Review of evolution of tunnel position in anterior cruciate ligament reconstruction

Table 1 Anatomy and evolution summary

Ref.	Study type	Results/conclusion
Petersen et al[1]	Anatomical	Describes the anatomy of ACL with histology. Describes definite landmarks of ACL attachments
Ferretti et al[2]	Cadaveric	The medial tibial eminence and the intermeniscal ligament may be used as landmarks to guide the correct tunnel placement in an anatomical ACL reconstruction
Schultz et al[8]	Histological	In this first histological demonstration of mechanoreceptors in human ACL, it seemed likely that mechanoreceptors provide proprioceptive information and contribute to reflexes inhibiting injurious movements of the knee
Schutte et al[9]	Histological	Three morphological types of mechanoreceptors and free nerve-endings were identified: two of the slow-adapting ruffini type and the third, a rapidly adapting pacinian corpuscle. Rapidly adapting receptors signal motion and slow-adapting receptors subserve speed and acceleration. Free nerve-endings, which are responsible for pain, were also identified within the ligament. These neural elements comprise 1 percent of the area of the anterior cruciate ligament
Adachi et al[11]	Histological	Positive correlation between the number of mechanoreceptors and accuracy of the joint position sense, suggesting that proprioceptive function of the ACL is related to the number of mechanoreceptors. Recommended preserving ACL remnants during ACL reconstruction
Georgoulis et al[12]	Anatomical and histological	In patients with an ACL remnant adapted to the PCL, mechanoreceptors exist even 3 yr after injury
Mae et al[17]	Cross over trial using cadaveric laboratory study	The ACL reconstruction via 2 femoral sockets using quadrupled hamstring tendons provides better anterior-posterior stability compared with the conventional reconstruction using a single socket
Strauss et al[24]	Descriptive laboratory study	During hamstring ACL reconstructions, the constraints imposed by a coupled drilling technique result in nonanatomic femoral tunnels that are superior and posterior to the native femoral insertion. Clinical relevance: Anatomic femoral tunnel placement during hamstring ACL reconstructions may not be possible using a coupled, transtibial drilling approach
Zavras et al[26]	Controlled laboratory study	Laxity was restored best by grafts tensioned to a mean of 9 ± 14 N, positioned isometrically and 3 mm posterior to the isometric point. Their tension remained low until terminal extension. Grafts 3 mm anterior to the isometric point caused significant overconstraint, and had higher tension beyond 80 degrees knee flexion
Musahl et al[30]	Controlled laboratory study	Neither femoral tunnel position restores normal kinematics of the intact knee. A femoral tunnel placed inside the anatomical footprint of the ACL results in knee kinematics closer to the intact knee than does a tunnel position located for best graft isometry
Siebold et al[18]	Cadaveric dissection Laboratory study	Clinical relevance: This study provides an anatomic description of the femoral AM and PL insertions including gender differences, landmarks, and arthroscopic orientation models for DB bone tunnel placement
Hefzy et al[31]	Cadaveric	Study found that altering the femoral attachment had a much larger effect than had altering the tibial attachment. The axis of the 2 mm region was nearly proximal-distal in orientation and located near the center of the ACL’s femoral insertion. Attachments located anterior to the axis moved away from the tibial attachment with flexion, whereas attachments located posterior to the axis moved toward the tibia
Hutchinson et al[34]	Cadaveric	The phenomenon of “resident’s ridge” is accounted for by a distinctive change in slope of the femoral notch roof that occurs just anterior to the femoral attachment of the ACL. The density change apparent at the time of notchplasty is probably caused by the transition between normal cortical thickness just anterior to the ACL and the cortical thickness of the ACL attachment. No distinctive increased cortical thickness can be identified as "resident’s ridge"-
Ferretti et al[35]	Histological and cadaveric anatomic study	The ACL femoral attachment has a unique topography with a constant presence of the lateral intercondylar ridge and often an osseous ridge between AM and PL femoral attachment, the lateral bifurcate ridge. Clinical relevance: These findings may assist surgeons to perform ACL surgery in a more anatomic fashion
Purnell et al[36]	Descriptive cadaveric study	Clinical relevance: Bony landmarks can be used to aid in anatomical anterior cruciate ligament reconstruction
Bernard et al[38]	Cadaveric anatomic study	By using this radiographic quadrant method combined with fluoroscopic control during surgery, authors were able to reinsert the ACL at its anatomic insertion site. This method is independent of variation in knee size or film-focus distance, easy to handle, and reproducible.
Colombet et al[40]	Cadaveric study	The Retro Eminence Ridge provides an easily identifiable and accurate reference point that can be used clinically. On a lateral radiograph, the positions of the tibial attachments can be referenced to Amis and Jakob's line. This method, different from Blumensaat's line, is independent of knee flexion
Amis et al[41]		A study of knee anatomy and graft placement concluded that the tibial attachment must be posterior enough to avoid graft impingement against the femur, and methods to attain this were presented

ACL: Anterior cruciate ligament; AM: Anteromedial; PL: Posterolateral.