Skip to content
Epomedicine
Epomedicine

Mnemonics, Simplified Concepts & Thoughts

  • Medical Students
  • Bedside Clinics
  • Case Reports
  • Emergency Medicine
  • Blog
  • Surgical Skills
  • Medical Mnemonics
Epomedicine

Mnemonics, Simplified Concepts & Thoughts

Orthopedic Screw Insertion Mnemonic

Dr. Sulabh Kumar Shrestha, MS Orthopedics, Dec 18, 2021Jan 20, 2024

Last updated on January 20, 2024

Don’t Marry Too Soon

DRILL

  1. Choose the correct drill bit
  2. Insert the drill bit correctly in the chuck
  3. Tighten the chuck sufficiently
  4. Start the drill home perpendicular to the surface
  5. Maintain adequate pressure
  6. Maintain the proper direction
  7. Irrigation with normal saline should be commenced simultaneously with drilling
  8. Keep the drill rotating while backing it out
  9. Countersink (create circular sit for undersurface of screw head) when screw is used outside plate in cortical bone.
  10. Drill bit size:
    • For thread hole: Core diameter (4.5 mm cortical and malleolar screw and 6 mm cancellous screw all have core diameter of 3 mm – hence, 3.2 mm drill bit is used for all)
    • For gliding hole: Outer diameter for cortical screw and Shaft diameter for cancellous screw (Shaft diameter of 6 mm cancellous screw is 4.5 mm)
Screw diameter (mm)Screw typeThread hole (mm)Gliding hole (mm)
1Cortical0.81
1.3Cortical11.3
1.5Cortical1.11.5
2Cortical1.52
2.4Cortical1.82.4
2.7Cortical22.7
3.5Cortical2.53.5
4Cortical2.94
Cancellous2.5
4.5Cortical3.24.5
Malleolar3.24.5
6Cancellous3.24.5
orthopedic screws

MEASURE

Measure before tapping as depth gauge may damage the thread.

Correct way of measuring in oblique hole: The hook of depth gauge tends to slip off the obtuse angled tip of the thread hole, but engaging the obtuse angle of the hole is is the correct way of making measurement as engagement of acute angled lip of thread hole gives short reading.

Appropriate length:

  • Measure the length with head for locking screws and without head for non-locking screws
  • Add plate thickness to the measured length (2-4 mm)
  • For cortical bone:
    • >/= 1 full thread must exit far cortex
    • Self-tapping: Flutes must be out of far cortex and >/= 1 full thread must engage cortex (add 2 mm more)
  • For cancellous bone: Sharp tip threatens the soft tissues, hence engagement of full thread in far cortex as in cortical screw is unnecessary

TAP

Tapping refers to cutting threads in a drill hole.

Center line of tap should coincide with the center line of hole.

Tap in couples of 2 turns forward and 1/2 reverse turn until 2 threads of tap emerges out of far cortex.

Tap is removed by twisting in reverse direction.

Tap only near cortex in cancellous bone.

SCREW

Keep insertional torque (recommended 2.824 Nm) and axial force as low as possible.

Screw is centered and inserted perpendicular to the hole in a plate.

Avoid overtightening of screw.

Washer – used as an artificial cortex in cancellous bone to prevent burying of screw head into thin cortex.

  • Flat side: rests on bone
  • Concave (Countersink) side: underside of screw head

dr. sulabh kumar shrestha
Dr. Sulabh Kumar Shrestha, MS Orthopedics

He is the section editor of Orthopedics in Epomedicine. He searches for and share simpler ways to make complicated medical topics simple. He also loves writing poetry, listening and playing music.

  • Facebook
  • Twitter
Surgical Skills BiomechanicsOrthopedics

Post navigation

Previous post
Next post

Leave a Reply Cancel reply

Your email address will not be published. Required fields are marked *

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Shrestha SK. Orthopedic Screw Insertion Mnemonic [Internet]. Epomedicine; 2021 Dec 18 [cited 2025 May 25]. Available from: https://epomedicine.com/surgical-skills/orthopedic-screw-insertion-mnemonic/.

Pre-clinical (Basic Sciences)

Anatomy

Biochemistry

Community medicine (PSM)

Embryology

Microbiology

Pathology

Pharmacology

Physiology

Clinical Sciences

Anesthesia

Dermatology

Emergency medicine

Forensic

Internal medicine

Gynecology & Obstetrics

Oncology

Ophthalmology

Orthopedics

Otorhinolaryngology (ENT)

Pediatrics

Psychiatry

Radiology

Surgery

RSS Ask Epomedicine

  • What to study for Clinical examination in Orthopedics?
  • What is the mechanism of AVNRT?

Epomedicine weekly

  • About Epomedicine
  • Contact Us
  • Author Guidelines
  • Submit Article
  • Editorial Board
  • USMLE
  • MRCS
  • Thesis
©2025 Epomedicine . All rights reserved.