Arthroscopy: The Journal of Arthroscopic & Related Surgery
Original ArticleBiomechanical Study: Determining the Optimum Insertion Angle for Screw-In Suture Anchors—Is Deadman's Angle Correct?
Section snippets
Methods
To provide a uniform material, we decided to perform the biomechanical tests using solid rigid polyurethane foam blocks (Sawbones, Limhamn, Sweden). This is a recognized alternative test medium that has similar properties to cancellous bone. The density of the material used was 10 lb/cu ft. We used 5.5-mm Twinfix screw-in anchors (Smith & Nephew, Andover, MA) according to the manufacturer's guidelines. The suture material was replaced with No. 5 FiberWire (Arthrex, Naples, FL) to ensure that
Results
All constructs were loaded to failure. In every experiment the metal anchor pulled out of the synthetic bone block. There was a statistically significant difference in failure load among all constructs (P < .0001, repeated-measures ANOVA test). The mean pullout strengths for all constructs are shown in Table 1. An angle of insertion of 90° and applied load of 90° produced the strongest construct, failing at a mean of 306 N (standard deviation [SD], 9 N). The strongest pullout strengths for each
Discussion
We have shown that with a contemporary screw-in anchor, the ultimate pullout strength is greatest when it is inserted at the same angle as or similar angle to the angle of applied load. Do these findings have a clinical impact? Rotator cuff repairs with suture anchors can fail at 3 interfaces: the anchor can pull out of the bone, the eyelet or suture material can break, and the suture can cut out through tendon. It is likely that all 3 are linked. The focus of research has moved among these
Conclusions
The angle of applied load to a suture anchor and the insertion angle significantly influence the biomechanical pullout strength of screw-in suture anchors. The insertion angle of the suture anchor should replicate the angle of applied load to ensure the optimum pullout strength.
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Perianchor cyst formation in all-suture anchor after rotator cuff repair: an evaluation of anchor insertion angle
2022, Journal of Shoulder and Elbow SurgeryCitation Excerpt :Burkhart1 suggested in the Deadman theory that minimizing the insertion angle results in stronger fixation. However, many subsequent studies have refuted this theory.9,26 Moreover, unlike screw-type anchors, all-suture anchors are deployed under the cortex for fixation.
Rotator cuff repair techniques: Current concepts
2021, Journal of Clinical Orthopaedics and TraumaCitation Excerpt :This ‘deadman angle’ describes both the angle at which the anchor is inserted and the angle that the suture makes with the direction of pull of the rotator cuff. Traditionally, an angle less than 45° has been advocated, but recent evidence suggests that a more vertical entry point corresponding to the angle of applied load more reliably optimises pullout strength.27–30 Suture anchors constitute a strong and stable form of fixation between the torn rotator cuff and its bony footprint.
Anatomic considerations for arthroscopic glenoid reconstruction using iliac crest grafts: a radiologic study
2019, Journal of Shoulder and Elbow SurgeryCitation Excerpt :In daily clinical use, angulation of up to 30° is easy to accomplish; in some arthroscopic procedures, far higher degrees of angulation are accepted. Especially anchors used for arthroscopic Bankart repair maintain good mechanical stability when inserted in steep angles, whereas screws for fixation of bone grafts to the glenoid should be applied perpendicularly to achieve good compression.8,19 Resch et al16 examined the average distance from the coracoid process to the intersection of the musculocutaneous nerve with the medial margin of the coracobrachial muscle and found it was more than 5 cm, leading to the conclusion that this nerve is seldom at risk when establishing an anterior portal for Bankart repair.
Pullout Strength of All-Suture Anchors: Effect of the Insertion and Traction Angle—A Biomechanical Study
2018, Arthroscopy - Journal of Arthroscopic and Related SurgeryCitation Excerpt :Since the deadman theory proposed that the ideal insertion angle of suture anchors was 45° to the bone surface, most surgeons believe that inserting suture anchors at this angle will result in the strongest pullout strength. However, several recent studies did not demonstrate the strongest ultimate load to failure for CSA inserted at 45°.10,12,13,30 Itoi et al.30 compared the pullout strength of 3 different insertion angles (45°, 90°, and 135°) in both finite element analysis and biomechanical study with a synthetic bone analog model.
Effect of anchor threads on the pullout strength: A biomechanical study
2018, Journal of OrthopaedicsCitation Excerpt :After the introduction of this theory, many researchers and surgeons use 45° as a standard angle of anchor insertion.6,8–10,12,13 However, biomechanical studies using cadavers and synthetic bones revealed that the pullout strength of the anchor inserted at 90° to the bone surface was greater than that of the anchor inserted at 45°.14–16 The greatest difference between the commonly-accepted intuitional understanding of tent peg insertion and the outcome of these biomechanical studies is the friction between the bone (ground) and the anchor (peg).
Minimum Distance of Suture Anchors Used for Rotator Cuff Repair Without Decreasing the Pullout Strength: A Biomechanical Study
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The authors report that they have no conflicts of interest in the authorship and publication of this article.