During open heart surgery, surgeons split the sternum (breastbone) straight down the middle using a specialized power saw in a procedure called a median sternotomy. The cut runs the full length of the bone, from the small notch at the top of your chest down to the pointed tip at the bottom. More than 750,000 of these procedures are performed in the United States each year, making it one of the most common bone cuts in all of surgery.
The Incision Before the Bone
The surgeon doesn’t go straight to bone. You’re lying face up under general anesthesia, and the first cut is through skin, typically 7 to 9 centimeters long for minimally invasive approaches or longer for standard procedures. That skin incision runs along your midline, starting a few centimeters below the sternal angle (the slight ridge you can feel about a third of the way down your breastbone).
After the skin, the surgeon works through several layers: subcutaneous fat, the fascia (a tough connective tissue sheet), and finally the periosteum, which is the thin membrane that wraps the bone itself. Each layer is opened carefully along the midline. The soft tissues are pulled back to expose the full length of the sternum, including the suprasternal notch at the top and the xiphoid process, the small cartilage tip at the bottom.
How the Bone Is Actually Cut
The sternum is divided with a sternal saw, a handheld power tool that looks somewhat like a small reciprocating saw you might find in a workshop, but engineered for precision and safety. The most common type is an oscillating saw, whose blade vibrates rapidly side to side rather than plunging up and down. This oscillating motion gives the surgeon precise, perpendicular division of the bone while making it easier to control how deep the blade goes. The surgeon can feel when the blade passes through the back wall of the bone (the posterior sternal table), which helps protect the structures directly behind it.
The cut goes right down the center of the sternum, splitting it into two equal halves. This is important because the sternum is a flat, relatively thin bone, and directly behind it sits the pericardium (the sac around the heart), major blood vessels, and sometimes lung tissue that has adhered to the back of the bone from prior surgery. The oscillating saw’s controlled depth is what makes it safer than older reciprocating designs, particularly in patients undergoing a second or third operation where scar tissue may have glued the heart closer to the bone.
Once the sternum is split, a chest retractor (called a Finocchietto retractor) is placed between the two halves and cranked open. This spreads the ribcage apart, creating a wide window to the heart. The surgeon then opens the pericardium with a vertical incision and places traction sutures to hold it open.
Full Sternotomy vs. Mini-Sternotomy
Not every open heart surgery requires splitting the entire bone. For certain procedures, particularly aortic valve replacements, surgeons may perform a mini-sternotomy. This involves a shorter skin incision (6 to 8 centimeters) and a partial cut through the sternum, typically extending from the second rib down to the fourth intercostal space. The bone is only partially divided, often in a J-shape or T-shape, leaving the lower portion intact.
Mini-sternotomy causes less trauma, keeps the chest more stable, produces a smaller scar, and generally speeds up healing with lower rates of the bone separating afterward. The tradeoff is a more limited view of the surgical field, which makes it unsuitable for complex procedures like coronary artery bypass grafting or surgeries involving multiple valves. Patients with chest deformities like scoliosis or pectus excavatum are also typically excluded from the mini approach.
How the Bone Is Put Back Together
Closing the sternum is just as critical as opening it. The standard method uses stainless steel wires: at least six wires are threaded around or through the bone, then twisted tight to hold the two halves firmly together. The wiring pattern varies by surgeon preference, but the goal is even compression across the full length of the sternum. These wires stay in permanently and are visible on chest X-rays for the rest of your life.
A newer approach uses rigid plate fixation, where titanium plates are screwed directly into the bone with self-drilling screws that grip both the front and back surfaces of the sternum. One plate is placed on the manubrium (the broad upper portion) and two on the sternal body. Rigid plates provide more mechanical stability than wires alone, which matters especially for patients at higher risk of the bone separating, such as those with diabetes, obesity, or osteoporosis.
Some centers also apply a biocompatible bone cement between the two halves before wiring. This adhesive is mixed during surgery and applied as a thin layer to each half of the sternum, adding mechanical strength to the standard wire closure. Studies have found that this combination accelerates healing, reduces postoperative pain, and improves quality of life compared to wires alone.
How Long the Sternum Takes to Heal
Most patients experience significant improvement within 4 to 6 weeks, though complete bone healing takes closer to 10 weeks on average. Chest pain or soreness commonly persists for 8 to 12 weeks after surgery. Some patients develop chronic pain or, rarely, nonunion where the bone fails to fully fuse.
The major complications to watch for are sternal dehiscence (the bone separating) and mediastinitis (a deep infection in the chest cavity). These are uncommon: mediastinitis occurs in roughly 0.34% of cases and dehiscence without infection in about 0.55%. Both are serious when they happen, often requiring a return to the operating room.
Recovery Restrictions After the Cut
Because the sternum needs weeks of stable healing, you’ll face specific lifting and movement restrictions. The exact limits vary by hospital, but the general range gives you the idea: some programs restrict you to no more than 5 to 10 pounds for the first four weeks, while others allow up to 10 pounds for six weeks or up to 20 pounds for six to eight weeks. Pushing, pulling, and any motion that forces the two halves of the sternum apart (like pushing yourself up from a chair with both arms) are restricted during this window.
You’ll also be told to avoid driving for several weeks, partly because of the lifting restriction on the steering wheel and partly because a sudden stop with a seatbelt could stress the healing bone. Sleeping on your back is recommended to avoid pressure on the chest. Most people return to normal daily activities within 6 to 8 weeks, though full recovery with no restrictions typically takes closer to 12 weeks.
Pain Control After Sternotomy
The bone cut itself is a significant source of postoperative pain. Standard pain management includes oral and intravenous medications, but regional nerve block techniques are increasingly used to target the pain more directly. A continuous parasternal block, where a local anesthetic is delivered through small catheters placed alongside the sternum, can reduce the need for stronger systemic painkillers. Epidural infusions placed in the upper spine are another option that provides effective chest wall pain relief, though they carry their own risks and aren’t used universally. Pain management approaches are still evolving, and what you’re offered will depend on your surgical team’s protocols.