[Fractures of the trapezium. Mechanisms. Anatomo-pathology and therapeutic indications].

Fractures of the trapezium are rare and often unrecognized lesions; their diagnosis can only be made by radiographs with specific projections that clearly separate the outline of the trapezium from the radial side of the carpal bony complex. Starting from a series of 88 cases collected from the world literature, 34 of which had been examined by the authors, a study was made of the different mechanisms of these fractures, their main fracture lines and displacements and the current indications for treatment. The physio-pathology of fractures of the trapezium was investigated by personal experiments conducted in the laboratory on 26 wrists and showed 3 main mechanisms: a fall on the hand with the wrist extended and radially deviated (Manon) and direct commissural trauma combined with various degrees of shearing described by Monsche. The fracture line is, in most cases, a vertical one and the lateral fragment which is connected to the first metacarpal is often subluxated proximally and radially. The treatment of these fractures can be conservative with immobilization in plaster either as the fracture lies or after reduction, or by continuous traction after reduction, or it can be operative. Direct internal fixation, completed, if necessary, by a stabilization of the thumb column using one of the various implants available today for the fixation of small fragments, should particularly be used for displaced and unstable fractures. Partial removal of the trapezium should be reserved for small fracture fragments that do not affect the joint surface or affect it very little. Proper treatment of this rare fracture is a key condition for the future function of the thumb column.