Retrieval analysis in total knee arthroplasty

Table 1 Metrology tools to investigate the root cause of implant failure

Qualitative methods	Quantitative methods
Visual investigation	Semi-quantitative methods, such as Hood, Goldberg and other visual scoring systems
Microscopic investigation	Gravimetric method
SEM	AFM
EDS	VSI
XRD	Coronal and sagittal plane radiographs
Spectroscopy: AES, XPS, Raman spectroscopy, FTIR	2D-CT
-	3D-CT
-	SPECT

SEM: Scanning electron microscopy; EDS: Energy dispersive X-ray spectroscopy; XRD: X-ray diffractometry; AES: Auger electron spectroscopy; XPS: X-ray photoelectron spectroscopy; FTIR: Fourier transform infrared spectroscopic; AFM: Atomic force microscopy; VSI: Vertical scanning interferometer; 2D-CT: Two-dimensional computed tomography; 3D-CT: Three-dimensional computed tomography; SPECT: Single-photon emission computerized tomography.