Does It Really Matter? The Pessimistic Interpretation of Contralateral Anterior Laxity as a Predictor of ACL Reconstruction Outcomes: Commentary on an article by Sung-Jae Kim, MD, PhD, et al.: “Does Anterior Laxity of the Uninjured Knee Influence Clinical Outcomes of ACL Reconstruction?”
第一作者:Samuel A. Taylor
2014-04-03 点击量:923 我要说
Samuel A. Taylor,Robert Marx
Kim et al. investigated the role of contralateral knee laxity as a predictor of clinical outcomes following anterior cruciate ligament (ACL) reconstruction. The authors should be applauded for this pursuit and attempt to investigate a previously unexamined predictor of these outcomes. The reader should not, however, overlook the fact that the significant differences, on which the conclusions hinge, are in fact clinically insignificant and the authors’ conclusions are therefore grossly overstated. Many authors have explored the role of nonmodifiable patient-specific risk factors such as sex, age, excessive posterior tibial slope, and generalized ligamentous laxity as predisposing factors for ACL injury. Myer et al.determined that knee hyperextension and side-to-side differences in anterior-posterior laxity resulted in fivefold and fourfold increases in the odds of ACL injury, respectively, in a large prospective cohort of female soccer and basketball players. The authors of another study found that generalized ligamentous knee laxity and knee hyperextension were more common among those who sustained an ACL injury compared with controls. Uhorchak et al.determined that a narrow femoral notch, generalized joint laxity, and KT2000 arthrometer (MEDmetric) measurements more than one standard deviation above the mean were independent risk factors for the occurrence of noncontact ACL injury in a cohort of nearly 1200 prospectively evaluated U.S. military cadets. The authors of another study determined that knee hyperextension was predictive of postoperative stability and function independent of generalized joint laxity. Fewer studies, however, have demonstrated modifiable factors that produce suboptimal ACL reconstruction outcomes. Spindler and colleagues in the MOON (Multicenter Orthopaedics Outcomes Network) group identified use of autograft, smoking status, and body mass index as variables that can affect functional outcome scores. Kowalchuk et al.showed that both a body mass index of >30 kg/m2 and smoking adversely affected outcomes following ACL reconstruction. Although the authors of the present study should be praised for their excellent study design, there are several limitations that must be considered. First, patients with generalized ligamentous laxity, as assessed by the presence of four or more positive examinations on the Beighton and Horan joint mobility index, were excluded. Three groups were then created on the basis of the anterior-posterior laxity of the contralateral knee: below average (Group 1), average (Group 2), and above average (Group 3) tibial translation as measured with the KT2000. The cohort was homogeneous with regard to surgeon, surgical technique, and postoperative rehabilitation. The three groups were also similar with regard to all demographic information collected in the study protocol. Second, although the authors report that differences in the functional outcome measures and in the side-to-side laxity differences among the three groups reached significance, their conclusions are overstated and are not clinically relevant. As they astutely point out in their limitations section, the maximal differences among the groups (those between Groups 1 and 3) for the Lysholm (6.4) and International Knee Documentation Committee (IKDC) subjective (6.7) scores are less than the minimal clinically important difference for either outcome measure, indicating that these health states are in fact not appreciably different from one another.