Differences in Baseline Characteristics and Outcome Among Responders,Late Responders,and Never-Responders After Anterior Cruciate Ligament Reconstruction

Abstract

Background:

Loss to follow-up in registry studies might affect generalizability and interpretation of results.

Purpose:

To evaluate the effect of nonresponder bias in our anterior cruciate ligament (ACL) registry.

Study Design:

Case-control study; Level of evidence, 3.

Methods:

A total of 2042 patients with ACL reconstruction in the Hospital for Special Surgery ACL Registry between 2009 and 2013 were included in the study. Patients who completed the patient-reported outcome measures at 2 or 5 years were considered responders (n = 808). Baseline data and patient characteristics were compared between responders and nonresponders (n = 1234). Both responders and nonresponders were contacted and invited to complete the International Knee Documentation Committee (IKDC) and Marx scores electronically and respond to questions regarding return to sports and subsequent surgeries. Nonresponders who completed the questionnaires after reminders were considered late responders. The remaining nonresponders were considered never-responders. The late responders (n = 367) completed the questionnaires after a mean follow-up of 7.8 years (range, 6.7-9.6 years), while follow-up for the responders was 6.8 years (range, 5.0-9.7 years). Responders and late responders were then compared in terms of differences in IKDC and Marx scores from baseline to final follow-up.

Results:

Nonresponders were younger (28.5 vs 31.5 years; P < .001) and more often male (60% vs 53%; P = .003) compared with responders. Responders had a higher level of education and were more likely to be White (79% vs 74%; P = .04). There were no substantial differences in patient characteristics or baseline IKDC and Marx scores between the late responders and never-responders. There were no statistically significant differences in patient-reported outcomes, return to sports, or subsequent surgeries between responders and late responders at a mean follow-up time of 8.8 years (range, 6.7-9.7 years). Repeat email reminders and telephone calls increased response rate by 18% (from 40% to 58%).

Conclusion:

There was no difference in clinical outcome as evaluated using IKDC and Marx scores between responders and late responders.