Weightbearing Radiography and MRI Findings in Ankle Fractures.

Background. Static weightbearing radiography can be used to assess stability in ankle fractures by measuring lateral talar shift (medial clear space; MCS). However, the correlation of a stable ankle joint under weightbearing load and the structural integrity of the deltoid ligament has not been shown. In this study, we assessed deltoid ligament integrity on magnetic resonance imaging (MRI) and correlated that with weightbearing and gravity stress test radiography. Methods. Thirty-four patients with supination external rotation II-IV (SER) fractures underwent MRI, weightbearing radiography, and gravity stress test. On MRI, the deep anterior and posterior tibiotalar deltoid, tibionavicular and tibiocalcaneal ligaments, as well as the syndesmosis were assessed as intact, partial rupture, or complete rupture. The MCS was measured as the distance between the lateral border of the medial malleolus and the medial border of the talus at the level of the talar dome on the mortise view. Results. Twenty-three patients suffered a deep anterior tibiotalar ligament rupture (16 partial; 7 complete) and 2 a deep posterior tibiotalar ligament tear (1 partial; 1 complete). For MCS on weightbearing radiography, no statistically significant differences were identified between any of the individual groups. With gravity stress radiography, only a complete tear of the tibiocalcaneal ligament showed a significantly higher MCS than a partial tear or intact tibiocalcaneal ligament (P < .005). No other ligament disruption showed a significant difference between the complete rupture versus intact or partial tear. Conclusion. Weightbearing radiography does not show much variation in terms of MCS even with ligamentous disruption and fibula fracture. The talus often centers itself underneath the tibia with weightbearing radiography.Levels of Evidence: Level III: Retrospective cohort study.

Patient-Specific 3-D Magnetic Resonance Imaging-Based Dynamic Simulation of Hip Impingement and Range of Motion Can Replace 3-D Computed Tomography-Based Simulation for Patients With Femoroacetabular Impingement: Implications for Planning Open Hip Preservation Surgery and Hip Arthroscopy.

BACKGROUND: Femoroacetabular impingement (FAI) is a complex 3-dimensional (3D) hip abnormality that can cause hip pain and osteoarthritis in young and active patients of childbearing age. Imaging is static and based on 2-dimensional radiographs or computed tomography (CT) scans. Recently, CT-based 3D impingement simulation was introduced for patient-specific assessments of hip deformities, whereas magnetic resonance imaging (MRI) offers a radiation-free alternative for surgical planning before hip arthroscopic surgery. PURPOSE: To (1) investigate the difference between 3D models of the hip, (2) correlate the location of hip impingement and range of motion (ROM), and (3) correlate diagnostic parameters while comparing CT- and MRI-based osseous 3D models of the hip in symptomatic patients with FAI. STUDY DESIGN: Cohort study (Diagnosis); Level of evidence, 2. METHODS: The authors performed an institutional review board-approved comparative and retrospective study of 31 hips in 26 symptomatic patients with FAI. We compared CT- and MRI-based osseous 3D models of the hip in the same patients. 3D CT scans (slice thickness, 1 mm) of the entire pelvis and the distal femoral condyles were obtained. Preoperative MRI of the hip was performed including an axial-oblique T1 VIBE sequence (slice thickness, 1 mm) and 2 axial anisotropic (1.2 × 1.2 × 1 mm) T1 VIBE Dixon sequences of the entire pelvis and the distal femoral condyles. Threshold-based semiautomatic reconstruction of 3D models was performed using commercial software. CT- and MRI-based 3D models were compared with specifically developed software. RESULTS: (1) The difference between MRI- and CT-based 3D models was less than 1 mm for the proximal femur and the acetabulum (median surface distance, 0.4 ± 0.1 mm and 0.4 ± 0.2 mm, respectively). (2) The correlation for ROM values was excellent (r = 0.99, P < .001) between CT and MRI. The mean absolute difference for flexion and extension was 1.9°± 1.5° and 2.6°± 1.9°, respectively. The location of impingement did not differ between CT- and MRI-based 3D ROM analysis in all 12 of 12 acetabular and 11 of 12 femoral clock-face positions. (3) The correlation for 6 diagnostic parameters was excellent (r = 0.98, P < .001) between CT and MRI. The mean absolute difference for inclination and anteversion was 2.0°± 1.8° and 1.0°± 0.8°, respectively. CONCLUSION: Patient-specific and radiation-free MRI-based dynamic 3D simulation of hip impingement and ROM can replace CT-based 3D simulation for patients with FAI of childbearing age. On the basis of these excellent results, we intend to change our clinical practice, and we will use MRI-based 3D models for future clinical practice instead of CT-based 3D models. This allows radiation-free and patient-specific preoperative 3D impingement simulation for surgical planning and simulation of open hip preservation surgery and hip arthroscopic surgery.