Patellar tendon autograft for anterior cruciate ligament reconstruction

OVERVIEW

Chapter synopsis

The bone–patellar tendon–bone autograft is the most commonly used graft during the last 20 years and the graft of choice of physicians treating National Collegiate Athletic Association (NCAA) Division 1A and professional athletes. This is because of the graft’s ready accessibility, mechanical strength, and osseous tunnel integration. In this chapter, we highlight the harvesting procedure as well as transtibial and medial portal femoral independent surgical techniques for anatomic anterior cruciate ligament (ACL) reconstruction using bone–patellar tendon–bone autograft.

Important points

Surgical steps:

1.
Graft harvest
2.
Graft preparation
3.
Notch preparation
4.
Femoral tunnel placement
5.
Tibial tunnel placement
6.
Graft placement and fixation
7.
Closure

Clinical and surgical pearls and pitfalls

Harvest the tendinous and tibial plug portions of the bone–patellar tendon–bone autograft with the leg in flexion.
Harvest of the patellar plug in extension with the foot on a sterile Mayo stand will allow the superior skin flaps to be more easily mobilized.
Changing hands while the saw is used during graft harvest enhances visualization of the bone cuts.
Make a triangular cut for the tibial bone plug and a trapezoidal cut for the patellar bone plug. The latter avoids penetration into the patellar articular surface.
Ten-millimeter by 20-mm patellar bone plugs are sized for both the transtibial and medial portal femoral independent drilling techniques. The shorter length femoral bone plug will assist with navigating the bone block through the intercondylar notch when docking the graft and will allow greater flexibility with reconciling graft/tunnel mismatch. Notch preparation should be carried out with a motorized shaver and arthroscopic electrocautery device. Do not use a burr to perform osteoplasty, because this may obliterate the landmarks used to facilitate anatomic femoral tunnel placement.
For a medial portal femoral independent drilling technique, the use of a curved femoral aimer, flexible guide pin, and reamers will facilitate visualization without the resource challenges with maintaining a hyperflexed position and the change in orientation hyperflexion induces in the landmarks for femoral ACL tunnel placement.
While the bone–patellar tendon–bone ACL graft is pulled through the tibial tunnel, a probe or looped arthroscopic suture retriever should be used to help lever the pulling suture at the intra-articular entrance of the tibial tunnel. This will keep the pulling vector in line with the tibial tunnel, as well as keeping the sutures from abrading on the intra-articular tunnel entrance.
Graft-tunnel mismatch can be a concern with the medial portal femoral independent technique, because the femoral tunnel, femoral bone plug, and intra-articular length of the ACL will likely be shorter than when a transtibial technique is used. Therefore, we recommend creating a longer tibial tunnel to help manage this.

Anterior cruciate ligament (ACL) rupture commonly occurs among both professional and amateur athletes. Because the ACL is the primary restraint to anterior displacement of the tibia on the femur and a secondary stabilizer to tibial rotation, an ACL-deficient knee can lead to meniscal injury, functional instability, and early-onset osteoarthritis. These are potentially devastating consequences in certain populations of patients, especially in athletes who participate in cutting or pivoting activities. The ACL is the most frequently torn knee ligament requiring surgical repair, and more than 200,000 ACL reconstructions are performed each year in the United States.

A variety of decisions must be made when performing ACL reconstruction, including surgical technique, graft source, and graft fixation. Graft options may include autograft (patellar tendon, hamstring, and quadriceps tendon) or allograft (bone–patellar tendon–bone, Achilles tendon, and posterior and anterior tibialis tendon) tissue. The patellar tendon autograft has been the most commonly used graft during the last 20 years and is the graft of choice of physicians treating National Collegiate Athletic Association (NCAA) Division 1A and professional athletes. This is because of the graft’s ready accessibility, good mechanical strength, bone healing, and interference screw fixation. One of our primary goals in ACL reconstruction is to reapproximate the native ACL anatomy with respect to tibial and femoral tunnel placement. This anatomy has been well described in the literature. Several surgical techniques for drilling the femoral and tibial ACL tunnels can be used to accomplish this, including transtibial drilling, medial portal femoral independent drilling, outside-in femoral independent drilling, and two-incision ACL reconstruction. This chapter details the surgical technique for anatomic transtibial and medial portal femoral independent endoscopic ACL reconstruction with a bone–patellar tendon–bone autograft.

Preoperative considerations

History

The diagnosis of ACL injury is often apparent from the characteristic history that is provided by the patient. Typical descriptions of the injury mechanism include the following:

A noncontact injury that occurred during a change-of-direction maneuver, such as pivoting, cutting, or decelerating.
The patient may have noted knee hyperextension during an awkward landing.
A “pop” was heard or felt during the event.
Acute onset of significant swelling that often developed in minutes to hours.
A sensation of instability limits the ability to return to play.
The patient reports catching or locking (signifies meniscal disease, stump impingement, or loose bodies).
The patient’s age, history of anterior knee pain or patellar instability and other previous knee injury, and contralateral knee instability are critical to decision making.

Physical examination

The physical examination is essential in the diagnosis of ACL injury and the evaluation of associated pathologic changes, such as meniscal or chondral damage and associated ligamentous injury.

Assessment of the injured knee includes evaluation of gait, limb alignment, presence of an effusion, knee range of motion, patellar instability, anterior knee or joint line tenderness, and varus or valgus laxity. The Lachman and pivot-shift tests remain the most sensitive and specific examinations for the evaluation of ACL injury. A positive result of the posterior drawer test, posterior sag, or increased tibial external rotation at 30 or 90 degrees signals the presence of associated posterior cruciate ligament (PCL) or posterolateral corner injury. Instrumented knee arthrometry with anterior drawer testing at 30 degrees can be helpful in confirming an ACL injury when the side-to-side difference is greater than 3 mm.

Imaging

Radiography

Despite recent trends, plain radiographic imaging remains critical in the initial evaluation of patients with suspected ACL injuries. Weight-bearing radiographs are essential to visualize joint space, notch architecture, and bone alignment. Lateral radiographs may reveal an avulsion of the tibial eminence or lateral capsule/anterolateral ligament (Segond fracture). Radiographic views commonly used in evaluating patients with knee ligament injuries include the following:

Weight-bearing anteroposterior radiograph in full extension
Weight-bearing posteroanterior 45-degree flexion radiograph
Non–weight-bearing 45-degree flexion lateral view
Axial view of the patellofemoral joint (Merchant view)

Magnetic resonance imaging

Magnetic resonance imaging is performed to evaluate the ACL, PCL, medial collateral ligament, lateral collateral ligament, menisci, and associated articular cartilage injury.

Indications and contraindications

The ideal candidate for an ACL reconstruction with patellar tendon autograft is a young, active patient with minimal effusion, full range of motion, and no patellar tendon disease. In addition, patients with symptomatic intra-articular disease, such as meniscal injury or loose bodies, may benefit from earlier surgical intervention. Of note, it is vital to educate the patient concerning the risks and benefits of the various graft options for the patient to make the final informed decision. For example, patients in certain professions, such as roofers and carpet layers, should be counseled about the increased incidence of discomfort with kneeling.

ACL reconstruction with a patellar tendon autograft is relatively contraindicated in patients with degenerative joint disease, in patients with a history of patellar tendon disease, and in those patients who are sedentary, inactive, or elderly. In addition, patients who have limited motion preoperatively or who are unable to comply with a rigorous postoperative protocol are poor candidates as well. Patients with a history of anterior knee pain or pain with kneeling should be advised to choose a different graft option. Furthermore, ACL reconstruction in the skeletally immature patient remains a challenge and requires extensive discussion of the risks and benefits involved. In patients with significant growth remaining, soft tissue grafts such as hamstring, rather than bone–patellar tendon–bone grafts, are thought to pose less risk of premature physeal closure.

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