No association between serum metal ions and implant fixation in large-head metal-on-metal total hip arthroplasty

Figures & data

Table 3. Translations (mm) and rotations (°) for cups and stems at 5-year follow-up

Variable	Translations cups (n = 36)				Translations stems (n = 39)				Rotations cups (n = 36)				Rotations stems (n = 39)
Axis	X	Y	Z	TT ^a	X	Y	Z	TT ^a	X	Y	Z	TR ^b	X	Y	Z	TR ^b
Mean	–0.06	0.46	–0.33	1.21	0.05	–0.08	–0.27	0.79	–0.88	0.46	–0.74	2.63	0.07	0.96	–0.17	1.99
SD	0.89	0.47	0.86	0.74	0.33	0.55	0.65	0.53	1.78	1.78	1.47	1.71	1.24	1.94	0.31	1.53
Minimum	–1.68	–0.50	–3.53	0.26	–0.64	–1.84	–2.38	0.17	–6.89	–3.79	–3.76	0.35	–2.26	–2.85	–0.76	0.36
Maximum	1.98	1.60	0.95	3.88	0.64	0.82	1.05	2.57	2.99	5.59	2.57	8.91	3.76	6.67	0.59	7.11

^a The total translation was calculated using the 3-D Pythagorean theorem (TT = √(x² + y² + z²).

^b The total rotation was calculated using the 3-D Pythagorean theorem (TR = √(x² + y² + z²).

Figure 1. Box plots of total translations (mm) in cups and stems at the 1-, 2-, and 5-year follow-up. The line in each box marks the median, the box shows the interquartile range, and the whiskers show the tenth and ninetieth percentiles.

Figure 3. Total translations (TTs) for all individuals at the 1-, 2-, and 5-year follow-up.

Figure 4. Dichotomized total translation (TT) for stems and cups between the second and the fifth year. Patients who had migrations above the precision limit of the method are represented on the right side of the plots, and patients with elevated serum metal ion concentrations are marked with red dots. The TT precision limit was 0.45 mm for stems and 0.76 mm for cups. 1 patient had both cup and stem migrations with TT above the precision limits (denoted 1)