The prognosis and predictors of sports function and activity at minimum 6 years after anterior cruciate ligament reconstruction: a population cohort study

Abstract

Background: The predictors of anterior cruciate ligament reconstruction (ACLR) outcome at 6 years as measured by validated patient-based outcome instruments are unknown.

Hypothesis: Certain variables evaluated at the time of ACLR will predict return to sports function (as measured by the International Knee Documentation Committee [IKDC] questionnaire and the Knee injury and Osteoarthritis Outcome Score [KOOS] Sports and Recreation subscale), knee-related quality of life (KOOS Knee Related Quality of Life subscale), and activity level (Marx Activity Scale). Potential predictor variables include demographic factors, surgical technique and graft choice for ACLR, and intra-articular injuries and treatment.

Study design: Cohort study; Level of evidence, 2.

Methods: All patients with unilateral ACLRs from 2002 currently enrolled in the MOON (Multicenter Orthopaedic Outcomes Network) cohort were evaluated. Patients completed the validated outcome instruments preoperatively. Physicians documented intra-articular pathologic abnormalities, treatment, and surgical techniques used at the time of surgery. At 2 and 6 years postoperatively, patients completed the same validated outcome instruments.

Results: Follow-up was obtained at 2 years (88%) and at 6 years (84%). The cohort was 57% male with a median age of 23 years at enrollment. The ability to perform sports function was maintained at 6 years, but the Marx activity level continued to decline from baseline. Revision ACLR and use of allograft predicted worse outcomes on the IKDC and both KOOS subscales. Lateral meniscus treatment, smoking status, and body mass index at baseline were each predictors on 2 of 3 scales. The predictors of lower activity level were revision ACLR and female sex.

Conclusion: Six years after ACLR, patients could perform sports-related functions and maintain a high knee-related quality of life similar to their 2-year level, although their physical activity level (Marx) dropped over time. Choosing autograft rather than allograft, not smoking, and having normal body mass index are advised to improve long-term outcomes.

Figure 1

Flow Diagram of Study Cohort. All ACL reconstruction patients were enrolled during calendar year 2002. The follow-up for each time interval, either minimum of two or six years, for the validated patient-reported outcome questionnaires is indicated as returned. In addition, the lost-to-follow-up patients with known results (i.e. end points) such as death, subsequent total knee arthroplasty (TKA), and refusals are shown.

Figure 2

KOOS: Knee Related Quality of Life Results of Potential Predictor Variables (mean +/- 95% CI). For each potential predictor variable listed and the comparison, the change either positive (better outcome) or negative (worse outcome), is shown. Each result is the mean plus or minus the 95% confidence interval. A result is statistically significant if the 95% CI does not cross the zero line. A result is felt to be clinically meaningful if the mean is outside the red and green lines. These lines represent the positive (green) and negative clinically meaningful difference based on development of outcome instruments.

Figure 3

KOOS: Knee Related Quality of Life Patient-Specific Results at Six Years. The nomogram is used to predict a patient-specific outcome score at six years based on summing the individual point total for each variable on the left. For each variable the patient’s result is indicated and the points based on the top point scale are recorded. Then the sum of points is placed on the total points line on the bottom. After the total points are marked, you read the outcome score predicted at six years below.