title: Shoulder instability in the setting of bipolar (glenoid and humeral head) bone loss: the glenoid track concept.
abstract: BACKGROUND
  An assortment of variables has been used in predicting anterior shoulder instability resulting from pathologic engagement of Hill-Sachs lesions on the glenoid. The glenoid track is a unique biomechanical model that relates both Hill-Sachs and bony Bankart lesions to predict shoulder engagement. We examined the glenoid track concept to determine if it provides a model that unifies glenoid rim and humeral head bone loss in predicting engagement.
  
  
  OBJECTIVE
  In this review we addressed two questions: (1) How are humeral head and glenoid rim bony defects and their interactions quantified? (2) Why is the concept of the glenoid track important?
  
  
  METHODS
  We performed a systematic review of the literature using PubMed (MEDLINE) and OVID for biomechanical studies and peer-reviewed articles published until March 2013. Twenty-four studies fit the inclusion criteria. These were subdivided into four anatomic studies, four studies quantifying glenohumeral bone loss, nine studies biomechanically defining shoulder engagement, six studies analyzing current treatment models, and one clinical study to be included in the final review.
  
  
  RESULTS
  Data demonstrate pathologic engagement is dependent on the medial margin of the Hill-Sachs lesion traveling outside the glenoid track. The width of the glenoid track decreases accordingly if there is a glenoid defect, making engagement more likely. Most treatment models focus on widening the glenoid track before addressing Hill-Sachs lesions.
  
  
  CONCLUSIONS
  The glenoid track uses both glenoid and humeral head bone loss to predict subsequent risk of humeral head engagement and possible dislocation. The glenoid track shows us that restoring the track to its natural width should be among the surgeon's first priority in restoring shoulder stability. Humeral head lesions, also known as Hill-Sachs lesions, are surgically addressed when they cause clinical symptoms. Symptoms arise when the medial margin of the defect engages the glenoid track.
authors.affiliation: 3rd Marine Division, 3rd Battalion 12th Marines, FPO-AP, San Diego, CA, 96385-6100, USA, suraj.trivedi@med.navy.mil.
authors.forename: Suraj
authors.initials: S
authors.lastname: Trivedi
authors.forename: Michael L
authors.initials: ML
authors.lastname: Pomerantz
authors.forename: Daniel
authors.initials: D
authors.lastname: Gross
authors.forename: Petar
authors.initials: P
authors.lastname: Golijanan
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Provencher
mesh_terms: D001696:Biomechanical Phenomena; D016723:Bone Remodeling; D061165:Glenoid Cavity / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D006801:Humans; D058430:Humeral Head / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery; D007593:Joint Instability / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D011379:Prognosis; D011859:Radiography; D018570:Risk Assessment; D012307:Risk Factors; D012783:Shoulder Dislocation / Q000000981:diagnostic imaging / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000601:surgery; D012785:Shoulder Joint / Q000000981:diagnostic imaging / Q000473:pathology* / Q000503:physiopathology / Q000601:surgery
references.citation: J Shoulder Elbow Surg. 2007 Sep-Oct;16(5):649-56
references.pmid: 17644006
references.citation: J Shoulder Elbow Surg. 2013 Sep;22(9):1285-9
references.pmid: 23466174
references.citation: Arthroscopy. 2000 Oct;16(7):677-94
references.pmid: 11027751
references.citation: J Bone Joint Surg Am. 2010 Dec;92 Suppl 2:133-51
references.pmid: 21123597
references.citation: J Shoulder Elbow Surg. 2012 Jun;21(6):822-7
references.pmid: 22137754
references.citation: J Bone Joint Surg Am. 2010 Sep 1;92(11):2059-66
references.pmid: 20810855
references.citation: J Shoulder Elbow Surg. 2001 Jan-Feb;10(1):73-84
references.pmid: 11182740
references.citation: Am J Sports Med. 2010 Mar;38(3):594-9
references.pmid: 20194958
references.citation: J Shoulder Elbow Surg. 2010 Jul;19(5):769-80
references.pmid: 20392650
references.citation: Arthroscopy. 2002 May-Jun;18(5):488-91
references.pmid: 11987058
references.citation: Arthroscopy. 2005 Dec;21(12):1473-8
references.pmid: 16376238
references.citation: J Shoulder Elbow Surg. 2012 Sep;21(9):1142-51
references.pmid: 22036545
references.citation: Orthop Clin North Am. 1980 Apr;11(2):253-70
references.pmid: 7001307
references.citation: Am J Sports Med. 2012 Feb;40(2):388-94
references.pmid: 22053324
references.citation: J Bone Joint Surg Am. 2000 Jan;82(1):35-46
references.pmid: 10653082
references.citation: Arthroscopy. 1989;5(4):254-7
references.pmid: 2590322
references.citation: J Shoulder Elbow Surg. 1998 Jul-Aug;7(4):381-8
references.pmid: 9752648
references.citation: Am J Sports Med. 2009 May;37(5):949-54
references.pmid: 19261900
references.citation: Am J Sports Med. 2003 Jan-Feb;31(1):112-8
references.pmid: 12531767
references.citation: Am J Sports Med. 2011 Nov;39(11):2389-95
references.pmid: 21398576
references.citation: J Shoulder Elbow Surg. 2011 Dec;20(8):1328-34
references.pmid: 21493104
references.citation: J Shoulder Elbow Surg. 2004 May-Jun;13(3):286-90
references.pmid: 15111898
references.citation: J Bone Joint Surg Am. 2012 Jun 6;94(11):1003-12
references.pmid: 22637206
references.citation: J Orthop Res. 1992 Jul;10(4):524-34
references.pmid: 1613626
references.citation: Arthroscopy. 2006 Jun;22(6):609.e1
references.pmid: 16762697
references.citation: Radiology. 1994 Mar;190(3):665-8
references.pmid: 8115607
references.citation: Am J Sports Med. 2009 Dec;37(12):2459-66
references.pmid: 19726622
references.citation: Am J Sports Med. 2008 Sep;36(9):1805-12
references.pmid: 18448579
references.citation: Am J Sports Med. 2005 Jun;33(6):889-93
references.pmid: 15827355
references.citation: J Shoulder Elbow Surg. 2006 Nov-Dec;15(6):759-63
references.pmid: 16990019