Analysis of trapeziometacarpal joint congruency during opposition using four dimensional computed tomography.

OBJECTIVES

The trapeziometacarpal (TMC) joint is a puzzling joint with complex kinematics. Historically, instability and subluxation of the TMC joint are quantified by measurements as trapezial tilt, dorsal subluxation angle and radial subluxation ratio on two dimensional radiographs. These measurements are influenced by different factors such as radiographic incidence and position of the thumb relative to the hand. The recent introduction of four dimensional (4D) CT allows analysis of joint kinematics during an in vivo motion. The aim of this study was to analyze the congruency of the TMC joint during an active opposition and retropulsion movement using 4D CT.

PATIENTS AND

METHODS

A total of 10 healthy volunteers were included and their TMC joint kinematics were studied during a retropulsion-opposition-retropulsion movement. Trapezial tilt, dorsal subluxation angle and radial subluxation ratio were measured for every patient during this active motion.

RESULTS

Trapezial tilt evolved from 124 in retropulsion to 120 degrees in opposition and evolved from 120 degrees in opposition to 124 degrees in retropulsion. Dorsal subluxation angle evolved from 68 degrees in retropulsion to 45 degrees in opposition and evolved from 44 degrees in opposition to 68 degrees in retropulsion. Radial subluxation ratio evolved from 20% in retropulsion to 20% in opposition and evolved from 19% in opposition to 20% in retropulsion.

CONCLUSION

Trapezial tilt and dorsal subluxation decreases with opposition, whereas radial subluxation remains constant. Future research could use this model to investigate the influence of hyperlaxity and osteoarthritis on TMC joint kinematics and joint congruency.