Cannulated Screws – Types and Benefits

Cannulated Screws are specialized orthopedic implants used to treat fractures, perform osteotomies, and fix bones during surgeries. These screws have a central hollow core (cannulation) that allows them to be inserted over a guide wire or pin, enabling precise placement, especially in minimally invasive or image-guided procedures.

Types of Cannulated Screws

Here’s a detailed breakdown of the types of cannulated screws, based on design, function, thread configuration, and use cases in orthopedic surgeries:

Partial Thread Cannulated Screws

• Description: These screws have threading on only a portion of the shaft (usually the distal part).
• Function: Creates interfragmentary compression by allowing the proximal smooth portion to glide through the bone while the threaded portion anchors into the opposite fragment.
• Use Cases: Femoral neck fractures, Ankle fractures (medial malleolus) and Scaphoid fractures
• Advantage: Excellent for lag screw technique, pulling two bone fragments tightly together.

Fully Threaded Cannulated Screws

• Description: Threads cover the entire shaft of the screw.
• Function: Provides uniform fixation and stability across the full length of the screw.
• Use Cases: Diaphyseal fractures, Arthrodesis procedures (joint fusion), and Metaphyseal fractures where compression is not required
• Advantage: Maintains alignment and prevents telescoping or shortening of bone fragments.

Headed Cannulated Screws

• Description: Have a solid head on the proximal end, sometimes used with washers.
• Function: Provides a strong purchase point for driving the screw and applying compression.
• Use Cases: Long bone fractures and Fractures requiring additional surface compression
• Advantage: Offers more torque during insertion and enhanced fixation strength.

Headless Cannulated Compression Screws (HCCS)

• Description: No prominent head; screw is buried flush or below the bone surface.
• Function: Allows compression across the fracture site with minimal prominence.
• Use Cases: Scaphoid fractures, Metacarpal/metatarsal fractures, Small joint arthrodesis (e.g., toe, finger)
• Advantage: Minimizes irritation of soft tissue or joints. often has variable pitch threading to create compression without a head.

Variable Pitch Cannulated Screws

• Description: The pitch (distance between threads) varies along the screw shaft—typically coarser at the tip and finer near the head.
• Function: Generates gradual compression as the screw is inserted.
• Use Cases: Intra-articular fractures and Nonunion or delayed union fractures
• Advantage: Allows for controlled, automatic compression without overtightening.

Cannulated Lag Screws

• Description: Specifically designed to function as lag screws, either fully or partially threaded.
• Function: Creates compression between bone fragments.
• Use Cases: Acetabular or pelvic fractures and High-stress bone areas
• Advantage: Excellent for fragment fixation where strong compression is needed.

Cannulated Screws for Specific Anatomical Locations

Cannulated Cancellous Screws:

• Typically, larger diameter and coarse threads.
• Used in spongy (cancellous) bone, like in the femoral head, humeral head, or calcaneus.

Cannulated Cortical Screws:

• Finer threads, smaller diameter, used in dense cortical bone.
• Less common but available for specific diaphyseal applications.

Benefits of Cannulated Screws

Here are the detailed benefits of cannulated screws, which make them a popular choice in modern orthopedic and trauma surgeries:

Precision Placement Over Guide Wire

• Cannulated screws are designed to be inserted over a guide wire or Kirschner wire (K-wire).
• This minimizes the risk of misplacement, especially in deep or anatomically complex areas like the femoral neck, pelvis, or scaphoid.
• Ensures accurate trajectory and alignment during fixation.

Minimally Invasive Technique

• Enables percutaneous (small incision) insertion, reducing soft tissue damage.
• Leads to: Less blood loss, Faster recovery, Lower risk of infection and Shorter hospital stay
• Particularly beneficial in elderly or polytrauma patients.

Versatility Across Anatomical Sites

• Available in various lengths, diameters, and thread configurations.
• Used in:
• Long bone fractures (femur, tibia, humerus)
• Small bone fractures (scaphoid, metatarsals, phalanges)
• Joint fusions and osteotomies
• Suitable for both cancellous and cortical bone applications.

Controlled Compression at Fracture Site

• Partial thread and variable pitch designs allow interfragmentary compression, which Promotes primary bone healing, improves stability of fracture and Reduces the risk of nonunion
• Ideal for lag screw technique.

Reduced Soft Tissue and Joint Irritation

• Headless cannulated screws are buried within the bone, avoiding protrusion.
• Ideal for intra-articular or small bone areas (e.g., wrist, foot).
• Prevents soft tissue irritation and reduces the need for later screw removal.

Radiolucent Compatibility for Fluoroscopy

• The guide wire and hollow core make them easy to visualize and guide under X-ray or C-arm fluoroscopy.
• Ensures real-time correction of screw position during surgery.

Time-Saving and User-Friendly Design

• Streamlines surgical workflow by eliminating the need for extensive exposure or dissection.
• Quick and easy insertion over a pre-placed guide wire.
• Beneficial in both elective surgeries and emergency trauma cases.

Ideal for Complex and Fragile Bones

• Excellent for osteoporotic bones, where precision is critical to avoid fragmentation.
• Common in geriatric patients, especially for femoral neck and intertrochanteric fractures.

Multiple Configurations and Customization

• Comes in different thread lengths, diameters, head options (headed/headless), and materials (titanium or stainless steel).
• Surgeons can customize based on fracture pattern, bone quality, and surgical goal.

Reduced Risk of Implant Prominence

• Especially with headless designs, the screws stay buried and are less likely to cause issues like: Tendon irritation, Joint restriction and Soft tissue impingement.