Introduction 

​

As spinal fusion techniques continue to evolve, the focus has increasingly shifted toward innovations in interspinous fixation devices (IFDs, particularly their design and mechanical reliability. In patients suffering from conditions such as lumbar spinal stenosis, degenerative disc disease, or spinal instability, these devices offer a LESS invasive alternative to pedicle screw constructs, reducing muscle disruption, operative time, and recovery periods. 

​

Yet not all interspinous devices are created equal. A recent biomechanical study—"Advancing the design of interspinous fixation devices"—sheds light on how subtle differences in design parameters can have a major impact on performance, durability, and patient outcomes. 

​

​

Study Objectives 

​

The research team led by Chin et al. set out to compare the biomechanical efficiency of interspinous fixation devices with different: 

• Locking Mechanisms: Dual-locking set screws vs. single-locking set screws 

• Plate Designs: Symmetrical vs. asymmetrical configurations 

​

​

Their aim was to determine how these variations affect spinal stability, construct integrity, and the overall efficacy of fusion support during post-operative healing. 

 

Locking Mechanism Matters: Dual vs. Single Set Screws 

​

One of the most significant insights from the study was the superior biomechanical stability offered by dual-locking set screw mechanisms. Devices equipped with two points of fixation (i.e., a set screw on each side of the interspinous plate) demonstrated: 

• Reduced micro-motion between vertebral levels, which is critical for promoting bony fusion 

• Higher resistance to axial loading and shear forces, which helps prevent device migration 

• Improved torsional stability, thereby lowering the risk of post-operative loosening 

​

​

In contrast, single-locking devices showed a greater propensity for rotational instability and slippage under repetitive loading conditions, conditions that mimic daily patient activities like bending, twisting, or lifting. 

Implication: In real-world surgical scenarios, a dual-locking design could translate to fewer complications, better fusion rates, and more predictable outcomes. 

 

Plate Geometry: Symmetry Leads to Stability 

​

The study also examined how the geometry of the lateral plates influences device function. Devices with symmetrical plate designs offered the following advantages: 

• Uniform stress distribution across the spinous processes 

• Balanced load sharing between left and right components 

• Enhanced compatibility with a wider variety of spinal anatomies 

​

​

On the other hand, asymmetrical plate designs, while sometimes used to fit complex anatomical variations, showed inconsistent load bearing. This could lead to stress concentrations, increased risk of fatigue failure, or asymmetric bone remodeling over time. 

​

Implication: Symmetrical designs improve mechanical predictability and reduce the risk of spinous process fracture or asymmetric fusion development. 

​

​

Clinical Significance 

​

Why do these findings matter? 

​

For spine surgeons and device developers, this study provides an evidence-based blueprint for designing next-generation interspinous fixation systems. In a market increasingly driven by patient centric, LESS invasive solutions, the right design can offer substantial advantages: 

• Reduced need for posterior hardware such as pedicle screws 

• Outpatient surgery potential due to shorter operative times 

• Lower revision rates, preserving bone and soft tissue integrity 

• Faster recovery and less postoperative pain for patients 

​

​

Inspan by KIC Ventures: Bridging the Gap Between Research and Real-World Performance 

​

One interspinous fixation device that embodies these principles is Inspan, developed by KIC Ventures. 

Why Inspan aligns with the study’s findings: 

​

✅ Dual-Locking Mechanism: Inspan features a bilateral locking set screw system that ensures a robust grip on the spinous processes, enhancing construct rigidity. 
✅ Symmetrical Plate Design: The implant’s symmetrical geometry promotes even load distribution and conforms to natural spinal anatomy. 
✅ Fusion + Decompression: Inspan is FDA-cleared for both fusion and decompression, one of the few devices that bridge both therapeutic objectives. 
✅ LESS Invasive Delivery: It can be placed via a small posterior incision in an outpatient setting, reducing patient morbidity and hospital costs. 

​

​

The Verdict?

​

The future of spinal fusion is headed toward devices that are smarter, simpler, and biomechanically superior, and Inspan is leading that charge. 

​

​

Source: https://pmc.ncbi.nlm.nih.gov/articles/PMC11467278/