Q: Can you please explain to me the main reasons why people who have ACL reconstruction surgery end up rupturing the new ligament and having to start all over again?

A: Up to 10 per cent of all patients who have a primary (first) reconstruction of the anterior cruciate ligament (ACL) will experience a failed result. This could mean the graft failed/re-ruptured or it could mean the knee joint remained unstable after the reconstructive surgery.

Experts from the Mayo Clinic in Rochester, Minnesota suggest three reasons for ACL reconstructin failure. First, there can be post-operative complications such as infection, swelling, failure of the wound to heal, or failure of the graft "to take".

Second, there can be problems with the way the surgery was done. For example, tunnels are drilled through the lower aspect of the femur (thigh bone). The new graft material is passed through these tunnels and then attached to the bone. If the femoral tunnels are drilled too far forward or too far back, the angle of pull can be off, eventually leading to biomechnical problems and even graft failure.

And third, there can be some anatomic reasons for the less-than-satisfactory results. The alignment of the lower extremity may be a significant factor. In fact, malalignment of the leg results in uneven wear and tear on the joint. Damage to the meniscal or hyaline cartilage can contribute to the rupture of a primary ACL reconstruction.

There may or may not have been anything you did wrong that contributed to this unfortunate series of events. When patient factors are significant, it's usually one of several reasons. Overuse and trauma from participation in sports activities can be a major contribution. Patient noncompliance (failure to follow the surgeon's and thephysiotherapist's directions) is a potential risk factor for failure. And finally, according to a recent report from the Mayo Clinic, patients who are overweight (body mass index of 29 or higher) are more likely to rupture an ACL repair or reconstruction.

Your concerns are well-founded given that one in 10 patients who have ACL reconstructive surgery are going to have significant problems. Talk with your surgeon about your situation, your risk factors, and what you can do to prevent further complications in the future.

Reference: Timothy B. Griffith, MD, et al. Outcomes of Repeated Revision Anterior Cruciate Ligament Reconstruction. In The American Journal of Sports Medicine. June 2013. Vol. 41. No. 6. Pp. 1296-1301.