Biomechanical Evaluation of Transosseous Rotator Cuff Repair: Do Anchors Really Matter?

University Hospitals Case Medical Center, Cleveland, Ohio.
The American Journal of Sports Medicine (Impact Factor: 4.36). 12/2012; 41(2). DOI: 10.1177/0363546512469092
Source: PubMed


BACKGROUND:Suture anchor fixation has become the preferred method for arthroscopic repairs of rotator cuff tears. Recently, newer arthroscopic repair techniques including transosseous-equivalent repairs with anchors or arthroscopic transosseous suture passage have been developed. PURPOSE:To compare the initial biomechanical performance including ultimate load to failure and localized cyclic elongation between transosseous-equivalent repair with anchors (TOE), traditional transosseous repair with a curved bone tunnel (TO), and an arthroscopic transosseous repair technique utilizing a simple (AT) or X-box suture configuration (ATX). STUDY DESIGN:Controlled laboratory study. METHODS:Twenty-eight human cadaveric shoulders were dissected to create an isolated supraspinatus tear and randomized into 1 of 4 repair groups (TOE, TO, AT, ATX). Tensile testing was conducted to simulate the anatomic position of the supraspinatus with the arm in 60° of abduction and involved an initial preload, cyclic loading, and pull to failure. Localized elongation during testing was measured using optical tracking. Data were statistically assessed using analysis of variance with a Tukey post hoc test for multiple comparisons. RESULTS:The TOE repair demonstrated a significantly higher mean ± SD failure load (558.4 ± 122.9 N) compared with the TO (325.3 ± 79.9 N), AT (291.7 ± 57.9 N), and ATX (388.5 ± 92.6 N) repairs (P < .05). There was also a significantly larger amount of first-cycle excursion in the AT group (8.19 ± 1.85 mm) compared with the TOE group (5.10 ± 0.89 mm). There was no significant difference between repair groups in stiffness during maximum load to failure or in normalized cyclic elongation. Failure modes were as follows: TOE, tendon (n = 4) and bone (n = 3); TO, suture (n = 6) and bone (n = 1); AT, tendon (n = 2) and bone (n = 3) and suture (n = 1); ATX, tendon (n = 7). CONCLUSION:This study demonstrates that anchorless repair techniques using transosseous sutures result in significantly lower failure loads than a repair model utilizing anchors in a TOE construct. CLINICAL RELEVANCE:Suture anchor repair appears to offer superior biomechanical properties to transosseous repairs regardless of tunnel or suture configuration.

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    ABSTRACT: The aim of this study was to test a simple technique to augment the pullout resistance of an anchor in an over-drilled sheep humerus model. Sixty-four paired sheep humeri were harvested from 32 male sheep aged 18 months. Specimens were divided into an augmented group and non-augmented group. FASTIN RC 5-mm titanium screw anchors (DePuy Mitek, Raynham, MA) double loaded with suture material (braided polyester, nonabsorbable USP No. 2) were used in both groups. Osteoporosis was simulated by over-drilling with a 4.5-mm drill. Augmentation was performed by fixing 1 of the sutures 1.5 cm inferior to the anchor insertion site with a washer screw. This was followed by a pull-to-failure test at 50 mm/min. The ultimate load (the highest value of strength before anchor pullout) was recorded. A paired t test was used to compare the biomechanical properties of the augmented and non-augmented groups. In all specimens the failure mode was pullout of the anchor. The ultimate failure loads were statistically significantly higher in the augmented group (P < .0001). The mean pullout strength was 121.1 ± 10.17 N in the non-augmented group and 176.1 ± 10.34 N in the augmented group. The described augmentation technique, which is achieved by inferior-lateral fixation of 1 of the sutures of the double-loaded anchor to a fully threaded 6.5-mm cancellous screw with a washer, significantly increases the ultimate failure loads in the over-drilled sheep humerus model. Our technique is simple, safe, and inexpensive. It can be easily used in all osteoporotic patients and will contribute to the reduction of anchor failure. This technique might be difficult to apply arthroscopically. Cannulated smaller screws would probably be more practical for arthroscopic use. Further clinical studies are needed.
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