A comparison of lateral ankle ligament suture anchor strength

Absorbable suture anchor and knotless anchor techniques produced similar outcomes in arthroscopic anterior talofibular ligament repair

PURPOSE

The purpose of this study is to compare absorbable suture anchor with knotless anchor techniques for arthroscopic anterior talofibular ligament (ATFL) repair.

METHOD

A multicenter retrospective study was performed with 185 patients, who had undergone an arthroscopic ATFL repair procedure using absorbable suture anchor or knotless anchor between May 2017 and October 2019. The follow-up time was a minimum of 18 months. Karlsson-Peterson score, visual analogue scale (VAS), and Cumberland ankle instability tool (CAIT) were evaluated. The complications were also recorded.

RESULTS

One hundred and seven patients underwent one absorbable suture anchor repair procedure (Group A [A]), and the other seventy-eight patients underwent one knotless anchor repair procedure (Group B [B]). At the final follow-up, both Karlsson-Peterson score (A, pre 61.0 ± 8.0 vs post 93.5 ± 5.3, P < 0.001; B, pre 59.5 ± 8.2 vs post 92.4 ± 6.3, P < 0.001), VAS score (A, pre 5.0 ± 1.3 vs post 0.5 ± 0.7, P < 0.001; B, pre 5.5 ± 1.2 vs post 0.9 ± 1.0, P < 0.001), and CAIT score (A, pre 53.1 ± 12.0 vs post 93.1 ± 6.6, P < 0.001; B, pre 51.6 ± 12.0 vs post 93.1 ± 6.5, P < 0.001) improved significantly in both groups. There was no significant difference between the two groups regarding the Karlsson-Peterson score (A, pre 61.0 ± 8.0 vs B, pre 59.5 ± 8.2, n.s; A, post 93.5 ± 5.3 vs B, post 92.4 ± 6.3, n.s), CAIT score (A, pre 53.1 ± 12.0 vs B, pre 51.6 ± 12.0, n.s; A, post 93.1 ± 6.6 vs B, post 93.1 ± 6.5, n.s) and the change ranges of VAS (A, 4.5 ± 1.0 vs B, 4.6 ± 1.2, n.s). Anchor complications were easier to occur in Group B (0/107 vs 6/78, P = 0.007). Knot irritation slightly increased in Group A (10/107 vs 0/78, P = 0.006). No significant difference was found regarding total complication rates (A, 10/107 vs B, 6/78, n.s).

CONCLUSION

Absorbable suture anchor and knotless anchor for arthroscopic ATFL repair produced similar clinical outcomes. The ankle stability scores increased significantly in both groups. However, the knotless anchor has a higher risk to loosen, deviated direction or break, while the absorbable suture anchor still has a slim chance of knot irritation.

LEVEL OF EVIDENCE

III.

When deadman theory meets footprint decortication: a suture anchor biomechanical study

Background

The optimal insertion angle for suture anchor insertion has long been of great interest. Although greater tuberosity decortication is commonly performed during rotator cuff repair, the effect of decortication on the suture anchor insertion angle remains unclear. The purpose of this study was to compare the pullout strength of threaded suture anchors inserted at 45° and 90° in decorticated and non-decorticated synthetic bone models.

Methods

Two kinds of synthetic bones were used to simulate the decorticated and non-decorticated conditions, for which 40 metallic suture anchors were used. Anchors were inserted at 45° and 90° in both decorticated and non-decorticated models and tested under cyclic loading followed by load-to-failure testing. The number of completed cycles, ultimate failure load, and failure modes was recorded.

Results

In the decorticated model, the ultimate failure load of anchors inserted at 45° (67.5 ± 5.3 N) was significantly lower than that of anchors inserted at 90° (114.1 ± 9.8 N) (p <  0.001). In the non-decorticated model, the ultimate failure load of anchors inserted at 45° (591.8 ± 58 N) was also significantly lower than that of anchors inserted at 90° (724.9 ± 94 N) (p = 0.003). Due to the diverse failure modes in the non-decorticated model, specimens with a failure mode of suture anchor pullout were analyzed in greater detail, with results showing a significantly larger pullout strength for anchors inserted at 90° (781.6 ± 53 N) than anchors inserted at 45° (648.0 ± 43 N) (p = 0.025).

Conclusion

Regardless of decortication, the pullout strength of anchors inserted at 90° was greater than those inserted at 45°. The clinical relevance is that inserting suture anchors at 90° is recommended due to the significantly larger ultimate failure load in both decorticated and non-decorticated bones.

Knotless Anchors in Acetabular Labral Repair: A Biomechanical Comparison

PURPOSE

To analyze the failure mechanism, stiffness, and pullout strength of acetabular knotless suture anchors.

METHODS

Seven suture anchors were tested in high-density (0.48 g/cc) synthetic blocks. The anchors were implanted perpendicular to the bone block. The anchor's suture(s) were tied around a loop of 8 high-strength nonabsorbable sutures and pulled in line with the anchor at a rate of 1 mm/s until failure. The following knotless anchors were tested: Stryker Knotilus 3.5, Arthrex Pushlock 2.9, Linvatec PopLok 2.8, Linvatec PopLok 3.3, ArthroCare SpeedLock HIP (3.4-mm), and Smith & Nephew Bioraptor Knotless 2.9. The standard knot tying Smith & Nephew Bioraptor 2.9 mm served as a baseline for comparison.

RESULTS

Stiffness was highest in the Pushlock, the SpeedLock HIP, and Knotilus. At 1 mm displacement, the SpeedLock HIP exhibited significantly higher load than all other anchors, excluding the Pushlock and PopLok 3.3 (P ≤ .012 for all comparisons). Excluding the SpeedLock HIP and Knotilus, the Pushlock displayed significantly higher load than all other anchors at 2-mm displacement (P ≤ .015 for all comparisons). Maximum load was the highest for the Knotilus and Bioraptor knotted anchor (P < .001 compared with all other anchors).

CONCLUSIONS

All knotless suture anchors used in hip arthroscopy, except for the Knotilus 3.5, failed by suture pullout from the anchor. The 2 anchors with the highest maximum load, the Knotilus 3.5 and knotted Bioraptor 2.9, failed by suture failure; however, these anchors displayed the lowest stiffness and load at 1 mm displacement among all anchors tested. Stiffness and loads at clinically relevant displacements, not maximum load alone, may be most important in predicting anchor clinical performance during the early phases of labral healing.

CLINICAL RELEVANCE

Knotless suture anchors tend to fail by suture pullout from the anchor, yet the stiffness of these constructs suggests that minimal displacement of the repair will occur under physiologic loads.

Fixation Strength of Polyetheretherketone Sheath-and-Bullet Device for Soft Tissue Repair in the Foot and Ankle

Tendon transfers are often performed in the foot and ankle. Recently, interference screws have been a popular choice owing to their ease of use and fixation strength. Considering the benefits, one disadvantage of such devices is laceration of the soft tissues by the implant threads during placement that potentially weaken the structural integrity of the grafts. A shape memory polyetheretherketone bullet-in-sheath tenodesis device uses circumferential compression, eliminating potential damage from thread rotation and maintaining the soft tissue orientation of the graft. The aim of this study was to determine the pullout strength and failure mode for this device in both a synthetic bone analogue and porcine bone models. Thirteen mature bovine extensor tendons were secured into ten 4.0 × 4.0 × 4.0-cm cubes of 15-pound per cubic foot solid rigid polyurethane foam bone analogue models or 3 porcine femoral condyles using the 5 × 20-mm polyetheretherketone soft tissue anchor. The bullet-in-sheath device demonstrated a mean pullout of 280.84 N in the bone analog models and 419.47 N in the porcine bone models. (p = .001). The bullet-in-sheath design preserved the integrity of the tendon graft, and none of the implants dislodged from their original position.

Effect of anchor threads on the pullout strength: A biomechanical study

Pullout tests to determine the effect of anchor threads on the pullout strength was conducted by using universal testing machine, synthetic cancellous bone and thread-less metallic anchor. Anchors were inserted at 45°, 90° or 135° from the surface and they were pulled at 45° from the surface. The maximum load to failure was compared among the 3 insertion angles. Pullout strength of the anchors inserted at 45° was significantly greater than those inserted at 90° or 135°. Pullout strength of the thread-less anchor was the greatest when it was inserted at 45° to the bone surface.

Level of evidence

level II.

A biomechanical study on suture anchor insertion angle: Which is better, 90° or 45°?

INTRODUCTION

The purpose of this study was to compare the pullout strength of anchors inserted at 90° and 45° to the bone surface using synthetic bones and porcine humeri.

SUBJECTS AND METHODS

Pullout tests were performed by universal testing machine. Synthetic cancellous bones of 0.08, 0.16, and 0.24 g/cm³ (defining as low, medium and high density, respectively) with 2-mm-thick cortical bone model attached on one side and the greater tuberosity of porcine humeri (average bone density, 270 mg/cm³) were chosen for pullout tests. Metallic anchors were inserted at 90° or 45° to the surface and pulled at 90° or 45° from the surface. The maximum load to failure for each condition was recorded. Differences in pullout failure loads between insertion angle, pulling angle, and bone density were analyzed.

RESULTS

When the sutures were pulled at 90° in low, medium, high density bones, and porcine humeri, 90°-inserted-anchors showed higher pullout strength than the 45°-inserted-anchors (534.6 ± 28.9 N vs. 488.1 ± 25.3 N (p < 0.05), 636.8 ± 25.3 N vs. 517.5 ± 27.4 N (p < 0.01), 735.6 ± 45.1 N vs. 557.0 ± 42.5 N (p < 0.01), and 285.6 ± 47.2 N vs. 181.4 ± 31.3 N (p < 0.01), respectively). When the sutures were pulled at 45° in low, medium density bones and porcine humeri, 90°-inserted-anchors showed higher pullout strength than the 45°-inserted-anchors (651.1 ± 38.3 N vs. 529.4 ± 37.6 N (p < 0.01), 711.4 ± 25.3 N vs. 599.2 ± 29.8 N (p < 0.01), and 265.3 ± 49.0 N vs. 181.5 ± 29.4 N (p < 0.01), respectively).

CONCLUSION

Pullout strength of the anchors inserted at 90° to the bone surface was greater than the anchors inserted at 45° regardless of the bone density.

Suture slippage in knotless suture anchors resulting in subacromial-subdeltoid bursitis

Rotator cuff repair using a suture bridge and knotless suture anchors is a relatively new, but increasingly used technique. The suture bridge technique creates an anatomically similar and more secure rotator cuff repair compared with conventional arthroscopic techniques and the use of knotless anchors eliminates the challenges associated with knot tying during arthroscopic surgery. However, previous in vitro biomechanical tests have shown that the hold of the suture in a knotless suture anchor is far lower than the pullout strength of the anchor from bone. Up until now slippage has been a theoretical concern. We present a prospectively diagnosed case of in vivo suture loosening after rotator cuff repair using a knotless bridge technique resulting in subacromial-subdeltoid bursitis.