A STEREOPHOTOGRAMMETRIC METHOD FOR DETERMINING IN-SITU CONTACT AREAS IN DIARTHROIDAL JOINTS, AND A COMPARISON WITH OTHER METHODS

Determination of contact areas in diarthrodial joints is necessary for understanding the state of stress within the articular cartilage laye rs and the supporting bony structures. The present study describes the use of a stereophotogrammetry (SPG) system [Huiskes et al., J. Biomec hanics 18, 559-570 (1985) and Ateshian et al., J. Biomechanics 24, 761 -776 (1991)] for determining contact areas in diarthrodial joints, usi ng a surface proximity concept similar to the one used by Scherrer et al. [ASME J. biomech. Engng 101, 271-278 (1979)]. This method consists of evaluating the proximity of the articular surfaces to determine jo int contact areas using precise geometric models of the joint surfaces obtained from the SPG system, and precise kinematic data, also obtain ed from SPG. In this study, the SPG method for determining contact are as is compared to other commonly used methods such as dye staining, si licone rubber casting and Fuji film contact measurement techniques whi ch have been often used and reported by other investigators. The bovin e glenohumeral joint and the bovine lateral tibiofemoral articulation (without the meniscus) were used to represent congruent and incongruen t joints, respectively. While all the methods yielded consistent conta ct patterns for the incongruent tibiofemoral articulations, the result s for the congruent bovine glenohumeral joints showed that the SPG and Fuji film methods were in better agreement than those obtained from t he dye staining and silicone rubber casting methods. The advantages of the new SPG method are that it can be used for intact joints, and use d repeatedly and quickly thus making contact-area movement analyses po ssible [Soslowsky et al., J. orthop. Res. 10, 524-534 (1992)]. The res ults of this comparison study show that the SPG technique is a reliabl e and versatile method for determining contact areas in diarthrodial j oints.