Efficacy of Sub-laminar and/or Interspinous Tethers to Prevent Proximal Junctional Kyphosis After Surgical Correction of Adult Spinal Deformity

Condition(s) studied

Investigational drug(s) / intervention(s)

Tether strategy: During spine surgery sub-laminar or interspinous bands are utilized in combination with standard posterior rigid instrumentation (i.e. screws and metallic rods). They are typically implanted at the upper vertebral level, above the cranial screws, and then connected to the rods. Their implantation is based on standard surgical techniques for spine surgeons.

Reference: Patient will undergo the spine surgery as the standard of care, using only standard posterior rigid instrumentation (i.e. screws and metallic rods).

Study summary

PJK (proximal junctional kyphosis) at the upper end of spinal fusions after surgical correction of adult spinal deformity is not uncommon. Two-thirds of cases are observed within the first 3 months after surgery and 80% within the first 18 months. PJK is consequently a common problem after surgery for adult spinal deformity, representing one of the most frequent complications following this kind of procedure. Although the first-line treatment of this event is conservative, surgery may be necessary in around 30-40% of cases. Revision surgery generally consists of extending the posterior spinal instrumentation.

Prophylactic vertebroplasty has been proposed to reduce the risk of PJK and PJF, with promising results but with the limitation of reinforcing only the bony structures, with no action on the soft tissues. In this context, some authors have reported that the use of tethers, creating a transitional zone at the upper end of the construct between the fused and the non-instrumented spine, could reduce the occurrence of this complication (PJK). One of the hypotheses is that the use of a topping-off system results in a transitional zone reducing stresses at the junctional spine and may reduce the occurrence of both PJK and the need for reoperation.

Compared with other topping-off systems, such as hooks, the surface of contact provided by the bands on the posterior arches is much greater and the primary stability much better. In addition, the risk of malposition is extremely low.

The aim of this study is therefore to compare the occurrence of PJK and PJF in patients for whom tethers were implanted at the upper end of the instrumentation versus patients for whom no tether system was used.

In a retrospective study conducted in the neurosurgery department of the HCL on 38 patients undergoing multilevel spine instrumentation with junctional tethers, PJK occurred in 8 of them (21%) after 24 months of follow-up.

Eligibility

Primary outcome measure(s)

• Sub-laminar and/or interspinous tethers efficacy to prevent PJK — From enrollment to 24 months post-surgery
  Percentage of patients with PJK during the first post-operative 24 months with PJK defined as : * a proximal junctional sagittal Cobb angle (PJA) between the lower endplate of uppermost instrumented vertebra (UIV) with screws and the upper endplate of 2 supra-adjacent vertebra ≥15 * a 15° delta between 24months post operative PJA and preoperative PJA These 2 parameters will be assessed by an independent committee using radiographic images preop and 24 months postop

Trial sites (6)

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