BackgroundMedical litigation resulting from medical errors has a negative impact on health economics for both patients and medical practitioners. In medical litigation involving orthopedic surgeons, we aimed to identify factors contributing to plaintiff victory (orthopedic surgeon loss) through a comprehensive assessment. MethodsThis retrospective study included 166 litigation claims against orthopedic surgeons using a litigation database in Japan. We evaluated the sex and age of the patient (plaintiff), initial diagnosis, diagnostic error, system error, the time and place of each claim that led to malpractice litigation, the institution's size, and clinical outcomes. The main outcome was the litigation outcome (acceptance or rejection) in the final judgment. Acceptance meant that the orthopedic surgeon lost the malpractice lawsuit. We conducted multivariable logistic regression analyses to examine the association of factors with an accepted claim. ResultsThe median age of the patients was 42 years, and 65.7% were male. The litigation outcome of 85 (51.2%) claims was acceptance. The adjusted median indemnity paid was $151,818. The multivariable analysis showed that diagnostic error, system error, sequelae, inadequate medical procedure, and follow-up observation were significantly associated with the orthopedic surgeon losing the lawsuit. In particular, claims involving diagnostic errors were more likely to be acceptance claims, in which the orthopedic surgeon lost (adjusted odds ratio 16.7, 95% confidence intervals: 4.7 to 58.0, p < 0.001). All of the claims in which the orthopedic surgeon lost were associated with a diagnostic or system error, with the most common one being system error. ConclusionsSystem errors and diagnostic errors were significantly associated with acceptance claims (orthopedic surgeon losses). Since these are modifiable factors, it is necessary to take measures not only for individual physicians but also for the overall medical management system to enhance patient safety and reduce the litigation risk of orthopedic surgeons.