Flexible elongated chain implant and method of supporting body tissue with same

Abstract

Implants and methods for augmentation, preferably by minimally invasive procedures and means, of body tissue, including in some embodiments repositioning of body tissue, for example, bone and, preferably vertebrae are described. The implant may comprise one or more chain linked bodies inserted into the interior of body tissue. As linked bodies are inserted into body tissue, they may fill a central portion thereof and for example in bone can push against the inner sides of the cortical exterior surface layer, for example the end plates of a vertebral body, thereby providing structural support and tending to restore the body tissue to its original or desired treatment height. A bone cement or other filler can be added to further augment and stabilize the body tissue. The preferred implant comprises a single flexible monolithic chain formed of allograft cortical bone having a plurality of substantially non-flexible bodies connected by substantially flexible links.

Description

CROSS-REFERENCE TO RELATED APPLICATIONS [0001] This application claims priority to U.S. Provisional Patent Application No. 60 / 753,782, filed Dec. 23, 2005 and U.S. Provisional Application No. 60 / 810,453, filed Jun. 2, 2006, the entirety of each of which is incorporated by reference herein.FIELD OF THE INVENTION [0002] The invention relates to implants, and more particularly to flexible chain implants for augmenting or supporting bones or other structures, such as, for example vertebral discs. BACKGROUND OF THE INVENTION [0003] Vertebral compression fractures, as illustrated in FIG. 1, represent a generally common spinal injury and may result in prolonged disability. These fractures involve collapsing of one or more vertebral bodies 12 in the spine 10. Compression fractures of the spine usually occur in the lower vertebrae of the thoracic spine or the upper vertebra of the lumbar spine. They generally involve fracture of the anterior portion 18 of the affected vertebra 12 (as opposed...

AI Technical Summary

Problems solved by technology

Vertebral compression fractures, as illustrated in FIG. 1, represent a generally common spinal injury and may result in prolonged disability.

Until recently, doctors were limited in how they could treat such compression fractures and related deformities.

However, this procedure may not reposition the fractured bone and therefore may not address the problem of spinal deformity due to the fracture.

Moreover, this procedure requires high-pressure cement injection using low-viscosity cement, and may lead to cement leaks in 30-80% of procedures, according to recent studies.

In rare cases, however, polymethymethacrylate or other cement leaks into the spinal canal or the perivertebral venous system and causes pulmonary embolism, resulting in death of the patient.

Disadvantages of this procedure include the high cost, the repositioning of the endplates of the vertebral body may be lost after the removal of the balloon catheter, and the possible perforation of the vertebral endplates during the procedure.

Such a cement leak may occur through the low resistance veins of the vertebral body or through a crack in the bone which was not appreciated previously.

Other complications include additional adjacent level vertebral fractures, infection and cement embolization.

The cement may be forced into the low resistance venous system and travel to the lungs or brain resulting in a pulmonary embolism or stroke.

One drawback of this system, however, is that the mesh implant is not well integrated in the vertebral body.

This can lead to relative motion between the implant and vertebral body, and consequently to a postoperative loss of reposition.

This is primarily due to the limited applicability of xenografts, transplants from another species.

It is not always possible or even desirable to use an autograft.

Furthermore, the removal of material, oftentimes involving the use of healthy material from the pelvic area or ribs, has the tendency to result in additional patient discomfort during rehabilitation, particularly at the location of the material removal.

Grafts formed from synthetic material have also been developed, but the difficulty in mimicking the properties of bone limits the efficacy of these implants.

Additionally, the strain to failure of cancellous bone is about 5-7%, while cortical bone can only withstand 1-3% strain before failure.

It should also be noted that these mechanical characteristics may degrade as a result of numerous factors such as any chemical treatment applied to the bone material, and the manner of storage after removal but prior to implantation (i.e. drying of the bone).

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