Chapter 24 Anatomical Double-Bundle Anterior Cruciate Ligament Reconstruction with a Semitendinosus Hamstring Tendon Graft

Introduction

Anterior cruciate ligament (ACL) reconstruction is one of the most frequently performed knee surgical procedures today. Through the years, the various technical modifications together with the introduction of better instrumentations have led to the improved outcome currently reported in the various orthopaedic literature.

Conventional techniques of reconstructing the torn ACL employ the use of either a bone–patellar tendon or hamstring graft. The majority of these reconstruction techniques, however, basically reconstructs the anteromedial (AM) bundle of the cruciates as the femoral tunnel is placed between the 10- and 11-o’clock position for the right knee (or 1- and 2-o’clock position for the left knee). Although good results have been generally demonstrated concurrent with its ability to restore the knee’s anteroposterior (AP) stability, questions remain regarding its efficiency in restoring rotational stability.¹ Recently, the performance of an anatomical double-bundle reconstruction technique has generated renewed interests as several in vitro analyses demonstrated better results in terms of restoring knee rotational stability.²^–⁸

Performing an anatomical double-bundle reconstruction usually entails the use of both the semitendinosus (ST) and gracilis (Gr) autografts, requiring the use of independent femoral and tibial fixations.^5,^9,¹⁰ With this technique, therefore, the surgery becomes more costly with the additional fixation required. Moreover, with the use of both the ST/Gr, hamstring strength deficits can become apparent, as has been demonstrated by previous studies.^3,^4,¹¹

This section illustrates a modification of the anatomical double-bundle technique using a single ST autograft with independent femoral but single tibial fixation system. This double-bundle, single-tendon (DBST) technique enables the surgeon to achieve an anatomical reconstruction without compromising the hamstring function while at the same time avoiding the use of additional fixations limiting the cost of the surgery.

Anatomy of the Anterior Cruciate Ligament

Anatomical studies have shown that the ACL consists of two functional bundles, the AM and the posterolateral (PL) bundle, whose nomenclature is related to their insertion in the tibial plateau.^1,¹² These two bundles are already identifiable between the 16th to 22nd weeks of fetal development. Analyzing the insertions of these two bundles reveals that they do not lie on the same coronal plane; the AM bundle originates more proximally than the PL bundle. Biomechanically, the AM bundle tightens in flexion while the PL bundle slackens. On the other hand, the PL bundle tightens in extension while the AM bundle loosens.^1,¹³ The ACL attaches to the femur and tibia as a collection of fascicles that fan out as they approach their insertions sites.

Scientific Rationale

Early cadaveric investigations performed by Radford and Amis ¹ demonstrated the superior AP knee stability achieved through various ranges of flexion with a double-bundle reconstruction compared with single-bundle ACL reconstruction. Their investigation, however, did not include tests for rotational stability. Yamamoto et al,¹⁴ on the other hand, reported no significant differences between double-bundle and single-bundle ACL reconstruction of the PL bundle in terms of response to rotatory loads. However, single PL bundle reconstruction was found to be associated with increased anterior tibial translation with application of anterior loads. A more recent cadaveric study emphasized that single-bundle ACL reconstruction is mostly successful in restoring AP knee stability but is inadequate in controlling the combined rotatory loads of internal tibial torque and valgus torque.

In a biomechanical study by Yagi et al ⁶ restoration of the knee kinematics, particularly in terms of rotational control, was also demonstrated to be better with a double-bundle versus single-bundle reconstruction technique. Further in vivo studies by Tashman et al⁵ also revealed that single-bundle reconstruction sufficiently restores AP tibial translation but failed to provide rotational stability during dynamic loading.

In general, the available studies thus far have demonstrated that single-bundle ACL reconstruction can only partially restore the normal knee kinematics because it limits anterior translation but is unable to control pivot shift. In addition, biomechanical analysis of an anatomically reconstructed knee also demonstrated that anterior tibial translation for double-bundle reconstruction is significantly closer to that of an intact knee and produces better rotatory stability.^7,⁸