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Abstract
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INTRODUCTION: The purpose of this study was to classify the injury mechanism of TT and suggest a treatment method according to the mechanism.
MATERIALS AND METHODS: Forty TT with MRI scans and 3-D CT were enrolled. 3-D CT scans of coronoid fractures were used for classifying into O'Driscoll type representing injury mechanisms and measuring sizes. In MRI scans, lateral collateral ligament complex (LCLC) injuries were classified into distraction (D) type caused by varus force and stripping (S) type caused by forearm external rotation (ER) force. Using these findings, possible injury mechanisms were speculated and classified into groups. Characteristic soft tissue injury patterns of collateral ligaments and overlying muscles, direction of dislocation in simple X-rays, and the amount of involvement of radial head (RH) fracture were investigated. Ulnar and radial side instabilities of soft tissues were newly defined and investigated.
RESULTS: There were 29 (73%) cases by posterolateral external rotation (PLER), 5 (13%) cases by posteromedial external rotation (PMER), and 6 (14%) cases by posteromedial internal rotation (PMIR). Simple X-rays showed all posterolateral (PL) dislocations (DLs) in PLER TT compared to posteromedial (PM) or pure posterior (PP) DLs in PMER or PMIR TT. Regarding LCLC and OEM, they were all completely torn with D type in all PLER compared to D type in PMER or PMIR. Ulnar collateral ligament (UCL) was spared in 5 (17%) cases among 29 PLER in contrast to complete rupture (CR) in all PMER and PMIR. In PLER, PMER, and PMIR, involvement ratios of radial head fracture were 82% (range, 27% ∼ 100%), 61% (range, 25% ∼ 100%), and 61% (range, 25% ∼ 100%), respectively, and sizes of coronoid fractures were 7 mm (range, 1 ∼ 14 mm), 6 mm (range, 2 ∼ 11 mm), and 10 mm (range, 2 ∼ 16 mm), respectively. In PLER, PMER, and PMIR, percentages of ulnar side instabilities were 17%, 20%, and 17% respectively, and those of radial side instabilities were 59%, 60%, and 83%, respectively.
CONCLUSIONS: TT is caused by at least three mechanisms (PLER, PMER, and PMIR) with characteristic soft tissue injuries and fracture patterns. PLER is the main mechanism of injury. It is always observed in the form of PL DL on simple radiographs compared to PP or PM DL of PMER or PMIR. It should be managed individually based on injury mechanisms presenting different instability patterns. LEVEL OF EVIDENCE: Anatomy Study; Imaging.
Language: en |