Total knee replacement linked to cognitive decline in certain older patients, UF study finds

An interdisciplinary team of UF researchers have found in a recent study that following total knee replacement, 23 percent of patients 60 years and older suffered decline of activity in at least one of three brain networks investigated, each related to specific cognitive functions. Of these patients, 15 percent underwent a decline in all networks.

“We have the patient go through a scan in the MRI so we can look at how the brain (networks are) changed by the surgery,” said Mingzhou Ding, Ph.D., one of the study’s senior authors and distinguished professor in the J. Crayton Pruitt Family Department of Biomedical Engineering. “After the surgery, we found that these networks’ internal connections are declined, signifying a neural injury.”

Due to effects of anesthesia and major surgery, such as total knee replacement, older adults sometimes develop postoperative cognitive decline. However, it is not yet completely understood which patients will acquire this condition and which patients will not. With this study, UF researchers led by Catherine Price, Ph.D., associate professor of clinical and health psychology and anesthesiology, have begun to provide some answers.

Patients underwent functional MRI scanning both before and after surgery. “(Functional MRI) actually measures the blood oxygen level dependent (BOLD) responses, which varies to the level of neural activity in the brain,” said Haiqing Huang, Ph.D., one of the study’s lead authors and a graduate of the biomedical engineering program at UF. This technology allowed researchers to detect postoperative changes in activity throughout three brain networks.

Various preoperative measurements of the brain were also recorded so that researchers could learn whether specific markers exist that predict how the brain will respond after surgery. Of these measurements, processing speed, working memory, and ventricular volume correlated strongest with the severity of brain network connectivity decline.

“This finding suggests preoperative cognitive function and brain health status as important considerations for old adults who will be elected for total knee replacement surgery,” said Huang, now data manager for the University of Pittsburgh’s Brain Aging & Cognitive Health Lab.

Patients potentially at risk for cognitive decline after major surgery should be identified with predictive measurements and focus on improving brain function before going through with surgery to minimize injury, said Ding.

Engaging in mental and physical exercise might benefit older patients, in particular, said Huang. These activities may maintain brain function and decrease the risk of cognitive decline from surgery.

Patients were scanned just days after surgery in this study which means that preoperative measurements were only able to predict cognitive decline in the short term. Future experiments will build on this current study, monitoring patients at further time points, such as three months and one year, so that markers for long-term decline may be identified.

By Jonathan Griffin, BME Ph.D. student

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