Advanced Biomedical Engineering
Online ISSN : 2187-5219
ISSN-L : 2187-5219
Effect of Needle Geometry on Insertion Force of Different Hair Implanters
Hyunhee BangHoseob SongChul-woo ParkIlhyung ParkMoonkyu KimSanghyun Joung
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2021 Volume 10 Pages 90-100


Surgeons insert approximately 3000 hair implants in a single hair restoration surgery, and the needle shape critically affects surgical performance including surgical time, survival rate, and the surgeon's fatigue. There are several experimental studies on the relationship between needle shape and performance; however, there are no studies on hair implant needles, which are different from other medical needles as they have a comparatively short bevel. This study compared several hair implant needles to determine the relationship between needle shape and insertion force. Eight hair implant needles with the same diameter were collected, and their geometrical data were visually measured. The insertion force and total work of each needle were measured using custom-made force measurement equipment; the results were statistically compared, and their correlation was analyzed. Moreover, a qualitative comparison was made. The needle insertion force ranged from 1.30 to 2.97 N, and the total work ranged from 8.15 to 10.97 mJ. The primary bevel and acute angles showed a moderate positive correlation with the total work. A longer point length, smaller primary bevel, and acute angle decrease the total work of hair implant needles. As per the results of the qualitative comparison, we found that the surgeons can identify the differences in needle insertion force among various hair implant needles, and their grading was consistent with the grading according to the total work of needle insertion.

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© 2021 Japanese Society for Medical and Biological Engineering

Copyright: ©2021 The Author(s). This is an open access article distributed under the terms of the Creative Commons BY 4.0 International (Attribution) License (, which permits the unrestricted distribution, reproduction and use of the article provided the original source and authors are credited.
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