Lateral femoral tunnel preparation and graft fixation for anterior cruciate ligament reconstruction–A discussion

Abstract

This article provides a discussion and commentary around the recent advances in arthroscopic anterior cruciate ligament reconstruction (ACLR), with a focus on the aspects of lateral femoral tunnel preparation and graft fixation techniques. The paper explores and comments on a recently published review by Dai et al, titled "Research progress on preparation of lateral femoral tunnel and graft fixation in ACLR", while providing insight into its relevance within the field of ACLR, and recommendations for future research.

Key Words: Anterior cruciate ligament reconstruction; Arthroscopic surgery; Lateral femoral tunnel; Graft fixation techniques; Anterior cruciate ligament tear; Biomechanics; Knee injuries

Core Tip: Anterior cruciate ligament reconstruction (ACLR) is a highly complex surgery with multiple approaches. Decisions regarding the most optimal approach should be made with a comprehensive knowledge of the risks and benefits of each, in conjugation with patient factors, taking an individualized approach to each case. Future comparative research studies and large-scale interventional studies are needed to determine the optimal techniques for femoral tunnel preparation and graft fixation in ACLR.

TO THE EDITOR

The anterior cruciate ligament (ACL) is a strong band of connective tissue and collagenous fibers which aids to stabilize the knee joint in conjugation with the posterior cruciate ligament (PCL). A majority of ACL tears occur in athletes, with non-contact pivoting injury being a common mechanism, involving sudden deceleration with a change in landing motion[1]. ACL ruptures are additionally associated with multiple intra-articulate and extra-articulate injuries. Lateral meniscal tears are the most commonly associated injury with acute ACL ruptures[2].

Management of ACL rupture is guided by functional demands of the patients. Young patients and active older patients with complete ACL tears are managed with ACL reconstruction (ACLR). Additionally, in patients with high functional demand, partial tears that lead to instability can also be repaired via ACLR, or using an augmented suture of the ACL, if appropriate[3,4]. Reconstruction is done via an arthroscopic approach, involving preparation of the graft bed, tunnel positioning, and graft placement and fixation.

We read with interest, a review conducted by Dai et al[5], titled “Research progress on preparation of lateral femoral tunnel and graft fixation in ACLR”, which describes the intricate details of lateral femoral tunnel preparation and graft fixation[5]. It discusses a range of techniques and provides a comprehensive review of the advantages and disadvantages of each. This work aims to highlight the key points discussed within this article, while offering insights into the importance of these research findings.

Lateral femoral tunnel preparation

The review conducted by Dai et al[5], describes five techniques for preparation of the lateral femoral tunnel as part of ACLRs. These include the transtibial technique (TT), anteromedial approach (AM), outside-in technique (OI), over the top technology, and oval tunnel preparation. Dai et al[5], has highlighted the various options, while taking into account risks and anatomical variations, allowing for a more individualized approach to ACLR for patients. The OI technique was described as superior to TT and AM approaches, due to its ability to precisely locate the position of the femoral tunnel with the aid of an ACL locator, posing a lower risk of cortical fractures. This technique traditionally employs an ACL locator inserted into the AM femoral entrance, and a working entrance using an arthroscope anterolaterally.

Compared to the introduction of the arthroscope and instruments via anterior portals into the joint, a technical note by Yau[6] proposes the modification of the traditional OI technique by using an AM “viewing” portal, and a posterolateral (PL) “working” portal instead of the anterolateral approach. While preserving advantages of the traditional OI method, this would reduce overcrowding of the joint space and improve visibility. The risk of iatrogenic injury to the articulation cartilage of the lateral femoral condyle is also reduced due to the positioning of the instruments, relative to the arthroscope. It is to be noted that proper training of surgeons to perform the modified technique should take place to prevent additional risks such as common perineal nerve injury, and iatrogenic injury to the lateral collateral ligament. Other modifications to the OI technique have also been proposed, which include the use of the PL portal or a trans-septal portal as the “viewing” port[7,8]. Future comparative studies are required to determine the most optimal approach to the OI technique.

The AM approach for lateral femoral tunnel preparation has been considered superior to the TT technique due to the prospect of preparation of the femoral tunnel independent of the position of the tibial tunnel. The traditional TT technique has been modified (mTT) to allow for the creation of a femoral tunnel similar to the AM approach[9]. A network meta-analysis of 20 randomized controlled trials (RCTs) demonstrated the superiority of the anteromedial portal technique to traditional TT techniques, providing a better functional recovery, and higher levels of anteroposterior and rotational stability to the joint[10]. It also noted a greater incidence of graft rupture using the OI technique compared to standard TT techniques. Future large-scale RCTs are required to determine the efficacy of mTT over standardized approaches for femoral tunnel preparation.

Benefits of an oval-shaped tunnel compared to the conventional circular tunnel was also examined by Dai et al[5] The former technique has the prospect of better reproducibility of the anatomical attachment site for ACLR. This reduces bone loss and increases tensile strength of the replaced ACL. This was demonstrated by Wen et al[11], where the oval femoral tunnel technique resulted in better restoration of knee function and laxity, and more mature ACL grafts A recent study by Morales-Avalos et al[12], demonstrated variations in the morphology of the femoral ACL insertion with age. These findings should encourage the consideration of patient age, to avoid the assumption of specific morphology of the femoral footprint leading to inappropriate reconstruction techniques. With the current research, AM and OI techniques remain the standard of care for lateral femoral tunnel preparation in ACLR. However, it has been noted that the choice of procedure technique is usually surgeon-specific[13].

ACL bundle reconstruction

The review by Dai et al[5], also compared single-bundle (SB) and double-bundle (DB) ACLRs, with DB-ACLRs demonstrating potential to better restore the kinematics of the knee. However, DB-ACLRs pose a greater risk of graft fractures and knee osteoarthritis. SB-ACLRs have received preferential focus due to the potential of providing similar outcomes with lower levels of postoperative pain, and shorter recovery times. A bibliographic analysis of ACLR research over the last 20 years demonstrated an increasing trend in research around SB-ACLR, and a decreasing trend in publications about DB-ACLRs. It was speculated that factors regarding concerns around postoperative pain, and precision of tunnel placement has led to the shift of interest from DB-ACLR techniques to SB reconstruction, despite the theoretical advantages posed by DB reconstruction[14]. With several unanswered questions about the best method to restore normal knee biomechanics, methods have been compared in several studies to come to a consensus. A study by Ehlers et al[15], questioned the statistical stability of studies comparing DB-ACLRs and SB-ACLRs, after describing the Fragility Index (FI) and Fragility Quotient (FQ), which represented the number of events required to change the statistical significance of the data. Future comparative studies taking into account FI and FQ are needed, to produce statistically stable results for comparison of the two techniques.

Additionally, a recent systematic review has demonstrated the potential benefits of enhancement of ACLR grafts with suture tape (ST)-augmented grafts for ACLR have been associated with a significantly higher Tegner score, as well as a better ability to return to sports activity compared with standard ACLRs[16]. Despite the positive findings, more large-scale studies are needed to determine the benefits and indications for ST-augmented grafts for ACLR. The risk of foreign body reactions within the knee joint caused by wear particles should also be considered.

Femoral graft fixation techniques

The advantages and disadvantages of various femoral graft fixation techniques has also been discussed by Dai et al[5]. These include aperture fixation, cortical suspension, and transverse nail fixation. A network meta-analysis by Shah et al[17], compared femoral graft fixation methods and determined no statistically significant difference in techniques. Therefore, there is currently no superior method of femoral graft fixation. The lack of consensus of the best technique for graft fixation in ACLR demonstrates the need for an in-depth biomechanical understanding of graft fixation options and techniques in conjugation with an individualized approach to patient needs and factors[18].

Critical appraisal and conclusion

Dai et al[5], provided an excellent summary of the advances and options for various aspects of arthroscopic ACLR. It has provided a concise reference guide for specialists in ACLR and has effectively navigated the complexities of the evolving field. The review had a well-defined scope of lateral femoral tunnel preparation and graft fixation methods, allowing a comprehensive and balanced discussion of the various techniques, outlining the advantages and disadvantages of each. The lack of elaboration of the methods of the review, leave a lack of clarity of the process of the literature search and synthesis of the article. The article provided limited discussion on emerging technologies, such as the applications of three-dimensional printing for lateral femoral tunnel positioning in ACLR[19]. The article largely avoids drawing conclusions or recommendations for future research from the findings. In conclusion, the review by Dai et al[5], provides a comprehensive foundation for the understanding and critical evaluation of current practices in ACLR surgery.