*smith&nephew KNEE TECHNIQUE GUIDE Single-Bundle ACL Reconstruction: Medial Portal Technique Charles H. Brown Jr., MD Tim Spalding, MD KNEE HIP SHOULDER EXTREMITIES Single-Bundle ACL Reconstruction: Medial Portal Technique As described by: Anatomic placement of an anterior cruciate ligament (ACL) graft is critical Charles H. Brown Jr., MD to the success and clinical outcome of ACL reconstruction. Anatomic ACL Abu Dhabi, United Arab Emirates graft placement is defined as positioning the ACL femoral and tibial bone tunnels at the center of the native ACL femoral and tibial attachment sites. Tim Spalding, FRCS Orth. Clinical studies have demonstrated that non-anatomic ACL graft placement Consultant Orthopaedic Surgeon is the most common technical error leading to recurrent instability following University Hospital Coventry ACL reconstruction.1,2 ACL reconstruction has been commonly performed and Warwickshire NHS Trust, UK using a transtibial 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. In the transtibial technique, positioning the ACL tibial tunnel in the posterior half of the ACL tibial attachment site is dictated by the need for the endoscopic drill bit to reach the region of the ACL femoral attachment site and the desire for the ACL graft to avoid impingement against the roof of the intercondylar notch when the knee is in full extension. However, the resulting ACL femoral tunnel is often positioned too high and too deep in the intercondylar notch, away from the native ACL femoral attachment site. An ACL graft positioned at a posterior tibial and a high-deep femoral attachment site will be vertically oriented in both the coronal and sagittal planes. Biomechanical studies have shown that a vertically oriented ACL graft may resist the motion of anterior tibial translation, but may fail to control the combined motions of anterior tibial translation and internal rotation which occur during the pivot-shift phenomenon.3 The inability of a vertically oriented ACL graft to control these combined motions may result in the patient experiencing continued symptoms of instability and giving-way episodes due to the pivot-shift phenomenon. KNEE TECHNIQUE GUIDE 10600926 Rev. A In the medial portal technique described in this paper, the ACL femoral tunnel is drilled through an accessory anteromedial (AAM) portal with the knee flexed to 120° or higher (Figures 1A and 1B). This approach provides several advantages compared to the traditional transtibial technique: 1. The ACL femoral tunnel is drilled independently of the tibial tunnel, which results in consistent placement of the femoral tunnel within the native ACL femoral attachment site. 2. The angle of the ACL tibial tunnel does not have to be compromised to accommodate drilling of the ACL femoral tunnel. Therefore, the surgeon can opt to drill a steeper and thus longer tibial tunnel. A longer tibial tunnel minimizes the potential for graft-tunnel length mismatch and allows longer bone-tendon- bone graft constructs to be utilized. 3. Although guides are available, the medial portal technique does not require any special guides or instrumentation. Figure 1A 4. Inserting an ACL femoral interference fixation screw through the same medial portal which was used to drill the ACL femoral tunnel minimizes screw-tunnel divergence. 5. The medial portal technique provides improved arthroscopic visualization during drilling of the ACL femoral tunnel since the femoral tunnel can be drilled under ideal arthroscopic conditions, without the loss of joint distention due to fluid extravasation out of the tibial tunnel. In the medial portal technique, the knee must be flexed to 120° or higher when a rigid guide pin and drill bit are used to drill the ACL femoral tunnel (Figure 2). Hyperflexion is necessary to avoid having the femoral guide pin exit the lateral soft tissues too posteriorly. The peroneal nerve is at risk when the femoral guide pin exits the lateral Figure 1B soft tissues in a too posterior position. Alternatively, the knee may be positioned at 90° of flexion and the ACL femoral tunnel drilled using a flexible guide wire and CLANCYTM flexible reamers. Figure 2 4 KNEE TECHNIQUE GUIDE 10600926 Rev. A INDICATIONS AND CONTRAINDICATIONS PORTAL PLACEMENT The medial portal technique is versatile and can Proper portal placement is critical to the success be used with any ACL graft type and for any of the procedure. ACL reconstruction using the primary, revision, single- or double-bundle ACL medial portal technique is facilitated by using reconstruction. The medial portal technique is three arthroscopic portals (Figure 3): particularly useful in the situation where only • The anterolateral (AL) portal, one of the ACL bundles is torn and the surgeon used as a viewing portal wishes to preserve the remaining intact ACL to perform diagnostic fibers and augment the injured posterolateral arthroscopy and meniscal (PL) or anteromedial (AM) bundle. The only surgery contraindication to the medial portal technique • The anteromedial (AM) portal, when using rigid guide pins and drill bits is the used as both a working and inability to flex the knee to at least 120°. This viewing portal limitation may be encountered in some obese patients, in which case consideration should be • The accessory anteromedial given to drilling the ACL femoral tunnel using an portal (AAM), used as a outside-in technique or using flexible reamers. working portal to insert instrumentation into the notch and for drilling the ACL PATIENT POSITIONING femoral tunnel It is important to have the ability to achieve full, Figure 3 The use of three portals provides unrestricted knee flexion during the procedure. the following advantages: The need to flex the knee to greater than 1. The additional medial portal allows the 120° of flexion can present problems when a ACL femoral attachment site to be viewed circumferential leg holder is used and the foot of through the AM portal, while working the operating room table is flexed down during instrumentation is inserted into the notch the procedure. through the AAM portal. As will be discussed The procedure is facilitated by keeping the later, viewing through the AM portal is the operating room table flat and using a thigh post preferred method to visualize the ACL femoral and one or two foot supports. This positioning attachment site. technique allows unrestricted knee flexion to be 2. Drilling the ACL femoral tunnel through an performed during the procedure and eliminates AAM portal increases the obliquity of the ACL the need to have an assistant maintain femoral tunnel relative to lateral wall of the hyperflexion of the knee during drilling of the notch, resulting in a longer femoral tunnel ACL femoral tunnel. length and a more elliptical ACL femoral 1. Position the patient supine on the OR table tunnel aperture compared to drilling the and apply a thigh-length anti-embolism femoral tunnel through the AM portal. stocking and a foam heel protector to the non-operative leg. 2. Place a padded pneumatic tourniquet high on the operative leg. Note: The tourniquet is rarely used during the procedure, as adequate joint visualization can be obtained using the Smith & Nephew DYONICS™ 25 Fluid Management System. KNEE TECHNIQUE GUIDE 10600926 Rev. A 5 ESTABLISH THE ANTEROLATERAL PORTAL Establish a high AL portal at the level of the inferior pole of the patella, as close as possible to the lateral border of the patellar tendon using a #11 knife blade. A high AL portal places the arthroscope above the widest part of the fat pad, minimizing interference of the visual field in the intercondylar notch when the knee is placed in hyperflexion. A high AL portal also provides a better, “look down” view of the ACL tibial attachment site. ESTABLISH THE ANTEROMEDIAL PORTAL Establishing the AM portal at the correct height above the medial joint line is extremely important to the success of the procedure. The needle position is too low if it enters the knee joint below the level of the roof of the intercondylar notch or passes through the fat pad. Placing the AM portal too low above the medial joint line will result in the arthroscope passing through the fat pad and will place the AM and AAM portals too close together. This will result in the fat pad being dragged into the visual field by the tip of the arthroscope and instrument crowding when the AM and AAM portals are used simultaneously to view the ACL femoral attachment site and drill the ACL femoral tunnel. 1. Place a 30° arthroscope in the AL portal and perform a diagnostic arthroscopy. 2. With the knee flexed between 70–90°, establish the AM portal under direct visualization using an 18-gauge needle. 3. Insert the needle into the knee joint as close as possible to the medial border of the patellar tendon. Direct the needle towards the intercondylar notch, adjusting the height of the needle above the medial joint line as needed to ensure that it comes to lie parallel to the roof of the intercondylar notch. 4. Typically, the needle is located at the height of the interior pole of the patella or slightly higher. Placing the needle at this level results in adequate spatial separation between the AM and the AAM portal, which is established later, and also results in the AM portal lying above the fat pad. 5. Insert a motorized shaver with a straight or curved 4.5 mm DYONICS™ INCISOR™ PLUS ELITE™ Shaver Blade into the knee joint through the AM portal and resect the ligamentum mucosum. This step will release the fat pad and expose the intercondylar notch. PLACEMENT OF THE A CCESSORY ANTEROMEDIAL PORTAL Proper placement of the AAM portal is also critical to the success of the procedure, as it is the most important factor affecting the length of the ACL femoral tunnel. The medial-lateral placement of the AAM portal determines both the length of the ACL femoral tunnel and the shape of the tunnel’s aperture. Positioning the AAM portal more medially results in a more perpendicular orientation of the femoral guide pin with respect to the lateral wall of the notch and produces a shorter ACL femoral tunnel and a more circular-shaped tunnel aperture (Figures 4A, 4B, and 4C).4 However, placing the AAM portal too medially can result in damage to the medial femoral condyle when the AAM portal is used to drill the ACL femoral tunnel. Moving the AAM portal more laterally, towards the medial border of the patellar ligament, orients the femoral guide pin more obliquely with respect to the lateral wall of the notch and produces a longer ACL femoral tunnel length and a more elliptically-shaped tunnel aperture (Figures 5A, 5B, and 5C).4 6 KNEE TECHNIQUE GUIDE 10600926 Rev. A Figure 4A Figure 4B Figure 4C Figure 5B Figure 5C Figure 5A Based on the ACL graft type and femoral fixation method, adjust the position of the AAM portal 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-stranded hamstring tendon graft with an ENDOBUTTON™ fixation device for femoral fixation. When performing hamstring ACL reconstructions with cortical fixation devices such as the ENDOBUTTON CL ULTRA fixation device, it is optimal to achieve a femoral tunnel length of approximately 40 mm, with the minimum tunnel length being approximatey 35 mm. A 40 mm femoral tunnel allows for 25 mm of the hamstring tendon graft to be inserted into the ACL femoral socket when using a 15 mm ENDOBUTTON CL ULTRA fixation device. In the event that a shorter femoral tunnel is drilled, or the surgeon prefers more graft in the femoral tunnel, a 10 mm ENDOBUTTON CL ULTRA fixation device can be used. In this example, a 40 mm femoral tunnel allows for 30 mm of the hamstring tendon to be inserted into the ACL femoral socket. KNEE TECHNIQUE GUIDE 10600926 Rev. A 7 ESTABLISH THE ACCESSORY ANTEROMEDIAL PORTAL 1. Use an 18-gauge needle to determine the optimal position for the AAM portal. The AAM portal should be located as low as possible above the medial joint line while avoiding the anterior horn of the medial meniscus. Rotate the arthroscope medially to determine if the needle is positioned too closely to the medial femoral condyle. Adjust the position of the portal accordingly. 2. Create the AAM portal using a # 11 knife blade, with the cutting edge of the blade oriented away from the anterior horn of the medial meniscus. 3. Dilate the AAM portal by inserting the tips of the Metzenbaum scissors or a small curved clamp into the incision and spreading the tips in-line with the direction of the portal. This step will ease future instrument passage through the AAM portal. PREPARE THE TIBIAL ATTACHMENT SITE Carefully inspect the remnants of the torn ACL. An attempt should be made to preserve large tibial stumps and ACL fibers with intact connections from the tibia to the femur. 1. Insert a motorized shaver with a straight or curved 4.5 mm DYONICS™ INCISOR™ PLUS ELITE™ Shaver Blade into the knee joint through the AM portal and resect the mid-section of the ACL. Preserve some of the remaining native ACL fibers at the tibial and femoral attachment sites to aid with anatomic placement of the ACL bone tunnels. 2. Insert a 90º high profile SAPHYRE™ Bipolar Ablation Probe through the AM Figure 6 portal and mark the borders of the ACL tibial attachment site (Figure 6). Note that a majority of the ACL tibial attachment site extends anterior to the posterior margin of the anterior horn of the lateral meniscus. The anterior margin of the ACL tibial attachment site lies just posterior to the intermeniscal ligament and the posterior margin lies just anterior to a bony ridge connecting the medial and lateral tubercles (spines). The medial border of the ACL tibial attachment site is defined by a bony ridge, the medial intercondylar ridge of the tibia, which extends anteriorly from the medial tubercle. DETERMINE THE LENGTH OF THE ACL TIBIAL A TTACHMENT SITE Insert a TRUKOR™ Gauge through the AAM portal and determine the Figure 7 length of the ACL tibial attachment site (Figure 7). Long and wide ACL tibial attachment sites are best restored with larger diameter ACL grafts such as 5- and 6-strand hamstring tendon grafts, a bone-patellar tendon-bone graft, a quadriceps tendon graft, or by performing a double-bundle ACL reconstruction.5 ANATOMIC ACL GRAFT PLACEMENT Biomechanical studies have demonstrated that a single-bundle ACL graft positioned at the center of the ACL femoral and tibial attachment sites best controls anterior tibial translation and the combined motions of anterior tibial translation and internal tibial rotation.3 It also restores knee kinematics more closely to those of the normal knee compared to other anatomic ACL graft placements.3 Based on the reported mean cross-sectional area of the native PL and AM bundles, 60% of the area of an ACL femoral tunnel placed at the center of the ACL femoral attachment site will lie in the region of the AM bundle attachment site, and 40% in the region of the PL bundle attachment site.6 8 KNEE TECHNIQUE GUIDE 10600926 Rev. A ANATOMIC ACL FEMORAL TUNNEL POSITION Although the clock-face reference method is often used to specify ACL femoral tunnel placement, the clock-face reference method has several shortcomings: it ignores the depth of the notch; there is no agreed upon reference position for the 3 and 9 o’clock locations; it relies on no known anatomic landmarks; and it cannot be used when viewing the ACL femoral attachment site through the AM portal. ACL femoral tunnel placement is more accurately defined and specified using the following methods: I. Native ACL Footprint In most cases, remnants of the native ACL fibers are present at the ACL femoral attachment site and these can aid with anatomic ACL femoral tunnel placement (Figure 8). The view of the intercondylar notch and ACL femoral attachment site changes significantly depending on the arthroscopic portal utilized. Figure 8 Viewing the ACL femoral attachment site through the AM portal provides an orthogonal view of the lateral wall of the notch, allowing accurate assessment of both the shallow-deep and high-low directions (Figure 9). As a result, the AM portal is the preferred portal for viewing the anatomic ACL femoral attachment site. Viewing the ACL femoral attachment site through the AM portal also eliminates the need to perform a routine notchplasty for visualization purposes. Avoid using a curette, motorized shaver blade or burr to initially perform a notchplasy or to completely remove all of the soft tissue remnants from the lateral wall of the notch as this destroys the remaining native ACL fibers and underlying bony landmarks. Figure 9 To use the native ACL footprint method: 1. View the lateral wall of the notch with the scope in the AM portal. Insert a 90º high profile SAPHYRE™ Bipolar Ablation Probe through the AAM and mark the borders of the native ACL femoral attachment site. 2. Insert a 45° angle microfracture awl through the AAM and mark the center of the ACL femoral attachment site. II. Lateral Intercondylar and Bifurcate Ridges When there are no soft tissue remnants present at the native ACL femoral attachment site to use for reference, the underlying bony morphology of the femoral attachment site can provide useful anatomical landmarks to assist with anatomic ACL femoral tunnel placement. Anatomic studies have demonstrated that the ACL femoral attachment site is defined by two osseous ridges (Figure 10).6 The lateral intercondylar ridge (“resident’s ridge”) runs at approximately a 30–35° angle with respect to the long axis of the femoral shaft and represents the upper or superior limit of the ACL femoral attachment Figure 10 KNEE TECHNIQUE GUIDE 10600926 Rev. A 9 site. The lateral intercondylar ridge has been shown to be present and visible in 88–100% of chronic ACL deficient knees.7,8 When present, the lateral intercondylar ridge is critical to anatomic ACL femoral tunnel placement since the ACL femoral attachment site always lies below or inferior to this ridge. In some knees it may be possible to identify a second bony ridge, the lateral bifurcate ridge, which separates the attachment sites of the AM and PL bundle fibers.6 It is important to remember that because the cross-sectional area of the PL and AM bundles is variable from patient to patient, the location of the bifurcate ridge, when present, does not necessarily represent the true center of the ACL femoral attachment site. To use the osseous ridges: 1. Use a 90º high profile SAPHYRE™ Bipolar Ablation Probe to remove soft tissue along the lower third of the lateral wall of the notch. 2. With the knee at 90° of flexion, identify the lateral intercondylar ridge and the lower border of the articular cartilage margin. The ridge is most easily identified by starting the dissection at the inferior articular cartilage border and working in a superior (high) direction. As the probe contacts the ridge, a distinct endpoint will be encountered. The center of the ACL femoral attachment site in the high-low direction is located half-way between these two landmarks. 3. Use an ACL template or fluoroscopy to determine the shallow-deep position of the ACL femoral tunnel. III. ACL Template An ACL template allows the surgeon to individualize the location of the ACL femoral tunnel based on the specific anatomy of the patient. This approach allows for “a la carte” or patient-specific surgery to be performed versus the “one size fits all” approach associated with the use of offset femoral aimers. 1. With the knee at 90° of flexion, place the arthroscope in the AM portal to view the ACL femoral attachment site. 2. Bend the TRUKOR™ Gauge to approximately a 45° angle at the 24 mark to allow it to lie flat along the lateral wall of the notch. 3. Insert the TRUKOR Gauge into the knee joint through either the AL or the AAM portal (Figure 11). Inserting the TRUKOR Gauge through the AL portal allows a microfracture awl to be inserted through the AAM portal, giving the surgeon the ability to measure and simultaneously mark the ACL femoral attachment site. However, due to the height of the AL portal above the lateral joint line, in some knees it may be more difficult to position the TRUKOR Gauge further down the sidewall of the notch at the location of the intercondylar ridge. In this situation, it may be advantageous to insert the Figure 11 TRUKOR Gauge through the AAM. The lower position of the AAM portal allows the TRUKOR Gauge to be easily positioned further down the sidewall of the notch. 4. If remnant fibers of the ACL are clearly visible, determine the length of the ACL femoral attachment site along its long-axis using the TRUKOR Gauge (Figure 12A and Figure 12B). Figure 12A Figure 12B 10 KNEE TECHNIQUE GUIDE 10600926 Rev. A