1994 William J. Stickel Gold Award. Contact characteristics of the ankle joint. Part 2. The effects of talar dome cartilage defects.

Variations in ankle joint contact characteristics caused by articular defects of the talar dome were investigated in 14 fresh-frozen cadaver specimens using pressure-sensitive film. Intact ankle and foot specimens were mounted in a materials tester on a loading frame which allowed positioning in neutral, and 20 degrees of dorsiflexion and plantarflexion. Joint contact prints were recorded while an 800 N load was axially applied through the leg. Specimens were randomly placed into two lesion groups: either anterolateral or posteromedial. During testing, each specimen had four concentrically placed lesions on the talar dome, graduated in size. Following removal, the film transducers were digitized along with pressure calibration prints. The images were analyzed quantitatively to determine contact areas, mean contact pressures, ratio of to contact plafond areas, and high pressure centroid position as a function of lesion size and location. The results demonstrated significant changes in contact characteristics for larger lesions (> or = 7.5 x 15 mm) (P < 0.05). These findings suggest that determining the size of a lesion may assist in predicting the long-term outcome of ankles with cartilage defects.

Contact characteristics of the ankle joint. Part 1. The normal joint.

The contact characteristics of ankle joints in 18 fresh cadaver specimens were studied by using pressure-sensitive film to provide baseline information for subsequent studies of various pathologic ankle conditions. Specimens, consisting of the distal half of the tibia and fibula and the intact ankle and foot, were mounted in a materials testing system on a loading frame that allowed positioning in neutral, and 20 degrees of plantarflexion and dorsiflexion. An 800 N load (1 body weight) was axially applied to the specimens through the tibia with 10% of the total load distributed through the fibula. Transducers made of pressure-sensitive film were used to make a contact print and were scanned along with calibration strips to form a digital image. The image was analyzed quantitatively to determine total contact area, mean contact pressure, ratio of contact to plafond areas, and high pressure zone centroid location as a function of sagittal plane foot position in the normal ankle joint. The results demonstrated significant changes in ankle joint contact characteristics with different foot positions.

A biomechanical comparison of four methods of fixation of the trapeziometacarpal joint.

Four methods of internal fixation for trapeziometacarpal arthrodesis were evaluated for biomechanical stability under axial compression, torsion, and cantilever bending in either flexion-extension or radial-ulnar deviation. The techniques tested included crossed Kirschner wires, cerclage wiring, cup and cone with a single oblique Kirschner wire, and a tension band technique that has not previously been reported. Results reported included stiffness (load/deformation) of the construct and toggle (displacement without load applied, after cyclic loading). The tension band and cerclage techniques provided greater construct stiffnesses in axial loading than crossed Kirschner wire or cup-and-cone fixation, and toggle was significantly lower than for specimens fixed by the cup-and-cone technique. In torsion the tension band technique produced fixation that was significantly stiffer than cup-and-cone fixation. In cantilever bending the differences between fixation systems were not significant, except between cerclage and cup-and-cone techniques in flexion-extension. On the basis of our results in a biomechanical model, the tension band technique offers superior fixation in torsion, the cerclage technique in flexion-extension, and both in axial loading.