Differential Distraction of Unstable Fractures of the Distal Radius by an Ilizarov Half-Frame: Experience Based on 19 Cases

Purpose: Evaluation of differential distraction using an Ilizarov half-frame in realigning unstable fractures of the distal radius. Methods: in 4 cases entering into malunion and in 14 cases fractured primarily, differential radial distraction was performed using an assembly consisting of three half-rings, a proximal fixed with Schanz screws to the proximal radius, a middle fixed with pretensioned K-wires to the distal radius and a distal fixed to the hand by means of two Schanz screws, one inserted into the second, the other into the fifth metacarpal. The half-frames were joined to each other by rod-uni axial hinge-rod systems. Incremental distraction was conducted at the fracture site between the proximal and distal half-rings. In 7 of the above cases, the proximal radius was displaced ulnodorsally obliterating the interosseous space and blocking supination. Differential interosseous radio-ulnar distraction had to be added to open the interosseous space. The attachment of the proximal half-ring was modified by adding a coupling device connecting the Schanz screws inserted into the radius with the proximal half-ring. The latter was also fixed to the ulna by means of two Schanz screws. Using the coupling device, the radius was distracted laterally opening up the interosseous space. Differential radial distraction, radial bone transport and differential carpus distraction were combined together in a case of ununitcd fracture of the distal radius associated with severe radial shortening and angulation. Proximal radial bone transport using a half-ring inserted between the proximal halfring and the distal two half-rings was used to fill the bone gap resulting after resection of the fibrous non-union. Differential radial distraction was carried out to adjust ulnar variance, radial angulation, radial length. To restore mobility at the radiocarpal joint, stretching of its capsule through differential carpus distraction was carried out. Results: Differential radial distraction has made it possible to adjust ulnar variance, palmar tilt (palmar slope), radial angulation (radial inclination), radial length and movements at the radiocarpal joint independently of each other. Palmar tilt became excessive in 3 cases, however. Due to overdistraction, an excessive decrease in ulnar variance was noted in 16 cases and an excessive increase in radial length in 8 cases. Articular incongruity had to be corrected by open reduction, K-wire augmentation and bone support. Because of extensive comminution and compression, differential distraction of the radius could not be applied in one case entering into malunion after anterior buttress plating for a comminuted volar Barton s fracture. In this instance, carpus distraction followed by grafting of the comminuted segment was resorted to. The functional result was fair due to the extensive fibrosis of the palmar capsule and flexor tendons consequent upon the previous surgeries. Differential interosseous radio-ulnar distraction has made it possible to open the interosseous space between radius and ulna. In one case, because opening the interosseous space was more volarly directed than along the interossous membrane, the proximal radius shifted radiovolarly. This was later on corrected by adjusting the direction of pull between the radius and ulna. Using differential radial distraction, radial bone transport and differential carpus distraction the radial clubhand in the neglected non-union was corrected fully. Palmarflexion became limited to 50 degrees, but the patient had a powerful grip. A decrease in ulnar variance and a disproportionate increase in radial angulation, mainly due to collapse of the medial column of the radius, occurred in one case in which the external fixator was removed at 4 weeks. After this case. the fixator was routinely removed at 6 weeks. Poor hand and wrist function occurred due to tendon adhesions in one case presenting with a comminuted volar Barton s fracture. Otherwise, gradual stretching of the tissues helped overcome tendon and capsular tightness. Conclusions: Differential radial distraction has made it possible to adjust ulnar variance, palmar tilt (palmar slope), radial angulation (radial inclination), radial length and movements at the radiocarpal joint independently of each other. It could be combined with differential interosseous radioulnar distraction, which should be carried out along the interosseous plane to prevent volar displacement of the proximal radius. It could also be combined with radial bone transport and differential carpus distraction in neglected nonunions. Overdistraction should be limited to an ulnar variance of-2 mm. The fixator has to be kept for six weeks. Hand function is not affected by it. K-wire augmentation and grafting have to be added to correct articular incongruity. Limitations to differential radial distraction are posed by the degree of comminution of the distal radial segment; in such instances, differential carpus distraction and bone grafting have to be resorted to.