Comparison of flanged and unflanged acetabular cup design

Figures & data

Figure 1. The Opera cup (with flange).

Figure 2. Prepared cadaveric acetabular bone bed with the cancellous bone exposed.

Figure 3. The template with test lines placed on a sample of ceramic. Note the close contact between the unflanged cup and the ceramic. Lateral segments are labeled L, and the central segment C.

Figure 4. The counting grid placed on a CT image of cadaveric bone. Opera cup (a), cement (b), cadaveric bone (c), and Vel-Mix stone (d).

Table 1. Intraacetabular pressures in ceramic. Values are median (95% confidence interval)

	Flanged	Unflanged	p-value
Position-controlled cup insertion
Force applied (N)	68 (65–74)	57 (43–83)	0.5
Pole pressure (mmHg)	353 (281–356)	402 (298–568)	0.3
Rim pressure (mmHg)	283 (282–292)	252 (189–331)	0.5
Force-controlled pressurization
Cup displacement (mm) ^a	-0.1 (-0.2–0.0)	-0.2 (-0.4 – -0.2)	0.05
Pole pressure (mmHg)	86 (0.0–108)	140 (114–160)	0.05
Rim pressure (mmHg)	76 (8–85)	25 (24–55) ^b	0.5

^a Negative displacement indicates cup migration toward the acetabular pole.

^b p < 0.05 for pole vs. rim pressures.

Table 2. Thickness of cement mantle, depth of penetration, and area of penetration per 5° sector in ceramic. Values are median (95% confidence interval)

	Flanged	Unflanged	p-value
Cement mantle
Lateral thickness (mm)	2.4 (1.7–3.8)	1.5 (0.9–2.0)	0.002
Central thickness (mm)	3.3 (2.0–4.2)	1.6 (0.6–2.1)	<0.001
Lateral area (mm^2/5°)	4.6 (3.2–7.1)	2.9 (2.1–4.1)	<0.001
Central area (mm^2/5°)	5.8 (3.7–7.7)	2.4 (1.0–4.1)	<0.001
Cement penetration
Lateral depth (mm)	3.6 (3.2–4.0)	3.8 (3.2–4.2)	0.5
Central depth (mm)	4.2 (4.6–5.3) ^a	4.7 (3.2–5.9) ^a	0.6
Lateral area (mm^2/5°)	9.2 (7.9–9.5)	8.8 (8.3–9.6)	0.2
Central area (mm^2/5°)	10.2 (8.9–12.1) ^a	10.4 (9.1–11.6) ^b	0.4

^a p <0.01 for lateral vs. central measurements.

^b p <0.001 for lateral vs. central measurements.

Table 3. Intraacetabular pressures in cadaveric bone. Values are median (95% confidence interval)

	Flanged	Unflanged	p-value
Position-controlled cup insertion
Force applied (N)	90 (12–196)	75 (0–138)	0.8
Pole pressure (mmHg)	218 (7–524)	470 (25–1,656)	0.04
Rim pressure (mmHg)	156 (3–457) ^a	196 (2–596) ^a	0.4
Force-controlled pressurization
Cup displacement (mm) ^b	-0.1 (-0.4 – 0.1)	-1.0 (-1.7–0.1)	0.01
Pole pressure (mmHg)	12 (3–100)	130 (21–190)	0.008
Rim pressure (mmHg)	17 (3–80)	23 (4–123) ^a	0.6

^a p < 0.05 for pole vs. rim pressures.

^b Negative displacement indicates cup migration toward the acetabular pole.