The Association Between the Volar Aspect of the Distal Radial Diaphysis and the Lunate Rotation Center on Lateral View X-ray of the Wrist

PURPOSE: For the treatment of severe distal radius fracture dislocations or malunions, especially those accompanied by intra-articular fractures, radiographic indexes based on the relationship between the carpus and radius are occasionally needed to achieve the ideal radiocarpal reconstruction. This study defined a reference point on the lunate and examined whether this point was located on a line extending along the volar aspect of the distal radial diaphysis on lateral radiographs of the wrist. METHODS: Two hundred one lateral wrist radiographs of adults were obtained, and the center of a circle passing through 3 selected points on the proximal articular surface of the lunate was defined as the lunate rotation center. Thereafter, the distance between the rotation center and a line extending along the volar aspect of the distal radial diaphysis was measured. Additionally, the distance between the rotation center and the midpoint of the distal articular surface of the lunate was measured. RESULTS: The mean distance between the lunate rotation center and the line extending along the volar aspect of the distal radial diaphysis was −0.01 ± 0.09 mm. The difference in this distance between both wrists in the same patient was 0.3 ± 0.12 mm. The distance between the rotation center and the midpoint of the distal articular surface of the lunate was 0.3 ± 0.05 mm. CONCLUSIONS: This study demonstrated that the lunate rotation center was located on a line extending along the volar aspect of the distal radial diaphysis and at the midpoint of the distal articular surface of the lunate. CLINICAL RELEVANCE: This study demonstrates that this association could become an important index for preoperative planning of corrective osteotomy for complicated intra-articular distal radial fracture malunions. Additionally, it may aid in confirming the reduced position during or after surgery for wrist fracture dislocations.