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Biomechanics of the foot and ankle
Published in Maneesh Bhatia, Essentials of Foot and Ankle Surgery, 2021
Sheraz S Malik, Shahbaz S Malik
The posterior tibial tendon is the key to performing a heel rise at push-off. It has a broad insertion on the navicular, tarsal bones and metatarsals. It acts to rotate navicular medially over the head of talus, which adducts transverse tarsal joint and inverts the heel. Hence, the posterior tibial tendon action initiates heel rise and brings the hindfoot in varus position, and the powerful Achilles tendon then takes over and holds the heel in inverted position. In posterior tibial tendon dysfunction the foot remains in a position of excessive pronation during weight-bearing, leading to adult-acquired flatfoot deformity. As the tendon loses function, increased stress is placed on supporting structures of medial longitudinal arch. The subsequent rupture of spring ligament and then failure of talonavicular joint results in collapse of the longitudinal arch and progressive abduction of the forefoot through transverse tarsal joint and progressive valgus deformity of the subtalar joint.16
The Kidney (KI)
Published in Narda G. Robinson, Interactive Medical Acupuncture Anatomy, 2016
Clinical Relevance: Dysfunction of the caudomedial soft tissues, including the posterior tibial tendon and flexor digitorum longus tendon, can lead to flattening of the medial arch of the foot, or pes planus.6 Posterior tibial tendon dysfunction also leads to a shift of the center of gravity toward the heel and medial aspect of the foot.
Biomechanical modelling and simulation of foot and ankle
Published in Youlian Hong, Roger Bartlett, Routledge Handbook of Biomechanics and Human Movement Science, 2008
Another study by Cheung and Zhang10 utilized the same model to investigate the load distribution and spatial motion of the ankle-foot structure with posterior tibial tendon dysfunction on intact and flat-arched foot structures during midstance. The musculotendon forces for the achilles, tibialis posterior, flexor hallucis longus, flexor digitorum longus, peroneus brevis and peroneus longus were applied at their corresponding points of insertion while the ground reaction force was applied underneath the ground support. Cadaveric foot measurements were generally comparable to the FE predicted strains of the plantar fascia and major joint movements. Unloading the posterior tibial tendon increased the arch deformations and strains of the plantar ligaments, especially the spring ligament, while plantar fasciotomy had a larger straining effect on the short and long plantar ligaments. The arch-flattening effect of posterior tibial tendon dysfunction was smaller than that of fasciotomy. It was speculated that fasciotomy and posterior tibial tendon dysfunction may lead to attenuation of surrounding soft tissue structures and elongation of foot arch, resulting in a progressive acquired flatfoot deformity.
Lateral collapse of the tarsal navicular in patients with rheumatoid arthritis: Implications for pes planovarus deformity
Published in Modern Rheumatology, 2018
Takumi Matsumoto, Yuji Maenohara, Song Ho Chang, Jun Hirose, Takuo Juji, Katsumi Ito, Sakae Tanaka
Some limitations of our study must be acknowledged. First, the prevalence of the MWD-like structural change might be underestimated in the present study due to its cross-sectional study design, with exclusion of patients who underwent previous mid- or hindfoot surgeries. Second, we evaluated only the shape of the tarsal navicular and the destructive and ankylotic changes at the talonavicular joints, and did not address the association with the soft tissues such as with capsular laxity, and weakened tendons or ligaments. For example, posterior tibial tendon dysfunction is considered to contribute to the development of pes planovalgus in RA patients [28]. By adding the element of soft-tissue involvement, specific characteristics will be further emphasized. Third, we did not include information about bone mineral density, or lower limb alignment in the present study, which might have some influence on the occurrence of tarsal navicular collapse. Fourth, we did not evaluate the forefoot abduction/adduction which is also one of the clinically important features in RA foot. Despite these limitations, we believe that the present study is important since it demonstrates that the prevalence of the MWD-like collapse of the tarsal navicular is not negligible in patients with RA, and that the MWD-like structural change leads to unusual pes planus deformity with hindfoot varus. Because the final fate of MWD is arthritic change around the tarsal navicular, several cases might be considered as just rheumatic joint destruction unless physicians are aware of this etiology.
Towards patient-specific medializing calcaneal osteotomy for adult flatfoot: a finite element study
Published in Computer Methods in Biomechanics and Biomedical Engineering, 2018
Zhongkui Wang, Masamitsu Kido, Kan Imai, Kazuya Ikoma, Shinichi Hirai
A healthy volunteer (Asian male, 38 years old, 178 cm, 70 kg) and a posterior tibial tendon dysfunction (PTTD) stage II patient (Asian male, 38 years old, 168 cm, 62 kg) with symptomatic flatfoot deformity were examined. Substaging of PTTD was done by Myerson’s classification (Myerson 1996). Two orthopedic foot and ankle surgeons diagnosed PTTD and flatfoot deformity based on clinical examinations and radiographs taken under loading conditions. We constructed FE models of the flatfoot and healthy foot. Both models were validated using experimental data of plantar stress during balanced standing. The healthy foot data were used as standards to compare with flatfoot data and evaluate surgical performance. Four surgical parameters of the MCO were investigated using simulations, and plantar stress distributions were quantitatively compared and discussed.