Journal of Functional Morphology and Kinesiology Article Floating Subscapularis Tear: A Variation of the Partial Subscapularis Tear Kotaro Yamakado Department of Orthopaedics/Sposrts medicine, Fukui General Hospital, Fukui 9108561, Japan; [email protected] Received: 25 December 2019; Accepted: 3 February 2020; Published: 5 February 2020 Abstract: A variation of subscapularis tear has been identified, named floating subscapularis, where the tendon is completely detached from the lesser tuberosity but is continuous with the tissue covering the bicipital groove. An accurate diagnosis can be made using arthroscopic observation with passive external and internal rotation of the affected shoulder, which shows mismatched movement between the humerus and the subscapularis tendon. The purpose of this study is to examine the prevalence of this particular tear pattern. Clinical records during the study period (from January 2011 to December 2017) were retrospectively examined. Overall, 1295 arthroscopic rotator cuff repair procedures were performed. Among these, the subscapularis tendon was repaired in 448 cases, and 27 cases were diagnosed as floating subscapularis. The prevalence of floating subscapularis was 6% in the subscapularis repair population. This particular tear pattern has not previously been described and it seems to be ignored. The floating subscapularis is thought to be the tear of the deep layer preserving the superficial layer connected to the greater tuberosity by fibrous extension of the soft tissue covering the bicipital groove. Keywords: arthroscopy; partial thickness rotator cuff tear; subscapularis tear; variation 1. Introduction The ball-and-socket structure of the shoulder joint allows a greater range of motion than other joints. The rotator cuff muscles hold the joint for stability and rotate the humerus for mobility. Rotator cuff muscles consist of four muscles: the supraspinatus, infraspinatus, teres minor, and subscapularis. The subscapularis, an internal rotator of the shoulder, arises from the subscapularis fossa of the scapula and inserts into the humerus. The superior two-third part (the tendinous part of the subscapularis) inserts into the lesser tuberosity and the inferior one-third part (the muscular part of the subscapularis) inserts directly into the humerus below the lesser tuberosity by a thin membranous structure [1–3]. Tears of the subscapularis tendon are less common than those of the posterosuperior rotator cuff muscles (supraspinatus and infraspinatus). The prevalence of subscapularis tendon tears had been largely underestimated before arthroscopic examination became popular in the 2000s. Currently, the diagnosis of full-thickness subscapularis tear is routinely made arthroscopically and with reliable accuracy, with reporting tear-rate up to 29% [4–6]. In most cases of a full-thickness subscapular tear, the torn tendon retracts medially and inferiorly; however, as the superior glenohumeral ligament and coracohumeral ligament are attached to the subscapularis, it assumes a comma shape (so-called “comma sign”), which is thought to be pathognomonic of a subscapularis tear (Figure1)[7]. Classification of rotator cuff tears can be made according to the tear morphology: acute or traumatic/degenerative, partial or complete, retracted or not retracted, combined or isolated. For subscapularis tears, various classifications have been proposed. But the Lafosse classification [8] is widely accepted. The Lafosse classification provides five grades of tear: (I) Partial lesion of superior third of the subscapularis without tendon retraction; (II) complete tear of the superior one-third; (III) J. Funct. Morphol. Kinesiol. 2020, 5, 11; doi:10.3390/jfmk5010011 www.mdpi.com/journal/jfmk J. Funct. Morphol. Kinesiol. 2020, 5, 11 2 of 6 complete tear of superior two-third; (IV) complete tear of subscapularis with tendon retraction and a concentricJ. Funct. Morphol. glenohumeral Kinesiol. 2019, 4 joint;, x FOR PEER (V) completeREVIEW tear of subscapularis with tendon retraction2 of 6 and an eccentric glenohumeralJ. Funct. Morphol. Kinesiol. joint. 2019 Garavaglia, 4, x FOR PEER et REVIEW al. [9 ] subdivided grade I, distinguishing minor2 of fraying6 of the insertionconcentric site glenohumeral (grade IA) joint; and partial(V) complete tears oftear the of deepsubscapularis layer (grade with tendon IB). retraction and an eccentric glenohumeral joint. Garavaglia et al. [9] subdivided grade I, distinguishing minor fraying A variationconcentric of subscapularis glenohumeral joint; tear (V) was complete identified tear andof subscapularis named as “floatingwith tendon subscapularis,” retraction and an where the of the insertioneccentric siteglenohumeral (grade IA) joint. and Garapartialvaglia tears et of al. the [9] deepsubdivided layer (grade grade I,IB). distinguishing minor fraying tendon is completely detached from the lesser tuberosity but is continuous with the tissue covering the A ofvariation the insertion of subscapularis site (grade IA) tear and was part identifiedial tears of and the deepnamed layer as (grade“floating IB). subscapularis,” where bicipitalthe groovetendon Ais (Figures variation completely2 of and subscapularis detached3). An accuratefrom tear wasthe diagnosislesseidentifiedr tuberosity and can named be but made as is “floating continuous using subscapularis,” arthroscopic with the tissue where observation with passivecoveringthe external the tendon bicipital andis completely groove internal (Figures detached rotation 2 and from of 3). the An the a accurateff lesseectedr tuberosity shoulderdiagnosis but can (Figure isbe continuous made4), whichusing with arthroscopic shows the tissue mismatched movementobservationcovering between with the thepassive bicipital humerus external groove and(Figures and theinternal 2 and subscapularis 3).rota Antion accurate of the tendon. diagnosis affected Thecan shoulder be purpose made (Figure using of arthroscopic this4), which study was to shows observationmismatched with movement passive betweenexternal andthe humerusinternal rota andtion the of subscapularis the affected shoulder tendon. (FigureThe purpose 4), which of examine the prevalence of this particular tear pattern. this studyshows was mismatched to examine movement the prevalen betweence of thisthe humerusparticular and tear the pattern. subscapularis tendon. The purpose of this study was to examine the prevalence of this particular tear pattern. FigureFigure 1. Subscapularis Figure1. Subscapularis 1. Subscapularis tear intear the intear rt. the shoulder.in rt.the shoulder. rt. Asshoulder. the As superior theAs thesuperior glenosuperior humeralgleno gleno humeral humeral ligament ligament ligament and coracohumeral and and coracohumeralcoracohumeral ligament ligament are attached are attached to the to subscapularis,the subscapularis, it assumes it assumes a commaa comma shape shape (so-called (so-called ligament are attached to the subscapularis, it assumes a comma shape (so-called “comma sign”), which is “comma“comma sign”), sign”),which whichis thought is thought to be pathognomonicto be pathognomonic of a subscapularisof a subscapularis tear. tear. SC: SC: subscapularis, subscapularis, HH: HH: thoughthumeral to behumeral head. pathognomonic head. of a subscapularis tear. SC: subscapularis, HH: humeral head. (B) (A) (B) (A) (C) Figure 2. Schematic drawing(C) of normal, torn, and floating subscapularis. (A) Intact subscapularis. SC, subscapularis; arrow, transverse humeral ligament; *, long head of the biceps tendon. (B) Torn subscapularis. The tendon is detached from the lesser tuberosity and is retracted medially. In many cases, long head of the biceps is subluxated. (C) Floating subscapularis. Subscapularis tendon is detached from the lesser tuberosity with soft tissue extension to the transverse humeral ligament is preserved. SC, subscapularis; arrow, transverse humeral ligament; *, long head of the biceps tendon. J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 3 of 6 Figure 2. Schematic drawing of normal, torn, and floating subscapularis. (A) Intact subscapularis. SC, J. Funct. Morphol. Kinesiol. 2019, 4, x FOR PEER REVIEW 3 of 6 subscapularis; arrow, transverse humeral ligament; *, long head of the biceps tendon. (B) Torn subscapularis.Figure 2. Schematic The tendon drawing is detached of normal, from torn, the and less floatinger tuberosity subscapularis. and (isA )retracted Intact subscapularis. medially. InSC, many cases,subscapularis; long head ofarrow, the bicepstransverse is subluxated.humeral ligament; (C) Floating *, long subscapularis.head of the biceps Subscapularis tendon. (B) tendonTorn is detachedsubscapularis. from the The lesser tendon tuberosity is detached with from soft the tissue lesser extension tuberosity to and th eis transverse retracted medially. humeral In ligament many is preserved.cases, longSC, subscapularis;head of the biceps arrow, is subluxated. transverse (humeC) Floatingral ligament; subscapularis. *, long Subscapularis head of the bicepstendon tendon. is J. Funct. Morphol. Kinesiol. 2020, 5, 11 3 of 6 detached from the lesser tuberosity with soft tissue extension to the transverse humeral ligament is preserved. SC, subscapularis; arrow, transverse humeral ligament; *, long head of the biceps tendon. (A()A ) (B)( B) FigureFigureFigure 3.3. Floating 3. Floating subscapularis.subscapularis. subscapularis. (A (A)) Rt.)Rt. Rt. shoulder shoulder viewing from fromfrom the thethe po posteriorposteriorsterior portal. portal.portal. Subscapularis SubscapularisSubscapularis