The geriatric orthopaedic population has a high prevalence of postoperative delirium with hip fracture repair having the highest incidence. The aim of this study was to identify whether surgical procedure is a risk factor for postoperative delirium in the elderly hip fracture population.
Ethical approval for this study (IRB-X) was provided by the Institutional Review Board of Johns Hopkins Medical Institutions, Baltimore, Maryland, USA (Chairperson Susan Bassett, PhD) on 15 September 2013. The dataset used for this analysis was our IRB-approved hip fracture database, which includes patients at least 65 years of age, as described previously.1 This dataset used mini-mental status exam (MMSE) and the confusion assessment method to test delirium preoperatively and mid-morning on postoperative day 2. Patients diagnosed with preoperative delirium were excluded.
Surgical procedure was categorised as arthroplasty (with or without cement), plate/screw or intramedullary nail (long or short). Perioperative predisposing factors for postoperative delirium were compared by surgical procedure using Chi-square analysis for categorical variables and analysis of variance for continuous variables. The univariate results were then used to guide the selection of logistic regression models to estimate the odds ratios (OR) of postoperative delirium associated with surgical procedure and their corresponding 95% confidence interval (CI), while adjusting for perioperative risk factors. A P value of 0.05 or less was considered statistically significant.
Data from 409 patients included arthroplasty (n = 177, 145 with cement and 32 without), plate/screw (n = 127) and intramedullary nail (n = 105). In logistic regression, previously identified perioperative risk factors for postoperative delirium remained highly significant (Table 1). These included male sex, age, preoperative cognitive impairment and perioperative blood transfusion. Arthroplasty with cement and screw/plate procedures were associated with significant higher odds of postoperative delirium, than intramedullary nail procedure (both P < 0.028), while cement-less arthroplasty was not (OR 1.78, P = 0.28).
The new potential postoperative delirium risk factor identified in this analysis is use of cement with arthroplasty. Arthroplasty carries a high rate of postoperative delirium, which has been associated with intraoperative cerebral fat embolism.2 Embolic events occur with both cement-less and cemented arthroplasty procedures, although the incidence is lower with cement-less arthroplasty.3 Bone cement implantation syndrome with its associated hypoxia and hypotension occurs in 20% of patients during arthroplasty for femoral neck fracture and could also provide a mechanism for postoperative delirium.4
Cemented prosthesis carries multiple benefits including reduced postoperative pain, and better mobility. Recent studies show a decreased need for revision arthroplasty with cemented implants when compared with cement-less arthroplasty.5 This is due to decreased implant loosening and a lower risk of peri-prosthetic re-fracture.6
Study limitations include confusion assessment method assessment on the second postoperative day only, which may have underdetected mild, transient delirium that occurred only on first postoperative day. Previous studies in hip fracture patients report that delirium severity peaks on day one postoperatively.7 Nonetheless, delirium episodes missed would have been mild. In addition, traditional risk factors such as preoperative depression, pain and duration of surgery were not assessed or not reported.7,8
In summary, this study is consistent with previous reports that identify male sex, age, preoperative cognitive impairment and perioperative blood transfusion, are important risk factors for postoperative delirium. In addition, we have identified use of cement as a potential surgical postoperative delirium risk factor. Future studies focused on detecting and limiting embolic events in arthroplasty with cement procedures for hip fracture repair may be important in decreasing postoperative delirium incidence.
Acknowledgements relating to this article
Assistance with the study: none.
Financial support and sponsorship: NIH R01AG033615; funding for statistical support is also received from the National Center for Research Resources (NCRR) and the National Center for Advancing Translational Sciences (NCATS) of the National Institutes of Health through Grant Numbers M01 RR02719, UL1 TR000424 and UL1 TR001079 and the MSTAR programme.
Conflicts of interest: none.
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