Authors’ Disclosure Statement: Dr. DiFelice reports that he is a paid consultant for Arthrex. Dr. van der List reports no actual or potential conflict of interest in relation to this article.
The gold standard of anterior cruciate ligament (ACL) injuries is currently single-bundle autograft reconstruction. However, many disadvantages of reconstructive surgery exist, such as: anterior knee pain, muscle atrophy, and loss of range of motion. In addition, native kinematics are not restored, and osteoarthritis is not prevented. Finally, revision surgery, if necessary, can be problematic due to tunnel widening, tunnel malpositioning, and preexisting hardware. Ligament preservation includes preservation of native tissues in order to optimize the biologic aspects, while decreasing the invasive nature of reconstructive surgery. In the 1970s and 1980s, ACL preservation via open primary repair was widely performed, but the technique was abandoned due to unpredictable results. Unfortunately, the influence of both tear location and tissue quality on primary repair outcomes was not adequately recognized. Augmented repair, essentially a combination of primary repair and reconstruction, was then performed in the 1980s and early 1990s. Despite excellent results, for multiple reasons the surgical community moved on to ACL reconstruction, which was adapted as the gold standard. With the current knowledge of the role of tear location and tissue quality on outcomes of ACL preservation, in combination with modern advances of magnetic resonance imaging, arthroscopic technology, and the benefits of early rehabilitation, there is likely a role for ACL preservation today. In this article, we (I) discuss the history of ACL preservation, (II) discuss how modern advances alter the risk-benefit ratio for ACL preservation, and (III) propose a treatment algorithm for ACL injuries that is based on tear location and tissue quality.
Injury of the anterior cruciate ligament (ACL) is very common with over 200,000 annual injuries in the United Status.1,2 There is a general consensus that these injuries should not be treated conservatively in patients that are younger, or who wish to remain active.3,4 Reconstructive surgery is currently the preferred treatment in these patients, and anatomic single-bundle reconstruction with autografts is considered the gold standard.5,6
Reconstruction of the ACL is, however, not a perfect treatment. Following single-bundle autograft reconstruction, revision rates of 3% to 8%,6-9 contralateral injury rates of 3% to 8%,10,11 and infection rates of 0.5% to 3%7,12,13 have been reported. Furthermore, due to the invasive nature of graft harvesting and the surgical procedure, 10% to 25% of the patients are not satisfied following ACL reconstruction.14,15 This can often be explained by common complaints, such as anterior knee pain (13%-43%), kneeling pain (12%-54%), quadriceps muscle atrophy (20%-30%),16,17 and loss of range of motion (ROM) (12%-23%).7,9,18,19 Furthermore, as a result of the invasive nature of reconstructive surgery, revisions can be difficult due to complications, such as tunnel widening, tunnel malpositioning, and preexisting hardware.20-22 This can lead to inferior outcomes and higher rates (13%) of revision surgery compared to primary reconstruction.23-26 Finally, reconstructive surgery does not restore native kinematics of the ACL,27-29 which may partially explain why reconstructive surgery has not been shown to prevent osteoarthritis.28-31
Over the past decades, there has been an increasing interest in the preservation of the ACL in an attempt to ameliorate these issues.32-37 Ligament preservation focuses on preserving the native tissues and biology, while minimizing the surgical morbidity to the patients.
Some authors have recently reported on arthroscopic primary repair of proximal ACL tears in which the ligament is reattached onto the femoral wall using modern-day suture anchor technology.32,38 Others have augmented this repair technique with an internal brace39,40 or with a synthetic device.33,41 When performing primary repair, it is believed that proprioception is maintained,42-44 while experimental studies have suggested that primary repair also restores the native kinematics,45 and may prevent osteoarthritis.46 Furthermore, primary repair is a conservative approach in that no grafts need to be harvested, no tunnels need to be drilled, and revision surgery, if necessary, is more analogous to primary reconstructions.32In patients with partial tears, some surgeons have advocated preserving the anteromedial (AM) or posterolateral (PL) bundle and performing selective single-bundle augmentation.34,35 In addition, several authors have used remnant tensioning36,47 or remnant preservation37,48 in combination with reconstructive surgery in order to benefit from the biological characteristics of the remnant. These techniques lead to better proprioceptive function,44,49,50 vascularization and ligamentization of the graft,50-52 provide an optical guide for anatomic tunnel placement,53 and decrease the incidence of tunnel widening.54,55The feasibility and applicability of these surgical techniques mainly depends on the tear type and tissue quality of the torn ligament. In this article we (I) discuss the history of ACL preservation, (II) discuss how modern advances alter the risk-benefit ratio for ACL preservation, and (III) propose a treatment algorithm for ACL injuries that is based on tear location and tissue quality.
History of ACL Preservation
The history of the surgical treatment of ACL injuries started in 1895 when Robson56 treated a 41-year-old male who tore both cruciate ligaments from the femoral wall. Performing primary repair with catgut ligatures, both cruciate ligaments were preserved and the patients had resolution of pain symptoms and full function at 6-year follow-up. Over the following decades, Palmer57,58 and O’Donoghue59,60 further popularized open primary repair for the treatment of ACL injuries, and this technique was the most commonly performed treatment in the 1970s and early 1980s.61-65 The initial short-term results of primary repair were excellent,61,62 but Feagin and Curl66 were the first to note that the results deteriorated at mid-term follow-up. Despite improvements in the surgical technique of repairing the ACL, such as the usage of nonabsorbable sutures and directly tying the sutures over bone,63,67 the results remained disappointing at longer-term follow-up.68-70
In response to these disappointing results, surgeons sought to improve the surgical treatment by either augmenting the primary repair with a semitendinosus, a patella tendon graft or an augmentation device,71-74 or by performing primary reconstruction.75-77 At the end of the 1980s and early 1990s, several randomized and prospective clinical trials were performed in order to compare the outcomes of these techniques.74,78-82 Many studies showed that results of augmented repair were more reliable when compared to primary repair, which led to the abandonment of primary repair in favor of augmented repair, and eventually primary reconstruction.65
