"Flexible nature of fixation" in syndesmotic stabilization of the inferior tibiofibular joint affects the radiological reduction outcome.

PURPOSE: Fibular mobility after suture button stabilization (SBS) of inferior tibiofibular joint (syndesmosis) injuries has been described. This effect is called the "flexible nature of fixation (FNF)." In this study, we aimed to quantify FNF in syndesmotic stabilization. METHODS: Postoperative bilateral computed tomography (CT) of ankle fractures with syndesmosis stabilization by SBS or syndesmotic screw (SYS) was retrospectively analyzed. The transverse offset (TO) and vertical offset (VO) were defined by evaluating the drill channels. The reduction outcome was evaluated by the side-to-side difference between the clear space and the anterior tibiofibular distance (antTFD). The calculated anterior tibiofibular distance (cal-antTFD) was calculated by subtracting the TO from the validated antTFD. Subsequently, a reevaluation of the reduction outcomes after SYS or SBS stabilization was performed using cal-antTFD. RESULTS: Sixty patients (44 with SBS and 16 with SYS stabilization) were analyzed. The intra-rater and inter-rater reliabilities for TO and VO were excellent (α > 0.92). SYS stabilization showed lower mean TO (- 0.02 mm; SD 0.14) and VO (0.11 mm; SD, 0.29 mm) than SBS stabilization (TO 1.16 mm, SD 1.4 mm; VO 0.2 mm, SD 0.8 mm; p = 0.001). The rate of malreduction according to cal-antTFD was higher than that of antFTD (p = 0.033). CONCLUSION: The presented method, which evaluates the position of the tibial to the fibular drill channel, allowed the quantification of the "FNF." The often described difference in the dynamic stabilization of SBS compared to the rigid stabilization by SYS could be objectified. Considering cal-antTFD illustrates that FNF potentially reduces the rate of malreduction in SBS stabilization.

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.

Does the orientation of syndesmosis fixative device affect the immediate reduction of the distal tibiofibular joint?

INTRODUCTION: Incongruent stabilization of the distal tibiofibular joint (syndesmosis) results in poorer long-term outcome in malleolar fractures. The aim was to analyze whether the orientation of the syndesmotic stabilization would affect the immediate reduction imaged in computed tomography (CT). MATERIALS AND METHODS: The syndesmotic congruity in 114 ankle fractures with stabilization of the syndesmosis were retrospectively analyzed in the post-operative bilateral CT scans. The incisura device angle (IDA) was defined and correlated with the side-to-side difference of Leporjärvi clear-space (ΔLCS), anterior tibiofibular distance (ΔantTFD) and Nault talar dome angle (ΔNTDA) regardless of the stabilization technique and separately for suture button system and syndesmotic screw. Asymmetric reduction was defined as ΔLCS > 2 mm and |ΔantTFD|> 2 mm. RESULTS: Regardless of the stabilization technique, no correlation between the IDA and the ΔLCS (r = 0.069), the ΔantTFD (r = 0.019) nor the ΔNTDA (r = 0.177) could be observed. There were no differences between suture button system and syndesmotic screw. Asymmetrical reduction was detected in 46% of the cases, while sagittal asymmetry was most common. No association was found between the orientation of stabilization device and occurrence of asymmetrical reduction (p > 0.05). The results of suture button system and syndesmotic screw were comparable in this respect (p > 0.05). CONCLUSION: Poor correlation between the orientation of the stabilization device and the immediate post-operative congruity of the syndesmosis could be shown. In contrast to current literature, this study did not show difference of suture button system over syndesmotic screw in this regard. Careful adjustment of the fibula in anteroposterior orientation should be given special attention.

Suture button versus syndesmotic screw in ankle fractures - evaluation with 3D imaging-based measurements.

BACKGROUND: Inadequate reduction of syndesmotic injuries can result in disabling clinical outcomes. The aim of the study was to compare syndesmosis congruity after fixation by syndesmotic screws (SYS) or a suture button system (SBS) using three-dimensional (3D) computed imaging techniques. METHODS: In a retrospective single-center study, patients with unilateral stabilization of an ankle fracture with a syndesmotic injury and post-operative bilateral CT scans were analyzed using a recently established 3D method. The side-to-side differences were compared for tibio-fibular clear space (∆CS), translation angle (∆α), and vertical offset (∆z) among patients stabilized with syndesmotic screws or suture button system. Syndesmotic malreduction was defined for ∆CS > 2 mm and for |∆α| > 5°. ∆CS and ∆α were correlated with two-dimensional (2D) measurements. RESULTS: Eighteen patients stabilized with a syndesmosis screw and 29 stabilized with a suture button system were analyzed. After stabilization, both groups revealed mild diastasis (SYS: mean ∆CS 0.3 mm, SD 1.1 mm vs SBS: mean ∆CS 0.2 mm, SD 1.2 mm, p = 0.710). In addition, both stabilization methods showed slight dorsalization of the fibula (SYS: mean ∆α 0.5°, SD 4.6° vs SBS: mean ∆α 2.1°, SD 3.7°, p = 0.192). Also, restoration of the fibula-to-tibia length ratio also did not differ between the two groups (SYS: mean Δz of 0.5 mm, SD 2.4 mm vs SBS: mean Δz of 0 mm, SD 1.2 mm; p = 0.477). Malreduction according to high ∆α was most common (26% of cases), with equal distribution between the groups (p = 0.234). ∆CS and ∆α showed good correlation with 2D measurements (ρ = 0.567; ρ = 0.671). CONCLUSION: This in vivo analysis of post-operative 3D models showed no differences in immediate post-operative alignment after syndesmotic screws or suture button system. Special attention should be paid to syndesmotic malreduction in the sagittal orientation of the fibula in relation to the tibia in radiological control of the syndesmotic congruity as well as intra-operatively.

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 AO triangular external fixator: a backup option in the treatment of ankle fractures in geriatric patients?

PURPOSE: To analyze the indications, radiological short-term outcomes, and complications of ankle fractures in geriatric patients treated with a triangular external fixator (AEF) until fracture healing. Furthermore, the effect of an additional osteosynthesis to AEF on the radiological outcome was investigated. METHODS: Retrospective analysis of ankle fractures treated in a Level I Trauma Center between 2005 and 2015 with an AEF in patients aged ≥ 65 years until fracture has healed. The combination of AEF and at least one additional osteosynthesis of a malleolus was defined as hybrid external fixator (HEF). At the time of AEF removal, a preserved ankle joint congruity was defined as good radiological outcome. Incongruity more than 2 mm was defined as poor radiologic results. RESULTS: 16 patients (13 women, 3 men) with a mean age of 74 years (SD 6.2) were treated with AEF until fracture healing, 9 with a single AEF and 7 with a HEF. Stabilization with HEF (n = 7 [100%]) showed higher rates of good radiological outcome than AEF alone (n = 4 [44%] of 9; p = 0.034). The duration of therapy did not differ between HEF and AEF (70 day vs 77 days). 4 patients (22%) required surgical revision. CONCLUSION: It could be shown that osteosynthesis in addition to AEF leads to a better radiological short-term results than using AEF alone. Therefore, in the situation where an AEF is considered as the definitive treatment option for an ankle fracture in geriatric patients with expected or existing soft tissue problems, it should be done or completed as a HEF. LEVEL OF EVIDENCE: Therapeutic level IV.

Validation of a new method for evaluation of syndesmotic injuries of the ankle.

PURPOSE: To define a new parameter in CT that could make imaging of the contralateral ankle dispensable evaluating the position of the fibula after syndesmotic injury. METHODS: Thirty bilateral CTs of 30 patients were included. Five parameters were defined in axial CT for the injured (_inju) and uninjured (_unin) ankle. Reproducibility was examined for inter-observer and intra-observer reliability. Comparisons for all parameters were performed between the CT scans of both ankles. RESULTS: All measurements had a high agreement for the inter-observer and intra-observer correlation coefficients. A large interindividual variance could be found between all parameters. If the difference of the anterior tibiofibular distance antTFD_unin and antTFD_inju was less than 2 mm, there was a strong significant pairwise correlation between all parameters between both sides. CONCLUSION: Bilateral CT is still to be recommended, as it is the only way to exactly assess anterior posterior reduction of the fibula.

Os calcaneus secundarius, a relevant differential diagnosis to fracture or pseudarthrosis of processus anterior of the calcaneus: a CT morphologic description.

PURPOSE: A fracture or a pseudarthrosis of the processus anterior calcanei (PAC) as well as a traumatized Os calcaneus secundarius (OCS) is often overlooked. A clinical or conventional radiological differentiation of these is uncertain. Therefore, a CT scan is recommended. The aim of the study was to identify CT morphological differentiators between OCS and pathologies of PAC. METHODS: All CT scans at our trauma center level I from 2010 to 2014, which imaged the entire foot, performed after acute trauma or postoperative control were retrospectively re-examined for OCS, other accessory ossicles (oAOS), fracture or pseudarthrosis of PAC and analyzed for specifiers. RESULTS: In 611 CT examinations, 14 (2.3%) accessory ossicles (AOS) at the PAC were detected. 12 (86%) were identified as typical OCS and 2 (14%) as oAOS. 56 (9.2%) pathologies were detected. Of these, 44 (79%) were declared as fractures and 12 (21%) as pseudarthrosis. 7 OCS (58%) and 25 (46%) of the pathologies were not mentioned in the initial CT reports. The main differentiators of OCS to fracture of PAC were the anteromedial localization into a concave notch at the calcaneal facet at PAC and the continuous corticalization. With increasing size, radiological osteoarthritic signs at the OCS were frequent (p ≤ 0.05). CONCLUSIONS: The study confirms that AOS or pathologies at the PAC often are not exactly described in CT report. In the context of foot trauma, attention should be paid to this region. Based on the presented differentiation criteria, a precise distinction can be made with the help of a CT.