Over the years, surgical technique for the repair of a ruptured or deficient anterior cruciate ligament (ACL) has evolved and changed. Most recently, in the 1990s, surgeons went from using a two-incision tunnel to a one-incision technique. Results of each method have been studied and compiled.
The incisions are made to create tunnels through the bone. Graft tissue is threaded through the tunnels. Graft placement appears to be an important factor in the success of ACL repairs (single or double). The graft must be able to resist tibial translation (movement of the lower leg bone against the femur or thigh bone). It must also resist abnormal internal tibial rotation.
The repair can be done as a single bundle approach or a double-bundle procedure. Just as the term indicates, single-bundle is a piece of tendon taken from elsewhere around the knee (usually patellar tendon or hamstrings) and used to replace the deficient ACL. A double-bundle graft is more likely to be made of hamstring material. The double-bundle is formed by folding the graft over to form two layers of graft material.
The double-bundle graft was developed to provide greater stability. It was felt that a single-bundle graft led to too many failures. But the double-bundle graft is complex and requires two grafts and two femoral and tibial tunnels. There’s been some question about the failure rate for this approach compared with the single-bundle method.
It has been noted that a vertically oriented single-bundle ACL graft resulted in many more patients with too much knee instability (compared with patients who got the double-bundle graft). But there were other studies where there wasn’t much difference in results between these two procedures.
So, some authors advocated the simpler, less complex single-bundle procedure. Why go to all the trouble of using the double-bundle technique when the single-bundle works just as well and isn’t such a technically demanding operation?
In looking back at all of the studies (cadaveric and human), one method doesn’t appear superior over another. There are different advantages and disadvantages to each. It may be that the location of the graft is a key factor in results.
In some cases the orientation of a single-bundle graft can give the same stability provided by a double-bundle graft. The next step will be to conduct studies comparing locations of single-bundle grafts. The goal would be to find a single-bundle orientation that offers all of the advantages of a double-bundle approach without the complexities of technique.