Prof. N. Reha Tandoğan, M.D. - Asım Kayaalp, M.D.

What is a partial anterior cruciate ligament injury?

Anterior cruciate ligament (ACL) injuries usually involve the entire ligament in which all the fibers are torn. Surgery in these patients requires removal of all the remaining fibers and reconstruction of the ligament using a tendon graft. Less frequently, some of the fibers of the ACL may be un-injured and may remain undisturbed between the bone insertions of the ligament. This is called a partial anterior cruciate ligament injury. These patients may still require surgery, since the remaining fibers of the ACL are not enough to prevent the symptoms of instability.

What are the treatment options for partial anterior cruciate ligament injuries?

There are three options for the treatment of partial ACL injuries.

Primary repair: This involves sewing back the torn ligament form its insertion site using multiple sutures. This works only in a very small proportion of the patients, and is only suitable for acute peel-off injuries in adolescents, in which the body of the ligament is relatively intact. However, the outcomes are inferior to reconstruction using a graft tissue, probably due the plastic deformation the ligament undergoes before being torn.

Classical ACL reconstruction: This technique involves removal of all ligament remnants and reconstructing the ACL using a tendon graft and bone tunnels drilled into original ligament insertion sites. The proponents of this technique argue that the remaining fibers of the ACL do not have an important effect on healing and leaving the remnants might compromise tunnel locations.

Remnant preserving ACL reconstruction: Although the torn fibers of the ACL are removed, the undamaged fibers of the partially torn ligament are preserved in this technique. The ACL is reconstructed using a tendon graft again using bone tunnels, but the remnants of the ACL are preserved with special techniques (Video 1).

Video 1: Remnant preserving ACL reconstruction.

Is remnant preserving ACL reconstruction more difficult than classical techniques?

Remnant preserving ACL reconstruction might be more challenging than classical ACL reconstruction techniques. Special precautions are necessary to prevent damage to the remaining fibers of the ACL. An experienced knee surgeon is a must, since compromising on tunnel locations negates the positive effects of remnant preservation. The post-operative pain and recovery are no different than classical ACL reconstruction.

What are the advantages of remnant preserving ACL reconstruction?

Remnant preserving ACL reconstruction increases the strength of the reconstructed ligament and has positive effects on the healing and maturation of graft tissue. The tendon grafts using for ACL reconstruction are avascular (without any functioning blood vessels) at the time of implantation. These grafts are vascularized during the first year after surgery, with the body creating a healing response and covering the graft with new tissue and blood vessels. This process is called “ligamentization”. The preserved fibers of the ACL increase the vascularity (new blood vessels needed for healing) of the graft and prevent the leakage of synovial fluid into the bone tunnels which impedes healing. The preserved fibers of the ACL also increase the mechanical strength of the graft and may act as an internal brace to protect the graft during the ligamentization process. Some scientists also think that remnant preservation increased the ability of nerve endings to cover the newly forming ligament, thereby increasing proprioception (joint position sense). Proprioception is an important factor for successful return to sports.

Are the outcomes of remnant preservation ACL reconstruction better than classical techniques?

Excellent outcomes and a high rate of return to pre-injury levels of sports can be achieved with both techniques. However, in a comparative analysis of 7 studies, remnant preserving ACL reconstruction was found to have slightly better outcomes compared to classical techniques (Wang HD. J Orthop Surg Res. 2018;13(1):231). It is important to note that not all patients are suitable for remnant preservation, however when possible, these techniques should be employed to achieve better outcomes.

© Prof. Dr. Reha Tandoğan - Op. Dr. Asım Kayaalp