Pertinent Insights On Biologic Matrices For Soft Tissue Repair

Andrew Rice, DPM, FACFAS, and Erin Mathews, DPM

Given the emergence of biologic matrices, these authors examine the biologic and biomechanical potential of these modalities in the lower extremity. They also offer a review of the current research on these therapies and provide a pertinent case study.

Recently in the healthcare field, the use of tissue biologic matrices has become part of the surgical mainstream. Currently in foot and ankle reconstruction, the matrices provide essential aids in tendon strengthening and are becoming much needed necessities in tendon repair. Advancements in the technology and application of tissue grafts improve the successful outcomes of elective and non-elective tendon surgical procedures.

   Traditionally, tendon repair has been met with great frustration even in the hands of the most skilled surgeons. This is particularly the case when surgeons see injured tendons with large gaps between ends and/or diseased tendon substance. In these situations, surgeons often question how to restore the native tissue adequately.

   Biological matrices were introduced into the orthopedic arena with the intention of improving clinical outcomes of tendon repair and restoration. When it comes to tendon reinforcement with biological matrices, there are two primary goals that are biomechanical and biologic in nature. First, the matrix should reinforce the repair site and provide strength to the tendon. Second, the matrix should integrate itself into the tendon and serve as a new tendon substance.

A Closer Look At The Biomechanical Properties Of Biologic Matrices

Clinically important biomechanical properties of these matrices include the ability to: resist gap formation, load share across the repair and increase the ultimate load to failure. Furthermore, the material’s suture retention strength is critical for a successful repair construct.

   Mechanical testing of various biologic matrices has shown that different processing conditions result in a wide range of mechanical properties.1 More recent biomechanical testing of Achilles tendon repair applications has shown that the dermis-based regenerative matrices Conexa (Tornier) and GraftJacket® (KCI) significantly increase the ultimate load to failure versus unaugmented controls. This testing has also revealed that Conexa decreases gap formation under cyclic loading and exhibits load sharing.2,3

   In regard to suture retention strength of different tissue matrices, the thickest is GraftJacket MaxForce Extreme.2,3 This is followed by Conexa and then the standard GraftJacket MaxForce. Cross-linked materials are noted to have reduced suture retention strength. Neither Conexa nor GraftJacket are cross-linked products.

Understanding The Regenerative And Reparative Potential

In addition to providing adequate biomechanical support, biologic grafts should support the regeneration of native tissue over time and simultaneously prevent acute or chronic reactions.

   Critical factors such as processing, sterilization methods, surgical technique, repair application and rehabilitative programs contribute to the success or failure of these matrices. Failure of the biological matrix or tendon repair is usually multifactorial but the underlying reason often is associated with the host response.

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