Influence of the surgeon's instruction on postoperative joint replacement disability when measured by the Short Form 36: Comment on the article by FitzGerald et al


To the Editor:

The recent article by FitzGerald et al (FitzGerald JD, Orav EJ, Lee TH, Marcantonio ER, Poss R, Goldman L, et al. Patient quality of life during the 12 months following joint replacement surgery. Arthritis Rheum 2004;51:100–9), is important in increasing our understanding of the postoperative phase of joint replacement.

I was surprised to read that in spite of a dramatic improvement in pain at 1 month, physical function was found to have deteriorated. When the Short Form 36 questionnaire was completed at 6 months, function had considerably improved. This result is not what one would expect intuitively. My experience with post-joint replacement patients coming to their first followup appointment is that they arrive carrying rather than using their crutches, and they are trying to remember the list of things they have been advised to avoid during their postoperative period (such as avoiding crossing their legs, having sex, or driving).

In the study by FitzGerald et al, physical function was measured by a questionnaire rather than by direct testing. I wonder if the apparent reduction in physical function at 1 month is due to the questionnaire reflecting the doctor's postoperative instructions and the patient's wish to be seen as compliant, rather than a true reduction in function. The physical limitations imposed by the surgeon to safeguard the postoperative result will themselves result in reduced physical function when measured by a questionnaire, although we all know how patients like to please by giving the answers they believe doctors want to hear. The patient would not want to tell us they have been doing many activities that they believe to be forbidden.

Therefore, I suspect that this apparent postoperative reduction in physical function is not a true reflection of the patients' physical function, but rather a result of using a questionnaire rather than direct testing as the measurement tool. Although questionnaires are a simple method of gathering information, it is important to remember that they can be influenced by extraneous factors and can sometimes give misleading results.

Jeremy G. Jones MD*, * Ysbyty Gwynedd, Bangor, UK.