The Journal of Bone and Joint Surgery (American). 2006;88:41-45.
doi:10.2106/JBJS.E.00272
© 2006 The Journal of Bone and Joint Surgery, Inc.
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How Many Patients? How Many Limbs? Analysis of Patients or Limbs in the Orthopaedic Literature: A Systematic Review

Dianne Bryant, MSc, PhD1, Thomas C. Havey, BHSc2, Robin Roberts, MSc3 and Gordon Guyatt, MD, MSc4

1 Faculty of Health Sciences, The University of Western Ontario, Elborn College Room 1438, London, ON N6G 1H1, Canada. E-mail address: dianne.bryant{at}uwo.ca
2 Michael G. DeGroote Centre for Learning and Discovery, Room 3308, Faculty of Health Sciences, McMaster University, 1200 Main Street West, Hamilton, ON L8N 3Z5, Canada
3 Clinical Epidemiology and Biostatistics, Faculty of Health Sciences, McMaster University, Hamilton Civic Hospital Research Centre, Henderson General Hospital, 711 Concession Street, Hamilton, ON L8V 1C3, Canada. E-mail address for R. Roberts: robertsr{at}mcmaster.ca
4 Clinical Epidemiology and Biostatistics, Hamilton Health Sciences Center, Room 2C12, McMaster University, 1200 Main Street West, Hamilton, ON L8N 3Z5, Canada. E-mail address for G. Guyatt: guyatt{at}mcmaster.ca

Investigation performed at McMaster University, Hamilton, Ontario, Canada

The authors did not receive grants or outside funding in support of their research for or preparation of this manuscript. They 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 authors are affiliated or associated.

Background: Clinical studies assessing orthopaedic interventions often include data from two limbs or multiple joints within single individuals. Without appropriate design or statistical approaches to address within-individual correlations, this practice may contribute to false precision and possible bias in estimates of treatment effect. We conducted a systematic review of the orthopaedic literature to determine the frequency of inappropriate inclusion of nonindependent limb or joint observations in clinical studies.

Methods: We identified seven orthopaedic journals with high Science Citation Index impact factors and retrieved all clinical studies for 2003 for any intervention on any limb or joint.

Results: We identified 288 clinical studies, 143 of which involved two limbs or multiple joint observations from single individuals. These studies included nineteen randomized clinical trials (13%) fifty-eight two-group cohort studies (41%), and sixty-six one-group cohort studies (46%). Seventy-six (53%) of the 143 studies involved statistical comparisons between patient groups with use of tests of association, and an additional sixty studies (42%) presented estimates of proportions without statistical comparisons. Only sixteen of the seventy-six studies involving statistical comparisons involved the use of any technique or methodological approach to account for multiple, nonindependent observations. A median of approximately 13% of the patients in these studies contributed more than one observation. The median proportion of nonindependent observations to total observations (the unit of analysis) was approximately 23%.

Conclusions: Our findings suggest that a high proportion (42%) of clinical studies in high-impact-factor orthopaedic journals involve the inappropriate use of multiple observations from single individuals, potentially biasing results. Orthopaedic researchers should attend to this issue when reporting results.


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