Background: Zancolli theorized that the first metacarpal bone axially rotates on the semispheroidal part of the trapezium, which is controlled by ligaments. This study used three-dimensional computed tomography (3D-CT) to describe the motion of the first metacarpal bone on the trapezium.
Methods: 3D-CT images were taken of the left hand of 30 healthy volunteers (mean age 40.0 ± 5.440.0 ± 5.4 years, 15 men and 15 women). They were divided into five groups: radial abduction, retroposition, adduction, palmar abduction, and opposition. The range of motion of radial abduction and palmar abduction of the trapeziometacarpal joint was measured from the first metacarpal bone to the second metacarpal bone. The range of motion of pronation was measured following Cheema's method. The main contacts of the joint surface of trapezium and the first metacarpal bone were determined on the 3D-CT images.
Results: Pronation of the trapeziometacarpal joint was 42 ± 9° in radial abduction, 61 ± 6° in retroposition, 68 ± 6° in adduction, 91 ± 6° in palmar abduction, and 99 ± 3° in opposition. Radial abduction was 40 ± 7° in radial abduction, 17 ± 10° in retroposition, 15 ± 7° in adduction, 13 ± 6° in palmar abduction, and -4 ± 3° in opposition. Palmar abduction was -8 ± 8° in radial abduction, 0 ± 3° in retroposition, 14 ± 6° in adduction, 40 ± 7° in palmar abduction, and 37 ± 5° in opposition. The contact surfaces of the trapezium and the first metacarpal bone were dorsal and ulnar in radial abduction, radial and ulnar in retroposition, and volar-ulnar and volarradial in opposition, respectively, while they were both central in adduction and both radial in palmar abduction.
Conclusions: The range of motion of the trapeziometacarpal joint was 44° for radial abduction/adduction, 48° for palmar abduction/adduction, and 57° for pronation/supination. The varying contact surfaces of the trapezium and the first metacarpal bone enabled a wide range of motion.