A Monteggia fracture is defined as a fracture of the proximal ulna combined with a luxation of the radial head.

A new study published in Journal of Orthopaedic Surgery and Research evaluated the extent of instability of the radius head in proximal radioulnar joint (PRUJ), as a function of the severity of elbow fracture and ligamentous injury in an experimental biomechanical approach.

The present study used eight fresh-frozen cadaver arms. A tensile force of 40 N was exerted laterally, anteriorly or posteriorly onto the proximal radius. The dislocation in the PRUJ was photometrically recorded and measured by two independent examiners.

It was observed that an anterior instability remains relatively constant until the proximal third of the interosseous membrane is dissected. The radial head already dislocates relevantly in the posterior direction after dissection of the annular ligament with an additional considerable stability anteriorly and laterally. Thereafter, the posterior instability increases less pronouncedly relative to distal resected structures. While the lateral instability increases constantly during the progressing resection of the ligamentous structures.

In inference, it was stated that a complete healing of the ligament injury after functional treatment is hardly conceivable with ligamentary damage up to the level of the proximal interosseous membrane. A remaining instability of the proximal radius could therefore be a possible cause for the unsatisfactory clinical results after certain Monteggia fractures.

Source: Biewener A, Bischoff F, Rischke T et al. Instability of the proximal radioulnar joint in Monteggia fractures—an experimental study. J OrthopSurg Res. 2019;14(1). doi:10.1186/s13018-019-1367-7