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Proximal Junctional Kyphosis (PJK) | Diagnosis, Management, and Prevention

Introduction

PJK or forward bending (Kyphosis) of the spine at the upper end of spinal fusions, is not uncommon after spine surgery in adult patients. The rate varies between 17% - 46%. Most cases occur within 2 years of surgery. Two-third of cases occur within the first 3 months of surgery.

Most cases do not need revision surgery. Patients with this problem have results like those without it. Surgery may be required due to marked kyphosis, pain, poor self-image, or weakness of limbs.

The average cost of revision surgery has been estimated at $77,432. Failure at the thoracolumbar junction was more common and more likely due to fracture. Failure at the upper thoracic region was more likely due to soft-tissue failure.

Risk Factors
  • Older age may indicate poor bone quality, or poor soft tissue strength. Old age may itself not be a risk factor.
  • Bone quality has not been determined to be a risk factor.
  • Upper Level
    • Conflicting data exists for selecting the correct upper level. It seems to occur at higher rate at the lower thoracic level. However, extending the construct higher also increases the risk of failure and weakness in limbs. 
  • Combined Anterior-Posterior/Posterior Surgery
    • Combined approach was also found to be a risk factor. Preservation of ligaments and muscle may have an effect in patients undergoing posterior surgery. The number of levels fixed using the anterior approach may play a role.
    • The current existing data does not address these details.
  • Extension of Instrumentation to the Sacrum
    • Most studies show an increase in the rate of PJK in patients with fusion to the sacrum. This may be due to more rigidity of the construct.
  • Proximal Implants
    • The use of hooks rather than screws at the upper level has been advised by some surgeons.
    • Use of transition rods may create a less rigid construct.
    • The material of the rod can also have an effect on the rigidity of the construct. The use of titanium alloy, which is less stiff, has a lower rate of PJK compared to cobalt chrome.
  • Ligaments and Muscular Tissues
    • The removal of posterior ligaments above the upper level greatly increased the risk.
    • The posterior tethers create a steadier change in the range of motion at the upper level.
    • Minimally invasive surgery may avoid damage to posterior ligaments and muscles. But, a clear benefit of this method has not been shown.
  • Cement Support
    • Support at upper vertebrae alone did not reduce the risk of fractures. However, support at both upper vertebrae and upper vertebrae plus one did reduce the risk of fractures.
    • No clear benefit with long term follow-up has been shown.
  • Postoperative Alignment
    • Achieving ideal post-operative alignment has been reported to have a lower incidence of deformity.

“Overcorrection” can also lead to deformity, especially in the older age group.

Conclusion

PJK is a common problem after the surgery for adult spinal deformity. We have found several risk factors for the development of this problem. Some solutions have been suggested. The solutions focus on pre-operative planning, alignment, and steps to augment the upper level fixation.

There is not enough data at this time to suggest one solution that can prevent this problem.

Tips for Decreasing the Incidence of Deformity
  • Improve Bone Mineral Density before the surgery.
  • Aim for age-based alignment goals.
  • For patients with preoperative thoracic kyphosis >40˚ consider including the thoracic spine in the planned fusion.
  • Use of hooks in place of screws at the upper level.
  • Use of transition rods with the smaller diameter at the upper levels.
  • Shape the rod into a gentle kyphosis at the upper end of the construct.
  • Consider cement support mainly when upper vertebrae is in the TL spine.
  • Avoid injury to posterior ligaments, capsules, and muscles at the upper level.
  • Posterior Tethers may play a role, but longer-term clinical studies are needed.

Summary provided by the SRS Patient Education Committee