Medial Portal Technique for Anterior Cruciate Ligament Reconstruction

Christopher A. Radkowski MD

Christopher D. Harner MD

History of the Technique

Several significant advances have been made in the realm of anterior cruciate ligament (ACL) reconstruction. Use of arthroscopy and the wide array of graft choices and fixation devices available to the surgeon offer a variety of means to obtain a successful ACL reconstruction.¹^,²^,³^,⁴^,⁵ Advances in early motion rehabilitation have also contributed to excellent clinical results.⁶^,⁷^,⁸ Biomechanical and anatomic studies have enhanced our understanding of the ACL and its function.⁹^,¹⁰^,¹¹^,¹²

There are several potential causes of ACL reconstruction failure.¹³^,¹⁴^,¹⁵^,¹⁶ One of the most common preventable errors is in surgical technique, specifically errant femoral and tibial tunnel placement.¹⁷^,¹⁸ The desired position for femoral tunnel placement is posterior on the medial aspect of the lateral femoral condyle at the 10 or 2 o’clock position for right and left knees, respectively. This tunnel position has been shown to more effectively resist rotatory loads in a cadaveric study.¹⁹ Use of a transtibial technique can make it more difficult to accurately place the femoral tunnel in the optimal position. In this manner, the femoral tunnel is limited to the confined space dictated by the position of the tibial tunnel.

The medial portal technique for femoral tunnel placement offers several advantages over the transtibial tunnel technique. First, use of the anteromedial portal facilitates accurate placement of the femoral tunnel that is not dependent on the tibial tunnel position. In addition to allowing the surgeon more freedom for anatomic placement of the femoral tunnel, this method provides an opportunity to better preserve any intact ACL fibers when performing anteromedial (AM) or posterolateral (PL) bundle augmentation. It can be used in the primary or revision ACL reconstruction setting and can be used regardless of the type of graft, instrumentation, or fixation.²⁰

Another advantage of using the medial portal technique is in the placement of femoral interference screws. Because both the drill for the femoral tunnel and the screw are passed through the medial portal, the paths of the tunnel and the interference screw will be parallel. It has been shown that placement of the interference screw parallel with the tunnel provides stronger fixation than a divergent position.²¹^,²² In a series of 100 ACL reconstructions, O’Donnell and Scerpella²³ have shown that use of this technique leads to low divergence rates and angles between the femoral tunnel and interference screw.

Use of the medial portal technique may lead to a decrease in the number of errant femoral tunnels placed in ACL reconstruction. Yasuda et al.²⁴ recommended use of the medial portal to better visualize the anatomic insertion site of the PL bundle in ACL reconstruction. Other studies have shown successful results of ACL reconstruction using the medial portal technique.²³^,²⁵^,²⁶^,²⁷^,²⁸^,²⁹^,³⁰^,³¹ In 1990, Harner et al.³² progressed from the two-incision technique for ACL reconstruction to an all-arthroscopic technique. Because of concerns over lack of rotational stability in ACL reconstruction, the modification of lower femoral tunnel placement via the medial portal technique instead of a transtibial technique was implemented in 1999.

Indications and Contraindications

The medial portal technique may be used in any ACL reconstruction setting. This method may be utilized independent of the type of graft, the type of tunnel placement guide, and the type of fixation.²⁰ Establishing the femoral tunnel through the medial portal may be especially useful in AM or PL bundle augmentation cases. Another indication for this technique is in revision ACL reconstruction cases in which the tibial tunnel is well aligned but the femoral tunnel
is not. Even in revision surgery, with well-placed femoral tunnels from a transtibial technique, use of the medial portal technique allows placement of a divergent femoral tunnel in native bone. In some cases with tunnel widening, this method may eliminate the need for a staged reconstruction procedure with bone grafting.

Because the knee must be flexed to 120 degrees, the medial portal technique cannot be used in cases in which a leg holder is placed circumferentially around the femur. There are no known relative or absolute contraindications for use of this technique.

Surgical Technique

Preoperative Assessment

A thorough history and physical examination are obtained preoperatively in a clinic setting. Note is made of the active range of motion (ROM) of both knees and any positive findings that may suggest associated pathology. Magnetic resonance imaging (MRI) is frequently done to assess for meniscal pathology, which can be difficult to elucidate with a large effusion and a guarded physical examination. Informed consent is obtained in the clinic.

Anesthesia

The patient is identified in the preoperative holding area and the operative site is signed. Femoral nerve blocks are usually performed for postoperative pain management. The patient is taken to the operating room where spinal or general anesthesia is induced.

Patient Positioning

The patient is positioned supine on the operating room table. A padded bump is taped to the operating room table at the foot with the knee flexed to 90 degrees to hold the leg flexed during the case. A side post is placed on the operative side just distal to the greater trochanter to support the proximal leg with the knee in flexion. Padded cushions are placed under the nonoperative leg. A tourniquet and a leg holder are not used.

Examination under Anesthesia

An examination under anesthesia (EUA) is then performed. The non-operative knee is examined followed by the operative knee. The alignment and ROM is assessed with specific attention to terminal extension. A ligamentous exam is performed including a Lachman test, pivot shift test, anterior drawer test, posterior drawer test, and stability to varus and valgus stress at 0 and 30 degrees of flexion. This examination is critical for completing a thorough evaluation of the injured knee, which may often be obscured by guarding and effusion in the office setting. Lower grades of Lachman and pivot shift tests may represent an intact AM or PL bundle of the ACL, whereas higher grades may signal a functional loss of the secondary stabilizers of the knee (i.e., medial meniscus).

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