Search

Background: The purpose of this investigation was to compare the magnitude of rotatory knee laxity in patients with a partial anterior cruciate ligament (ACL) tear, those with a complete ACL tear, and those who had undergone a failed ACL reconstruction. It was hypothesized that rotatory knee laxity would increase with increasing injury grade, with knees with partial ACL tears demonstrating the lowest rotatory laxity and knees that had undergone failed ACL reconstruction demonstrating the highest rotatory laxity. Methods: A prospective multicenter study cohort of 354 patients who had undergone ACL reconstruction between 2012 and 2018 was examined. All patients had both injured and contralateral healthy knees evaluated using standardized, preoperative quantitative pivot shift testing, determined by a validated, image-based tablet software application and a surface-mounted accelerometer. Quantitative pivot shift was compared with the contralateral healthy knee in 20 patients with partial ACL tears, 257 patients with complete ACL tears, and 27 patients who had undergone a failed ACL reconstruction. Comparisons were made using 1-way analysis of variance (ANOVA) with post hoc 2-sample t tests with Bonferroni correction. Significance was set at p < 0.05. Results: There were stepwise increases in side-to-side differences in quantitative pivot shift in terms of lateral knee compartment translation for patients with partial ACL tears (mean [and standard deviation], 1.4 ± 1.5 mm), those with complete ACL tears (2.5 ± 2.1 mm), and those who had undergone failed ACL reconstruction (3.3 ± 1.9 mm) (p = 0.01) and increases in terms of lateral compartment acceleration for patients with partial ACL tears (0.7 ± 1.4 m/s2), those with complete ACL tears (2.3 ± 3.1 m/s2), and those who had undergone failed ACL reconstruction (2.4 ± 5.5 m/s2) (p = 0.01). A significant difference in lateral knee compartment translation was found when comparing patients with partial ACL tears and those with complete ACL tears (1.2 ± 2.1 mm [95% confidence interval (CI), 0.2 to 2.1 mm]; p = 0.02) and patients with partial ACL tears and those who had undergone failed ACL reconstruction (1.9 ± 1.7 mm [95% CI, 0.8 to 2.9 mm]; p = 0.001), but not when comparing patients with complete ACL tears and those who had undergone failed ACL reconstruction (0.8 ± 2.1 [95% CI, −0.1 to 1.6 mm]; p = 0.09). Increased lateral compartment acceleration was found when comparing patients with partial ACL tears and those with complete ACL tears (1.5 ± 3.0 m/s2 [95% CI, 0.8 to 2.3 m/s2]; p = 0.0002), but not when comparing patients with complete ACL tears and those who had undergone failed ACL reconstruction (0.1 ± 3.4 m/s2 [95% CI, −2.2 to 2.4 m/s2]; p = 0.93) or patients with partial ACL tears and those who had undergone failed ACL reconstruction (1.7 ± 4.2 m/s2 [95% CI, −0.7 to 4.0 m/s2]; p = 0.16). An increasing lateral compartment translation of the contralateral, ACL-healthy knee was found in patients with partial ACL tears (0.8 mm), those with complete ACL tears (1.2 mm), and those who had undergone failed ACL reconstruction (1.7 mm) (p < 0.05). Conclusions: A progressive increase in rotatory knee laxity, defined by side-to-side differences in quantitative pivot shift, was observed in patients with partial ACL tears, those with complete ACL tears, and those who had undergone failed ACL reconstruction. These results may be helpful when assessing outcomes and considering indications for the management of high-grade rotatory knee laxity. Level of Evidence: Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Background: The biomechanical pathophysiology of chronic lateral ankle instability (CLAI) is not fully understood. Planter pressure is susceptible to subtle changes in foot and ankle movement and could be used to detect CLAI. Therefore, this study aimed to compare plantar pressure between patients with CLAI and healthy subjects.Methods: Eighteen patients with CLAI who were scheduled for anterolateral ligament repair (9 women and 9 men) and 100 healthy subjects (50 women and 50 men) were included. Using an in-shoe pressure sensor system with ten plantar pressure sensors, the plantar pressure was recorded at a sampling rate of 200 Hz while walking. Analyses were adjusted for body mass index and gait speed.Results: Patients with CLAI had a significantly lower peak pressure on the hallux and toes than did healthy subjects. However, patients with CLAI had a significantly higher peak pressure on the medial aspect of the foot than did healthy subjects. Conclusions: The planter pressure distribution significantly differed between patients with CLAI and healthy subjects. The difference could have been due to a compensatory mechanism to prevent ankle instability. These findings could be used to elucidate the biomechanical pathophysiology of CLAI.