Biologic and Mechanical Augmentation in Anterior Cruciate Ligament Reconstruction: Fibrin Clot Augmentation of 5-Strand Hamstring Autograft

Abstract

Hamstring autografts in anterior cruciate ligament reconstruction have an excellent clinical track record, but some patients have hamstring tendons that yield grafts of smaller diameter, which has been shown to be a significant risk factor for worse outcomes and graft failure. Some authors have advocated augmentation with allograft in these patients. Tripling the semitendinosus yields a completely autogenous 5-strand graft with a larger diameter but still of sufficient length. In addition, imaging studies still show signal heterogeneity within grafts, even autografts, after the healing process, which correlates with worse biomechanical properties. Recent animal studies have shown improved incorporation and better remodeling of soft tissue grafts with the use of an endogenous fibrin clot. We present our technique of biologic and mechanical augmentation of hamstring autografts with fibrin clot and a 5-strand graft.

Fig 1

Preliminary measurement of graft diameter. A preliminary measurement of graft diameter is obtained to allow the surgeon to drill the femoral and tibial tunnels while the graft is being prepared. Once fibrin clot and final sutures are placed, the femoral diameter will eventually be 0.5 mm larger than this preliminary measurement, and the tibial side 0.5-1.0 mm larger. (A) The surgeon holds the 2 limbs of suture from one end of the semitendinosus apart. (B) One third of the tendon is passed between the sutures, leaving 3 limbs that are evened out. This effectively triples the semitendinosus. (C) The gracilis is also placed through the 2 sutures, creating a 5-strand graft that is passed through the graft sizer using the 2 sutures of the semitendinosus.

Fig 2

Preparation of the tripled semitendinosus. To prepare a 5-strand graft, the semitendinosus must be tripled. It is important to even out all 3 limbs and secure it in such a way that all limbs are tensioned in the final construct. (A) The sutures on the semitendinosus are secured to the graft board. The other end is passed through the loop of the clamped sutures. After evening out the 3 limbs of the tendon, a no. 0 Vicryl (Ethicon) is placed through the folded end of the semitendinosus (white arrow) for traction while it is secured with another no. 2 Ultrabraid (Smith & Nephew) in a Krackow configuration, ensuring that the sutures grab both limbs of the folded portion of the graft (black arrow: free end of semitendinosus). (B) Once the appropriate-size EndoButton (Smith & Nephew) is chosen, it is secured to the graft board, and the short end of the semitendinosus is tied to the loop. The other end of the tendon is passed through the loop, again leaving a tripled semitendinosus (white arrow: single limb; black arrow: folded over limb). (C) The gracilis is also placed through the loop, leaving a 5-strand graft.

Fig 3

Incorporating a fibrin clot into the final graft construct is an easy, cheap method to improve the incorporation of the graft. (A) The anesthesiologist obtains 50 mL of venous blood and transfers it to a specimen cup on the surgical field. The blood is agitated to create a fibrin clot. This is accomplished one of 2 ways: stirring with a metal object for 10 minutes and placing a metal valve from an arthroscopic cannula into the cup and shaking for 5 minutes. (B) The cup is poured out onto a towel to soak up excess fluid, and the clot is gathered. It is placed between the limbs of the graft, and a circumferential suture is placed around the femoral and intra-articular portions of the graft to secure the clot and stabilize the limbs of the graft. (C) Final 5-strand hamstring autograft augmented with fibrin clot.