Influence of bone morphology and injured ligament of the ankle on ankle stress radiographs

Transcription

1 Influence of bone morphology and injured ligament of the ankle on ankle stress radiographs Gye Wang Lee, MD, Chin Youb Chung, MD, Moon Seok Park, MD Seung Yeol Lee, MD, Myung Ki Chung, MD, Byung Chae Jo, MD, Dong Yeon Lee, MD Kyoung Min Lee, MD Department of Orthopaedic Surgery Seoul National University Bundang Hospital, South Korea

2 The authors have no disclosures.

3 Introduction Both MRI and ankle stress radiographs are generally performed for the preoperative evaluation of ankle instability. Although ankle stress radiographs are widely used in patients with lateral ankle instability, potential factors affecting their results may be overlooked.

4 Purpose To investigate the influence of bone morphology and injured ligament of the ankle on ankle stress radiographs in patients with lateral ankle instability.

5 Materials and Methods IRB approved retrospective study Inclusion - Patients at least 20 years old who underwent ankle MRI and stress X-ray Exclusion - acute pain following less than 6 weeks of ankle injury - inadequately taken X ray - abnormal anatomy Data collection - Demographic data (age, gender) - MRI evaluation qualitative evaluation of ligaments (ATFL, CFL, PTFL, Deltoid lig), effusion - Stress radiographs (talar tilt, anterior displacement of talus)

6 Ankle AP & lateral X-rays DTAS angle, the angle between the DTAS and the longitudinal axis of the tibia BT, the angle between the longitudinal axis of the tibia and a line connecting the tips of the lateral and medial malleoli MMRL (or LMRL), the ratio of the length of the medial (or lateral) malleolus to the width of the talar dome MMSA, the line parallel to the medial malleolar articular surface and DTAS. AI, the angle between the longitudinal axis of the tibia and the anterior and posterior margins of the tibial plafond FP, the relative position of the fibular center on a line between the anterior and posterior margins of the tibial plafond (d/e)

7 Talar tilt & Anterior drawer test Talar tilt angle on AP ankle X ray while exerting varus stress 15 decanewton using Telometer device Anterior displacement of talus on Lat ankle X ray while exerting anterior drawer stress 10 degrees of plantar flexion 15 decanewton using Telometer device

8 Results Table 1. Data summary No. 115 Mean age (years) 37.5±13.5 (20.0, 74.0) M:F 66 : 49 Radiographic measurements (AP, Lat ) Distal tibial articular surface angle ( ) 91.1 ± 2.6 Bimalleolar tilt ( ) ± 2.8 Medial malleolar relative length 0.52 ± 0.07 Lateral malleolar relative length 0.86 ± 0.09 Medial malleolar slip angle ( ) ± 7.3 Anterior inclination of tibia ( ) 82.5 ± 3.1 Fibular position 0.65 ± 0.10 Radiographic measurements (stress view) Talar tilt ( ) 6.8 (SD 4.8) Anterior translation of talus (mm) 7.2 (SD 2.1) MRI evaluation ATFL (intact/partial/complete injury) 14 / 73 / 28 CFL (intact/partial/complete injury) 62 / 53 / 0 PTFL (intact/partial/complete injury) 89 / 25 / 1 Deltoid ligament (intact/partial/complete injury) 84 / 31 / 0 Presence of effusion 43 ATFL, anterior talofibular ligament; CFL, calcaneofibular ligament; PTFL, posterior talofibular ligament. Table 2. Factors affecting ankle stress radiographs by univariate analysis Tibiotalar tilt angle Anterior translation of talus Estimat SE p-value Estimat SE p- e e value Age Gender Radiographic measurements DTAS BT MMRL LMRL MMSA AI of tibia FP MRI evaluations Degree of ATFL injury Degree CFL injury of Degree of PTFL injury Degree of Deltoid ligament injury Presence of effusion < SE = standard error, DTAS = distal tibial articular surface angle, BT = bimalleolar tilt, MMRL = medial malleolar relative length, LMRL = lateral malleolar relative length, MMSA = medial malleolar slip angle, AI = anterior inclination, FP = fibular position, MRI = magnetic resonance image, ATFL = anterior talofibular ligament, CFL = calcaneofibular ligament, PTFL = posterior talofibular ligament

9 Table 3. Factors affecting tibiotalar tilt by multiple regression analysis Estimate SE p-value Tibiotalar tilt angle Age Gender BT Degree of ATFL injury < Degree of Deltoid ligament injury Table 4. Factors affecting anterior translation by multiple regression analysis Anterior translation of talus Estimate SE p-value Age Gender BT LMRL FP Degree of PTFL injury SE = standard error, BT = bimalleolar tilt, ATFL = anterior talofibular ligament, LMRL = lateral malleolar relative length, FP = fibular position, PTFL = posterior talofibular ligament

10 Conclusions - Age and sex, in addition to ligament injury shown on MRI could affect ankle stress radiographs in patients with lateral ankle instability - ATFL injury, and BT were significant factors affecting tibiotalar tilt angle on varus stress view. - PTFL injury and FP were significant factors affecting anterior translation of the talus on anterior drawer view.

11 Conclusions - Differences in demographic factors including age, sex, and bony anatomical structure of the ankle joint might predispose the results of ankle stress radiographs.

12 Thank you!!