Surgical Screws: Purpose, Types, Insertion Procedure, and Recovery

How are surgical screws put in?

Surgical screws are meticulously implanted into bone to stabilize fractures, fuse joints, or attach soft tissues, following a precise, multi-step orthopedic procedure designed to optimize healing and restore anatomical function.

Understanding the Purpose of Surgical Screws

Surgical screws, typically made from biocompatible materials like stainless steel or titanium, are fundamental tools in orthopedic surgery. Their primary function is to provide internal fixation, holding bone fragments together securely while the body's natural healing processes take over. This stability is crucial for proper bone union (osteosynthesis) and allows for earlier mobilization, which is vital for preventing muscle atrophy and joint stiffness. They are used in various scenarios, including:

• Fracture Fixation: Stabilizing broken bones in limbs, spine, and joints.
• Arthrodesis (Joint Fusion): Permanently joining two bones, often to alleviate pain from severe arthritis.
• Osteotomies: Holding bone segments after a surgical cut designed to correct alignment.
• Ligament/Tendon Reattachment: Anchoring soft tissues to bone.

Types of Surgical Screws

Orthopedic surgeons select specific screw types based on the bone's density, the fracture pattern, and the biomechanical demands of the repair:

• Cortical Screws: Designed for dense cortical bone, featuring fine, shallow threads along their entire shaft for maximum purchase.
• Cancellous Screws: Used in softer, cancellous (spongy) bone, characterized by coarse, deep threads, often only on the distal portion.
• Cannulated Screws: Hollow along their length, allowing them to be inserted over a guide wire for precise placement, particularly useful in minimally invasive procedures.
• Locking Screws: Used with locking plates, they thread into the plate as well as the bone, creating a fixed-angle construct that offers enhanced stability, especially in osteoporotic bone.
• Bioabsorbable Screws: Made from polymers that gradually dissolve in the body over time, eliminating the need for removal surgery.

The Surgical Procedure: A Step-by-Step Overview

The process of inserting surgical screws is a highly technical procedure requiring precision, anatomical knowledge, and specialized instrumentation.

Pre-operative Planning

Before surgery, comprehensive planning is essential. This includes:

• Imaging: X-rays, CT scans, and sometimes MRI are used to precisely map the fracture, assess bone quality, and determine the optimal screw trajectory and length.
• Patient Assessment: A thorough medical evaluation ensures the patient is fit for surgery and anesthesia.
• Surgical Strategy: The orthopedic surgeon meticulously plans the approach, incision location, and specific implants to be used.

Anesthesia and Positioning

The patient is administered appropriate anesthesia (general or regional) and carefully positioned on the operating table to allow optimal access to the surgical site while maintaining patient safety and comfort.

Incision and Exposure

An incision is made through the skin and underlying tissues to expose the fractured bone or joint. The size and location of the incision depend on the specific anatomical site and the complexity of the procedure, ranging from small percutaneous punctures for cannulated screws to larger open approaches.

Reduction of the Fracture/Joint

This critical step involves realigning the bone fragments (reduction) to their anatomical position. This may involve manual manipulation, specialized clamps, or external traction. Proper reduction is paramount for optimal healing and restoration of function.

Drilling the Pilot Hole

Once the bone fragments are perfectly aligned, a drill bit, precisely matched to the diameter of the screw being used, is employed to create a pilot hole through the bone. This hole guides the screw and prevents bone cracking during insertion. For cannulated screws, a guide wire is first inserted under fluoroscopic (real-time X-ray) guidance, and then the cannulated drill bit is passed over the wire.

Measuring Screw Length

After drilling, a depth gauge is inserted into the pilot hole to accurately measure the required screw length. This ensures the screw is long enough to provide adequate purchase in the bone but not so long that it protrudes excessively or damages surrounding structures.

Tapping (Optional but Common)

For many screw types, especially in dense cortical bone, a tapping instrument (a tool with threads matching the screw) is used to pre-cut threads into the pilot hole. This reduces the force required for screw insertion, minimizes bone stress, and ensures a secure fit, particularly important when inserting non-self-tapping screws. Self-tapping screws have a cutting flute at their tip that creates threads as they are inserted, often eliminating the need for pre-tapping.

Screw Insertion

The surgical screw is then carefully placed into the prepared hole using a specialized screwdriver. The surgeon applies controlled pressure and rotation to advance the screw, ensuring it engages the bone threads securely. The screw is tightened to the appropriate torque, providing stable fixation without over-compressing or stripping the bone.

Confirmation

Throughout the procedure, and especially after screw insertion, fluoroscopy (real-time X-ray imaging) is frequently used to confirm the correct position and length of the screws and the proper alignment of the bone fragments. This immediate feedback helps ensure surgical accuracy.

Closure

Once the screws are securely in place and confirmed, the surgical site is irrigated to remove debris, and the incision is closed layer by layer using sutures, staples, or surgical glue. A sterile dressing is applied.

Post-operative Care and Recovery

Following screw insertion, post-operative care is crucial for successful healing. This typically involves:

• Pain Management: Medications to control discomfort.
• Immobilization: Bracing or casting may be used to protect the repair, though internal fixation often allows for earlier movement.
• Rehabilitation: Physical therapy is often initiated early to restore range of motion, strength, and function. The specific rehabilitation protocol depends on the location and nature of the injury and the stability of the fixation.
• Monitoring: Regular follow-up appointments with X-rays track bone healing. In some cases, screws may be removed once the bone has fully healed, particularly if they cause irritation or are no longer needed.

Potential Complications

While generally successful, surgical screw insertion carries potential risks, including infection, nerve or blood vessel damage, screw loosening or breakage, non-union (failure of the bone to heal), malunion (healing in an incorrect position), and allergic reactions to implant materials.

In conclusion, the precise insertion of surgical screws is a cornerstone of modern orthopedic surgery, enabling stable internal fixation that facilitates the body's natural healing processes and helps patients regain mobility and function after musculoskeletal injuries.