title: Knotted versus knotless suture bridge repair of the achilles tendon insertion: a biomechanical study.
abstract: BACKGROUND
  Surgical treatment of insertional Achilles tendinopathy often involves detachment and debridement of the Achilles tendon insertion. A recent study has shown that knotted suture bridge fixation of the Achilles to the calcaneus is biomechanically superior to single-row fixation, but there is an absence of literature on the use of different suture bridge constructs to repair the Achilles tendon.
  
  
  OBJECTIVE
  There will be no significant difference in the load to failure, mode of failure, tendon strain, tendon stiffness, repair site gapping, or footprint size when comparing knotted suture bridge repair to knotless suture bridge repair of the Achilles tendon after detachment for insertional Achilles tendinopathy.
  
  
  METHODS
  Controlled laboratory study.
  
  
  METHODS
  A single specimen from each pair of 10 cadaveric Achilles tendons was randomized to 1 of 2 Achilles insertion repair groups: knotted (n = 10) or knotless (n = 10) suture bridge repair. Repaired footprint size was measured, and then cyclic testing from 10 to 100 N for 2000 cycles was performed. This was followed by measurement of tendon strain, repair site displacement, load to failure, and tendon stiffness.
  
  
  RESULTS
  The knotted suture bridge repair had a significantly higher load to failure compared with the knotless suture bridge (mean ± SD, 317.8 ± 93.6 N vs 196.1 ± 12.1 N, respectively; P = .001). All constructs failed at the tendon-suture interface. Tendon strain after cyclic testing was significantly greater in the knotless (1.20 ± 1.05) compared with the knotted (0.39 ± 0.4) suture repair groups (P = .011). There was no significant difference in footprint size between the knotted (230.3 ± 63.3 mm(2)) and knotless (248.5 ± 48.8 mm(2)) groups (P = .40). There was also no significant difference in stiffness (knotted = 76.4 ± 8.0 N/mm; knotless = 69.6 ± 10.9 N/mm; P = .17) and repair site displacement after cyclic testing (knotted = 2.8 ± 1.2 mm; knotless = 3.6 ± 1.1 mm; P = .17).
  
  
  CONCLUSIONS
  During suture bridge repair of the Achilles tendon after detachment, knots at the proximal suture anchors significantly improve the biomechanical strength of the repair.
  
  
  CONCLUSIONS
  This study demonstrated that the knotless suture bridge repair had a significantly lower load to failure than the knotted suture bridge. Surgeons should be aware of these biomechanical differences, as they influence the postoperative rehabilitation protocol and may lead to higher surgical complication rates.
authors.affiliation: Department of Orthopaedic Surgery, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA joecoxortho@gmail.com.
authors.forename: Joseph T
authors.initials: JT
authors.lastname: Cox
authors.affiliation: Department of Orthopaedic Surgery, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA.
authors.forename: Peter L
authors.initials: PL
authors.lastname: Shorten
authors.affiliation: Department of Orthopaedic Surgery, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA.
authors.forename: Gregory C
authors.initials: GC
authors.lastname: Gould
authors.affiliation: Department of Orthopaedic Surgery, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA.
authors.forename: Ronald J
authors.initials: RJ
authors.lastname: Markert
authors.affiliation: Department of Orthopaedic Surgery, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Barnett
authors.affiliation: Department of Orthopaedic Surgery, Wright State University Boonshoft School of Medicine, Dayton, Ohio, USA.
authors.forename: Richard T
authors.initials: RT
authors.lastname: Laughlin
mesh_terms: D000125:Achilles Tendon / Q000601:surgery*; D000368:Aged; D000369:Aged, 80 and over; D001696:Biomechanical Phenomena; D002102:Cadaver; D002111:Calcaneus / Q000601:surgery; D003646:Debridement; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053441:Suture Anchors; D013536:Suture Techniques; D013537:Sutures; D052256:Tendinopathy / Q000601:surgery*
keywords: insertional Achilles tendinopathy; repair; suture anchor; suture bridge