This document provides an overview of screws in orthopedic surgery. It discusses the history of screw development from ancient times through modern innovations in materials. The anatomy of a screw is described in detail, including the head, shaft, thread, tip, and special features like pitch, diameter, and cannulation. Different types of screws are compared based on their properties and intended uses in cortical versus cancellous bone. Special screw designs like Herbert screws, lag screws, and dynamic hip screws are also briefly mentioned.

1. SCREWS
DR. PRATIK DHABALIA
JUNIOR RESIDENT

2. OVERVIEW
HISTORY
• Father of screw - Archimedes of Syracuse
• Used for irrigation

3. • By the late 18th century, European and American craftsmen had developed
and patented effective screw-cutting lathes

4. • In 1850, French surgeons Cucel and Rigaud performed the
first internal fixation procedure by reducing an olecranon
fracture with 2 transcutaneous screws fastened by string.
• Perhaps more famously, German surgeon Carl Hansmann
performed the first internal plate fixation using a removable
steel plate and nickel-plated screws in 1886.

5. • Danis was able to achieve precise anatomical fracture reductions with rigid
fixation.
• Maurice Müller, himself one of Danis’ students.
• Arbeitsgemeinschaft für Osteosynthesefragen (AO)—German for the
Association for the Study of Internal Fixation.
• Introduction of stainless steel in 1926 to the testing of titanium alloys in the
1970s.
• Biomechanical qualities of screw features, such as cannulation, tread depth,
pitch, and single- vs double-lead threads.

6. SCREW - INTRODUCTION
• A device used to convert small applied rotational force into large compressive
force.
• Helps in
1. Holding plate or other prosthesis to the bone
2. Fixing fracture fragments
3. Achieving compression at fracture fragments.

7. ANATOMY OF SCREW
• Four main parts:
1. Head
2. Shank/shaft
3. Thread
4. Tip

9. 1. HEAD
• Serves two functions –
1. Provides the means
for applying torque to
the screw.
2. It acts as a stop –
translation force
converts to
compressive force.
• Recess – for firm
purchase of screwdriver
on the head for insertion
and removal.

10. OTHER TYPES

11. 2. COUNTERSINK
• Undersurface of the head.
• Either conical or hemispherical
• Conical – inserted centered or
perpendicular to the hole in the plate.
• Hemispherical – allows the screw to
be angulated
• Hemispherical threaded – used in
locking plates.

12. 3. SHAFT
• Link between head and
thread.
• Non existent in standard
cortical screw.
• Long shaft in lag screws –
smooth shaft has no
purchase.

13. 4. RUN OUT
• Transitional area between shaft
and thread.
• Represents location of significant
stress because of changes in
diameter and sharp corners.
• Typically breaks with spiral
configuration.
• More chances in fully threaded
than in partially threaded.

14. 5. THREAD
• Converts torque into compressive force.
• Standard screw – single threaded
• Double threaded – advances more faster but
requires more torque.
6. CORE DIAMETER
• Inner or root diameter
• Narrowest diameter
• Determines minimum cross section area of screw
• Smaller diameter has more tendency to shear off

15. 7. OUTER DIAMETER
• Diameter across maximum thread width.
• Affects the pull out strength
• More in cancellous screws.
8. PITCH
• Distance between two adjacent threads
• Determines rate of advance
• Small pitch – advances less, more compression, cortical bone.
• Typically – 1.75mm/40.5tpi
• Lead is the distance it travels on one complete turn.

16. 9. TIP
I. Self tapping
II. Non self tapping
III. Corkscrew
IV. Trocar tip
V. Self drilling self tapping tip

17. CORTICAL CANCELLOUS
TIP Tapered Non tapering
PITCH Small Large
CORE DIAMETER Larger than shaft Smaller than shaft
HOLD More Less
PULL OUT STRENGTH Less More
LAG SCREW No Yes
PILOT HOLE Pre tapping No Pre tapping
CANNULATION Absent Present

18. SPECIAL SCREWS
• Herbert screw
• Lag screw
• Dhs screw

19. HERBERT SCREW
• Interfragmentary compression
• Differential pitch
• Headless

20. DYNAMIC HIP SCREW

21. LAG SCREW