A spinal cage is a medical device used in spinal surgery. These devices provide support and stability to the spine following certain procedures. They help individuals with various spinal conditions by addressing structural issues.
What is a Spinal Cage?
A spinal cage is a small, hollow implant used in spinal fusion procedures. It is shaped to fit within the space between two vertebrae after a damaged disc is removed. The device maintains correct height and alignment between spinal bones. As a spacer, the cage restores natural disc height, which can alleviate pressure on nearby nerves.
The design includes porous surfaces or openings that encourage bone growth through and around the device. This structural support stabilizes the spinal segment. The cage acts as a framework, preventing vertebrae from collapsing or moving excessively.
Materials and Designs
Spinal cages are manufactured from various biocompatible materials. Common materials include titanium, polyetheretherketone (PEEK), and carbon fiber. Titanium is a strong, lightweight metal known for its biocompatibility and ability to promote bone ingrowth, though its radiopacity can obscure post-operative imaging. PEEK, a polymer, offers strength and elasticity similar to natural bone, which may contribute to even load distribution and better fusion rates, while also being radiolucent for clearer imaging. Carbon fiber is another strong and lightweight option.
Cage designs vary for different surgical approaches and anatomical needs. Some are cylindrical and may be threaded for insertion, while others are box-shaped or crescent-shaped. Newer innovations include expandable cages, inserted in a compact form and then expanded within the disc space to achieve optimal fit and restore spinal curvature. These designs and materials allow surgeons to select the most appropriate cage for each patient.
Why Spinal Cages are Used
Spinal cages are implanted to address conditions causing instability or pain. Degenerative disc disease, a common reason, involves the breakdown of discs between vertebrae, leading to pain and reduced function. Spinal stenosis, a narrowing of spaces around the spinal cord and nerves, can also be treated with cages, as they decompress nerves by restoring disc height.
Spondylolisthesis, where one vertebra slips over another, benefits from cage implantation to stabilize the segment. Spinal instability following disc removal, trauma, or deformity also makes a patient a candidate. Restoring disc space expands natural openings for spinal nerves, reducing nerve compression and pain. This restoration of height and stability alleviates symptoms and improves overall spinal function.
The Role of Spinal Cages in Fusion
Spinal cages play a significant role in spinal fusion, which aims to create a solid bone bridge between adjacent vertebrae. The cage itself does not directly fuse the spine; instead, it functions as a spacer and a scaffold. Once the damaged disc is removed, the cage is inserted into the empty space, providing immediate structural support and maintaining intervertebral height.
Bone graft material is packed inside and around the hollow interior of the cage. This bone graft, from the patient’s body (autograft), a donor (allograft), or synthetic materials, contains cells and proteins that promote new bone growth. Over several months, new bone cells grow through the cage’s openings and integrate with the bone graft, forming a solid fusion that permanently joins the two vertebrae. This process eliminates movement at the affected segment, contributing to long-term stability and pain relief.