Summary

The 4.5mm Bio-Corkscrew anchor appears to provide the most robust fixation during SCR as it demonstrated the strongest maximal load, had minimal elongation and excursion with cyclic testing, and did not fail during cyclic testing.

Abstract

Superior capsular reconstruction (SCR) is an emerging treatment alternative for the management of irreparable rotator cuff tears. It has encouraging biomechanical data that has translated to largely acceptable clinical outcomes. To date, there remains a paucity of data examining anchor strength at the superior glenoid neck. Thus, the purpose of this biomechanical study was to determine the optimal anchor construct at the glenoid neck through cyclic testing and load to failure testing

This was an IRB exempt biomechanical study performed in a controlled laboratory setting with a total of 20 fresh-frozen cadaveric shoulders. Specimens were thawed and mounted in the beach chair position from the medial scapular border. The sternoclavicular joint was rigidly stabilized through traction suspension, and a radiolucent bolt was utilized across the coracoclavicular interval to maintain a rigid construct in the native anatomic shoulder position. Specimens were randomly divided into four groups: all-suture anchor (FiberTak; Arthrex, Naples FL), conventional 3.0 mm knotless suture anchor (SutureTak), 3.9 mm knotless PEEK Corkscrew anchor, and 4.5 mm Bio-Corkscrew anchor. After arthroscopic evaluation and debridement, each specimen was prepared with three anchors into the glenoid: (1) an anterosuperior anchor at 2 o’clock, (2) superior anchor at 12 o’clock, and (3) a posterosuperior anchor at 10 o’clock. All anchors were inserted into the superior glenoid 5-mm off of the glenoid rim. Each scapula was potted within a PVC cylinder using acrylic cement and mounted to a custom fixture secured to the base of an electromechanical materials testing system (MTS Insight 5, Eden Prairie, MN). Each specimen was positioned under the load cell such that the load applied was parallel to the axis of the cuff tendon. The free ends of the suture were attached to the load cell and tested in the following manner: (1) preload at 5 N for 2 minutes; (2) cyclic testing from 10 N to 100 N at 0.5 Hz for 200 cycles; and (3) load to failure at 12.5 mm/sec. Load-to-failure was performed immediately after cyclic testing. Time, force, and actuator displacement were synchronously recorded at 48 Hz using the MTS software. Data was presented as mean ± standard deviation. After confirming normality with a Shapiro-Wilk test, primary outcomes were compared using repeated measures analysis of variance (ANOVA) with a Bonferroni multiple-comparison correction. Alpha was set at 0.05.

During cyclic testing, two SutureTak anchors in the anterior position failed, one FiberTak anchor in the anterior position failed, and one FiberTak anchor in the superior position failed. Among the anchors that completed cyclic testing, there was no significant difference in cyclic elongation (P = 0.327) or cyclic excursion (P = 0.890) between the anterior, superior, and posterior glenoid anchor positions. However, there were significant differences between suture anchor groups. Cyclic elongation was significantly longer in the PEEK Corkscrew group relative to the other suture anchor groups (P < 0.02). There was no difference in cyclic elongation between the remaining three anchor groups. Cyclic excursion was significantly greater in the FiberTak group relative to all other suture anchor groups (P < 0.01). No other differences in cyclic excursion were observed between the studied anchor types. Among the anchors that completed cyclic testing, pull to failure testing was then performed. There were no significant differences in maximal load between the anterior, superior, and posterior glenoid anchor positions (P = 0.990). When examining anchor types, the Bio-Corkscrew group achieved the highest ultimate load (P < 0.001). No other differences in ultimate load were observed between the groups.