Jiangsu Gather Biotech Co.,Ltd
Professional Orthopedic Implants and Instruments Development and Supplier
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Introduction:
The primary function of a bone screw is to produce compression in bones which is required to mend a bone injury. A screw converts all the forces that arise out of bone movement into compression and distributes this compression evenly throughout the surface of injured bones. It is due to this compression that a bone stays in place and heals faster. Screws can help in attaching implants to bones or anchorage or in fixation of soft tissue.
The structure of an orthopaedic screw is just like a normal screw, consisting of a head and the body. Let us see different parameters related to orthopaedic bone screws.
Head: A head of a screw is the top flattened surface of a screw which is mainly used to insert the screw.
Length: The length of a screw is measured as the length from head to the tip.
Diameter: There are two types of diameters. Outside diameter is the total thickness of a screw from one horizontal end of a thread to the other. Inner diameter is the thickness of a screw sans the threads. In order to insert a screw, the pilot hole must be the size of the inner diameter.
Pitch: A pitch of the screw is defined as the distance travelled by a screw with each 360º turn.
Material:
Depending upon the material used to make a screw, there are three types:
Stainless Steel: Stainless Steel screws are the most common. For cortex bones, they range from 1.5 to 4.5mm. For cancellous bones, they range from 3.5 to 6.5mm.
Titanium:Titanium screws are ideal for treating mandibular fractures. The rate of infection in titanium is less as compared to stainless steel.
Bio-absorbable:Bio-absorbable screws are mostly made up of polylactic acid, polyglycolic acid and poly-L-lcatic acid. There is no need to remove them afterwards, as they are absorbed by the body. But they also stimulate foreign body reaction in some cases.
Head: There are various screws depending upon the type of a head, some of them are as described below.
Threaded:Screws with threaded heads are beneficial in case when a screw is to be locked to an implant. The construct using threaded-head screws is more stable.
Hexagonal:Screws with hexagonal heads are the most common. They provide great attachment for screwdriver to insert the screw.
Crossed:These heads are normally present in smaller screws, to be used in phalangeal and metacarpal surgeries.
Cannulated: These screws are generally used to mend small and long bones, scaphoids, tibial plateau fracture etc. They can be self-drilling and self-tapping.