Intra-Articular Landmarks for Anterior Cruciate Ligament Reconstructions: a Review

REVIEW Intra-articular landmarks for anterior cruciate ligament reconstructions: a review Although many factors influence outcome following anterior cruciate ligament reconstruction, recurrent instability is frequently linked to technical errors, most commonly tunnel malposition. Numerous anatomic landmarks have been described in order to aid in accurate tunnel placement. This article will review and summarize the current literature regarding intra-articular landmarks and their use in anterior cruciate ligament reconstruction. 1 KEYWORDS: anterior cruciate ligament n anteromedial bundle n lateral bifurcate Elcil Kaya Bicer , ridge n medial tibial spine n posterolateral bundle n Resident’s ridge Robert A Magnussen2, n retro-eminence ridge Matthias Jacobi2, Sebastien Lustig2, The anterior cruciate ligament (ACL) is one of the most frequent cause of recurrent instability, Elvire Servien2 the most important stabilizers of the knee joint. with tunnel malpositioning noted to be the most & Philippe Neyret† 1 It resists anterior tibial translation and serves as common error [17,18]. On the femur, tunnels are Specialist of Orthopedic Surgery & Traumatology, Ipekyolu Public a secondary restraint to internal tibial rotation often too anterior, leading to impingement in the Hospital, Van, Turkey [1–3]. ACL deficiency frequently leads to symp- notch and a loss of extension. Placement of the 2Specialist of Orthopedic Surgery & Traumatology, Centre Albert Trillat, tomatic knee instability, and is associated with femoral tunnel too far posterior can lead to graft Groupe Hospitalier Nord, Hospices both short- and long-term consequences, includ- laxity in flexion or excessive tension in extension. Civils de Lyon, Lyon-Caluire, France ing meniscal and articular cartilage lesions and Placement of the femoral tunnel vertically in the †Author for correspondence: Centre Albert Trillat, Groupe progressive osteoarthritic changes [4–6]. ACL notch may lead to decreased rotational control Hospitalier Nord, Hospices Civils de rupture is generally treated either operatively or and a persistent pivot-shift in some cases [17]. On Lyon, Lyon-Caluire, France nonoperatively depending on the patient’s symp- the tibia, the tunnel may be too far posterior, [email protected] toms, age, activity level and functional demands leading to a vertical graft that poorly controls [7–9]. Arthroscopically assisted reconstruction anterior translation, or too far anterior, leading techniques are frequently utilized in the surgi- to impingement of the graft in the notch dur- cal management of ACL ruptures. Numerous ing extension [19]. In order to achieve a successful techniques have been described and there is cur- long-term outcome, the surgeon must consider the rently no consensus as to which methods yield native ACL anatomy during ACL reconstruction. the best functional outcome, patient satisfaction The aim of this article is to present the current and long-term results. knowledge of the native attachment sites of the Currently, there is great interest in reproduc- ACL and the intra-articular landmarks for ACL ing the native anatomy when reconstructing the reconstruction. ACL [10,11]. There is debate regarding the need for double-bundle reconstruction. Double-bundle The anatomy & function of the ACL reconstructions have been shown to improve The ACL is an intra-articular but extrasynovial rotational stability in vitro [12,13], but improved ligament. Proximally, its origin is on the postero- clinical outcomes have not been demonstrated medial aspect of the lateral femoral condyle. It [14,15]. With all techniques, the ultimate goal follows an oblique course inferomedially until it in ACL reconstructive surgery is to restore the reaches its insertion site on the tibia, the anterior translational and rotational kinematics of the intercondylar fossa. native knee. Whether single- or double-bundle The ACL is frequently described as consist- ACL reconstruction is performed, adherence to ing of two functional bundles: the anteromedial the anatomic reconstruction concept seems to be (AM) bundle and the posterolateral (PL) bundle an important factor in achieving this goal [16]. [20]. They are named according to their relative Numerous factors affect outcome following insertion sites onto the tibia. There is, however, ACL reconstruction, but the most common conflicting evidence regarding the number of cause of revision ACL reconstruction is recurrent bundles that constitute the ligament. Odensten symptomatic instability [17]. Technical errors are and Gillquist reported that it was not possible 10.2217/IJR.10.97 © 2010 Future Medicine Ltd Int. J. Clin. Rheumatol. (2010) 5(6), 677–686 ISSN 1758-4272 677 REVIEW Bicer, Magnussen, Jacobi, Lustig, Servien & Neyret Intra-articular landmarks for anterior cruciate ligament reconstructions REVIEW to demonstrate separate bundles of the ACL in The size of the ACL is variable. Measurement histologic sections [21], while some authors have of the intra-articular length of ACL in cadav- described a third, intermediate bundle [22,23]. eric studies revealed that it had a range However, based on the findings of numerous between 22 and 41 mm, with a mean length cadaveric and fetal dissections, the majority of of 32 mm [23]. The ligament is broadest near authors agree on the presence of two functional its attachment sites and narrower in its mid- bundles [2,24–29]. substance [20]. The AM bundle is longer than The division of the ligament into functional the PL bundle, but the lengths and widths of bundles implies that each bundle is unique with the bundles are varied, subject to different respect to its tensioning pattern throughout the degrees of flexion [2]. range of motion of the knee. In extension, the AM and PL bundles are parallel and both are The femoral attachment site relatively taut (FIGURE 1A) [20]. With knee flexion, The ACL originates from the posteromedial a change in the spatial orientation of the bundles aspect of the lateral femoral condyle. The is observed. The AM bundle remains taut and orientation of the origins of the AM and PL crosses over the PL bundle, which relaxes with bundles relative to each other is dependent on knee flexion(F IGURE 1B) [2,20] . In situ biomechani- the degree of knee flexion. From an anatomic cal studies have demonstrated that when resist- point of view, the femoral origins are generally ing anterior tibial translation, the forces carried described with the knee in extension; how- by the PL bundle significantly increased as the ever, the arthroscopic view is not compatible knee was extended, whereas the AM bundle was with the anatomic descriptions since the knee exposed to an almost constant force at all degrees must be flexed to visualize the femoral origin of flexion. When resisting internal tibial rota- arthroscopically. In full extension, the origin of tion, the force transmitted by the AM bundle the AM bundle is located at the proximal por- both in 15 and 30° of flexion was found to be tion of the entire ACL footprint and the origin higher than that of the PL bundle. These find- of the PL bundle is located posterior and distal ings suggest that both of the bundles participate to the origin of the AM bundle (FIGURE 2A). With in the maintenance of the anteroposterior and knee flexion, the longitudinal axis of the ACL rotational knee stability [2,30,31]. attachment becomes more horizontal and the Figure 1. Anteromedial (light gray) and posterolateral (dark gray) bundles of the anterior cruciate ligament in a right knee. The bundles are parallel and taut in extension (A), while in flexion the anteromedial bundle remains taut and crosses over the posterolateral bundle (B). 678 Int. J. Clin. Rheumatol. (2010) 5(6) future science group REVIEW Bicer, Magnussen, Jacobi, Lustig, Servien & Neyret Intra-articular landmarks for anterior cruciate ligament reconstructions REVIEW Figure 2. Femoral and tibial attachments of the anteromedial (light gray) and posterolateral (dark gray) bundles of the anterior cruciate ligament in a right knee. Note the change in orientation of the femoral attachment sites relative to the tibia when the knee moves from extension (A) to flexion(B) . PL origin is located anterior and inferior relative of the femoral diaphysis in the sagittal plane to the AM origin when viewed arthroscopically was 34.9 ± 3.7° and the length of this ridge was (FIGURE 2B) [11]. measured as 15.5 ± 1.5 mm [35]. Numerous cadaveric and radiologic studies In a clinical study, Shino et al. investigated have been performed to describe the localiza- the utility of Resident’s ridge as an arthroscopic tion of the attachment sites of the ACL with landmark for anatomical femoral tunnel for respect to anatomic references [2,20,25,26,29,32– ACL graft [36]. It was shown that arthroscopic 34]. Concerning the femoral origin, the most identification of the Resident’s ridge was possible prominent bony landmark is the Resident’s without performing bony notchplasty, even in ridge (also known as the lateral intercondylar patients with chronic ACL insufficiency. The ridge). The Resident’s ridge is a thick bony arthroscopically measured distance between the ridge on the medial wall of the lateral femoral midpoint of this ridge and the posterior articular condyle (FIGURE 3A), which extends from a pos- margin was 7–10 mm. Postoperative evaluation terior–superior to anterior–inferior direction of these patients with 3D computed tomogra- from an arthroscopic point of view (FIGURE 3B). phy demonstrated that the mean length of the It constitutes the anterosuperior border of the Resident’s ridge was 18.8 ± 1.4 mm. The average femoral ACL attachment area, meaning that maximum distance measured between the ridge the ACL does not possess any fibers that attach and the posterior margin of the medial wall of antero superior to this ridge. The Resident’s ridge the lateral femoral condyle was 9.3 ± 0.8 mm, extends along the entire length of the femoral and the angle between the ridge and the axis of origin. Histologic ana lysis of fetuses ranging distal femoral diaphysis in the sagittal plane was from 19 to 22 weeks of gestation has demon- 31.1 ± 2.0°.

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