RSA prediction of high failure rate for the uncoated Interax TKA confirmed by meta-analysis

Figures & data

Figure 1. Summary of the migration results of the previous RSA trial (Nelissen et al. 1998). The plot shows the mean migration —expressed as maximal total point motion (MTPM)—with 95% CI for each type of fixation of the tibial components: red dashed line for uncoated; green dotted line for HA-coated, and blue solid line for cemented. The uncoated tibial components showed the most migration.

Table 1. Mean migration rate (MTPM) expressed in mm/year. The uncoated components showed the highest migration rate. The migration rate was determined from the migration measured with the postoperative RSA examination as reference

	Cemented		HA-coated		Uncoated
Migration rate	Mean	95% CI	Mean	95% CI	Mean	95% CI
0–6 months ^a	1.22	0.88 to 1.57	1.84	1.07 to 2.61	2.45	1.82 to 3.10
6–12 months ^b	0.24	–0.34 to 0.82	0.27	–0.02 to 0.57	0.60	0.06 to 1.15
12–24 months ^b	–0.12	–0.31 to 0.07	0.03	–0.12 to 0.18	0.19	0.02 to 0.35

^a 0–6 months: Cem vs. HA, p = 0.2; Cem vs. UN, p = 0.01; HA vs. UN, p = 0.1 (GLMM).

^b 6–24 months: Cem vs. HA, p = 0.3; Cem vs. UN, p = 0.01; HA vs. UN, p = 0.1 (GLMM).

Figure 2. Flow diagram showing details of study selection. In cases where the title and abstract were insufficiently conclusive, the full text article was obtained.

Table 2. Characteristics of the studies included

	Cemented vs. uncoated		HA-coated vs. uncoated
Study	Pijls 2011	Gicquel 2000	Stukenborg 2000	Petersen 2005 ^a
Type	RCT	RCT	OBS	RCT
No. of TKAs	68	96	209	18
Females, n (%)	55 (81)	NS (75)	166 (79)	15 (83)
OA, n (%)	18 (26)	NS (97)	NS (67)	18 (100)
RA, n (%)	49 (72)	NS (3)	NS (26)	0 (0)
Mean age at
operation, years	66	73	68	76
Mean FU, years	7.6	2.3	6.8	2
Operation period	1993–1998	1993–1995	1991–1994	–
Deaths, n (%)	28 (42)	6 (6)	39 (19)	1 (5.5)
Lost to follow-up (%)	1 (1.5)	20 ^b (20)	3 (1.4)	1 (5.5)
Jadad quality score ^c	3	3	1	2

^a Since Petersen et al. was the only study evaluating HA-coated and uncoated and included only 18 patients, no meta-analysis could be performed for the comparison of HA-coated and uncoated.

^b 20 cases were lost to follow-up: 8 cemented cases and 12 uncoated cases.

^c Maximum attainable score was 3 because the evaluation of revision on the radiograph cannot be blinded.

RCT: randomized controlled trial; OBS: observational study; NS: not stated.

Figure 3. Forest plot summarising the pooled effect size of cemented and uncoated tibial components. As shown, there was a significantly (3 times) higher revision rate for the uncoated Interax tibial components than for the cemented ones.

Nelissen RG, Valstar ER, Rozing PM. The effect of hydroxyapatite on the micromotion of total knee prostheses. A prospective, randomized, double-blind study. J Bone Joint Surg (Am) 1998; 80 (11): 1665-72.

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