[Fractures and dislocation fractures of the wrist joint]

Most carpal fractures are based on the same injury mechanism. In most cases the injury is caused by a fall on the dorsiflexed hand, which is raised as a protective measure, and less frequently by a fall on the clenched fist. The latter leads to passive palmar flexion, pronation and radial inclination of the hand; in the former, the hand is passively superextended by the impact, supinated, and brought into ulnar inclination. The instability caused by injury to various articular structures has four developmental stages. The bones or syndesmoses that are involved depend on the stage and quantitative relationship between the three above-mentioned moments of force. If the lateral ligament of the wrist is slack, scaphoid fractures occur; in the last stage of superextension, fractures of the capitate bone occur. With increasing ulnar inclination, perilunar dislocations or fracture-dislocations and triquetrum fractures occur in the third stage and dislocations of the semilunar bone in the fourth stage. In addition, compression and avulsion of the 1st, 4th or 5th metacarpal bones cause fractures of the trapezium and the hamate bone. To avoid unpleasant late sequels, scaphoid fractures with diastasis due to soft tissue interposition or non-reducible dislocated scaphoid fractures must be treated surgically. Vertical oblique fractures and scaphoid fractures with small proximal fragments are relatively good indications for operation. Perilunar instability and dislocations, particularly De Quervain's fracture-dislocations, must be treated operatively because reduction of the scaphoid bone requires a different approach than correcting alignment in the carpus and because soft tissue interpositions are always present, even though they may not be evident in the X-ray pictures. Fracture-dislocations in the distal carpal row also require operation, preferably percutaneous internal fixation using K-wire and fluoroscopy. Immobilization is accomplished by a below-elbow cast with a dorsal plaster splint up to the interdigital webs and from the palmar to the proximal crease. The thumb is only embedded in trapezium fractures; fractures requiring fist or above-elbow casts are indications for operation.