Ligamentous Augmentation to Prevent Proximal Junctional Kyphosis and Failure: A Biomechanical Cadaveric Study

Area of Science:

• Spine biomechanics
• Spinal instrumentation
• Surgical techniques

Background:

• Proximal junctional kyphosis (PJK) is a complication of spinal fusion, linked to stiffness mismatch between fused and unfused segments.
• Current understanding of PJK etiology highlights the need for biomechanical evaluation of methods to mitigate proximal junctional failure.
• The effect of polyethylene band placement on proximal junctional biomechanics remains understudied.

Purpose of the Study:

• To biomechanically assess the efficacy of polyethylene bands in reinforcing the cephalad unfused segment of spinal fusion constructs.
• To evaluate the impact of polyethylene bands placed around the spinous process (SP) or spinal lamina (SL) on reducing junctional stress.
• To investigate the potential of polyethylene bands to enhance construct strength and prevent proximal junction failure.

Main Methods:

• A biomechanical cadaveric study involving 12 fresh frozen specimens.
• Three groups were tested: control (T10-L5 instrumentation), SP group (T10-L5 with a polyethylene band to T9 SP), and SL group (T10-L5 with two bands to T9 SL).
• Specimens underwent eccentric loading to failure, with load-to-failure analyzed using linear regression.

Main Results:

• All specimens experienced fractures.
• The spinous process (SP) group demonstrated a higher mean peak load to failure (2148 N) compared to the control group (1248 N) and spinal lamina (SL) group (1390 N), though not statistically significant (P > 0.05).
• No significant differences were observed in fracture level or net kyphotic angulation among the groups.

Conclusions:

• Ligament augmentation using polyethylene bands attached to the spinous process (SP) showed a trend towards increased load-to-failure in a cadaveric model of proximal junctional kyphosis (PJK).
• While statistical significance was not achieved, these findings suggest that SP augmentation may offer biomechanical benefits in preventing proximal junction failure.
• Further research is warranted to confirm the clinical efficacy of this augmentation technique in mitigating PJK.