ICD-10 codes do not accurately reflect ankle fracture injury patterns

To determine the accuracy of International Classification of Disease Version 10 (ICD-10) coding for ankle fracture injury patterns.

Retrospective cohort study PATIENTS: 97 adult patients with fractures about the ankle (rotational ankle fracture or distal tibia fracture) from 2016 to 2020, selected by stratified random sampling.

Assignment of an ICD-10 code representative of a rotational ankle fracture, pilon fracture, or unspecified fracture of the lower leg.

Injury radiographs were reviewed by three authors to determine the correct code. Agreement between the correct code and the electronic medical record (EMR) assigned code was determined using kappa's statistic in the aggregate as well as percent agreement, sensitivity, specificity, and positive predictive value (PPV) between individual codes.

59 of 97 cases (60.8%) demonstrated discordance between the existing EMR and surgeon-assigned codes. Aggregate agreement between all codes was fair (K = 0.26). Lateral malleolus fracture codes demonstrated the highest PPV (0.91, 95% CI 0.72-0.99), while the lowest PPV was found for "other fractures of the lower leg" (0.05, 95% CI 0.0-0.24) and "other fracture of the fibula" (0.0, 95% CI 0.0-0.15). Generalized "other fracture" codes comprised 45% of EMR codes compared to only 6% of assigned codes (p < 0.001). EMR codes were specific but not sensitive.

There is substantial discordance between existing EMR and surgeon-assigned ICD-10 codes for ankle fractures. Database research that relies on ICD-10 coding as a surrogate for primary clinical data should be interpreted with caution and institutions should make efforts to increase the accuracy of their coding.