title: Biomechanical comparison of transosseous versus suture anchor repair of the subscapularis tendon.
abstract: OBJECTIVE
  The purpose of this study was to compare the biomechanical properties of transosseous versus suture anchor repair of the subscapularis tendon. We also performed real-time measurement of contact area and pressure of the repair site under rotational loads.
  
  
  METHODS
  Six paired human cadaveric shoulders were subjected to rotational loading after repair of the subscapularis tendon. Both shoulders were randomized to transosseous or suture anchor repairs. Real-time pressure sensors were placed between the subscapularis tendon and lesser tuberosity. The repair was subjected to cyclical rotational loading and load-to-failure testing.
  
  
  RESULTS
  No significant difference was detected in initial pressurized contact area between transosseous repairs (1.70 +/- 0.99 cm(2), 57.88 +/- 30.02% footprint) and suture anchor repairs (1.08 +/- 0.58 cm(2), 34.26% +/- 17.32% footprint). Under cyclical loading, the conditioning elongation of transosseous repairs (0.64 +/- 0.40 mm) was significantly lower (P < .05) than that of suture anchor repairs (2.38 +/- 1.58 mm). No significant difference was found in mean pressurized contact area between the transosseous repairs (2.72 +/- 1.25 cm(2), 94.2% +/- 37.4% footprint) and suture anchor repairs (2.01 +/- 0.89 cm(2), 65.9% +/- 27.9% footprint). For suture anchor repairs, repair-site contact area was significantly (P < .05) smaller than the area of corresponding native insertional footprints; for transosseous repairs, no significant difference was detected. There were no significant differences in peak pressures between the 2 repairs. In the load-to-failure tensile test, there was no significant difference between transosseous repairs (453.2 +/- 66.1 N) and suture anchor repairs (392.6 +/- 78.0 N).
  
  
  CONCLUSIONS
  Transosseous and suture anchor repairs of the subscapularis tendon have comparable biomechanical properties. Despite increased conditioning elongation in suture anchor repairs, we found no significant differences in mean contact area between the 2 repairs under cyclical loading. The suture anchor repairs do have a smaller contact area than the native insertional area. Real-time pressure and contact area measurements enabled mapping of the repair site throughout cyclical loading.
  
  
  CONCLUSIONS
  Rotational loading of the subscapularis tendon may provide a more accurate representation of subscapularis tendon injuries. Both techniques showed adequate repair strength; however, neither surgical technique exhibited normal insertional behavior in this time-zero biomechanical study.
authors.affiliation: Department of Orthopaedic Surgery, University of California, San Francisco, CA 94143-0728, USA.
authors.forename: Daniel J
authors.initials: DJ
authors.lastname: Wheeler
authors.forename: Tigran
authors.initials: T
authors.lastname: Garabekyan
authors.forename: Roberto
authors.initials: R
authors.lastname: Lugo
authors.forename: Jenni M
authors.initials: JM
authors.lastname: Buckley
authors.forename: Christopher
authors.initials: C
authors.lastname: Jones
authors.forename: Marielena
authors.initials: M
authors.lastname: Lotz
authors.forename: Jeffery C
authors.initials: JC
authors.lastname: Lotz
authors.forename: C Benjamin
authors.initials: CB
authors.lastname: Ma
mesh_terms: D000368:Aged; D000369:Aged, 80 and over; D001182:Arthroscopy; D001696:Biomechanical Phenomena; D006801:Humans; D008875:Middle Aged; D012782:Shoulder / Q000601:surgery*; D053441:Suture Anchors; D013536:Suture Techniques; D013708:Tendon Injuries / Q000601:surgery*