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The Sternum Saw (also commonly called a Sternal Saw or Bone Saw) is a specialized power surgical instrument designed for one primary purpose: to safely and precisely cut through the sternum (breastbone) during a surgical procedure called a median sternotomy.
Here's a detailed introduction:
Primary Purpose: Median Sternotomy
This is the most common approach for open-heart surgery (like coronary artery bypass grafting - CABG, valve replacements) and major thoracic procedures.
Accessing the heart, lungs, and major blood vessels requires dividing the sternum down the middle.
Design & Mechanism:
Reciprocating Blade: The defining feature. The blade moves rapidly back-and-forth (reciprocates) in a straight line, like a tiny jigsaw. This is distinct from oscillating saws (which move in a small arc) often used for bone elsewhere.
Power Source: Typically powered by:
Compressed Air (Pneumatic): Most common in operating rooms, offering high power, reliability, and ease of sterilization.
Electricity (Battery or Corded): Increasingly common, offering greater mobility and quieter operation, especially battery-powered versions.
Blade: Features sharp, fine teeth specifically designed for cutting dense cortical bone like the sternum. Blades are single-use, sterile, and disposable.
Depth Control & Safety: Crucial features include:
Depth Stops/Guards: Prevent the blade from plunging too deep after cutting through the sternum, protecting the underlying heart, lungs, and major vessels (mediastinum).
Blade Guard/Shoe: A flat plate that slides under the sternum or rests against it, guiding the blade and acting as the depth stop.
Ergonomics: Designed for the surgeon to hold securely and maneuver precisely along the sternum's length.
How It's Used:
Preparation: The patient is positioned supine. The skin and tissues over the sternum are incised.
Positioning: The blade guard/shoe is carefully slid under the lower tip of the sternum (xiphoid process) or positioned centrally.
Cutting: The surgeon activates the saw and steadily guides it upwards along the midline of the sternum, from the bottom (xiphoid) to the top (suprasternal notch). The reciprocating blade cuts efficiently through the bone.
Hemostasis: Bleeding from the bone edges is controlled (e.g., with bone wax or electrocautery).
Retraction: A sternal retractor is inserted to hold the two halves of the sternum apart, providing wide access to the chest cavity.
Closure: After the procedure, the sternum is closed using strong stainless steel wires looped around or through the bone halves and twisted tight.
Key Advantages:
Precision: Allows a clean, straight cut down the midline.
Speed: Cuts through dense sternal bone much faster than manual saws.
Safety: Integrated depth stops/guards significantly reduce the risk of injuring vital underlying structures compared to unguarded saws.
Efficiency: Essential for the timely execution of complex cardiac and thoracic surgeries.
Sterilization:
The handpiece (motor unit) is designed for repeated sterilization (autoclaving) after each use.
The blade is always single-use, sterile, and disposable to prevent infection and cross-contamination.
Safety Critical:
Using a sternum saw requires significant skill and training. Proper positioning of the guard and steady control during the cut are paramount to avoid catastrophic complications.
Understanding the anatomy beneath the sternum is essential.
In summary: The sternum saw is a vital, highly specialized surgical tool enabling safe and efficient access to the chest cavity for life-saving cardiac and thoracic surgeries. Its reciprocating blade mechanism combined with critical depth safety features makes it the instrument of choice for performing the median sternotomy.
