[Treatment of instability of the metacarpophalangeal and trapeziometacarpal joints of the thumb].

Restoration of stability of the thumb represents an enormous gain of function for the patient and can be achieved by arthrodesis or ligament reconstruction. Ligament reconstruction should only be performed if good stability and mobility and a pain-free grip can also be achieved. In every case surgery must protect the delicate soft tissues and should be based on a profound knowledge of the anatomical and biomechanical circumstances. Instability of the trapeziometacarpal joint is rare but metacarpophalangeal joint instability (ulnar, palmar and radial) is relatively frequent. For both conditions arthrodesis is the most frequently used and easier surgical procedure. Ligament reconstruction is more difficult to perform but can maintain the mobility of these joints.