Introduction 2 4 16 30 4 28 41 9 10 13 19 28 35 40 46 49 50 52 53 28 41 50 48 28 50 39 41 51 23 29 55 36 55 8 27 47 17 3 5 12 14 16 20 26 33 34 37 38 44 11 32 45 52 This study is aimed at acquiring quantitative geometric data of the ACL attachments on tibia and femur, such that these data can be used in an arthroscopically guided procedure for reconstruction of the ACL. We hypothesized that reliable guidelines to find the centres of the AMB, PLB and ACL relative to arthroscopically visible landmarks can be established. For the purpose of an anatomically accurate reconstruction of the ACL, the variations should be equal to or less than reported in other studies. As regard to the dimensions of drilled tunnel holes, normally 10 up to 12 mm, 95% (mean ± 2SD) of the attachment centres should be within this range. Therefore the a priori set assumption is that the maximally acceptable SD is 2.5 up to 3 mm. Methods Dissection 16 Anatomical position x y z 42 r P Femur 17 1 4 1 Fig. 1 4 shallow deep low high  2 17 2 2 3 Fig. 2 a rectangular corner b white rounds black rounds grey asterisks black asterisk white asterisk  Fig. 3 first reference line second reference line centre  Tibia 4 5 Fig. 4 white rounds black rounds light grey oval dark grey oval white asterisks  Fig. 5 first reference line second reference line centre  Surface 2 ® http://www.mathworks.com t P Results Femur The oval-shaped attachment of the anterior cruciate ligament was situated on the medial surface of the lateral femoral condyle. It was positioned deep in the notch, covering most of the proximal half of the wall. The fibres of the deep low border attached to the edge of the joint cartilage, following the contour of this edge posteriorly on the condyle. In only 4 of the 35 specimens, the attachment site was completely limited to the medial wall of the lateral condyle and had no footprint in the notch roof. In 31 femurs, a small part of the deep high AMB attachment extended into the intercondylar notch roof. 1 6 1 6 P Table 1 The positions of the ligament centres in the femoral notch   Absolute distances (mm) mean (SD) Relative distances (%) mean (SD) DP CP DP/DS CP/LH AMB 7.2 (1.8) 1.4 (1.7) 23 (6) 10 (12) PLB 8.8 (1.6) 6.7 (2.0) 28 (6) 47 (13) ACL 7.9 (1.4) 4.0 (1.3) 25 (5) 28 (9) DP CP DP/DS CP/LH Fig. 6 a red squares blue diamonds green dots b red square with line blue diamond with line green dot with line  P 2 Table 2 The surface dimensions of the ACL and the two bundles at femur and tibia  Absolute surface area (mm) mean (SD) Relative surface to total ACL (%) mean (SD) ACL AMB PLB AMB PLB Femur 184 (52) 81 (27) 103 (39) 45 (11) 55 (11) Tibia 229 (53) 136 (37) 93 (33) 59 (9) 41 (9) Tibia The tibial attachment area of the ACL was situated between the medial and lateral tibial condyle covering the medial part of the anterior intercondylar area. It was stretched out from the region between the tibial spines to anterior with various extensions, more or less shaped as a footprint. The fibres of the AMB inserted medially along the cartilage edge of the articular surface of the medial tibial condyle. The PLB covered the lateral side of the attachment area and was bounded by the attachment of the anterior horn of the lateral meniscus. 3 7 3 7 P P Table 3 The positions of the ligament centres at the anterior intercondylar tibial area  Absolute distances (mm) mean (SD) Relative distances (%) mean (SD) MP CP MP/ML CP/MQ AMB 3.0 (1.6) 9.4 (2.2) 23 (12) 37 (9) PLB 7.2 (1.8) 10.1 (2.1) 55 (13) 38 (9) ACL 5.1 (1.7) 9.8 (2.1) 39 (12) 38 (8) MP CP MP/ML CP/MQ Fig. 7 a red squares blue diamonds green dots b red square with line blue diamond with line green dot with line  P P 2 Discussion 22 25 43 1 8 27 47 11 20 32 45 52 20 52 11 32 45 45 13 18 35 36 52 54 17 54 17 21 29 55 56 24 32 52 7 11 6 22 34 44 31 26 23 45 20 3 16 38 45 2 2 38 2 45 2 20 20 45 16 15 45 2 20 38 45 20 There was a large variation in knee sizes and dimensions of the reference lines. However, we did not find a correlation between the absolute distance of the attachment centres and the size of the reference lines, i.e. knee size. The absolute positions of the attachment centres were more or less similar for large and small knees. Therefore both absolute as well as relative data can be used as guidelines to find the anatomical positions. At the arthroscopic view, the absolute positions are more useful than the relative positions. 5 15 33 38 33 3 11 20 32 11 45 3 11 34 44 Conclusions This study was performed because no earlier study described the ACL, AMB and PLB attachment centres relative to arthroscopically visible landmarks. This resulted in quantitative data of the positions of the attachment centres of the ACL and its two bundles, relative to bony landmarks on femur and tibia, visible through an arthroscope. Using these results, the surgeon will be able to determine the anatomical position of the ACL and the two functional bundles during arthroscopy without additional images or fluoroscopic support. The results can be applied for anatomic single-bundle or anatomic double-bundle techniques.