Protective cranial implant caps for macaques

Abstract

Background: Neuroscience studies with macaque monkeys may require cranial implants to stabilize the head or gain access to the brain for scientific purposes. Wound management that promotes healing after the cranial implant surgery in non-human primates can be difficult as it is not necessarily possible to cover the wound margins.

New method: Here, we developed an easily modifiable head cap that protects the sutured skin margins after cranial implant surgery and contributes to wound healing. The protective head cap was developed in response to monkeys picking at sutured skin margins around an implant, complicating healing. The user-friendly protective cap, made from Klarity- R™ Sheet (3.2 mm thick with 36 % or 42 % perforation) is affixed to the implant post-surgically. Once secured and while the monkey is still anesthetized, the plastic sheeting is molded around the implant. The protective head cap restricts the monkey's finger access to its' wound margins while allowing air to circulate to promote wound healing.

Results and comparison with existing methods: Across two UK primate facilities, the protective head cap promoted wound healing. In monkeys that did not wear the head cap, re-suturing was necessary in ∼30 % of cases. In contrast, none of the monkeys that wore the head cap required re-suturing. The monkeys wearing the head cap also had reduced numbers of days of prescribed antibiotics and analgesia.

Conclusion: This bespoken, easily adaptable, protective head cap supports postoperative wound healing, and enhances the welfare of monkeys involved in neuroscience research.

Keywords: Behavior; Cognition; Macaca mulatta; Neuroimaging; Neurophysiology; Neuroscience; Non-human primate; Primate chair; Welfare; Wound management.

Fig. 1

Photographs showing top (A, B) and underside (C) views of a smaller protective head cap used to cover the wound margins for a head post only implant in Oxford. In these images, the protective head cap, with a green colored anchor securely molded into the Klarity plastic sheeting (see Methods) will be used with an MRI compatible headpost designed from Rogue Research/ Hybex.

Fig. 2

(A) Image showing anchor designed by Rogue Research/ Hybex. The anchor was developed to allow easier handling of the head cap while the awake monkey is sitting (neckplated) in its primate chair during postoperative checks (i.e. the anchor allows to secure the head cap to the monkey’s head post attachment used to head fix the monkey). The anchor has the same design as the head post, in this example, an MRI compatible headpost. Rogue Research/ Hybex can make an anchor for any type of headpost design. (Bi and Bii) Figures showing how anchor slots into the headpost attachment at the top, while the base of the anchor slots onto the top of the headpost. (C) Photo showing a bespoke protective head cap molded around the anchor system with the front of the head cap molded to accommodate two chambers implanted into the monkey’s skull.

Fig. 3

Schematic images showing how the anchor is molded round the Klarity sheet of the MRI compatible headpost (A and Ai) or the titanium headpost (B and Bi) and how the headpost attachment is used to attach to the anchor of the head cap for removal and replacement while the monkey is sitting (awake) neckplated in its primate chair. (C) Photograph of monkey sitting in primate chair (neckplated) wearing the head cap with it affixed to the headpost attachment, ready for removal.

Fig. 4

(A) Photo showing suggested sizes (scale bar = 10 mm) and relative proportions for the different pieces of the head cap. (B) Photos showing the creation process of the cap, (Bi) the smooth shape the cap should have to avoid irritation on the animal’s skin, and (Bii and Biii) the overlapping of the sheets, necessary to have a strong and secure cap. (C) Photos showing the screw holes necessary to hold the cap to the headpost.

Fig. 5

Photographs showing the bespoke protective head cap affixed to the headpost of the anesthetized monkey.

Fig. 6

The number of days the monkeys across the two institutions were prescribed (A) analgesia (typically a course of non-steroidal anti-inflammatory drugs), and (B) antibiotics after surgical implants in the group of monkeys that did not have the protective head cap fitted after the procedure and the group of monkeys fitted with the protective head cap after the procedure.