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Bone & Joint Research
Vol. 3, Issue 11 | Pages 317 - 320
1 Nov 2014
Statistical consequences of using bone mineral density to pair cadaver femurs in comparative ex vivo hip fracture studies
Basso T Klaksvik J Foss OA
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Objective

In ex vivo hip fracture studies femoral pairs are split to create two comparable test groups. When more than two groups are required, or if paired femurs cannot be obtained, group allocation according to bone mineral density (BMD) is sometimes performed. In this statistical experiment we explore how this affects experimental results and sample size considerations.

Methods

In a hip fracture experiment, nine pairs of human cadaver femurs were tested in a paired study design. The femurs were then re-matched according to BMD, creating two new test groups. Intra-pair variance and paired correlations in fixation stability were calculated. A hypothetical power analysis was then performed to explore the required sample size for the two types of group allocation.