Types

Monaxial pedicle screws are key instruments for spinal fixing. These screws aid in supporting and stabilizing. There are different types of monoaxial screws, and each of them has a unique function and benefit.

Type by Material

Spine monoaxial pedicle screws set can be made from various materials, namely:

Titanium: Titanium has a high strength and comes with low weight as opposed to other metals. Also, it is highly resistant to corrosion. Hence, it is a popular choice in medical applications.
Stainless Steel: Stainless steel is very durable. Besides, it is easy to machine, thus making it fit for many medical applications. Moreover, it provides good tensile strength and is resistant to wear.
Cobalt-Chromium Alloys: Cobalt-chromium comprises high strength and outstanding biocompatibility. Therefore, these alloys are mainly used in high-stress implant applications.

Type by Coating

Coatings can enhance the screw's longevity, decrease friction, and improve biocompatibility. Common coatings are:

Hydroxyapatite Coating: It improves the screw's bone integration capability. Hydroxyapatite is a hard natural substance found in bone tissues.
Titanium Nitride Coating: It increases wear resistance. Additionally, it minimizes tarnishing and improves the screw's aesthetic properties.
Polymer Coating: These coatings offer lubrication and lessen the risk of adverse reactions upon tissue contact.

Type by Size

Monoaxial screws come in various sizes to suit different patient anatomies. A patient's bone density and the specific spinal area are crucial in determining the right size. Common size specifications are:

Diverse Diameters: The diameter can be between 4 mm to 8 mm. Larger diameters give more strength, while smaller ones are suitable for minimally invasive procedures.
Variable Lengths: The length ranges from 40 mm to 80 mm. The variety in lengths allows for proper engagement in the pedicle and vertebral body.

Type by procedure

These screws are used in various spinal procedures. Common applications enable creating a motion segment fusion in the dorsal spine. They include:

Deformity Correction: The screws facilitate correction during procedures like spinal fusion. They stabilize the spine as it heals and reduces the need for further surgery due to hardware failure.
Tumor Resection: In oncological cases, pedicle screws stabilize the spine. They help manage lesions by providing support in areas where the structural integrity has been compromised.
Trauma Repairs: In cases of traumatic injuries, such as fractures, pedicle screws are used to stabilize the affected vertebrae. They promote healing and restore alignment.

Function and Use

Monaxial screws fix and stabilize the spine. They provide a rigid connection between two adjacent vertebrae. They are primarily utilized in spinal fusion surgeries. In these surgeries, two or more vertebrae are permanently joined. Here are detailed functions of these screws:

Spinal Stability

Spinal stability prevents abnormal movements between adjacent vertebrae. Thus, it helps maintain proper alignment and reduces pain caused by nerve compression or instability.

Load Transmission

Monoaxial pedicle screws distribute the mechanical loads exerted on the spine during normal activities. These include walking, lifting, and twisting. Proper load transmission lowers the chance of adjacent segment disease harm.

Biomechanics Function

The rigid fixation provided by monoaxial screws alters the mechanics of the spinal segment. It creates a controlled environment for fusion. In doing so, it minimizes motion at the surgical level and facilitates bone healing. The reduced motion decreases friction between the nerves and surrounding tissues. Hence, minimizing discomfort and injury risk.

Anchor Points in Rod System

Monoaxial screws serve as primary anchors in the rod-based fixation system. The rod connects several screws across the spine section being treated. This connection allows for even force distribution, enhancing overall stability.

Design and Decoration

Pedicle screws are designed with different features to improve their performance and ease of implantation.

Screw Thread Design

The screw threads are designed for the bone's axial load and rotational torque.

Thread Profile: The threads have varying profiles. Some have deeper profiles for better load capture. Others have a finer pitch to reduce bone stress during insertion.
Thread Shape: It could be triangular, square, or trapezoidal. Each shape affects how the screw transfers loads and interacts with the surrounding bone.
Leading Edge: The leading edge of the thread is designed to cut into the bone gently as the screw is turned. This cutting edge reduces the torque needed for insertion.

Head Configuration

Head Type: Pedicle screw heads can have different configurations, such as round, bevelled, or low-profile designs. The head type influences how the rod is attached and affects the screw's multi-angle adjustability.
Slot or Screw Feature: Some heads have a slot or a specialized feature that allows for the use of a backup wrench. This design prevents the screw from rotating during the tightening of the rod.

Rod Connection

Rod Material and Profile: Rods are made from stainless steel and titanium alloys. These materials provide the needed strength and flexibility balance. Rod profiles can be circular or hexagonal. They affect the connection with the screw and the resulting stiffness.
Anti-Rotation Features: Some rods have integrated anti-rotation features. These are such as keyways or flats. They prevent unwelcome rod rotation relative to the pedicle screws. This function ensures torque is evenly distributed during spinal fixation and minimizes loosening over time.

Decoration and Aesthetic Quality

The performance of monoaxial pedicle screws is primarily focused on functional and structural integrity. But some decorative aspects may improve user perception and ease of control.

Coatings: These screws usually have either gold or silver electroplated finishes. The coatings improve corrosion resistance. Also, they enhance aesthetic appeal. Gold-tone screws are often more visible during surgery, while silver screws have a more subdued appearance.
Color-Coded Systems: Some manufacturers employ color-coded screw heads or shafts for easy identification. These colors correspond to specific sizes or angles. This design helps surgical teams quickly select the appropriate screw, which improves procedural efficiency.
Surface Textures: A variety of textured finishes have been applied to screw heads or collars. These are knurled or ridged patterns. They increase friction and improve handling during the installation.

How to Choose

Selecting the correct spinal monoaxial pedicle screws requires careful consideration of various factors. These factors ensure optimal surgical outcome and long-term patient health.

Material

Spinal fixation products are preferred in titanium and stainless steel alloys. Titanium has superior biocompatibility and radiolucency. The two ensure the implant is not visible on medical imaging. On the other hand, stainless steel provides better elasticity. Hence, it is more easily shaped to the required dimensions. There are also cobalt-chromium alloys. They feature excellent wear resistance and may be used in heavy load scenarios.

Bone Density

The quality of bone determines the screw choice markedly. High-density bone requires screws with greater diameters. On the other hand, low-density bone is more suited for smaller screws. The two help reduce the risk of bone fractures.

Pedicle Size

Use imaging modalities like CT or MRI to evaluate the pedicle size. Then choose screws that fit snugly within the pedicle. The snug fit reduces the risk of screw loosening and ensures proper load-bearing.

Cross-sectional Area

Select screws with larger cross-sectional areas for patients with osteoporosis and fragile bones. The feature helps in distributing mechanical loads more evenly. Thus minimizing the risk of bone fractures. On the other hand, screws with smaller cross-sectional areas are ideal for denser bones. They are easier to install owing to their reduced invasiveness.

Stereotactic Navigation

Consider how many pedicle screws are placed using stereotactic navigation. The navigation system improves accuracy and decreases the risk of malpositioning. It achieves this by providing real-time feedback on screw trajectory and depth. Therefore, the user may want to go for screws that have compatible with the navigation setup.

Local and Systemic Factors

Assess any local or systemic factors that affect the integration of the screw with adjacent tissues. They include infections or vascular disorders. Also, consider previous spinal surgeries. These factors could result in scar tissue formation, which affects screw placement.

Q&A

Q. What is the difference between monoaxial and polyaxial pedicle screws?

A) The difference between monoaxial and polyaxial screws lies in their design and flexibility. Monoaxial screws have a fixed angle of attachment. This feature ensures a rigid and stable connection. It makes them ideal for situations requiring strong support. On the other hand, polyaxial screws have a flexible ball-and-socket joint mechanism. The feature allows multi-angle adjustments. It makes them suitable for complex spinal geometries.

Q. How do coatings enhance the longevity of monoaxial pedicle screws?

A) Coatings like titanium nitride and hydroxyapatite serve diverse functions that enhance the screw's longevity. One, they reduce wear and tear during the insertion and use, and two, they improve the screw's integration with bone. It minimizes the chances of loosening over time. Also, some coatings like polymer may provide a buffer against adverse tissue reactions. They help in resisting corrosion, thus maintaining the screw's integrity over time.

Q. How are monoaxial pedicle screws selected for specific spinal regions?

A) Monoaxial screws are selected based on the unique biomechanical requirements of each spinal region. They take into account these screws' size, shape, and material properties. For instance, in the cervical region, smaller diameter screws are preferred due to space constraints. On the other hand, lumbar region screws often have a larger diameter. More robust screws are better suited to handle higher loads because of this region's increased weight bearing.

Q. What role do bone density and pedicle size play in screw selection?

A) Bone density and pedicle size significantly impact the selection of monoaxial pedicle screws. For one, higher bone density requires screws with greater holding power. On the other hand, lower density demands screws that provide a secure and gentle fit to minimize bone trauma. On the other hand, pedicle size determines the screw choice. Larger pedicles are suited for bigger screws, while narrower ones have smaller screws.

Spine monoaxial pedicle screw

Factory Price Titanium Spine Screw 5.5 Spinal Monoaxial Screw Orthopedic Surgical Spinal Implant Orthpedic By Surgiright

Popular in your industry

Baby Health Care Products

Rehabilitation Therapy

Absorbent Aids

Dark Room Supplies

Top categories

Related Searches: