title: A self-made, low-cost infrared system for evaluating the sciatic functional index in mice.
abstract: The sciatic functional index (SFI) is a popular parameter for peripheral nerve evaluation that relies on footprints obtained with ink and paper. Drawbacks include smearing artefacts and a lack of dynamic information during measurement. Modern applications use digitized systems that can deliver results with less analytical effort and fewer mice. However, the systems are expensive (€40,000). This study aimed to evaluate the applicability and precision of a self-made, low-cost infrared system for evaluating SFI in mice. Mice were subjected to unilateral sciatic nerve crush injury (crush group; n = 7) and sham operation (sham group; n = 4). They were evaluated on the day before surgery, the 2(nd), 4(th) and 6(th) days after injury, and then every day up to the 23(rd) day after injury. We compared two SFI evaluation methods, i.e., conventional ink-and-paper SFI (C-SFI) and our infrared system (I-SFI). Our apparatus visualized footprints with totally internally reflected infrared light (950 nm) and a camera that can only detect this wavelength. Additionally we performed an analysis with the ladder beam walking test (LBWT) as a reference test. I-SFI assessment reduced the standard deviation by about 33 percent, from 11.6 to 7.8, and cut the variance around the baseline to 21 percent. The system thus requires fewer measurement repetitions and fewer animals, and cuts the cost of keeping the animals. The apparatus cost €321 to build. Our results show that the process of obtaining the SFI can be made more precise via digitization with a self-made, low-cost infrared system.
authors.affiliation: Department of Plastic and Hand Surgery, University of Freiburg Medical Center, Freiburg, Germany.
authors.forename: Lukas
authors.initials: L
authors.lastname: Fricker
authors.affiliation: Department of Plastic and Hand Surgery, University of Freiburg Medical Center, Freiburg, Germany.
authors.forename: Vincenzo
authors.initials: V
authors.lastname: Penna
authors.affiliation: Department of Plastic and Hand Surgery, University of Freiburg Medical Center, Freiburg, Germany.
authors.forename: Florian
authors.initials: F
authors.lastname: Lampert
authors.affiliation: Department of Plastic and Hand Surgery, University of Freiburg Medical Center, Freiburg, Germany.
authors.forename: G Bjoern
authors.initials: GB
authors.lastname: Stark
authors.affiliation: Plastic and Reconstructive Surgery, Charité - Universitätsmedizin Berlin, Berlin, Germany.
authors.forename: Christian
authors.initials: C
authors.lastname: Witzel
authors.affiliation: Department of Plastic and Hand Surgery, University of Freiburg Medical Center, Freiburg, Germany.
authors.forename: Georgios
authors.identifier: 0000-0001-5679-7686
authors.initials: G
authors.lastname: Koulaxouzidis
keywords: crush; error rate; frustrated total internal reflection; infrared; ladder beam walking test; mouse; nerve regeneration; neural regeneration; peripheral nerve injury; sciatic nerve