2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


Patient and Operative Risk Factors for Subsequent Total Knee Arthroplasty Following Primary Anterior Cruciate Ligament Reconstruction

David Y. Ding, MD, San Francisco, ca UNITED STATES
Heather Prentice, PhD, San Diego, CA UNITED STATES
Chelsea Reyes UNITED STATES
Elizabeth W. Paxton, PhD, El Cajon, CA UNITED STATES
Gregory B. Maletis, MD, Baldwin Park, CA UNITED STATES
Foster Chen, MD, Redwood City, CA UNITED STATES

Kaiser Permanente, San Diego, CA, UNITED STATES

FDA Status Not Applicable

Summary

Patients who underwent ACLR with allograft compared to autograft had a 2-times higher risk of undergoing a TKA during follow-up, and additional risk factors for TKA after ACLR included patient age, female gender, concomitant chondral injury, and ipsilateral reoperation or contralateral surgery during follow-up.

Abstract

Background

Patients who undergo anterior cruciate ligament reconstruction (ACLR) are at a higher risk of undergoing total knee arthroplasty (TKA) and are at risk earlier than those from a general population. As ACLR patients become older, and as ACLR becomes more prevalent in the older athlete, the rates of TKA after ACLR will only increase. We aim to determine the incidence of TKA following ACLR by patient age at the time of ACLR and graft selection, as well as evaluate the risk factors for TKA after ACLR.

Methods

Data from a US healthcare system’s ACLR registry was used to conduct a cohort study. Primary ACLR patients were identified (2005-2022). Patient factors considered included age, body mass index (BMI), gender, race/ethnicity, smoking status, ASA classification, activity at the time of injury, and medical comorbidities. Time from injury to ACLR, concomitant meniscal or chondral injuries, multi-ligament injury, graft type, and drilling technique were procedure factors evaluated. Postoperative factors included revision surgery, ipsilateral reoperation, and contralateral operation during follow-up. The outcome of interest was a subsequent TKA. Patients were followed until the outcome of interest unless censored for membership disenrollment, death, or December 31, 2022 (the study end date). Multivariable Cox proportional hazards regression was used to determine factors associated with TKA following ACLR using p<0.05 as the threshold for statistical significance.

Results

The study sample included 52,222 primary ACLR. The mean age was 28.6 years, and more patients were male (60.2%). When considering age at the time of ACLR, the 15-year cumulative incidence of TKA after ACLR was 0.07% for those aged <30 years, 1.17% for those aged 30-39 years, 3.96% for those aged 40-49 years, 8.05% for those aged 50-59 years, and 22.53% for those aged ≥60 years. When considering graft used at ACLR, the 15-year cumulative incidence of TKA after ACLR was 3.15% for allograft, 0.36% for BPTB autograft, and 0.69% for hamstring autograft; it was 0.55% at 10-years follow-up for hybrid grafts (using an allograft and hamstring autograft) and 0.27% at 4-years for quadriceps tendon autograft.

Risk factors for TKA included increasing age compared to those <40 years (40-49 years: hazard ratio [HR]=7.85, 95% confidence interval [CI]=4.65-13.24; 50-59 years: HR=17.51, 95% CI=10.47-29.28; ≥60 years: HR=50.41, 95% CI=25.52-99.60), female gender (HR=1.48, 95% CI=1.10-1.97), a history of other neurological disorders at the time of ACLR (HR=5.98, 95% CI=2.56-13.98), chondral injuries reported during the ACLR (HR=1.61, 95% CI=1.17-2.23), and allograft selection (HR=2.24, 95% CI=1.19-4.20). Ipsilateral reoperation (HR=2.46, 95% CI=1.80-3.35) and contralateral surgery (HR=2.55, 95% CI=1.80-3.61) during follow-up were both risk factors for TKA.

Conclusions

The 15-year cumulative risk of TKA in patients who were ≥60-years old when undergoing their ACLR was 23%. Patients who underwent ACLR with allograft had a 2-times higher risk of undergoing a TKA. Age, female gender, concomitant chondral injury, and ipsilateral reoperation or contralateral surgery during follow-up were additional risk factors for TKA in patients who have undergone prior ACLR.