The anterior cruciate ligament (ACL) is a ligament in the knee that is important in maintaining stability in the knee. They can be torn in any age group, but tears more commonly occur in young adults who are active in sports.
One can tear the ACL when twisting the knee or landing badly after jumping. There is usually an instantaneous sensation of a ‘pop’, followed by pain and immediate swelling in the knee.
Left alone, the swelling and the pain usually subside after a few weeks, afterwhich one may experience symptoms of instability in the knee whereby the knee feels loose and may give way when pivoting on the knee.
Treatment of ACL injuries usually involve a course of physiotherapy to reduce the swelling, and to improve the flexibility, strength and function of the knee. In some patients, physiotherapy is sufficient to allow them to return to their normal activities.
In other patients however, an ACL-deficient knee may still have residual instability which hampers them from participating in sports or performing their job. In these patients, surgery may be necessary to improve their knee function.
The traditional surgical treatment for an ACL tear is an ACL reconstruction. This is usually a keyhole operation and involves taking a tendon from the thigh or from a deceased donor, and utilizing that tendon to create a new ACL in the knee.
If the tendon is taken from the same patient, this is known as an autograft. A tendon that is taken from a deceased donor is known as an allograft.
Autografts are commonly taken from the hamstring tendons, or from the patella tendon (knee cap tendon). Some patients choose not to sacrifice their own tendons and hence choose to use an allograft. Using an allograft carries with it a slightly increased risk of infection as well as graft rupture.
The risk of rupturing an allograft can be as high as 26% in the first 10 years after surgery, compared to the risk of rupturing an autograft which is under 10%.
The typical time for rehabilitation after surgery is 9 months before a patient is cleared to return to sports.
During this period, it is important for patients to comply with physiotherapy exercises and follow-up in order to avoid complications such as a weak and stiff knee.
The results of ACL reconstructions are generally good, with 80-90% of patients being satisfied with the operation. About 80% of patients will go back to some form of sports, although only around 65% may return to their previous level of sports. Only 55% will return to competitive sports.
In a more recent review of elite athletes, 83% were able to return to high level sports after successful ACL reconstruction.
Increasingly, certain types of ACL tears are amenable to surgical repair with comparable results to the traditional ACL reconstruction. This involves stitching the torn ligament back to its attachment on the bone.
Patients who are suitable and undergo a repair usually rehabilitate faster than those who undergo the traditional ACL reconstruction. In addition, the repair operation is also a smaller procedure than a full reconstruction, thus avoiding excessive drilling of the bone.
The main concern with ACL repairs is the chance of the repair re-tearing and failing before the repair has healed. Should the repair fail, the patient may have to undergo another operation to formally reconstruct the torn ACL.
Remnant Preserving ACL reconstruction
In order to improve the functional results of an ACL reconstruction, some surgeons now try to preserve as much of the original ACL as they can. This is known as Remnant Preserving ACL reconstruction.
During this surgical procedure, the surgeon assesses the injured ligament and preserves parts of the original ACL that can be salvaged, and only reconstructs the parts that are irreparably torn. By preserving the original ACL, the surgeon tries to preserve the nerves and blood supply to the ACL.
This can equate to better graft healing and incorporation, and may help to reduce the chance of retearing the ACL. With preserved nerve function, the chances of successful return to sports may also be higher.
Remnant preservation ACL reconstruction
1) ACL Reconstruction Preserving the ACL Remnant Achieves Good Clinical Outcomes and Can Reduce Subsequent Graft Rupture, http://journals.sagepub.com/doi/full/10.1177/2325967113505076
2)Comparison of anatomic ACL reconstruction between selective bundle reconstruction and double-bundle reconstruction, https://link.springer.com/article/10.1007/s00167-013-2684-8
1) Clinical Outcomes of Arthroscopic Primary Repair of Proximal Anterior Cruciate Ligament Tears Are Maintained at Mid-term Follow-up, https://www.arthroscopyjournal.org/article/S0749-8063(17)31333-6/fulltext?mobileUi=0
2) Acute Proximal Anterior Cruciate Ligament Tears: Outcomes After Arthroscopic Suture Anchor Repair Versus Anatomic Single-Bundle Reconstruction. https://www.arthroscopyjournal.org/article/S0749-8063(16)30239-0/fulltext
3) Fifty-five per cent return to competitive sport following anterior cruciate ligament reconstruction surgery: an updated systematic review and meta-analysis including aspects of physical functioning and contextual factors.
4) Eighty-three per cent of elite athletes return to preinjury sport after anterior cruciate ligament reconstruction: a systematic review with meta- analysis of return to sport rates, graft rupture rates and performance outcomes.
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