Influence of somatization dysfunction and depressive symptoms on the course of pain within the first year after uncomplicated total knee replacement (TKR), a prospective study

AIMS AND OBJECTIVES: The implantation of a bicondylar knee implant is one of the most common orthopedic surgeries performed in Germany. However, it has been shown that 10 to 25% of the patients are not satisfied with the result. Purpose of this study was to evaluate the effect of depressive symptoms and somatization on the outcome after total knee replacement (TKR). MATERIALS AND METHODS: In 2012 and 2013 a total of 138 patients out of 150 were enrolled in this prospective study. Preoperatively depressive symptoms were assessed with the patient health questionnaire 9 (PHQ-9) and somatization was assessed with the PHQ-15. Primary outcome measure was the self-assessed knee function evaluated with the "knee osteoarthritis outcome score" (KOOS) and pain measured with a numerical rating scale (NRS). Secondary outcome measures were the KOOS subscales and the patient satisfaction. Group differences were tested by the independent t-test and the influence of other co-factors was checked with the univariate variance-analysis. RESULTS: At 6 and 12 months postoperatively patients with a PHQ-9 of more than 10 points had significant higher pain score at rest and daily living activities. Somatization assessed with the PHQ-15 had a significant effect on pain at rest and pain at daily living activities at 6 and 12 months postoperatively. Both factors, PHQ-9 and PHQ-15 had also a significant effect on KOOS outcome and patient satisfaction. CONCLUSION: Psychopathological factors such as depressive symptoms and somatization have an impact on outcome after TKR. Preoperative screening for psychopathological conditions could help to improve patient selection for TKR.