Exploring The Potential Of Acellular Dermis Grafts For Wound Healing And Soft Tissue Repair
Flowable/Injectable Versions Of Acellular Dermis Grafts
Several manufacturers have injectable pulverized acellular dermis graft versions that are indicated for tunneling wounds. Such grafts can provide an effective collagen medium for ingrowth of granular tissue. Careful application techniques are necessary for prevention of graft egress from the wound.
Tunneling wounds in the foot or ankle may indicate the presence of a deep chronic infection such as osteomyelitis. Communication of the wound with a joint or tendon sheath can allow for extensive drainage of synovial fluid, impairing the ability to heal even with grafting unless the deeper defect is closed. An appropriate workup including thorough clinical wound inspection, surgical exploration or radiographic imaging modalities is essential.
Pertinent Insights On Acellular Grafts For Soft Tissue Repair
An improved understanding of how these grafts enhance the healing process as well as seeing how these grafts have functioned in various clinical settings have helped allow the development of new graft applications. The inherent tensile strength of these grafts also allows successful use in the repair of tendons, ligaments and other structures where the graft helps augment the repair strength.5 7,12,13,18 The tensile strength of the graft varies according to graft thickness and size. For a standard thickness graft, Barber and colleagues have reported the tensile strength to be 182 N (range +/- 50N).18
For tendon repair, most authors describe repair techniques in which the tendon ends are first reapproximated and sutured in a Bunnell or Krakow fashion. The acellular dermis graft is then wrapped around the repair site and sutured to enhance the tensile strength.18-20 (Picture 3) Barber and colleagues found that Achilles tendon wrap repair in cadaver models had a failure point of 455 N versus 217 N for standard suturing.18 This added strength allows for earlier active tendon mobilization, which improves the rehabilitation.18,21 Appropriate aggressive use of heavy gauge sutures with adequate purchase of tendon and graft is advisable.18-20
In these standard cannoli-wrap techniques, the suture grasps the tendon. When a tensile force exerts itself along the tendon course, stress focuses on the tendon-suture interface as well as the suture-graft interface along the direction of the applied force. Thompson notes that the typical failure point is at the suture–tendon interface rather than the interface of the suture and the graft.22
Recently, techniques have been described where one weaves strips of acellular dermis graft through the tendon repair site. Such techniques then use the graft strip instead of suture to purchase (i.e. grasp) the tendon. In the “strip and shoelace technique,” one first re-approximates and repairs the Achilles rupture in a Bunnell technique under physiologic tension. Then inlay a 1 to 1.5 cm strip of the acellular dermis graft within the tendon across the repair site parallel to the tendon course and suture it. Then cut the remainder of the graft in a zigzag fashion to create a very long 0.5 to 1 cm wide strip. (Picture 4) Cut one end of the graft into a very thin, tapered tip and pass it through the eye of a large Mayo needle. (Picture 5) Then weave the graft like a shoelace up and down the repair site. (Pictures 6,7) One can cut the corners on the graft to allow for easier passage of the graft through the tendon.12