The Degree of Knee Extension Does Not Affect Postoperative Stability or Subsequent Graft Tear Rate after Anterior Cruciate Ligament Reconstruction with Patellar Tendon Autograft

OBJECTIVES: To compare graft tear and failure rates and subjective scores between patients of varying degrees of knee extension after anterior cruciate ligament (ACL) reconstruction with patellar tendon autograft. METHODS: Of 2329 patients who underwent ACL reconstruction with patellar tendon autograft between 1998 and 2008, 625 patients met the inclusion criteria of having primary ACL surgery, no bilateral ACL injuries, no existing osteoarthritis, and having either 6⁰ or more of knee hyperextension before and after surgery (Group A; n=318; mean 8⁰ + 2⁰, range 6⁰ to 15⁰) or 3⁰ or less of knee hyperextension before and after surgery (Group B; n=307; mean 0⁰ + 3⁰, range 3⁰ hyperextension to -4⁰ extension). As part prospective follow-up, patients were evaluated with KT-1000 arthrometer for objective stability, range of motion measurements, and subjective follow-up with International Knee Documentation Committee (IKDC), Cincinnati Knee Ratings Scale (CKRS), and Activity Rating surveys. Subsequent graft tear related to specific injury within 5 years of surgery was recorded. Graft failure was defined as a KT-1000 manual maximum difference between knees of > 5mm. RESULTS: Follow-up was obtained from 278 (87%) in Group A and 275 (90%) in Group B at a mean of 4.1 + 1.1 years after surgery. The KT1000 arthrometer manual/maximum difference between knees was 2.0 + 1.4 in Group A and 2.1 + 1.6 in Group B (p=.701). Within 5 years after surgery, subsequent ACL graft tear/failure occurred in 22 patients (6.9%) in Group A and 30 patients (9.8%) in Group B (p=.246.) Further sub-analysis of Group A showed that the graft tear/failure rate was 6 of 81 (7.4%) for patients with ≥ 10⁰ of hyperextension versus 16 of 237 (6.8%) for patients with 6⁰ to 9⁰ of hyperextension. The percentage of patients who participated in jumping and pivoting sports before surgery was 85% in Group A and 86% in the Group B before surgery and 87% in Group A and 90% in Group B after surgery. The mean activity rating score was 8.4 + 1.1 in both groups after surgery. There was no statistically significant difference in the IKDC giveway or CKRS stability scores between groups after surgery (p=.174 and p=.107 respectively). Similarly, there was no difference in IKDC total score or CKRS total score between groups after surgery (p=.933 and p=.155 respectively). CONCLUSION: Obtaining full hyperextension that is anatomically normal for most patients does not affect postoperative objective stability, ACL graft tear/failure rates, or subjective scores after ACL reconstruction with patellar tendon autograft.