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Spine Fusion

  • Spine fusion is a surgical procedure that causes 2 or more vertebral levels to be joined with solid bony healing in the spine.
  • It is performed to correct spinal instability from traumatic, degenerative, or iatrogenic causes and to prevent spinal deformity progression.
Over the last 2 decades, the incidence of spinal fusion in the United States has more than doubled in the adult population .
Risk Factors
  • Diabetes mellitus leads to increased risk of infection in patients undergoing spine fusion.
  • Diabetes mellitus or tobacco use leads to high rates of pseudarthrosis (nonunion).
  • Spinal fusions often are indicated for:
    • Congenital scoliosis
    • Idiopathic scoliosis
    • Spondylolisthesis
    • Degenerative scoliosis
    • Spinal fractures
    • Postsurgical instability
Signs and Symptoms
  • Plain radiographs are used to assess the adequacy and maturation of a spinal fusion.
    • The presence of continuous bridging bone over the fusion site is the best evidence of a well-healed fusion.
  • When failure to heal (pseudarthrosis) is suspected, the following are indicated:
    • CT scan
    • 3D reconstructions of a CT scan
    • Conventional radiographs, often with flexion and extension views
General Measures
  • Success of an individual fusion depends on:
    • Patient age
    • Surgical technique
    • Use of bone graft
    • Patient’s nutritional status
    • Patient’s smoking status: Cigarette smoking can increase the rate of pseudarthrosis by up to 8-fold.
Special Therapy
Physical Therapy
  • Physical therapy helps increase walking ability and improve aerobic conditioning.
  • It is not required after spinal fusion.
  • Individual surgeon preference
  • The choice of surgical approach (anterior or posterior) depends on the requirements of an individual case (e.g., the need for correction of rigid versus flexible deformities or the need to decompress neural elements).
  • Fusion can be facilitated by combining instrumentation techniques (e.g., pedicle screws, pedicle hooks, sublaminar wires) and various types of bone graft (e.g., local, iliac crest, rib, fibula, or allograft).
  • During the 1st year after spinal fusion surgery, patients require follow-up with the treating surgeon every 2-3 months for healing assessment.
  • Once solidly healed, patients should be followed every few years to monitor for developing pseudarthrosis or problems related to early degenerative changes at levels adjacent to the fused levels.
  • The prognosis varies greatly, depending on:
    • Diagnosis
    • Smoking status
    • Surgical technique
  • Patients with impending litigation and those injured at work tend to have less favorable results than patients without these conditions.
  • Depending on the indications for surgery:
    • Failure to return to normal function
    • Pseudarthrosis
  • Depending on the surgical technique:
    • Pseudarthrosis rates of 10% are not uncommon in the literature, but not all pseudarthroses are painful or require treatment.
    • Spinal fusion increases load and stresses at levels adjacent to the fusion, a situation that can lead to an increased rate of early degeneration at the junctional levels.
    • Neurologic injury
Patient Monitoring
  • Activity:
    • For 6 weeks after surgery (during healing and maturation of the fusion), patients often have activity restrictions, which vary from surgeon to surgeon.
    • By 6 months after surgery, most patients are released to unlimited activities, but most physicians advise against high-impact activities such as running, downhill skiing, and lifting heavy weights.
  • Follow-up care:
    • In general, bone is the slowest healing tissue in the human body, but it has the ability to heal completely without a scar.
    • Healing of the spinal fusion is similar to fracture healing.
      • Spinal instrumentation and appropriate immobilization limit the local motion, which allows a fusion to heal.
      • In adults, it takes up to 6 months for a fusion to become solid and up to 2 years for it to attain full strength.
      • In children, bone heals more rapidly, and full fusion strength can occur in 6-12 months.
Patient Teaching
  • Spinal fusion predisposes to additional spinal difficulties.
  • Generalized total body fitness, avoiding smoking, and preventing osteoporosis are important factors for minimizing these problems.
Q: How are spinal fusions obtained?
A: Spinal fusions occur as a result of the process of incorporating bone graft between adjacent spinal segments while maintaining a stable spinal segment, often with spinal instrumentation.
Q: What are 2 factors that increase the rates of pseudarthrosis (nonunion) after a spine fusion.
A: Diabetes mellitus and smoking.

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