Quantified contours of curvature in female index, middle, ring, and small metacarpophalangeal joints.
OBJECTIVE
To study and quantify the morphology of the curvature of the surfaces of metacarpophalangeal metacarpophalangeal joints and to relate joint morphology to joint function.


METHODS
Forty metacarpophalangeal joints of the index, middle, ring, and small fingers from 5 right and 5 left hands were taken from female cadavers. The articulating surfaces of the metacarpal head and the base of the proximal phalanx were copied in a true-to-scale fashion. The hard plaster models were sliced in 7 sagittal and 7 transverse planes. The curvatures of the section contours were determined with circular gauges. Statistical analyses were performed by analysis of variance and paired Student t-tests.


RESULTS
In the sagittal plane, the cartilaginous surface of the metacarpal head is divided into 2 functional regions and a third dorsal region that does not articulate with the base of the proximal phalanx. The articulating surface of the base of the proximal phalanx approximates a circle in the midsagittal plane. The mean median sagittal radius of curvature of the dorsal articulating aspect of the metacarpal head (6.9 mm) is 33% smaller than that of the base of the proximal phalanx (10.3 mm). The palmar articulating aspect of the metacarpal head (5.8 mm) is 44% smaller than that of the base of the proximal phalanx (10.3 mm). In the median transverse section, the mean radius of curvature of the metacarpal head (7.3 mm) is 18% smaller than that of the base of the proximal phalanx (8.9 mm).


CONCLUSIONS
The data demonstrate the highly significant incongruity in the curvature of the articulating pair. This incongruity provides a joint space with its greatest dimension in the sagittal plane. From a mechanical perspective, the metacarpophalangeal joint mechanically represents a joint with 5 kinematic degrees of freedom: 2 for flexion and extension, 2 for abduction and adduction, and 1 for axial rotation.
Dumont
Clemens
C
Department of Trauma Surgery, Plastic and Reconstructive Surgery, University of Göttingen, Göttingen, Germany. clemens.dumont@med.uni-goettingen.de
Ziehn
Claudia
C
Kubein-Meesenburg
Dietmar
D
Fanghänel
Jochen
J
Stürmer
Klaus Michael
KM
Nägerl
Hans
H
D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D002102:Cadaver; D005260:Female; D050278:Finger Phalanges / Q000033:anatomy & histology; D006801:Humans; D008662:Metacarpophalangeal Joint / Q000033:anatomy & histology*; D012727:Sex Characteristics