The distal radio ulnar joint. The influence of geometry and ligament on simulated Colles' fracture. An experimental study.

In five fresh frozen arm specimens Colles' fracture was simulated by a dorsal wedge osteotomy of the distal radius. A spring load was applied to the cortex of the distal radius fragment exerting a constant traction force in proximal direction. The distal radius fragment showed minimal dorsal angulation as the forearm was positioned in neutral or pronation, assuming the distal radio ulnar joint including its radio ulnar ligament was kept intact. As the forearm was moved into supination the distal fragment angulated dorsally to close the dorsal open gap in spite of the ligament being intact. When the radio ulnar ligament was detached the stability was however lost in any forearm position. The result supports the concept of immobilizing a satisfactorily reduced Colles' fracture in neutral position, possibly in slight pronation but never in supination.