When it comes to repairing broken bones or stabilizing joints, orthopedic screws are real unsung heroes. While they may seem like simple pieces of metal, these screws play a critical role in ensuring that bones heal properly after fractures, surgeries, or corrective procedures. Whether you’re a medical student, a curious patient, or someone interested in healthcare innovations, understanding the types of orthopedic screws can give you valuable insight into how modern medicine works.
In this guide, we’ll break things down in a straightforward way—no heavy jargon, just the essentials you need to know about these tiny but mighty tools.
What Are Orthopedic Screws?
Let’s start with the basics. Orthopedic screws are specialized fasteners designed to hold bones together. Think of them like the screws you use in DIY projects, but engineered for the human body. They’re made from materials like stainless steel, titanium, or bioabsorbable compounds that are strong, biocompatible, and safe to implant inside the body.
Orthopedic screws come in various shapes and sizes because bones and fractures vary a lot too. Surgeons choose different types based on factors like the location of the injury, the type of fracture, and the bone’s density.
Why So Many Types of Orthopedic Screws?
You might wonder: Why can’t one type of screw do it all? Well, bones aren’t all built the same. A screw that works for a delicate wrist fracture won’t necessarily work for a large thigh bone. Different scenarios require different solutions, which is why orthopedic screws are designed with unique features to meet specific needs.
Let’s explore the main types of orthopedic screws you’ll hear about.
What Are the Different Types of Orthopedic Screws?
Cortical Screws
These are the go-to screws for dense bone, typically the outer layer of the bone called the cortex. Cortical screws have a smaller thread depth and are tightly pitched, which makes them perfect for gripping hard, compact bone. They are usually used as lag screws or for plate fixation in the diaphyses of large bones. They are also used as fixation screws for the tension device or the pelvic reduction forceps. The thread and the polished surface allow easy removal of the screw, even though hard cortical bone will have grown between the threads during healing. These screws have a smooth tip. It is essential for the holding power of the screw that the threads engage the entire far cortex. The tip of the screw and one or two threads should therefore protrude on the opposite side of the bone. These screws are ideal for:
- Fixing fractures in long bones like the femur and tibia
- Securing plates to bones
Their strength and design make them ideal when firm, solid fixation is needed.
Cancellous Screws
Cancellous screws are designed for spongier bone, found in areas like the pelvis or around joints. They have wider threads and a deeper pitch, allowing them to “bite” better into the softer bone. These screws are used only in the metaphyseal and epiphyseal areas, with fine trabecular bone and relatively thin cortex. Three different types of screws exist: one with a 16 mm thread length, another with a 32 mm thread length, and the third fully threaded.
The screws with shafts are designed as lag screws; the fully threaded screw is mainly used as a plate fixation screw when the end holes of a plate are located over cancellous bone. The deep and wide threads of the cancellous bone screw ensure good purchase in the compressed cancellous trabeculae. Tapping is only necessary in the near cortex to allow introduction of the screw. The holding power in the fine trabecular bone is in- creased when the screw itself creates its thread by pressing bone aside. Engaging the far cortex increases the holding power of the screw, but is not necessary in porotic bone. However, the tip is pointed and care must be taken not to damage any structures on the opposite side of the bone if its is left protruding too far. These screws are best suited for:
- Fixing fractures in areas with less dense bone (e.g., around the hip)
- Holding together fragments of bones within joints
These screws often have a partially threaded design, helping draw fractured pieces together tightly.
Cannulated Cancellous Screws
Cannulated screws are hollow in the middle, allowing them to be guided over a wire or pin during insertion. This makes them incredibly useful for precise placement, especially in tricky or minimally invasive surgeries.
The primary indications for 7.0 mm cannulated screws are frac- tures involving large metaphyseal/epiphyseal fragments such as:
- Intracapsular fractures of the hip
- Tibial plateau fractures
- Femoral intercondylar fractures
- Paediatric femoral neck fractures
- Slipped capital femoral epiphysis
- Ankle arthrodesis
- Sacroiliac joint disruptions
The screws are applied as lag screws and can be inserted percutaneously, or through a normal surgical approach. The 7.0 mm cannulated screws in different lengths and the in- struments for their application can be obtained in either a graphic case or in a sterilising tray.
They can be best used for:
- Fractures in the hip, wrist, or ankle
- Procedures where pinpoint accuracy is essential
The hollow design may sound fragile, but these screws are surprisingly sturdy.
Lag Screws
Lag screws are designed to compress two pieces of bone together. They work by sliding through the first piece of bone and threading into the second, effectively pulling the pieces tight like a clamp. Surgeons use these screws generally for:
- Bringing fractured bone fragments together
- Encouraging faster healing through compression
Often, lag screws are used alongside plates for added stability.
Herbert Screws
Herbert screws are a specific type of headless compression screw. They’re most commonly used for small bones, especially in wrist and scaphoid fractures. These screws provide compression without the need for a separate lag screw, thanks to their unique dual-thread design. They are best in cases for:
- Fixing scaphoid fractures
- Joints where compression is critical
Herbert screws are brilliant for situations requiring both compression and a smooth, buried finish.
Bioabsorbable Screws
In recent years, bioabsorbable screws have gained attention. These are made from materials that gradually dissolve in the body as the bone heals, eliminating the need for a second surgery to remove them. They are ideal for:
- Pediatric cases where future growth is expected
- Situations where implant removal is impractical
While not as widely used as metal screws yet, bioabsorbable options represent the exciting future of orthopedics.
Final Thoughts
Orthopedic screws may be small, but their impact on healing and recovery is huge. Each type is carefully designed for specific situations, ensuring that broken bones or surgical sites get the best possible support.
For patients, understanding the basics can help ease anxiety about upcoming procedures. And for budding medical professionals, a good grasp of orthopedic hardware is essential knowledge.
The next time you hear about someone having screws put in during surgery, you’ll know just how clever and crucial these tiny devices really are.
