Cosmetic and radiological outcome following the use of synthetic hydroxyapatite porous-dense bilayer burr-hole buttons

Background. Cranial neurosurgical procedures utilising burr-holes lead to development of cosmetically unacceptable puckered scars on the scalp over burr-hole sites. Ceramics, especially Hydroxyapatite (HA) are good bone substitutes owing to their biocompatibility and osteoconduction i.e. ability to lay down bone over the implant by fibrovascular invasion and later bone formation. The Sree Chitra Tirunal Institute for Medical Sciences and Technology in India has pioneered research in this direction and has developed a unique porous-dense bilayer HA burr-hole button. This study evaluates the safety, cosmetic effect, as well as the radiological outcome following implantation of these bilayer HA buttons. Method. Sixty-five HA buttons were implanted in 22 patients who underwent cranial neurosurgical procedures at the Sree Chitra Tirunal Institute for Medical Sciences and Technology. We assessed the cosmetic outcome (absence of puckered scar over burr hole sites, absence of allergic reactions or infections associated with the implant) as well as the radiological outcome with X-rays at specified intervals and looked for interference in the postoperative neurological imaging due to the implants. Results. There were no adverse events related to the HA buttons in the form of allergic reactions or infections. The implants persisted as radio-dense opacities on skull X-rays of recipients for up to two years. It did not lead to artefacts on postoperative CT or MR imaging of the brain. In particular, the HA buttons could be subtracted on Digital Subtraction Angiography and did not obstruct visualisation of the cerebral vasculature. Conclusion. The bi-layer porous-dense HA buttons are useful in preventing cosmetic defects over burr-hole sites on the scalp after cranial neurosurgical procedures. It does not interfere with current radiological imaging methods in the postoperative phase.