title: Effect of interference screw depth on fixation strength in biceps tenodesis.
abstract: OBJECTIVE
  The purpose of this study was to assess the biomechanical performance of the long head of the biceps tenodesis with an interference screw with respect to screw depth.
  
  
  METHODS
  Twenty-one human cadaveric shoulders were randomized into 3 treatment groups (7 each): interference screw placed flush to the humeral cortex, 50% proud, or fully recessed. Bone density was determined, and subpectoral biceps tenodesis was performed with 8 × 12 mm Bio-Tenodesis screws (Arthrex, Naples, FL). Each construct was cyclically loaded from 5 to 70 N for 500 cycles at 1 Hz and then pulled to failure at 1 mm/s. Relative actuator displacement was calculated from cyclic testing. Maximum load, elongation, linear stiffness, and failure mode were recorded from pull-to-failure testing. Because of numerous failures during cyclic testing, the final load data from the fully recessed group were not statistically analyzed. The remaining groups were compared by use of a 2-tailed, Student unpaired t test and χ(2) analysis.
  
  
  RESULTS
  There was no significant difference in displacement among groups during cyclic testing. Five specimens in the recessed group failed during cyclic testing, whereas 2 specimens and 0 specimens failed in the proud and flush groups, respectively. The maximum loads sustained were 281.6 ± 77.8 N, 184.5 ± 56.3 N, and 209.1 ± 57.0 N for the flush group, 50% proud group, and recessed group (in those specimens surviving cyclical loading), respectively.
  
  
  CONCLUSIONS
  Placement of a Bio-Tenodesis screw flush to the humeral cortex is preferred for maximum fixation strength in subpectoral biceps tenodesis. A screw placed to 50% depth may be effective in the laboratory setting, but recessed placement is more variable and requires additional fixation. The fully recessed group resulted in 5 of 7 failures during cyclical loading, with no specimens failing in the flush group.
  
  
  CONCLUSIONS
  This study shows the importance of determining the optimal depth of interference screw placement during biceps tenodesis to obtain optimal biomechanical performance and reduce the risk of fixation failure.
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Salata
authors.affiliation: Department of Orthopaedic Surgery, Naval Medical Center, San Diego, California, U.S.A.
authors.forename: James R
authors.initials: JR
authors.lastname: Bailey
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Bell
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Rachel M
authors.initials: RM
authors.lastname: Frank
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Kevin C
authors.initials: KC
authors.lastname: McGill
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Emery C
authors.initials: EC
authors.lastname: Lin
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: James S
authors.initials: JS
authors.lastname: Kercher
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Vincent M
authors.initials: VM
authors.lastname: Wang
authors.affiliation: Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts, U.S.A.
authors.forename: Matthew T
authors.initials: MT
authors.lastname: Provencher
authors.affiliation: Department of Orthopaedic Surgery, University of Connecticut Health Center, Farmington, Connecticut, U.S.A.
authors.forename: Augustus D
authors.initials: AD
authors.lastname: Mazzocca
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.. Electronic address: nverma@rushortho.com.
authors.forename: Nikhil N
authors.initials: NN
authors.lastname: Verma
authors.affiliation: Department of Orthopaedic Surgery, Rush University Medical Center, Chicago, Illinois, U.S.A.
authors.forename: Anthony A
authors.initials: AA
authors.lastname: Romeo
mesh_terms: D000368:Aged; D001696:Biomechanical Phenomena; D015519:Bone Density; D001863:Bone Screws; D002102:Cadaver; D006801:Humans; D006811:Humerus / Q000503:physiopathology / Q000601:surgery*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000503:physiopathology; D012782:Shoulder / Q000503:physiopathology*; D013710:Tendons / Q000503:physiopathology / Q000601:surgery*; D053656:Tenodesis / Q000295:instrumentation* / Q000379:methods; D016474:Weight-Bearing