Hernia repairs are among the more common surgical operations which may employ a mesh fabric prosthesis. Such mesh fabric prostheses are also used in other surgical procedures including the repair of anatomical defects of the abdominal wall, diaphragm, and chest wall, correction of defects in the genitourinary system, and repair of traumatically damaged organs such as the spleen, liver or kidney.
The prosthetic surgical meshes can be implanted in either an open surgical procedure or through laparocsopic procedures (i.e. inserting specialized tools into narrow punctures made by the surgeon in the surrounding tissue).
Mesh fabrics as well as knitted and woven fabrics constructed from a variety of synthetic fibers can be used to form the mesh used in surgical repair. It is desirable for a surgical mesh fabric to exhibit certain properties and characteristics. In particular, a mesh suitable for surgical applications should have a tensile strength sufficient to ensure that the mesh does not break or tear after it is implanted in a patient. The mesh should also have a pore size which allows tissue to penetrate or “grow through” the mesh, after the mesh has been implanted into a patient. In addition, the mesh should be constructed so as to maximize flexibility. Increased flexibility helps the mesh mimic the physiological characteristics of the bodily structure it is replacing or reinforcing. An added benefit of increased flexibility facilitates the insertion of the mesh prosthesis into a patient during a surgical operation.
There are competing mesh design concepts one of which is whether to employ a heavyweight mesh with small pores or a lightweight mesh with large pores. The heavyweight meshes are designed to provide the maximum strength for a durable and persistent repair of the hernia. Heavyweight meshes are formed using thick fibers, tend to have smaller pores, and a very high tensile strength. However, the heavyweight mesh may cause increased patient discomfort due to the increase in scar tissue formation.
Lightweight, large pore meshes are better adjusted to the physiological requirements of the body and permit proper tissue integration. These meshes provide the possibility of forming a scar net instead of a stiff scar plate and therefore help to avoid formerly known mesh complications.
However, lightweight meshes have other drawbacks. First, they typically have a lower minimum tensile strength due to the smaller diameter of filament used and the “open” weave. This is also aggravated by the fact that such meshes are formed anisotropic and the differential between the tensile strength in any one of the directions of force can vary significantly. Another drawback to using lightweight meshes is that the anisotropic nature of the mesh has the tendency to cause the mesh to twist or deform when placed under tension, making placement more difficult.
Further, it is desirable for a surgical mesh fabric to have a tensile strength sufficient to ensure that the mesh does not break or tear after implantation into a patient. The minimum tensile strengths for meshes implanted for the augmentation and reinforcement of an existing bodily structure should be at least 16 N/cm. The tensile strength needed for meshes implanted to repair large abdominal hernias can increases to as much 32 N/cm.
These and other objects and advantages of the invention will become more fully apparent from the description and claims, which follow or may be learned by the practice of the invention.