The Implications of Inaccuracy: Comparison of Coding in Heterotopic Ossification and Associated Trauma

Retrospective studies using large databases serve a major purpose in providing evidence in the current literature. However, the quality of medical coding is highly variable. This retrospective cohort study aimed to evaluate the documentation regarding the diagnosis of heterotopic ossification (HO) and the implications it may have for conducting retrospective research using electronic medical records (EMRs). A retrospective chart review using the EMR was performed to identify all patients with a diagnosis of HO within 7 university-affiliated hospital facilities. A limited data set request was conducted for all patients with HO-specific International Classification of Diseases, Ninth Revision (ICD-9) codes and additional nonspecific musculoskeletal codes to capture patients with HO who were improperly coded. A total of 522 patients were identified-26 patients with specific HO codes and 496 patients with nonspecific codes. Imaging and clinical notes were inspected for evidence and location of HO, and histories were reviewed for traumatic injury mechanism. Two-thirds of the patients with HO were discovered by reviewing miscellaneous musculoskeletal ICD-9 codes. Thirty-eight percent of the patients with an HO-specific ICD-9 code had no evidence of HO in their EMR. Thirty-three patients had a clinical history of a traumatic injury preceding HO formation, but only 16 of the 33 had documented ICD-9 codes for the injury. The utility of databases in retrospective research is dependent on the integrity of the coding. This study questions the use of retrospective reviews for patients with uncommon diagnoses and shows how painstaking verification may be necessary to ensure that research conclusions are based on accurate data.