Three-dimensional motion of the toes with simulated contraction of individual toe flexors and extensors: A cadaver study.

BACKGROUND: The primary motion of the toes is flexion and extension. The motion results from activity of multiple muscles, and toe disorders may result from muscle dysfunction. The relationships of specific muscles related to toe function is underreported. The purpose of this study was to quantitatively evaluate three-dimensional toe motion resulting from specific muscle contraction using cadavers. METHODS: Three-dimensional joint movements of the 1st, 2nd, and 5th toe were produced by applying traction of individual muscles using six Thiel-embalmed cadaver legs. The traction increments were 3 mm, 6 mm, and 9 mm, during which the angle of the distal bone with respect to the proximal bone of each toe joint was measured using a magnetic tracking system. RESULTS: As tendon traction distance increased, the angular measure of the distal bone with respect to the proximal bone at each toe joint increased linearly and three-dimensionally. The flexor hallucis brevis significantly pronated and abducted the 1st toe compared to the extensor hallucis longus and brevis. The flexor digitorum brevis significantly supinated and adducted the 2nd toe compared to the flexor digitorum longus and quadratus plantae, while the extensor digitorum brevis demonstrated significant pronation and abduction compared to the extensor digitorum longus. CONCLUSIONS: Three intrinsic muscles produced significant toe motion in frontal and horizontal planes. Our results revealed that there was a proportional relationship between tendon excursion and joint angle, and an antagonistic relationship of muscles acting on the toes. These results can be considered regarding pathogenesis of toe disorders or deformity and regarding treatment such as exercise therapy or tendon transfer. LEVEL OF EVIDENCE: V, cadaveric study.

Comparison of the three-dimensional bone morphology of the first proximal phalanx and first metatarsal between normal and hallux valgus foot using the homologous model technique.

Bone morphology is one of the factors involved in hallux valgus development. However, previous studies have not evaluated the overall bone shape in three dimensions. This study aimed to compare the overall shape of the first proximal phalanx and first metatarsal in hallux valgus with those of normal feet.Homologous models were created from computed tomography data of the first proximal phalanx and first metatarsal of 75 healthy men and 53 women in the control group and 10 men and 71 women in the hallux valgus group. Principal component analysis was performed to examine the differences in bone morphology between the control and hallux valgus groups. In men and women with hallux valgus, the proximal articular surface of the first proximal phalanx was characterized by a more lateral inclination and torsion of the pronated first metatarsal. Additionally, the first metatarsal head was characterized by a more lateral inclination in male hallux valgus. This study is the first to reveal the morphological characteristics of the first metatarsal and first proximal phalanx in hallux valgus as a whole bone using a homologous model technique. These characteristics are considered possible causes of hallux valgus development. The shapes of the first proximal phalanx and first metatarsal in hallux valgus were different from those in normal feet. This finding should be useful when considering the pathogenesis and treatment development for hallux valgus.

Three-dimensional morphological variations in the calcaneus and talus in relation to the hallux valgus angle.

BACKGROUND: The present study aimed to clarify the morphological patterns of the calcaneus and talus that are associated with hallux valgus angle (HVA) by quantifying the differences in the hindfoot bone morphology between left and right sides in HV patients with clear bilateral difference of HVA. METHODS: Three-dimensional (3D) computed tomography scans of 32 feet of 16 patients with HV who had right-to-left HVA differences of more than 5 degrees (68.8 ± 8.6 years) were enrolled, and 3D surface models of the calcaneus and talus were generated. A total of 556 and 430 landmarks were placed on the calcaneal and talar surfaces, respectively, to calculate the principal components (PCs) of shape variations. The PC scores were compared between the small and large HVA sides within an individual. RESULTS: The calcaneus in patients with a larger HVA (mean, 43.2 degrees) possessed slender calcaneal tuberosity, more medially oriented posterior articular surface in the coronal plane, and narrower and more concave anterior-middle articular surfaces compared to those with a small HVA (mean, 33.7 degrees). The talus with a larger HVA exhibited more medially oriented talar head in the transverse plane and more anteriorly protruded lateral region of the talar head compared to the small HVA. CONCLUSIONS: The morphological patterns of the calcaneus in patients with a larger HVA allows the hindfoot bones to easily rotate in the everting direction, while those of the talus could induce a larger internal rotation of the first metatarsal. These morphological patterns of the calcaneus and talus could be structural factors affecting the HV.

Three-dimensional motion analysis of the hindfoot resulting from simulated contraction of individual lower leg muscles utilizing Thiel-embalmed cadavers.

BACKGROUND: Joint movement within the foot is complex involving multiple muscles. We evaluated three-dimensional movement of the hindfoot through simulated traction of extrinsic tendons of the foot. METHODS: Six Thiel-embalmed cadavers were utilized and thread was sutured to each tendon of the lower leg muscles. Traction of the thread was prescribed and the change of calcaneal position used to quantify foot motion was measured for each increment using a magnetic tracking system. RESULTS: As the tendon traction length advanced, the angle of the calcaneus with respect to the tibia increased linearly. Eversion and abduction angles due to extensor digitorum longus (EDL) traction were significantly greater than that due to the peroneus longus. Plantarflexion due to Achilles tendon traction was significantly greater than that of other plantarflexors. CONCLUSIONS: Our results demonstrated three-dimensional characteristics of hindfoot motion by simulated muscle contraction and importance of EDL as an evertor. These information should be applicable for tendon transfer procedures around the ankle and physical therapy for ankle dysfunction such as chronic ankle instability.