Physiologic Preoperative Knee Hyperextension Is a Predictor of Failure in an Anterior Cruciate Ligament Revision Cohort: A Report From the MARS Group

Abstract

<div class="section"> <a class="named-anchor" id="S1"> <!-- named anchor --> </a> <h5 class="section-title" id="d514625e87">Background</h5> <p id="P1">The occurrence of physiologic knee hyperextension in the revision anterior cruciate ligament (ACL) reconstruction population, and its effect on outcomes, has yet to be reported. </p> </div><div class="section"> <a class="named-anchor" id="S2"> <!-- named anchor --> </a> <h5 class="section-title" id="d514625e92">Hypothesis/Purpose</h5> <p id="P2">The prevalence of knee hyperextension in revision ACL reconstruction, and its effect on 2-year outcome were studied with the hypothesis that preoperative physiologic knee hyperextension ≥ 5 degrees is a risk factor for ACL graft rupture. </p> </div><div class="section"> <a class="named-anchor" id="S3"> <!-- named anchor --> </a> <h5 class="section-title" id="d514625e97">Study Design</h5> <p id="P3">Cohort study.</p> </div><div class="section"> <a class="named-anchor" id="S4"> <!-- named anchor --> </a> <h5 class="section-title" id="d514625e102">Methods</h5> <p id="P4">Revision ACL reconstruction patients were identified and prospectively enrolled between 2006 and 2011. Study inclusion criteria were patients undergoing single bundle graft reconstructions. Patients were followed up at 2 years, and asked to complete the identical set of outcome instruments (IKDC, KOOS, WOMAC, and Marx activity rating score), as well as to provide information regarding revision ACL graft failure. A regression model using graft failure as the dependent variable included age, gender, graft type at the time of the revision ACL surgery, and physiologic preoperative passive hyperextension greater than or equal to 5 degrees (HE≥5; “yes/no”), to assess these potential risk factors for clinical outcomes 2 years after revision ACL reconstruction. </p> </div><div class="section"> <a class="named-anchor" id="S5"> <!-- named anchor --> </a> <h5 class="section-title" id="d514625e107">Results</h5> <p id="P5">There were 1,145 subjects included in the analyses. Two-year follow-up was attained on 91%. The median age was 26, with age being a continuous variable. Those below the median were grouped as “younger” and those above “older” (Age of 25/75 quartiles: IQR= 20, 35), and 42% were female. There were 50% autografts, 48% allografts, and 2% which had a combination autograft plus allograft. Passive knee HE≥5 degrees was present in 374 (33%) of our revision cohort, with 52% being female. Graft rupture at 2-year follow-up occurred in 34 cases in our entire cohort, of which 12 were in our HE≥5 group (3.2% failure rate) and 22 were in the non-hyperextension group (2.9% failure rate). The median age of subjects that failed was 19, compared to 26 for those with intact grafts. Three variables included in our regression model were significant predictors of graft failure: younger age (odds ratio [OR] = 3.6; 95% CI: 1.6, 7.9; p= 0.002), use of allograft (OR = 3.3; 95% CI: 1.5, 7.4; p= 0.003), and HE≥5 degrees (OR = 2.12; 95% CI: 1.1, 4.7; p= 0.03). </p> </div><div class="section"> <a class="named-anchor" id="S6"> <!-- named anchor --> </a> <h5 class="section-title" id="d514625e112">Conclusion</h5> <p id="P6">This study found that preoperative physiologic passive knee hyperextension greater than or equal to 5 degrees is present in 1/3 of patients who undergo revision ACLR. HE≥5 was found to be an independent significant predictor of graft failure after revision ACLR with a &gt;2X odds ratio) of subsequent graft rupture in revision ACL surgery. </p> </div><div class="section"> <a class="named-anchor" id="S7"> <!-- named anchor --> </a> <h5 class="section-title" id="d514625e117">Clinical Relevance</h5> <p id="P7">Future study of these variables is warranted, and reports on ACL reconstruction results should separately evaluate the group of knees with HE≥5. </p> </div>