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.
Department of Orthopaedics, The Warren Alpert Medical School of Brown University and University Orthopedics, 2 Dudley Street, Suite 200, Providence, RI 02905, USA.
Robin N
RN
Kamal
Michael J
MJ
Rainbow
Edward
E
Akelman
Joseph J
JJ
Crisco
D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D050824:Carpal Joints / Q000000981:diagnostic imaging / Q000502:physiology*; D005260:Female; D051225:Hamate Bone / Q000000981:diagnostic imaging / Q000502:physiology*; D018737:Hand Strength / Q000502:physiology; D006801:Humans; D008297:Male; D011859:Radiography; D016059:Range of Motion, Articular / Q000502:physiology*; D012016:Reference Values; D013647:Task Performance and Analysis; D051221:Triquetrum Bone / Q000000981:diagnostic imaging / Q000502:physiology*; D014955:Wrist Joint / Q000000981:diagnostic imaging / Q000502:physiology*; D055815:Young Adult