The important finding of the present study was that additional ALLR helped gain better dynamic postural stability evaluated by YBT in revision ACLR cases at 1-year postoperative follow-up.
The renewed attention and confirmation of the ALL anatomy was made by several investigators in the early 2010s. Vincent et al.11 identified the ALL in patients undergoing total knee arthroplasty and Clae et al.10 also pointed out the ligament in the cadaver specimen. Many biomechanical studies of ALL followed and revealed that ALL is an important structure for the anterolateral rotatory stability of the knee. In a cadaver study, Sonnery-Cottet et al. showed that ALL affected rotational control of the knee at varying degrees of knee flexion during a pivot shift maneuver23. Parsons et al. reported in their cadaver study that ALL is an important stabilizer of the knee’s internal rotation at flexion angles greater than 35°13. Nielsen et al. also reported that augmented ALLR with ACLR in a cadaveric setting reduced internal rotation, varus rotation, and anterior translation knee laxity12.
There have been several reports suggesting that the clinical result of revision ACLR is generally inferior to that of primary ACLR24,25. In the case of revision ACLR, since it is a second or more relevant surgery on one knee, there is lesser room to spare than in primary ACLR. Therefore, close attention should be paid to the cause of the failure and the presenting symptoms. Both the cause and the symptoms should be managed thoroughly to prevent re-rupture. Residual rotational laxity is known to be the major cause of failure after ACLR, and a high pivot shift is one of the major symptoms. Recently, numerous studies reported significantly better knee stability after revision ACLR with additional ALLR. Yoon et al. reported that additional ALLR in revision ACLR cases with high-grade pivot shift improved both anteroposterior stability and rotational stability7. Louis et al. reported improved rotational stability and re-rupture risk with additional ALL stabilization procedures in revision ACLR cases in their multi-center study5. However, in terms of subjective patient outcomes usually evaluated using clinical questionnaires and scores, controversy persists regarding the effect of additional ALLR in revision ACLR cases. Yoon et al. reported no difference in clinical scores, while Lee et al. reported significantly better scores6,7. Furthermore, these previous studies concentrated on traditional clinical outcomes and stability assessments5,7.
Among the various measures that evaluate the results of either ACLR or revision ACLR, postural stability is an important measure to be taken seriously. Lack of sufficient postural stability of the involved limb is considered the main factor in the failure of ACLR. Paterno et al. reported that postural instability after ACLR is a predictor for ACL re-injury26. Whether the increased knee stability by additional ALLR in revision ACL cases improves the postural stability of the patient has not been studied widely.
Postural stability generally means the ability to regain the balance or control of the trunk and the lower limb21. Postural stability can be assessed in two different ways: static and dynamic27,28. In static postural stability evaluation, the subject is required to establish a firm base of support and maintain the position while limiting body movement. In dynamic postural stability evaluation, the subject is required to maintain balance while moving from a dynamic to a static position. For the general assessment after ACLR, such as evaluating the duration of rehabilitation and when to start sports activity, dynamic postural stability evaluation is more appropriate than static postural stability evaluation. Head et al. insisted that dynamic postural stability should be assessed carefully in the return-to-sports decision-making process after ACLR27,29.
The SEBT developed by Gray et al. was considered a reliable and valid method to measure dynamic postural stability18. However, the test was too time-consuming in a clinical setting. To apply the SEBT practically, the YBT was developed and its reliability has been proven by many researchers22,30. YBT is a relatively inexpensive and easy to apply test for clinicians31. While performing the YBT, the subjects are required to stand on one leg stance and squat down as far as they can. This movement requires concentric contraction strength of the quadriceps muscles and eccentric contraction strength of the hamstring muscles. Moreover, it requires the ability to maintain balance, which reflects the patient’s proprioceptive function18. Nowadays, YBT is considered one of the most popular research tools used for the assessment of dynamic postural stability21. Several studies have used YBT as one of their evaluation measures for ACLR results. However, few studies have used YBT in revision ACLR cases. In this study, we placed emphasis on the dynamic postural stability evaluated using YBT in comparing revision ACLR results for additional ALLR and confirmed that additional ALLR indeed improves dynamic postural stability in revision ACLR cases.
This study has limitations. First, this study was a retrospective comparative study. A prospective randomized study is always desirable in such kinds of comparative clinical analyses; however, it is difficult to design a prospective randomized study in revision ACLR cases because patients are usually desperate for the success of the surgery and do not want to participate in any kind of clinical study. Second, postoperative 1-year evaluation might be considered too short for the evaluation of results. However, return-to-sports activity is one of the major decision-making processes, and dynamic postural stability is the main factor to consider for those decisions. Because the time to return to sports is usually around a year after surgery, we thought that it is important to perform the evaluation 1-year postoperatively.