Medial portal technique for single-bundle anatomical anterior cruciate ligament (ACL) reconstruction

Abstract

The aim of the paper is to describe the medial portal technique for anatomical single-bundle anterior cruciate ligament (ACL) reconstruction. Placement of an ACL graft within the anatomical femoral and tibial attachment sites is critical to the success and clinical outcome of ACL reconstruction. Non-anatomical ACL graft placement is the most common technical error leading to recurrent instability following ACL reconstruction. ACL reconstruction has commonly been performed using a transtibial tunnel technique in which the ACL femoral tunnel is drilled through a tibial tunnel positioned in the posterior half of the native ACL tibial attachment site. ACL reconstruction performed using a transtibial tunnel technique often results in a vertical ACL graft, which may fail to control the combined motions of anterior tibial translation and internal tibial rotation which occur during the pivot-shift phenomenon. The inability of a vertically oriented ACL graft to control these combined motions may result in the patient experiencing continued symptoms of instability due to the pivot-shift phenomenon. The medial portal technique in which the ACL femoral tunnel is drilled through an anteromedial or accessory anteromedial portal allows consistent anatomical ACL tunnel placement. This paper describes the advantages of the medial portal technique, indications for the technique, patient positioning, proper portal placement, anatomical femoral and tibial tunnel placement, graft tensioning and fixation.

Figures

Fig. 1

Transtibial tunnel technique. a The femoral guide pin is drilled using an ACL femoral offset aimer inserted through a tibial tunnel positioned in the posterior half of the ACL tibial attachment site. b An ACL femoral tunnel drilled through a posteriorly positioned tibial tunnel often results in the ACL femoral tunnel being positioned high relative to the native ACL femoral attachment site. c An ACL graft positioned in a posterior tibial and high femoral tunnel often results in a non-anatomical “vertical” ACL graft. d An example of ACL reconstruction using a transtibial technique

Fig. 2

a Medial portal technique. The knee is hyperflexed and the femoral tunnel is drilled through a medial portal. b The knee is hyperflexed with the 30° arthroscope positioned in the anteromedial (AM) portal. The ACL femoral tunnel is drilled through a low AAM portal. c View through the AM portal with the knee in hyperflexion. The ACL femoral tunnel is drilled into the centre of the ACL femoral attachment site through a low AAM portal

Fig. 3

The right knee is positioned in hyperflexion during drilling of the ACL femoral tunnel. The drill tip femoral guide pin exits the lateral soft tissues in the mid-thigh region and is thus directed away from the peroneal nerve and posterior neurovascular structures

Fig. 4

a Isolated PL bundle reconstruction. b Isolated AM bundle reconstruction

Fig. 5

AM portal view at 90°. Failed ACL reconstruction. Probable cause of failure: non-anatomical ACL femoral tunnel placement. Surgical technique: transtibial. The old ACL femoral tunnel is located high above the anatomical ACL femoral attachment site. A new anatomical ACL femoral tunnel was drilled through an AAM portal bypassing the original non-anatomical femoral tunnel

Fig. 6

a The patient’s pelvis is stabilised on the operating table by the lateral hip positioner and thigh post. b Distal foot rest is adjusted to maintain 90° of knee flexion. c Proximal foot rest is adjusted to maintain hyperflexion during drilling of the ACL. d The proximal and distal foot rest can be adjusted to maintain the desired degree of knee flexion during graft tensioning and fixation

Fig. 7

Three portals and their relationship to the inferior pole of the patella, medial and lateral borders of the patellar tendon, and the medial and lateral joint lines. AL high anterolateral portal, AM high anteromedial portal, AAM low accessory anteromedial portal

Fig. 8

Medial placement of the AAM portal results in a more perpendicular orientation of the spinal needle relative to the lateral wall of the notch. The orientation will produce a more circular-shaped aperture of the ACL femoral tunnel and a shorter femoral tunnel length

Fig. 9

A more lateral placement of the AAM portal results in a more oblique orientation of the spinal needle relative to the lateral wall of the notch. This orientation will produce a more elliptically shaped aperture of the femoral tunnel and a longer femoral tunnel length. Based on the ACL graft type and femoral fixation method, the position of the AAM portal is adjusted to achieve the desired ACL femoral tunnel length. For example, if a bone-patellar tendon-bone ACL graft with interference screw fixation of the femoral bone block is used for the ACL reconstruction, the optimal femoral tunnel length can be in the range of 25–30 mm. For this graft type and fixation method, the AAM portal can be positioned more medially compared to an ACL reconstruction performed using a multiple-strand hamstring tendon graft with ENDOBUTTON femoral fixation

Fig. 10

ACL tibial attachment site. The medial and lateral tibial tubercles (spines) with the interconnecting ACL ridge and the medial intercondylar ridge of the tibia are well seen

Fig. 11

Measuring tibial attachment site length. a Short tibial insertion site (13 mm). b Long tibial insertion site (18 mm)

Fig. 12

AM portal view at 90° of flexion. Remnants of the native ACL fibres at the ACL femoral attachment site are clearly seen

Fig. 13

AM portal view at 90° of flexion (arthroscopic position). In the arthroscopic terminology, directions along the lateral wall of the intercondylar notch are referred to as: high or superior, low or inferior, shallow and deep. The directions using the corresponding anatomical terminology (shown in parentheses) which references the knee in the extended position are: anterior, posterior and distal. Remnant ligament fibres of the native ACL are seen along the lower third of the lateral wall of the notch

Fig. 14

View through the AM portal at 90° of flexion. The lateral intercondylar and bifurcate ridges are clearly visible

Fig. 15

AM portal view at 90°. Microfracture awl tip is positioned halfway between the lateral intercondylar ridge and the inferior (low) articular cartilage margin

Fig. 16

View through the AM portal at 90° of flexion. The ACL ruler has been bent to lie flat along the lateral wall of the intercondylar notch. The ruler is inserted through the AL portal and is positioned to lie parallel to the wall of the notch just below the lateral intercondylar ridge (dotted line)

Fig. 17

AM portal view at 90° of flexion. Remnant fibres of the native ACL are seen along the lateral wall of the notch. The ACL femoral attachment site is shown by the dotted ellipse. The length of the ACL femoral attachment site length is measured along its long axis (black line)

Fig. 18

AM portal view at 90° of flexion, same knee as shown in Fig. 17. The ACL ruler is inserted through the AL portal and the 45° microfracture awl through the AAM portal. In this case, the ACL femoral attachment site length measures 14 mm, so the centre of the ACL femoral tunnel is placed at the 7 mm mark

Fig. 19

Chronic ACL-deficient knee. AM portal view at 90° of flexion. a The lateral intercondylar ridge is clearly seen. However, there are no remnants of the native ACL fibres visible. b The ACL ruler is inserted through the AL portal. The length of the lateral wall of the notch measures 18 mm. A 45° microfracture awl is inserted through the AAM portal and is used to mark the ACL femoral attachment site at 9 mm, which represents 50 % of the measured lateral wall length

Fig. 20

AM portal view at 90°. The tip of the 45° microfracture awl is placed halfway between the lateral intercondylar ridge and the low (posterior) articular cartilage margin and 50 % of the length of the ACL femoral attachment site as measured using the ACL ruler. Note that in this particular case, the centre of the ACL femoral attachment site lies slightly deep (proximal) to the lateral bifurcate ridge

Fig. 21

a Intra-operative C-arm. b True lateral image of the knee. The microfracture awl is positioned at the centre of the ACL femoral attachment site

Fig. 22

a Bernard and Hertel grid. b The centre of the AM and PL bundles are shown according to the data of Columbet et al. [16]. In this study, the centre of the AM bundle was found to lie at a point 25 % along Blumensaat’s line (t) and 25 % along line h. The centre of the PL bundle was located at a point 33 % along line t and 50 % along line h

Fig. 23

The ACUFEX DIRECTOR APPLICATION Anatomic Guide software was used to plot the location of the AM and PL bundles (white circles) based on the data of Columbet et al. [16]. The software also allows other coordinates for the centre of the AM and PM bundles to be selected. In this example, the tip of the microfracture awl is positioned halfway between the centre of the AM and PL bundles (white circles). This location would position the ACL femoral tunnel in the centre of the ACL femoral attachment site

Fig. 24

AM portal view in hyperflexion. a The femoral drill tip passing pin is oriented perpendicular to the lateral wall of the notch. This guide pin orientation will result in a short femoral tunnel length and a more circular shape of the ACL femoral tunnel aperture. b The 0° offset aimer has been angled laterally which results in the femoral guide pin being oriented more obliquely to the lateral wall of the notch. A more oblique orientation of the guide pin will increase the length of the ACL femoral tunnel and produce a more elliptically shaped femoral tunnel aperture [7]

Fig. 25

a AM portal view in hyperflexion. The endoscopic drill bit is inserted into the intercondylar notch through the AAM portal and is seen to lie at the centre of the ACL femoral attachment site. b AM portal view at 90°. The elliptically shaped aperture of the ACL femoral tunnel is centred in the ACL femoral footprint

Fig. 26

Chronic ACL-deficient knee with osteophytes along the lateral wall of the intercondylar notch. After drilling the ACL femoral tunnel, a curved compound gouge is used to excise the osteophytes along the lateral wall and widen the width of the intercondylar notch

Fig. 27

The tip of the ACL tip aimer is positioned slightly anterior to the posterior margin of the anterior horn of the lateral meniscus and slightly medial to the midline of the tibial footprint

Fig. 28

The tibial guide pin is positioned slightly anterior to the posterior margin of the anterior horn of the lateral meniscus and slightly medial to the midline of the insertion site

Fig. 29

The C-arm is used to take a lateral radiograph of the knee in full hyperextension

Fig. 30

Amis-Jakob line [18]. The medial joint line is marked by the dotted white line. The Amis-Jakob line (red line) passes through the posterior corner of the widest part of the medial tibial plateau (square posterior border) parallel to the medial joint line. The anterior tibial cortex represents 0 % and the posterior tibial cortex 100 % of the sagittal width of the tibia. The tibial guide pin position is calculated by dropping an orthogonal line (green line) from the point where the tibial guide pin crosses the medial joint line onto the Amis-Jakob line. The distance from the anterior tibial cortex (0 %) to the orthogonal projection onto the Amis-Jakob line (blue line with arrowheads) is represented as a percentage of the total length of the Amis-Jakob line. The tibial guide pin in this case is located at 44 % along the Amis-Jakob line, which places the guide pin in the centre of the ACL tibial attachment site

Fig. 31

The tibial tunnel is elliptically shaped and in this case almost completely restores the cross-sectional area of the ACL tibial attachment site

Fig. 32

Passing femoral bone block. An arthroscopic probe can be used to assist with rotation of the femoral bone block into the ACL femoral tunnel

Fig. 33

a Six-strand (9.5 mm) hamstring ACL graft, b 10 mm bone-patellar tendon-bone ACL graft