Tuesday, July 30, 2013

New Concept in the Design & Manufacture of a Prosthetic Latticework.


The use of mesh has become essential in the repair of all hernias. To move forward into a new era of hernia mesh prosthesis  a panel of nine experts in hernia repair and experimental mesh evaluation agreed that new technologies and novel approaches must be investigated and designed.

The aim of this paper is to propose, a new concept in the design & manufacturing of a prosthetic latticework for inguinal, ventral or incisional hernia repair.

The 'smooth' side, having a small pore size, is placed adjacent to the bowel and resists tissue attachment.

The unique geometry of the lattice allows it to stretch in more than one direction and then return to its original shape. Existing hernia meshes are made of relatively stiff and inelastic material. The author strongly believes that these characteristics may be a contributing factor for recurrences and patient discomfort.
The proposed lattice easily assumes the conformity of the abdominal wall musculature anatomy and thus improves the long term comfort and well-being of the patient.

 The 'rough' side, with a more open pore size, is next to the tissues that surround the bowel where tissue incorporation is an advantage. Lattice cell size of 4mm (5/32nds) and thickness of 2mm (5/64ths). Lattice width of 150mm (6”).

The method of manufacture of this surgical lattice is using 3D printing technology. First, a three-dimensional structure is designed using CAD software. The porosity can be tailored using algorithms within the software. The lattice is then realized by using ink-jet printing of polymer powders or through Fused Deposition Modeling of a polymer melt.
The basic materials could be:
• ePTFE. (Expanded polytetrafluoroethylene) The use of ePTFE surfaces in hernia repair reduces adhesions and would reduce the recurrence rate.  This would be the first layer that is printed (smooth side down)
• Polypropylene. This material has been used for the past 20 years because of its stability, strength, inertness and handling qualities. Polypropylene is overprinted on the PTFE layer and provides the basic structure of the lattice.
• Collagen. A final layer of collagen is printed to encourage speedy host tissue incorporation into the latticework.

Potential attributes of lattice.
1. May result in the permanent repair of the abdominal wall, to reinforce and replace tissue for long-term stabilization of the abdominal wall.

2. Ingrowth characteristics that mimic normal tissue healing. May stimulate adequate fibroblastic activity for optimum incorporation into the tissues. May prevent adhesions. The ePTFE protects the edge of the lattice minimizing tissue attachment to the material.

3. Strong. May provide sufficient biomechanical strength to meet physiological requirements in order to permanently protect the fascial defect.

4. Pliable. It has elasticity in more than one dimension, allowing it to stretch in more than one direction and then return to its original shape. Easily assumes the conformity of the abdominal wall musculature anatomy.

5. Handling characteristics should be amenable to laparoscopic instruments.

6. The lattice may have an adequate adhesive quality that requires minimal or no additional fixation, even for large defects.

7. Non-allergenic.

8. Inert.

9. Non-biodegradable.

10. Non-carcinogenic.

11. Cuts easily without fraying.

12. The dimensions and mechanical properties of the proposed lattice can be tailored to provide an effective portfolio of hernia prostheses.

13. No shrinkage

CAD/CAM Technologies.
A number of different methods have been described in literature for preparing porous structures to be employed as tissue engineering scaffolds. Each of these methods presents its own advantages, but none are free of drawbacks.
Because most of the above techniques are limited when it comes to the control of porosity and pore size, computer assisted design and manufacturing techniques have been introduced to tissue engineering.