A Removable 3D-Printed Protective Cap for Chronic Cranial Implants in Rhesus macaques (Macaca mulatta): A Descriptive Case Series and Technical Refinement

Chronic neurophysiology studies in Rhesus macaques (Macaca mulatta) require implantation of cranial hardware including headposts, recording chambers, and fixation screws. A common complication is persistent picking, scratching and grooming around implant margins, which can result in skin retraction, chronic inflammation, infection, repeated surgical repairs, and premature removal of the animal from research studies. Existing implant-care protocols rely heavily on topical therapies that may inadvertently increase grooming behavior. We developed a removable carbon fiber 3D-printed cranial cap that attaches directly to the headpost, covering the implant margins while allowing airflow and rapid removal during recording sessions. Three macaques received the protective 3D-printed cap. One animal tolerated the device for 836 days, during which implant manipulation ceased, surgical repair frequency decreased, and an additional 1056 h of electrophysiological data were collected. A second animal successfully used the 3D-printed cap during postoperative healing for 61 days following implant revision surgery. One animal did not tolerate the 3D-printed cap, and it was removed. This case study suggests that a simple, low-cost 3D-printed cap has the potential to improve wound healing, reduce implant manipulation, enhance animal welfare, and prolong the functional lifespan of chronic cranial implants in appropriately selected animals.