Discussion on Large Animal Spinal Implant Surgical Models in Medical Devices

2024-07-25

Preclinical experiments involving implantation in large animals are frequently conducted for medical devices. In particular, the surgical models used for spinal implantation are known to be more complex compared to other experiments. Let’s delve deeper into this topic and continue our discussion here. #### I. Implantation of Pedicle Fixation Products Many spinal orthopedic products involve the implantation at the pedicle site. During the testing process, pedicle operations are also performed in animal models. Large animals that can accommodate spinal fixation implants generally include pigs, dogs, and sheep. Due to anatomical differences, sheep and pigs are the preferred choices for pedicle operations. For example, pedicle screws can be implanted into the lumbar vertebrae of pigs to verify their stability and extraction force. Postoperative CT imaging reveals that due to the choice of screw length, the implant has not fully entered the vertebral body.  *CT image post-implantation* From the CT image post-implantation, we can observe that the implant does not completely enter the vertebral body due to the chosen screw length. In subsequent tests, screws of appropriate length and diameter can be selected for the experiment. As the diameter of the pedicle in animals is generally smaller than that in humans, smaller screws are sometimes utilized for testing.Upon pathological dissection, it can also be observed that the screw avoids the vertebral canal and is primarily implanted along a reasonable pedicle trajectory. #### II. Spine Navigation Products Experiment Currently, the R&D projects of navigation products for spinal operations are increasing on the market, used for intraoperative guidance in spinal surgery.  *In the testing of such products, sheep are generally used as the experimental animals.*  *Based on the data measured during surgery, models are created for calculation to obtain a reasonable needle insertion path and angle.*  *Traditional radiography is also used during the study for real-time fluoroscopy to verify the rationality of puncture guidance.* #### III. Artificial Bone Products Testing New material artificial bones are generally tested in rabbits for spinal fusion studies. In general, autogenous iliac bone is also used as a control in this study. After separation of the ilium, autogenous bone is prepared.  *Bilateral dissection is conducted on the rabbit's lumbar vertebrae to expose the transverse processes for bone graft fusion. After the bone graft fusion, imaging examinations are performed on the animals at appropriate time points to assess the fusion effect.* #### IV. Study on Spinal Nerve-related Products Spinal Nerve-related Product Evaluation Studies on neurostimulation generally aim to verify the long-term safety of the implant and the effectiveness of certain functions.In terms of animal selection, sheep or pigs are generally selected. The main consideration is whether the epidural space inside the vertebral canal can accommodate the size of the implant.  *Taking sheep as an example, procedures are performed on appropriate vertebrae, followed by implantation into suitable segments. Postoperatively, behavioral observations of the animals are conducted, along with imaging evaluations to assess whether the implant is in the predetermined position and its associated neurostimulation functions.* #### V. Conclusion The aforementioned discussion elucidates various large animal models employed in spinal experiments for medical devices, encompassing common test items. As the number of related test products amplifies, novel experiments will be tailored for animal models in alignment with customer testing needs. Through rigorous experimental studies, we endeavor to efficiently complete test projects with precision and accuracy, ensuring the swift market entry of your products and consequently benefiting a greater number of patients. WuXi AppTec Medical Device Testing Center, your trusted partner, is committed to enhancing patient healthcare and quality of life.

Brain implantation test of medical devices

2021-11-23

The international organization for stand...

Have we identified the extractables and leachables (E & L) of medical devices correctly?

2021-10-10

With the promulgation and implementation of the new version of iso10993-18:2020 on the chemical characterization of medical device materials in the risk management process and the public solicitation of cmde in June 2020 for the guiding principles for the review of the establishment of evaluation methods and characterization techniques for unknown leachables of medical devices (Exposure Draft) Opinions issued a notice that combining the chemical characterization and toxicological risk assessment of medical devices with the biological evaluation of biocompatibility test results has become a new trend in the development of biosafety evaluation of medical devices. E & L research in medical devices will soon become an indispensable part of the whole process of product R & D, registration and application. Due to the complex material composition and production process of some medical devices, the types and quantity of E & L produced are extremely large. It is estimated that there are tens of thousands of kinds, and the content of these chemicals in the extraction solution is small, which poses a big problem for the identification of chemicals. In the process of E & L research using various technologies of chemical characterization of medical devices, mass spectrometry, especially high-resolution mass spectrometry, can infer the molecular formula of compounds by using accurate molecular weight, which provides a practical idea for E & l work. At the same time, there are also some difficulties in the structural analysis of chemical substances based on mass spectrometry. If there is no participation of professional mass spectrometry analysts in the implementation process, the identification work is very prone to errors.