A calcar screw is a specialized orthopedic implant primarily utilized in the surgical repair of proximal humerus fractures. Its critical function is to anchor into the calcar region of the humerus, providing essential medial column support to ensure the stability of the fracture fixation.
Understanding Its Role and Significance
In the context of locked plate fixation for fractures of the upper arm bone, the calcar is an extremely important anatomical landmark. It acts as a robust anchor point for these screws, which are vital for supporting the medial column of the humerus. This support is crucial for the overall stability of the surgical construct and for successful healing.
The design of a calcar screw often involves a fixed-trajectory locking screw as part of a larger locking plate implant system. This design ensures a strong, stable connection between the screw, the plate, and the bone, maximizing biomechanical support at this critical site.
| Feature | Description |
|---|---|
| Primary Purpose | Provides crucial medial column support in proximal humerus fractures. |
| Anatomical Target | Anchors specifically into the calcar region of the humerus (upper arm bone). |
| Surgical Context | Used within locked plate fixation systems, a common method for stabilizing complex fractures. |
| Common Type | Frequently designed as a fixed-trajectory locking screw, integrating seamlessly with locking plate implants to ensure optimal stability and prevent screw back-out or toggle. |
| Clinical Benefit | Enhances the stability of the fracture repair, reducing the risk of implant failure and promoting proper bone healing by resisting collapse of the medial column. |
The Importance of Medial Column Support
Medial column support provided by a calcar screw is paramount in proximal humerus fractures. The medial column of the humerus bears significant compressive loads, especially during activities that involve the arm. Without adequate support, there is a substantial risk of the fracture collapsing, leading to:
- Loss of reduction: The fracture fragments can shift out of their correct alignment.
- Varus collapse: The humeral head can tilt inwards, causing malunion or nonunion.
- Implant failure: The plate or other screws may fail under stress if the medial column does not provide sufficient load-sharing.
By securely engaging the calcar, calcar screws distribute these loads more effectively, protecting the implant and allowing the bone to heal in a stable environment.
Design and Integration with Locking Plates
Modern locking plate implants are designed with specific pre-contoured trajectories for screws, including those intended for the calcar. A fixed-trajectory locking screw, as opposed to a non-locking screw, creates a fixed-angle construct with the plate. This robust connection enhances the stability of the entire system, making it particularly advantageous in osteoporotic bone or complex fracture patterns where traditional screw fixation might be less secure. The calcar screw is strategically positioned within this system to maximize its biomechanical contribution to the medial column.
