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Evolving Concepts in Anterior Cruciate Ligament Surgery

By Suzanna Ohlsen, MD, Mia S. Hagen, MD

    • Physicians' Corner


Tears of the anterior cruciate ligament (ACL) are a common orthopaedic pathology, with an annual incidence of roughly 70 per 100,000 person-years in the United States38. Given the frequency of this injury, it is important for the treating surgeon to be aware of evolving techniques and concepts in ACL surgical management19, 24, 26, 38. The purpose of this review is to discuss the newest data on ACL reconstruction (ACLR) graft selection, lateral augmentation techniques, and ACL repair.

Graft Selection in ACLR

While bone-patellar tendon-bone (BTB) grafts have been the historical gold-standard in ACLR, there are established associations of BTB with harvest-site morbidity including degenerative joint disease and kneeling pain8,36. These concerns may be avoided through use of other grafts. For example, the quadrupled hamstring (HS) autograft has been shown to have equivalent patient reported outcomes and retear rate among a generalized cohort of patients, but confer a risk of saphenous neuritis during harvest, decreased maximum knee flexion strength, as well as concern for increased rotational and anterior knee laxity compared to that seen after BTB ACLR21, 2, 5, 50. While allografts inherently are not associated with donor site morbidity, these are expensive, have a low risk of immune reaction or transmission of disease, have slower incorporation times, and have a well-documented higher rate of re-rupture in younger patients compared to autografts12,21, 27, 35.

In the search for the ideal graft choice, quadriceps tendon (QT) autografts have been increasingly used and studied43. While older studies suggested biomechanical inferiority of the QT autograft, newer data have refuted this claim17, 34, 45. It has been shown that QT grafts result in both greater intra-articular graft volume and greater residual native tendon volume compared to that seen in BTB, but also that extensor mechanism strength is greater post-harvest in patients undergoing QT ACLR compared to those who underwent BTB ACLR1,51. Furthermore, QT autografts have demonstrated comparable patient-reported outcomes including International Knee Documentation Committee (IKDC) and Knee Injury and Osteoarthritis Outcome Score (KOOS), stability including side-to-side anteroposterior laxity as tested by a KT-1000/2000 arthrometer, functional outcomes, and lower donor site morbidity than both BTB and HS autografts10, 11, 23, 25, 31, 39, 43, 47. There are multiple techniques of QT autograft harvest, including bone plug and all-soft tissue methods, with no observed differences in patient-reported outcomes, stability testing, and graft rupture rates29, 41. The all-soft tissue QT harvest does result in a shorter graft length and thus relies on suspensory fixation techniques6. Further data are needed to evaluate the mid- and longer-term outcomes of QT compared to other graft choices, as well as to compare QT to BTB in young athletes, as HS autograft has been shown to have a 2.1 times higher rate of ACL graft revision compared to BTB in this high-risk demographic30.

Lateral Extra-articular Tenodesis

The ACL confers both anteroposterior and rotational laxity of the knee. Historically, there have been attempts at managing ACL tears with lateral extra-articular reconstructions alone42. This addressed the rotational component but did not address laxity in the sagittal plane and thus led to poor outcomes and early joint degeneration22. With the advent of arthroscopy and development of newer ACLR tools and techniques, the isolated extra-articular procedures were largely abandoned48. But increased research on ACL reconstruction has shown that non-anatomic, vertical femoral tunnel placement can result in poor rotational stability after intra articular ACLR. It has also been shown that despite anatomic tunnel placement in ACLR, rotational laxity can still persist as indicated by positive pivot shift test, suggesting that other anatomic variables contribute to rotational stability, such as the anterolateral ligament (ALL), menisci, and iliotibial band37, 9, 48.

Given possible limitations of ACLR, there is renewed interest in the addition of the lateral extra-articular tenodesis (LET) procedure in cases with a higher risk for retear, such as revision ACLR or primary hamstring autograft in young athletes28, 30. The STABILITY trial was a multicenter, prospective randomized clinical trial that compared HS ACLR with or without LET (modified Lemaire technique) in patients 25 years or younger who met two of three criteria: high-grade pivot shift [2 or 3], goal to return to pivoting sports, or generalized ligamentous laxity. Patients who underwent LET augmentation during ACLR had a 0.67 relative risk reduction of graft rupture over the two-year follow-up period16. Additionally, data have shown that during revision ACLR, in the absence of a clear cause of failure and the absence of meniscus or collateral ligament injury, LET augmentation reduces the incidence of positive pivot shift postoperatively and could reduce risk of graft retear46. There are biomechanical concerns of overconstraint with the LET or ALL procedures but clinically no differences have yet been found in terms of increased risk of degenerative joint disease18, 4, 40.

Multiple techniques for lateral extra articular reconstruction exist. The Lemaire procedure involves passing an ITB graft beneath the LCL, through a femoral tunnel, then back under the LCL to be attached to Gerdy’s tubercle via a tibial tunnel7. The modified Lemaire utilizes a shorter graft that is passed deep to the LCL and secured to the femur by a staple, negating the need for a transosseus tunnel and thus reducing risk of ACL femoral tunnel intersection. Older extra articular procedures include the Ellison, the Macintosh, the Arnold-Coker modification to the Macintosh, and the Losee procedures. Passing a graft superficial to the LCL may be more likely to over constrain internal rotation of the knee in deep flexion compared to passing the graft deep to the LCL20. There are also methods described in the literature for anterolateral ligament (ALL) reconstruction, such as the Smith, Helito, and Sonnery-Cottett, which all utilize hamstring tendon as the graft of choice, versus the Wagih procedure which percutaneously reconstructs the ALL with a polyester tape7.

ACL Repair

Historically, primary repair of ACL tears was abandoned because of high failure rates13. With expanding research on the pathophysiology and biology of midsubstance ACL tears, an alternative repair technique for management of midsubstance tears has gained popularity -- the bridge-enhanced ACL repair (BEAR), which utilizes suture repair augmented by a collagen and autologous blood scaffold to facilitate healing32, 33. Murray et al. demonstrated noninferiority of BEAR as compared to ACLR (including both BPTB and HS autografts) in terms of IKDC scores and side-to-side AP laxity at their 2-year follow-up, and showed that patients in the BEAR group had greater hamstring strength, which was statistically significant at all postoperative time points in the study3, 32. There was a higher rate of retear in the study (14% BEAR vs 6% ACLR) but this was not statistically significant. Research is ongoing to better understand the indications and mid- to long-term outcomes after the BEAR procedure44.


The field of ACL surgery continues to evolve. This review focused on updates in graft options, extra-articular reconstruction, and ACL repair. There is no firm conclusion on ideal graft choice, though newer data on quadriceps tendon autograft shows promise. It is reasonable to discuss options and utilize a patient-directed approach for graft selection, based on patient-specific factors. Anterolateral augmentation techniques such as LET can be beneficial in individuals at high risk of retear such as revision ACLR, youth athletes receiving hamstring autograft, and patients with high-grade pivot shift testing or extreme ligamentous laxity. Last, bridge-enhanced ACL repair could be noninferior to ACLR in specific populations although robust larger cohort analyses are needed to better understand the advantages and outcomes of this technique.


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