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- Author or Editor: JC Christensen x
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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.
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.
The authors provide a detailed description of effective surgical techniques for painful plantar skin lesions of the foot that are not amenable to simple excisional procedures. Modified unilobed and bilobed skin flaps are described, emphasizing step-by-step design and procedure performance. These advanced techniques offer numerous advantages over other excisional and flap methods, such as being reproducible and yielding predictable results.
The authors investigated various factors that affect stiffness of screw fixation in the oblique first metatarsal osteotomy. One screw versus two screw fixation with intact medial cortical hinge, and two screw fixation without hinge were tested on the same metatarsal specimen. Mechanical properties of the fixation patterns were measured on a materials testing apparatus. Each metatarsal was tested at below failure threshold for stiffness within the elastic range of the specimen. Load versus displacement curves and fixation stiffness values were generated for axial loading, valgus torque, and plantar-to-dorsal cantilever bending. Osteotomies with an intact hinge demonstrated superior stiffness in most parameters as compared to osteotomies without a hinge. Two screw fixation with intact hinge showed significantly increased axial stiffness as compared to one screw fixation. There was no statistical difference between one and two screws in cantilever bending and torsional stiffness with an intact hinge. The major stabilizing factor of the first metatarsal base osteotomy is the medial cortical hinge.
The weightbearing biomechanics of the tarsus with and without subtalar joint arthroereisis was investigated in 11 fresh frozen cadaver specimens using a three-dimensional (3-D) radiowave tracking system. Specimens, consisting of the distal half of the tibia and fibula and the intact ankle and foot, were mounted on a nonmetallic loading frame test system that allowed positioning of the foot to simulate midstance position of gait. The tibia was axially loaded to 756 N (one bodyweight) with 15% of the total load diverted through the fibula. Receiving transducers were attached to the talus, navicular, calcaneus, and cuboid bones. Tarsal movements were monitored as the specimen was loaded with and without subtalar joint arthroereisis. Three-dimensional data sets of osseous positions and orientations were collected and analyzed. Significant rotational differences were detected with and without subtalar joint arthroereisis for all four tarsal bones (p < or = 0.05). Tarsal translational position changes were small and not statistically significant.
