Low BMD affects initial stability and delays stem osseointegration in cementless total hip arthroplasty in women

Figures & data

Figure 1. Study design.

Table 1. Demographic data

No. of cases	39
Age, years	64 (41–78)
BMI, kg/m ^2	31 (SD 6)
Previous fractures	8
Systemic BMD
normal bone	12
osteopenia	22
osteoporosis	5
Dorr classification
type A	21
type B	18
type C	0

Figure 2. A. The ABG-II stem with proximal HA coating and 3 medial tantalum RSA markers (arrows). There were 2 additional RSA markers on the shoulder of the stem and 1 marker in the distal tip. B. Schematic drawing of the prosthesis with tantalum RSA markers in the prosthesis and in the surrounding bone, with the coordinate system for RSA analysis of 3D micromotion of the implant.

Table 2. Comparison of time-related changes in RSA migration and functional scores in THA patients with normal and low BMD

	Normal BMD	Low BMD
	(n = 12)	(n = 27)
Time point (months)	Mean (SD)	Mean (SD)	Difference	95% CI	p-value ^d
Stem subsidence ^a
3	–0.5 (0.5)	–1.1 (0.9)	0.6	0.1 to 1.2	0.02
6	–0.5 (0.6)	–1.3 (1.1)	0.8	0.1 to 1.5	0.02
12	–0.5 (0.6)	–1.2 (1.1)	0.8	0.06 to 1.4	0.03
24	–0.5 (0.6)	–1.3 (1.0)	0.8	0.1 to 1.5	0.02
Stem rotation ^b
3	1.2 (0.8)	1.6 (1.7)	–0.5	–1.5 to 0.6	0.4
6	2.0 (1.1)	1.6 (1.7)	0.4	–0.7 to 1.6	0.5
12	2.0 (1.4)	1.7 (1.8)	0.3	–1.0 to 1.5	0.6
24	1.8 (1.4)	1.8 (2.0)	0.03	–1.3 to 1.3	0.6
Harris hip score ^c
Preop.	49 (13)	51 (17)	–1.3	–13 to 11	0.8
3	75 (22)	75 (17)	0.02	–14 to 14	1.0
6	87 (13)	85 (13)	2.1	–7 to 12	0.7
12	87 (10)	88 (12)	–0.7	–9 to 7	0.9
24	86 (17)	85 (13)	1.1	–9 to 12	0.9
WOMAC score ^c
Preop.	47 (13)	53 (17)	–6.2	–21 to 9	0.4
3	26 (21)	25 (13)	1.1	–11 to 13	0.9
6	19 (11)	20 (13)	–1.5	–11 to 8	0.8
12	10 (5)	16 (11)	–5.5	–13 to 2	0.1
24	13 (9)	17 (16)	–4.2	–15 to 6	0.4

^a y-translation

^b y-rotation

^c Global p < 0.001 for the time-related change (repeated measures ANOVA).

^d Student’s t-test.

Figure 3. Stem migration determined by RSA in women with normal or low systemic BMD. A. Total translational migration expressed as translation vector. B. Total rotational migration expressed as rotation vector. The values represent mean (SD).