Exploring the importance of track, torque, and distal force testing in medical device development.
Overview
Track testing is a critical component of medical device testing used to evaluate how effectively interventional devices navigate complex, tortuous anatomies. Track, torque, and distal force testing work together to provide a comprehensive, reproducible framework for assessing device performance, informing design decisions, and reducing clinical risk. By simulating real-world conditions and capturing key performance metrics, these methods help bridge the gap between engineering and real-world clinical application. The newly released TTS1000 provides unmatched reliability for track testing of medical devices.
The advancement of minimally invasive therapies depends on the ability of devices to traverse complex vascular pathways safely and efficiently.
Unlike static mechanical components, intravascular devices are subject to constant interaction with dynamic biological systems. Variability in patient anatomy and operator technique further complicates performance expectations.
To mitigate these challenges, medical device developers rely on bench testing frameworks that replicate key aspects of clinical use.
Among the most widely adopted testing frameworks are:
- Track Testing: Track testing assesses a device’s ability to advance smoothly through tortuous geometries such as human vasculature.
- Torque Testing: Torque Testing evaluates rotational response and control fidelity of a device.
- Distal Force Measurement: Measuring distal force is a way of quantifying forces applied by the distal end of a device during navigation.
When paired with a reliable track testing system such as Harland Medical’s TTS1000, these methods provide a reproducible and objective foundation for design optimization, regulatory submission, and physician
confidence.
Track Testing in Tortuous Paths
Trackability is a critical attribute for medical devices which are designed to navigate the body’s complex vascular system. These devices must advance smoothly through tortuous geometries that include sharp bends, variable vessel diameters, and branching angles, often under challenging clinical conditions.
Using a bench model designed to replicate these anatomies, engineers can evaluate a device’s ability to maintain forward motion with minimal resistance, binding, or deformation.
By measuring push force, advancement smoothness, and resistance across standardized pathways, developers gain insights into how design features such as shaft stiffness gradients, lubricious coatings, and tip flexibility impact performance.
Importantly, these models also simulate worst-case anatomies, helping identify potential failure modes such as kinking, buckling, or binding before they arise in vivo.
Why Trackability Matters
Clinically, improved trackability of a medical device reduces procedure time, minimizes vessel trauma, and decreases the likelihood of device exchange. From a physician’s perspective, better trackability enhances confidence in the device’s predictability and control.
In this way, track testing in tortuous paths provides both a rigorous engineering evaluation and a practical proxy for real-world usability, bridging the gap between bench design and clinical application.
Testing methodology: Devices are advanced through anatomically representative bench models, often incorporating variable curvatures, bifurcations, and stenoses. Measurements focus on push force, advancement smoothness, and resistance encountered.
Clinical relevance: Improved trackability reduces procedure time, limits trauma to vessel walls, and decreases the likelihood of device exchange.
Design implications: Data can inform shaft stiffness gradients, lubricious coatings, and tip flexibility. Risk mitigation: Identifies potential kinking, buckling, or binding before clinical studies.
Physician perspective: Provides insights into handling, repositioning, and procedural workflow.
Worst-case modeling: Pathway designs often incorporate exaggerated curvatures to simulate difficult patient anatomies and ensure robust device design.
Torque Testing of Medical Devices
The purpose of torque testing is to ensure proximal rotational input translates predictably to distal motion and that the device can withstand worst-case rotational loads without kinking, coiling, or structural failure.
Torque response (functional behavior): Effective torque response ensures that proximal operator input translates accurately to distal device movement. Without precise transmission, operators face reduced control, longer procedures, and higher risk of vessel injury. A critical hazard is in-line “whip” — when distal response lags during rotation and then releases abruptly, producing a transient spike in torque. Whip undermines predictability and can elevate local stresses at the vessel wall.
Methodology: Apply controlled angular displacements proximally while measuring distal angle and torque. Capture torque efficiency, phase/temporal lag, hysteresis, and whip events (identified as rapid torque spikes and overshoot). Use high-rate data acquisition to detect transient spikes and quantify their magnitude and decay.
Clinical relevance: High fidelity with minimal lag and absence of whip supports precise steering in tortuous or microvascular targets, reducing unintended tip motion and vessel trauma.
Design levers: Material selection, braid/coil geometry (pick count, wire diameter), shaft layering, and lubricious liners/jackets to balance torque transmission with flexibility and damping to mitigate whip.
Torque strength testing (test-to-failure)
Torque strength is the device’s maximum rotational capacity before yield, kinking, coiling, delamination, or fracture.
Methodology: Conduct monotonic torsion ramp at a controlled angular rate to failure; optionally add stepload holds and cyclic torsion fatigue at clinically relevant amplitudes. Document failure mode and location.
Key outputs: Ultimate torsional strength (N·mm), yield torque, rotations to failure, safety factor versus expected clinical loads, and post-test patency/track integrity.
Clinical relevance: Adequate torque strength ensures the device tolerates difficult lesion crossing and severe tortuosity without catastrophic failure, minimizing procedure interruptions and retrieval risks.
Design levers: Reinforcement at transitions and joints, braid/coil architecture, bonding/adhesive coverage, heat-set profiles, and jacket/lumen reinforcement to lift yield and delay kink/coil onset without sacrificing deliverability.
Distal Force Measurement
The distal tip of a device is the primary point of interaction with the vasculature. Distal force measurement involves measuring axial and radial forces, which is essential to ensuring that devices can cross lesions and maintain stability without imposing undue stress on fragile vessel walls.
Testing methodology: Specialized systems record tip forces during advancement, withdrawal, and deflection. Both static and dynamic forces are evaluated.
Clinical relevance: Excessive force may cause vessel dissection or perforation, while insufficient force limits the device’s ability to traverse occlusions or remain stable during deployment.
Design implications: Optimizing force profiles helps achieve an appropriate balance between pushability and atraumatic navigation.
Reproducibility of Track Testing for Medical Devices
The value of any bench test lies in its reproducibility. Reproducible testing enables meaningful comparisons across devices, prototypes, and generations. It also ensures confidence in regulatory and clinical review.
Standardization: Adherence to ISO and ASTM standards promotes consistency across laboratories.
Comparative analysis: Reproducible data enables benchmarking against competitor devices and historical baselines.
Design iteration: Repeatable results provide clear feedback loops, allowing engineers to evaluate incremental changes with confidence.
Track testing, torque testing, and distal force measurement form a complementary framework for evaluating the performance of interventional devices. When executed with reproducibility and within clinically relevant anatomical models, these tests provide actionable insights that accelerate development, improve safety, and enhance physician usability.
As regulatory expectations and clinical demands evolve, rigorous bench testing will remain a cornerstone of medical device innovation, supporting both patient safety and competitive differentiation.
If accuracy and reproducibility are the at the top of the requirements list for a new machine, the TTS1000 from Harland Medical is the top option on the market.
Reach out to Harland to learn more about the system.
