Trisomy 21 and Patellar Femoral Instability in a Pediatric Population: Results From 53,800 Patients.

BACKGROUND: Patellofemoral instability (PFI) commonly occurs in pediatric patients with Trisomy 21 (T21). Reported prevalence ranges from 1.5% to over 20%. This study establishes incidence and prevalence among tens of thousands of T21 patients and compares rates of surgical intervention with a matched non-T21 cohort.

METHODS: We conducted a retrospective analysis using the TriNetX Research USA Minimal Date Shift network, which includes de-identified electronic health records from 59 healthcare organizations. Patients with T21 and PFI (ICD-10 code S83.00 or M22.1) diagnosed at or before age 19 were included. We evaluated rates of surgical intervention for PFI using CPT codes for patellofemoral reconstruction procedures in T21 patients and compared them to an age, sex, race, and ethnicity-matched non-T21 patients with PFI. The annual point prevalence of PFI in Down syndrome patients was also calculated in a separate cohort from 2017 to 2024.

RESULTS: Among 53,800 patients with T21, the annual prevalence of PFI increased from 0.54% in 2017 to 0.81% in 2024. Females exhibited a higher prevalence than males (0.97% vs. 0.67% in 2024). The mean age at initial PFI diagnosis among patients with T21 was 11.1±4.7 years. Following 1:1 propensity-score matching, 18.7% (65/347) of patients with T21 and PFI underwent surgical treatment compared with 10.7% (37/347) of matched patients without T21 (RR, 1.76; 95% CI, 1.21-2.56). Kaplan-Meier analysis demonstrated no statistically significant difference in time from PFI diagnosis to surgery between matched cohorts (log-rank P=0.054; HR, 1.49; 95% CI, 0.99-2.23).

CONCLUSIONS: This is the first prevalence analysis of PFI in tens of thousands of children with T21. The findings reveal lower prevalence than previously reported, but a higher likelihood of surgical treatment compared with non-T21 peers. These results underscore the need to better understand how the current treatment strategies for PFI can affect this population and stress the importance of longitudinal monitoring of PFI in T21 patients.

LEVEL OF EVIDENCE: Level III.