Inquiry

A key challenge of developing soft tissue replacements is selecting a method for keeping them in place. Whether the implant is highly load-bearing (such as an artificial ligament) or only minimally (as in artificial cheekbones), implant migration is a serious issue. Because soft tissue replacements are typically made of compliant materials, implant fixation is particularly difficult. Tools such as screws or wires, commonly used in orthopedic implants, will only serve to damage these more delicate materials. Some typical methods for soft tissue replacements include suturing and encouraging tissue ingrowth into porous meshes. Are there ways to incorporate adhesives or less compliant materials for improved fixation?

Historical perspective and overview

Previous chapters in the clinical section of this textbook have described devices used to replace hard tissues (such as bone or teeth) and blood-interfacing implants (including vascular grafts and stents). Hard tissue replacements have their special challenges: for example, the need for a hip implant to be strong enough to withstand loading but have a low stiffness so as to reduce stress shielding. Blood-interfacing devices are required to provide structural support while preventing adhesion of platelets and without damaging blood cells. A third category of implant is soft tissue replacements. These can be further subdivided into mechanical supports (demanding a specific stiffness or strength as in sutures and synthetic ligaments), space fillers (primarily cosmetic implants, but also including artificial skin, which require compliance match and conformability), and highly specialized ophthalmic implants, which have further specifications related to their optical properties.