# Survival Analysis of ACL Graft and Contralateral ACL Ruptures in Patients Younger Than 18 Years

## TL;DR

This study finds that young patients who undergo ACL reconstruction face a high risk of future ACL injuries, with the risk increasing over time, especially in males.

## Contribution

The study provides the largest and longest follow-up analysis of ACL graft and contralateral rupture rates in patients under 18 years old.

## Key findings

- Cumulative graft rupture rates reached 22% at 10 years, while contralateral ACL rupture rates reached 33%.
- Males had significantly higher graft rupture rates than females, and their risk of contralateral rupture increased after 5 years.
- Females with smaller graft diameters (<7 mm) had higher graft rupture rates.

## Abstract

Although high rates of graft and contralateral anterior cruciate ligament (ACL) ruptures have been reported in younger patients after ACL reconstruction (ACLR), recent evidence suggests that previously reported crude event rates underestimate the actual event risk.

To report rates of graft and contralateral ACL rupture after ACLR in a large series of younger patients using survival analysis.

Cohort study; Level of evidence, 3.

Patients aged <18 years at the time of primary ACLR were identified from a single-surgeon database over 12 years ending January 2018. Patients with a previous contralateral ACL rupture or bilateral ACL ruptures were excluded. Overall, 388 patients (204 males, 184 females) were included in the final dataset. Bespoke survey data and clinic follow-up data were used to record graft rupture and contralateral ACL rupture events. Rates of graft and contralateral ACL rupture were calculated using Kaplan-Meier survival analysis. Log-rank tests were used to compare survival functions between several subgroups.

According to Kaplan-Meier survival analysis, the cumulative rates at 2, 5, and 10 years for graft rupture were 11%, 17%, and 22%, and the cumulative rates for contralateral ACL injury were 7%, 19%, and 33%. Males had significantly greater rates of graft rupture than females throughout a 10-year follow-up period (P < .001). Contralateral ACL rupture survival functions were not significantly different between the sexes, although rates were higher in females until 5 years postoperatively, after which contralateral ACL ruptures increased in males, with a cumulative rate of 39% at 10 years compared with 29% for females. Survival rates did not vary between different age groups (<16 vs ≥16 years), but females with a graft diameter of <7 mm on the femoral side had significantly greater graft rupture rates than females with grafts ≥7 mm (P = .04).

The present study is one of the largest consecutive series of younger patients, with one of the longest follow-up periods, reporting a high risk for a second ACL injury. Over time, the cumulative risk for contralateral ACL rupture was higher than for graft rupture. In males, the risk for contralateral ACL rupture continued to increase after 5 years.