Early subsidence of shape-closed hip arthroplasty stems is associated with late revision

Figures & data

Figure 1. PRISMA flow chart of both reviews. Details of the 14 PF combinations can be found in Table 1.

Table 1. Details of prosthesis and fixation (PF) combinations

PF	Prosthesis (stems)	Fixation	Number of RSA studies	Number of survival studies	Number of combinations
1	ABG I	HA-coated	1	8	8
2	Bicontact	Porous-coated	1	4	4
3	Charnley Elite Plus (SC)	Cement (high-viscosity)	2	2	4
4	Charnley Elite Plus (SC)	Cement (low-viscosity)	1	1	1
5	Cementless Spotorno	Uncoated	1	7	7
6	Exeter (FC)	Cement (high-viscosity)	4	8	32
7	Exeter (FC)	Cement (low-viscosity)	3	1	3
8	Honnart Partel-Garches	Uncoated	1	1	1
9	Lubinus SP II (SC)	Cement (high-viscosity)	3	5	15
10	Omnifit	HA-coated	1	5	5
11	Ribbed	Uncoated	1	1	1
12	Scanhip (SC)	Cement (high-viscosity)	1	2	2
13	Spectron EF (SC)	Cement (high-viscosity)	3	4	12
14	Taperloc	Porous-coated	1	5	5
Total			24	54	100

SC: shape-closed; FC: force-closed; HA: hydroxyapatite; ABG: Anatomique Benoist Giraud

Figure 2. Scatter plot showing the subsidence at 2 years (in mm) and revision rate for aseptic loosening of the femoral stem at 10 years (percentage), categorized according to design concept (i.e. shape-closed, force-closed, uncemented).

Figure 3. Scatter plot showing the association between 2-year subsidence (in mm) and revision rate for aseptic loosening of the shape-closed femoral stem at 10 years (percentage). The colored lines are derived from weighted regression according to match quality, survival study quality, and RSA quality (the coefficients and 95% CIs are presented in Table 2).

Table 2. Association between 2-year subsidence of shape-closed femoral stems and revision rate for aseptic loosening at 10 years. Increase in 10-year revision rate (%) for each 0.1-mm increase in subsidence at 2 years. In the crude analysis (unadjusted), 4.2% (95% CI: 1.3–7.1; p < 0.05) was added to the 10-year revision rate for every 0.1-mm increase in subsidence at 2 years

	Increase in revision (%)/0.1-mm subsidence	(95% CI)
Crude	4.2	(1.3–7.1)
Adjusted for ^a:
N survival^b	3.9	(0.6–7.2)
N RSA^b	4.2	(1.2–7.4)
Survival study quality	3.7	(0.6–6.7)
RSA study quality	4.4	(1.8–7.0)
Total match score	5.2	(2.7–7.7)
Range of values	3.7–5.2	(0.6–7.2)

^a When adjusted for e.g. the number of THAs in survival studies (N survival), 3.9% (95% CI: 0.6–7.2; p > 0.05) was added to the 10-year revision rate for every 0.1-mm increase in subsidence at 2 years. The association between subsidence and revision rate for aseptic loosening remained significant when adjusting for confounders (all p-values < 0.05).

^b The square root of N was used for the weighted regression, so larger studies weighed more heavily.

N survival: number of THAs in survival studies;

N RSA: number of THAs in RSA studies.

Figure 4. Line chart of the pooled subsidence (in mm) up to 2 years, according to design concept (i.e. shape-closed, force-closed, uncemented). The standard errors were 0.05 mm and 1 mm (force-closed), 0.08 mm and 0.07 mm (uncemented), and 0.01 mm and 0.01 mm (shape-closed) at 1 and 2 years, respectively.

Figure 5. Scatter plot showing the 2-year subsidence and revision rate of shape-closed femoral stems for aseptic loosening at 10 years. The threshold of 0.15 mm for acceptable subsidence is shown. The threshold of 0.23 mm for unacceptable subsidence could be defined less precisely and is also shown. Adoption of the NICE criteria (10% revision at 10 years) did not alter these thresholds.

Figure 6. Dot chart showing the pooled 2-year subsidence of shape-closed femoral stems ranked by the pooled 10-year revision rate for each PF combination. The threshold of 0.15 mm for acceptable subsidence is shown and the less precisely definable threshold for unacceptable subsidence (0.23) is also shown.