Inferior stabilization of cementless compared with cemented dual-mobility cups in elderly osteoarthrosis patients: a randomized controlled radiostereometry study on 60 patients with 2 years’ follow-up

Figures & data

Figure 1. CONSORT flow diagram showing the inclusion/exclusion process until 2-year follow-up.

Table 1. RSA measurement error based on double-examination stereoradiographs

	Translation (mm)	Rotation (°)
	X	Y	Z	TT^a	X	Y	Z	TR^b	MTPM^c
Mean dif.^d	0.02	–0.01	–0.01	0.00	–0.23	–0.05	0.09	0.07	0.01
SD dif.^e	0.20	0.09	0.16	0.17	0.91	0.92	0.64	0.90	0.57
CR (1.96 × SD dif.)^f	0.39	0.18	0.31	0.33	1.78	1.80	1.25	1.76	1.12

There was no statistically significant difference between cemented and cementless fixation.

a TT: total translation was calculated using 3D Pythagorean theorem (TT = sqrt (xt2 + yt2+ zt2).

b TR: total rotation was calculated using 3D Pythagorean theorem (TR = sqrt (xr2 + yr2 + zr2).

c MTPM: maximum total point motion is an absolute migration parameter (migration vector).

d Mean dif.: systematic error between two RSA double measurements (should optimally be 0).

e SD dif.: standard deviation of the difference between the two examinations (SD dif.) reflects the precision of the applied RSA method.

f CR: the coefficient of repeatability (1.96 × SD dif.) reflects the lower limit within which it is possible to detect prosthetic migration on an individual basis.

Figure 2. Illustration of directions, translation, and rotations for Avantage DM cup.

Figure 3. Wilkinson regions of interest (ROI) 1–4. Only the bone areas within yellow lines are included in the analysis.

Table 2. DXA (g/cm²) measurement error based on 3-month double-examination DXA scans for cemented and cementless cup fixation

	Cemented	Cementless
	ROI1	ROI2	ROI3	ROI4	ROI1	ROI2	ROI3	ROI4
Mean dif.	–0.02	–0.01	–0.05	–0.01	0.02	–0.01	0.00	0.01
SD dif.	0.07	0.31^a	0.13^a	0.07	0.07	0.11^a	0.07^a	0.05
CV %^b	3.02	12.50	8.20	5.40	3.20	6.26	5.83	4.14

a Denotes significant difference between cemented and cementless cups using the F-test.

b CV% = 100 Ч [(δ/√2)/µ] for each ROI for cemented and cementless cup fixation.δ represents the SD of the difference between the paired BMD measurements, and µ is the overall mean of all BMD measurements for each ROI.

Table 3. Descriptive baseline characteristics of the patients, implants, and surgery. Values are mean (range) unless otherwise specified

	Cemented	Cementless
	(n = 29)	(n = 30)
Sex, male/female, n	14/15	13/17
Age at operation	75 (70–82)	75 (70–83)
Implant side, right/left, n	16/13	15/15
Cup size (mm)	48.7 (44–54)	52.8 (48–58)
Cup inclination (°)	49.2 (36.2–61.0)	43.5 (28.9–59.7)
Cup anteversion (°)	11.5 (1.2–26.2)	11.7 (0.7–26.3)
Preoperative T-score	–1.01 (–2.9–1.8)	–1.12 (–3.1–2.3)
BMI	28 (23–39)	29 (22–38)
ASA class	2.0 (1–3)	1.8 (1–3)

Figure 4. Significant migration in cementless cups compared with cemented in y-axis, TR, and MTPM.

Table 4. Translations along and rotations about the x-, y-, and z-axis for cemented and cementless cups presented as mean (95% CI)

Cemented		Cementless
Axis	(n = 28)	(n = 28)
Translations (mm)
x-axis
3 months	–0.01 (–0.17 to 0.14)	0.08 (–0.19 to 0.36)
12 months	–0.03 (–0.21 to 0.15)	0.16 (–0.20 to 0.51)
24 months	–0.01 (–0.22 to 0.20)	0.23 (–0.20 to 0.66)
y-axis
3 months	0.08 (0.00 to 0.16)	0.15 (0.02 to 0.27)
12 months	0.09 (0.01 to 0.18)	0.12 (–0.02 to 0.26)
24 months	0.11 (0.00 to 0.23)	0.09 (–0.09 to 0.28)
z-axis
3 months	0.16 (0.00 to 0.32)	0.31 (0.00 to 0.62)
12 months	0.15 (–0.01 to 0.31)	0.36 (0.03 to 0.69)
24 months	0.23 (0.02 to 0.44)	0.39 (0.03 to 0.75)
Total translation
3 months	0.49 (0.34 to 0.64)	0.79 (0.49 to 1.10)
12 months	0.56 (0.37 to 0.76)	0.88 (0.51 to 1.25)
24 months	0.65 (0.44 to 0.87)	0.98 (0.54 to 1.42)
Rotations (°)
x-axis
3 months	0.34 (0.01 to 0.66)	0.01 (–0.48 to 0.51)
12 months	0.52 (0.15 to 0.89)	0.64 (–0.01 to 1.30)
24 months	0.29 (–0.05 to 0.63)	0.04 (–0.63 to 0.70)
y-axis ^a
3 months	0.23 (0.26 to 0.72)	1.08 (0.34 to 1.82)
12 months	0.30 (–0.25 to 0.85)	1.74 (0.91 to 2.57) ^b
24 months	0.18 (–0.37 to 0.73)	1.10 (0.42 to 1.78)
z-axis
3 months	–0.35 (–0.60 to 0.03)	–0.07 (–0.60 to 0.46)
12 months	–0.40 (–0.75 to –0.05)	–0.33 (–0.92 to 0.26)
24 months	–0.35 (–0.76 to 0.05)	–0.01 (–0.69 to 0.68)
Total rotation ^a
3 months	1.52 (1.12 to 1.90)	2.23 (1.55 to 2.92)
12 months	1.80 (1.40 to 2.24)	3.00 (2.20 to 3.80) ^b
24 months	1.72 (1.30 to 2.13)	2.57 (1.83 to 3.30)
MTPM (mm) ^a
3 months	1.14 (0.86 to 1.42)	1.81 (1.26 to 2.36)
12 months	1.30 (1.00 to 1.60)	2.24 (1.64 to 2.85) ^b
24 months	1.36 (1.00 to 1.73)	2.16 (1.44 to 2.87)

MTPM: maximum total point motion.

^aDenotes Bonferroni adjusted p-values for multiple testing.

^bStatistically significant difference between cemented and cementless cup fixation.

Table 5. Cup rotations and MTPM between follow-ups within each cup fixation group presented as mean difference (95% CI)

Rotations (°)	Cemented	Cementless
x-axis
3–12 months	–0.18 (–0.49 to 0.13)	–0.63 (–0.95 to 0.31)^a
12–24 months	0.23 (–0.08 to 0.55)	0.61 (0.28 to 0.93)^a
y-axis
3–12 months	–0.07 (–0.44 to 0.29)	–0.66 (–1.03 to 0.28)^a
12–24 months	0.14 (–0.22 to 0.51)	0.64 (0.26 to 1.01)^a
z-axis
3–12 months	0.09 (–0.15 to 0.32)	0.26 (0.01 to 0.50)
12–24 months	–0.08 (–0.32 to 0.15)	–0.33 (–0.60 to –0.08)^a
Total translation
3–12 months	–0.25 (–0.62 to 0.12)	–0.75 (–1.13 to 0.36)^a
12–24 months	0.07 (–0.31 to 0.44)	0.42 (0.04 to 0.80)^a

a Statistically significant within-group difference from one follow-up to next follow-up.

Figure 5. Proximal translation in normal and low BMD when stratified according to fixation method.

Figure 6. MTPM migration in normal and low BMD groups based on cup fixation.

Table 6. BMD change in the 4 ROIs around the acetabular component presented as mean (95% CI) percentage change from the baseline values at 3, 12, and 24 months

ROI Follow-up	Cemented	Cementless
ROI 1	Postoperative	ref	ref
	3 months	0 (–2 to 2)	–1 (–4 to 1)
	12 months	1 (–1 to 3)	–2 (–4 to 0)
	24 months	3 (1 to 5)	–2 (–4 to 0) ^a
ROI 2	Postoperative	ref	ref
	3 months	–7 (–13 to –1)	–4 (–11 to 2)
	12 months	–1 (–6 to 6)	–12 (–19 to –6) ^a
	24 months	–7 (–13 to –1)	–11 (–17 to –4)
ROI 3	Postoperative	ref	ref
	3 months	–5 (–10 to 0)	4 (–1 to 9) ^a
	12 months	–2 (–7 to 3)	4 (–1 to 8)
	24 months	–1 (–6 to 4)	4 (–1 to 9)
ROI 4	Postoperative	ref	ref
	3 months	–5 (–8 to –1)	–1 (–4 to 3)
	12 months	–7 (–10 to –3)	–2 (–6 to 2)
	24 months	–9 (–13 to –6)	–1 (–4 to 3) ^a

ROI: Regions of interest according to Wilkinson et al. (2001).

a Statistically significant difference between cemented and cementless fixation.

Table 7. Mean (SD) scores for the HHS, OHS, EQ-5D, and VAS for pain

	Cemented	Cementless
Outcomes	(n = 29)	(n = 30)	p-value
HHS
	Preoperative	56 (12)	56 (16)	0.6
	3 months	80 (13)	81 (14)	0.6
	12 months	92 (6.5)	89 (10)	0.3
	24 months	92 (8.7)	90 (11)	0.7
OHS
	Preoperative	25 (6.5)	25 (6.2)	0.8
	3 months	37 (8.0)	39 (5.6)	0.8
	12 months	45 (3.9)	43 (4.9)	0.1
	24 months	45 (4.3)	43 (5.5)	0.3
EQ-5D
	Preoperative	0.63 (0.15)	0.66 (0.10)	0.9
	3 months	0.88 (0.13)	0.90 (0.10)	0.6
	12 months	0.93 (0.10)	0.92 (0.11)	0.8
	24 months	0.94 (0.10)	0.92 (0.10)	0.4
VAS for hip pain (rest)
	Preoperative	3.2 (2.7)	2.9 (2.0)	0.7
	3 months	0.9 (1.3)	0.7 (0.8)	0.6
	12 months	0.03 (0.2)	0.2 (1.1)	0.5
	24 months	0.1 (0.6)	0.2 (0.8)	0.6
VAS for hip pain (activity)
	Preoperative	6.8 (1.9)	5.5 (2.1)	0.02
	3 months	1.0 (0.9)	0.9 (0.8)	0.7
	12 months	0.2 (0.5)	0.5 (1.4)	0.5
	24 months	0.4 (1.0)	0.1 (0.3)	0.4

HHS: Harris Hip Score. OHS: Oxford Hip Score.

EQ-5D: EuroQol—five-dimensional. VAS: Visual Analogue Scale.

Wilkinson J M, Peel N F, Elson R A, Stockley I, Eastell R. Measuring bone mineral density of the pelvis and proximal femur after total hip arthroplasty. J Bone Joint Surg Br 2001; 83(2): 283–8.

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