ISAKOS: 2019 Congress in Cancun, Mexico
ISAKOS

2019 ISAKOS Biennial Congress ePoster #1816

 

Cyclic Biomechanical Evaluation of Single-Tunnel Coracoclavicular Reconstruction: Is Augmentation Necessary?

Tyler R. Johnston, MD, Palo Alto, CA UNITED STATES
John G. Costouros, MD, FACS, Menlo Park, CA UNITED STATES
Anthony Behn, MS, Palo Alto, CA UNITED STATES
Timothy Thio, MS, Palo Alto, CA UNITED STATES

Stanford University, Redwood City, CA, UNITED STATES

FDA Status Cleared

Summary

Single-tunnel cortical button reconstruction of the CC joint significantly increases superior-inferior joint stiffness in a manner closely correlated with construct preload, while graft and suture augments and cyclic loading do not significantly alter SI-plane reconstruction biomechanics.

Abstract

Background

Coracoclavicular (CC) reconstruction is frequently performed with augments to help minimize clinical/radiographic failures without a thorough understanding of risks/benefits or preload effects.

Purpose

Compare single-tunnel (ST) cortical button (CB) CC reconstruction to augmentation with high-strength suture (CB + S) or tibialis anterior allograft (CB + G) under cyclic loading and load-to-failure conditions. Measure the effect of tensioning (preload) on superior-inferior (SI) and anterior-posterior (AP) load-displacements.
Study Design: Controlled laboratory study

Methods

Nine fresh-frozen cadaveric shoulders from five donors were disarticulated and potted for testing in a custom materials testing jig. Motion capture was used to measure scapular and clavicular displacements under physiologic loads: -10N to 70N SI and -25N to 25N AP for 10 cycles. Next, AC and CC ligaments were transected and CC ligaments were serially reconstructed with different techniques (CB, CB + S, and CB + G) in a randomized order, and exposed to 5,000 cycles of 10-70N superior-directed loading . Construct preload, and pre and post-cyclic testing displacements in SI and AP directions were recorded, followed by a superiorly directed load-to-failure.

Results

All reconstruction groups demonstrated significantly increased stiffness and reduced SI load-displacements vs intact state (p<0.04) before cyclic testing. Significant differences remained after cyclic testing, with average SI load-displacements of: 0.7+/-0.4mm, 0.5+/-0.3mm, and 0.7+/-0.4mm for the CB, CB + S, and CB + G groups respectively, compared to 2.3+/-1.5mm intact. SI loosening was minimal during cyclic loading, with 96% of reconstructed specimens loosening <0.5mm. Graft or suture augmentation did not significantly change SI load-displacements, but the CB alone group demonstrated significantly increased AP displacement vs intact and CB + S groups after cyclic testing. There were no significant differences in average failure loads between groups, all augmented groups failed at >700N. Across groups, preload tension was significantly inversely correlated with superior load-displacement p<0.005.

Conclusion

Single-tunnel cortical button-based CC reconstruction techniques significantly increase CC stiffness compared to native state, particularly in the SI direction (two-fold), in a manner highly correlated with preload tension. Suture augmentation may be beneficial to prevent AP creep and overload failures but does not significantly change superior force-displacements under cyclic loading.