Isolated coronoid fracture: Assessment by magnetic resonance imaging for concomitant injuries.

BACKGROUND: Ligamentous injury associated with isolated coronoid fracture had been sparingly reported. Concealed or unclear fractures and ligamentous or articular cartilage lesions are promptly acknowledged by magnetic resonance imaging (MRI) but cannot be entirely pictured in regular radiological assessments. In isolated coronoid fracture, the fragment size is very small and due to the complex anatomy surrounding the coronoid radiographic imaging may not be sufficient. The purpose of this study was to evaluate the incidence of combined osteochondral and ligamentous injuries by magnetic resonance imaging (MRI) in 24 patients with an isolated coronoid fracture.

MATERIALS AND METHODS: In a retrospective study conducted at tertiary hospital between 2009 and 2011, elbow radiographs (anteroposterior and lateral views), computed tomography scan images, and MRI in the sagittal, coronal, axial, oblique, and coronal oblique planes were collected and reviewed. Musculoskeletal radiologist with subspecialty training in musculoskeletal MR interpretation and a fellowship-trained shoulder and elbow surgeon evaluated the MRI.

RESULTS: The incidence of associated injuries revealed torn lateral collateral ligament (LCL) in all 24 patients (100%) while 15 patients (62.5%) had common extensor muscle tears. Seven of 24 elbows (29.2%) showed medial collateral ligament (MCL) tear, and 13 of 16 patients (81.3%) with anteromedial facet fracture had MCL attached to the fragment. Five of 24 (20.8%) cases had contusions on the radial head. On the distal humeral side, 15 patients had bone contusions on the posterior inferior of the trochlear on sagittal view. The ligament affections of the LCL were confirmed intraoperatively and repaired.

CONCLUSION: LCL injury was consistent in all isolated coronoid fracture. The forces resulting in the injury appear similar to varus distraction forces acting in the knee leading to distraction injuries of the lateral structures of the knee joint. As concurrent osteochondral injuries and ligamentous injuries are not rare, magnetic resonance analysis serves as an excellent tool for analysis of the ligamentous injuries preoperatively and aids in surgical planning.