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Article

Impact of Distal Tibiofibular Joint Anatomy on Reduction Outcome in Dynamic Suture Button Stabilization of the Distal Syndesmosis—A CT Analysis

by
Robert Hennings
1,*,
Carolin Fuchs
1,
Firas Souleiman
1,
Henkelmann Jeanette
2,
Ullrich Joseph Spiegl
3,
Christian Kleber
1 and
Annette B. Ahrberg-Spiegl
1
1
Department of Orthopedics, Traumatology and Plastic Surgery, University Hospital Leipzig, Liebigstraße 20, Haus 4, 04103 Leipzig, Germany
2
Department of Diagnostic and Interventional Radiology, University Hospital Leipzig, Leipzig, Liebigstraße 20, Haus 4, 04103 Leipzig, Germany
3
Clinic for Trauma Surgery and Orthopaedics, Munich Harlaching, Sanatoriumspl. 2, 81545 München, Germany
*
Author to whom correspondence should be addressed.
Trauma Care 2025, 5(2), 10; https://doi.org/10.3390/traumacare5020010 (registering DOI)
Submission received: 13 February 2025 / Revised: 5 May 2025 / Accepted: 15 May 2025 / Published: 18 May 2025
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Abstract

:
Introduction: The anatomy of the distal tibiofibular joint (DTFJ) has been demonstrated to influence the radiological outcome of reduction with syndesmotic screw fixation in the course of ankle fracture treatment. The objective of this study was to describe the anatomy of the DTFJ and to analyze the effect of incisura anatomy on syndesmotic stabilization with suture button systems (SBS), also in the context of their flexible nature of fixation. Materials and Methods: Forty-four (21 females, 23 males) consecutive postoperative bilateral computed tomography scans after stabilization of the DTFJ by SBS in the course of operative treatment of unstable ankle fractures were retrospectively analyzed. The anatomy of the DTFJ was evaluated by examining the following parameters: depth of the tibial incisura (DI), rotation of the incisura (ROI), Nault talar dome angle (NTDA), Leporjärvi clear space (LCS), anterior tibiofibular distance (antTFD), and fibula engagement (FE). The side-to-side (Δ) of LCS, NTDA, and antTFD, which analyzed the reduction result, were correlated with DI, FE, ROI, and NTDA, as well as the transverse offset (TO), reflecting the flexible nature of fixation. Results: Patients with slight overtightening (ΔLCS > −1 mm) showed a fibula that protruded less into the incisura on the native side (smaller FE) compared to symmetrical reduced patients and to patients with slight diastasis (p < 0.05). There was no relationship between the parameters describing the anatomy of the incisura and parameters assessing the parameter of the “flexible nature of fixation” (rs < 0.300). Regarding the anatomical parameters, it was observed that there were inter-individual differences of more than 4 mm (p > 0.05). Conclusions: The considerable inter-individual anatomical variability of the DTFJ was confirmed. The morphological configuration of the incisura has no impact on the immediate radiological reduction result after SBS stabilization of the DTFG, as determined by CT. The extent of the flexible nature of fixation is also not affected by the morphology of the incisura. Stabilization of the DTFJ can be performed regardless of the anatomical configuration.

1. Introduction

There is a consensus that anatomical reduction and stabilization of a proven unstable distal tibiofibular joint (DTFJ) in the course of the operative treatment of unstable ankle fractures is necessary. Incongruity after stabilization is associated with increased pressure on the talus and a worse functional outcome, which may result in long-term complications [1,2,3]. It has been demonstrated that malreduction of the DTFJ, particularly in the sagittal plane, occurs in up to 40% of cases after stabilization with a syndesmosis screw (SYS) or suture button system (SBS) [4,5]. Therefore, it is crucial to identify and address all risk factors for malreduction of DTFJ before and during surgical treatment of ankle fractures.
These factors may be patient-specific or fracture-specific [6,7,8]. Thus, it has been demonstrated that certain anatomical configurations increase the risk of malreduction following stabilization of the DTFJ with SYS [6,7,8]. A syndesmosis with a deep tibial incisura (incisura) and a fibula that does not engage the tibial incisura is at an increased risk of overtightening. An anteverted incisura poses a risk of anterior fibular translation, while a retroverted incisura poses a risk of posterior fibular translation [7,9].
In addition to the SYS, stabilization with a suture button system (SBS) has become established [4,10,11]. In contrast to the static stabilization offered by SYS, SBS stabilization has been demonstrated to possess a dynamic component that can be termed the Flexible Nature of Fixation (FNF) [5,12,13,14,15]. This flexible property may contribute to a reduction in the rate of sagittal malreduction [5,14].
Moreover, the anatomical configuration of the DTFJ exhibits considerable inter-individual and gender-dependent variability, which poses a notable challenge to the assessment of joint congruity in the context of ankle fracture treatment [16,17,18]. It has been shown that unilateral intraoperative fluoroscopy and postoperative plain radiography are less precise than computed tomography (CT) in assessing syndesmotic reduction, in particular in the sagittal direction [2,11,12,19,20,21]. Based on these findings, it may be recommended that intra- or postoperative bilateral computed tomography (CT) be performed to precisely evaluate the congruity of the DTFJ following surgical stabilization, both by SYS and by SBS [2,4,11,17,21,22].
Further verification is required regarding the impact of incisura anatomy on the radiological reduction outcome of DTFJ after stabilization using SBS. The objective of this study was to assess the anatomy of the DTFJ and the impact of the incisura anatomy on the dynamic stabilization of the DTFJ, with particular focus on its flexible nature of fixation. It was hypothesized that stabilization via suture button systems can be performed regardless of anatomical variations.

2. Materials and Methods

The local institutional review board gave approval for the study beforehand (AZ 488/19-ek).
This retrospective study included 44 (61%) out of 65 consecutive adult patients who underwent surgical stabilization of the DTFJ in the course of open reduction and internal fixation of unstable ankle fractures by suture button system (SBS) and met the inclusion criteria (Table 1). Thirteen patients with CT slice thickness of >1 mm, 11 patients with monolateral CT control, and four patients with inadequate bony osteosynthesis were excluded from the study. The identified patients were stored in an electronic database using SPSS (version 24, Chicago, IL, USA), with their data pseudonymized.
All fractures were classified and treated in accordance with the “Arbeitsgruppe für Osteosynthesefragen” (AO) classification at a trauma level I center [23,24]. For patients in whom no preoperative instability of the distal tibiofibular joint (DTFJ) was evident, standardized intraoperative assessment of instability was conducted following anatomical fracture stabilization. This was achieved with the hook test, as recommended by AO for coronal instability [24,25,26,27]. In this procedure, the distal fibula is grasped with a hook and pulled horizontally towards the lateral side. The foot is fixed by the examiner [28]. Subsequently, the external rotation test was performed to assess sagittal and rotational instability under fluoroscopy [28]. In both tests the beam is aligned perpendicular to the tibia and centered at the joint line, while the foot is rotated internally by 15–20° while the ankle joint is in the neutral position [23,25]. Once the instability had been verified, reduction and preliminary K-wire fixation of the syndesmosis were carried out under visualization via the chosen approach. Following verification of the reduction using fluoroscopy, final stabilization was performed with a suture-button device (TightRope®, Arthrex, Naples, FL, USA) [29].
As part of the treatment of unstable ankle fractures, the syndesmosis reduction is assessed by postoperative bilateral CT control, which is considered to be the hospital’s internal standard in accordance with the literature [2,6,19,21]. All bilateral CT scans were obtained during the inpatient period without the administration of intravenous contrast medium. The patients were positioned supine with their feet fixed symmetrically in a standardized position: feet rotated 15–20° internally and the ankle joints in a neutral position. Images were acquired using a multidetector CT scanner (iCT 256, Philips, Amsterdam, The Netherlands) and were reconstructed in slice thicknesses of 0.67 mm to 1 mm in axial, sagittal, and coronal orientations.
The following parameters were selected to describe the anatomy of the tibial incisura. These included the depth of the incisura (DI), the fibula engagement (FE), the Leporjärvi clear space (LCS), the Nault talar dome angle (NTDA), the anterior tibiofibular distance (antTFD), and the rotation of the incisura (ROI) of the native side. These were measured 10 mm proximal to the plafond, as previously described (Figure 1) [8,16,30,31]. All parameters have been proven to have high reliability [9,23]. Positive values of FE represent tibiofibular overlap and ROI greater than 90°, a dorsally opened incisura plane (Figure 1a,b). To verify the comparability of the two sides, the DI of the native and stabilized sides were compared.
The syndesmotic reduction was also assessed 10 mm proximal of the tibial plafond using the LCS to analyze the medial–lateral translation (coronal plane), the NTDA to evaluate the rotation (transversal plane), and the antTFD for protrusion (sagittal plane, Figure 2a) [6,8,30,31]. The parameters were assessed for both sides, and the side-to-side difference (Δ) between the injured and uninjured sides was calculated (ΔLCS, ΔNTDA, and ΔantTFD). A positive ΔLCS indicates widening of the syndesmosis, a positive ΔantTFD defines a posterior translation of the fibula at the stabilized DTFJ, and a positive ΔNTDA represents an increased external rotation of the fibula at the stabilized DTFJ [14].
To facilitate comparison with results from the limited literature on static stabilization with a syndesmotic screw, the threshold values in this analysis were set to more than 1.0 mm for ΔLCS and ΔantTFD and more than 5° for ΔNTDA as the definition of incongruence [6,32]. This is to be distinguished from the definition of malreduction, which is defined as a side-to-side difference of more than two millimeters for |ΔLCS|, |ΔantTFD| [2,3,14,19,22,32,33,34].
To quantify the FNF, the transverse offset (TO) of the burr channels was measured in accordance with the previously described methodology (sagittal plane, Figure 2a) [20]. The intra-rater and inter-rater reliabilities for the parameters describing the ‘FNF’ have been proven to be excellent (α > 0.90) [14].
Initially, the centers of the drill channel of the tibia (A and B) and fibula (C and D) were delineated in line with the cortical bone. Subsequently, the tibia line was drawn from point A to B and the fibula line from point D to point C. The tibial line was extended to point B on the fibula side. The midpoint of the fibular line (F) was marked, and the perpendicular line from F was drawn to the lines A and B; the intersection was marked as E. The measured distance from E to F is defined as TO and quantifies the FNF of TightRope® stabilization.
It was assumed that the reduction was temporarily fixed before stabilization and that the tibial and fibular lines, respectively the drill channels, did not deviate during the drilling and insertion of the SBS.
The standardized measurements of the parameters describing the anatomy were performed using the RadiAnt DICOM Viewer 2020.2.3 (Medixant, Poznań, Poland). The radiological measurements assessing the reduction result and the FNF were performed by two examiners. Previous studies have demonstrated an excellent level of intra- and inter-observer reliability for all parameters used [14,31].

Statistical Analysis

The statistical analysis was performed with SPSS software (version 25, Chicago, IL, USA). The Student’s t test, Mann–Whitney U test, or Kruskal–Wallis test was used to compare continuous variables between the study groups, depending on normal distribution and study size (Shapiro–Wilk test). Categorical variables were compared using Pearson’s chi-square test or Fisher’s exact test. p-values (p) of less than 0.05 were considered statistically significant. Pearson correlation coefficients (r) were used for correlation analysis. The interpretation of |r| was as follows: poor (r < 0.3), moderate (0.3 > r < 0.5), good (r > 0.50) [35].

3. Results

3.1. Patients Overview

The patients were, on average, 39 years old (range 18 to 68 years; SD ± 14 years). There was no difference between sexes (female N = 21, mean age 41 years, SD ± 15 years; male N = 23, mean age 39 years, SD ± 14 years; * p = 0.686).

3.2. Parameters Describing the Anatomy of the DTFJ

The mean depth of incisura (DI) on the native side was 3.9 mm (SD ± 1.2 mm), while on the injured side it was 3.8 mm (SD ± 1.3 mm). There was no difference between the two sides (p = 0.993). The mean engagement of the fibula on the native side into the incisura was 0.4 mm (SD ± 1.4 mm), while the Leporjärvi clear space (LCS) was 3.5 mm (SD ± 1.1 mm) and external rotation (NTDA) was 8 degrees (SD ± 5 degrees). The mean rotation of the incisura (ROI) on the native side was 96 degrees (SD ± 4 degrees), indicating that the sagittal incisura plane was on average 6 degrees (SD ± 4°) directed dorsally. Men have a larger DI than women [4.3 mm (SD ± 1.1 mm) vs. 3.3 mm (SD ± 1.2), p = 0.003]. LCS showed no sex differences [men 3.6 mm (SD ± 1.1 mm); women 3.4 mm (SD ± 1.2 mm), p = 0.378].
For the parameters DI, LCS, FE, and antTFD, there are inter-individual differences in excess of 4 mm. The complete results are listed in Table 2.
There was a positive correlation between depth of incisura (DI) and fibular engagement (FE), indicating that as the depth of the incisura increased, the fibula engaged deeper in the incisura (FE) (r = 0.662). With increasing fibula engagement, there tends to be a smaller clear space (r = −0.446). No correlation was seen between ROI and NTDA, FE, or LCS (|r| < 0.300). The complete results are listed in Table 3.

3.3. Correlation Between CT-Morphological Reduction Outcome Parameters and Incisura Parameters

On average, a slight diastasis (ΔLCS/ΔFE) of 0.6 mm/0.7 mm (SD ± 1.6 mm/0.9 mm), a slight dorsal translation (ΔantTFD) of 0.4 mm (SD ± 2.4 mm), and an external rotation (ΔNTDA) of 2 degrees (SD ± 4 degrees) tended to occur on the operative side without differences between the sexes (p > 0.05). Full results are shown in Table 2.
Patients with slight overtightening exhibited a smaller FE compared to patients with symmetrical reduction (p < 0.05) and to patients with slight diastasis (p = 0.047, Table 4). There was no difference between patients with slight diastasis and patients with symmetrical congruity (p = 0.336). No differences in DI, ROI, LCS, or NTDA were observed between patients with postoperative slight diastasis (ΔLCS > 1 mm) or overtightened (ΔLCS > −1 mm; p > 0.05, Table 4).
There was a moderate positive correlation between FE and ΔLCS (r = 0.334). This indicates that the deeper the fibula was anchored in the incisura, the less this anchoring was restored. Conversely, a wide LCS on the native side was associated with increasing overstressing at a moderate correlation level (r = −0.554; Table 5). There were no correlations observed between other parameters describing the anatomy (DI, ROI, and NTDA) and the CT-morphological outcome parameters of reduction (Table 5).

3.4. The Impact of Incisura Anatomy on the “Flexible Nature of Fixation”

The mean TO was 1.2 mm (SD, 1.4 mm), with no differences between sexes (p > 0.005; Table 2). There were no differences observed between patients with TO greater or less than 1 mm (p > 0.005; Table 4). Additionally, no correlation was found between the extent of FNF and the parameters describing the anatomy of DTFJ (r < 0.300; Table 5).

4. Discussion

The present analysis investigated the relationship between the anatomical properties and congruity of DTFJ after dynamic stabilization by suture button system (SBS) while operatively treating ankle fractures. It could be demonstrated that the individual incisura anatomy does not affect the CT-morphological reduction outcome in syndesmotic stabilization by means of SBS. Also, the degree of flexible nature of fixation (FNF) remained unaffected by individual anatomy.
Certain anatomical configurations of the DTFJ have been demonstrated to increase the risk of malreduction following syndesmotic screw (SYS) stabilization [15,16,18]. The present study did not confirm the findings of Boszcyk et al., which suggested that a deep incisura is more frequently associated with over-compression and a shallow incisura with anterior incongruence [34]. The relationship between the depth of the tibial incisura and the postoperative rotation of the fibula remains a topic of debate [6,7,36]. Cherney et al. observed a greater frequency of external rotation of the fibula with increasing depth [7]. Conversely, our findings align with those of Bosczyk, who was unable to demonstrate this relationship [7,34]. In comparison to the SYS, during SBS stabilization, an anterior rotation of the incisura was not confirmed as a morphologic risk factor for anterior incongruity [7,36,37]. Furthermore, a retroversion of the incisura was not associated with a posterior incongruity, while flexible stabilization. In the authors’ opinion, the so-called flexible nature of fixation may be a potential explanation for the lack of correlation between anatomy and CT-morphological reduction outcome. FNF describes small amplitude movements of the fibula that still allow self-centering within the incisura after stabilization (Figure 2b) [5,14,15]. Previous CT analyses have demonstrated that sagittal translation of the fibula towards the lowest point of the incisura occurs with greater frequency after SBS than after SYS [14]. The flexible nature of the suture button’s fixation has been demonstrated in CT analysis to result in a low malreduction rate [5,14]. In SYS stabilization there is no compensation by sagittal translation; therefore, it can be called a static stabilization [14,18,37].
Considering the presented results, the authors hypothesize that the extent of FNF is able to compensate for minor anatomical discrepancies that may occur during reduction due to the anatomical configuration [5,14]. This results in a lack of correlation between the rate of incongruity and the anatomy of the DTFJ.
As a result, the question was raised as to the extent to which anatomy affects the extent of sagittal translation of FNF. In the present analysis, no correlation was found between the extent of FNF during SBS stabilization (transverse offset; TO) and the parameters describing the anatomy of the DTFJ. It is therefore the authors’ opinion that stabilization of the DTFJ can be performed as a part of the treatment of unstable ankle fractures regardless of the anatomical configuration, provided that the bone anatomy is anatomically correct.
Furthermore, it has been confirmed that there are only minimal intra-individual but considerable interindividual differences in the appearance of the uninjured tibiofibular joint (DTFJ) of more than 2 mm [16,17,33,36]. A larger depth of incisura (DI) was found to be associated with a larger fibula engagement (FE). In the frontal plane, individuals who had undergone slight overtightening showed a smaller FE on the native side. There was no evidence to suggest that individual incisura anatomy affects the CT-morphological reduction outcome or the extent of flexible nature of fixation (FNF) after dynamic stabilization, as demonstrated by postoperative bilateral CT control.
The parameters describing the anatomy of the DTFJ vary by 4–8 mm for ATF, 6–13 mm for TFCS, and 13 mm for antTFD [6,16,17,18]. Given these variations and the fact that a lateral difference of >2 mm after surgery is considered a malreduction, bilateral CT is superior to plain radiography for assessing DTFJ postoperative congruity [2,11,12,19,20,21,22]. The findings of this study reinforce the recommendation that a unilateral CT scan is not a comprehensive assessment of postoperative congruity of the DTFJ. Based on the results and the literature, bilateral CT control was established as part of our postoperative routine following DTFJ stabilization in the treatment of ankle fractures [17]. In particular, the presence of a discrepancy between the anterior tibiofibular compression (ATF) and the tibiofibular compression stress (TFCS) of more than 2 mm in lateral comparison suggests that there may be a malreduction present, which potentially has a negative effect on the clinical outcome [2,3]. In our own treatment strategy, we recommend considering a revision of a syndesmotic malreduction for patients with a side difference of |ΔantTFD| and ΔLCS of more than 2 mm [2,3,12].
It should be noted that this study is not without limitations. In addition to the retrospective design and the heterogeneous patient group, the determination of the reduction was independent of the size of the patient 10 mm above the plafond. In order to facilitate a comparison of the results with those obtained following static stabilization, the study design was modified to align with the methodology described by Boszcyk et al. [6,34]. The present study does not assess the categorical quality of DTFJ reduction. Instead, the relationship between the anatomical properties and congruity of DTFJ after dynamic stabilization by SBS was analyzed [6]. The results of the study are also based on the assumption that the extremities are symmetrical, which is well documented by studies [17]. In order to account for inter-individual variability, further analyses could be conducted on the initial axial CT slice in which the first subchondral bone is visible [5]. Furthermore, the available studies employ disparate methodologies, necessitating the establishment of a consensus on the parameters to be considered. This is in accordance with the recommendations of Schon et al. [32] One possible approach is to determine these parameters in the first slice of the CT, where the subchondral bone of the tibia is visible. This is a topic for further investigation.
The parameters describing the anatomy were measured by one examiner (R.H.). Prior to this, a high level of reliability was demonstrated for the parameters used [6,14]. Two investigators (H.R. and C.F.) performed the radiological measurements of the reduction result and the FNF. High intra- and interrater reliability has also been demonstrated in previous publications [14].

5. Conclusions

The considerable inter-individual anatomical variability of the DTFJ was confirmed. The morphological configuration of the incisura has no impact on the immediate reduction result after dynamic stabilization of the DTFG, as determined by CT. The extent of FNF is also not affected by the morphology of the incisura. Stabilization of the DTFJ can be performed regardless of the anatomical configuration.

Author Contributions

Conceptualization: R.H., C.F., and A.B.A.-S.; methodology: R.H., C.F., and A.B.A.-S.; software: R.H. and A.B.A.-S.; validation, formal analysis, data curation: R.H., C.F., and F.S.; writing—original draft preparation: R.H. and A.B.A.-S.; writing—review and editing: F.S., H.J., and U.J.S.; supervision: C.K. All authors have read and agreed to the published version of the manuscript.

Funding

The authors received no financial support for the research, authorship, and/or publication of this article.

Institutional Review Board Statement

Approval of the local institutional review board for the study had been given on 16 August 2023 (Ethical Committee at the Medical Faculty, Leipzig University, AZ 488/19-ek) in view of the retrospective nature of the study, and all the procedures being performed were part of the routine care.

Informed Consent Statement

All patients provided written consent for the use of their anonymized data, including imaging, for analysis and publication as outlined in the general treatment contract. This has been approved by the Ethical Committee at the Medical Faculty, Leipzig University.

Data Availability Statement

The datasets used and/or analyzed during the current study are available from the corresponding author upon reasonable request.

Acknowledgments

The authors would like to thank the patients who participated in the study and the Department of Diagnostic and Interventional Radiology at Leipzig University Hospital for providing the imaging.

Conflicts of Interest

The authors declare no conflicts of interest with respect to the research, authorship, and/or publication of this article.

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Figure 1. Computed tomography in axial reconstruction of a native right ankle without signs of prior trauma or osteoarthritis 10 mm proximal to the plafond. Measurement of the parameters describing the anatomy and the reduction result shown on the uninjured tibial incisura. The intertubercular line (IL, A–B) was drawn between the anterior and posterior tubercle of the tibial fibular incisura (incisura). (a): Rotation of the incisura (ROI) is the measured angle between the center of the IL and the center of the tibia (C). Anterior tibiofibular distance (antTFD) is the distance between the tangent on the anterior plane of the tibia and the most anterior point of the fibula (E). (b): Depth of incisura (DI) is the distance between the IL and the deepest point of the incisura. Leporjärvi clear space (LCS, pointed arrow) is the distance between the most medial point of the fibula (---) and the deepest point of the incisura. Fibula engagement (FE) is the distance between the IL and the most medial point of the fibula (---).
Figure 1. Computed tomography in axial reconstruction of a native right ankle without signs of prior trauma or osteoarthritis 10 mm proximal to the plafond. Measurement of the parameters describing the anatomy and the reduction result shown on the uninjured tibial incisura. The intertubercular line (IL, A–B) was drawn between the anterior and posterior tubercle of the tibial fibular incisura (incisura). (a): Rotation of the incisura (ROI) is the measured angle between the center of the IL and the center of the tibia (C). Anterior tibiofibular distance (antTFD) is the distance between the tangent on the anterior plane of the tibia and the most anterior point of the fibula (E). (b): Depth of incisura (DI) is the distance between the IL and the deepest point of the incisura. Leporjärvi clear space (LCS, pointed arrow) is the distance between the most medial point of the fibula (---) and the deepest point of the incisura. Fibula engagement (FE) is the distance between the IL and the most medial point of the fibula (---).
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Figure 2. Computed tomography in axial reconstruction of a left ankle fracture (AO 44B3.1) after open reduction and internal fixation of the lateral malleolus (lag screw and neutralization plate) and dynamic stabilization of the distal tibiofibular joint with the suture button system (TightRope®, Arthrex, Naples, FL, USA); lateral endobutton and medial flip anchor. Stitched arrow = still visible fracture gap; dotted arrow = plate and suture button. (a): parameters assessing the reduction quality; A–B anterior tibiofibular distance (antTFD) and C–D Leporjärvi clear space (LCS). (b): The tibial line (A–B) and fibula line (C–D) represent the drill channel, assuming that they lie on the exact centerline during drilling after reduction and temporary fixation for SBS [16]. The distance of the tibial and fibular line represents the transversal offset (E–F, TO), the spontaneous translation of the fibula within the incisura after SBS stabilization.
Figure 2. Computed tomography in axial reconstruction of a left ankle fracture (AO 44B3.1) after open reduction and internal fixation of the lateral malleolus (lag screw and neutralization plate) and dynamic stabilization of the distal tibiofibular joint with the suture button system (TightRope®, Arthrex, Naples, FL, USA); lateral endobutton and medial flip anchor. Stitched arrow = still visible fracture gap; dotted arrow = plate and suture button. (a): parameters assessing the reduction quality; A–B anterior tibiofibular distance (antTFD) and C–D Leporjärvi clear space (LCS). (b): The tibial line (A–B) and fibula line (C–D) represent the drill channel, assuming that they lie on the exact centerline during drilling after reduction and temporary fixation for SBS [16]. The distance of the tibial and fibular line represents the transversal offset (E–F, TO), the spontaneous translation of the fibula within the incisura after SBS stabilization.
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Table 1. Inclusion and exclusion criteria, AO “Arbeitsgruppe für Osteosynthesefragen”, DTFJ distal tibiofibular joint, CT computed tomography, and SBS suture button system.
Table 1. Inclusion and exclusion criteria, AO “Arbeitsgruppe für Osteosynthesefragen”, DTFJ distal tibiofibular joint, CT computed tomography, and SBS suture button system.
Inclusion CriteriaExclusion Criteria
  • AO 44 B or 44 C fracture with instability of the DTFJ
  • stabilization of DTFJ by suture button system
  • postoperative bilateral CT control
  • slice thickness of ≤ 1 mm in CT unilateral stabilization of the syndesmosis with SBS
  • anatomical reduction of the fractures
  • anatomical configuration of the distal anterior (Tillaux-Chaput) and posterior (Volkmann) tibial tubercle
  • anatomical configuration of anteromedial distal fibula (Wagstaffe–Le Fort)
  • fractured ankle joint without history of pre-treatment
  • a non-fractured contralateral ankle without signs of previous pathologies in postoperative bilateral CT control
  • age < 18 years
  • bilateral ankle and/or syndesmosis lesion
  • pathologies of the uninjured ankle
  • non-anatomic reduction of the fractures with bone steps > 2 mm.
  • intraoperative CT control
  • preoperative known osteoporosis
Table 2. Parameters describing the anatomy of the native distal tibiofibular joint. Overview of ΔLCS, ΔantTFD, and ΔNTDA characterizing the CT-morphological reduction outcome; all parameters are presented in mean (SD), 1 U test.
Table 2. Parameters describing the anatomy of the native distal tibiofibular joint. Overview of ΔLCS, ΔantTFD, and ΔNTDA characterizing the CT-morphological reduction outcome; all parameters are presented in mean (SD), 1 U test.
Parameter Assessing DTFJAll N = 44Range
Min–Max		Female
N = 21		Male
N = 23		p
DI in mm (SD)3.8 (1.2)1.3–7.23.3 (1.2)4.3 (1.1)0.003 1
LCS in mm (SD)3.5 (1.1)1.2–5.83.4 (1.2)3.6 (1.1)0.378 1
FE in mm (SD)0.4 (1.4)−2.6–3.60.1 (1.3)0.7 (1.4)0.196 1
ROI in degrees (SD)96 (4)85–10996 (4)96 (4)0.878 1
NTDA in degrees (SD)8 (5)−2–188 (6)8 (4)0.672 1
antTFD in mm (SD)11.2 (2.8)4.4–18.710.8 (2.2)11.7 (3.3)0.244 1
Parameter assessing the CT-morphological reduction outcome
ΔLCS in mm (SD)0.7 (1.5)−2.7–5.50.7 (1.9)0.7 (1.1)0.622 1
ΔantTFD in mm (SD)0.4 (2.4)−4.1–9.00.2 (2.3)0.6 (2.8)0.689 1
ΔNTDA in degrees (SD)2 (1.4)−11–92 (4)1 (3)0.300 1
TO in mm (SD)1.2 (1.4)−2.88–5.71.4 (1.0)0.9 (1.8)0.118 1
Table 3. Pearsons’s correlation coefficients (r) between the parameters of interest of the native side as well as age at computed tomography. Incisura depth (ID); rotation of incisura (ROI); fibula engagement (FE); Leporjärvi clear space (LCS); Nault talar dome angle (NTDA).
Table 3. Pearsons’s correlation coefficients (r) between the parameters of interest of the native side as well as age at computed tomography. Incisura depth (ID); rotation of incisura (ROI); fibula engagement (FE); Leporjärvi clear space (LCS); Nault talar dome angle (NTDA).
Native SideIDROIFELCSNTDA
DI −0.1970.6620.2180.159
ROI−0.197 −0.232−0.0810.090
FE0.662−0.232 −0.4660.379
age0.128−0.0730.401−0.4440.128
Table 4. Relationship of CT-morphological reduction outcome |ΔLCS| 1 mm, |ΔantTFD| 1 mm, and |ΔNTDA| five degrees, and |ΔFE| 1 mm to the incisura parameters: incisura depth (ID), rotation of incisura (ROI), fibula engagement (FE), Nault talar dome angle (NTDA), and Leporjärvi clear space (LCS). Values are presented as mean and standard deviation (SD); differences were analyzed between Δ* and 1 Mann–Whitney U test. Asterisk (*): These parameters were compared statistically.
Table 4. Relationship of CT-morphological reduction outcome |ΔLCS| 1 mm, |ΔantTFD| 1 mm, and |ΔNTDA| five degrees, and |ΔFE| 1 mm to the incisura parameters: incisura depth (ID), rotation of incisura (ROI), fibula engagement (FE), Nault talar dome angle (NTDA), and Leporjärvi clear space (LCS). Values are presented as mean and standard deviation (SD); differences were analyzed between Δ* and 1 Mann–Whitney U test. Asterisk (*): These parameters were compared statistically.
CongruityNDI in mmROI in DegreesFE in mmNTDA in DegreeLCS in mm
|ΔLCS|
in mm		<−1 mm *N = 83.4 (1.1)97 (5)0.1 (1.0)6 (4)3.9 (1.7)
anaN = 213.7 (1.2)96 (4)0.9 (1.4)8 (5)3.6 (1.0)
>1 mm *N = 154.2 (1.4)96 (4)1.1(1.4)8 (4)3.1 (1.0)
p 0.149 10.681 10.047 10.686 10.238 1
|ΔantTFD|
in mm		<−1 mm *N = 143.4 (1.3)95 (4)0.5 (0.8)7 (5)3.2 (1.4)
AnaN = 103.9 (1.3)98 (5)0.2 (1.8)8 (5)3.7 (1.1)
>1 mm *N = 204.0 (1.2)95 (4)0.4 (1.5)9 (5)3.5 (1.0)
p 0.35910.691 10.743 10.5450.522
|ΔNTDA|
in degree		<−5° *N = 34 (1)95° (9)1.0 (0.5)10 (8)3.2 (1.0)
AnaN = 394 (1)96° (4)0.4 (1.4)8 (5)3.5 (1.2)
>5° * N = 124 (1)95° (4)0.4 (1.5)7 (5)3.5 (1.1)
P 0.852 10.404 10.617 10.741 10.896 1
|TO|
In mm		<1 mm *N = 253.7 (1.2)95 (2)0.4 (1.5)7 (5)3.3 (1.0)
>1 mm *N = 203.9 (1.296 (6)0.4 (1.3)9 (4)3.8 (1.2)
P 0.465 10.568 10.781 10.146 10.121 1
Table 5. Correlations of parameters describing the CT-morphological reduction outcome (Δ = side-to-side differences) and parameters describing the anatomy of the distal tibiofibular joint: Leporjärvi clear space (LCS), Nault talar dome angle (NTDA), and anterior tibiofibular distance (antTFD) with incisura depth (ID), rotation of incisura (ROI), and fibula engagement (FE) of the native side.
Table 5. Correlations of parameters describing the CT-morphological reduction outcome (Δ = side-to-side differences) and parameters describing the anatomy of the distal tibiofibular joint: Leporjärvi clear space (LCS), Nault talar dome angle (NTDA), and anterior tibiofibular distance (antTFD) with incisura depth (ID), rotation of incisura (ROI), and fibula engagement (FE) of the native side.
Parameters of Native IncisuraParameters Assessing the Quality of Reduction of the DTFJ
ΔLCSΔNTDAΔantTFDTO
DI0.058−0.0870.024−0.141
ROI−0.231−0.064−0.018−0.015
FE0.334−0.109−0.112−0.110
LCS−0.5540.1010.001−0.052
NTDA0.254−0.3620.024−0.122
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Hennings, R.; Fuchs, C.; Souleiman, F.; Jeanette, H.; Spiegl, U.J.; Kleber, C.; Ahrberg-Spiegl, A.B. Impact of Distal Tibiofibular Joint Anatomy on Reduction Outcome in Dynamic Suture Button Stabilization of the Distal Syndesmosis—A CT Analysis. Trauma Care 2025, 5, 10. https://doi.org/10.3390/traumacare5020010

AMA Style

Hennings R, Fuchs C, Souleiman F, Jeanette H, Spiegl UJ, Kleber C, Ahrberg-Spiegl AB. Impact of Distal Tibiofibular Joint Anatomy on Reduction Outcome in Dynamic Suture Button Stabilization of the Distal Syndesmosis—A CT Analysis. Trauma Care. 2025; 5(2):10. https://doi.org/10.3390/traumacare5020010

Chicago/Turabian Style

Hennings, Robert, Carolin Fuchs, Firas Souleiman, Henkelmann Jeanette, Ullrich Joseph Spiegl, Christian Kleber, and Annette B. Ahrberg-Spiegl. 2025. "Impact of Distal Tibiofibular Joint Anatomy on Reduction Outcome in Dynamic Suture Button Stabilization of the Distal Syndesmosis—A CT Analysis" Trauma Care 5, no. 2: 10. https://doi.org/10.3390/traumacare5020010

APA Style

Hennings, R., Fuchs, C., Souleiman, F., Jeanette, H., Spiegl, U. J., Kleber, C., & Ahrberg-Spiegl, A. B. (2025). Impact of Distal Tibiofibular Joint Anatomy on Reduction Outcome in Dynamic Suture Button Stabilization of the Distal Syndesmosis—A CT Analysis. Trauma Care, 5(2), 10. https://doi.org/10.3390/traumacare5020010

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