Kura, Hideji

Background: One factor believed to contribute to the development of hallux valgus is an abnormality in collagen structure and makeup of the medial collateral ligament (MCL) of the first metatarsophalangeal joint (MTPJ). We hypothesized that the mechanical properties of the MCL in feet with hallux valgus are significantly different from those in normal feet and that these differences may be related to alterations in the type or distribution of collagen fibers at the interface between the MCL and the bone. Materials and Methods: Seven normal fresh-frozen cadaver feet were compared to four cadaver feet that had hallux valgus deformities. The MCL mechanical properties, structure of collagen fibers, and content proportion of type I and type III collagen were determined. Results: The load-deformation and stress-strain curves were curvilinear with three regions: laxity, toe, and linear regions. Laxity of the MCL in feet with hallux valgus was significantly larger than that of normal feet ( p = 0.022). Stiffness and tensile modulus in the toe region in feet with hallux valgus were significantly smaller than those in normal feet ( p = 0.004); however, stiffness and tensile modulus in the linear region were not significantly different. The MCL collagen fibrils in the feet with hallux valgus had a more wavy distribution than the fibrils in the normal feet. Conclusions: In general, strong staining for collagen III and to a lesser extent, collagen I was observed at the interface between the MCL and bone in the feet with hallux valgus but not in the normal feet. These results indicate that the abnormal mechanical properties of the MCL in feet with hallux valgus may be related to differences in the organization of collagen I and collagen III fibrils.

Background: It is necessary to have an understanding of ankle and hindfoot motion and stability to accurately diagnosis and treat ankle-hindfoot disorders. Methods: We devised an ankle ligament testing apparatus to more critically determine ankle stability in all planes with a constant rotational force applied (inversion, eversion, internal rotation, external rotation) throughout the range of sagittal plane motion in 13 cadaver specimens. Three-dimensional kinematics were determined with a magnetic tracking device. Results: With inversion force applied, calcanealtibial inversion was greatest in maximal plantarflexion (mean 22.1 ± 6.0 degrees) and gradually decreased with dorsiflexion, which indicated that the ankle had the most inversion instability in plantarflexion. With eversion force applied, calcaneal-tibial eversion gradually increased with increasing dorsiflexion to 12.7 ± 7.4 degrees indicating that the most eversion instability was in dorsiflexion. With internal rotation force applied, calcaneal-tibial internal rotation from plantarflexion to neutral ankle position increased. With external rotation force application, external rotation from neutral to maximal dorsiflexion increased. Conclusions: Ankle laxity was not constant but varied depending on the plantarflexion-dorsiflexion position and the direction of the applied force. The degree of ankle laxity was greater with inversion and internal rotation torque. Variation in laxity between specimens was observed, consistent with previous reports. These data indicate that the ankle is less stable in plantarflexion when inversion and internal rotation forces are applied. This may explain why the lateral ankle ligaments are most prone to injury in this position. The ankle was less stable in dorsiflexion when eversion and external rotation forces were applied. This is consistent with the observation that deltoid ligament injuries occur in the neutral to dorsiflexion position. The study demonstrates the importance of examining patients with suspected ankle ligament injuries in several ankle positions. The ankle testing device has potential application for in vivo testing of patients with suspected ankle ligament instability.

Ligaments surrounding the hindfoot joints play an important role in hindfoot stability. This in vitro study investigated anatomical and biomechanical characteristics of nine major ligamentous structures, including length and orientation at neutral position and physiological elongation with the foot in five different positions relative to the neutral position. The results showed that ligament elongation depended on the ligament length, orientation in neutral position, and movement of bones to which they were attached.