Three-dimensional kinematics of the lunate, hamate, capitate and triquetrum with type 1 or 2 lunate morphology.

The purpose of this study was to investigate the differences in three-dimensional carpal kinematics between type 1 and 2 lunates. We studied 15 instances of wrist flexion to extension (nine type 1, six type 2), 13 of radial to ulnar deviation (seven type 1, six type 2), and 12 of dart-throwing motion (six each of type 1 and 2) in 25 normal participants based on imaging with computerized tomography. Mean proximal translation of the distal articular midpoint of the triquetrum relative to type 2 lunates during wrist radioulnar deviation was 2.9 mm (standard deviation (SD) 0.7), which was significantly greater than for type 1 lunates, 1.6 mm (SD 0.6). The hamate contacted the lunate in ulnar deviation and ulnar flexion of wrists with type 2 lunates but not with type 1. We conclude that the four-corner kinematics of the wrist joint are different between type 1 and 2 lunates.

In vivo triquetrum-hamate kinematics through a simulated hammering task wrist motion.

BACKGROUND: The shape and kinematics of the triquetrum-hamate joint have been the subject of continued research, as its articulation provides wrist stability and motion. The purpose of this study was to measure the in vivo articulation of the triquetrum-hamate joint as the wrist moves along an important functional wrist motion, the dart thrower's path. METHODS: The right wrist of six male and six female volunteers (average age [and standard deviation], 24.8 ± 3.8 years) were imaged with computed tomography in five positions along a simulated hammering task. Three-dimensional kinematics of the third metacarpal, triquetrum, hamate, and radius were analyzed with use of the rotation axis and the path of contact areas. RESULTS: As the wrist ulnar-flexed with respect to the radius, the triquetrum translated 3.7 ± 1.7 mm distally on the hamate. Approximately midway through this distal course, when the triquetrum appeared to engage the distal ridge of the hamate, the triquetrum began translating volarly. Total volar translation was 2.6 ± 1.1 mm. As the wrist ulnar-flexed, there was also a decrease in the distance and variability in the location of the triquetrum-hamate rotation axis from the hamate centroid: it decreased from 11.7 ± 4.1 mm to 3.3 ± 1.4 mm (p < 0.0001). CONCLUSIONS: Our findings support the concept that the triquetrum rotates on the convex ellipsoid surface of the hamate and that the helicoidal description of the triquetrum's motion on the hamate may be an oversimplification.

The effect of radioscapholunate fusion on wrist movement and the subsequent effects of distal scaphoidectomy and triquetrectomy.

Radioscapholunate arthrodesis is a salvage procedure indicated for osteoarthritis of the radiocarpal joint involving the lunate facet of the radius. This cadaver study examines changes in wrist motion resulting from radioscapholunate arthrodesis, and the effects of surgical techniques to improve the range of motion. Simulated radioscapholunate arthrodesis, distal scaphoidectomy and triquetrectomy were carried out sequentially on six cadaver forearms and measurements (maximum flexion/extension and radial/ulnar deviation) were taken in the intact situation and after each surgical step using a magnetic tracking device. Radioscapholunate arthrodesis diminishes the amplitudes of movements of the wrist in all directions, but range of motion in the radioscapholunate fused wrist improves after scaphoidectomy and improves further after triquetrectomy (88% of original flexion/extension and 98% of original radial/ulnar deviation). Radioscapholunate arthrodesis causes a significant change in kinematics between the hamate and the triquetrum in flexion/extension.

[The double-cup carpus: a demonstration of the variable geometry of the carpus]. / Le carpe à double cupule: illustration de la géométrie variable du carpe.

OBJECTIVES: The variable frontal geometry of the carpus has been known for many years, however there is no unanimity as to whether to describe the dynamic model of the carpus as comprising row or columnar functional units. The place of the scaphoid is also discussed. This study attempts to understand the organization and the composition of the functional units of the carpus. METHODS: We took radiographs of 40 normal right wrists in radial and ulnar deviation and measured the displacement in the coronal plane of each carpal bone except the pisiform. We measured the angular movements of each carpal bone compared to a vertical axis passing through the geometric centre of the carpus. This axis is parallel to the radial axis which is defined as the line joining the midpoints of the radius at 2 and 5 cm proximal to the radial articular surface. We studied the movement of each row and each column. RESULTS: Recorded angular movements were the followings: scaphoid 26 degrees, lunate 28 degrees, triquetrum 29 degrees, trapezium 44 degrees, trapezoid 50 degrees, capitate 50 degrees, hamate 56 degrees. Average angular movement within the first row is 27 degrees, within the second row is 50 degrees. Average angular movement within the radial column is 38 degrees, middle column is 39 degrees, ulnar column is 42 degrees. CONCLUSIONS: The amplitude of movement are similar for the bones of each row, and different for the bones of each column. The bones of each row tend to move together and can alone account for all movements of the wrist. The movements measured between each column are torsional intrarow movements, allowing congruence between the two rows and the glenoid surface of the radius. The scaphoid movements are superposable with those of lunate and triquetrum. Scaphoid kinematics joins the first row. Radio-ulnar deviation of the wrist is shared equally between the radiocarpal and midcarpal joints. This sharing of wrist movement between the two rows constitutes for us a double cup carpal model.