Single-bundle Versus Double-bundle Reconstruction and Anatomic Risk Factors for Anterior Cruciate Ligament Injury

The anterior cruciate ligament (ACL) is an important stabilising component of the knee that prevents the forward movement of the tibia and helps to maintain the rotational stability of the knee. It is well known that the ACL consists of two different fibres: the anteromedial (AM) fibre and the posterolateral (PL) fibre, each having a different function. Although both fibres contribute to anterior and rotational stability, the amount of support they provide depends largely on the degree of knee flexion. The AM fibre plays a key role in preventing forward movement of the tibia, particularly when the knee is flexed between 60 degrees and 90 degrees. In contrast, the PL fibre helps to maintain the stability of the knee both forwards and in terms of rotation when the knee is in an extended or almost straight position.

ACL injury is a common sports-related injury that is often managed with operative treatment. Various anatomical factors have been associated with noncontact ACL injuries. For many years, the single-bundle (SB) method, which reconstructs the AM fibre, has been the standard method for operative treatment. However, the double- bundle (DB) method more accurately replicates the natural anatomy of the ACL because it reconstructs both the AM and the PL fibres. The aim of the DB method is to give the knee better rotational and anterior stability compared to the SB method, especially at lower flexion angles.

The aim of this dissertation was to investigate anatomical risk factors for noncontact ACL injuries (IV) and to compare the SB and DB methods in a meta- analysis (I) and a long-term randomised controlled trial (RCT) design (II, III).

In study II and III, baseline data were collected between 4/2003 and 2/2008 at Hatanpää Hospital, Tampere, Finland. In total, 153 patients were randomly assigned to two different groups for ACL reconstruction with hamstring tendon (HT) autografts: the anatomic SB technique group (n = 78) and the anatomic DB technique group (n = 75). All surgical procedures were performed by a single experienced orthopaedic surgeon TJ. The rehabilitation protocol was standardised and evaluation included clinical tests, patient-reported outcome measures (PROMs) and osteoarthritis (OA) grading with x-ray.

In study IV, baseline data were collected between 2011 and 2015 at the UKK Institute, Tampere, Finland. Two hundred and eighty‐seven female athletes from basketball, floorball, ice hockey and volleyball completed a baseline physical examination, including measurements of anterior‐posterior (AP) knee laxity, knee hyperextension, generalised joint hypermobility (GJH), femoral anteversion, hamstring extensibility and navicular drop. Magnetic resonance imaging (MRI) was used to evaluate ACL tears. Baseline data were examined by two physiotherapists and one medical student.

The main finding of the meta-analysis (I) was that DB ACL reconstruction generally led to better recovery of knee stability and subjective outcomes than SB ACL reconstruction. For example, there were 1.49 to 2.66 times more positive pivot shift test results in the SB technique than in the DB technique, depending on which studies were included in the statistical analysis. However, no statistically significant differences between the two techniques were found in subgroup analysis of the MP technique. The main findings in Studies II and III were that DB ACL reconstruction leads to better International Knee Documentation Committee (IKDC) objective grading (p<0.001) compared to the SB technique and no differences were found between the surgical techniques in terms of osteoarthritis. Study IV concluded that anatomical baseline characteristics did not significantly contribute to the risk of noncontact ACL injuries.

In conclusion, based on our research and the recent literature, the DB ACL reconstruction technique outperforms the SB technique in terms of knee stability and IKDC objective grading. However, the differences between the two methods seem to be relatively small. Nevertheless, neither our studies nor any of the earlier studies found that the SB technique is superior to the DB technique.