Following anterior cruciate ligament (ACL) injury, quantitative pivot shift (QPS) testing using the PIVOT technology can detect high- and low-grade rotatory instability.(1,2) Previously, preoperative rotatory knee laxity measured using an optical tracking system with manual load application was shown to predict postoperative rotatory knee laxity following ACL reconstruction (ACLR).(3) However, this study was performed with non-standardized external loads leading to potential error. To better inform treatment-decisions, we aimed to determine whether a correlation exists between preoperative QPS and postoperative knee kinematics during running at 6 and 12 months following ACLR with or without lateral extraarticular tenodesis (LET) using a highly precise in vivo analysis system.(4) A positive correlation between preoperative QPS and postoperative anterior-posterior tibial translation and internal-external tibial rotation at 6 and 12 months following ACLR with or without LET was hypothesized.
Twenty patients with an ACL injury (age 20.8 ± 6.8 years, 12 males) were randomized to undergo anatomic ACLR with or without LET using either bone-patellar tendon-bone or quadriceps tendon autograft as part of a prospective randomized trial (No. NCT0291340). To be included in this study, preoperative examination under anesthesia demonstrating high-grade rotatory instability (=3 mm of lateral compartment translation or a side-to-side difference =50% using PIVOT technology) was required.(2) At 6 and 12 months postoperatively, in vivo kinematic data was collected using dynamic biplanar radiography superimposed with high-resolution computed tomography scans of patients’ knees during downhill running at 2 m/s.(4) Total (maximum subtracted by minimum) anterior-posterior tibial translation and internal-external tibial rotation were calculated from foot-strike to mid-stance of the gait cycle. Spearman’s rho was calculated to evaluate for correlation between preoperative QPS and postoperative kinematics using SPSS statistics (IBM) with p<0.05.
Preoperatively, all patients were confirmed to have high-grade rotatory knee instability with a QPS of 5.0 ± 1.6 mm. No statistically significant correlations were observed between preoperative QPS and total anterior-posterior tibial translation, or between preoperative QPS and total internal-external tibial rotation at 6 and 12 months postoperatively for combined ACLR and ACLR with LET patients as well as ACLR patients or ACLR with LET patients analyzed separately.
The main finding of this study was that there were no significant correlations between preoperative QPS and postoperative in vivo kinematics at 6 and 12 months following ACLR with or without LET. These findings suggest that preoperative QPS does not correlate with postoperative rotatory knee stability following anatomic ACLR as there are likely other patient, injury, and surgical factors which play a role in determining postoperative knee kinematics. In addition, additional LET does not appear to be necessary in all cases of high-grade rotatory instability as other factors such as graft choice may be more important. In conclusion, additional LET does not appear to be required in all cases of high-grade rotatory instability as preoperative instability does not correlate with postoperative in vivo kinematics following ACLR with or without LET.
References: 1)Musahl. AJSM. 2016. 2)Hoshino. KSSTA. 2012. 3)Signorelli. Scand J Med Sci Sports. 2013. 4)Anderst. Med Engl Phys. 2009.