The relationship of anterior and rotatory laxity between surgical navigation and clinical outcome after ACL reconstruction

Purpose Recently, a computer-assisted navigation system has been used for the quantitative evaluation not only of anterior-posterior (AP) laxity but also rotational laxity of the tibia intraoperatively. The purpose of this study was to investigate how intraoperative AP or rotational laxities measured by the navigation system could correlate with postoperative AP and rotational laxities of the patients. Methods 125 patients who underwent primary isolated anatomical single-or double-bundle ACL reconstruction or augmentation using multistranded autologous hamstring tendons were included in the study after a minimum of 2-year follow-up. Clinically, absolute value and side-to-side difference (SSD) of AP translation of the tibia were measured by KT-2000 preoperatively and postoperatively. Intraoperative measurement of AP translation of the tibia and total range of tibial rotation of the ACL-injured knee were carried out using the computer-assisted navigation system. We have investigated the relationship between intraoperative measurements using the navigation system and AP laxity measurements using the KT-2000 knee arthrometer as well as rotational laxity measurements using the manual pivot shift test. Results There was a positive correlation between the SSD of preoperative AP translation of the tibia measured by KT-2000 arthrometer and the reduction in AP laxity following ACL reconstruction measured by the navigation system. However, we found no significant correlation between the reduction in AP laxity measured by the navigation system and the SSD of AP translation of the tibia measured by the KT-2000 arthrometer at final follow-up. Postoperatively, eight patients had a positive pivot shift test. Using the navigation system pre- and post-ACL reconstruction, these patients could not be identified by high absolute values for AP laxity nor rotational laxity. Conclusion Although AP and rotational laxities vary largely among the patients, and AP and rotational stabilization are successfully achieved immediately after ACL reconstruction, intraoperative AP and rotational laxity measured by the navigation system did not influence the postoperative AP and rotational laxities after ACL reconstruction.