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Home > Non-union of Spinal Bones in Fusion Surgery: Part I – Causes

Non-union of Spinal Bones in Fusion Surgery: Part I – Causes

Jeffrey R. Carlson, MD CPEJeffrey R. Carlson, MD, MBA, CPE, FAOOS

Spinal fusion surgery is performed to stabilize the spinal column by promoting the fusion of adjacent vertebrae. Successful fusion depends on the formation of a bony bridge between two or more spinal vertebrae, which provides stability and eliminates motion at the affected spinal segment. It also alleviates pain caused by conditions such as degenerative disc disease, spinal stenosis, or spondylolisthesis.

While fusion success rates are generally high, non-union, or failed fusion, remains a significant concern in a subset of patients. Non-union occurs when the bones fail to heal and fuse as intended, leading to persistent pain, instability, and potential revision surgery. Understanding the causes and treatment options for non-unions are important for optimizing patient outcomes.  It remains one of my top concerns in dealing with patients post-operatively.

Several factors can contribute to the non-union of spinal bones following fusion surgery. The following are some of the primary causes:

  1. Patient-related factors:
    • Age: Older patients have reduced bone healing capacity, increasing the risk of non-union.
    • Smoking/Vaping/Marijuana: Nicotine and other components of tobacco impair bone healing by reducing blood flow and interfering with cellular function. Patients who smoke anything or use nicotine-containing products have a higher risk of developing non-union following spinal fusion surgery.
    • Obesity: Excessive weight puts additional stress on the fusion site, hindering bone healing
    • Malnutrition: Undernutrition, particularly protein undernutrition, contributes to the occurrence of osteoporotic fracture, by lowering bone mass and altering muscle strength. Medical complications after fracture can also be increased by nutritional deficiency.
  2. Surgical factors:
    • Inadequate stabilization: Insufficient internal fixation hardware or improper surgical technique (inadequate surgical preparation, improper placement of instrumentation, or insufficient decortication of bone surfaces) can impede the fusion process by leading to mechanical instability.
    • Poor bone quality: Osteoporosis or other bone disorders compromise bone quality, impeding successful fusion.
    • Infection: Surgical site infections contribute to non-union by disrupting the healing process by decreasing blood supply, causing tissue damage, inflammation, and promoting bone resorption, which leads to non-union.

In the next installment of this series, I’ll talk about non-union for spinal fusion cases.  There are a variety of options for treatment and it’s not a one-size-fits-all therapeutic plan – I have to adjust what I recommend according to my patient’s age, bone health and overall condition.

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