title: The effect of the rotator interval on glenohumeral kinematics during abduction.
abstract: BACKGROUND
  The rotator interval (RI) has been exploited as a potentially benign point of entry into the glenohumeral (GH) joint. Bounded by the supraspinatus, subscapularis and coracoid process of the scapula, the RI is believed to be important in the shoulder's soft tissue balancing and function. However, the role of the RI in shoulder kinematics is not fully understood. The purpose of this study is to describe the effect of the RI on GH motion during abduction of the arm.
  
  
  METHODS
  Six shoulders from three cadaveric torsos were studied to assess the impact of changes in the RI during abduction under four conditions: Intact (Baseline), Opened, Repaired (repaired with side-to-side tissue approximation, no overlap) and Tightened (repaired with 1 cm overlap). For each group, the GH translation and area under the Curve (AUC) were measured during abduction using an intact cadaveric shoulder (intact torso).
  
  
  RESULTS
  GH kinematics varied in response to each intervention and throughout the entire abduction arc. Opening the RI caused a significant change in GH translation. The Repair and Tightened groups behaved similarly along all axes of GH motion.
  
  
  CONCLUSIONS
  The RI is central to normal GH kinematics. Any insult to the tissue's integrity alters the shoulder's motion throughout abduction. In this model, closing the RI side-to-side has the same effect as tightening the RI. Since suture closure may offer the same benefit as tightening the RI, clinicians should consider this effect when treating patients with shoulder laxity. This investigation provides an improved perspective on the role of the RI on GH kinematics during abduction. When managing shoulder pathology, surgeons should consider how these different methods of RI closure affect the joint's motion. In different circumstances, the surgical approach to the RI can be tailored to address each patient's specific needs.
authors.affiliation: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA. babak_haghpanah@yahoo.com.|Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, USA. babak_haghpanah@yahoo.com.
authors.forename: Babak
authors.initials: B
authors.lastname: Haghpanah
authors.affiliation: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA. kcwalley@gmail.com.
authors.forename: Kempland C
authors.initials: KC
authors.lastname: Walley
authors.affiliation: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA. andreashingsammer@hotmail.com.
authors.forename: Andreas
authors.initials: A
authors.lastname: Hingsammer
authors.affiliation: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA. ethan.harlow@med.uvm.edu.
authors.forename: Ethan R
authors.initials: ER
authors.lastname: Harlow
authors.affiliation: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA. roftadeh65@gmail.com.|Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, USA. roftadeh65@gmail.com.
authors.forename: Ramin
authors.initials: R
authors.lastname: Oftadeh
authors.affiliation: Department of Mechanical and Industrial Engineering, Northeastern University, Boston, MA, USA. vaziri@coe.neu.edu.
authors.forename: Ashkan
authors.initials: A
authors.lastname: Vaziri
authors.affiliation: Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. aramappa@bidmc.harvard.edu.
authors.forename: Arun J
authors.initials: AJ
authors.lastname: Ramappa
authors.affiliation: Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. jpdeange@bidmc.harvard.edu.
authors.forename: Joseph P
authors.initials: JP
authors.lastname: DeAngelis
authors.affiliation: Center for Advanced Orthopaedic Studies, Beth Israel Deaconess Medical Center, Harvard Medical School, 330 Brookline Avenue, RN115, Boston, MA, 02215, USA. anazaria@bidmc.harvard.edu.|Carl J. Shapiro Department of Orthopaedic Surgery, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA. anazaria@bidmc.harvard.edu.
authors.forename: Ara
authors.initials: A
authors.lastname: Nazarian
mesh_terms: D001696:Biomechanical Phenomena / Q000502:physiology; D006801:Humans; D008297:Male; D008875:Middle Aged; D016059:Range of Motion, Articular / Q000502:physiology*; D012371:Robotics / Q000379:methods; D017006:Rotator Cuff / Q000473:pathology / Q000502:physiology* / Q000601:surgery; D012785:Shoulder Joint / Q000473:pathology / Q000502:physiology* / Q000601:surgery
references.citation: Am J Sports Med. 1995 Sep-Oct;23(5):557-63
references.pmid: 8526270
references.citation: J Orthop Surg Res. 2013;8:24
references.pmid: 23883431
references.citation: J Biomech. 2011 May 17;44(8):1543-52
references.pmid: 21481879
references.citation: Gait Posture. 2005 Feb;21(2):226-37
references.pmid: 15639401
references.citation: Arthroscopy. 2007 Jun;23(6):583-92
references.pmid: 17560472
references.citation: Bone Joint Res. 2012 May 01;1(5):78-85
references.pmid: 23610675
references.citation: J Bone Joint Surg Am. 2000 Jul;82-A(7):991-1003
references.pmid: 10901314
references.citation: J Bone Joint Surg Am. 2008 Jan;90(1):136-44
references.pmid: 18171968
references.citation: J Shoulder Elbow Surg. 2008 Jan-Feb;17(1):132-8
references.pmid: 18036848
references.citation: Clin Orthop Relat Res. 1987 Oct;(223):44-50
references.pmid: 3652591
references.citation: Mayo Clin Proc. 1998 Jun;73(6):508-15
references.pmid: 9621856
references.citation: J Shoulder Elbow Surg. 1996 Jan-Feb;5(1):41-6
references.pmid: 8919441
references.citation: J Shoulder Elbow Surg. 1994 Nov;3(6):353-60
references.pmid: 22958839
references.citation: J Biomech. 2005 May;38(5):981-992
references.pmid: 15844264
references.citation: Semin Musculoskelet Radiol. 2015 Jul;19(3):243-53
references.pmid: 26021585
references.citation: J Bone Joint Surg Am. 1992 Jan;74(1):53-66
references.pmid: 1734014
references.citation: J Shoulder Elbow Surg. 1992 May;1(3):140-50
references.pmid: 22971606
references.citation: J Shoulder Elbow Surg. 2010 Oct;19(7):1056-62
references.pmid: 20471865
references.citation: Clin Orthop Relat Res. 1993 Jun;(291):75-84
references.pmid: 8504617
references.citation: J Biomech. 1998 Jan;31(1):93-6
references.pmid: 9596544
references.citation: J Shoulder Elbow Surg. 2013 Jul;22(7):986-92
references.pmid: 23313371
references.citation: Bull Hosp Jt Dis (2013). 2013;71 Suppl 2:94-100
references.pmid: 24328589
references.citation: J Bone Joint Surg Am. 1981 Jul;63(6):863-72
references.pmid: 7240326
references.citation: Injury. 2010 Oct;41(10):1075-8
references.pmid: 20621294
references.citation: Arthroscopy. 2004 Dec;20(10):1044-9
references.pmid: 15592233