This novel study highlighted the significant differences in the utilization of the femoral tunnel between the ALD and FLD. Additionally, it was the first study to our knowledge, to use CT to observe the filling of the femoral tunnel graft, making up for the lack of clinical data of on ALDs. Most importantly, this study found that the use of an ALD leads to better use of the lateral femoral tunnel with a smaller gap distance but does not completely eliminate the graft top gap or increase the length of graft insertion. Second, it found that CT can be effectively used, with good reliability, to evaluate graft filling in the femoral tunnel. These findings were consistent with our hypothesis. Although the ALD has been reported to have no gap distance, our findings show that there was still a gap distance in the ALD group (1.90 ± 1.81 mm). One advantage of the ALD is that it may help clinicians to select a more suitable fixation device for patients, especially for patients with a short femoral tunnel. Our findings will enable clinicians to better understand the differences between the two devices and help them to make better decisions regarding the preferred device for use. However, the prolongation of the ALD still requires further investigation in future studies.
In previous studies, investigators used magnetic resonance imaging (MRI) to evaluate the femoral tunnel and graft [2, 3, 16, 17]. Ahmet.et al reported that the gap distance was 4.6 ± 0.3 mm and 9.5 ± 1.6 mm in the groups in which toggle loc with zip loop femoral fixation ALDs and ENDOBUTTON CL fixation loop devices were used, respectively . These findings are similar to those obtained in our study; however, we found that the RIGIDLOOP had a smaller gap distance (1.90 ± 1.81 mm). This difference may be due to the use of different brands of ALDs. One biomechanical study showed that the stability of the RIGIDLOOP was closest to that of the fixed-loop device . However, to our knowledge no clinical study has reported the postoperative tunnel filling of the RIGIDLOOP device. Moreover, recent studies have indicated that gap distances are positively correlated with postoperative femoral tunnel widening and that they may affect revascularization after ACLR based on CT and MRI image findings [2, 14, 16, 17, 19–21]. These findings suggest that the large space may affect the prognosis of patients. Although we only observed patients on the first day after surgery, these findings may provide a reference for future studies.
In this study, we decided to use CT for evaluation because all patients who underwent ACLR in our hospital required CT evaluation to determine bone tunnel position and the postoperative device position. MRI examinations require a longer wait time and cost more money, thus the use of CT was more viable. Given that CT was used for all patients, there was a big enough sample size to ensure the power of our results. Additionally, all radiograph measurements were conducted by one experienced radiologist who was specialized in musculoskeletal imaging. Finally, we tested the consistency of our measurements using CT images and found good consistency and repeatability between the two observers (ICC = 0.956, P < 0.001). Therefore, we believe that our results obtained using CT imaging were reliable.
Compared to the FLD, adjustable-loop femoral cortical suspension devices are relatively new. They offer various advantages: graft maximization in femoral tunnels, avoidance of the over drilling of the femoral tunnel, and obviation of the need to calculate the loop length [1, 5, 6]. Our study supports the findings from previous studies and provides more information for clinicians. A full understanding of these advantages of ALDs may help clinicians make more appropriate choices for patients, especially those with short femoral tunnels. The ALD allows for better use of the femoral tunnel and retains adequate thickness of the lateral femoral cortex.
There are several limitations of this study which merit a mention here. First, this was a retrospective study thus potentially limiting the validity of our findings. Second, we did not report on the prognosis for the two groups of patients. This study only provided information on the postoperative imaging parameters for the two kinds of suspension devices used. We did not provide data on postoperative follow-up observations, whether the ALD was relaxed, and whether the prognosis of patients differed. This requires evaluation in future studies. Third, we used CT rather than MRI to evaluate the graft filling conditions. This may have exposed patients to a certain amount of radiation. Finally, this study was only able to exhibit the difference between these two devices using our specific surgical approach, thus limiting the generalizability of our results. Different devices and surgical methods may produce different results.