KNEE Anatomic double-bundle ACL reconstruction restricts knee extension in knees with hyperextension M. Ettinger • M. Petri • D. Guenther • C. Liu • C. Krusche • E. Liodakis • U-V Albrecht • C. Krettek • M. Jagodzinski Received: 31 January 2012 / Accepted: 21 August 2012 Ó Springer-Verlag 2012 Abstract Purpose Double-bundle ACL reconstruction has been demonstrated to be at least as effective as single-bundle reconstruction in terms of restoring knee rotational and translational stability. Until now, the influence on knees with hyperextension has not been evaluated. It was the purpose of this study to evaluate whether double-bundle ACL reconstruction restricts extension in hyperextendable knees. Methods Hamstring tendon reconstructions of 10 human cadaveric knees with the ability of hyperextension (age: 48 ± 14 years) were performed as single bundle (SB) on one side and double bundle (DB) on the other side. A surgical navigation system (BrainLab, Germany) was used to assess the kinematics of each knee at the intact and reconstructed state. A difference with regard to the ante- rior-to-posterior translation (AP) and rotational stability at 30° of knee flexion, 90° of flexion and the hyperextension capability of each specimen was analysed. Results The difference in AP translation before and after the reconstruction was not significantly different in 30° and 90° of flexion (n.s). Both single- and double-bundle reconstructions restored the preoperative kinematics at 30° and 90° of knee flexion (n.s). The knee extension was 4° ± 1.8° with the intact ACL and 4° ± 1.7° after recon- struction in the SB group (n.s). The knee extension was 5° of hyperextension ± 1.1° with the intact ACL and 0° ± 0.4° after reconstruction in the DB group; the limi- tation of the extension was significantly larger in this group (p = 0.013). Conclusion Both single- and double-bundle ACL reconstruction techniques are capable of restoring knee anteroposterior and rotational stability. Double-bundle reconstructions significantly reduce knee extension in knees with hyperextension capability. Care must be taken when using double-bundle techniques in patients with knee hyperextension as this procedure may limit the knee extension after double-bundle ACL reconstruction. Keywords ACL Á Double-bundle Á Single-bundle Á Knee Á Navigation Introduction During most of the last century, reconstructions of the ACL were dedicated to isometric single-bundle techniques [5, 24]. Then, attention was drawn to the double-bundle nature of the ACL [20, 27]. Ever since, numerous studies have evaluated the benefits of this reconstruction technique compared with a single-bundle (isometric) approach in vitro[17, 18, 26, 27] and in vivo [14–16, 21, 25]: Even though there are studies that point to a biomechanical benefit of double-bundle reconstructions compared with single-bundle procedures [10, 17, 26], there is a lack of common opinion on the clinical benefits: Only Muneta et al. [16] report increased anteroposterior stability fol- lowing double-bundle reconstruction. However, this study M. Ettinger (&) Departent of Orthopaedic Surgery, Hannover Medical School, Anna-von-Borrie-Str. 1-7, 30625 Hanover, Germany e-mail: max@ettinger.info M. Petri Á D. Guenther Á C. Liu Á C. Krusche Á E. Liodakis Á C. Krettek Á M. Jagodzinski Trauma Department, Hannover Medical Scholol, Hanover, Germany U.-V. Albrecht Istitute for Legal Medicine, Hannover Medical School, Hanover, Germany 123 Knee Surg Sports Traumatol Arthrosc DOI 10.1007/s00167-012-2190-4