Regarding Biomechanical Advantages of Triple-loaded Suture Anchors

Abstract

We read with interest the article by Barber et al.1Barber F.A. Herbert M.A. Schroeder F.A. et al.Biomechanical advantages of triple-loaded suture anchors compared with double-row rotator cuff repairs.Arthroscopy. 2010; 26: 316-323Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar in the March 2010 issue. The authors should be commended for investigating the advantages of the triple-loaded anchor, as adding an additional suture through a given anchor allows for additional fixation without increasing the number of steps to place the implant, although the implications of additional stress from an additional suture to the given implant and repaired tendon are not fully understood to date.The concern that is raised involves the “Conclusions” and “Clinical Relevance” portions, particularly in the abstract, stating that suture-bridging techniques are more likely to stretch and fail than a single row of triple-loaded anchors. It should be highlighted that bovine shoulders were used. The geometry of a bovine tuberosity is not the same as that of a human shoulder in general. The advantage of suture-bridging repairs comes from the fact that the distal-lateral fixation is placed over the lateral edge of the human rotator cuff footprint (not on top of the footprint)—this distal position creates an obligatory compression vector over the tendon and increases the fixation over the footprint (Fig 1); the rotator cuff must overcome the distal-lateral fixation in bone that is roughly orthogonal to the cuff-loading vector.2Park M.C. ElAttrache N.S. Tibone J.E. et al.Part I: Footprint contact characteristics for an arthroscopic transosseous-equivalent rotator cuff repair technique.J Shoulder Elbow Surg. 2007; 16: 461-468Abstract Full Text Full Text PDF PubMed Scopus (302) Google Scholar, 3Park M.C. Tibone J.E. ElAttrache N.S. et al.Part II: Biomechanical assessment for a footprint-restoring arthroscopic transosseous-equivalent rotator cuff repair technique compared to a double-row technique.J Shoulder Elbow Surg. 2007; 16: 469-476Abstract Full Text Full Text PDF PubMed Scopus (305) Google Scholar On the basis of Figs 3 and 4 in the article by Barber et al.,1Barber F.A. Herbert M.A. Schroeder F.A. et al.Biomechanical advantages of triple-loaded suture anchors compared with double-row rotator cuff repairs.Arthroscopy. 2010; 26: 316-323Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar the benefit of this compression vector for load to failure, footprint contact, and gap resistance is not optimally realized because the lateral row is placed nearly in the same plane as the medial row (not orthogonal to the loading vector). It is therefore critical to consider the human geometry of the footprint-restoring repair in the context of biomechanical comparisons, and the advantages of the triple-loaded anchor may be overestimated with respect to the gist of the reported conclusions.Other considerations not mentioned include the possibility that a triple-loaded anchor may increase the stress experienced at the single anchor point—this additional load may not perform as well in the setting of humeral rotation, where there is more strain and gapping experienced anteriorly with external rotation, for example.4Ahmad 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.Am J Sports Med. 2008; 36: 888-892Crossref PubMed Scopus (60) Google Scholar, 5Gates J.J. Gilliland J. McGarry M.H. et al.The influence of distinct anatomic subregions of the supraspinatus on humeral rotation.J Orthop Res. 2010; 28: 12-17Crossref PubMed Scopus (36) Google Scholar, 6Park M.C. Jun B.J. Park C.J. et al.The biomechanical effects of dynamic external rotation on rotator cuff repair compared to testing with the humerus fixed.Am J Sports Med. 2007; 35: 1931-1939Crossref PubMed Scopus (49) Google Scholar This anterior-versus-posterior differential stress (created by rotation) may be better addressed by interconnected load-sharing suture-tendon–bridging constructs.7Park M.C. Idjadi J.A. ElAttrache N.S. et al.The effect of dynamic external rotation comparing 2 footprint-restoring rotator cuff repair techniques.Am J Sports Med. 2008; 36: 893-900Crossref PubMed Scopus (69) Google Scholar In addition, increased footprint contact from double-row techniques potentially allows suture-bridging techniques to better prevent synovial fluid extravasation into the healing zone8Ahmad C.S. Vorys G.C. Covey A. et al.Rotator cuff repair fluid extravasation characteristics are influenced by repair technique.J Shoulder Elbow Surg. 2009; 18: 976-981Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 9Park M.C. Pirolo J.M. Park C.J. et al.The effect of abduction and rotation on footprint contact for single-row, double-row, and transosseous-equivalent rotator cuff repair techniques.Am J Sports Med. 2009; 37: 1599-1608Crossref PubMed Scopus (56) Google Scholar—a single row of triple-loaded anchors may not be optimal in this context.Having stated these concerns and considerations, we recognize that not all rotator cuff tear patterns are amenable to double-row techniques; nor do we assert that all repairs should be double-row repairs. Although Barber et al.1Barber F.A. Herbert M.A. Schroeder F.A. et al.Biomechanical advantages of triple-loaded suture anchors compared with double-row rotator cuff repairs.Arthroscopy. 2010; 26: 316-323Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar seem to argue in favor of a single-row repair with triple-loaded anchors over double-row repairs given the same tear size, on the basis of the concerns and potential biomechanical advantages discussed previously, we favor a suture-bridging repair over the single-row repair described. We read with interest the article by Barber et al.1Barber F.A. Herbert M.A. Schroeder F.A. et al.Biomechanical advantages of triple-loaded suture anchors compared with double-row rotator cuff repairs.Arthroscopy. 2010; 26: 316-323Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar in the March 2010 issue. The authors should be commended for investigating the advantages of the triple-loaded anchor, as adding an additional suture through a given anchor allows for additional fixation without increasing the number of steps to place the implant, although the implications of additional stress from an additional suture to the given implant and repaired tendon are not fully understood to date. The concern that is raised involves the “Conclusions” and “Clinical Relevance” portions, particularly in the abstract, stating that suture-bridging techniques are more likely to stretch and fail than a single row of triple-loaded anchors. It should be highlighted that bovine shoulders were used. The geometry of a bovine tuberosity is not the same as that of a human shoulder in general. The advantage of suture-bridging repairs comes from the fact that the distal-lateral fixation is placed over the lateral edge of the human rotator cuff footprint (not on top of the footprint)—this distal position creates an obligatory compression vector over the tendon and increases the fixation over the footprint (Fig 1); the rotator cuff must overcome the distal-lateral fixation in bone that is roughly orthogonal to the cuff-loading vector.2Park M.C. ElAttrache N.S. Tibone J.E. et al.Part I: Footprint contact characteristics for an arthroscopic transosseous-equivalent rotator cuff repair technique.J Shoulder Elbow Surg. 2007; 16: 461-468Abstract Full Text Full Text PDF PubMed Scopus (302) Google Scholar, 3Park M.C. Tibone J.E. ElAttrache N.S. et al.Part II: Biomechanical assessment for a footprint-restoring arthroscopic transosseous-equivalent rotator cuff repair technique compared to a double-row technique.J Shoulder Elbow Surg. 2007; 16: 469-476Abstract Full Text Full Text PDF PubMed Scopus (305) Google Scholar On the basis of Figs 3 and 4 in the article by Barber et al.,1Barber F.A. Herbert M.A. Schroeder F.A. et al.Biomechanical advantages of triple-loaded suture anchors compared with double-row rotator cuff repairs.Arthroscopy. 2010; 26: 316-323Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar the benefit of this compression vector for load to failure, footprint contact, and gap resistance is not optimally realized because the lateral row is placed nearly in the same plane as the medial row (not orthogonal to the loading vector). It is therefore critical to consider the human geometry of the footprint-restoring repair in the context of biomechanical comparisons, and the advantages of the triple-loaded anchor may be overestimated with respect to the gist of the reported conclusions. Other considerations not mentioned include the possibility that a triple-loaded anchor may increase the stress experienced at the single anchor point—this additional load may not perform as well in the setting of humeral rotation, where there is more strain and gapping experienced anteriorly with external rotation, for example.4Ahmad 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.Am J Sports Med. 2008; 36: 888-892Crossref PubMed Scopus (60) Google Scholar, 5Gates J.J. Gilliland J. McGarry M.H. et al.The influence of distinct anatomic subregions of the supraspinatus on humeral rotation.J Orthop Res. 2010; 28: 12-17Crossref PubMed Scopus (36) Google Scholar, 6Park M.C. Jun B.J. Park C.J. et al.The biomechanical effects of dynamic external rotation on rotator cuff repair compared to testing with the humerus fixed.Am J Sports Med. 2007; 35: 1931-1939Crossref PubMed Scopus (49) Google Scholar This anterior-versus-posterior differential stress (created by rotation) may be better addressed by interconnected load-sharing suture-tendon–bridging constructs.7Park M.C. Idjadi J.A. ElAttrache N.S. et al.The effect of dynamic external rotation comparing 2 footprint-restoring rotator cuff repair techniques.Am J Sports Med. 2008; 36: 893-900Crossref PubMed Scopus (69) Google Scholar In addition, increased footprint contact from double-row techniques potentially allows suture-bridging techniques to better prevent synovial fluid extravasation into the healing zone8Ahmad C.S. Vorys G.C. Covey A. et al.Rotator cuff repair fluid extravasation characteristics are influenced by repair technique.J Shoulder Elbow Surg. 2009; 18: 976-981Abstract Full Text Full Text PDF PubMed Scopus (31) Google Scholar, 9Park M.C. Pirolo J.M. Park C.J. et al.The effect of abduction and rotation on footprint contact for single-row, double-row, and transosseous-equivalent rotator cuff repair techniques.Am J Sports Med. 2009; 37: 1599-1608Crossref PubMed Scopus (56) Google Scholar—a single row of triple-loaded anchors may not be optimal in this context. Having stated these concerns and considerations, we recognize that not all rotator cuff tear patterns are amenable to double-row techniques; nor do we assert that all repairs should be double-row repairs. Although Barber et al.1Barber F.A. Herbert M.A. Schroeder F.A. et al.Biomechanical advantages of triple-loaded suture anchors compared with double-row rotator cuff repairs.Arthroscopy. 2010; 26: 316-323Abstract Full Text Full Text PDF PubMed Scopus (62) Google Scholar seem to argue in favor of a single-row repair with triple-loaded anchors over double-row repairs given the same tear size, on the basis of the concerns and potential biomechanical advantages discussed previously, we favor a suture-bridging repair over the single-row repair described. Biomechanical Advantages of Triple-Loaded Suture Anchors Compared With Double-Row Rotator Cuff RepairsArthroscopyVol. 26Issue 3PreviewTo evaluate the strength and suture-tendon interface security of various suture anchors triply and doubly loaded with ultrahigh–molecular weight polyethylene–containing sutures and to evaluate the relative effectiveness of placing these anchors in a single-row or double-row arrangement by cyclic loading and then destructive testing. Full-Text PDF Author's ReplyArthroscopyVol. 26Issue 7PreviewWe would like to thank Drs. Park, Ahmad, ElAttrache, and Lee for their interest and discussion of our article.1 They are correct to reiterate a point we raised in the study limitations paragraph of our discussion that this study was performed in bovine specimens. Also important is that the bovine infraspinatus tendon was used as a model and not the supraspinatus. The morphology and relation between that tendon and its humeral attachment are clearly not the same as those found for the supraspinatus and the greater tuberosity or in a human specimen. Full-Text PDF