How to improve the mechanical safety of a novel spinal implant while saving costs and time

Abstract

Background: Spinal implant failure is associated with prolonged patient suffering, high costs for the medical device industry, and a high economic burden for the health care system. Pre-clinical mechanical testing has great potential to reduce the risk of such failure. However, there are no binding regulations for planning and interpretation of mechanical testing. Therefore, different strategies exist. Mainly for novel implants an option is to start with a structured scientific literature search that forms an objective background for the definition of an implant-specific test plan, the derivation of acceptance criteria and interpretation of the test results.

Methods: This paper describes, how a literature-based approach can look like from the initial literature search through the derivation of the test plan and the acceptance criteria, to the final test result evaluation and how this approach can support the proof that the device meets all necessary safety and performance standards.

Results: The main advantage of this literature-based approach is that testing and test result interpretation are linked with the loads acting on the individual implant in vivo. In an ideal case, testing is focused on the individual implant in a way that ensures maximum efficiency during the development and approval process combined with maximum insight in safety and effectiveness of the implant. Even comparative implant testing may become obsolete, which is a big advantage if comparative implant and related data are not available.

Conclusion: This approach to pre-clinical mechanical testing offers the potential to create a chain of arguments, from literature review through testing to the interpretation of test results. This methodology can significantly enhance testing efficiency, reduce risk of failure, and ultimately prevent unnecessary patient suffering and healthcare costs. By synthesizing scientific insights with regulatory requirements, this review aims to guide clinicians and researchers in improving patient care and advancing device technologies.

Keywords: approval; biomechanical testing; implant; mechanical safety; mechanical testing; performance; predicate device; risk‐analysis; spine.

FIGURE 1

Step 1 of the literature‐based approach to proof the mechanical safety of a spinal implant: Summary of the in vivo loading of the relevant spinal region and the implant under consideration of the intended use of the implant and human factors.

FIGURE 2

Examples of two different screw trajectories: Pedicle screw (black), cortical screw (blue). Modified according to Verma et al. There are different preferences among surgeons, however, whether these preferences have any effect on mechanical safety has not yet been clarified.

FIGURE 3

Examples how human factors could be addressed in pedicle screw testing according to the ASTM F1717 standard. Left: Screw orientation horizontal (standard) versus upward/downward pointing; Right: Polyaxial screw in line with screw axis (standard) or inward rotated.

FIGURE 4

Step 2 of the literature‐based approach to proof the mechanical safety of a spinal implant: Derivation of a mechanical test plan based on the in vivo loading conditions and taking into consideration the specific function of the implant, available test standards and custom test methods.

FIGURE 5

Step 3 of the literature‐based approach to proof the mechanical safety of a spinal implant: Derivation of acceptance criteria for each single test described in the test plan. This derivation is based on the in vivo loading as summarized in step 1.

FIGURE 6

Step 4 of the literature‐based approach to proof the mechanical safety of a spinal implant: Selection of the worst‐case sizes and designs of the implant for each single test described in the test plan.

FIGURE 7

Step 5 of the literature‐based approach to proof the mechanical safety of a spinal implant: Assessment of the test results.

FIGURE 8

Structure of a literature‐based approach to proof the mechanical safety of a spinal implant.

FIGURE 9

Mechanical testing must be accompanied by safety considerations in various other areas (representative topics).