Commentary & Perspective by
Thomas K. Fehring, MD*,
Charlotte Orthopaedic Specialists, Charlotte, North Carolina
Many previous studies on the subject of closed suction drainage for hip and knee arthroplasty have been compromised by poor trial methodology and inadequate reporting of outcomes. I would agree with the conclusion of Parker et al. in the abstract of their paper that additional randomized trials with use of larger numbers of patients are indicated before the absence of any benefit for the use of drains can be proved.
I would also agree with the authors that the primary outcome measure for this investigation should be the occurrence of wound infection, but the authors admittedly included studies that may have underreported this complication. Follow-up in these studies was often limited to the time of hospital discharge and thus may have resulted in underreporting of wound infection and reoperation. Such deficiencies are not unique to this particular meta-analysis. The ultimate quality of a meta-analysis depends on the quality of the primary studies on which it is based. The authors have included in their meta-analysis many randomized studies with poor methodology ratings. In a review of meta-analysis in orthopedic surgery, Bhandari et al. found that 88% of the meta-analyses reviewed had methodological flaws that could limit their validity1.
Another major concern regarding the authors' conclusions is the lack of a power analysis. Without performing this analysis, one risks the possibility of making a Type-2 error. A Type-2 error results when the p value fails to reach statistical significance even though the underlying groups are truly distinct2. Pooled results for all studies showed a wound infection rate of 1.6% (twenty-nine) of 1775 wounds treated with a drain compared with 2.4% (forty-two) of 1765 wounds treated without a drain. This difference was not significant. However, without knowing the statistical power, the reader cannot determine if this sample size is adequate to make the claim that there was no difference between the two groups with regard to infection following elective hip and knee replacement.
It certainly would be beneficial to know whether the use of drains is necessary in elective hip and knee replacement. Unfortunately, because of the admitted methodological flaws in the primary articles that were the basis of the meta-analysis and because of the lack of a power analysis, this study does not answer the question.
*The author did not receive grants or outside funding in support of his research or preparation of this manuscript. He did not receive payments or other benefits or a commitment or agreement to provide such benefits from a commercial entity. No commercial entity paid or directed, or agreed to pay or direct, any benefits to any research fund, foundation, educational institution, or other charitable or nonprofit organization with which the author is affiliated or associated.
1. Bhandari M, Morrow F, Kulkarni AV, Tornetta P 3rd. Meta-analyses in orthopaedic surgery. A systematic review of their methodologies. J Bone Joint Surg Am. 2001;83:15-24.
2. Freedman KB, Bernstein J. Sample size and statistical power in clinical orthopaedic research. J Bone Joint Surg Am. 1999;81:1454-60.