Carpal Instability Nondissociative after Intra-Articular Radius Fractures

Introduction Carpal instability nondissociative (CIND) is characterized by dysfunction of the entire proximal carpal row, manifested at either the radiocarpal joint, the midcarpal joint, or both. CIND may be distinguished radiographically from CID by the lack of a dissociation or bony gap within the proximal carpal row. Conceptually, radiocarpal ligament insufficiencies are CIND problems in which the entire carpus is translocated in a palmar, dorsal, radial, or ulnar direction without proximal row dissociation.¹

Adaptive carpal instability following malunited, extra-articular Colles fracture was defined as an extrinsic midcarpal dynamic instability by Taleisnik and Watson.² In 1993, we described two types of adaptive carpal instability following Colles fractures,³ a Type I = lax reducible dorsal carpal malalignment, which can be improved and totally corrected by radial osteotomy, and a Type II = fixed nonreducible dorsal carpal malalignment that will remain unchanged despite correction of the radial deformity.

Material and Methods In this presentation, we report four intra-articular radius fractures that developed CIND—two with a palmar pattern and two with a dorsal pattern. Of the two patients who developed a fixed nonreducible palmar CIND following dorsal radiocarpal dislocations, one had a successful closed reduction, and one had an insufficient open reduction of the distal radius fracture. In both cases, the whole proximal palmar row adopted a flexed position with slight radiocarpal subluxation, while the midcarpal joint exhibited a hyperextended position. Both patients were salvaged with a radio-scapho-lunate fusion and distal-scaphoid-pole resection.

The other two cases revealed a dorsal type of CIND. The first patient had a malunited radial styloid fracture with dorsal rotation of the whole proximal row and slight palmar subluxation. No intrinsic intercarpal ligament lesions were found during diagnostic arthroscopy, and important degenerative changes were already present in the radio-scaphoid joint. The last patient showed a very similar carpal malalignment following open reduction and internal fixation of an intra-articular distal radius fracture involving both the lunate and the radial facets of the joint with initial dorsal displacement. The intra-operative arthroscopy showed a fracture gap without step-off at the level of the intra-articular fracture line, and the midcarpal arthroscopy showed no dissociative tears of the intrinsic ligaments. However, the patient developed a CIND with dorsally rotated proximal carpal row and a flexion deformity in the midcarpal joint. At three years, the patient remained asymptomatic with the same radiographic deformity.

Conclusion We have identified four cases of CIND, two palmar and two dorsal associated with intra-articular fractures of the distal radius. The radiographic and arthroscopic findings confirmed the definition of CIND in both cases with a flexion or an extension deformity of the whole proximal carpal row without intrinsic lesions of the intercarpal ligaments. We postulate that the malalignment of the proximal carpal row is secondary to the displacement and malposition of nonreduced articular fragments and/or an associated extrinsic radiocarpal capsulo-ligamentous lesion. Depending on the palmar or dorsal rotation of the proximal carpal row, the midcarpal joint develops a compensatory deformity in the opposite direction. Three patients were symptomatic—two with a fixed deformity and one with posttraumatic arthritic changes—and were treated with a radio-scapho-lunate fusion. The last patient did not require further surgical treatment.

Fig. 1 (a) Radiocarpal fracture dislocation. (b) Radiograph following closed reduction and percutaneous pinning showing an adequate reduction of the distal radius and normal carpal alignment. (c) Six weeks postreduction film reveals a palmar CIND-type of carpal instability. (d) Fixed volar CIND carpal malalignment with slight dorsal carpal subluxation. The palmar fracture gap is still visible at nine weeks postoperatively. (e) Radiographs at 18 months following injury. The carpal malalignment is fixed. (f) Radiographs six months after radio-scapho-lunate fusion and distal scaphoid resection. The bone graft was taken from the distal radius and replaced with a bone substitute.

Fig. 2 (a) Radiographs of a dorsally displaced intra-articular fracture of the distal radius. (b) Radiographs eight weeks postoperatively. Notice dorsally rotated proximal carpal row and a compensatory flexion deformity of the mid-carpal joint. The most ulnar screw was inside the DRUJ and blocked pronation and supination. (c) One year after removal of the plate and DRUJ arthrolysis. Notice increase in the CIND dorsal-type of carpal instability with an extended scaphoid and lunate. (d) At three years the carpal deformity has remained the same and the patient is asymptomatic. The S-L angle measures 43°.

References

References

1 Wolfe SW, Garcia-Elias M, Kitay A. Carpal instability nondissociative. J Am Acad Orthop Surg 2012;20(9):575–585

2 Taleisnik J, Watson HK. Midcarpal instability caused by malunited fractures of the distal radius. J Hand Surg Am 1984;9(3):350–357

3 Fernandez DL. Reconstructive procedures for malunion and traumatic arthritis. Orthop Clin North Am 1993;24(2):341–363