Surgical repair product comprising UHMWPE filaments

Abstract

The invention relates to an elongate surgical repair product comprising a cable of which bending stiffness can be lowered, which fibrous member is a heat-set cable comprising at least 50 mass % of high-performance polyethylene yarn. The product shows very high tenacity, combined with a relatively high initial bending stiffness that is significantly reduced upon bending or flexing the member, without significant dimensional change; and allows both easy and well-controlled handling and good knot tying characteristics. The invention also relates to a method of making said elongate product.

Claims

1. An elongate surgical repair product comprising a cable having an initial bending stiffness, wherein the cable exhibits a subsequent bending stiffness which is lower than the initial bending stiffness, the lower subsequent bending stiffness being obtained solely in response to bending of the elongate surgical repair product having the initial bending stiffness without removing a component thereof, wherein a ratio of the initial bending stiffness to the subsequent bending stiffness is in a range of about 3 to 10, and wherein the cable comprises at least 50 mass % of high-performance polyethylene yarn consisting essentially of a plurality of ultra high molecular weight polyethylene (UHMWPE) filaments, the cable having been heat-set under elongational tension at a heat-setting temperature between 140 and 151 C. but below a melting point of the UHMWPE filaments for a time period of 2-10 minutes to cause surfaces of the filaments in the cable to stick together sufficiently to increase the bending stiffness of the cable following heat setting while yet allowing at least a part of the filaments of the cable to separate from one another in response to bending thereby lowering the bending stiffness of the cable at a place of the bending.

2. The surgical repair product according to claim 1, wherein the high-performance polyethylene yarn has a tenacity of at least 2.0 N/tex.

3. The surgical repair product according to claim 1, wherein the cable is of a braided construction.

4. The surgical repair product according to claim 1, wherein the fibrous member comprises strands, and wherein the strands comprise at least 60 mass % of high-performance polyethylene yarn.

5. The surgical repair product according to claim 1, wherein the cable has a linear density of about 20-3000 tex.

6. The surgical repair product according to claim 1, wherein the heat-setting temperature is between 145 and 149 C.

7. A method of making an elongate surgical repair product according to claim 1, comprising the steps of: (a) assembling a plurality of strands comprising high-performance polyethylene yarn that substantially consists of a plurality of UHMWPE filaments and optionally strands comprising other fibrous materials to form a cable, and (b) subjecting the cable to a heat-setting treatment at a temperature between 140 and 151 C. but below the melting point of the UHMWPE filaments while keeping the filaments of the cable under elongational tension for a time period of 2-10 minutes so that the filaments in the cable stick together at their surface sufficiently to increase the stiffness of the cable while yet permitting at least part of the filaments to separate upon bending of the cable to thereby decrease the stiffness of the cable at a place of the bending.

8. The method according to claim 7, wherein the heat-setting treatment is carried out at a temperature between 145 and 149 C.

9. The method according to claim 7, wherein step (a) comprises braiding the plurality of strands.

10. The method according to claim 7, wherein keeping the filaments of the cable under elongational tension is performed by stretching the cable with a stretch ratio of from 1.05 to 3.0.

11. The method according to claim 10, wherein the stretch ratio is from 1.2 to 2.0.

12. A kit for a surgical method, comprising a sterile surgical repair product comprising a cable according to claim 1.

Description

EXAMPLES 1-3

(1) A braided cable was made as in Comp. Exp. A, and subsequently heat-set by feeding it into one end of a hot air oven kept at a constant temperature of 140 C., with a feeding rate of 2 m/min (controlled by feeding rolls). The cable trajectory in the oven was 8.4 meter, and the winding speed after exiting the oven at the other end was varied to result in stretch ratios of 1.11, 1.28 and 1.43, respectively. Properties were determined as indicated above; results are collected in Table 1.

EXAMPLES 4-7

(2) Examples 1-3 were repeated, with the oven temperature setting now being 151 C. Stretch ratios of 1.13, 1.34, 1.55, and 2.33 were applied, respectively. Results are also listed in Table 1.

(3) It can be seen that bending stiffness increases with increasing heat-setting temperature and applied stretch ratio. The heat-set cable shows an initial stiffness, that can be about 2-5 fold lowered upon bending the cable several times, and is then at a level similar to a non heat-set cable (normalized to cable titer). The heat-set cable also shows a higher level of residual stress in relaxation tests.

(4) TABLE-US-00001 TABLE 1 Residual stress Bending stiffness At 1 At 1 At 1.5 At 1.5 Dimensions Tensile properties ratio N/tex; N/tex; N/tex; N/tex; Titer Diameter Tenacity Modulus eab Initial After bending (initial/ 5 min. 10 min. 5 min. 10 min. Sample (tex) (mm) (N/tex) (N/tex) (%) (mm) (mm/tex) (mm) (mm/tex) after) (%) (%) (%) (%) Comp. 186 0.5 2.8 30 4.4 98 0.5 98 0.5 1 67 61 70 66 exp. A Ex. 1 168 0.46 3.4 111 3.3 252 1.5 63 0.4 3.5 77 73 79 75 Ex. 2 145 0.39 3.5 130 3.0 252 1.7 77 0.5 3.0 80 77 80 77 Ex. 3 130 0.27 3.3 134 2.9 244 1.9 71 0.5 3.4 78 74 79 76 Ex. 4 165 0.38 2.8 31 3.4 282 1.7 71 0.4 4.3 Ex. 5 139 0.36 3.3 121 3.0 300 2.2 89 0.6 3.7 Ex. 6 120 0.30 3.4 138 2.8 278 2.3 71 0.6 3.8 Ex. 7 80 0.18 3.5 168 2.5 208 2.6 83 1 2.6