Erratum to: Flat midsubstance of the anterior cruciate ligament with tibial "C"-shaped insertion site - Siebold, Rainer; Schuhmacher, Peter; Fernandez, Francis; Smigielski, Robert; Fink, Christian; Brehmer, Axel; Kirsch, Joachim (Knee Surgery Sports Traumatology Arthroscopy, 2014)