and intraobserver reliability were assessed for each evaluation method.

RESULTS

The syndesmotic area calculation showed the highest interobserver reliability (0.96), the highest intraobserver reliability for observer 2 (0.97), and the second highest intraobserver reliability for observer 1 (0.92). Fibular rotation had the second highest interobserver reliability in our results (0.84), with intraobserver reliability of 0.91 and 0.8 for first and second observers, respectively. The intraobserver reliability of the side-by-side method was 0.49 and 0.24 for the first and second observers, respectively, and the interobserver reliability was 0.26.

CONCLUSION

Qualitatively assessing syndesmotic reduction via side-by-side comparison with the uninjured ankle had the least intra- and interobserver reliability and should not be relied on to determine syndesmotic reduction quality. In contradistinction, syndesmotic area calculation demonstrated the highest reliability when evaluating syndesmotic reduction, followed by fibular rotation. Given that syndesmotic area measurement techniques are not readily available on standard image viewers, technologically updating image viewers to allow such calculation would make this approach more accessible in clinical practice.

LEVEL OF EVIDENCE

Level IV, case series.

Defining the three most responsive and specific CT measurements of ankle syndesmotic malreduction

PURPOSE

The purpose of this study was to compare the reliability and accuracy of existing computed tomography (CT) methods for measuring the distal tibiofibular syndesmosis in uninjured, paired cadaveric specimens and in simulated malreduction models. It was hypothesized that a repeatable set of measurements exists to accurately and quantitatively describe the typical forms of syndesmotic malreduction using contralateral ankle comparison.

METHODS

Twelve cadaveric lower-leg specimen pairs were imaged with CT to generate models for this study. Thirty-five measurements were performed on each native model. Next, four distinct fibular malreductions were produced via digital simulation and all measurements were repeated for each state: (1) 2-mm lateral translation; (2) 2-mm posterior translation; (3) 7-degree external rotation; (4) the previous three states combined. The modified standardized response mean (mSRM) was calculated for each measurement. To assess rater reliability and side-to-side agreements of the native state measurements, intraclass correlation coefficients (ICC) and Pearson correlation coefficients (PCC) were calculated, respectively.

RESULTS

The most responsive measurements for detecting isolated malreduction were the Leporjärvi clear space for lateral translation, the Nault anterior tibiofibular distance for posterior translation, and the Nault talar dome angle for external rotation of the fibula. These measurements demonstrated fair to excellent inter-rater ICCs (0.64-0.76) and variable side-to-side PCCs (0.14-0.47).

CONCLUSIONS

The most reliable method to assess the syndesmosis on CT was to compare side-to-side differences using three distinct measurements, one for each type of fibular malreduction, allowing assessment of the magnitude and directionality of syndesmosis malreduction. Reliable evaluation is essential for assessing subtle syndesmosis injuries, malreduction and surgical planning.

Ankle Fractures: An Expert Survey of Orthopaedic Trauma Association Members and Evidence-Based Treatment Recommendations

OBJECTIVES

To describe current practice patterns of orthopaedic trauma experts regarding the management of ankle fractures, to review the current literature, and to provide recommendations for care based on a standardized grading system.

DESIGN

Web-based survey.

PARTICIPANTS

Orthopaedic Trauma Association (OTA) members.

METHODS

A 27-item web-based questionnaire was advertised to members of the OTA. Using a cross-sectional survey study design, we evaluated the preferences in diagnosis and treatment of ankle fractures.

RESULTS

One hundred sixty-six of 1967 OTA members (8.4%) completed the survey (16% of active members). There is considerable variability in the preferred method of diagnosis and treatment of ankle fractures among the members surveyed. Most responses are in keeping with best evidence available.

CONCLUSIONS

Current controversy remains in the management of ankle fractures. This is reflected in the treatment preferences of the OTA members who responded to this survey.

LEVEL OF EVIDENCE

Therapeutic Level V. See Instructions for authors for a complete description of levels of evidence.

Cone-beam CT measurements of distal tibio-fibular syndesmosis in asymptomatic uninjured ankles: does weight-bearing matter?

OBJECTIVE

To evaluate the influence of weight-bearing (WB) load in standard axial ankle syndesmotic measurements using cone beam CT (CBCT) examination of asymptomatic uninjured ankles.

MATERIALS AND METHODS

In this IRB approved, prospective study, patients with previous unilateral ankle fractures were recruited. We simultaneously scanned the injured ankles and asymptomatic contralateral ankles of 27 patients in both WB and NWB modes. For this study, only asymptomatic contralateral ankles with normal plain radiographs were included. Twelve standardized syndesmosis measurements at two axial planes (10 mm above the tibial plafond and 5 mm below the talar dome) were obtained by two expert readers using a custom CBCT viewer with the capability for geometric measurements between user-identified anatomical landmarks. Inter-reader reliability between two readers was obtained using the intra-class correlation coefficient (ICC). We compared the WB and NWB measurements using paired t test.

RESULTS

Significant agreement was observed between two readers for both WB and NWB measurements (p <0.05). ICC values for WB and NWB measurements had a range of 50-95 and 31-71 respectively. Mean values of the medial clear space on WB images (1.75, 95% confidence interval [95% CI]: 1.6, 1.9) were significantly lower than on NWB images (2.05, 95% CI: 1.8, 2.2) measurements (p <0.001). There was no significant difference between the remaining WB and NWB measurements.

CONCLUSION

Measurements obtained from WB images are reliable. Except for the medial clear space, no significant difference in syndesmotic measurements were observed during the WB mode of CBCT acquisition, implying that the tibio-fibular relationship remains unchanged when the physiological axial weight-bearing load is applied.

Assessing Quality of Syndesmotic Reduction in Surgically Treated Acute Syndesmotic Injuries: A Systematic Review

There is no universal method with cutoff values for the assessment of distal tibiofibular joint reduction in acute syndesmotic injuries. It is important to detect malreductions because they may lead to impaired functional outcome and may demand reoperations. The aim of this study was to systematically review the literature to evaluate the appropriateness of different image techniques in determining syndesmotic malalignment. A literature search was conducted in Medline, Embase, and the Cochrane Library to search for articles assessing syndesmotic reduction. Excluded were articles where no criteria and/or measurements for syndesmotic reduction were provided, only normative values were provided and reviews. In total, 2157 articles were found, of which 1421 studies were screened for title and abstract after exclusion of duplicates. One hundred ten studies were eligible for full-text analysis. Of these, 61 were excluded. Three studies where added after screening the included references. Fifty-two studies were included, of which 32 were original publications and 20 were publications referring to the original publications. From the original publications, 14 used plains radiographs, 19 computed tomographic (CT) scans, and 5 used 3-dimensional CT scans (some authors used >1 modality in their study). For each modality, a large number of parameters and different cutoff values were reported. CT scanning is superior to plain radiography in the assessment of the quality of joint reduction. Parameters used the most were fibular position in the incisura and fibular rotation. The criteria for adequate reduction should at least include the position of the fibula in the incisura and rotation of the fibula, while ensuring adequate fibular length, all equaling or at least approaching the values of the uninjured contralateral side.

Templating of Syndesmotic Ankle Lesions by Use of 3D Analysis in Weightbearing and Nonweightbearing CT

BACKGROUND:

Diagnosis and operative treatment of syndesmotic ankle injuries remain challenging due to the limitations of 2-dimensional imaging. The aim of this study was therefore to develop a reproducible method to quantify the displacement of a syndesmotic lesion based on 3-dimensional computed imaging techniques.

METHODS:

Eighteen patients with a unilateral syndesmotic lesion were included. Bilateral imaging was performed with weightbearing cone-beam computed tomography (CT) in case of a high ankle sprain (n = 12) and by nonweightbearing CT in case of a fracture-associated syndesmotic lesion (n = 6). The healthy ankle was used as a template after being mirrored and superimposed on the contralateral ankle. The following anatomical landmarks of the distal fibula were computed: the most lateral aspect of the lateral malleolus and the anterior and posterior tubercle. The change in position of these landmarks relative to the stationary, healthy fibula was used to quantify the syndesmotic lesion. A control group of 7 studies was used.

RESULTS:

The main clinical relevant findings demonstrated a statistically significant difference between the mean mediolateral diastasis of both the sprained (mean [SD], 1.6 [1.0] mm) and the fracture group (mean [SD], 1.7 [0.6] mm) compared to the control group ( P < .001). The mean external rotation was statistically different when comparing the sprained (mean [SD], 4.7 [2.7] degrees) and the fracture group (mean [SD], 7.0 [7.1] degrees) to the control group ( P < .05).

CONCLUSION:

This study evaluated an effective method for quantifying a unilateral syndesmotic lesion of the ankle. Applications in clinical practice could improve diagnostic accuracy and potentially aid in preoperative planning by determining which correction needs to be achieved to have the fibula correctly reduced in the syndesmosis.

LEVEL OF EVIDENCE:

Level III, retrospective comparative study.

Outcomes of Acute Hematogenous Periprosthetic Joint Infection in Total Ankle Arthroplasty Treated With Irrigation, Debridement, and Polyethylene Exchange

BACKGROUND

Acute hematogenous periprosthetic joint infection (PJI) is defined in the literature as infection diagnosed and treated within 2 to 4 weeks from the onset of symptoms. In total hip and knee arthroplasty, irrigation and debridement (I&D) and polyethylene exchange with component retention has been studied extensively. However, there is minimal literature evaluating this treatment method for PJI in total ankle arthroplasty (TAA). The purpose of this study was to evaluate both the clinical and patient-reported outcomes and survivorship of TAA acute hematogenous PJIs treated with I&D and polyethylene exchange.

METHODS

A single-center, retrospective chart review of prospectively collected data in patients with TAA PJI who subsequently underwent I&D and polyethylene exchange with retention of metal components was conducted. The primary outcome was failure rate of I&D and polyethylene exchange, where failure was defined as subsequent removal of all components and 2-stage revision or arthrodesis. Patient-reported outcomes collected before primary arthroplasty, after primary arthroplasty, and after polyethylene exchange were also analyzed.

RESULTS

We identified 14 patients with acute hematogenous PJI who underwent I&D and polyethylene exchange with retention of metal components. The mean time from primary TAA to symptoms was 43 months (range 1-147 months). The average time from onset of symptoms to I&D and polyethylene exchange was 11.4 ± 5.6 days. The mean follow-up after this surgery was 2.8 ± 1.5 years. The long-term failure rate was 54%. The most common bacteria isolated in patients who failed was methicillin-resistant Staphylococcus aureus (MRSA). The most common bacteria isolated in patients who retained their implants was methicillin-sensitive Staphylococcus aureus (MSSA). Visual analog scale (VAS), Short Musculoskeletal Function Assessment (SMFA), Short Form-36 (SF-36), and American Orthopaedic Foot & Ankle Society (AOFAS) hindfoot scale showed significant improvement when compared to preoperative scores in patients who retained their implants both after primary and after I&D and polyethylene exchange.

CONCLUSIONS

I&D and polyethylene exchange with retention of metal components has a long-term survivorship comparable to those reported in the total knee and total hip arthroplasty literature. Patient-reported outcomes after I&D and polyethylene exchange were comparable to those collected after primary arthroplasty in those patients who ultimately retained their implants. Two variables in this cohort that were associated with I&D and polyethylene exchange failure include time the patient was symptomatic prior to I&D as well as organism isolated on culture. With a failure rate of 54%, the authors recommend thorough evaluation on a case-by-case basis prior to indicating a patient for single-stage I&D with polyethylene exchange.

LEVELS OF EVIDENCE

Level IV, case series.