DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] In accordance with the present invention, a bone tissue treatment apparatus is provided for treating damaged bone tissue by application of reduced pressure (i.e., below atmospheric pressure) so that suction may be applied to a damaged bone tissue site in a controlled manner for a selected time period. As schematically shown in FIG. 2, a bone tissue apparatus includes a reduced pressure appliance, generally designated 200, which is applied to a damaged bone tissue site to treat the damaged bone tissue 224 through the application of reduced pressure. The appliance 200 is sealed in position over the damaged bone tissue site to create a generally-fluid-tight or gas-tight enclosure over the damaged bone tissue site.

[0015] The appliance 200 may include a substantially flat section of open cell polyester foam section 210 (Fischer Scientific, Pittsburgh, Pa. 15219) sufficiently large to cover a region surrounding the damaged bone tissue 224, a flexible hollow tube 211 (Fischer Scientific) inserted into the open cell foam section 210 and joined thereto with an adhesive and extending to attach at its opposite end with a Gast Vacuum pump (Fischer Scientific), and an Ioban adhesive sheet 212 (Minnesota Mining and Manufacturing, St. Paul, Minn. 55144) overlying the foam section 210 and tubing 211 and adhered to the tissue surrounding the damaged bone tissue, thus forming a seal that allows creation of a vacuum when the suction pump operates. Such an appliance 200 would most preferably be packaged in a sterile condition to ameliorate the need for sterilization of the apparatus prior to use. The adhesive sheet 212 may be packaged separately from the foam-tube assembly 210 and 211. A suitable wound treatment apparatus is also available from Kinetic Concepts International of San Antonio, Tex.

[0016] Referring to FIG. 1, a bone tissue treatment apparatus, generally designated 25, is depicted having a reduced pressure appliance 29 for enclosing a damaged bone tissue site to provide a fluid-tight or gas-tight enclosure over the damaged bone tissue site to effect treatment of a damaged bone tissue 24 with reduced pressure. The damaged bone tissue treatment apparatus 25 includes a reduced pressure appliance, generally designated 29, which is applied to and sealed over a damaged bone tissue site in order to enclose the damaged bone tissue site for treatment with suction or reduced pressure within a sealed generally fluid-tight or gas-tight enclosure. For the purpose of creating suction within the appliance 29, the appliance 29 is connected with a vacuum system, generally designed 30, to provide a source of suction or reduced pressure for the sealed appliance 29 at the damaged bone tissue site. The vacuum system 30 may include a suction device 31 and an optional fluid collection device 32 intermediate the hose 12 and suction device 31. The suction device 31 produces a source of reduced pressure or suction which is supplied to the reduced pressure appliance 29 by suction tubing 12. The fluid collection device 32 functions to collect any exudate that may be aspirated from the tissue. A stop mechanism 33 may be provided to halt application of the suction device 31 upon collection of a predetermined quantity of fluid in the fluid collection device 32. Interrupting the application of suction to the appliance 29 is desirable to prevent exsanguination in the unlikely event a blood vessel ruptures under the tissue cover 18 during treatment. If, for example, a blood vessel ruptures in the vicinity of the damaged bone tissue 24, a shut-off mechanism would be useful to prevent the vacuum system 30 from aspirating any significant quantity of blood from the patient. As a safety feature, various mechanical or electrical detection mechanisms may be employed to detect the level of exudate in the fluid collection device 32.

[0017] The appliance 29 includes a fluid-impermeable tissue cover 18 in the form of a flexible, adhesive, fluid impermeable polymer sheet for covering and enclosing the damaged bone tissue 24 at the damaged bone tissue site. The tissue cover 18 includes an adhesive backing 20 which functions to seal the tissue cover 18 to the attachment site 22 around the periphery of wound 24 to provide a generally gas-tight or fluid-tight enclosure over the damaged bone tissue 24. The tissue cover 18 must have sufficient adhesion to form a fluid-tight or gas-tight seal 19 around the periphery of the damaged bone tissue and to hold the tissue cover 18 in sealed contact with the attachment site 22 during the application of suction or reduced pressure.

[0018] The appliance 29 also includes a porous tissue screen 10 which is placed proximate the damaged bone tissue 24. The size and configuration of the tissue screen 10 can be adjusted to fit the treatment site. It can be formed from a variety of porous materials. The material maybe sufficiently porous to allow oxygen to reach the damaged bone tissue. The tissue screen 10 may be in the form of an open-cell polymer foam, such as a polyurethane foam, which is sufficiently porous to allow gas flow to and/or from the damaged bone tissue 24. Foams may be used that vary in thickness and rigidity, although it may be desirable to use a spongy material for the patient's comfort if the patient must lie upon the appliance during treatment. The foam may also be perforated to enhance gas flow and to reduce the weight of the appliance. As shown in FIG. 1, the screen 10 is cut to an appropriate shape and size to fit within a region about the damaged bone tissue 24. Alternatively, the screen may be sufficiently large to overlap the surrounding attachment site 22.

[0019] The appliance 29 also includes a suction port in the form of a hollow suction tube 12 that connects with the vacuum system 30 to provide suction within the sealed enclosure. The suction tubing 12 serves as a suction port for appliance 29. An end segment 12a of the tubing 12 is embedded within the foam screen 10 for providing suction or reduced pressure within the enclosure provided under the tissue cover 18. Embedding the open end of segment 12a of tubing 12 within the interior of the foam screen 10 permits the foam screen 10 to function as a shield to help prevent the tissue cover 18 from being inadvertently sucked into sealing engagement with the open end of the tube thereby plugging the tube 12 and restricting gas flow. The tube segment 12a embedded within the foam screen 10 may desirably include at least one side port 14 for positioning within the interior of the foam screen 10 to promote substantially uniform application of reduced pressure throughout the enclosure. Positioning the side port 14 of tube segment 12a within the interior of the foam screen 10 permits the foam screen 10 to function as a shield for the side port to thereby prevent the tissue cover 18 from being sucked into the side port 14 and thereby restricting gas flow. The open cells of the foam screen 10 facilitate gas flow throughout the enclosure. In addition, the foam screen 10 functions to hold the tissue cover 18 generally out of contact with the damaged bone tissue 24 during the application of suction within the enclosure.

[0020] Tubing 12 and tube segment 12a may be sufficiently flexible to permit movement of the tubing but are sufficiently rigid to resist constriction when reduced pressure is supplied to the appliance 29 or when the location of the damaged bone tissue 24 is such that the patient must sit or lie upon the tubing 12 or upon the reduced pressure appliance 29. The screen-tube assembly comprising the foam screen 10 and the tube 12 may be fabricated by snaking the end of the tube segment 12a through an internal passageway in the foam screen 10 such as by pulling the end of the tube segment 12a through the passageway using forceps. Alternatively, fabrication of the screen-tube assembly may be accomplished by suspending the end of the tube segment 12a into a suitable mold or form and then blowing foam into the mold or form to embed the tube end segment 12a within the blow-molded foam screen. The screen-tube assembly 12 and 10 is preferably prepared prior to use under sterile conditions and then stored in an aseptic package.

[0021] In order to use the reduced pressure appliance 29 at the site of the damaged bone tissue 24, the flexible, gas-impermeable, adhesive tissue cover 18 is secured in position at the damaged bone tissue site overlying the foam screen 10 disposed within the damaged bone tissue 24. The tissue cover 18 is secured and sealed to the surrounding attachment site 22 by an adhesive layer 20 on the under surface of the tissue cover 18 to form a gas-tight seal 19 around the periphery of the damaged bone tissue 24. The tissue cover 18 also provides a gas-tight seal around the tubing 12 at the feed through location 22a where the tubing 12 emerges from beneath the tissue cover 18. The tissue cover 18 is preferably formed of a fluid impermeable or gas impermeable flexible adhesive sheet such as Ioban, a product of the 3M corporation of Minneapolis, Minn.

[0022] Predetermined amounts of suction or reduced pressure are produced by the suction device 31. The suction device 31 is preferably controlled by a control device 44 such as a switch or a timer which may be set to provide cyclic on/off operation of the suction device 31 according to user-selected intervals. Alternatively, the suction device 31 may be operated continuously without the use of a cyclical timer. The control may also include a pressure selector to enable the amount of suction produced by the system to be adjusted so that a suitable sub-atmospheric pressure may be created within the chamber. Operation of the vacuum system 30 may be controlled to permit graduated increases in the amount of vacuum applied or graduated decreases in the amount of vacuum applied.

[0023] A method of treatment of damaged bone tissue in accordance with the present invention can be carried out by securing a reduced pressure appliance to the treatment site as previously shown and described, and then maintaining a substantially continuous or cyclical reduced pressure within the appliance until the damaged bone tissue has reached a desired improved condition. A selected state of improved condition may include formation of a neo-osteoid tissue. It may be preferable to change the appliance periodically, such as at 48 hour intervals, during treatment, particularly when using appliances incorporating a screen on or in the damaged bone tissue. The method is preferably practiced using a reduced pressure ranging from 0.01 to 0.99 atmospheres, and more preferably practiced using a reduced pressure ranging between 0.5 to 0.8 atmospheres. The time period for use of the method on damaged bone tissue may preferably be at least 12 hours, but can be, for example, extended for one or more days.

[0024] Supplying reduced pressure to the appliance in an intermittent or cyclic manner may also be desirable for treating damaged bone tissue. Intermittent or cyclic supply of reduced pressure to an appliance may be achieved by manual or automatic control of the vacuum system. A cycle ratio, the ratio of “on” time to “off” time, in such an intermittent reduced pressure treatment may be as low as 1:10 or as high as 10:1. For example, a useful ratio may be approximately 1:1, applied in alternating 5 minute intervals of reduced pressure supply and non-supply.

[0025] A suitable vacuum system for use in the method includes any suction pump capable of providing at least 0.1 pounds of suction to the damaged bone tissue, and preferably up to three pounds suction, and most preferably up to fourteen (14) pounds suction. The pump can be any ordinary suction pump suitable for medical purposes that is capable of providing the necessary suction. The dimension of the tubing interconnecting the pump and the reduced pressure appliance is controlled by the pump's ability to provide the suction level needed for operation. A ¼ inch diameter tube may be suitable.

EXAMPLE

[0026] A 61 year old male fell from a ladder while loading steel at his place of employment, sustaining an open pilon variety fracture on the right distal tibia and fibula and a nondisplaced tibial plateau fracture on the contralateral side. According to the referring surgeon, he was initially managed with a splint for his tibial plateau fracture and a surgical debridement of his open distal tibial (pilon) fracture with open reduction and internal fixation of the fractured fibula, reduction and percutaneous screw fixation of the portion of the fracture extending to the joint surface, application of dressings to the open fracture wound, and application of a long leg splint. This was followed four days later by a re-inspection and irrigation of the wound, cancellous bone grafting of the defect, and application of an external fixator (non-bridging hybrid variety with thin, tensioned wires distally.)

[0027] The patient was transferred to a rehabilitation facility, and orthopedics was consulted to evaluate his leg injury. At this time, the wound appeared red and was draining. A debridement and irrigation of the wound, including removal of the infected graft from the defect in the tibia, was undertaken with application of antibiotic beads as well as application of a vacuum assisted closure system as shown in FIG. 1. The vacuum system was placed at the wound site to form an enclosure about the tibial defect. The foam section was placed proximate the tibial defect but out of contact with the tibial defect. The foam section, however, could be placed in contact with the tibial defect if so desired. The vacuum was set to −125 mmHg pressure, that is 125 mmHg below atmospheric pressure. The patient utilized the system for approximately three and a half months, with the bulk of this time in the home setting. The foam section was changed at 48-hour intervals. The patient was placed on a course of culture directed intravenous antibiotics for six weeks while undergoing the vacuum treatment. The antibiotic beads were removed at one month following the initial debridement. During this time, he was evaluated for a free flap with the aim toward coverage of his wound whose base consisted of the defect in the tibia.

[0028] The patient had a long history of cigarette smoking (50 pack years), with chronic obstructive pulmonary disease and atherosclerotic distal leg vessels which made him a poor candidate for the procedure. At this point, the option of below knee amputation with early prosthetic fitting was recommended with the aim toward early functional restoration, but the patient refused this option. It was because of the contraindications to free flap coverage and the patient's refusal to undergo an amputation that the relatively prolonged vacuum treatment was elected and continued on an outpatient basis. Vacuum treatment was continued on an outpatient basis under the conditions mentioned above, with weekly follow-up visits to the patient's orthopaedic surgeon. Over the span of the subsequent six weeks, the metadiaphyseal defect of the tibia filled in with what appeared on the surface to be healthy granulation tissue which spontaneously epithelialized. One would anticipate a persisting nonunion in these circumstances. For the defect to have spontaneously healed with bone was not anticipated. The spontaneous formation of specialized tissue at the surface (epithelium) mirrored the spontaneous formation of specialized tissue at the level of the tibial defect (bone). The progenitor of bone in the defect was a neo-osteoid tissue whose formation was encouraged by the vacuum treatment.

[0029] The terms and expressions which have been employed are used as terms of description and not of limitation and there is no intention in the use of such terms and expressions of excluding any equivalents of the features shown and described, or portions thereof, but it is recognized that various modifications are possible within the scope of the claimed invention.