title: The deviation of the mechanical leg axis correlates with an increased hip alpha angle and could be a predictor of femoroacetabular impingement.
abstract: OBJECTIVE
  This study was designed to evaluate whether the mechanical axis deviation (MAD) of the leg correlates with an increased hip alpha angle as described by Nötzli, which is associated with femoroacetabular impingement (FAI).
  
  
  METHODS
  In a retrospective analysis, standing full-length anteroposterior radiographs were analysed in patients who suffered from symptomatic leg alignment. The study included 85 radiographs of 80 patients with an average age of 43.11 years (range 18-60 years). Five patients underwent a bilateral long-leg X-ray examination. All radiographs were transferred as Digital Imaging and Communications in Medicine data files from the Picture Archiving and Communications System into the OrthoPlanner software version 2.3.2. The radiographs were measured by one orthopaedic surgeon and one independent radiologist.
  
  
  RESULTS
  The mean value of the alpha angle of Nötzli was 61.43° (49.07-74.04°). A total of 57 (67%) radiographs showed a varus deviation, 25 (29.5%) had a valgus malalignment and three (3.5%) a straight leg axis. Of 82 radiographs, 40 (48.8%) had a moderate axis deviation with a MAD <15 or > - 15 mm and a mean alpha angle of 57.81°, and 42 (51.2%) with extended axis deviation of a MAD > 15 or < - 15 mm had a mean alpha angle of 62.93°; 40 (95.2%) of these 42 showed an alpha angle > 55°. The alpha angle was significantly increased in extended axis deviation compared to moderate axis deviation (P = 0.001).
  
  
  CONCLUSIONS
  This study confirmed that increased alpha angles were found significantly at higher degrees of axis deviation on the full-length radiograph. In cases of a MAD >15 or < - 15 mm and symptomatic coxalgia, diagnostic tests must be pursued for FAI.
authors.affiliation: Department of Orthopaedic Sports Surgery, St. Josef-Hospital, Ruhr University Bochum, Gudrunstr. 56, 44791, Bochum, Germany, m.lahner@klinikum-bochum.de.
authors.forename: Matthias
authors.initials: M
authors.lastname: Lahner
authors.forename: Nadine-Lucie
authors.initials: NL
authors.lastname: Jahnke
authors.forename: Sonja
authors.initials: S
authors.lastname: Zirke
authors.forename: Wolfram
authors.initials: W
authors.lastname: Teske
authors.forename: Gregor
authors.initials: G
authors.lastname: Vetter
authors.forename: Christoph
authors.initials: C
authors.lastname: von Schulze Pellengahr
authors.forename: Kiriakos
authors.initials: K
authors.lastname: Daniilidis
authors.forename: Marco
authors.initials: M
authors.lastname: Hagen
authors.forename: Lars Victor
authors.initials: LV
authors.lastname: von Engelhardt
mesh_terms: D000293:Adolescent; D000328:Adult; D001696:Biomechanical Phenomena / Q000502:physiology; D005260:Female; D057925:Femoracetabular Impingement / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006621:Hip Joint / Q000000981:diagnostic imaging* / Q000503:physiopathology; D006801:Humans; D007866:Leg / Q000000981:diagnostic imaging* / Q000502:physiology; D008297:Male; D008875:Middle Aged; D011237:Predictive Value of Tests; D011859:Radiography; D015203:Reproducibility of Results; D012189:Retrospective Studies; D012307:Risk Factors; D055815:Young Adult
references.citation: J Bone Joint Surg Br. 2006 Jun;88(6):727-9
references.pmid: 16720763
references.citation: Orthopade. 2004 Feb;33(2):122-34
references.pmid: 14872303
references.citation: Acta Orthop Scand. 2000 Aug;71(4):370-5
references.pmid: 11028885
references.citation: Int Orthop. 2013 May;37(5):783-8
references.pmid: 23456019
references.citation: Clin Orthop Relat Res. 2011 Feb;469(2):464-9
references.pmid: 20953854
references.citation: Radiology. 2005 Aug;236(2):588-92
references.pmid: 15972331
references.citation: Int Orthop. 2012 May;36(5):903-14
references.pmid: 22190060
references.citation: Clin Orthop Relat Res. 2007 Sep;462:115-21
references.pmid: 17589367
references.citation: Clin Orthop Relat Res. 2003 Dec;(417):112-20
references.pmid: 14646708
references.citation: Clin Orthop Relat Res. 2009 Mar;467(3):660-5
references.pmid: 19037709
references.citation: J Bone Joint Surg Am. 1985 Sep;67(7):1136-40
references.pmid: 4030836
references.citation: J Bone Joint Surg Br. 2002 May;84(4):556-60
references.pmid: 12043778
references.citation: Int Orthop. 2011 Oct;35(10):1427-35
references.pmid: 21755334
references.citation: Clin Orthop Relat Res. 2004 Jan;(418):67-73
references.pmid: 15043095
references.citation: Clin Orthop Relat Res. 2008 Feb;466(2):264-72
references.pmid: 18196405
references.citation: Arthritis Care Res (Hoboken). 2010 Sep;62(9):1319-27
references.pmid: 20853471
references.citation: Clin Orthop Relat Res. 2009 Mar;467(3):651-9
references.pmid: 19023635
references.citation: Unfallchirurg. 2005 Jan;108(1):9-10, 12-7
references.pmid: 15619064
references.citation: J Bone Joint Surg Br. 2010 Feb;92(2):209-16
references.pmid: 20130310
references.citation: Clin Orthop Relat Res. 2004 Jan;(418):54-60
references.pmid: 15043093
references.citation: J Bone Joint Surg Br. 2007 Oct;89(10):1309-16
references.pmid: 17957069
references.citation: J Pediatr Orthop. 1993 May-Jun;13(3):286-9
references.pmid: 8496358
references.citation: Lancet. 2012 Nov 17;380(9855):1768-77
references.pmid: 23021846
references.citation: J Bone Joint Surg Br. 2005 Jul;87(7):1012-8
references.pmid: 15972923
references.citation: J Orthop Res. 2005 Nov;23(6):1286-92
references.pmid: 15921872
references.citation: J Bone Joint Surg Am. 2010 Oct 20;92(14):2436-44
references.pmid: 20962194
references.citation: Clin Orthop Relat Res. 2013 Dec;471(12):3774-80
references.pmid: 23463288