DISCUSSION
The purpose of this study was to evaluate the biomechanical strength of a new technique for PASTA repairs—the PASTA Bridge.6 After creation of a partial-thickness tear on a cadaveric model, we compared the PASTA Bridge technique6 with a standard transtendon suture anchor repair. We hypothesized that the PASTA Bridge would yield equivalent or better biomechanical properties including the ultimate load to failure and the degree of strain at different locations in the repair. Our results supported this hypothesis. The PASTA Bridge was biomechanically equivalent to transtendon repair.
For repairs of partial-thickness rotator cuff tears, 2 traditional techniques are transtendon repairs and the “takedown” method of completing a partial tear into a full tear with a subsequent repair.13 While clinical outcomes of the 2 methods suggest no superiority over the other,13 studies have demonstrated a biomechanical advantage with transtendon repairs. Repairs of PASTA lesions exhibit both lower strain and displacement of the repaired tendon compared with a full-thickness repair.2-5 Failure of the “takedown” method results in a full-thickness rotator cuff tear as opposed to a partial tear. This outcome can prove to be more debilitating for the patient. Furthermore, Mazzocca and colleagues5 illustrated that for partial tears >25% thickness, the cuff strain returned to the intact state once repaired.
Our data suggest that biomechanically the transtendon and the PASTA Bridge6 techniques were equivalent. While the ultimate load and strain at repair sites are comparable, the PASTA Bridge is percutaneous and presents significantly less risk of complications. The PASTA Bridge6 uses a medial row horizontal mattress with a lateral row fixation to recreate the rotator cuff footprint. It has been postulated that reestablishing a higher percentage of the footprint can aide in tendon-bone healing, having valuable implications for both biological and clinical outcomes of the patient.3,4,14 Greater contact at the tendon-bone interface may allow more fibers to participate in the healing process.14 In their analysis of rotator cuff repair, Apreleva and colleagues14 asserted that more laterally placed suture anchors may increase the repair-site area. The lateral anchors of the PASTA Bridge help not only to increase the footprint and thereby the healing potential of the repair but also assist in taking pressure off the medial row anchors.
In their report on double-row rotator cuff repair, Lo and Burkhart3 suggest that double-row fixation is superior to single-row repairs for a variety of reasons. Primarily, double-row techniques increase the number of points of fixation, which will secondarily reduce both the stress and load at each suture point.3 This effect improves the overall strength of the repair construct. Use of the lateral anchor of the PASTA Bridge6 allows the medial anchors to act as pivot points. Placing the stress laterally, the configuration allows for movement and strain distribution without sacrificing the integrity of the repair. In our analysis, failure occurred by the tendon tearing mid-substance, humeral head breaking, tendon tearing at the repair site, and tearing at the musculotendinous junction (Figures 2-4). There was no instance of failure due to the construct itself indicating that the 2.4-mm medial anchors are more than adequate for the PASTA Bridge.6 When visually inspecting the samples after failure, there was no damage to the anchors or sutures. This observation indicates that the PASTA Bridge construct is remarkably strong and capable of withstanding excessive forces.
There were some potential limitations of this study. The small sample size modified the potential for identifying significant differences between the groups. A post-hoc power analysis revealed that a sample size of at least 20 matched pairs would be required to determine a significant difference between the 2 repair groups in strain at the repair site. We did not test this many pairs because the data was so similar after 6 matched pairs that it did not warrant continuing further. Additional research should be done with larger sample populations to evaluate the biomechanical efficacy of this technique further.
CONCLUSION
The PASTA Bridge6 creates a strong construct for repair of articular-sided partial-thickness tears of the supraspinatus. The data suggest the PASTA Bridge6 is biomechanically equivalent to the gold standard transtendon suture anchor repair. The PASTA Bridge6 is technically sound, percutaneous, and presents less risk of complications. It does not require arthroscopic knot tying and carries only minimal risk of damage to residual tissues. In our analysis, there were no failures of the actual construct, asserting that the PASTA Bridge6 is a strong, durable repair. The PASTA Bridge6 should be strongly considered by surgeons treating PASTA lesions.