Orthopaedic and Rehabilitation Devices Panel
Of the Medical Devices Advisory Committee
November 21, 2002
Draft Questions
(Revised 11/12/02)

SPINE
In January of 2000, the FDA issued The Guidance Document for the Prepareation of IDEs for spinal systems. Prior to its issuance, ORDB presented a preliminary background document to the Orthopaedic and Rehabilitation Devices Panel. Durint the October 8, 1998 panel meeting, input was received from panel members and the public which resulted in the current guidance document. At that time, the FDA requested some input on Non-Fusion devices which are not intended to facilitate fusion of the spine. Unlike fusion devices, these devices allow some functional motion through the various levels of the spine. These include devices that provide stability while continuing to allow some percentage of normal or functional motion, devices which allow motion and growth, and devices which stabilize vertebral body and spine fracture repair. Examples of these types of devices are included in the references enclosed in this panel package.

The current spinal guidance focuses primarily on spinal fusion devices for various etiologies, with brief guidance on such non fusion devices as vertebral body replacements and disc replacement devices. While the FDA Guidance for Spinal Implant 510 (k)s issued September 27, 2000, outlines in detail devices intended for fusion and there is a voluntary testing standard available for pedicle screw systems and intervertebral body fusion devices (i.e., ASTM F1717 and ASTM 2077, respectively), many sponsors use modified versions to address different types of spinal systems. Because there are testing standards in development, the FDA has advised sponsors to contact appropriate standards bodies (e.g., ASTM, ISO) for additional information. As the scope of spinal devices expands, the FDA recognizes the need to update the spinal guidance to include additional clarification and suggestions for preclinical testing, clinical assessments, endpoints and success determinations related to emerging spinal technologies.

I. Preclinical Questions

 
  

1. Currently, the FDA Guidance for Spinal Implant 510(k) s, which extensively covers devices intended for fusion, recommends various static and fatigue testing for spinal devices. Because devices not intended for fusion are intended to stabilize the spinal motion segment and retain functional motion, they must be designed to last for the lifetime of the individual rather than until a fusion occurs. Therefore, the current testing requested for devices intended for fusion and non-fusion may not be adequate. The FDA currently requests the following testing for spinal devices:

Fusion devices (devices intended to stabilize by fusing motion segments, e.g., pedicle screw systems, intervertebral fusion devices, vertebral body fusion devices, etc.)

These are the current recommendations by the FDA for testing of these types of devices.

 
    

2. The FDA is currently recommending that any device in the area of the spinal cord and nerve roots, that has the potential to generate debris, be tested for neurotoxicity. For those incorporating new materials (e.g.., polymers, composites, etc.) or designs, both fusion and non fusion, the FDA recommends that manufacturers perform wear simulations and fatigue tests to evaluate the potential for the device to generate wear debris. The FDA believes the wear debris generated from these tests should be collected and characterized. For those devices where toxicity may be an issue, the FDA suggests two options to evaluate neurotoxicity:

  • Injection study of various sized particles into the spinal cord area of small animals
  • Functional animal models

Because of the limitations of the current testing methods and models, should devices made of new materials and/or those intended to retain motion be tested for neurotoxicity independent of the type of material or the amount of wear debris generated? If you suggest that testing be performed, please describe the testing you recommend. For example,

  • Discuss viability and usefulness of injection animal study including amount and distribution of sizes and shapes of wear debris should be injected in the animal in predicting what may occur clinically for the life of the implant;
  • Discuss recommendations, viability and usefulness of functional animal models in predicting what may occur clinically for the life of the implant; or
  • Discuss alternatives.

II. Clinical Questions

1. For spinal assemblies not intended to fuse motion segments (Non-fusion spinal devices, e.g., disc replacement devices, nucleus replacement devices, joint replacement, spinal stabilization without fusion, etc.), the goals of treatment may be to stabilize the spine, maintain “normal/functional” motion, treat disease early in its course to prevent further progression and to conserve motion instead of fusing segments of the spine to alleviate pain and restore function. These types of devices provide challenges in choosing the best methods to evaluate safety and effectiveness.

Our current Spinal Guidance describes methods to assure that data collected provide adequate characterization of the safety and effectiveness of devices. These sections suggest appropriate patient inclusion and exclusion criteria (Section 4 and 5), effectiveness evaluations (Section 8: 8.1-8.4) safety evaluations (Section 9) and patient and study success criteria (Section 10). The FDA believes that the populations and goals of treatment may be different for devices that maintain functional motion. Therefore:

a. Please discuss study designs which may be better suited to evaluate Non-Fusion spinal devices. In your discussion, please comment on:

i. enrollment criteria,
ii. patient populations,
iii. controls,
iv. success criteria and
v. goals of the study
that would be suitable for these types of Non-fusion spinal devices

b. Devices intended to stabilize the spine yet retain functional motion are expected to have an upper limit of motion beyond which one would consider the device to be unstable and a lower limit below which one would consider the device to have inadequate motion or possibly even consider the segment to be fused. Please discuss the amount of motion and on what scale, to define a patient as a functional and clinical success (i.e., a clinically significant improvement in condition) for each of cervical, thoracic and lumbar levels for Non-Fusion spinal devices.