Editorial Commentary: Size Matters: Biomechanical Analysis of All-Suture Suture-Anchor Fixation Compared to Conventional Suture Anchors and Interference Screws for Biceps Tenodesis

All-suture anchor size and drill angle influence load to failure in a porcine model of subpectoral biceps tenodesis, a biomechanical study

BACKGROUND

Tenodesis of the long head of the biceps tendon is frequently performed in shoulder surgery, and all-suture anchors have become more popular as fixation methods. However, uncertainty still exists regarding the ultimate load to failure of all-suture anchors and the best insertion angle at a cortical humeral insertion point.

PURPOSE

The purpose of this study was to compare the biomechanical characteristics of three types of all-suture anchors frequently used for biceps tenodesis. In addition, the influence of two different insertion angles was observed in a porcine humeri model.

METHODS

The ultimate load to failure and failure mode of three types of all-suture anchors (1.6 FiberTak®, 1.9 FiberTak®, 2.6 FiberTak®, Arthrex®) applicable for subpectoral biceps tenodesis were evaluated at 90° and 45° insertion angles in 12 fresh-frozen porcine humeri. The anchors were inserted equally alternated in a randomized manner at three different insertion sites along the bicipital groove, and the suture tapes were knotted around a rod for pullout testing. In total, 36 anchors were evaluated in a universal testing machine (Zwick & Roell).

RESULTS

The 2.6 FiberTak® shows higher ultimate loads to failure with a 90° insertion angle (944.0 N ± 169.7 N; 537.0 N ± 308.8 N) compared to the 1.9 FiberTak® (677.8 N ± 57.7 N; 426.3 N ± 167.0 N, p-value: 0.0080) and 1.6 FiberTak® (733.0 N ± 67.6 N; 450.0 N ± 155.8 N, p-value: 0.0018). All anchor types show significantly higher ultimate loads to failure and smaller standard deviations at the 90° insertion angle than at the 45° insertion angle. The major failure mode was anchor pullout. Only the 2.6 FiberTak® anchors showed suture breakage as the major failure mode when placed with a 90° insertion angle.

CONCLUSIONS

All three all-suture anchors are suitable fixation methods for subpectoral biceps tenodesis. Regarding our data, we recommend 90° as the optimum insertion angle.

CLINICAL RELEVANCE

The influence of anchor size and insertion angle of an all-suture anchor should be known by the surgeon for optimizing ultimate loads to failure and for achieving a secure fixation.

Increased Load to Failure in Biceps Tenodesis With All-Suture Suture Anchor Compared With Interference Screw: A Cadaveric Biomechanical Study

PURPOSE

To compare the biomechanical characteristics of a single radially expanding all-suture anchor with an interference screw for open subpectoral long head of biceps tendon (LHBT) tenodesis.

METHODS

Eighteen fresh-frozen matched-pair human cadaveric humeri were used for this biomechanical study. The matched pair humeri were randomly assigned into 2 experimental biceps tenodesis groups: conventional interference screw (CIS) or all-suture suture anchor (ASSA). Open subpectoral LHBT tenodesis was then performed and biomechanical testing was performed using a servohydraulic test frame. A preload of 5 N was applied for 2 minutes before cyclic loading. Displacement was recorded at cycle 300 (D300) and cycle 500 (D500) and at ultimate failure. Data recorded included displacement, load to failure, displacement at failure. Paired t test was used for analysis.

RESULTS

Decreased displacement was observed for the CIS group at D300 (1.67 ± 0.57 mm vs 3.35 ± 2.24 mm; P = .04), D500 (2.00 ± 0.76 mm vs 3.87 ± 2.20 mm; P = .04), and at failure (5.17 ± 3.05 mm vs 10.76 ± 2.66 mm; P < .001). Load to failure was lower in CIS specimens (170 ± 24.5 N vs 217.8 ± 51.54 N; P = .02). Failure in each case was tendon pullout for all CIS specimens; in ASSA 6 specimens failed as the suture pulled through the tendon, 2 specimens failed by suture breakage. No difference in stiffness was observed between the 2 groups (CIS = 98.33 ± 22.98 N/m vs ASSA = 75.94 ± 44.83 N/m; P = .20).

CONCLUSIONS

Our study found that open subpectoral biceps tenodesis performed with an ASSA construct results in increased load to failure as compared with CIS. However, the CIS did demonstrate decreased displacement as compared to ASSA in this cadaveric biomechanical study.

CLINICAL RELEVANCE

ASSA and CIS at time zero provide fixation as indicated by the provider intraoperatively for LHBT tenodesis. ASSA, however, does remove less cortical bone than does CIS and therefore produces a smaller stress riser in the proximal humerus. Further testing as to the integrity of ASSA is warranted to determine the integrity of the tenodesis with cyclical loading.