Tears of the anterior cruciate ligament (ACL) are some of the commonest conditions seen and treated in my practice.
The natural ACL is made up of 2 anatomically and functionally distinct bundles. They are named the anteromedial bundle (AMB) and the posterolateral bundle (PLB) based on the position of the fibres in the central part of the knee joint.
ACL reconstruction surgeons have traditionally reconstructed the larger and functionally more important bundle and that was the anteromedial bundle (AMB). The understanding of the role of the posterolateral bundle (PLB) was lacking and the ability to reconstruct this bundle was not well accepted until recent years.
Through cadaveric knee anatomical dissection studies as well as biomechanical studies, sports and knee surgeons now have a better understanding of the importance of the once neglected posterolateral bundle (PLB) of the ACL.
Criticism of Single Bundle ACL Reconstructions
Biomechanical studies with cadaver knees
- 1 bundle ACL reconstruction cannot completely restore the normal anterior laxity
- 1 bundle ACL reconstruction has no effect on the rotatory instability
Woo et al: JBJS, 84A:907, 2002
Yagi, et al: AJSM, 30: 660, 2002
Kinematic analyses with patients
- 1 bundle ACL reconstruction cannot improve the rotatory instability during walking or running, independent of the graft (BTB, Hamstring, etc)
Georgoulis et al: AJSM, 31: 75, 2003
Ristanis et al: Arthroscopy, 21: 1323, 2005
Chouliaras et al: AJSM, 35:189, 2007
Tashman et al: Clin Orthop, 454: 66, 2007
What Are The Roles of Each ACL Bundle?
Posterolateral bundle (PLB) acted dominantly in extension, while the anteromedial bundle (AMB) mainly resisted against anterior tibial load in flexion. Hence each bundle have specific role in providing knee stability at different knee flexion angle.
Comparing Single Bundle to Double Bundle ACL Reconstructions
8 papers showing Double Bundle ACL Reconstruction is Clinically Better than Single Bundle ACL Reconstruction
2006 Yasuda et al: Arthroscopy (level 2) n = 72
2007 Agllieti et al: CORR (level 2) n = 75
2007 Yagi, Kurosaka, et al: CORR (level 1) n = 60
2007 Jarvela: KSSTA (level 1) n = 65
2007 Muneta et al: Arthroscopy (level 1) n = 68
2008 Siebold et al: Arthroscopy (level 1) n = 70
2008 Streich et al: KSSTA (level 1) n = 50
2008 Kondo, Yasuda, et al: AJSM (level 2) n = 328