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

Background: To compare the accuracy of arthroscopic sagittal versus coronal plane distal tibiofibular motion toward diagnosing syndesmotic instability. Methods: Arthroscopic assessment of the syndesmosis was performed on 21 above-knee cadaveric specimens, first with all ligaments intact and subsequently with sequential transection of the anterior inferior tibiofibular ligament, the interosseous ligament, the posterior inferior tibiofibular ligament, and the deltoid ligament. A lateral hook test, an anterior-to-posterior (AP) translation test, and a posterior-to-anterior (PA) translation test were performed under 100 N of applied force. Anterior and posterior third coronal plane diastasis and AP and PA sagittal plane fibular translations were measured relative to the static tibia. Results: Receiver operating characteristic (ROC) curve analysis revealed that the area under the curve (AUC) was higher for the combined AP and PA sagittal measurements (AUC, 0.91; accuracy, 83.5%; sensitivity, 78%; specificity, 89%) than the coronal plane measurements (anterior third: AUC, 0.65; accuracy, 60.5%; sensitivity, 63%; specificity, 59%; posterior third: AUC, 0.73; accuracy, 68.5%; sensitivity, 80%; specificity, 57%) ( P < .001), underscoring the higher accuracy of sagittal plane measurements. Conclusion: Arthroscopic measurement of sagittal plane fibular translation is more accurate than coronal plane diastasis for evaluating syndesmotic instability. Clinical Relevance: Clinicians should focus on distal tibiofibular motion in the sagittal plane when arthroscopically evaluating suspected syndesmotic instability. Level of Evidence: Biomechanical cadaveric study.

Category: Midfoot/Forefoot; Sports; Trauma Introduction/Purpose: Early detection of Lisfranc instability is critical for optimizing clinical outcomes. Injuries causing a more subtle instability, however, can be difficult to diagnose. The aim of this study was to compare the injured Lisfranc joint to the healthy contralateral side using weightbearing computed tomography (CT) in patients with known Lisfranc instability. We also aimed to define the range of normal measurement variation by comparing the Lisfranc joint measurements between the left and right foot in individuals without foot injury who underwent similar imaging. Our hypothesis was that compared to the healthy contralateral side, weightbearing CT area and volume measurements were increased in patients diagnosed with subtle Lisfranc instability. Methods: Patients with unilateral Lisfranc instability requiring operative fixation (n = 14) underwent preoperative bilateral foot and ankle weightbearing CT. A separate group of patients without foot injury who also underwent similar imaging were included as comparative controls (n = 36). For each weightbearing CT, 2 dimensional axial and coronal plane Lisfranc joint parameters, Lisfranc area, intercuneiform area, C1-M2 distance, C1-C2 distance, M1-M2 distance, first and second tarsometatarsal (TMT 1 and 2) alignment; and first and second tarsometatarsal (TMT 1and 2) dorsal step off were measured to evaluate the Lisfranc anatomy at a level 10 mm below the dorsal surface of medial cuneiform (Figures I and II). In addition, the volume of the Lisfranc joint was also evaluated. Values were recorded by two independent observers to assess interobserver reliability. Results: Among those with unilateral Lisfranc instability, values differed largely between the injured and the healthy contralateral side for all measurements performed (p-value range, 0.008 - <0.001). In the control population without foot injury, no differences were identified between any of the bilateral measurements (p-value range, 0.121 - 0.984). Conclusion: Weightbearing CT can effectively differentiate Lisfranc instability from those without instability. The Lisfranc volume and area had the largest difference between the injured and the uninjured feet among surgically treated patients with substantial interrater agreement making them the most relevant parameters for detecting Lisfranc instability. However, prospective studies are needed to validate the role of weightbearing CT in the diagnosis of subtle Lisfranc instability.

Category: Ankle; Trauma Introduction/Purpose: Diagnosis of destabilizing deltoid ligament injuries remains challenging and is best identified with dynamic imaging techniques. This study aims to assess and compare medial clear space (MCS) distances in various stages of sequentially created supination external rotation (SER) ankle injury model using portable ultrasound (P-US) and fluoroscopy. We hypothesize that there is a strong correlation between the P-US and fluoroscopic measurements for the assessment of medial ankle instability in SER type ankle injury during the gravity stress test (GST), weight-bearing, or external rotation stress test. Methods: Ten cadaveric specimens were used for assessing medial ankle instability. The assessment was performed with all structures intact, and later with sequential transection of the anterior inferior tibiofibular ligament (Stage I), fibular (Weber-B fracture) (Stage II), posterior inferior tibiofibular ligament (Stage III), superficial deltoid ligament (Stage IVa), and deep deltoid ligament (Stage IVb). In all scenarios, the GST, external rotation stress test(45N), and Simulated weight-bearing condition(750N) were performed. The P-US measurement of the MCS was assessed at the anteromedial and inferomedial aspect of the ankle joint. Three different MCS distances were measured, as demonstrated in Figure 1. The fluoroscopic MCS measurements were assessed on a true mortise ankle view achieved during each loading condition. Spearman rank correlation was used to investigate the relationship between the P-US and fluoroscopic measurements. The inter- and intra-observer agreement was assessed using the intraclass correlation coefficient (ICC) through a two-way mixed-effects model with absolute agreement. Results: The P-US and fluoroscopic assessed medial ankle instability values during the GST, weight-bearing, and the external rotation stress test increased as the SER ankle injury stage progressed. The P-US values measured during all stress tests demonstrated a moderate to strong positive correlation with those measured with the fluoroscopy (Spearman's rank correlation ranged from 0.61-0.93, p-values <0.001). Inter-rater (P-US: 0.97, 95%CI: 0.96-0.98) and intra-rater reliability (P-US, 0.95, 95%CI: 0.94-0.96) for the P-US measurements were all substantial. Conclusion: The use of dynamic P-US to measure the MCS appears to be a reliable and repeatable technique. The P-US MCS measurement values measured in the SER ankle injury model during the GST, weight-bearing and the external rotation stress test are well correlated with those values measured with fluoroscopy. Therefore, the dynamic P-US with stress examination of the ankle has the potential to quantify medial ankle instability in a radiation-free, non-invasive, low cost, and point of care setting.