Open Sub-pectoral Biceps Tenodesis: A Biomechanics Comparison Of Interference Screw And Various Fixation Techniques

OBJECTIVES: The purpose of this study was to biomechanically compare six techniques for biceps tenodesis to evaluate the potential difference of anchor size, type and configuration (single- versus double-loaded). The six techniques were interference screws (IS), endobutton (EB), double-loaded 2.9mm PEEK anchor (DL-2.9), double-loaded 1.9mm all-suture anchor (DL-1.9), single-loaded 1.7mm all-suture anchor (SL-1.7), and soft tissue tenodesis (ST) (Smith and Nephew, Memphis, TN, USA). METHODS: 42 fresh-frozen cadaver shoulders (mean age, 72 years [range 54 to 89 years; SD, 9.8 years]; 71% male specimens) were dissected leaving the proximal humerus, proximal biceps tendon, and pectorals major insertion. Specimens were randomized 1 to 6 groups and a sub-pectoral biceps tenodesis was performed. The specimens underwent load to failure axial traction on a materials testing machine. RESULTS: The mean failure loads with the 95%Cl are as follows: IS (78.6N, 58.1-99.1 N), ST (100.3 N, 77.7-122.9 N), DL-1.9 (120.6 N, 101.3-139.8 N), EB (136.7 N, 104.5-168.9 N), DL-2.9 (141.0 N, 111.3-170.7 N), and SL-1.7 (142.0 N, 107.9-176.1 N). Failure occurred at the tendon in almost all specimens, however 5 specimens sustained anchor failure during mechanical loading (IS, n=2; DL-2.9, n=1; DL-1.9, n=1; SL-1.7, n=1). CONCLUSION: The load to failure testing of the interference screw group demonstrated statistically significant lower results than the endobutton and anchor techniques. The endobutton and anchor techniques were not significantly different. The endobutton, double-loaded 2.9mm PEEK anchor, and single-loaded 1.7mm all-suture anchor attained the largest ultimate failure loads at approximately 140 N. These results may be taken into consideration when the orthopedic surgeon selects the appropriate fixation technique.