[Postoperative Dissociation after Knee Replacement and its Influence on the Course of Pain]

Even after successful knee replacement, one in 5 patients complains of chronic pain. Previous studies suggest that surgical interventions trigger postoperative traumatic stress in some patients. The aim of this explorative study is to investigate whether postoperative dissociation occurs as a manifestation of postoperative traumatic stress after total knee replacement. In addition, it should be investigated whether these patients have more chronic postoperative pain 1 year postoperatively and to what extent the course of pain differs from the other patients.

201 Patients who underwent primary knee TEP were studied. They answered questionnaires on knee pain (WOMAC) and dissociation (FDS-20) at 3 measurement points: 1 day preoperatively (T1), 10 weeks postoperatively (T2) and 1 year postoperatively (T3).

Data from 145 patients could be analyzed. The incidence for postoperative dissociation is 8.3%. Not only do patients with postoperative dissociation report more chronic postoperative pain after 1 year (p=0,016), but also their postoperative pain levels decreases less than in the patients without postoperative dissociation (p=0,025).

The findings provide evidence that postoperative dissociation occurs as a manifestation of postoperative traumatic stress after total knee replacement. Even if dissociation seems to be a defense mechanism for the regulation of overstraining affects in the short term, it is associated with more chronic postoperative pain in the long term. Furthermore, the patients with postoperative dissociation benefit less in a 1-year follow-up from total knee replacement in terms of pain reduction.

Strategies to reduce dissociation could lead to better results after knee TEP implementation and should be investigated in future intervention studies.