Fig. 1

The schematic details, chemical composition and metallography observation of intervertebral fusion device. a The schematic details of cervical spine fusion surgery and dimension recorded for intervertebral fusion device. Asterisk: intervertebral fusion device (cage). For the present study, the experimental cage was similar configuration to that of EIT Cervical Cage (Natural Bone Ingrowth with EIT Cellular Titanium^®; EIT Emerging Implant Technologies GmbH, Tuttlingen, Germany) and was produced using the Renishaw AM 400 system (UK). The representative images of samples from each batch are shown; with the dimensions of 15 mm in width, 9 mm in height, and 13 mm in length. All samples show a similar level of porosity. There are non-melted surface powder particles visible on the sides of the pores which indicates insufficient melting during laser beam movement. The centerline average roughness (Ra) was 10–30 μm, pore size 500-600 μm, and the porosity ratio was 55%. b Chemical Composition and Metallography Observation. Metallographic organizations presented such as attached photos. The metallographic structure of the sample showed acicular structure without obvious grain display. After hot isostatic pressing treatment, the acicular structures become wider and less sharp. HIP treatment: − (without hot isostatic pressing); HIP treatment: + (with hot isostatic pressing)