Charles H. Brown, Jr., M.D. “The 5- and 6-Strand Hamstring Tendon ACL Graft”
I’m going to switch gears and talk about hamstring tendon grafts.
Hamstring graft size does matter. Increasing the diameter of your hamstring tendon graft decreases revision and failure rate.
Reconstructions with grafts larger than 8 mm decrease the failures rate. Four-stranded graft is your traditional doubled gracilis and double SemiT [semitendinosus]. Four-stranded, I stopped in 2007.
We developed five- and six-stranded graft techniques.
Now we use about 90% six-stranded grafts. The five-stranded graft is a triple SemiT and a doubled gracilis. Typically, the femoral side is an average 8 mm. The tibial side is 8.5. If you use the technique I describe, you get a larger tibial end than femoral end. The six-stranded graft is a triple semitendinosus and triple gracilis and you can get 9 mm on the femoral and sometimes 9.5 on the tibia.
In your four-stranded graft, the diameter is 8 on the femoral side 6-7 on the tibial side. The distal end of the graft is attached to 5 mm Dacron tape. It’s the width of the tape that matters. The tape does not add to the strength of the constructs but still helps to compartmentalize the grafts. Tie the distal end of both the gracilis and the semitendinosus. You should use a high-strength suture. Proximal end is tied to a suspensory device.
Use an endobutton 15 mm fix loop. Tie this as hard as you can. The proximal end of the graft of the hamstring should be tied to the loop. Tie that to the loop and then tie the sutures from gracilis to semitendinosus together.
This gives you a continuous loop of hamstring graft. So, both grafts are now attached to the endobutton. Now the distal end is passed through the loop of the endobutton inside out and there is a loop through a loop. The distal end is passed through the loop you create and that triples the graft. The tape compartmentalizes the third strand, keeps it from falling out of the loop.
On the other side, the gracilis is doubled and now you have a six-stranded graft. It’s important to try to equally tension the graft so you can apply uniform tension.
Now the diameter is up from 8 mm to 11 mm on the tibial end and 10 mm on the femoral end. You’ve taken a small graft and significantly increased the diameter by doing this technique. Typically, you need about 25mm.
Tips: use a high strength of suture to whipstitch the ends. Polyester suture may break. Attach the proximal end to the loop and the distal end to the tape. This results in the tibial end being larger than the femoral end. A 24 cm length hamstring graft will allow adequate length. 25 for the femoral socket, 25 for the intra-articular length of the graft, and 30 mm for the tibial.
Data from ACL registry suggests higher infection rates for hamstring tendon autografts. The Vancomycin technique was introduced in Australia in 2008 has 0% infection. Four-millimeter gauze and 500 mg of Vancomycin. Wrap it and create a burrito and that decreases your infection rates.
In summary, hamstring grafts with a diameter of 8 mm or greater have lower failure and revision rate. Five- and six-stranded hamstring tendon grafts allow the surgeon to create a larger-diameter hamstring grafts compared to traditional four-stranded graft.
