Two-Tunnel Single-Bundle Acl Reconstruction

Two-Tunnel Single-Bundle Acl Reconstruction

Mark E. Steiner

Aaron Gardiner

ACL reconstruction techniques have undergone an evolution over the past few decades both in terms of graft choice and in surgical techniques. The historical “gold standard” technique was considered by many to be a patellar tendon autograft placed with a transtibial drilling technique. The transtibial technique replaced the older technique of outside-in femoral drilling and certainly increased the ease of femoral tunnel placement. However, this ease came at the expense of significant constraint in femoral tunnel placement. Over the past several years, there have been two major technical developments in ACL reconstruction. The first is the use of medial portal drilling for the femoral tunnel that gives the surgeon increased flexibility in tunnel placement compared with a transtibial technique. The second is the improved understanding of the native ACL anatomy, which has led to both a refinement of the single-bundle technique and the development of the double-bundle technique, which may more closely reproduce the native ACL anatomy.

Good results can be achieved using various grafts including patellar tendon autografts, hamstring autografts, quadriceps tendon autografts, and various allografts. More critical than graft selection appears to be surgical technique including tunnel placement, graft tensioning, and fixation technique. An accelerated rehabilitation with no restrictions on range of motion and weight bearing as tolerated are standards for all reconstruction techniques.

Despite the overall success of getting most patients back to athletic activity, several areas of concern remain with current ACL reconstruction techniques. First is that an estimated 10% to 30% have residual symptomatic instability (1, 2). This is the patient who has a Lachman test with a solid end point, but a mildly positive pivot shift test and functional instability during athletic activity. Second, there is a relatively high reinjury rate among young athletic patients for whom a reoperation rate of over 25% has been reported (3). Third, despite a successful ACL reconstruction and a stable knee that allows a return to pivoting activities, many patients develop degenerative changes in the long term (4). Fourth, modern analysis has shown that kinematic abnormalities remain in clinically stable knees (5, 6 and 7). Certainly, despite intensive study and many years of refinement, the current techniques of ACL reconstruction leave room for significant improvement.

Recent research has raised significant concerns with conventional transtibial drilling in regard to knee stability. Howell (8) in 2001 demonstrated that conventional transtibial drilling often produced vertical grafts that resulted in loss of motion and residual anterior laxity. Similarly, a cadaver study by Woo (9) in 2002 showed that a single-bundle reconstruction placed with a conventional transtibial drilling technique was unable to restore normal laxity.

Subsequent biomechanical studies have demonstrated that the residual laxity of transtibial techniques may be avoided with a double-bundle graft. The biomechanical rationale for this procedure is that while a conventional transtibial single-bundle graft may restore anterior laxity and produce a knee with an end point during Lachman examination, there may still be residual laxity with a positive pivot shift and instability due to rotatory loads (10, 11 and 12).

One limitation of some of the comparisons of double-bundle reconstructions to single-bundle reconstructions
is that these studies used a conventional transtibial drilling with single-bundle grafts that did not optimize tunnel placement in the center of the anatomic footprints. Recent work by the senior author (M.E.S.) in a cadaver model has shown that a single-bundle graft placed with independent drilling in the center of the anatomic footprints can improve stability compared with a transtibial graft and can provide stability equivalent to a double-bundle graft (13, 14).

The premise of a single-bundle anatomic reconstruction is that the limitations of transtibial drilling are the basis for single-bundle grafts not restoring functional stability. Anatomic placement of a single-bundle graft is a means of increasing stability rather than increasing the number of grafts crossing the knee joint. In order to place single-bundle grafts centered in the anatomic footprints, independent drilling of the tibial and femoral tunnels is required (15). This chapter will review the technique for single-bundle ACL reconstruction, including patient selection, operative techniques, and rehabilitation.


Most patients with an ACL injury will give a history of acute trauma. Patients often report hearing a “pop” at the time of injury. Often this will be a noncontact injury during a deceleration and rotation maneuver. Patients generally are unable to continue their activity, develop a hemarthrosis within 24 hours, and seek medical attention. Patients with a chronic ACL tear will often give a history of recurrent episodes of instability, especially with cutting or pivoting activities.

On examination, an effusion will usually be present. This may not be the case during an initial on-field examination or in chronic cases. A Lachman test will reveal increased anterior translation with no firm end point. This examination should be performed on both knees for comparison. The pivot shift test will reveal a greater shift in the ACL injured knee compared with the contralateral normal knee, but muscle spasm may impair the examination.

A complete knee examination should be performed as many associated injuries may also be present. Evaluation of the collateral ligaments, posterolateral corner, posterior cruciate ligament (PCL), and menisci is important. Particularly in chronic or revision cases, an evaluation of limb alignment should be performed, as undiagnosed malalignment is a potential cause of failure of reconstruction.

Patients with a suspected ACL injury should initially be evaluated with a series of plain radiographs. Although these will generally be normal, they are useful in ruling out fracture in the setting of an acute injury with hemarthrosis. A Segond fracture, a small bony avulsion of the lateral tibial plateau, can sometimes be seen and is strongly associated with ACL injury. Generally, anteroposterior (AP), lateral, and sunrise views are sufficient in the case of an acutely injured knee. In cases of chronic ACL tears or in revision cases, the surgeon should be alert to the possibility of malalignment and full-length standing films of both lower extremities should be evaluated if malalignment is suspected.

CT scan does not have a major role in cases of acute ACL injury, but it may be helpful in revision cases to accurately identify tunnel positions and possible tunnel widening.

MRI is the most useful imaging modality for diagnosis of ACL injury. The torn ACL is usually identified by the interruption of the fibers and the abnormal horizontal alignment of the ligament. Associated injuries, including meniscal tears, chondral injuries, and ligamentous injuries, can also be identified. In over 80% of patients, a bone bruise will be identified, usually in the lateral compartment. If these bone bruises are absent, the clinician may suspect the injury is chronic or the possibility of another injury.


Treatment for ACL tears should be individualized to the patient. In general, ACL reconstruction allows a return to sports and other activities that require cutting and pivoting. For some patients, especially older patients that do not participate in these activities, a nonoperative approach may be the preferred treatment. Certainly, a trial of nonoperative treatment, consisting of physical therapy and a gradual return to activity, is appropriate for the older, low-demand patient. If this patient has instability during their normal activities after completing a rehabilitation program, at that point they would be a candidate for ACL reconstruction. The decision to undergo ACL reconstruction should be individualized after a thoughtful discussion between the surgeon and the patient regarding the risks, benefits, and expected outcomes of the procedure.

Operative treatment should be offered to all patients who desire to return to cutting or pivoting athletic activities. An ACL tear is a season-ending injury and allowing an athlete to return to competition with an unstable knee exposes the patient to a significant risk of meniscal and chondral injury that could likely be avoided by ACL reconstruction.

Timing of ACL reconstruction has received attention in the sports medicine literature with some conflicting reports as to when it is safe to perform ACL reconstruction after an injury. It is important to assess the “personality” of the knee injury and to recognize the large variation among patients. Prior to performing ACL reconstruction, the knee effusion and swelling should have largely resolved, and the range of motion, particularly extension, should be regained. A strong quadriceps contraction is critical to the return of full extension and some patients have severe quadriceps inhibition with this injury. There is a rare patient who will have an impinging torn ACL that requires debridement in a separate arthroscopic procedure to facilitate the return of
full extension. A continuous passive motion (CPM) machine can also be helpful in rare cases where loss of flexion and parapatellar fibrosis limits flexion. If patients are progressing slowly with their recovery prior to surgery, reconstruction may be delayed for a period of weeks to allow the soft tissues around the knee to recover.


Our preferred technique is an anatomic single-bundle reconstruction with independent drilling of the tibial and femoral tunnels. Based on the clinical situation, either autograft (either hamstring or patellar tendon) or an allograft (usually tibialis anterior tendon) may be used. The decision on graft is based on patient preference, but a patellar tendon graft is preferred for very unstable knees or in a young athlete with a strong quadriceps who plays the most demanding sports. Allografts are used when an early return to daily activities is important and the demands on the knee are less. Hamstring grafts are used for competitive and recreational athletes who prefer autograft and may not rehabilitate well with the disability of a patellar tendon autograft harvest. The same anatomic single-bundle technique can be used regardless of graft choice.

A standard operating table is used with the foot of the bed left extended. A leg holder is not used as it often prevents adequate flexion of the knee when drilling through the anteromedial portal. Instead, we use three posts to support the operative leg in either 90° or full flexion (Fig. 70.1A,B). A vertical post is placed on the lateral side of the thigh to allow access to the medial compartment as well as to prevent hip abduction when the knee is flexed. Two posts are placed across the bed to serve as footrests to maintain the two flexion angles most often needed during the procedure (90° and >125°). This setup allows the knee to be held in either position without any assistance, which frees the hands of both the surgeon and the assistant. Regardless of the setup, if an anteromedial portal drilling technique will be used, it is essential that the knee can be flexed adequately.

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Jul 22, 2016 | Posted by in ORTHOPEDIC | Comments Off on Two-Tunnel Single-Bundle Acl Reconstruction

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