title: Kinematic analysis of the flexion axis for correct femoral component placement.
abstract: OBJECTIVE
  This study evaluates a new method for intraoperative determination of femoral component rotation by a navigation system (flexion axis, FA) driven by joint stability over the range of motion.
  
  
  METHODS
  Seventy-five patients were treated with a navigated total knee replacement. Intraoperatively, the posterior condylar axis (PCA), the Whiteside's line (WL), and the surgical epicondylar axis (EA) were palpated, the flexion gap (FG) was determined, and the FA was calculated. The anatomical landmarks, lines, and angles were determined based on a postoperative computed tomography in all knees. The femoral rotation was intraoperatively determined by the surgeon based on the knowledge of the EA, the PCA, and the FG but not the FA.
  
  
  RESULTS
  The deviation of the palpated EA was 3.5° [0°-13.8°], of the PCA externally rotated by 3° was 2.2° [0°-9.6°], of the WL was 3.8° [0.1°-10.0°], of the FG was 2.5° [0.2°-8.8°], and of the FA was 2.5° [0°-10.0°].
  
  
  CONCLUSIONS
  The FA is a new functionally acquired axis for the determination of optimal femoral component alignment. Whether the FA leads to clinically superior results must be clarified by subsequent studies.
authors: Department of Orthopaedic, Center for Musculoskeletal Surgery, Charité-University Medicine Berlin, Charitéplatz 1, 10117 Berlin, Germany. Georg.Matziolis@Charite.de
authors: Georg
authors: G
authors: Matziolis
authors: Sascha
authors: S
authors: Pfiel
authors: Georgi
authors: G
authors: Wassilew
authors: Hinrich
authors: H
authors: Boenicke
authors: Carsten
authors: C
authors: Perka
references: Clin Orthop Relat Res. 2001 Nov;(392):46-55
references: 11716424
references: J Rheumatol. 2000 Jul;27(7):1745-52
references: 10914862
references: Arch Orthop Trauma Surg. 2008 Jun;128(6):561-6
references: 18004577
references: J Arthroplasty. 2009 Feb;24(2):263-71
references: 18534422
references: Clin Orthop Relat Res. 1999 Oct;(367):39-42
references: 10546596
references: Clin Orthop Relat Res. 2006 Nov;452:35-43
references: 16967035
references: Clin Orthop Relat Res. 2002 Oct;(403):143-52
references: 12360020
references: J Arthroplasty. 2008 Sep;23(6):879-85
references: 18555651
references: Orthopade. 2006 Aug;35(8):848-52
references: 16741750
references: Knee Surg Sports Traumatol Arthrosc. 2011 Jul;19(7):1077-81
references: 21161176
references: Orthop Traumatol Surg Res. 2009 Sep;95(5):365-72
references: 19592323
references: Knee. 2005 Aug;12(4):293-6
references: 16026698
references: Clin Orthop Relat Res. 1999 Sep;(366):155-63
references: 10627729
references: Clin Biomech (Bristol, Avon). 2010 May;25(4):352-8
references: 20117864
references: J Bone Joint Surg Br. 2004 Apr;86(3):372-7
references: 15125124
references: Clin Orthop Relat Res. 2004 Sep;(426):180-6
references: 15346071
references: Surg Radiol Anat. 2003 Jul-Aug;25(3-4):330-4
references: 12920572
references: J Arthroplasty. 2001 Jun;16(4):476-82
references: 11402411
references: Clin Orthop Relat Res. 2001 Nov;(392):38-45
references: 11716411
references: J Orthop Sci. 1998;3(4):194-8
references: 9662661
references: Clin Orthop Relat Res. 2002 Nov;(404):7-13
references: 12439231
references: Orthopade. 2003 Jun;32(6):469-76
references: 12819885
references: J Bone Joint Surg Am. 2007 Feb;89(2):236-43
references: 17272435
references: Acta Orthop Scand. 2004 Feb;75(1):74-7
references: 15022812
references: Knee Surg Sports Traumatol Arthrosc. 2002 May;10(3):194-7
references: 12012038
references: J Bone Joint Surg Br. 2007 Nov;89(11):1528-33
references: 17998196
references: J Arthroplasty. 1998 Oct;13(7):812-5
references: 9802670
references: Clin Orthop Relat Res. 2007 Sep;462:137-42
references: 17563704