The principal finding of the current study is that the posterior draw force is not helpful in enhancing postoperative stability during ACL graft fixation. Moreover, the postoperative clinical outcomes were similar in the groups.
Almekinders et al. had first described abnormal tibiofemoral positioning after an ACL injury. They suggested that untreated ACL ruptures result in irreducible anterior tibial subluxation, and this phenomenon was especially evident in patients with failed ACL reconstruction on plain radiographs. McDonald et al. investigated tibiofemoral subluxation after ACL tears in more detail using magnetic resonance imaging. In their study, patients were divided into four experimental cohorts according to their ACL status: intact ACL, acute ACL disruption (within 2 months of an ACL tear), chronic ACL disruption (more than 12 months after an ACL tear), and failed ACL reconstruction. The study demonstrated significantly increased medial and lateral compartment subluxation in patients with chronic ACL disruption than in those with normal knees; however, patients with acute ACL tears did not show significant subluxation. In the current study, the mean time from injury to surgery was 9.2 and 7.2 weeks in the non-draw and draw groups, respectively. Therefore, in our study, it was too early for the tibiofemoral subluxation to have occurred. We think there would be no significant postoperative STSD difference between the two groups because subluxation did not occur. To identify the efficacy of posterior draw force during ACL graft fixation in patients with tibiofemoral subluxation, further investigations with a revised ACL reconstruction cohort or chronic ACL deficiency cohort is necessary.
Mae et al. had conducted a cadaveric investigation with respect to graft tension during ACL reconstruction. They suggested that the tibia moved proximally and posteriorly during tensioning in the graft fixation stage. After graft fixation, the proximal and posterior tibial forces caused the tibia to move proximally and posteriorly. We believe that our results support the hypothesis of the previous study. Adequate graft tensioning causes the tibia to move posteriorly; therefore, intentional posterior draw is not necessary during ACL graft fixation.
This study has some limitations. First, factors, such as fixation method, graft selection, and tunnel position, could be confounding factors for postoperative stability. However, two fellowship-trained surgeons performed the same surgical procedure, except for the posterior draw force during graft fixation. Moreover, demographic data and preoperative data were similar between both groups; therefore, it was sufficient to determine the effect of posterior draw on postoperative stability after ACL reconstruction. Second, follow-up was relatively short and, therefore, survival analysis or long-term results could not be fully evaluated. Third, this was a retrospective study, which has inherent limitations and biases. Fourth, the posterior draw force was applied manually. Therefore, a constant force would not have been applied to the patients in the draw group, which could be a bias in interpreting the results.