Exploratory Analysis of Subtle Ankle Malpositioning on Sagittal Tibiofibular Alignment: Implications for Assessing Syndesmotic Malreduction.

Abstract

Background: Accurate radiographic assessment of syndesmotic alignment is critical in the management of ankle injuries. Given limitations in traditional radiographic parameters, sagittal tibiofibular relationship (STFR) has been increasingly utilized. However, subtle variations in lower-limb rotation during imaging may alter STFR measurements, potentially leading to misinterpretation. This cadaveric study investigates the effect of ankle positioning on STFR in a cadaver model with intact syndesmotic ligaments.

Methods: Twelve knee-disarticulated cadaver lower limbs with intact syndesmotic ligaments were used. True lateral fluoroscopic images were obtained using the talar dome double-shadow superimposition method, followed by incremental internal rotation (IR), external rotation (ER), abduction (ABD), and adduction (ADD) to simulate minor positional changes. Two foot and ankle fellowship-trained orthopaedic surgeons confirmed image acceptability. STFR was measured using the anterior tibiofibular interval (ATFI), posterior tibiofibular interval (PTFI), tibial/fibular width ratio (TW/FW), and anterior-posterior tibial-fibular distances (AF-AT, PF-PT). Pearson correlation analysis assessed associations between positioning and each measurement.

Results: All STFR measurements were significantly correlated with axial plane rotation (P < .001) demonstrating that slight rotational malalignment in limb positioning was associated with apparent changes in tibiofibular alignment. Inter-rater reliability ranged from 0.75 to 0.95 and intrarater reliability from 0.63 to 0.98. ABD/ADD variation showed no significant effect on STFR measurements (all P > .05).

Conclusion: Although increasing in utilization to assess syndesmotic alignment, STFR is sensitive to minor rotational deviations in the axial plane. Awareness of this limitation should be considered to avoid misinterpretation of syndesmotic reduction during intraoperative or postoperative imaging.

Clinical relevance: Radiographic assessment of syndesmotic alignment is important for guiding intraoperative reduction and postoperative evaluation in ankle injuries. This study suggested that STFR could be relatively sensitive to minor rotational limb malpositioning, which alter apparent tibiofibular positioning. These findings caution that small rotational deviations may significantly change STFR measurements and may lead to misinterpretation of syndesmotic reduction.