Migration of all-polyethylene compared with metal-backed tibial components in cemented total knee arthroplasty

Figures & data

Figure 1. CONSORT flow diagram. TKA = total knee arthroplasty.

^a Missed follow-up; ^b Technical reasons, clinical follow-up only.

Table 1. Baseline demographic characteristics

Outcome	All-polyethylene (n = 29)	Metal-backed (n = 30)
Age, mean (SD)	69 (5.5)	68 (5.6)
BMI, mean (SD)	28 (4.2)	29 (3.0)
Female sex, n	22	13
Ahlbäck’s classification, n
II	6	10
III	21	19
IV	2	1
HKA preoperative, n
Varus (< 177°)	22	25
Neutral (177–183°)	5	3
Valgus (> 183°)	2	2
HKA postoperative, n
Varus (< 177°)	4	7
Neutral (177–183°)	19	22
Valgus (> 183°)	6	1
Surgeon 1, n performed	20	14
Surgeon 2, n performed	9	16

HKA: hip–knee–ankle angle.

Table 2. RSA migration analysis of mean maximum total point motion (logMTPM values are back-transformed in original scale in millimeters), as provided by the mixed-effects model

	All-polyethylene	Metal-backed
Time	mean (95% CI)	mean (95% CI)	p-value
3 months	0.47 (0.36–0.59)	0.48 (0.38–0.60)
1 year	0.57 (0.46–0.69)	0.69 (0.57–0.82)
2 years	0.61 (0.49–0.74)	0.81 (0.68–0.96)	0.03

Figure 2. RSA analysis results of maximum total point motion (MTPM). Top: mean and 95% confidence interval for the groups; bottom: mean and 95% confidence interval for the same groups excluding 8 individual components showing continuous migration of >0.2 mm in the second postoperative year. These individual components are illustrated as 4 dashed blue lines (metal-backed) and 4 dashed red lines (all-polyethylene).