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Limited Biomechanical Evidence Behind Single Row Versus Double Row Repair of Subscapularis Tears: A Systematic Review

Open AccessPublished:March 15, 2022DOI:https://doi.org/10.1016/j.asmr.2022.01.009

      Purpose

      To systematically review the literature for studies investigating the biomechanical properties of constructs used to repair isolated subscapularis tears in time zero human cadaveric studies.

      Methods

      A systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines. Three electronic databases were searched for studies that reported on the construct technique and biomechanical outcomes for the repair of isolated subscapularis tears in human cadaveric specimens. Ultimate load, gap formation, stiffness, and failure mode were documented. Methodological quality was assessed using the Quality Appraisal for Cadaveric Studies (QUACS) scale.

      Results

      Six articles qualified (104 shoulders [72 single-row, 26 double-row, 6 transosseous]; mean QUACS score 10.5 ± 1) and were analyzed. Studies varied in the number and type of anchors and construct technique (1-2 anchors single-row; 3-4 anchors double-row; bioabsorbable or titanium anchors) and suture(s) used (no. 2 FiberWire or FiberTape), subscapularis tear type (25%, 33%, 50%, or 100% tear), and whether a knotless or knotted fixation was used. In studies that created full-thickness, upper subscapularis tears (Fox-Romeo II/III or Lafosse II), no significant differences were seen in ultimate load, gap formation, and stiffness for knotted versus knotless single-row repair (2 studies) and single-row versus double-row repair (1 study). Double-row repair of complete subscapularis tears demonstrated higher ultimate load, stiffness, and lower gap formation in 1 study. Ultimate load differed between the studies and constructs (single-row: range, 244 N to 678 N; double-row: range 332 N to 508 N, transosseous: 453 N). Suture cutout was the most common mode of failure (59%).

      Conclusion

      Because of the limited number of studies and varying study designs in examining the biomechanical properties of repair constructs used for subscapularis tears, there is inconclusive evidence to determine which construct type is superior for repairing subscapularis tears.

      Clinical Relevance

      Results from biomechanical studies of clinically relevant subscapularis repair constructs are important to guide decision-making for choosing the optimal construct for patients with subscapularis tears.
      The subscapularis is the largest and most powerful rotator cuff muscle. It primarily functions as an internal rotator of the humerus but also plays an important role in balancing glenohumeral joint forces and in maintaining anterior shoulder stability.
      • Denard P.J.
      • Ladermann A.
      • Burkhart S.S.
      Arthroscopic management of subscapularis tears.
      • Keating J.F.
      • Waterworth P.
      • Shaw-Dunn J.
      • Crossan J.
      The relative strengths of the rotator cuff muscles. A cadaver study.
      • Kuntz A.F.
      • Raphael I.
      • Dougherty M.P.
      • Abboud J.A.
      Arthroscopic subscapularis repair.
      Historically, the prevalence of subscapularis tears was thought to be low and reported in less than 5% of rotator cuff tears.
      • Warner J.J.P.
      • Higgins L.
      • Parsons I.M.
      • Dowdy P.
      Diagnosis and treatment of anterosuperior rotator cuff tears.
      However, with the progression of shoulder arthroscopy techniques and advanced imaging, it is now estimated that 19% to 59% of rotator cuff tears also have combined subscapularis involvement.
      • Denard P.J.
      • Ladermann A.
      • Burkhart S.S.
      Arthroscopic management of subscapularis tears.
      ,
      • Bennett W.F.
      Arthroscopic repair of isolated subscapularis tears: A prospective cohort with 2- to 4-year follow-up.
      • Garavaglia G.
      • Ufenast H.
      • Taverna E.
      The frequency of subscapularis tears in arthroscopic rotator cuff repairs: A retrospective study comparing magnetic resonance imaging and arthroscopic findings.
      • Kim T.K.
      • Rauh P.B.
      • McFarland E.G.
      Partial tears of the subscapularis tendon found during arthroscopic procedures on the shoulder: A statistical analysis of sixty cases.
      • Lafosse L.
      • Jost B.
      • Reiland Y.
      • Audebert S.
      • Toussaint B.
      • Gobezie R.
      Structural integrity and clinical outcomes after arthroscopic repair of isolated subscapularis tears.
      • Barth J.R.
      • Burkhart S.S.
      • De Beer J.F.
      The bear-hug test: a new and sensitive test for diagnosing a subscapularis tear.
      Isolated subscapularis tears remain rare, accounting for around 5% of all rotator cuff repairs.
      • Bennett W.F.
      Arthroscopic repair of isolated subscapularis tears: A prospective cohort with 2- to 4-year follow-up.
      ,
      • Lafosse L.
      • Jost B.
      • Reiland Y.
      • Audebert S.
      • Toussaint B.
      • Gobezie R.
      Structural integrity and clinical outcomes after arthroscopic repair of isolated subscapularis tears.
      ,
      • Nové-Josserand L.
      • Hardy M.B.
      • Leandro Nunes Ogassawara R.
      • Carrillon Y.
      • Godenèche A.
      Clinical and structural results of arthroscopic repair of isolated subscapularis tear.
      These isolated tears are typically the result of a traumatic injury and occur more commonly in younger patients.
      • Kuntz A.F.
      • Raphael I.
      • Dougherty M.P.
      • Abboud J.A.
      Arthroscopic subscapularis repair.
      ,
      • Deutsch A.
      • Altchek D.W.
      • Veltri D.M.
      • Potter H.G.
      • Warren R.F.
      Traumatic tears of the subscapularis tendon. Clinical diagnosis, magnetic resonance imaging findings, and operative treatment.
      ,
      • Gerber C.
      • Hersche O.
      • Farron A.
      Isolated rupture of the subscapularis tendon: Results of operative repair.
      Adequate fixation of subscapularis tears is important for restoring normal joint function.
      • Lee T.Q.
      Editorial Commentary: Precise Repair of Partial Subscapularis Tendon Tears Is Essential.
      Open repair of the subscapularis was once considered the gold standard,
      • Bartl C.
      • Scheibel M.
      • Magosch P.
      • Lichtenberg S.
      • Habermeyer P.
      Open repair of isolated traumatic subscapularis tendon tears.
      but arthroscopic, single- or double-row, suture anchor constructs have become increasingly used.
      • Ahmad C.S.
      • Kleweno C.
      • Jacir A.M.
      • et al.
      Biomechanical performance of rotator cuff repairs with humeral rotation: A new rotator cuff repair failure model.
      • Barber F.A.
      • Drew O.R.
      A biomechanical comparison of tendon-bone interface motion and cyclic loading between single-row, triple-loaded cuff repairs and double-row, suture-tape cuff repairs using biocomposite anchors.
      • Burkhart S.S.
      • Denard P.J.
      • Konicek J.
      • Hanypsiak B.T.
      Biomechanical validation of load-sharing rip-stop fixation for the repair of tissue-deficient rotator cuff tears.
      • Domb B.G.
      • Glousman R.E.
      • Brooks A.
      • Hansen M.
      • Lee T.Q.
      • ElAttrache N.S.
      High-tension double-row footprint repair compared with reduced-tension single-row repair for massive rotator cuff tears.
      • Ma C.B.
      • Comerford L.
      • Wilson J.
      • Puttlitz C.M.
      Biomechanical evaluation of arthroscopic rotator cuff repairs: double-row compared with single-row fixation.
      • Smith C.D.
      • Alexander S.
      • Hill A.M.
      • et al.
      A biomechanical comparison of single and double-row fixation in arthroscopic rotator cuff repair.
      Clinical studies have demonstrated that arthroscopic single- and double-row repair of subscapularis tears results in significant improvements in clinical outcomes.
      • Xiao M.
      • Cohen S.A.
      • Cheung E.V.
      • Abrams G.D.
      • Freehill M.T.
      Arthroscopic single and double row repair of isolated and combined subscapularis tears result in similar improvements in outcomes: A systematic review.
      Numerous biomechanical studies have compared the strength of single-row and double-row repairs for supraspinatus and infraspinatus tears,
      • Ahmad C.S.
      • Kleweno C.
      • Jacir A.M.
      • et al.
      Biomechanical performance of rotator cuff repairs with humeral rotation: A new rotator cuff repair failure model.
      • Barber F.A.
      • Drew O.R.
      A biomechanical comparison of tendon-bone interface motion and cyclic loading between single-row, triple-loaded cuff repairs and double-row, suture-tape cuff repairs using biocomposite anchors.
      • Burkhart S.S.
      • Denard P.J.
      • Konicek J.
      • Hanypsiak B.T.
      Biomechanical validation of load-sharing rip-stop fixation for the repair of tissue-deficient rotator cuff tears.
      • Domb B.G.
      • Glousman R.E.
      • Brooks A.
      • Hansen M.
      • Lee T.Q.
      • ElAttrache N.S.
      High-tension double-row footprint repair compared with reduced-tension single-row repair for massive rotator cuff tears.
      • Ma C.B.
      • Comerford L.
      • Wilson J.
      • Puttlitz C.M.
      Biomechanical evaluation of arthroscopic rotator cuff repairs: double-row compared with single-row fixation.
      • Smith C.D.
      • Alexander S.
      • Hill A.M.
      • et al.
      A biomechanical comparison of single and double-row fixation in arthroscopic rotator cuff repair.
      ,
      • Tashjian R.Z.
      • Hoy R.W.
      • Helgerson J.R.
      • Guss A.D.
      • Henninger H.B.
      • Burks R.T.
      Biomechanical comparison of transosseous knotless rotator cuff repair versus transosseous equivalent repair: Half the anchors with equivalent biomechanics?.
      and a systematic review concluded that double-row constructs restored more of the anatomic footprint and had stronger biomechanical properties compared to single-row repairs for posterosuperior rotator cuff tears.
      • Wall L.B.
      • Keener J.D.
      • Brophy R.H.
      Double-row vs single-row rotator cuff repair: A review of the biomechanical evidence.
      However, the anatomical and functional differences between the subscapularis and the posterosuperior rotator cuff necessitate biomechanical studies pertaining directly to the subscapularis to determine the strongest repair construct.
      • Halder A.
      • Zobitz M.E.
      • Schultz E.
      • An K.N.
      Structural properties of the subscapularis tendon.
      Given that there is limited tendon-to-bone healing in the early postoperative window, the initial success of the repair depends largely on the strength of the construct and its ability to transfer load from tendon to bone.
      • Smith C.D.
      • Alexander S.
      • Hill A.M.
      • et al.
      A biomechanical comparison of single and double-row fixation in arthroscopic rotator cuff repair.
      Thus results from biomechanical studies of clinically relevant subscapularis repair constructs are important to guide decision-making for choosing the optimal construct for patients with subscapularis tears. The purpose of this study was to systematically review the literature for studies investigating the biomechanical properties of constructs used to repair isolated subscapularis tears in time zero human cadaveric studies.

      Methods

      Literature Review and Search Strategy

      This systematic review was performed using Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines.
      • Moher D.
      • Liberati A.
      • Tetzlaff J.
      • Altman D.G.
      Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement.
      Two authors conducted separate searches of the following medical databases: PubMed, SCOPUS, and Cochrane Central Register of Controlled Trials. The searches were performed on December 22, 2021, and confirmed by the senior author (M.T.F.). The search string used was as follows: subscap∗[All Fields] AND (construct[tw] OR strength[tw] OR fixation[tw] OR repair[tw] OR tear[tw] OR reconstruct∗[tw] OR fail∗[tw]) AND (biomech∗[tw] OR cadav∗). Articles published from inception to December 22, 2021 were included for screening.

      Eligibility Criteria

      Eligible studies consisted of biomechanical studies published in the English language that reported on the construct technique and biomechanical outcomes for the repair of simulated isolated subscapularis tears in human cadaveric specimen. Exclusion criteria were (1) review articles, animal studies, clinical studies, book chapters, technique articles, and case reports; (2) studies pertaining to subscapularis repair during shoulder arthroplasty; and (3) studies examining tendon transfers. In the event of different studies with duplicate (or overlapping) subject populations, the study with the greatest number of subjects or greatest clarity of methods and results was included if the subjects could not be separated. After removal of duplicates, titles or abstracts were screened, and full text articles were further assessed based on inclusion and exclusion criteria by 2 independent reviewers (M.X., S.A.C.). The search results were reviewed for duplicates and the inclusion criteria to determine the articles that were included in the final analysis (Fig 1).
      Figure thumbnail gr1
      Fig 1Flow diagram summarizing the literature search, screening, and review.

      Data Extraction

      Articles were reviewed and data were extracted from the included studies by the 2 independent reviewers using the methodology recommended by Harris et al.
      • Harris J.D.
      • Quatman C.E.
      • Manring M.M.
      • Siston R.A.
      • Flanigan D.C.
      How to write a systematic review.
      All study, specimen, and biomechanical parameters were collected. Parameters analyzed included year of publication, number of specimens, number of shoulders, mean age, subscapularis tear size, construct type, cyclic loading protocol, ultimate load, gap formation, stiffness, failure mode, and repair footprint contact area. Extracted data were cross-checked for accuracy by the two reviewers and recorded onto a shared spreadsheet.

      Quality Assessment

      The risk of study bias and methodological quality was assessed using the Quality Appraisal for Cadaveric Studies (QUACS) scale, a 13-item checklist that assesses the design, conduct, and report of cadaveric dissection studies for inclusion into systematic reviews.
      • Wilke J.
      • Krause F.
      • Niederer D.
      • et al.
      Appraising the methodological quality of cadaveric studies: Validation of the QUACS scale.
      Scores are reported as poor (<20%), fair (>20% and <40%), moderate (>40% and <60%), substantial (>60% and <80%), or excellent (>80%).

      Statistical Analysis

      Due to the heterogeneity between studies, pooling of data and meta-analysis was not performed. Thus, a qualitative synthesis with descriptive summaries of the studies is presented.

      Results

      Characteristics of Included Studies

      The initial search yielded 1188 articles. After removing duplicates, 916 records were screened for eligibility. Of these, 12 articles underwent full text review, resulting in six articles that were included and analyzed (Fig 1).
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      According to the QUACS, three studies were excellent (>11/13),
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      ,

      Borbas P, Cammarata S, Loucas R, et al. Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability [published online November 25, 2021]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-021-06808-0.

      ,
      • Sgroi M.
      • Kappe T.
      • Ludwig M.
      • et al.
      Are knotted or knotless techniques better for reconstruction of full-thickness tears of the superior portion of the subscapularis tendon? A study in cadavers.
      and 3 studies were of substantial (9/13 or 10/13) quality.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      ,
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      The number of specimens per study ranged from 6 to 18 for a total of 63 specimens and 104 shoulders included in this review. The mean age of the cadaveric specimens ranged from 62.4 to 78 years. The average native subscapularis footprint area was reported in three studies,
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      ,
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      ,

      Borbas P, Cammarata S, Loucas R, et al. Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability [published online November 25, 2021]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-021-06808-0.

      and it ranged from 295 mm2 to 631.5 mm2 (Table 1).
      Table 1Characteristics of Included Studies
      StudyJournalQUACSNumber of SpecimensNumber of ShouldersSpecimen Age, (y), Mean ± SD (Range)Native Footprint Size (mm2), Mean ± SD (Range)
      Borbas 2021KSSTA11181878 ± 8631.5 ± 131.2
      Dyrna 2019Arthroscopy11153062.4 (58-74)486.9 ± 59.7
      Lorbach 2016KSSTA9612NSNS
      Sgroi 2021CORR1281669 (61-75)NS
      Wellmann 2009KSSTA10101665.4 ± 13NS
      Wheeler 2010Arthroscopy1061268 ± 12295 (237-365)
      QUACS, Quality Appraisal for Cadaveric Studies; SD, standard deviation; KSSTA, Knee Surgery, Sports Traumatology, Arthroscopy; CORR, Clinical Orthopaedics and Related Research; NS, not specified.

      Subscapularis Repair Constructs

      Three studies
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      ,
      • Sgroi M.
      • Kappe T.
      • Ludwig M.
      • et al.
      Are knotted or knotless techniques better for reconstruction of full-thickness tears of the superior portion of the subscapularis tendon? A study in cadavers.
      ,
      • Lorbach O.
      • Trennheuser C.
      • Kieb M.
      • Efe T.
      • Kohn D.
      • Anagnostakos K.
      Reconstruction of 25 and 50 % subscapularis tears: a single anchor with a double-mattress suture is sufficient for the reconstruction.
      used the Fox-Romeo
      • Fox J.A.
      • Noerdlinger M.A.
      • Romeo A.A.
      Arthroscopic subscapularis repair.
      classification system to recreate type II (complete tear of the upper 25%) and III (complete tear of the upper 50%) tears of the subscapularis, 1 study

      Borbas P, Cammarata S, Loucas R, et al. Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability [published online November 25, 2021]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-021-06808-0.

      used the Lafosse classification
      • Lafosse L.
      • Jost B.
      • Reiland Y.
      • Audebert S.
      • Toussaint B.
      • Gobezie R.
      Structural integrity and clinical outcomes after arthroscopic repair of isolated subscapularis tears.
      to recreate type II tears (complete tear of the upper 1/3), and 2 studies created complete full-thickness tears
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      ,
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      (Table 2). Of the included studies, two
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      ,
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      compared single-row and double-row repair, one
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      compared single-row to transosseous repair, and 3 studies

      Borbas P, Cammarata S, Loucas R, et al. Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability [published online November 25, 2021]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-021-06808-0.

      • Sgroi M.
      • Kappe T.
      • Ludwig M.
      • et al.
      Are knotted or knotless techniques better for reconstruction of full-thickness tears of the superior portion of the subscapularis tendon? A study in cadavers.
      • Lorbach O.
      • Trennheuser C.
      • Kieb M.
      • Efe T.
      • Kohn D.
      • Anagnostakos K.
      Reconstruction of 25 and 50 % subscapularis tears: a single anchor with a double-mattress suture is sufficient for the reconstruction.
      used only single-row suture anchor constructs. Two studies compared knotted and knotless single-row repairs.

      Borbas P, Cammarata S, Loucas R, et al. Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability [published online November 25, 2021]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-021-06808-0.

      ,
      • Sgroi M.
      • Kappe T.
      • Ludwig M.
      • et al.
      Are knotted or knotless techniques better for reconstruction of full-thickness tears of the superior portion of the subscapularis tendon? A study in cadavers.
      The 4 studies
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      ,

      Borbas P, Cammarata S, Loucas R, et al. Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability [published online November 25, 2021]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-021-06808-0.

      • Sgroi M.
      • Kappe T.
      • Ludwig M.
      • et al.
      Are knotted or knotless techniques better for reconstruction of full-thickness tears of the superior portion of the subscapularis tendon? A study in cadavers.
      • Lorbach O.
      • Trennheuser C.
      • Kieb M.
      • Efe T.
      • Kohn D.
      • Anagnostakos K.
      Reconstruction of 25 and 50 % subscapularis tears: a single anchor with a double-mattress suture is sufficient for the reconstruction.
      published most recently used bioabsorbable suture anchors, whereas titanium suture anchors were used in the other 2 studies (Table 2).
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      ,
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      Table 2Summary of Subscapularis Repair Construct Types in the Included Studies
      StudyTear TypeRepairSR StitchSR AnchorsDR/TO StitchDR AnchorsSuture
      Borbas 2021Lafosse IISR
      • 1.
        Knotted Lasso-loop mattress
      • 2.
        Knotted horizontal Mattress
      • 3.
        Knotless FiberTape
      DL 5.5 mm PEEK or 4.75 mm Swivelock (1 anchor)N/AN/ANS or FiberTape
      Dyrna 2019Fox-Romeo II and IIISR vs HDR vs DRSimple mattressDL 4.5 mm Bio-Corkscrew (2 anchors)Medial: knotless; Lateral: knotlessSL medial and DL lateral 4.75-mm absorbable SwiveLock (3 anchors)SR: No. 2 FiberWire; DR: FiberTape
      Lorbach 2016Fox-Romeo II and IIISRDouble mattressDL 5.5 mm Bio-Corkscrew (1 anchor)N/AN/ANo. 2 FiberWire
      Sgroi 2021Fox-Romeo IIISR
      • 1.
        Knotted (Modified MA)
      • 2.
        Knotless FiberTape
      5.5 mm Bio-Corkscrew or 5.5 mm Swivelock (1 anchor)N/AN/ANo. 2 FiberWire or FiberTape
      Wellmann 2009Full-Thickness Complete TearSR vs DRModified MADL 5.5 mm titanium Corkscrew (2 anchors)Medial: horizontal mattress; Lateral: knotlessMedial: SL 5.0-mm titanium Corkscrew (2 anchors); Lateral: DL 4.5-mm Bio-PushLock (2 anchors)No. 2 FiberWire
      Wheeler 2010Full-Thickness Complete TearSR vs TOHorizontal mattressDL 5.0 mm titanium Corkscrew (2 anchors)Modified MA3 bone tunnelsNo. 2 FiberWire
      SR, single row; DR, double row; TO, transosseous; HDR, hybrid double row; DL, double-loaded; SL, single-loaded; MA, Mason Allen; N/A, not applicable.
      Double-row repairs used three
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      or four
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      suture anchors. The double-row, knotless construct in the study by Dyrna et al.
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      placed 1 lateral row suture anchor out of the native subscapularis footprint in a superolateral position close to the entrance of the bicipital groove. Wellman et al.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      repaired the subscapularis tendon using a double row suture-bridge technique, with a modified Mason-Allen stitch used to tie the medial row. The authors positioned the 2 lateral row anchors just medial to the bicipital groove and the 2 medial row anchors 10 to 12 mm medially to the lateral row anchors. Wheeler et al.
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      used an open transosseous construct for subscapularis repair with 3 bone tunnels made at the lesser tuberosity. Three modified Mason-Allen stitches were used to secure the subscapularis repair (Table 2).

      Biomechanical Properties

      All 6 studies recorded ultimate load and mode of failure. The load to failure protocol for the studies was either 0.5 mm/s or 1 mm/s. The mean ultimate load for single-row constructs ranged from 244 N to 678 N. No significant differences in ultimate load were seen in the 2 studies comparing knotted and knotless single-row constructs.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      ,
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      The mean ultimate loads for the 2 studies with double-row constructs were 332 N and 508 N,
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      ,
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      and the ultimate load for transosseous repair was 453 N. One study
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      found that double-row repair resulted in a significantly higher ultimate load compared to single-row repair of complete subscapularis tears, whereas another study
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      did not find a significant difference in ultimate failure load between single-row and double-row constructs of full-thickness partial subscapularis tears. Lorbach et al.
      • Lorbach O.
      • Trennheuser C.
      • Kieb M.
      • Efe T.
      • Kohn D.
      • Anagnostakos K.
      Reconstruction of 25 and 50 % subscapularis tears: a single anchor with a double-mattress suture is sufficient for the reconstruction.
      reported no significant difference in ultimate failure load between Fox-Romeo type II and III tears repaired with a single-row construct. Overall, suture cutout through the tendon was the most common mode of failure (59%; Table 3).
      Table 3Summary of Biomechanical Results of the Included Studies
      StudyCyclic LoadingGap Formation (mm)Ultimate Load (N)Footprint Contact Area (%)Stiffness (N/mm)Failure ModeFailure Loading
      Borbas 2021Preload 10N; 10-100 N for 300 cycles at 2 mm/sSR lasso: 1.3 ± 0.5

      SR mattress: 1.3 ± 0.5

      SR tape: 1.1 ± 0.9
      SR lasso: 630.8 ± 145.3

      SR mattress: 586.9 ± 220.7

      SR tape: 678.2 ± 236.5
      SR lasso: 65.4 ± 10.2

      SR mattress: 66.8 ± 9

      SR tape: 62.3 ± 9.7
      SR lasso: 88 ± 30.3

      SR mattress: 65 ± 27

      SR tape: 83.9 ± 32.9
      Suture cutout (8/18); proximal humerus fracture (5/18); MT junction (4/18); lesser tuberosity avulsion (1/18)0.5 mm/s
      Dyrna 2019Preload 10 N; 10-100 N for 300 cycles at 0.5 HzSR Type II: 1.4 ± 0.5

      HDR Type II: 1.3 ± 0.5

      SR Type III: 1.8 ± 0.6

      HDR Type III: 1.4 ± 0.5

      DR Type III:1.5 ± 0.5
      SR Type II: 531 ± 129

      HDR Type II: 451 ± 132

      SR Type III: 451 ± 124

      HDR Type III: 548 ± 228

      DR Type III: 508 ± 170
      SR Type II: 88.4 ± 8.9

      HDR Type II: 95.1 ± 7.9

      SR Type III: 73.6 ± 10.9

      HDR Type III: 84.4 ± 9.4

      DR Type III: 84.1 ± 12.3
      SR Type II: 36.5 ± 8.7

      HDR Type II: 36.4 ± 6.9

      SR Type III: 36.2 ± 5.5

      HDR Type III: 48.3 ± 11.5

      DR Type III: 42.3 ± 12.1
      Suture cutout (16/30), Anchor pullout (7/30), lesser tuberosity fracture (4/30), medial tendon failure (3/30)0.5 mm/s
      Lorbach 2016Preload 10 N; 10-60 N for 50 cycles Stepwise increase to 100 N and 180 N for 50 cyclesAt 100 N:

      SR Type II: 5.1 mm

      SR Type III: 4.3 mm
      SR Type II: 486 ± 167

      SR Type III: 455 ± 213
      NSNSSR Type II: Anchor pullout or bone fracture (6/6)

      SR Type III: Anchor pullout (2/6), Suture cutout (4/6)
      NS
      Sgroi 2021Preload 10N; 10-60 N for 50 cycles Stepwise increase to 100 N and 180 N for 50 cycles at 1 HzNo differences between groupsSR knotted: 521.1 ± 266.2

      SR knotless: 475.8 ± 183.3
      NSAt 10-100 N:

      SR knotted: 45.0 ± 4.8

      SR knotless: 45.2 ± 6
      SR knotted: anchor pullout (2/8); suture cutout (6/8)

      SR knotless: anchor pullout (2/8); suture cutout (3/8); suture slipped out of eyelet (3/8)
      1 mm/s
      Wellmann 20095-100 N for 100 cyclesSR: 1.7 ± 0.5

      DR: 1.2 ± 0.3
      Statistically significant difference between groups.
      SR: 244 ± 40N

      DR: 332 ± 39N
      Statistically significant difference between groups.
      NSSR: 55 ± 8

      DR: 81 ± 12
      Statistically significant difference between groups.
      SR: Suture cutout (7/8); lesser tuberosity fracture (1/8)

      DR: Suture cutout (8/8)
      1 mm/s
      Wheeler 2010Preload 60 N; 76-183 N for 50 cycles at 0.1 HzSR: 2.38 ± 1.6

      TO: 0.64 ± 0.4
      Statistically significant difference between groups.
      SR: 392.6 ± 78

      TO: 453.2 ± 66
      SR: 65.9 ± 27.9

      TO: 94.2 ± 37.4
      NRSR: suture cutout (3/6), anchor pullout (3/6); TO: suture cutout (6/6)0.5 mm/s
      SR, single row; DR, double row; TO, transosseous; MT, musculotendinous; NS, not specified; N, Newtons; Hz, Hertz.
      Statistically significant difference between groups.
      The number of cycles of loading ranged from 50 to 300 (Table 3). All articles used a force controlled cyclic loading protocol to assess gap formation. There were no significant differences in gap formation in studies comparing knotted and knotless single-row constructs. Two studies
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      ,
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      found that double-row or transosseous constructs resulted in significantly less gap formation compared to single-row repair of complete subscapularis tears, whereas one study
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      found no difference between constructs in gap formation after repair of Fox-Romeo type II and III tears. Wellmann et al.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      reported that the double-row technique resulted in a stiffer construct compared to single-row repair, although Dyrna et al.
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      found no significant difference in stiffness and pressurized contact area between single- and double-row repairs. Wheeler et al.
      • Wheeler D.J.
      • Garabekyan T.
      • Lugo R.
      • et al.
      Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
      reported no significant differences in contact area between single-row and transosseous repair (Table 3).

      Discussion

      The present systematic review included 6 studies that investigated the biomechanical properties of repair constructs used for isolated subscapularis tears in cadaveric specimens. Despite the variation in the number of anchors, anchor type, suture type, and tear pattern between the studies, all 6 articles investigated single-row repair constructs. Other repair types that were studied included double-row and transosseous repair. Although tendon healing is affected by a variety of parameters such as patient demographics, tear characterization, biological factors, and tissue quality, biomechanical properties of the repair construct are strong predictors of successful repair.
      • Bunker D.L.
      • Ilie V.
      • Ilie V.
      • Nicklin S.
      Tendon to bone healing and its implications for surgery.
      • Killian M.L.
      • Cavinatto L.
      • Shah S.A.
      • et al.
      The effects of chronic unloading and gap formation on tendon-to-bone healing in a rat model of massive rotator cuff tears.
      • Rossi L.A.
      • Rodeo S.A.
      • Chahla J.
      • Ranalletta M.
      Current concepts in rotator cuff repair techniques: Biomechanical, functional, and structural outcomes.
      These biomechanical properties include low gap formation, high ultimate load, large footprint contact area, and higher stiffness, which are especially important during the initial phase of postoperative period, when biological healing results in a structurally and mechanically weakened tendon-to-bone interface.
      • Rossi L.A.
      • Rodeo S.A.
      • Chahla J.
      • Ranalletta M.
      Current concepts in rotator cuff repair techniques: Biomechanical, functional, and structural outcomes.
      • Nho S.J.
      • Yadav H.
      • Pensak M.
      • Dodson C.C.
      • Good C.R.
      • Macgillivray J.D.
      Biomechanical fixation in arthroscopic rotator cuff repair.
      In studies that created full-thickness, upper subscapularis tears (Fox-Romeo II/III or Lafosse II), no significant differences were seen in ultimate load, gap formation, and stiffness for knotted compared to knotless single-row repair. In studies that compared single-row to double-row repair for subscapularis tears, similar biomechanical properties were reported for single-row and double-row repair of Fox-Romeo II/III tears, but a higher ultimate load, lower gap formation, and higher stiffness was found for double-row repair of complete subscapularis tears.
      Single-row repair in the current review used either 1 or 2 double-loaded suture anchors and were knotless or tied with variations of mattress or modified Mason-Allen stitches. Sgroi et al.
      • Sgroi M.
      • Kappe T.
      • Ludwig M.
      • et al.
      Are knotted or knotless techniques better for reconstruction of full-thickness tears of the superior portion of the subscapularis tendon? A study in cadavers.
      compared knotted and knotless single-row repair for Fox-Romeo III subscapularis tears and found no significant differences in biomechanical properties for both constructs. Likewise, Borbas et al.

      Borbas P, Cammarata S, Loucas R, et al. Arthroscopic single anchor repair techniques for upper third subscapularis tears provide sufficient biomechanical stability [published online November 25, 2021]. Knee Surg Sports Traumatol Arthrosc. doi:10.1007/s00167-021-06808-0.

      compared 3 different single-row constructs (knotted lasso-loop mattress, knotted mattress, and knotless suture tape) for Lafosse II subscapularis tears and found that the constructs resulted in similar ultimate load, gap formation, and stiffness. The authors did report a significantly higher pressurized footprint coverage for the knotted lasso-loop mattress and knotless construct compared to the knotted mattress repair. Overall, single row repair accounted for the most common construct investigated in biomechanical studies of subscapularis repair, which is in line with findings that the majority of clinical studies use single row constructs as well.
      • Xiao M.
      • Cohen S.A.
      • Cheung E.V.
      • Abrams G.D.
      • Freehill M.T.
      Arthroscopic single and double row repair of isolated and combined subscapularis tears result in similar improvements in outcomes: A systematic review.
      There were 2 studies that directly compared single-row to double-row suture anchor repair, although the double-row constructs varied between studies. Dyrna et al.
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      focused their repair toward the “leading-edge” by placing a lateral-row anchor superolaterally outside of the native footprint. Wellmann et al.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      used a suture bridge construct, which is designed to maximize the pressurized contact area while preserving tendon vascularity.
      • Rossi L.A.
      • Rodeo S.A.
      • Chahla J.
      • Ranalletta M.
      Current concepts in rotator cuff repair techniques: Biomechanical, functional, and structural outcomes.
      These studies also conflicted with regards to whether there was a biomechanical difference between the two construct types. Although Dyrna et al.
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      found no difference in load to failure between single- and double-row repairs, Wellmann et al.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      reported significantly higher ultimate load and stiffness for double-row constructs. These variations in results are likely due to the differences in study design, because the study by Dyrna and colleagues
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      was conducted more recently, included only Fox-Romeo II and III tears, and repaired tears using absorbable suture anchors and a knotless double-row configuration with FiberTape. On the other hand, Wellmann et al.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      repaired complete subscapularis tears with titanium suture anchors, and their double-row construct used a tied medial row. From these studies, tear size may play an important role in choosing a repair construct. For smaller tears, no biomechanical differences may be seen between single-and double-row repair, but for larger, complete tears, double-row constructs may be more biomechanically favorable. These findings are similar to those in clinical practice, as clinical studies on subscapularis repair tended to use double-row constructs for larger, Lafosse III and IV tears, and single-row constructs for smaller subscapularis tears.
      • Xiao M.
      • Cohen S.A.
      • Cheung E.V.
      • Abrams G.D.
      • Freehill M.T.
      Arthroscopic single and double row repair of isolated and combined subscapularis tears result in similar improvements in outcomes: A systematic review.
      Prior systematic reviews of biomechanical evidence for rotator cuff constructs have focused on the posterosuperior rotator cuff, concluding that double-row constructs are biomechanically stronger to single-row fixation.
      • Wall L.B.
      • Keener J.D.
      • Brophy R.H.
      Double-row vs single-row rotator cuff repair: A review of the biomechanical evidence.
      ,
      • Shi B.Y.
      • Diaz M.
      • Binkley M.
      • McFarland E.G.
      • Srikumaran U.
      Biomechanical strength of rotator cuff repairs: A systematic review and meta-regression analysis of cadaveric studies.
      Shi et al.
      • Shi B.Y.
      • Diaz M.
      • Binkley M.
      • McFarland E.G.
      • Srikumaran U.
      Biomechanical strength of rotator cuff repairs: A systematic review and meta-regression analysis of cadaveric studies.
      performed a meta-regression of 40 posterosuperior rotator cuff biomechanical studies and found that the repair material such as number of sutures, suture limbs passed through the tendon, and mattress stitches are stronger predictors of rotator cuff repair strength than the type of construct. Clinically, Chen et al.
      • Chen M.
      • Xu W.
      • Dong Q.
      • Huang Q.
      • Xie Z.
      • Mao Y.
      Outcomes of single-row versus double-row arthroscopic rotator cuff repair: A systematic review and meta-analysis of current evidence.
      found that after meta-analysis, double-row repairs resulted in improved tendon healing compared to single-row fixation for patients with larger posterosuperior rotator cuff tears (>3 cm), but the authors did not find clinically significant differences in patient-reported outcomes. Many of the arthroscopic constructs currently used for subscapularis repair are derived from repair techniques used for supraspinatus tears. Yet the subscapularis has the largest anatomic footprint out of all rotator cuff tendons and differs in stiffness and strength,
      • Curtis A.S.
      • Burbank K.M.
      • Tierney J.J.
      • Scheller A.D.
      • Curran A.R.
      The insertional footprint of the rotator cuff: An anatomic study.
      • D'Addesi L.L.
      • Anbari A.
      • Reish M.W.
      • Brahmabhatt S.
      • Kelly J.D.
      The subscapularis footprint: An anatomic study of the subscapularis tendon insertion.
      • Richards D.P.
      • Burkhart S.S.
      • Tehrany A.M.
      • Wirth M.A.
      The subscapularis footprint: An anatomic description of its insertion site.
      necessitating separate biomechanical and clinical studies. Despite the importance of the subscapularis, there is a relative paucity of studies in the literature in comparison to that of posterior superior tears.
      • Kuntz A.F.
      • Raphael I.
      • Dougherty M.P.
      • Abboud J.A.
      Arthroscopic subscapularis repair.
      ,
      • Lo I.K.Y.
      • Burkhart S.S.
      Subscapularis tears: Arthroscopic repair of the forgotten rotator cuff tendon.
      The small number of studies found in the current investigation mirror the finding that fewer clinical studies targeting subscapularis repair exist as compared to studies of the posterosuperior rotator cuff.
      • Xiao M.
      • Cohen S.A.
      • Cheung E.V.
      • Abrams G.D.
      • Freehill M.T.
      Arthroscopic single and double row repair of isolated and combined subscapularis tears result in similar improvements in outcomes: A systematic review.
      ,
      • Saltzman B.M.
      • Collins M.J.
      • Leroux T.
      • et al.
      Arthroscopic repair of isolated subscapularis tears: A systematic review of technique-specific outcomes.
      Isolated tears make up about 10% to 25%
      • Lafosse L.
      • Jost B.
      • Reiland Y.
      • Audebert S.
      • Toussaint B.
      • Gobezie R.
      Structural integrity and clinical outcomes after arthroscopic repair of isolated subscapularis tears.
      ,
      • Yoon J.S.
      • Kim S.J.
      • Choi Y.R.
      • Kim S.H.
      • Chun Y.M.
      Arthroscopic repair of the isolated subscapularis full-thickness tear: Single- versus double-row suture-bridge technique.
      of all subscapularis lesions (5% of all rotator cuff repairs)
      • Bennett W.F.
      Arthroscopic repair of isolated subscapularis tears: A prospective cohort with 2- to 4-year follow-up.
      ,
      • Lafosse L.
      • Jost B.
      • Reiland Y.
      • Audebert S.
      • Toussaint B.
      • Gobezie R.
      Structural integrity and clinical outcomes after arthroscopic repair of isolated subscapularis tears.
      ,
      • Nové-Josserand L.
      • Hardy M.B.
      • Leandro Nunes Ogassawara R.
      • Carrillon Y.
      • Godenèche A.
      Clinical and structural results of arthroscopic repair of isolated subscapularis tear.
      and are usually associated with a traumatic event, although subscapularis tears occur more often in combination with other rotator cuff tears. The rate of isolated subscapularis re-tear has been reported to range from 5% to 17%.
      • Lafosse L.
      • Jost B.
      • Reiland Y.
      • Audebert S.
      • Toussaint B.
      • Gobezie R.
      Structural integrity and clinical outcomes after arthroscopic repair of isolated subscapularis tears.
      ,
      • Yoon J.S.
      • Kim S.J.
      • Choi Y.R.
      • Kim S.H.
      • Chun Y.M.
      Arthroscopic repair of the isolated subscapularis full-thickness tear: Single- versus double-row suture-bridge technique.
      • Bartl C.
      • Salzmann G.M.
      • Seppel G.
      • et al.
      Subscapularis function and structural integrity after arthroscopic repair of isolated subscapularis tears.
      • Heikenfeld R.
      • Gigis I.
      • Chytas A.
      • Listringhaus R.
      • Godolias G.
      Arthroscopic reconstruction of isolated subscapularis tears: clinical results and structural integrity after 24 months.
      • Meshram P.
      • Rhee S.M.
      • Park J.H.
      • Oh J.H.
      Comparison of functional and radiological outcomes of tears involving the subscapularis: Isolated subscapularis versus combined anterosuperior rotator cuff tears.
      • Seppel G.
      • Plath J.E.
      • Völk C.
      • et al.
      Long-term results after arthroscopic repair of isolated subscapularis tears.
      Yoon et al.
      • Yoon J.S.
      • Kim S.J.
      • Choi Y.R.
      • Kim S.H.
      • Chun Y.M.
      Arthroscopic repair of the isolated subscapularis full-thickness tear: Single- versus double-row suture-bridge technique.
      compared arthroscopic single- versus double-row suture bridge repair for isolated subscapularis tears and found no differences in outcomes or re-tear rates. In this review, the most common failure mode for all repair types was suture cutout through the tendon, although differences in failure mode between construct types could not be determined. Additionally, the increased cost, operating room time, and technical difficulty of double-row compared to single-row repair may influence construct choice. In cases of smaller tears that require less fixation strength, single-row constructs may be adequate.

      Limitations

      This analysis has several limitations. The study design resulted in analysis of relatively few studies. The studies included in this review varied with respect to subscapularis tear size, anchor placement, and testing parameters. Given the varying parameters, head-to-head comparisons of knotted and knotless constructs or single- and double-row constructs yielded few studies, which may affect final conclusions. Because of the study heterogeneity, pooling of results could not be performed. The double-row constructs included in this review were either all-knotless
      • Dyrna F.
      • Beitzel K.
      • Pauzenberger L.
      • et al.
      A superolaterally placed anchor for subscapularis “leading-edge” refixation: A biomechanical study.
      or tied medial row.
      • Wellmann M.
      • Wiebringhaus P.
      • Lodde I.
      • et al.
      Biomechanical evaluation of a single-row versus double-row repair for complete subscapularis tears.
      As such, no support for or against the tying of the medial row can be determined. Additionally, 1 study investigating transosseous repair was included in this review, although this repair construct is less frequently used. All studies included in this review were cadaveric studies that only assessed time zero biomechanical properties. Thus healing responses, tissue quality, and forces applied are different than in vivo.
      • LeClere L.
      CORR Insights(R): Are knotted or knotless techniques better for reconstruction of full-thickness tears of the superior portion of the subscapularis tendon? A study in dadavers.
      Few studies included in this review were homogenous and compared similar groups. Thus conclusions with regard to whether single-row versus double-row repair of subscapularis tears is biomechanically favorable cannot be determined. Finally, the loading protocols and construct materials such as suture and anchor type differed among all studies, supporting the possibility that the biomechanical differences detected in this study may be due to differences in study design.

      Conclusions

      Because of the limited number of studies and varying study designs in examining the biomechanical properties of repair constructs used for subscapularis tears, there is inconclusive evidence to determine which construct type is superior for repairing subscapularis tears.

      Supplementary Data

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