[New radiologic data on the trapezo-metacarpal joint. The results of 330 cases].

Systematic x-rays in specific views and maximal amplitude of 330 trapezo-metacarpal joints in patients presenting with hand lesions has enabled us to define some original radiological parameters: the angle of the trapezium, the slope angle of the trapezium in anteversion and retroversion, trapezium mobility, the subluxation coefficient and the contact arc of the first metacarpal (M1) on the trapezium, defective reintegration of the base of the first metacarpal into the curve of the trapezium on AP and lateral views and the length of the intermetacarpal ligament. Statistical analysis, using analysis of variance, Chi-square test and correlation tests have demonstrated some correlations between all of these parameters allowing us to propose a pathophysiological hypothesis. In particular, this study emphasised the important role of a failure of the intermetacarpal ligament in the pathogenesis of proximal osteoarthritis of the thumb. Long before the onset of the well known signs of osteoarthritis, narrowing of the joint line and osteophytes, precursor radiological signs can be detected: loosening of the intermetacarpal ligament, excessive mobility of the trapezium, and poor reintegration of the base of M1 in the trapezium curve on AP and lateral films should now allow the early diagnosis and the proposal of preventive operations, such as intermetacarpal ligamentoplasty, reorientation osteotomies of the trapezium facet when the trapezium angle is too wide or new surgical techniques on the abductor carpi radialis, an almost constant expansion of the abductor pollicis longus on the trapezium.