Abstract
Purpose
Femoral nerve blockade (FNB) can provide prolonged postoperative analgesia and facilitate rehabilitation following major knee surgery while minimizing opioid-related adverse effects. However, anecdotal data have implicated FNB in post-operative falls, presumably due to a block-related reduction in quadriceps strength. Age, gender and knee replacement surgery have also been previously identified as risk factors for falls in the acute postoperative orthopaedic inpatient setting. We hypothesized that the use of FNB would be an independent predictor of an inpatient fall following total knee replacement (TKR).
Method
We examined a cohort of 2,197 patients who underwent TKR in a single academic institution between October 2003 and March 2010. The start date was based on the separate initiation of both a comprehensive regional anesthesia database and an orthopaedic ward Falls Surveillance Program. Patients undergoing revision TKR or unicompartmental arthroplasty were excluded. Age, simultaneous bilateral TKR, gender, body mass index (BMI), and various regional nerve blocks were considered predictors of post-operative falls in a logistic regression model. The database allowed resolution of the type (i.e. femoral, sciatic) and duration (i.e. single-bolus, indwelling continuous perineural catheter) of nerve blockade. Hospital-standard dosing and insertion techniques were employed.
Results
The total number of falls was 60 (rate 2.7%), 40 of which occurred within 48 hours of surgery. When compared to patients who did not fall, those who fell were significantly older (699 years vs 6611 years; p=0.03), obese [BMI >30kg/m2] (75% vs 59%; p=0.01) and had continuous catheter FNB (97% vs 86%; p=0.02). The odds ratio of having a fall was 1.04 (1.0–1.07; p=0.008) for each one-year increase in age above the mean age of 66 years, 2.4 (1.3–4.5; p=0.005) for a BMI >30kg/m2 and 4.4 (1.04–18.2; p=0.04) for continuous catheter FNB. Gender, simultaneous bilateral TKR, any sciatic nerve block or spinal anesthetic did not predict an increased risk of acute-care post-operative falls.
Conclusion
This is the first study to demonstrate an increased risk of post-operative falls in obese patients and with the use of continuous catheter FNB following TKR. Careful consideration of the use of continuous catheter FNB may be warranted in patients with additional risk factors for falls such as advanced age and obesity.
