In vivo CT study of carpal axial alignment

Axial rotation of the carpal bones forms an important component of all wrist movements; however, carpal alignment in the axial plane has somehow not attracted attention. The present study comprised computed tomography (CT) imaging of the wrist joint in 53 asymptomatic volunteers lying prone with the shoulder abducted, elbow flexed and the palm facing down. Axial axes of various carpal bones and the distal radius were drawn and measured. The scaphoid axis was found to be in neutral position in 11%, and supinated in 89% of wrists, with mean of 16 degrees (SD 9 degrees ) while the lunate axis was in neutral position in 17% and supinated in 83% of the wrists with mean of 13 degrees (SD 9 degrees ). The axis for the triquetrohamate joint was found to be 9 degrees pronated (SD 13 degrees ) and 6 degrees supinated (SD 7 degrees ) for the capitohamate joint. Mean values for various carpal angles were 24 degrees, 21 degrees, 3 degrees, 22 degrees and 7 degrees for the radioscaphoid, radiolunate, scapholunate, lunotriquetral and lunocapitate angle, respectively. Examination was repeated in ten volunteers and showed statistically similar values for the various measurements, except the lunotriquetral angle. The present study provides a reference database of normal anatomy for carpal axial alignment. Its potential applications include identifying abnormal axial alignment of the carpal bones that may occur in various pathological conditions affecting the wrist joint, and also quantification of normal and abnormal axial motion of the carpal bones.