Anterior Cruciate Ligament Reconstruction: Hamstring Autograft/Single and Double Bundle Techniques

Peter S. Cha MD

Robin V. West MD

Freddie H. Fu MD

History of the Technique

Complete anterior cruciate ligament (ACL) ruptures can lead to recurrent knee instability, meniscal tears, and articular cartilage degeneration. Reconstruction of the ACL has become a common procedure, and good-to-excellent clinical results have been reported.¹^,²^,³^,⁴

The ideal graft for the ACL during reconstruction should have similar structural and biomechanical properties as the native ACL, permit secure fixation, allow for rapid biological incorporation, and limit donor site morbidity. Patellar tendon autografts are historically the most popular graft choice because of their strength characteristics, ease of harvest, rigid fixation, bone-to-bone healing, and good clinical outcomes. However, donor site morbidity of patellar tendon autografts has led to the investigation and use of alternative graft sources.

Hamstring grafts have gained recent popularity due to their ease of harvest, avoidance of injury to the extensor mechanism, improved soft tissue fixation devices, and decreased incidence of anterior knee pain. Some concerns regarding the use of hamstring autografts include their strength, potential elongation, fixation methods, and a greater length of time required for incorporation into the bone tunnels.

Biomechanical data have shown that the quadrupled hamstring tendon graft has a higher ultimate tensile load and stiffness than a 10-mm patellar tendon graft.⁵^,⁶^,⁷ The healing process of soft tissue grafts within the bone tunnels has been detailed.⁸ Healing of the site of the graft attachment may be responsible for most of the strength observed after transplantation. From a biologic standpoint, patellar tendon grafts, compared with soft-tissue grafts, have the advantage of bone-to-bone healing. Bone-to-bone healing is similar to fracture healing and is stronger and faster than soft tissue healing. The graft is usually incorporated into the host bone by 6 weeks during bone-to-bone healing. Soft tissue grafts usually take 8 to 12 weeks to incorporate into the host bone.

Histologic examination has demonstrated the formation of Sharpey-like fibers that extend between the bone and soft tissue graft between 4 and 12 weeks after reconstruction. Biomechanical testing has demonstrated a progressive increase in the strength of the tendon-to-bone interface over the first 12 weeks after implantation.⁸

Fixation of the graft is a crucial factor in ACL reconstruction. The fixation is the weak link during the initial 6- to 12-week period while healing of the graft to the host bone occurs. The graft must withstand the early aggressive rehabilitation that is recommended during this time period. It has been estimated that the forces during rehabilitation can be as high as 450 to 500 N.⁹ If the fixation is poor, the graft may slip or the fixation may fail altogether, resulting in an unstable knee. Fixation failure usually occurs at the tibial side.¹⁰

Fixation methods for hamstring grafts have dramatically expanded. There are currently many fixation methods available, including absorbable and nonabsorbable implants. During biomechanical testing, these soft-tissue fixation devices have been shown to have a higher load to failure than the “gold standard” metal interference screw fixation for the patellar tendon grafts.¹¹^,¹²

Indications and Contraindications

Our indications for ACL reconstruction include ACL deficient young patients who want to continue athletic competition, have recurrent instability with activities of daily living,
repairable meniscal tears, or multiligamentous knee injuries. We always review the graft options with the patient and have him or her select the graft of choice.

In our practice, we tend to use patellar tendon autografts in high-demand individuals who participate in cutting, pivoting, or jumping sports. We also favor the patellar tendon autograft in athletes who desire a “quick return to play.” Preexisting anterior knee pain and certain lifestyle activities (kneeling for work, religion) are relative contraindications to the patellar tendon autograft. Quadruple hamstring autograft is our preference in “lower” demand patients, recreational athletes, younger patients with open growth plates, and for cosmesis. Contraindications to the hamstring autograft include generalized increased ligamentous laxity, competitive sprinters (terminal flexion weakness), and a previous hamstring injury. We opt for the patellar tendon allograft in lower demand patients, older patients who prefer an easier rehabilitation, and in the multiple-ligament injured knee.

Recently, we have switched to a double bundle, or anatomic, ACL reconstruction, using hamstring autografts. Cadaveric and biomechanical studies have shown that the standard ACL reconstruction is successful in limiting anterior tibial translation but insufficient in controlling a combined rotatory load of internal and valgus torque.¹³ The anterior cruciate ligament is a collection of individual fascicles that attach to the femur and tibia over a broad area. The anteromedial bundle (AMB) originates from the proximal aspect of the femoral attachment and inserts on the anteromedial aspect of the tibial attachment. The posterolateral bundle (PLB) inserts onto the posterolateral aspect of the tibial attachment.¹⁴ When the knee is extended, the PLB is tight, while the AMB is moderately lax. With knee flexion, the AMB tightens and the PLB becomes lax.

Most ACL reconstructions focus on replacing only the AMB. The PLB has not received sufficient attention. An anatomic ACL reconstruction, or double bundle technique, has been described in recent biomechanical and outcome studies.¹⁵^,¹⁶^,¹⁷^,¹⁸^,¹⁹^,²⁰^,²¹^,²²^,²³ The normalized in situ force of the double bundle reconstructions have been shown to be more similar to the intact ACL when compared to the single bundle reconstructions.¹⁵^,¹⁶

With the biomechanical and clinical support for an anatomic ACL reconstruction, we recently started using a technique with the autogenous hamstrings to reproduce the two ACL bundles. We have been using this double bundle technique in our “high demand” athletes, ligamentously lax, and younger patients. The single bundle technique is reserved for lower-demand patients. We present our single bundle and double bundle (anatomic) ACL reconstruction techniques.

Surgical Technique

Preoperative Visit

The surgeon reviews the indications, expectations, rehabilitation, and potential complications with the patient and his or her family. The operative consent is then obtained by the surgeon. A registered nurse reviews the preoperative plan with the patient, including where to go and what to bring on the day of surgery, and when to stop anti-inflammatory use. A physical therapist fits the patient for an ELS (extension lock splint) brace, explains the brace and Cryocuff usage, and reviews the postoperative exercises (quadriceps set, straight let raises, heel slides, calf pumps).

Anesthesia

The choice of anesthesia is at the discretion of the anesthesiology team based on the age of the patient, the patient’s comorbid medical problems, and the previous anesthesia history of the patient. The anesthesia team typically chooses between a general anesthesia or a spinal anesthetic with concomitant intravenous (IV) sedation. If the anesthesiologist is at all concerned about airway management, then the general anesthesia is performed. At our center, there is an ongoing National Institutes of Health–funded grant that evaluates the effectiveness of preoperative femoral or sciatic nerve blocks for ACL reconstruction surgery. This prospective clinical trial randomizes the patients for femoral or sciatic nerve blocks and evaluates the pain scores postoperatively. The nerve blocks have not only been useful during the surgical procedure, but they offer 9 to 12 hours of postoperative pain relief. Prophylactic antibiotics are administered by the anesthesiologist.

Examination under Anesthesia

A thorough examination is performed to assess the range of motion, varus/valgus instability, posterolateral corner instability, posterior drawer, Lachman, and pivot-shift. If the history, radiographic studies, and examination correlate with an ACL tear, the graft is harvested prior to the arthroscopy. If there is any uncertainty in the diagnosis, an arthroscopy is performed first to assess the articular cartilage, menisci, and cruciate ligaments.

Positioning

The patient is positioned supine on the operating room table with the nonoperative extremity in a leg holder with the hip and the knee flexed to 90 degrees and the hip abducted and externally rotated. This extremity is well padded and loosely secured with a 6-inch elastic wrap. The foot of the table is dropped. A tourniquet is applied to the operative extremity and insufflated to 250 to 300 mmHg, depending on the patient’s size and systolic blood pressure. Once the tourniquet is inflated, the thigh is placed into the leg holder (Fig. 36-1).

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