Bi-phasic compressed porous reinforcement materials suitable for implant

#The present invention relates to surgical devices for stabilizing, reinforcing and/or fusing adjacent tissue structures, and, more particularly, to porous and/or partially porous surgical devices for stabilizing, reinforcing and/or fusing the tissues in the fields of bone and soft tissue repair. Generally, this invention concerns internal fixation devices, particularly useful for spinal fusion and hernia repair.

#Spinal degenerative diseases (e.g., stenosis, disc disease, spondylosis, etc.), trauma, aging, or a herniated disc can cause compression in the spine thus applying pressure to the nerve roots and/or spinal cord. The compression produces progressive pain, loss of movement and sensation, and sometimes, permanent disability. Spinal fusion is among the standards of care for surgical decompression and stabilization of the spine. Fusion, known also as arthrodesis, is accomplished by the formation of an osseous bridge between adjacent motion segments. The goals of spinal surgery include relieving spinal cord/nerve compression, promoting spinal fusion, increasing stability, maintaining spinal alignment, and restoring disc height. Ideally, reconstructive surgery would result in total spinal fusion with an excellent clinical outcome.

#For over 40 years, removal of the problematic disc and fusion of the adjacent vertebrae has been the common treatment for degenerative diseases. The classical surgical procedure is discectomy and interbody fusion with an iliac crest autograft with or without internal fixation. A discectomy typically requires the removal of a portion or the entire intervertebral disc. Different types of grafts (e.g., autograft, allograft, or synthetic ceramics) are used to fill the disc space.

#FIGS. 1A and B illustrate the porous matrix material, including its pore structure, before (1A) and after (1B) being compressed.

#FIG. 2A illustrates the porous matrix material between two compressive devices.

#FIG. 2B shows the porous matrix material being compressed by the top compressive device.

#The object of the invention is an implantable prosthesis, constructed of a compressed porous polymeric material. The construction of the prosthesis is such that it is capable of absorbing energy and supporting large loads utilizing less mass of material than would be necessary in the formation of a solid polymer prosthesis. Additionally, the device has advantages over non-degradable solid implants, including the resorbable nature of the prosthesis, the ability to absorb biologically active materials, and the transient nature of its stress shielding.

#While working to create a low porosity material, a new and unique method to control or alter the porosity within a porous material was discovered. In an embodiment, the method for preparing the high-density porous matrix involves: a) creating a high porosity polymeric matrix by methods known in the art; b) inducing glass-transition within said porous polymeric matrix; c) applying a compressive force within one or more dimensions to achieve a new size or shape; and d) cooling the porous polymer out of the glass-transition wherein the polymer matrix maintains the new size or shape.

#Within this embodiment, steps b and c may be reversed such that the compressive force is applied and maintained then glass-transition temperatures are induced in said matrix.