in accordance with the present invention , a soft biological material is interposed between a bone fracture and the surrounding tissue . by way of example , a bone fracture may be sheathed with a piece of bioprosthetic material during surgical repair of damaged tendons or bones . the bioprosthetic tissue advantageously protects surrounding tissue from the deleterious effects caused by the irregular bone edges of the fracture , promotes free tendon and muscle gliding over the bone fracture site , and provides a suitable environment around the bone fracture to maintain the range of motion and flexibility of the repair area . surrounding tissue includes tendons , muscles , nerves , blood vessels , and the like . for purposes of illustrating the present invention , fig1 illustrates the insertion of bioprosthetic tissue around a fractured tibia . the bioprosthetic tissue is applied to the surface of the bone to interface between the area of fracture and the surrounding tissue , forming a barrier . the bioprosthetic tissue 1 is in sheet form and is inserted between the surface of the bone fracture 2 and the surrounding tendons 3 , muscle 4 , nerves 5 , blood vessels 6 , and other surrounding tissue . the bioprosthetic tissue can be free - floating and held in place by friction with the bone and surrounding tissue . alternatively , it may be secured to the bone by any suitable means such as cementing or attachment with surgical screws or staples . prior to application of the bioprosthetic material , displaced fractures are preferably set . in severe cases , bone grafting and other techniques may be employed . the bioprosthetic material not only isolates the bone fracture from surrounding tissue , thus inhibiting fibrous adhesions , but also promotes healing of the bone in a smooth , non - abrasive surface . the shape and dimensions of the bioprosthetic tissue will vary , depending upon the length and surface area of the bone fracture . generally , the shape is square or rectangular . in a preferred embodiment of the invention , the barrier has dimensions sufficient to cover the fracture surface , and which are sufficient to extend beyond the edge of the fracture surface a short distance as shown in fig1 . the bioprosthetic tissue is made of soft biological tissue , such as naturally occuring biological tissue derived from animal sources . suitable animal sources can include but are not limited to bovine , porcine , horse , sheep , kangaroo , or rabbit . the tissue may be obtained from various parts of the anatomy , as described below . alternatively , the soft biological tissue can be composed of collagen or reconstituted collagen substitutes including but not limited to collagen - fabric films , collagen membranes , reconstituted collagen on dacron ® mesh , tanned collagen sponge grafts and the like . in accordance with the present invention , the soft biological tissue barriers provide a moist , lubricious , and flexible interface between the irregular bony edges of the bone fracture and the surrounding tissue , and inhibits the formation of fibrous adhesions between the bone edges and the surrounding tissue . moreover , the soft biological tissue is stable and nonantigenic when placed into the body . in preparing the bioprosthetic material , naturally occurring biological tissue is removed from its host , defatted if necessary and processed by one of several well - known procedures used to prepare the tissue for implantation into humans . the tissue may be fixed ( tanned ) conventionally in from about 0 . 2 to about 0 . 6 weight percent glutaraldehyde in either phosphatebuffered solutions , or phosphate - free buffers as described in the copending u . s . patent application ser . no . 445 , 345 filed on nov . 29 , 1982 . the tissue handling conditions , as conventionally known , are not considered part of the present invention unless otherwise stated . likewise , tissue may be sterilized conventionally , using radiation or exposure to ethylene oxide , or by immersion in about 0 . 625 percent glutaraldehyde or from about 4 to about 5 percent formaldehyde . a particularly preferred sterilant is a combination of about 4 weight percent formalde hyde , about 22 weight percent ethanol and about 1 . 2 weight percent of a surfactant such as polysorbate 80 . naturally occurring biological tissue in accordance with the present invention includes , but is not limited to , epithelial and fibrous connective tissue such as pericardial tissue , dura mater , fascia lata , amnion , tendon , ligament , cartilage , and the like . the epithelial tissues such as dura mater , amnion , facia lata , and pericardium generally comprise two layers each ; a fibrous , proteinaceous layer and a relatively smooth membranous layer . in accordance with a preferred embodiment of the present invention , the rough , fibrous layer of the tissue is placed against the bone to provide better anchoring to the bone surface , while the smooth , membranous layer is directed toward the surrounding tissue and provides a more lubricious surface . in accordance with the preferred embodiment of the present invention , pericardial tissue which has been tanned with glutaraldehyde is employed as the interpositional bioprosthetic material . in accordance with a preferred embodiment of the present invention , the natural biological tissue is treated prior to implantation to render it substantially resistant to calcification . this treatment advantageously maintains the biological tissue in a more flexible state than calcified tissue , allowing the tissue to conform better to the uneven surface of the bone , and provides a softer surface to prompt better bone healing . calcification mitigation treatments of biological tissue are not considered part of the present invention but can be found in copending u . s . patent applications ser . nos . 445 , 345 filed nov . 29 , 1982 ; 377 , 747 filed may 13 , 1982 ; now u . s . pat . no . 4 , 481 , 009 and 441 , 023 filed nov . 12 , 1982 ; and in u . s . pat . no . 4 , 323 , 358 . the following test demonstrates a significant reduction in fibrous adhesions between a bone fracture of a rabbit tibia and the surrounding tissues when using biologically inert material as a barrier between the bone and the surrounding tissue as compared to a control model . a trauma simulating a fracture was imparted to the tibia bone proximal to the tibia - ankle joint of a rabbit . a piece of glutaraldehyde - processed bovine pericardium having a shape and size sufficient to cover the fracture was applied to the surface of the bone fracture . bone fractures prepared as above in a control group of rabbits were not sheathed with any bioprosthetic tissue . a 62 % reduction in visually - observed fibrous adhesions on resected bone when using the bioprosthetic tissue was noted . in addition , free tendon gliding over the subjacent bone fracture was observed in the experimental group , whereas minimal free tendon gliding was observed in the control group . thus , the bioprosthetic tissue inhibited the formation of fibrous adhesions and increased the post - operative range of motion of the repair area . the present invention has been described in detail and with specific reference to its preferred embodiments ; however , it will be understood by those skilled in the art that modifications can be made thereto without departing from the spirit and scope thereof .
a method of treating a bone fracture which involves interposing a barrier layer of soft biological tissue at the interface of the bone and surrounding tissue .