Prosthesis (i.e. – artificial body members) – parts thereof – or ai – Implantable prosthesis – Bone
Patent
1997-05-01
1999-08-31
Willse, David H.
Prosthesis (i.e., artificial body members), parts thereof, or ai
Implantable prosthesis
Bone
A61F 240
Patent
active
059447575
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a total trochitero-acromial shoulder prosthesis, that is to say a prosthesis which is intended to treat the mechanical and rheumatic disorders of the shoulder, which are known in particular under the term ruptures of the cuff, or scapulo-humeral periarthritis.
It is recognized that these disorders are excessively frequent and that they lead to an unnatural articulation between, on the one hand, the arch formed by the acromion and the acromio-coracoid ligament, and, on the other hand, the trochiter and the muscles which have their insertion there and which are then gradually destroyed.
This false articulation is painful and leads to premature restriction of the movement of the humerus in relation to the scapula.
The present invention aims to restore this freedom of movement of the shoulder and to eliminate the pain due to the aforementioned disorders, it being understood that the mechanical articulation of the shoulder, that is to say the gleno-humeral articulation, is unaffected.
The patent FR-A-2 418 644 has already proposed a prosthesis comprising two elements, namely: a trochiterian element having the shape of a spherical sector equipped with means for fastening to the site of the trochiter which has been sectioned beforehand, and an acromio-coracoid element having substantially the shape of a cylindrical or spherical segment intended to constitute an artificial articular arch by fastening, via one of its ends, to the coracoid apophysis, and via its other end to the lower face of the acromion, in such a way as to cover the aforementioned trochiterian element, its axis passing through the centre of the gleno-humeral articulation.
Total shoulder prostheses have also already been proposed, such as those described in the patent U.S. Pat. No. 4,550,450, in which a trochiterian prosthesis cooperates with a glenoid prosthesis and an acromial prosthesis placed under the end part of the acromion, and whose main length extends transversely towards the resectioned end of the clavicle. Such a prosthesis affords a function substantially identical to that described in the aforementioned French patent or in the patent FR-A-2 541 890, in which a single acromio-glenoid prosthesis serves as a seat for the trochiterian ball.
In order to move the humeral head downwards during abduction of the humerus in the glenoid cavity of the scapula, it has already been proposed that the trochiterian element in the shape of a spherical sector be off-centred laterally with respect to the centre of the humeral head or the glenoid cavity, in such a way as to bear under the acromio-coracoid element during abduction of the humerus by acting as a cam and effecting a concomitant lowering of the head of the humerus during the abduction.
However, in a number of cases, and particularly in cases of absence or total inefficiency of the periarticular or capsular muscles, which normally effect an active downward movement of the humeral head in the event of abduction or elevation of the arm, the prosthesis, and consequently the bone tissues supporting it, may be subjected to very high stresses, which may be damaging in the long term.
The present invention proposes to solve this problem in the case where the pulley effect of the elevator muscle heads of the deltoid muscle is, in view of the aforementioned stresses, insufficient to effect a suitable lowering of the humeral head during contraction of the deltoid muscle.
The prosthesis according to the invention comprises two elements, namely: a trochiterian element, for example of the type described in the patent FR-A-2 418 644, having the shape of a convex spherical sector whose diameter is preferably equal to or less than that of the humeral head, and equipped with means for fastening to the site of the trochiter, and an acromial element having a bearing surface for the trochiterian element and equipped with means for fastening to the lower face of the acromion, in such a way as to cover the aforementioned trochiterian element, and whose dimensions are such that it rem
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patent: 5032132 (1991-07-01), Matsen, III et al.
patent: 5080673 (1992-01-01), Burkhead et al.
patent: 5593448 (1997-01-01), Dong
Medinov-Amp
Willse David H.
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