What's all that noise? The effect of co-morbidity on health outcome questionnaire results after knee arthroplasty.
BACKGROUND
We modified the Charnley Classification for hips to facilitate its use with knee arthroplasty patients and investigated what affect the different classes of co-morbidity had on the results of a spectrum of outcome questionnaires.


METHODS
3600 patients from the Swedish Knee Arthroplasty Registry were surveyed by post with a variety of questionnaires ranging from multiple-item general health, to a single-item knee arthroplasty specific questionnaire. All patients also completed a co-morbidity questionnaire, from which a modified Charnley Classification was generated for each patient. We then investigated the correlation and relationship between the results of the questionnaires and the different classes of co-morbidity.


RESULTS
The results of the questionnaires tested varied significantly by Charnley Class, regardless of the specificity of the questionnaire used.


CONCLUSIONS
We suggest that co-morbidity should be taken into account in outcome studies utilizing general health or disease/site specific questionnaires.
Dunbar
Michael J
MJ
Department of Orthopaedics, Lund University Hospital, SE-221 85 Lund, Sweden. Michael.dunbar@ort.lu.se
Robertsson
Otto
O
Ryd
Leif
L
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D015897:Comorbidity; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D020370:Osteoarthritis, Knee / Q000453:epidemiology* / Q000601:surgery; D012042:Registries; D011795:Surveys and Questionnaires; D013548:Sweden / Q000453:epidemiology; D016896:Treatment Outcome