The aim of this study was to compare the HB as innovative double-row technique with the clinically most common and convenient gluteal repair technique, the MA.
Our study demonstrates that HB technique showed a significant higher ultimate failure load compared to old-fashioned MA technique with less elongation during cyclic loading and a higher stiffness during pull-to-failure test for HB group, although this did not reach statistical significance. In summary HB technique showed a superior primary stability compared to the established transosseous Mason-Allen suture technique.
Plastic elongation is defined in this study as the deformation that irreversibly occurs during cyclic loading. In literature, it is additionally associated with stress softening, which is observed as a progressive decrease in tensile modulus prior to failure (19). The tendon loses its ability to absorb energy without returning to the unloaded reference state. This inelastic behavior may contribute to an early failure and rupture of the tendon or from a clinical perspective this may lead to disorders like muscle insufficiency or tendinopathy (19). As previously described, we equalized plastic elongation due to its irreversibility with gap formation. Taking this into account especially when treating elder patients with a poor tendon quality, it is obvious that a good primary stability of the refixed tendon is essential until solid healing to prevent a long period of immobilization (14). These findings are also very important for early functional rehabilitation, because tendon detachments occur most frequently in the early postoperative period, before bone-to-tendon healing is completed (20).
In this study we compared the rather new knotless HB with an already established transosseus suture repair technique. The Mason Allen technique is cost-efficient and no special equipment is needed. Therefore, it is often used in a large scale for multiple tendon refixations (21). Gerber et al. compared different conventional fixation techniques and concluded that modified Mason-Allen suture seems to be the superior technique because of stable fixation and broad-based fixation (14).
Furthermore, our study showed that HB reconstruction fails at the point of tendon, while the MA constructs demonstrates three failure modes: tendon failure (1/6), bone cutting (4/6) and muscle tear (1/6). This furthermore underlines the excellent primary stability of the reattached footprint after HB repair. It is generally agreed that restoration of the anatomical footprint is essential for good biomechanical results (22). As explanation, the advantage of broad-based anatomical footprint reconstruction using HB over the punctual rigid fixation (MA) enables not only a stable and reproducible refixation of the gluteal tendon from the beginning, but and possibly even more important a good mid- to long-term biological healing. Barrera et al. could determine that mini-open repair of chronic gluteus medius tendon tears using a double-row technique showed good clinical and functional outcomes at short follow-up (secondary stability) (23). Depending on our clinical experience, the HB technique shows good results also regarding secondary stability.
Biomechanical data on the different repair techniques for rotator cuff repair are well investigated but data for gluteal tendons are still rare. Some studies could demonstrate that double-row repair had higher ultimate failure load when comparing with single-row techniques for rotator cuff repair (24). To the best of our knowledge, Kahlenberg et al is the only biomechanical study with a single- versus double-row technique for gluteal tendon repair after hip abductor tears in a biomechanical cadaver study. However, MA repair was not performed and compared. They demonstrated that double-row suture repair yields improved footprint coverage and a mean but not significant higher yield load (8). Comparing both studies, we used a state-of-the-art technique for measuring the elongation, 3D optical measurement technique (150 Hz) vs. digital video (60 Hz). In addition, our mean values regarding failure load and stiffness trend were higher and therefore more stable and we could demonstrate significantly different results regarding failure load. However, since we could also detect only trends regarding reaching less elongation after cyclic loading when using HB technique maybe a greater sample size would assume statistical difference also in plastic elongation.
Limitations
This study has certain limitations. The comparison of both surgical techniques was performed in a biomechanical test setup and therefore only primary stability data could be achieved immediately after performed surgery. Additionally, we could not reach statistical significance regarding elongation and stiffness. However, due to cost and rareness of human cadaver, it was not possible to increase the number of tests run to get possibly significant results. However existing biomechanical studies deal with comparable number of cadavers used (8). Furthermore, our data showed a greater variance in HB group. This might be due to a reduced tissue quality caused by the freezing process or the slight imbalance regarding gender. Possible difference in tendon quality between specimens has also been reported in another biomechanical study by Kahlenberg et al. (8). Due to the test setup and the biomechanical setting of the study, both repair techniques were performed in an open and not endoscopic procedure. Maslaris et al. demonstrated that in a clinical routine there is no difference between open or endoscopic refixation of gluteal tendons concerning the outcome (25). Nevertheless, our results cannot be completely generalized to endoscopic abductor tendon repair although the newly analyzed Hip Bridge technique is feasible as a both endoscopic and open procedure.