3D Printed Caps to Protect Chronic Cranial Implants in Rhesus macaques (Macaca mulatta)

Chronic neurophysiology studies using Rhesus macaques (Macaca mulatta) often require implanting cranial hardware, including headposts, recording chambers, and screws. Unfortunately, a macaque’s instinct to scratch and groom around these cranial devices has the potential to result in retraction of skin from implant margins, chronic inflammation, and regional or even systemic infections that negatively impact animal well-being and can sometimes necessitate early removal from the study. Current literature on chronic cranial implant care primarily advocates topical treatments, which may exacerbate these scratching and grooming behaviors. To address these challenges, we tested the use of 3D printed caps designed to protect cranial implants. These caps aim to mitigate the adverse effects associated with these undesirable behaviors by providing a detachable physical barrier that does not interfere with research objectives. We designed and developed 3D printed head caps that securely attach to a headpost, covering cranial implants and surrounding tissue margins. With a carbon fiber 3D printer, we created more durable caps and connector pieces that are also autoclavable. Caps are secured to the headpost using two screws that are easily removed prior to each chaired recording session. These caps can prevent the animal from physically interacting with cranial implants, improving surgical healing in the short term, and preventing potential complications over extended periods.