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Keep calm and carry on testing: a substantive reanalysis and critique of ‘what is the evidence for and validity of return-to-sport testing after anterior cruciate ligament reconstruction surgery? A systematic review and meta-analysis’
  1. Jacob John Capin1,
  2. Lynn Snyder-Mackler2,
  3. May Arna Risberg3,4,
  4. Hege Grindem3,5,6
  1. 1 Biomechanics and Movement Science, Physical Therapy, University of Delaware, Newark, Delaware, USA
  2. 2 Physical Therapy, Biomechanics and Movement Science, Biomedical Engineering, Delaware Rehabilitation Institute, University of Delaware, Newark, Delaware, USA
  3. 3 Department of Sport Medicine, Norwegian School of Sport Sciences, Oslo, Norway
  4. 4 Division of Orthopaedic Surgery, Oslo University Hospital, Oslo, Norway
  5. 5 Oslo Sport Trauma Research Center, Norwegian School of Sport Sciences, Oslo, Norway
  6. 6 Stockholm Sports Trauma Research Center, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden
  1. Correspondence to Dr Lynn Snyder-Mackler; smack{at}

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Clinicians rely on rigorous systematic reviews to guide practice. We therefore suspect many clinicians will note the results of the 2019 systematic review and meta-analysis by Webster and Hewett, ‘What is the Evidence for and Validity of Return-to-Sport Testing after Anterior Cruciate Ligament Reconstruction Surgery? A Systematic Review and Meta-Analysis’.1 We agree that it is important to evaluate the association between return-to-sport (RTS) test batteries and outcomes after ACL reconstruction. The third review question in Webster and Hewett (2019) is particularly pertinent: ‘Is passing RTS test batteries associated with reduced rates of subsequent knee injury (all knee injuries and ACL injury)?’1 We are authors of several of the original data papers cited in the systematic review, and we are concerned about the study methodology and its conclusions. We highlight major problems with including two studies and present revised analyses that demonstrate the impact these studies had on the conclusions.

Methodological concerns

First, we question the validity of pooling studies with substantial clinical and methodological diversity.2 The meta-analysis combined studies where only some athletes returned to sport3 4 and studies where all, or mostly all, returned to sport;5–7 studies with skeletally immature patients7 and studies with elite athletes;6 and studies where substantially different RTS test batteries were used. Our second concern is that Webster and Hewett1 did not assess risk of bias, a fundamental precept of systematic review methodology clearly stated in the PRISMA reporting guideline.8–10 Assessment of study quality (as performed by Webster and Hewett1) does not quantify risk of bias.11 A risk of bias assessment identifies factors within studies that can skew results, and these factors must be considered carefully in the decision to pool data and in the conclusion. Important bias domains for review questions 2 and 3 include …

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