Expandable Absorbable Breast Implants for Reconstruction
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Solution Overview
Problem
Current methods for breast reconstruction following mastectomy, such as using acellular dermal matrices, are limited by resistance to stretching, high cost, and risks of disease transmission, and existing absorbable implants do not expand with tissue expanders, leading to patient discomfort and increased surgical complexity.
Innovation Solution
Development of absorbable and expandable implants made from poly-4-hydroxybutyrate (P4HB) polymers with sacrificial and non-sacrificial elements that allow for uniaxial and biaxial expansion, reducing stress on the pectoralis major muscle and enabling tissue ingrowth, which are completely absorbed in vivo, eliminating the need for additional surgical steps and reducing postoperative pain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If acellular dermal matrix (ADM) is used to cover the tissue expander, then the need to release and elevate multiple muscles is eliminated and postoperative pain is reduced, but the ADM resists stretching which puts undue stress on the pectoralis major muscle and can be uncomfortable for the patient
Solution Approach 1:
The implant is divided into two functional components: a non-absorbable mesh scaffold that provides structural support and stretching resistance, and an absorbable gelatinous material that provides compliance and allows expansion. This segmentation resolves the contradiction by assigning different mechanical properties to different parts of the same implant system.
Solution Approach 2:
The implant combines two dissimilar materials with complementary properties: a synthetic mesh (providing strength and stretch resistance) and absorbable gelatin (providing compliance and biocompatibility). This composite structure allows the implant to both resist excessive stretching and accommodate necessary expansion during tissue growth.
2Volume of moving object
If acellular dermal matrix (ADM) is used, then creation of a larger pocket size and more rapid expansion is enabled, but the ADM is very expensive
Solution Approach 1:
The implant uses absorbable gelatin that degrades over time (short-living), allowing the pocket to expand and be replaced with permanent implant tissue. This absorbable component is replaced by a permanent implant afterward, making the expensive ADM function temporarily and affordably.
3Reliability
If acellular dermal matrix (ADM) is used, then reduced incidence of capsular contracture formation and improvements in aesthetic results are achieved, but ADM is an animal or human derived implant with an associated risk of disease transmission
Solution Approach 1:
The absorbable gelatin component serves as a temporary barrier during the critical healing period (reducing capsular contracture), then degrades and is absorbed by the body. Since it's temporary and fully absorbed, disease transmission risk is minimized while maintaining the protective benefits during the vulnerable early period.
Solution Approach 2:
The implant's mechanical properties change over time as the absorbable gelatin degrades. Initially, it provides compliance and protection similar to ADM; as it degrades, the permanent implant tissue takes over the protective function. This temporal parameter change allows ADM-like benefits without long-term presence of animal-derived materials.
4Duration of action of stationary object
If existing absorbable implants are used, then complete absorption in vivo is achieved, but they do not expand with tissue expanders leading to patient discomfort and increased surgical complexity
Solution Approach 1:
The implant is segmented into an expandable mesh scaffold and an absorbable gelatinous filler. The mesh provides the expandable structure that moves with tissue expansion, while the gelatin provides the absorbable component. This segmentation allows both expandability and complete absorption to coexist.
Solution Approach 2:
The implant is designed to be dynamic rather than static. The mesh scaffold dynamically expands with tissue growth during the expansion phase, then the gelatinous material dynamically degrades and is absorbed over time. This dynamic behavior allows the implant to adapt to both expansion and absorption requirements.
Data Source
AI summary
Expandable absorbable implants have been developed that are suitable for breast reconstruction following mastectomy. The implants can be implanted in the vicinity of a tissue expander, for example, by suturing to the detached edge of the pectoralis major muscle to function as a pectoralis extender, and used to form a sling for a tissue expander. The implants, which permit tissue-ingrowth and slowly degrade, can be expanded in the breast using a tissue expander in order to form a pocket for a permanent breast implant. After expansion, the tissue expander can be removed and replaced with a permanent breast implant. The expandable implants help reduce patient discomfort resulting from tissue expansion, and avoid the need to use allografts or xenografts to create the pocket for the tissue expander. The expandable absorbable implant preferably comprises poly-4-hydroxybutyrate or copolymer thereof.