Experimental Methods for Studying the Contact Mechanics of Joints

Abstract

Biomechanics researchers often experimentally measure static or fluctuating dynamic contact forces, areas, and stresses at the interface of natural and artificial joints, including the shoulders, elbows, hips, and knees. This information helps explain joint contact mechanics, as well as mechanisms that may contribute to disease, damage, and degradation. Currently, the most common in vitro experimental technique involves a thin pressure-sensitive film inserted into the joint space; but, the film's finite thickness disturbs the joint's ordinary articulation. Similarly, the most common in vivo experimental technique uses video recording of 3D limb motion combined with dynamic analysis of a 3D link-segment model to calculate joint contact force, but this does not provide joint contact area or stress distribution. Moreover, many researchers may be unaware of older or newer alternative techniques that may be more suitable for their particular research application. Thus, this article surveys over 50 years of English-language scientific literature in order to (a) describe the basic working principles, advantages, and disadvantages of each technique, (b) examine the trends among the studies and methods, and (c) make recommendations for future directions. This article will hopefully inform biomechanics investigators about various in vitro and in vivo experimental methods for studying the contact mechanics of joints.

Figure 1

An idealized ball-and-socket joint mimicking a shoulder or hip. Diameter D, elastic modulus E, or Poisson's ratio ν may or may not be known. However, in vitro or in vivo experimental techniques can still be used to determine joint contact force F, area A, or stress σ.

Figure 2

Mechanochemical methods for joint contact mechanics research: (a) Fujifilm; (b) microindentation film [17]; (c) casting material; (d) staining dye. Images are used by permission of the indicated citations; otherwise, they are original to the current authors.

Figure 3

Electronic sensor methods for joint contact mechanics research: (a) Tekscan [9]; (b) strain gages; (c) piezosensors; (d) e-coating. Images are used by permission of the indicated citations; otherwise, they are original to the current authors.

Figure 4

Noninvasive methods for joint contact mechanics research: (a) videography; (b) laser spectroscopy; (c) optical visualization; (d) photoelasticity [18]; (e) proximity; (f) ultrasound [19]; (g) X-rays [20]. Images are used by permission of the indicated citations; otherwise, they are original to the current authors.