Comparative in vivo kinematic analysis of normal and osteoarthritic trapeziometacarpal joints.

PURPOSE: Although extensive studies have been conducted on the trapeziometacarpal (TM) joint, there have been few quantitative studies on its in vivo kinematics. The purposes of this study are to quantitatively evaluate the in vivo kinematics of the TM joint with a fluoroscope and to determine the difference between normal and arthritic joints.
METHODS: Fourteen healthy hands and 8 symptomatic hands with idiopathic osteoarthritis were included in this study. The healthy subjects were divided into 2 groups: a younger control group aged under 50 years (n = 7) and an older control group aged 51 years or older (n = 7). Radial and dorsal translations of the center of rotation (COR) were quantified in active abduction-adduction and active flexion-extension. In addition, volar tilt of the metacarpal facet of the TM joint was measured on the lateral view.
RESULTS: The CORs in flexion-extension translated more dorsally in the patient group than those in the 2 control groups whereas the CORs in abduction-adduction did not differ significantly between the patient group and the control groups. There was no significant difference in the translation of COR between the 2 control groups in either abduction-adduction or flexion-extension. The average volar tilt in the patients with osteoarthritis increased significantly compared with those in the control groups.
CONCLUSIONS: Dorsal translation of the COR in flexion-extension but not radial translation in abduction-adduction is the kinematic characteristic of the arthritic TM joint. We suggest that increased volar tilt is a predisposition to the dorsal translation of COR in the patient group.