The objective of this study was to evaluate the conditions of ankle stability and the morphological and/or lesional factors in sprains that determine when instability becomes chronic. It is based on a review of the literature and the data from the 2008 Sofcot symposium. The biomechanics of the ankle cannot be reduced to a simple flexion-extension movement with one degree of freedom as characterized by the talocrural joint: its function cannot be dissociated from the subtalar joint, allowing the foot to adapt to the ground surface. Functional stability is related to the combination of the particular biometry of the joint surfaces and a multiaxial ligament system. The bone morphology of the talus, shaped like a truncated cone, explains the potential instability in plantar flexion; the radii of curvature of the talar dome have a variable mediolateral distribution: most often the medial radius of curvature is inferior to the lateral radius of curvature (66%), sometimes equal (19%), or inverted (15%). Joint kinematics, combining rotation and slide, can therefore be modulated by the talar morphology, explaining the occurrence of at-risk ankles. Ligament stability relies on the organization in three parts of the lateral collateral ligament and the specific subtalar ligaments: the cervical and the talocalcaneal interosseous ligament. The different injury mechanisms are largely responsible for the sequence of ligament lesions: the most frequent is inversion. The first ligament stabilizers correspond to the cervical and anterior talofibular ligaments; the talocalcaneal ligament, by its oblique orientation, is solicited when there is a dorsal varus-flexion component. In chronic instability, these mechanisms explain the onset of associated lesions (impingement, osteochondral lesions, fibular tendon pathology), which can play a role in instability syndrome. Ligament lesions determine laxity, characteristic of mechanical instability. Functional instability goes along with proprioceptive deficiency. There are postural factors such as varus of the hindfoot that favor instability. Knowledge of all these factors, often associated, will provide a precise lesional assessment and treatment adapted to the instability.
Adult flatfoot is defined as a flattening of the medial arch of the foot in weight-bearing and lack of a propulsive gait. The 3 lesion levels are the talonavicular, tibiotarsal and midfoot joints. The subtalar joint is damaged by the consequent rotational defects. Clinical examination determines deformity and reducibility, and assesses any posterior tibialis muscle deficit, the posterior tibialis tendon and spring ligament being frequently subject to degenerative lesions. Radiographic examination in 3 incidences in weight-bearing is essential, to determine the principal level of deformity. Tendon (posterior tibialis tendon) and ligamentous lesions (spring ligament and interosseous ligament) are analyzed on MRI or ultrasound. In fixed deformities, CT explores for arthritic evolution or specific etiologies. 3D CT reconstruction can analyze bone and joint morphology and contribute to the planning of any osteotomy. Medical management associates insoles and physiotherapy. Acute painful flatfoot requires strict cast immobilization. Surgical treatment associates numerous combinations of procedures, currently under assessment for supple flatfoot: for the hindfoot: medial slide calcaneal osteotomy, calcaneal lengthening osteotomy, or arthroereisis; for the midfoot: arthrodesis on one or several rays, or first cuneiform or first metatarsal osteotomy; for the ankle: medial collateral ligament repair with tendon transfer. Fixed deformities require arthrodesis of one or several joint-lines in the hindfoot; for the ankle, total replacement after realignment of the foot, or tibiotalocalcaneal fusion or ankle and hindfoot fusion; and, for the midfoot, cuneonavicular or cuneometatarsal fusion. Tendinous procedures are often associated. Specific etiologies may need individualized procedures. In conclusion, adult flatfoot tends to be diagnosed and managed too late, with consequent impact on the ankle, the management of which is complex and poorly codified.
Level IV. Retrospective therapeutic study.
With the continuous shrinking of transistor size, processor designers are facing new difÝculties to achieve high clock frequency. The register Ýle read time, the wake up and selection logic traversal delay and the bypass network transit delay with also their respective power consumptions constitute major difÝculties for the design of wide issue superscalar processors.In this paper, we show that transgressing a rule, that has so far been applied in the design of all the superscalar processors, allows to reduce these difÝculties. Currently used general-purpose ISAs feature a single logical register Ýle (and generally a Ðoating-point register Ýle). Up to now all superscalar processors have allowed any general-purpose functional unit to read and write any physical generalpurpose register.First, we propose Register Write Specialization, i.e, forcing distinct groups of functional units to write only in distinct subsets of the physical register Ýle, thus limiting the number of write ports on each individual register. Register Write Specialization signiÝcantly reduces the access time, the power consumption and the silicon area of the register Ýle without impairing performance.Second, we propose to combine Register Write Specialization with Register Read Specialization for clustered superscalar processors. This limits the number of read ports on each individual register and simpliÝes both the wakeup logic and the bypass network. With a 8-way 4-cluster WSRS architecture, the complexities of the wake-up logic entry and bypass point are equivalent to the ones found with a conventional 4-way issue processor. More physical registers are needed in WSRS architectures. Nevertheless, using WSRS architecture allows a dramatic reduction of the total silicon area devoted to the physical register Ýle (by a factor four to six). Its power consumption is more than halved and its read access time is shortened by one third. Some extra hardware and/or a few extra pipeline stages are needed for This work was partially supported by an Intel grant register renaming. WSRS architecture induces constraints on the policy for allocating instructions to clusters. However, performance of a 8-way 4-cluster WSRS architecture stands the comparison with the one of a conventional 8-way 4-cluster conventional superscalar processor.
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