Knot Strength Varies Widely Among Expert Arthroscopists

Am J Sports Med. 2014 Aug;42(8):1978-84. doi: 10.1177/0363546514535554. Epub 2014 Jun 12.


Background: While most surgeons can tie visually appealing knots under an arthroscope, few surgeons have undergone an objective evaluation of their ability to consistently tie knots with maximum loop and knot security.

Purpose/hypotheses: The purpose of this study was to evaluate and compare variations in ultimate load to failure, 3-mm displacement (clinical failure), and knot stack height of arthroscopic suture knots tied by 73 independent expert orthopaedic arthroscopists. The hypotheses were (1) that skilled arthroscopic surgeons would be able to routinely tie arthroscopic knots of similar strength, (2) that surgeons with <10 years of clinical practice would tie stronger and more consistent knots, and (3) that surgeons who performed >200 arthroscopic shoulder cases per year would produce stronger and more consistent knots than would surgeons who performed fewer cases.

Study design: Controlled laboratory study.

Methods: Each surgeon tied 5 of the same type of their preferred arthroscopic knot and half-hitch locking mechanism. Each knot was mechanically tested for ultimate load to failure and clinical failure.

Results: For the 365 individual knots tested, the mean ultimate load across each knot was 231 N (range, 29-360 N). The mean clinical failure load was 139 N (range, 16-328 N). The average knot stack height among the 365 knots was 5.61 mm (range, 2.89-10.32 mm). For an individual surgeon, the standard deviations of the 5 consecutive knots tied ranged from 6 to 133 N. The ultimate load and clinical failure load for surgeons with <10 years of practice (n = 39) were 248 ± 93 N and 142 ± 56 N, respectively. The mean ± SD ultimate and clinical failure loads for surgeons with >10 years of practice (n = 34) were 211 ± 111 N and 136 ± 69 N, respectively. When knot strength was used to measure performance, significant differences existed in ultimate load (P = .001); however, there were no differences in clinical failure load (P = .329). Surgeons with <10 years of practice were able to tie knots more consistently than were surgeons in practice for >10 years, for both ultimate load (P = .018) and clinical failure load (P = .005). There was no significant difference based on number of cases performed with respect to ultimate load or clinical failure load (P = .292 and .479, respectively). There was no difference in consistency, as both groups had similar standard deviations (P = .814 for ultimate load, P = .545 for clinical failure).

Conclusion: Considerable variations in knot strength exist between arthroscopic knots tied by surgeons. Study findings revealed that surgeons were unable to tie 5 consecutive knots of the same type consistently; that for both ultimate load and clinical failure load, surgeons with <10 years in practice were able to tie knots more consistently than surgeons with >10 years; and that surgeons performing >200 arthroscopic shoulder cases annually failed to tie stronger or more consistent knots than their counterparts performing fewer cases.

Clinical relevance: This variation in knot tying has the potential to affect the integrity of arthroscopic repairs. Independent objective testing of the ability to tie secure knots as part of a surgeons' training may be necessary.

Keywords: arthroscopic knot tying; knot security; knot stack height; knot strength.

MeSH terms

  • Arthroscopy / methods*
  • Clinical Competence*
  • Humans
  • Materials Testing
  • Suture Techniques*
  • Sutures*
  • Tensile Strength