[Traditional radiology in the assessment of posttraumatic carpal instability]

Carpal instability is a painful posttraumatic syndrome with early or late loss of the normal alignment of the carpal bones, which can be caused by a variety of injuries, from minor sprain to major fracture-dislocation of the carpal-wrist complex. If the trauma causing instability is a fracture, a severe dislocation or a fracture-dislocation, the radiographic diagnosis is not particularly difficult. The morphologic and dynamic complexity of the carpal region represents, instead, a major obstacle in the radiologic diagnosis of mild or moderate sprains because the morphologic alterations on standard static views are minimal or absent in these conditions.

We reviewed 214 injuries causing posttraumatic carpal instability including both the cases classified by the Data Analysis Center of the Istituto Ortopedico Rizzoli as carpal dislocations and fracture-dislocations from January, 1975, to July, 1996, and the more recent cases directly observed at our Casualty Clinic. In the former cases, we reviewed only the available images, while our patients were examined with comparative standard and under stress or dynamic views.

Of 214 lesions causing posttraumatic carpal instability, 43 along the great arch were classified as severe because they were easily detectable on standard films and 171 along the small arch were classified as mild because slight/no abnormalities were detected on standard static views. Only dynamic imaging showed posttraumatic carpal instability demonstrating the integrity of the ligaments and of the carpal hinges, as well as gaps or asymmetry not detected on static views.

We suggest the systematic use of dynamic imaging in the cases where static findings are negative or poor, in the patients with a painful wrist after an apparently minor sprain. Missed or delayed diagnoses are thus reduced, as well as the consequent joint incongruity and/or chronic subluxation which may severely impair these patients.