MRI detection of forearm soft tissue injuries with radial head fractures

Abstract

Background: This study aims to evaluate the incidence of forearm soft tissue abnormalities associated with radial head fracture severity based on the Mason classification system.

Methods: Eighteen patients (age 18-45 years) were prospectively evaluated with elbow radiographs and magnetic resonance imaging (MRI) following longitudinal forearm trauma. MRI was performed within 10 days of the initial injury. Radiographs and MR images were evaluated in a blinded fashion by two musculoskeletal radiologists.

Results: Thirteen of 18 patients presented with Mason type I radial head fractures. In all patients with Mason type I fractures, the interosseous membrane (IOM) was intact. Two patients had Mason type II fractures with associated partial and compete tearing of the IOM and three patients had Mason type III fractures with complete tearing of the IOM. Edema was noted in the pronator quadratus in six of 13 type I injuries and seen in all type II and III injuries. No structural forearm soft tissue abnormalities were present in patients with Mason type I injuries. The presence of edema within the pronator quadratus correlated with distal forearm pain.

Conclusions: The severity of radial head fracture correlates with longitudinal forearm injury evidenced by the presence of IOM tearing. The findings suggest patients with Mason type II or III fractures of the radial head should undergo further evaluation of the forearm for associated soft tissue injuries. Edema within the pronator quadratus was present following forearm trauma regardless of the severity of fracture and was related to symptomatic forearm pain.

Keywords: Essex-Lopresti lesion; Forearm pain; Interosseous membrane; Longitudinal forearm trauma; Mason classification; Radial head fracture.

Fig. 1

Radial head fractures (arrow) were classified according to the Mason system based on radiographic findings; a Mason type I non-displaced radial head fracture, b Mason type II minimally displaced marginal radial head fracture, c Mason type III displaced comminuted radial head fracture

Fig. 2

The central portion of the interosseous membrane was evaluated in each patient with MR imaging (AX T2 FS). a In all patients with Mason type I radial head fractures, the central IOM was intact (arrow). b In this patient with Mason type II fractures, partial disruption of the central IOM was identified (arrow). c In all patients with Mason type III fractures, complete IOM disruption was present (arrow)

Fig. 3

Soft tissue abnormalities were present in all three Mason classification groups. However, no structural abnormalities were demonstrated on MR imaging in patients with Mason type I fractures (AX T2 FS). a In all patients, there was edema and some degree of joint effusion at the elbow on MR imaging. b In patients with distal forearm pain, moderate edema was demonstrated in the pronator quadratus muscle