BIOMECHANICAL TOPOGRAPHY OF HUMAN ARTICULAR-CARTILAGE IN THE FIRST METATARSOPHALANGEAL JOINT

The objective of this study was to provide a map of cartilage biomecha nical properties, thickness, and histomorphometric characteristics in the human, cadaveric first metatarsophangeal joint, to determine if no rmal articular cartilage was predisposed topographically to biomechani cal mismatches in articulating surfaces. Cartilage intrinsic material properties and thickness were obtained from seven pairs of human, fres hly frozen, cadaveric, metatarsophalangeal joints using an automated c reep indentation apparatus under conditions of biphasic creep. Eight s ites were tested: four on the metatarsal head, two on the proximal pha lanx base, and one on each sesamoid bone to obtain the aggregate modul us, Poisson's ratio, permeability, shear modulus, and thickness. Carti lage in the lateral phalanx site of the left metatarsal head had the l argest aggregate modulus (1.34 MPa), whereas the softest tissue was fo und in the right medial sesamoid (0.63 MPa). The medial phalanx region of the right joint was the most permeable (4.56 x 10(-15) meter(4)/Ne wton.second), whereas the medial sesamoid articulation of the metatars al head of the left joint was the least permeable (1.26 x 10(-15) mete r(4)/Newton.second). Material properties and thickness are indicative of the tissue's functional environment. The lack of mismatches in cart ilage biomechanical properties of the articulating surfaces found in t his study may be supportive of clinical observations that early degene rative changes, in the absence of traumatic events, do not occur at th e selected test sites in the human first metatarsophalangeal joint.