Background: The aim of this study was to perform a systematic review and meta-analysis of the literature regarding the incidence of delirium following orthopedic surgery.

Methods: Relevant papers were sourced from online databases and gray literature. Included studies used a validated diagnostic method to measure the incidence of delirium in a prospective sample of adult/elderly orthopedic patients. Data were subject to meta-analysis after stratification by type of surgery (elective v. emergency) and inclusion/exclusion of pre-existing cognitive impairment. A funnel plot assessed for publication bias.

Results: 26 publications reported an incidence of postoperative delirium of 4–53.3% in hip fracture samples and 3.6–28.3% in elective samples. Significant heterogeneity was evident, and this persisted despite stratification. Hip fracture was associated with a higher risk of delirium than elective surgery both when the cognitively impaired were included in the sample (random effects pooled estimate = 21.7% [95% CI = 14.6–28.8] vs. 12.1% [95% CI = 9.6–14.6]), and when the cognitively impaired were excluded (random effects pooled estimate = 25% [95% CI = 15.7–34.7] vs. 8.8% [95% CI = 4.1–13.6]). The funnel plot showed a deficit of small studies showing low risk and large studies showing high risk. In eight hip fracture studies, the proportion of delirium cases with a preoperative onset ranged from 34 to 92%.

Conclusions: Delirium occurs more commonly with hip fracture than elective surgery, and frequently has a preoperative onset when associated with trauma. Recommendations are made with the aim of standardizing future research in order to further explore and reduce the heterogeneity and possible publication bias observed.