SURGICAL ARTICLE FOR ARTIFICIAL JOINTS

Abstract: The article comprises means to engage the humeral or tibial component of a shoulder or knee joint prosthesis and means adapted to accommodate at least part of the head of the humeral or tibial component, at least part of the said accommodating means being adapted to allow, in use in a joint, the ingrowth of soft tissue from around the joint. The article is woven from a polyester mesh.

Description: SURGICAL ARTICLE FOR ARTIFICIAL JOINTS SURGICAL ARTICLE The present invention relates to surgical articles used artificial joints. Shoulder replacement has been shown to be very successf for patients who have good soft tissues around the shoulde particularly in cases of osteo-arthritis and avascular necrosi However, in patients who have significant soft tiss deficiency, particularly patients who have defects of the rotator cuff (for example in rheumatoid arthritis unconstrained shoulder replacement has been unsatisfacto (Hirst _ Wallace (1986) 3rd ICSS). The Kessel constrain shoulder replacement is sometimes used in these situations but report by Wallenstein from Sweden at the 3rd ICSS indicat that, in a series of 24 shoulder replacements using the Kess constrained shoulder, there was serious concern about gleno loosening at the two to four year stage. There is, therefore, a need to find a method of stabilisi the unconstrained shoulder where the rotator cuff is deficient. In this specification, we shall refer to the tibial (in th case of a knee joint prosthesis) or humeral (in the case of shoulder joint prosthesis) component as the "head" component, i contradistinction to the natural or artificial socket component into the socket of which the head of the head component fits The head component (hemiarthroplasty) consists of a head and shaft portion, the shaft extending into the tibia or humeru when in use. In one aspect of the present invention, this is achieved b providing an article comprising means to engage the hea component of a knee or shoulder joint prosthesis and mean adapted to accommodate and extend beyond at least part of th head of the said head component in a direction generally awa from the shaft of the head component, at least part of the sai accommodating means being adapted to allow, in use in a joint the ingrowth of soft tissue from around the joint. The article can be used whether or not the socket of th joint is replaced by an artificial socket. Preferably, the article is generally tubular, having relatively wide open end which will accommodate the head of th head component and a relatively narrow open end which wil accept the shaft of the head component but not the head. Th open narrow end of the article thus constitutes the sai engaging means of the article and the wide open end constitute at least part of the head-accommodating means. The narrow en may be created by tapering the tube for all or (more preferably) part of its length. From a manufacturing point of view, it is advantageous the narrow end to be axial, whereas from a surgical point view it may be advantageous for the narrow end to be offset f the axis. Both embodiments are embraced by the scope of invention. The article is conveniently made from a surgically iner flexible fabric and is usually woven or knitted as a sing piece, either as a tube or as a flat piece which is sewn to fo a tube. The narrow end may be formed in the knitting process may be formed in a cutting and sewing step. "Dacron" (Reg T.M. , Du Pont) and "Terylene" (Regd. T.M. , ICI) are suitab polyester fibres . The material can be coated or impregnat with gelatin or another biodegradable material which ai integration of the material with the rotator cuff. The openness of the mesh is so chosen as to allow tiss ingrowth without being so open that the necessary structur integrity is lost. One skilled in the art will readily be ab to determine the optimum mesh parameters. Useful dimensions for the article, when used in a should joint, include a fabric thickness of 0.2-1.0 mm, a length 30.0-140.0 mm, preferably about 50.0-120.0 mm (eg 50, 60 or 7 mm), a wide end diameter of 20.0-60.0 mm, preferably about 30.0 50.0 mm (eg 38 mm) and a narrow end diameter of 5.0-20.0 m preferably about 13.0-20.0 mm (eg 16.0 or 19.0 mm). In general however, the dimensions are so chosen that the shaft, but no the head, of the head component may pass through the narrow end and the wide end will accommodate the head and, usually, part o the joint socket. Thus, the dimensions may differ according t the choice of head component, the patient and whether the join is the knee or shoulder. In use, the head component is inserted through the articl and into the bone, and the article is attached to the rotato cuff muscles and/or tendons by conventional surgical techniques ie (usually) by suturing. Although it is known to use fabrics into which tissue ma grow to strengthen joints, for example knee joints, these hav previously been attached to the leg bones, not to the prosthesi and to the rotator cuff. Particular examples of the invention will now be describe with reference to the accompanying photographs, in which Figure 1 to 6 show a very crude model of the article, knitted fro wool, Figures 7 to 12 show a less crude model, made fro "Dacron" , Figure 13 shows an actual article of the invention an Figures 14 to 17 show diagrams of a shoulder joint durin surgery using the article. More particularly: Figure 1 is a ventral view of a humeral component and th wool model; Figure 2 shows the article being slid up the shaft of humeral component; Figure 3 is a ventral view of the article in place; Figure 4 shows the medial side of the arrangement of Figu 3; Figure 5 corresponds to Figure 3 but shows the artic encompassing the socket of the scapula; Figure 6 shows the dorsal side of the Figure 5 arrangemen Figure 7 is a view of the narrow end of a simple cut-tu model of a Dacron article; Figure 8 is a perspective view of the wide end of t Figure 7 article; Figure 9 shows the Figure 7 article being slid up the sha of the humeral component; Figure 10 shows the Figure 7 article being pulled over t head of the humeral component; Figure 11 shows the article in place, from the back; Figure 12 is a view in the direction of arrow A in Figur li; Figure 13 is a plan view of a flattened Dacron article suc as might be used; Figure 14 shows a shoulder joint with a damaged rotato cuff; Figure 15 shows the joint with a 15 mm head humera component inserted into the humerus; in Figure 16, the head component is shown closer to th socket; and Figure 17 illustrates where the article of the inventio is located and attached to the rotator cuff. The humeral component 1 may be a standard Neer device wit either a 22 mm or 15 mm head 2, as is known (the dimension bein the distance shown as B in Figure 1) and a shaft 3. Th prototype 4 shown in Figures 2 to 6 is knitted from wool and ha a wide end 5 and a narrow end 6 with a hole 7. The model 10 shown in Figures 7 to 12 is a 30.0 mm inter diameter vascular graft, available from C R Bard I Billericay, Massachusetts, USA, which is cut to enlarge one 11 in order to accommodate the head of the humeral compon (approximately 42 mm for a 22 mm head). Figure 13 is a photocopy of an actual article 20 of invention in a sterile pack. A scale bar (50 mm) has be superimposed, and it can be seen that the diameter of the wi end 21 is about 32 mm, the diameter of the narrow end 22 about 10 mm, the length is about 106 mm and the length of t tapering section 23 is about 45 mm (measured along the taperi section itself). Table 1 gives this and alternati configurations. All dimensions are in millimetres. Version Narrow End Wide End Length Length of Diameter Diameter Tapering Portio The article 20 is made from Du Pont T56 Dacron (R.T.M. (polyethylene terephthalate) as a continuous seamless tubing warp-knitted on a double-bed Raschel knitting machine and the cut to length to give a truncated conical geometry with terminal aperture to accommodate the prosthesis. The stitc density can be 150-250 per sq cm, preferably 180-200, fo example 192 per sq cm. The elasticity is controlled by th choice of Dacron and the stitch density. The thickness may b 0.5-1.0 mm, for example 0.75 mm. The head component is inserted by known surgica techniques, for example those described in Neer et al , J. Bon Joint Surg. (Am) 1982, 64A, 319-337, Redfern et al International Orthopaedics (1989) 13, 61-63 or Kessel, Shoulde Surgery, Springer Verlag (1982) pp 39-44 (all of which ar incorporated herein by reference), the only difference bein that the shaft is passed successively through the wide end an then the narrow end of the article of the invention before bein inserted into the tibia or humerus. The article is placed deep lying on top of the head first. The rotator cuff is then place on top and secured by known methods to the article, for exampl by suturing with two rows of non-absorbable Ethibond No sutures, one proximal and one distal. Any excess amount of th wide end of the article may be cut off first. In cases where there is very little undamaged rotator cu tissue, it may be advantageous to use a 15 mm head instead of 22 mm head for the head component. Figure 14 shows a shoulder joint with a damaged rotat cuff 30. Figure 15 shows the joint with a 15 mm head humer component 31 inserted into the humerus 32 and replacing part the head thereof. The dotted line shows the extent of t natural head before removal. In Figure 16, the head compone 31 is shown closer to the socket and Figure 17 illustrates whe the article of the invention 33 is located and attached by w of sutures 34,35 to the rotator cuff 30. The narrow end 22' of the article and the immediate adjacent part of the article are not visible as they a sandwiched between the head 2 of the head component 1 and t tibia or humerus. The wide end 21' is visible. For simplici only two sutures 34,35 are shown. In practice, two rows o sutures may be provided, one distal and one proximal, or suture may be placed wherever convenient.

Claims: CLAIMS 1. An article for use in an artificial joint of the kin involving a head component comprising a shaft and a head, th article comprising means to engage the head component of shoulder or knee joint prosthesis and means adapted t accommodate at least part of the head of the head component an extend beyond the head in a direction generally away from th shaft, at least part of the said accommodating means bein adapted to allow, in use in a joint, the ingrowth of soft tissu from around the joint. 2. An article according to Claim 1 which is tubular, having relatively wide end through which the said head may pass and relatively narrow end through which the shaft of the hea component may pass but through which the said head may not pass 3. An article according to Claim 1 or 2, formed at leas partially of a flexible open weave fabric. 4. A kit comprising a head component of a shoulder or kne joint prosthesis and an article according to any one of th preceding claims. 5. A method of repairing a shoulder or knee joint, comprisin engaging an article according to any one of Claims 1 to 3 on th head component of a joint prosthesis, installing the sai component in place, locating the head of the component in t socket of the joint and joining at least part of the soft tiss surrounding the socket to the said article.

Inventors: WALLACE WILLIAM ANGUS, WALLACE, WILLIAM, ANGUS
Applicants: UNIV NOTTINGHAM, THE UNIVERSITY OF NOTTINGHAM
Application year: 1990
Main classification: A61F2
IPC codes: A61B19, A61F2