title: Deltoid muscle shape analysis with magnetic resonance imaging in patients with chronic rotator cuff tears.
abstract: BACKGROUND
  It seems appropriate to assume, that for a full and strong global shoulder function a normally innervated and active deltoid muscle is indispensable. We set out to analyse the size and shape of the deltoid muscle on MR-arthrographies, and analyse its influence on shoulder function and its adaption (i.e. atrophy) for reduced shoulder function.
  
  
  METHODS
  The fatty infiltration (Goutallier stages), atrophy (tangent sign) and selective myotendinous retraction of the rotator cuff, as well as the thickness and the area of seven anatomically defined segments of the deltoid muscle were measured on MR-arthrographies and correlated with shoulder function (i.e. active abduction). Included were 116 patients, suffering of a rotator cuff tear with shoulder mobility ranging from pseudoparalysis to free mobility. Kolmogorov-Smirnov test was used to determine the distribution of the data before either Spearman or Pearson correlation and a multiple regression was applied to reveal the correlations.
  
  
  RESULTS
  Our developed method for measuring deltoid area and thickness showed to be reproducible with excellent interobserver correlations (r = 0.814-0.982).The analysis of influencing factors on active abduction revealed a weak influence of the amount of SSP tendon (r = -0.25; p < 0.01) and muscle retraction (r = -0.27; p < 0.01) as well as the stage of fatty muscle infiltration (GFDI: r = -0.36; p < 0.01). Unexpectedly however, we were unable to detect a relation of the deltoid muscle shape with the degree of active glenohumeral abduction. Furthermore, long-standing rotator cuff tears did not appear to influence the deltoid shape, i.e. did not lead to muscle atrophy.
  
  
  CONCLUSIONS
  Our data support that in chronic rotator cuff tears, there seems to be no disadvantage to exhausting conservative treatment and to delay implantation of reverse total shoulder arthroplasty, as the shape of deltoid muscle seems only to be influenced by natural aging, but to be independent of reduced shoulder motion.
authors: Orthopaedic Department, Balgrist University Hospital, University of Zurich, Rämistrasse 71, 8006, Zurich, Switzerland.
authors: Dominik C
authors: DC
authors: Meyer
authors: Stefan
authors: S
authors: Rahm
authors: Mazda
authors: M
authors: Farshad
authors: Georg
authors: G
authors: Lajtai
authors: Karl
authors: K
authors: Wieser
mesh_terms: D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001175:Arthrography; D001178:Arthroplasty; D002908:Chronic Disease; D057645:Deltoid Muscle / Q000473:pathology*; D005260:Female; D006801:Humans; D022125:Lacerations; D008279:Magnetic Resonance Imaging; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular; D012189:Retrospective Studies; D017006:Rotator Cuff / Q000473:pathology*; D000070636:Rotator Cuff Injuries; D012782:Shoulder / Q000473:pathology*; D012785:Shoulder Joint / Q000473:pathology / Q000601:surgery; D013708:Tendon Injuries / Q000473:pathology* / Q000628:therapy; D013997:Time Factors; D016896:Treatment Outcome
references: Clin Orthop Relat Res. 2000 Jun;(375):250-7
references: 10853176
references: Clin Orthop Relat Res. 1987 Jun;(219):15-20
references: 3581565
references: Invest Radiol. 1998 Mar;33(3):163-70
references: 9525755
references: J Shoulder Elbow Surg. 1998 Jul-Aug;7(4):393-6
references: 9752650
references: J Shoulder Elbow Surg. 2007 Nov-Dec;16(6):815-20
references: 17931906
references: Pflugers Arch. 1983 Dec;399(4):275-9
references: 6664830
references: Am J Sports Med. 2012 Mar;40(3):606-10
references: 22174340
references: Clin Orthop Relat Res. 1987 Jan;(214):160-4
references: 3791738
references: J Shoulder Elbow Surg. 1999 Nov-Dec;8(6):599-605
references: 10633896
references: Clin Orthop Relat Res. 2001 May;(386):222-5
references: 11347840
references: J Bone Joint Surg Am. 2006 Apr;88(4):800-5
references: 16595470
references: J Bone Joint Surg Am. 2005 Jul;87(7):1476-86
references: 15995114
references: Clin Orthop Relat Res. 1994 Jul;(304):78-83
references: 8020238
references: J Anat. 2011 Feb;218(2):185-90
references: 21118198
references: Am J Sports Med. 2011 Jul;39(7):1456-61
references: 21350068