The purpose of this study was to evaluate the load to failure, stiffness, displacement under cyclic loading, and footprint reconstruction of two different fixations at time zero. The number of suture passages through the tendon was equal (
n = 4) between the groups to focus on bony fixation strength. Generated results did confirm the original hypothesis that the transosseous fixation technique restores similar fixation strength in a revision case scenario compared to primary single row anchor fixation. We found no significant difference in the biomechanical properties of the compared techniques. The rotator cuff repair represents one of the most frequently performed orthopedic surgical intervention [
28]. Hence of numerous technological innovations, the re-tear rate is still unsatisfactory high [
3,
4,
7,
10] .With a raising number of surgeons performing their arthroscopic rotator cuff repairs with suture anchors our attention has been placed on a possible revision fixation technique. To our mind the TOR serves as a reasonable option to fulfill this task preserving similar biomechanical parameters by changing the fixation site. McLaughlin was the first one describing a transosseous rotator cuff repair back in 1944 [
29]. Since then a progress of technological improvements established a save and reproducible technique that can even be performed arthroscopically [
19]. According to Gerber et al. [
30], in theory a perfect repair should combined high fixation strength, minimal gap formation, and sufficient mechanical stability for tendon-bone healing. The existing literature consist of studies demonstrating that transosseous techniques have equivalent biomechanical properties relative to suture anchor fixation [
21,
31‐
33]. Lately, Behrens et al. [
34] showed that traditional transosseous suture construct without anchors can even provide an initial fixation strength equivalent to suture bridge repairs. The stress load is distributed wider in the bone tunnel of the transosseous repair, whereas in suture anchor repair, resulting in less local stress loads [
35]. In addition, the pressure is more homogenously assigned in transosseous sutures in opposite to the anchor repair, where high values may be a risk factor for ischemic tissue damage [
36]. To evaluate the Gap-formation and displacement two optical markers were positioned centric on either side of the repair as shown in Fig.
1c. This position was chosen to analyze the average displacement since Tashjian et al. [
32] found that gapping significantly increased from the anterior to posterior region. The gap formation observed in our three groups did not differ significantly and approached similar values as previously reported in literature [
34]. Hence, we had two failures in groups A and B and no failure in group C during cyclic loading due to anchor pull outs caused by weak bone quality. The bone quality (BMD) was measured for each specimen and did not differ between groups (group A mean 0.361 g/cm
2 ± 0.05 and group B 0.435 g/cm
2 ± 0.09
p = 0.094). The macroscopically decortication was performed after the BMD measuring and prior to the repairs to mimic poor bone quality. In regarding to Tingart et al. [
37] who published that a successful rotator cuff repair highly depends the bone density at the greater tuberosity we expected to weaken our primary suture anchor repair by this decortication process but we still reached comparable anchor pull out values compared to the literature [
31]. Pointing out that we may did not weaken the bone significantly even if macroscopically a full removal of cortical bone was performed. Pointing out that the suture anchors mainly rely on the trabecular, not the cortical bone [
38]. During our ultimate load to failure testing, anchor pullout was the main failure mode in all groups A-C. The most interesting factor is that we were able to show that even after pulling out a suture anchor repair the subsequent implanted TOR was not significantly weaker than the initial anchor nor the initial TOR. Leading to the assumption that after a failed single row anchor repair the TOR is a possible revision option.
Knowing the initial strength characteristics of different rotator cuff repair techniques may influence surgical decision-making and may ultimately improve patient outcomes. Traditionally, the TOR technique was performed open and later modified to mini-open procedures. Apreleva et al. [
39] demonstrated that TOR provides superior supraspinatus footprint coverage compared to suture anchor systems. Similar results were found in our study comparing a transosseous repair with a single row suture anchor.. The primary limitation of this study is that it is an in-vitro study only incorporating fixation strength at time point zero and a small sample size. The results cannot be extrapolated to the potential impact of tendon healing. Further the study specimens had intact rotator cuff tendons that do not replicate normal tendon and joint degeneration. We also created an isolated supraspinatus defect, which does not necessarily replicate the clinical situation. We try to include specimens with comparable age and bone quality. Lastly, the repairs in our study were performed under the ideal condition of being open procedures. Finally, the results of our study suggest that the initial fixation strength of single row suture anchor and TOR for rotator cuff repair at time point zero with comparable tendon and bone is equivalent. Both reconstructions prevented Gap-formation and early failure but preserved good footprint coverage. The revision TOR proved its biomechanical properties to be fully capable as an option for primary and secondary repairs. The clinical relevance of this study showed that there is no difference when comparing a current used arthroscopic single row suture anchor repair with a novel arthroscopic transosseous technique, supporting its use as a revision option.