Radiography is the most used and cost-effective diagnostic tool that can distinguish different body tissues based on an X-ray photon attenuation. It is a very versatile tool for the examination of hard tissue, such as bone and teeth, and for a routine check after orthopedic implant placement mostly made of metals. Bone healing, inflammation at the implant interface, and implant position can be assessed by comparing the degree of radiodensity in the two-dimensional (2-D) radiogram. The difference in the radiodensity level can indicate the formation of degradation products in relation to the tissue reaction toward degradation of a metal implant. A high radiodensity value is commonly found for iron implants as it highly absorbs the X-ray energy, making a radiopaque image , while a low radiodensity is found for magnesium implants related
Figure 2.6 Digital radiogram of different metal implants on a mice femur: (a, d) stainless steel, (b, e) porous tantalum, (c, f) porous iron, and (g) their corrected total intensity. Star, implant; circle, bone; broken red line, analysis area “line plot profile” using software of ImageJ; red triangle, implant analysis area; and yellow line triangle, background analysis area.
Adapted from Noviana D, Estuningsih S, Ulum MF. Animal study and pre-clinical trials of biomaterials. In: Mahyudin F, Hermawan H, editors. Biomaterials and medical devices: a perspective from an emerging country. Cham: Springer International Publishing; 2016. p. 67-101.
to hydrogen gas evolution surrounding the implant . However, radiographic analysis is mostly qualitative and is limited to resolution at the microscopic level. Additional tools such as a densitometer to read the radiograph, especially for implant sizes smaller than 1 mm, and image processing software can enhance the assessment at the peri-implant area, as illustrated in Fig. 2.6.