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Viscoelastic Models for Needle Insertion in Peripheral Nerves - Study Results

Investigating the mechanical properties of needle insertions into peripheral nerves using a standard viscoelastic model. Results show correlation, force variations, and impact of needle design factors.

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Viscoelastic Models for Needle Insertion in Peripheral Nerves - Study Results

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  1. Characterizing mechanical properties of peripheral nerves during needle insertion, using the viscoelastic standard mechanical body model Ingólfur Pálsson Group 701 Department of Health Science and Technology

  2. Introduction to the problem • Insertion of multi-site neural recording electrodes into nerves, can result in the structural failure of the electrode. • Needle used to guide the electrode into the nerve. • Characterizing the mechanical properties of needle insertion into nerves, could help reduce trauma to the nerve. • Hoffman et. al has shown that dimple occurs in the rat brain during needle insertion. • Yoshida et. al has fitted a viscoelastic model (SMB-model) to needle insertions into rat brains. • Aim: Investigate if the SMB-model could be fitted to needle insertions into peripheral nerves. • Penetration force and dimple.

  3. Needles • The needles are used to penetrate the perineurium • The data recorded is used to measure the dimple and the mechanical properties of the needle insertion • Important factors of the needle design • Opening Angle • Needle Diameter

  4. SMB - model • Models viscoelastic properties of data • Must be verified by measuring a known viscoelastic material - Honey

  5. Results • The SMB-model was verified using a 200µm needle • The SMB-model did not fit the data of needle insertion into peripheral nerves, for any populations of needles. • χ2 and correlation between residuals test confirmed that the model did not fit. (χ2 = 1263.4±1099 (mean±std) > χ2005 =14.671

  6. Results of needle insertions into nerves • The Dimple and penetration force vs. needle diameter • ANOVA and Newman-Keul: • Penetration force was the similar for all needles except the 200µm needle. (p=0.0001) • Mean of dimple was equal for all needle diameters. (p=0.048) • The largest opening angles (>24°) differed. (p=0.00009)

  7. Discussion • The SMB-model works • The peripheral nerve is not elastic in accordance with the SMB-model • Penetration force differed for the 200µm needle • Dimple is unaffected by needle diameter • The opening angle of the needle is a crucial factor in dimple and penetration force • The mechanical behavior of the peripheral nerve resembles friction

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