Definition

Bone Screws are a special type of Orthopedic Screws, used for surgery. They are also called Bone Fixation Screws or Cancellous Bone Screws. These Bone Screws are meant to stabilize fractures. The Orthopedic Screws may or may not be removed after the bone gets fully healed. The Bone Fixation Screws can be used to place external fixators. They can be used as implants as well.

Safe and inert raw material goes into the production of the GPC Bone Screws. Stainless Steel as well as Titanium Orthopaedic Screws are produced by us.

Classification

Orthopaedics screws may be classified depending on the following characteristics.

Design

• Conventional screws
• Locking screws
• Headless screws
• Cannulated etc.
• Single- vs double-lead threads.

Material

• Titanium
• Stainless steel
• Bioabsorbable

Size

• 3.5 mm
• 4 mm
• 4.5 mm
• 6.5 mm etc.

Function or mechanism:

•   Neutralisation screws – neutralises forces on the plate in plate fixation.
•   Lag screws – For inter-fragmentary compression.
•   Reduction screw – To reduce displaced fracture by pushing or pulling.
•   Position screw – Holds two fragments in position without compression. Eg. Syndemotic screw
•   Anchor screw – Acts as an anchor for wire or suture. In tension band wiring
•   Locking head screw – In locking plates
•   Locking screw – In interlocking nails
•   Poller screw – To guide the nail path in interlocking nailing of fractures close to the bone ends.

Structure of Screw:

Screw has the following parts

• Core – Solid section from which the threads project out wards. The size of core determines the strength of screw and its fatigue resistance. The size of drill bit used is equal to the core diameter.

• Threads- Thread diameter is the maximum diameter of threads. Thread depth is half of the difference between thread diameter and core diameter. The thread depth determines the amount of contact with the bones which in turn determines the resistance to pull out. The size of tap is equal to the thread diameter.

•  Head – Prevents sinking of screw into the bone. Hemispherical in shape to increase the surface area for load transfer and to allow angulated insertion. Can be improved by use of washer. Allows attachment of screw driver. The slot for screw driver may be star, hexagonal or Philips.

•   Tip – May be blunt, corkscrew, self tapping or trocar tip.

Common Bone Screws

Three types of bone screws are used.

• Cortex screw thread is designed for  diaphyseal bone
• Cancellous bone screws designed for cancellous bone. The threads have larger pitch, larger outer diameter and are deeper.
• Locking head screws have larger core diameter and shallow thread with blunt edges.

Alpine
Managing Editor
Journal of Orthopedic and trauma.
What’s App: +1-947-333-4405