Structural Changes in the Brain prior to and following Knee Joint Replacement

G Lewis*, R Parker, S Sharma, D Rice, P McNair
* Health and Rehabilitation Research Institute, Auckland University of Technology
** Department of Physiotherapy, Waitakere Hospital, Waitemata DHB
*** Waitemata Pain Service, North Shore Hospital, Waitemata DHB

Introduction: Previous studies utilising magnetic resonance imaging (MRI) techniques have indicated structural alterations in both grey and white matter in people with chronic pain conditions. Few studies have examined how brain structure is altered following treatment of chronic pain, and how any such alterations are related to changes in pain.

Aim: The goal of the study was to investigate grey and white matter structure and function in people with knee osteoarthritis (OA) before and after joint replacement surgery. We hypothesised that neuromatrix regions would be altered prior to surgery but would return to normal following joint replacement.

Methods: MRI scans were undertaken on 29 people scheduled to have a knee joint replacement (PREOP) and 18 healthy controls (CON). The scans were repeated 6 months following surgery (POSTOP). Scans included the analysis of morphometry of specific grey matter regions, white matter tract integrity, metabolite concentration, and functional response to nociceptive stimulation.

Results: Grey matter volume was reduced in the nucleus accumbens, amygdala and primary somatosensory cortex at PREOP compared to CON. Following surgery, there was an increase in grey matter volume in the amygdala, periaqueductal grey, and hippocampus, while there was a reduction in the primary somatosensory cortex. There was some evidence of reduced white matter tract integrity in the midbrain at PREOP, while integrity was increased at POSTOP compared to PREOP in a large region of the brainstem. None of these alterations were related to changes in pain following surgery. There were no differences in metabolite concentration or the functional response to nociceptive stimulation.

Conclusions: We provide evidence of alterations in grey and white matter regions of the brain associated with nociception in people with chronic knee OA, and further adaptations that occur following pain relief from joint replacement. The clinical importance of these structural brain alterations needs further investigation.