Table 4.

Marginal cost analysis in € (euros) for polyethylene wear analysis by EGS-RSA and with PolyWare as used in this study. For easy comparison, the staff costs are listed per patient

Cost area	EGS-RSA a	PW2 b	PW1 c
Investment costs (1 time)
Additional X-ray equipment	80,604	0	0
Calibration box	10,075	0	0
A3 transparency scanner	0	5,165	0
Software	34,595	510	510
Education of radiographer	1,542	0	0
Education of research assistant	6,166	1,542	1,542
Total investment costs	132,982	7,217	2,052
Staff costs per patient
Radiographer	35	12	12
Research assistant	102	77	39
Total staff costs per patient	137	89	51

^a EGS-RSA: radiostereometric analysis of PE wear using sphere models (2 stereo radiographs were used).

^b PW2: PolyWare PE wear analysis using the postoperative and final follow-up plain radiographs.

^c PW1: PolyWare PE wear analysis using only the final radiographic follow-up plain radiographs.