Sternum Breakdown After Heart Surgery

Wound and Bone Healing Problems, Causes of Non-Union, and Complications

Key Takeaway:
Sternal breakdown after cardiac surgery is a rare but serious complication, leading to impaired wound and bone healing, increased risk of infection, chronic pain, respiratory dysfunction, and significantly higher healthcare costs. Prevention and early intervention are critical to improving patient outcomes.

Introduction

Sternum breakdown, or sternal dehiscence, is a major complication following median sternotomy—the standard approach for most open-heart surgeries. This article explores the mechanisms behind sternal breakdown, the challenges of wound and bone healing, the reasons for bone non-union, and the spectrum of possible complications. PubMed links are provided throughout to support the discussion of clinical outcomes and economic impact.

1. Mechanisms and Prevalence of Sternum Breakdown

Sternal breakdown refers to the failure of the sternum to heal properly after being split during heart surgery. This can manifest as:

• Mechanical separation (dehiscence)
• Non-union of the bone
• Deep sternal wound infection (DSWI)
• Mediastinitis (infection of the mediastinum)

Incidence:

• Sternal dehiscence occurs in 0.2–5% of cardiac surgeries (https://pubmed.ncbi.nlm.nih.gov/30993919/) (https://pubmed.ncbi.nlm.nih.gov/29522306/).
• DSWI rates range from 0.3% to 2% (https://pubmed.ncbi.nlm.nih.gov/13129420/).

Key Risk Factors:

• Advanced age, high BMI, diabetes, COPD, smoking, use of both internal thoracic arteries, redo or emergency surgery, and poor nutritional status (https://pubmed.ncbi.nlm.nih.gov/29522306/) (https://pubmed.ncbi.nlm.nih.gov/13129420/).

2. Problems with Wound Healing

Biological and Clinical Challenges

• Poor Blood Supply: The sternum’s vascularity is compromised, especially when internal mammary arteries are harvested for bypass grafts (https://pubmed.ncbi.nlm.nih.gov/12558231/).
• Mechanical Stress: Coughing, obesity, and inadequate fixation can disrupt healing .
• Comorbidities: Diabetes, obesity, COPD, immunosuppression, and renal insufficiency all impair healing (https://pubmed.ncbi.nlm.nih.gov/23355648/).

Clinical Outcomes

Common Pathogens:
Staphylococcus aureus, Staphylococcus epidermidis, Enterococcus, Klebsiella, and Pseudomonas (https://pubmed.ncbi.nlm.nih.gov/30069187/).

3. Bone Healing and Causes of Non-Union

Biology of Sternal Bone Healing

• Osteogenesis and Angiogenesis: Bone healing requires new bone formation and blood vessel growth, both of which are impaired by poor vascularity and comorbidities (https://pubmed.ncbi.nlm.nih.gov/3105195/).
• Mechanical Stability: Instability at the sternal edges leads to micromotion, inhibiting bone healing and promoting fibrous tissue (non-union) (https://pubmed.ncbi.nlm.nih.gov/31711516/).

Causes of Non-Union

Definition:
Sternal non-union is persistent pain, instability, or clicking at the sternum for more than 3–6 months post-surgery, in the absence of infection (https://pubmed.ncbi.nlm.nih.gov/31711516/).

4. Complications of Sternal Breakdown

Major Complications

• Mediastinitis and Deep Sternal Wound Infection:
  Life-threatening, with mortality rates up to 35% in some series (https://pubmed.ncbi.nlm.nih.gov/7742429/).
• Chronic Pain and Functional Limitation:
  Up to 10% of patients report persistent pain; functional impairment is common, especially after multiple interventions (https://pubmed.ncbi.nlm.nih.gov/31711516/).
• Respiratory Dysfunction:
  Instability impairs chest wall mechanics, increasing risk of pneumonia and respiratory failure (https://pubmed.ncbi.nlm.nih.gov/37637509/).
• Reoperation and Prolonged Hospitalization:
  Non-union and infection often require further surgery, increasing length of stay and costs (https://pubmed.ncbi.nlm.nih.gov/15511452/).
• Long-Term Disability and Reduced Quality of Life:
  Especially in patients with infectious complications or multiple revisions (https://pubmed.ncbi.nlm.nih.gov/29522306/).

Economic Impact

• Hospital Costs:
  Sternal wound complications can nearly triple hospital costs, increasing expenses by up to $62,000 per patient (https://pubmed.ncbi.nlm.nih.gov/26371410/).
• Resource Utilization:
  Advanced wound care, multiple surgeries, and long-term antibiotics are often required (https://pubmed.ncbi.nlm.nih.gov/26557476/).

5. Summary Table: Key Data Points

6. PubMed Links for Further Reading

• Complications in cardiac surgery: factors contributing to sternal dehiscence (2010–2014)
• Complications of cardiac surgery: sternal dehiscence after median sternotomy (1990–2009)
• Deep sternal wound infection after cardiac surgery: Evidences and controversies
• Wound complications after median sternotomy: a single-centre study
• Increase in calcidiol level is associated with improved sternal bone healing after cardiac surgery with sternotomy-REINFORCE-D trial results
• Risk analysis of deep sternal wound infections and their impact on long-term survival
• Sternal fixation and autologous bone grafting for post sternotomy non-union: a case series

Conclusion

Sternal breakdown after heart surgery is a rare but devastating complication, driven by a combination of mechanical, biological, and patient-related factors. It leads to impaired wound and bone healing, non-union, and a cascade of complications including infection, chronic pain, respiratory dysfunction, and increased healthcare costs. Early identification of high-risk patients, meticulous surgical technique, and aggressive management of complications are essential to improve outcomes and reduce the burden of this serious complication.

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