Cancellous Screw

What are cancellous screws？

Cancellous screws have a larger pitch, and a larger thread diameter to core diameter ratio. They can be both fully or partially threaded, and — no surprise here — are used in cancellous bone. Cancellous bone describes the spongy bone found at the ends of long bones, in the pelvic bones, ribs, skull, and the vertebrae in the spinal column.

cancellous screws specifications

4.0mm Cancellous Screw

4.0mm Cancellous Screw              Half-threaded

6.5mm Cancellous Screw               Full-threaded

Cancellous Screw: An Overview of Usage, Indications, and Techniques

Introduction

Cancellous screws are a type of orthopedic screw used to fixate bone fragments or grafts in the treatment of fractures, non-unions, and other bone injuries. These screws are widely used in orthopedic surgery due to their biocompatibility, ease of insertion, and excellent mechanical properties. In this article, we will discuss the indications, techniques, and outcomes of using cancellous screws in orthopedic surgery.

Anatomy and Mechanical Properties of Cancellous Screw

Cancellous screws are made of titanium or stainless steel and have a threaded shaft and a tapered tip. The threads on the shaft provide excellent purchase in the cancellous bone and prevent pull-out, while the tapered tip facilitates easy insertion without damaging the surrounding tissues. The screws come in different sizes and lengths to accommodate different bone sizes and fracture patterns. The mechanical properties of cancellous screws are dependent on the material, diameter, length, and thread design. The use of larger diameter and longer screws increases the holding power and stability, while the use of smaller diameter and shorter screws reduces the risk of overdrilling and screw migration.

Indications for Cancellous Screw Fixation

Cancellous screws are indicated for a variety of orthopedic conditions, including:

• Fractures of the long bones, such as the femur, tibia, and humerus

• Fractures of the small bones, such as the wrist, ankle, and foot

• Non-unions and delayed unions of fractures

• Osteotomies, such as corrective bone cuts for deformity or malalignment

• Arthrodesis, such as fusion of the ankle, wrist, or spine

• Bone graft fixation, such as in spinal fusion or bone defect reconstruction

Techniques for Cancellous Screw Fixation

The technique of cancellous screw fixation depends on the specific indication and fracture pattern. The general principles of screw insertion include:

1. Proper positioning of the patient and identification of the fracture site

2. Creation of a pilot hole using a drill bit or a tap

3. Measurement of the screw length and diameter

4. Insertion of the screw using a screwdriver or a power drill

5. Verification of the screw position and depth using imaging modalities, such as fluoroscopy or X-ray

The key factors that affect the success of cancellous screw fixation include proper alignment of the fracture fragments, adequate reduction of the fracture, appropriate screw placement and length, and proper tensioning of the screw. Complications of cancellous screw fixation include screw loosening, screw breakage, screw migration, non-union, malunion, infection, and nerve or vessel injury.

Outcomes of Cancellous Screw Fixation

The outcomes of cancellous screw fixation depend on the specific indication and patient factors, such as age, comorbidities, and smoking status. In general, cancellous screw fixation provides excellent stability and compression of the fracture fragments, which leads to rapid bone healing and restoration of the normal function. The success rate of cancellous screw fixation ranges from 80% to 95%, depending on the indication and fracture pattern. The complications of cancellous screw fixation can lead to poorer outcomes, such as delayed healing, non-union, and chronic pain.

Conclusion

Cancellous screws are a versatile and effective tool in orthopedic surgery for the fixation of bone fractures, grafts, and fusion. The proper use of cancellous screws requires a thorough understanding of the anatomy, indications, techniques, and outcomes of the procedure. The selection of the appropriate screw size, length, and insertion technique should be tailored to the specific fracture pattern and patient factors. The use of cancellous screws can lead to excellent outcomes and rapid healing, but careful monitoring and management of complications are essential for optimal results.

FAQs

1. What is a cancellous screw? A cancellous screw is an orthopedic screw used to fixate bone fragments or grafts in the treatment of fractures, non-unions, and other bone injuries.

2. What are the indications for cancellous screw fixation? Cancellous screws are indicated for a variety of orthopedic conditions, including fractures, non-unions, osteotomies, arthrodesis, and bone graft fixation.

3. What are the key factors that affect the success of cancellous screw fixation? The key factors that affect the success of cancellous screw fixation include proper alignment of the fracture fragments, adequate reduction of the fracture, appropriate screw placement and length, and proper tensioning of the screw.

4. What are the complications of cancellous screw fixation? The complications of cancellous screw fixation include screw loosening, screw breakage, screw migration, non-union, malunion, infection, and nerve or vessel injury.

5. What are the outcomes of cancellous screw fixation? The outcomes of cancellous screw fixation depend on the specific indication and patient factors, but in general, cancellous screw fixation provides excellent stability and compression of the fracture fragments, which leads to rapid bone healing and restoration of the normal function.