Mobile- vs. fixed-bearing total knee replacement

Figures & data

Figure 1. CONSORT 2010 flow diagram.

Table 1. Baseline demographics. Values are mean (range)

	Fixed bearing (n = 23)	Mobile bearing (n = 23)
Weight, kg	87 (67–119)	80 (60–104)
Height, cm	171 (155–183)	170 (160–185)
BMI	30 (23–39)	27 (23–34)
Age, years	66 (56–73)	66 (54–75)
Sex (M/F)	14/12	9/15
OP side (right/left)	12/14	14/10
Implant size	4 (2.5–5)	3 (2.5–5)
Knee flexion, degrees	119 (77–144)	117 (77–144)
Extension defect, degrees	3 (0–11)	5 (0–11)
Range of motion, degrees	116 (88–144)	112 (88–144)
Anterior-posterior stability^a, mm	3 (0–5)	3 (0–5)
Medial-lateral stability^a, mm	2 (0–5)	2 (0–5)
Femorotibial angle^a, degrees	5 (2–9)	4 (1–10)

^apostoperatively.

Figure 2. DXA scans showing implant detection, bone borders, and regions of interest (ROIs). A. Anterior/posterior view. B. Lateral view.

Figure 3. 2-year RSA results. Error bars show SD.

Table 2. Migration results at 24 months

	Fixed bearing (n = 23)				Mobile bearing (n = 23)
	x	y	z	TT/TR	x	y	z	TT/TR	p^a
Translation, mm
Mean	0.09	0.06	0.26	0.30	0.06	0.08	0.11	0.17	0.04
SD	0.06	0.05	0.22	0.22	0.07	0.06	0.09	0.09
Min	0.03	0.00	0.01	0.05	0.00	0.00	0.01	0.03
Max	0.34	0.22	0.73	0.76	0.32	0.20	0.33	0.34
Rotation, degrees
Mean	0.58	0.44	0.10	0.83	0.27	0.53	0.09	0.67	0.1
SD	0.46	0.35	0.08	0.43	0.24	0.48	0.10	0.45
Min	0.00	0.03	0.01	0.22	0.01	0.03	0.00	0.12
Max	1.64	1.71	0.26	1.81	0.87	2.01	0.38	2.04

TT: total translation; TR: total rotation.

^ap-value for FB versus MB in total translation or total rotation.

Table 3. Percentage BMD change between baseline, 12-month follow-up, and 24-month follow-up

	Anterior/posterior images			Lateral images
	12 months	p	24 months	p	12 months	p	24 months	p
Fixed bearing (n = 23)
All ROIs	-2.3	0.02	-1.1	0.4	-11.5	< 0.01	-4.1	0.1
ROI1	-2.3	< 0.01	-0.9	0.5	-11.0	0.06	-2.4	0.5
ROI2	-2.9	0.03	-3.3	0.2	-17.0	< 0.01	-5.2	0.07
ROI3	-1.7	0.3	0.9	0.6	-9.2	0.7	-4.8	0.5
Mobile bearing (n = 23)
All ROIs	-8.8	0.04	-0.8	0.4	-11.8	< 0.01	-6.2	< 0.01
ROI1	-8.5	< 0.01	-2.1	0.3	-16.5	< 0.01	-10.4	< 0.01
ROI2	-11.9	0.06	-2.0	0.2	-12.8	< 0.01	-6.8	0.1
ROI3	-7.0	0.2	1.9	0.6	-10.8	0.2	-1.5	0.3

ROIs: regions of interest.

Figure 4. Oxford knee score (min = 12, max = 48). Error bars show SD.