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Dear Editor,
I read, initially with interest and then disappointment, the review article on minimally invasive (MIS) hip replacements by Smith et al. [1]. There are a number of methodological flaws that are irksome, and two duplications of studies that are not acceptable.
First, to group all MIS approaches together in order to pool data and make comparisons is unsound. Differences in technique (e.g. between the mini-anterior, mini-posterior, mini-anterolateral and two-incision approaches) are significant. Pooling data is therefore not appropriate.
Second, to include non-randomised studies may outwardly increase power, but simply dilutes the results.
Finally, the authors have taken inadequate care in researching their included studies, and duplicated the results of two studies: the group of Bennett et al. [2] is a cohort of Ogonda’s group [3], and Sculco et al. (second study) [4] is a description of Chimento’s group [5].
Meta-analyses are important ways of pooling data to increase power, especially in orthopaedics where all too often studies are underpowered. But, they are not as robust a tool as might be anticipated, and data entry must be handled with care and respect. The old adage of “garbage in, garbage out” springs to mind [6].
References
Smith TO, Blake V, Hing CB (2010) Minimally invasive versus conventional exposure for total hip arthroplasty: a systematic review and meta-analysis of clinical and radiological outcomes. Int Orthop. doi:10.1007/s00264-010-1075-8
Bennett D, Ogonda L, Elliott D, Humphreys L, Lawlor M, Beverland D (2007) Comparison of immediate postoperative walking ability in patients receiving minimally invasive and standard-incision hip arthroplasty: a prospective blinded study. J Arthroplasty 22:490–495
Ogonda L, Wilson R, Archbold P, Lawlor M, Humphreys P, O'Brien S et al (2005) A minimal-incision technique in total hip arthroplasty does not improve early postoperative outcomes. A prospective, randomized, controlled trial. J Bone Joint Surg Am 87-A:701–710
Sculco TP, Jordan LC, Walter WL (2004) Minimally invasive total hip arthroplasty: the Hospital for Special Surgery experience. Orthop Clin North Am 35:137–142
Chimento GF, Pavone V, Sharrock N, Kahn B, Cahill J, Sculco T (2005) Minimally invasive total hip arthroplasty: a prospective randomized study. J Arthroplasty 20:139–144
Egger M, Smith GD, Sterne JA (2001) Uses and abuses of meta-analysis. Clin Med 1:478–484
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Khan, R.J.K. Comments on Smith et al.: Minimally invasive versus conventional exposure for total hip arthroplasty: a systematic review and meta-analysis of clinical and radiological outcomes. International Orthopaedics (SICOT) 35, 299 (2011). https://doi.org/10.1007/s00264-010-1170-x
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DOI: https://doi.org/10.1007/s00264-010-1170-x