TECHNICAL FIELD OF THE INVENTION

This invention relates to the field of knee prostheses for a femoral amputee, and more specifically to fully mechanical knee prostheses, that is to say devoid of any sensor or electronic control system.

STATE OF THE ART

In order to make it possible to simulate at best the articulation of a healthy knee, recent developments have sought to provide prostheses with sophisticated integrated electronic systems to determine and control the flexion of the tibial part with respect to the femoral part, based on position and acceleration data obtained from various sensors. One drawback of this type of solution is that it requires especially efficient processors to process the sensor data and implement relatively complex algorithms designed to ensure the stability of the wearer, all the while reproducing the most natural possible movement of the leg. Firstly, this type of solution turns out to be particularly cumbersome to systematically ensure a sufficiently short reaction time of the system; moreover, it consumes an appreciable amount of energy and requires a frequent replacement or recharging of electrical batteries intended to supply the system; lastly, any electronic failure could prove catastrophic for the prosthesis wearer.

Since the end of the 1960s, however, other types of prostheses have been known moreover which, in contrast, are fully mechanical, that is to say they do not require the use of any sensor or electronic system, and all the more so do not need any supply of electrical energy. These prostheses, using essentially a preferably hydraulic piston simulating the group of muscles associated in particular with the quadriceps, are often referred to as “swing & stance” prostheses, because they operate alternatively based on a so-called “stance” mode where the resistance to the flexion is high—and a “swing” mode, where the resistance to the flexion is reduced and the leg can thus more easily bend, for example when a step is taken, following the phase in which the leg is pushed and then brought forward. As explained in the scientific article: Mauch—Stance Control for AK Prosthesis, Bulletin of Prosthetics Research/Fall 1968, except for a voluntary blockage by the user in the stance mode of the prosthesis to avoid any disequilibrium, there exist several control mechanisms managing their alternating activation automatically in the context of normal movement, and notably the one based on the detection of the placement of the heel, referred to as “heel-control”, with a non-stance mode as the default, another based on the flexion of the foot and/or the detection of pressure on the front of the foot, called “toe-control”, with a stance mode as default, and finally one detecting the application of a compression force on the prosthesis, referred to as “weight control”, whose mode of operation is relatively close to that of the “heel control”. None of these mechanisms has been shown to be suitable, however, for descending stairs, which renders their use not very practical.

In order to alleviate this problem and improve comfort of use in the greatest number of real-life situations possible, including walking down stairs, another system, the so-called “hyperextension control” system has been proposed. This control mechanism is stance mode by default when a weight is applied on the prosthesis corresponding to the placing of the heel on the ground, but activates the swing phase when the leg is fully extended, namely when the tibial part is substantially aligned with the femoral part of the prosthesis. In other words, an unblocking making it possible for the leg to bend more easily is supposed to be theoretically possible at the end of the phase of pushing on the leg, but never at any other time. A re-extension of the leg is moreover permitted to carry out the normal swing motion of the tibial part of the leg, when a step is taken starting from a slightly bent position at the moment where the foot is no longer supported on the ground, thanks to the action of a valve which is intended to close only when weight is applied on the prosthesis and is therefore in an open position at that moment.

A drawback of this type of above-described prosthesis is that there exists however a risk of unblocking of the stance mode during an involuntary extension of the leg and which would risk in this case a fall.

Thus there exists a need for a solution without these known limitations.

SUMMARY OF INVENTION

One object of the present invention is to propose a prosthesis whose reliability is improved, all while keeping production and labor costs reduced.

According to the invention, these objects are achieved by means of a hinged connecting device for a prosthesis for a femoral amputee, and in particular a fully mechanical locking system, designed to permit the activation of the second operating mode—where the value of the resistance corresponds to a second minimal value, as opposed to the value of maximal resistance of the first mode of operation—only from a certain inclination of the said tibial part corresponding to a first predetermined oriented angle with respect to the vertical in the direction of walking.

An advantage of the proposed solution is that it provides a prosthesis which is not limited in terms of scenarios of use for everyday life and thus substitutes efficiently for the groups of muscles to be replaced or respectively emulated by the prosthesis.

Another advantage of the proposed solution is that it provides in parallel increased safety in terms of stability, notably when the heel strikes the ground when a step is taken, and more generally in any situation of potential disequilibrium of the wearer of the prosthesis.

Still another advantage of the proposed solution is that it provides, according to a preferred embodiment, a prosthesis of simple and modular construction, easily adaptable to the majority of existing pistons provided for prostheses of the “swing and stance” (SNS) type, without necessitating moreover structural modifications or important additional accommodations on the prosthesis.

According to a preferred embodiment, the secured switching device is furthermore adjustable, with a view to being adapted optimally to the movement of the wearer of the prosthesis and thus optimally ensuring stability when the heel strikes the ground.

