Peri-apatite coating decreases uncemented tibial component migration: long-term RSA results of a randomized controlled trial and limitations of short-term results

Figures & data

Figure 1. CONSORT flow diagram. TKA = total knee arthroplasty. ^a revised after 3 months (early infection), 1 year (late infection), and 10 years (mechanical failure). ^b clinical follow-up only, see text.

Table 1. Baseline demographic characteristics. Values are mean (SD) unless otherwise specified

	Uncoated	PA-coated
	(n = 29)	(n = 29)
Age	67 (6.8)	65 (8.1)
Body mass index	30 (4.3)	30 (4.9)
Female sex (n)	16	17
Previous knee surgery (n)
none	22	25
joint debridement	1	1
meniscectomy	5	2
other	1	1
Ahlbäck’s grade (n)
II	12	6
III	15	22
IV	2	1
ASA classification (n)
I	8	6
II	20	21
III	1	2
Hip–knee–ankle angle
preoperative	175 (5.0)	176 (6.2)
postoperative	179 (2.8)	179 (3.2)

Figure 2. Maximum total point motion (back-transformed in the original scale in mm) during 10 years of follow-up: (top) the mean and 95% CI for the groups and (bottom) the mean and 95% CI for the groups and separate lines for the components showing continuous migration in the second postoperative year (in green the stabilized components after 2 years, in dashed brown the components failing to stabilize after 2 years and suspected for aseptic loosening, and in solid brown the revised component).

Table 2. RSA migration measurements in absolute mm or degrees (95% CI) (log-transformed values are back-transformed in the original scale)

	1 year		2 years		10 years
	Uncoated	PA-coated	Uncoated	PA-coated	Uncoated	PA-coated	p-value^a
Translations (mm):
Transverse	0.4 (0.28–0.49)	0.3 (0.21–0.40)	0.4 (0.33–0.54)	0.3 (0.19–0.38)	0.4 (0.30–0.54)	0.4 (0.24–0.48)	0.2
Longitudinal	0.5 (0.42–0.67)	0.3 (0.18–0.39)	0.5 (0.41–0.66)	0.3 (0.17–0.38)	0.5 (0.41–0.69)	0.3 (0.17–0.41)	< 0.001
Sagittal	0.5 (0.42–0.68)	0.3 (0.17–0.38)	0.7 (0.52–0.80)	0.2 (0.13–0.34)	0.7 (0.55–0.87)	0.3 (0.17–0.42)	< 0.001
Rotations (°):
Transverse	1.1 (0.79–1.37)	0.6 (0.39–0.83)	1.2 (0.92–1.55)	0.6 (0.35–0.80)	1.3 (0.94–1.64)	0.6 (0.33–0.83)	< 0.001
Longitudinal	0.7 (0.50–0.82)	0.3 (0.17–0.42)	0.8 (0.67–1.04)	0.3 (0.18–0.44)	1.0 (0.78–1.21)	0.3 (0.14–0.43)	< 0.001
Sagittal	0.6 (0.49–0.83)	0.4 (0.30–0.59)	0.8 (0.66–1.04)	0.5 (0.36–0.67)	0.8 (0.57–0.97)	0.5 (0.30–0.65)	0.004
MTPM (mm)	1.5 (1.24–1.88)	0.9 (0.71–1.18)	1.7 (1.35–2.01)	0.9 (0.70–1.17)	1.7 (1.41–2.08)	0.9 (0.72–1.19)	< 0.001

a p-values stated in this column indicate testing the between-group mean differences with time over the entire postoperative follow-up period.