What is the Difference Between Cortical and Cancellous Screw

The key difference between cortical and cancellous screw is that cortical screw has a fine pitch while cancellous screw has a coarse pitch.

In different orthopedic surgeries, different screws are used to treat trauma related to bones. These screws keep the damaged bone fragments together in order to increase the chance of healing and to provide stability for the body in the context of posture and movement. Screws designed for cortical bone and cancellous bone are the two main types (thread types) of surgical screws. Both screws are manufactured under medical grade standards with the usage of high-quality material such as stainless steel 316L or titanium.

CONTENTS

1. Overview and Key Difference
2. What is a Cortical Screw
3. What is a Cancellous Screw
4. Similarities – Cortical and Cancellous Screw
5. Cortical vs Cancellous Screw in Tabular Form
6. Summary – Cortical vs Cancellous Screw

What is a Cortical Screw?

A cortical screw is a type of a mechanical screw used by orthopedic surgeons to affix bone plates and other orthopedic devices to the cortical bone. In other words, these screws are involved in fixing bone damages due to accidents and trauma. Cortical screws used in such surgeries are medical grade. These screws are the most frequently used screws in bone trauma.

Cortical screws possess a smaller diameter with a fine pitch. The thread pattern of the cortical screw is a full thread. The gauge of a cortical screw varies from 2 mm to 4.5 mm. The length of such screws varies from 8 mm to 60 mm, depending on the requirement. Most of the time, a cortical screw is involved in the fixation of the similar diameter non-locking plates. The thread pattern is either complete threaded or partial threaded.

What is a Cancellous Screw?

A cancellous screw is a type of a mechanical screw used by orthopedic surgeons to affix bone plates and other orthopedic devices to the cancellous bone. These screws are medical-grade screws manufactured with either stainless steel 316L or titanium. The function of a cancellous screw is to produce interfragmentary compression in joint areas, as in this tibia head fracture.

The design of cancellous screws optimizes the fixation in metaphysical bone environments. Cancellous screws possess a coarse pitch. The gauge of a cortical screw varies from 2 mm to 4.5 mm. The thread pattern is either complete threaded or partial threaded. They are non-self-tapping screws. The important feature of these screws is that they should not be tapped all way, only the first few turns, because they function much better when they cut their own way into cancellous bone.

What are the Similarities Between Cortical and Cancellous Screw?

• Cortical and cancellous screws are two types of surgical screws.
• Both screws are involved in bone surgeries.
• Both cortical and cancellous screws keep the bones together.
• They are made up of SS 316L or titanium.
• Moreover, the screw patterns are in either fully threaded or partially threaded format.

What is the Difference Between Cortical and Cancellous Screw?

A cortical screw has a fine pitch while a cancellous screw has a coarse pitch. Thus, this is the key difference between cortical and cancellous screw. A large thread pattern is produced by cortical screws whereas small thread patterns are produced by cancellous screws.

The below infographic presents the differences between cortical and cancellous screw in tabular form for side-by-side comparison.

Summary – Cortical vs Cancellous Screw

The cortical screw has a fine pitch while the cancellous screw has a coarse pitch. The function of a cortical screw is to produce interfragmentary compression in places such as the outer layer of the long bones forming the shaft and the inner part of the trabecular bone at the proximal and distal ends of the bone tissue fracture. The function of a cancellous screw is to produce interfragmentary compression in joint areas, as in this tibia head fracture. Both these screws are manufactured under medical grade standards with the usage of high-quality material such as stainless steel 316L or titanium. So, this summarizes the difference between cortical and cancellous screw.

Reference:

1. Buck, J Stewart, et al. “Teaching Cortical-Screw Tightening: A Simple, Affordable, Torque-Directed Training Protocol Improves Resident Performance.” The Journal of Bone and Joint Surgery. American Volume, U.S. National Library of Medicine.
2. “Florian Gebhard.” AO Foundation Surgery Reference.

Image Courtesy:

1. “Cortical screw” By Netha Hussain – Own work (CC BY-SA 3.0) via Commons Wikimedia
2. “Dynamic condylar screw” By Netha Hussain – Own work (CC BY-SA 3.0) via Commons Wikimedia