Cadaveric flatfoot model: ligament attenuation and Achilles tendon overpull.
ABSTRACT Flatfoot deformity is characterized by loss of the medial longitudinal arch, forefoot abduction, hindfoot eversion, and often Achilles tendon contracture. Our objectives were to validate a cadaveric flatfoot model that involves selective ligament attenuation and to determine if Achilles tendon overpull is associated with increased pes planus severity. We measured the three-dimensional (3D) orientation of the bones of interest in the unloaded, loaded, and Achilles tendon overpull conditions. A flatfoot model was created by attenuating ligaments involved in the pes planus deformity followed by cyclic axial loading, and bone orientations were acquired in the three conditions. Significant differences seen between normal feet and flat feet were consistent with those seen with the pes planus deformity. The first metatarsal dorsiflexed and abducted relative to the talus. The navicular abducted relative to the talus. The calcaneus everted relative to the tibia. The talus plantar flexed and adducted. Achilles overpull resulted in first metatarsal-to-talus dorsiflexion and navicular-to-talus abduction. Thus, selective ligament attenuation followed by cyclic axial loading can create a cadaveric flatfoot model consistent with the in vivo deformity. Longitudinal arch depression, hindfoot eversion, talonavicular joint abduction, forefoot abduction, and talar plantar flexion were seen. Simulated Achilles tendon contracture increased the severity of the deformity, particularly in arch depression and forefoot abduction.
- SourceAvailable from: Theerawoot Tharmviboonsri[Show abstract] [Hide abstract]
ABSTRACT: Adult acquired flatfoot deformity is characterized by midfoot abduction and collapse of the medial longitudinal arch. Lateral column lengthening osteotomies primarily correct the abduction deformity, but the effects of graft shape on deformity correction and forefoot loading are unclear. Therefore, the purpose of this study was to demonstrate the effect of graft shape and taper on deformity correction and forefoot loading mechanics in a cadaveric flatfoot model.Foot & Ankle International 07/2014; · 1.63 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Following IRB approval, a cohort of 3-D rigid-body computational models was created from submillimeter MRIs of clinically diagnosed Adult Acquired Flatfoot Deformity patients and employed to investigate postoperative foot/ankle function and surgical effect during single-leg stance. Models were constrained through physiologic joint contact, passive soft-tissue tension, active muscle force, full body weight, and without idealized joints. Models were validated against patient-matched controls using clinically utilized radiographic angle and distance measures and plantar force distributions in the medial forefoot, lateral forefoot, and hindfoot. Each model further predicted changes in strain for the spring ligament, deltoid ligament, and plantar fascia, as well as joint contact loads for three midfoot joints, the talonavicular, navicular-1st cuneiform, and calcaneocuboid. Radiographic agreement ranged across measures, with average absolute deviations of <5° and <4 mm indicating generally good agreement. Postoperative plantar force loading in patients and models was reduced for the medial forefoot and hindfoot concomitant with increases in the lateral forefoot. Model predicted reductions in medial soft-tissue strain and increases in lateral joint contact load were consistent with in vitro observations and elucidate the biomechanical mechanisms of repair. Thus, validated rigid-body models offer promise for the investigation of foot/ankle kinematics and biomechanical behaviors that are difficult to measure in vivo.Annals of Biomedical Engineering 06/2014; · 3.23 Impact Factor
- [Show abstract] [Hide abstract]
ABSTRACT: Flatfoot is a foot condition caused by the collapse of the medial arch of the foot, and it can result in problems such as severe pain, swelling, abnormal gait, and difficulty walking. Despite being a very common foot deformity, flatfoot is one of the least understood orthopaedic problems, and the opinions regarding its optimal treatment vary widely. In this paper, an FE model of a flatfoot is proposed that is based on CT measurements. Surface meshes of the bones and soft tissue were generated from CT images and then simplified to reduce the node density. A total of 62 ligaments, 9 tendons, and the plantar fascia were modeled manually. Volume meshes of the different components were generated and combined to form the completed flatfoot model. A dynamic FE formulation was derived, and a balanced standing simulation was performed. The model was validated by comparing stress distribution results from the simulation to experimental data.08/2014; 2014:844-7.