Three Medial All Suture Anchors Improves Contact Force Compared to Two Hard Body Anchors in a Biomechanical Two-Tendon Rotator Cuff Tear Model

Abstract

Purpose: To biomechanically compare a knotless double-row construct with 3 medial all-suture (3AS) anchors with a standard 2 medial hard body (2HB) anchor construct.

Methods: Twelve matched cadaveric shoulder specimens with a mean age of 57 years (range: 54-61 years) were randomized to receive a knotless double-row repair with either a 3AS or 2HB construct. In the 3AS construct, three 2.6-mm all-suture anchors were placed adjacent to the articular margin and secured laterally with two 4.75-mm knotless hard body anchors. In the 2HB construct, two 4.75-mm medial hard body anchors were placed medially, lateral fixation was identical to the 3AS construct. Creep, displacement, stiffness, and ultimate load were recorded for each sample. In addition, a SynDaver model was used to compare contact pressure between the 2 repair constructs.

Results: There were no differences in cyclic displacement at 1, 30, and 100 cycles (P = .616, .497, .190, respectively), cyclic stiffness (.928), ultimate load (.445), or load to failure (P = .445) between the 2 constructs. The 3AS repair construct had improved contact pressure between tendon and bone when compared with the 2HB construct at loads of 20 N, 30 N, and 40 N (P = .01, .02, and .04, respectively).

Conclusions: Displacement and load to failure properties are similar between knotless constructs using either 2HB or 3AS for the medial row. However, contact force may improve with the use of 3 medial all-suture anchors.

Clinical relevance: As all-suture anchors are smaller in size when compared with hard body anchors. For this reason, there is potential to place an additional all-suture medial anchor to improve contact force and potentially improve rotator cuff healing when compared with the use of hard body anchors.

Fig 1

Schematics of the repair constructs in a right shoulder, which were evaluated biomechanically. (A) Repair using 3 medial all-suture anchors and 2 lateral hard body anchors. (B) Repair using 2 medial hard body with 2-mm tape and 2 lateral hard body anchors.

Fig 2

Photograph of the testing assembly, which consists of a uniaxial Servo Hydraulic Instron Mechanical Testing System, a variable angle platform, and attached aluminum custom fixture. Arrow indicates the line of pull during testing. (RC, the rotator cuff.)

Fig 3

Photograph of Syndaver model contact force setup and comparative pressure maps with legend detailing color and force relationship. (2HB, two hard body anchors; 3AS, 3 medial all-suture anchors.)

Fig 4

Average cyclic displacements by 1, 30, and 100 cycle counts of 3AS and 2HB techniques. (2HB, two hard body anchors; 3AS, 3 medial all-suture anchors.)

Fig 5

Contact force in Newtons (N) for the 2 hard body (2HB) and 3 medial all-suture (3AS) anchor constructs. Statistically significant differences were observed at 20, 30, and 40 N of load. Asterisks denote significance.