The beneficial effect of hydroxyapatite lasts

Figures & data

Table 1. Baseline characteristics. Values are mean (SD)

	Cement	HA	Uncoated
	(n = 24)	(n = 24)	(n = 20)
Age	69 (8.6)	63 (11)	65 (15)
Sex (F:M)	18:6	21:3	16:4
Diagnosis (RA:OA:SA) ^a	15:9:0	17:6:1	17:3:0
BMI	26 (3.8)	27 (4.9)	24 (3.3)
Preoperative FTA angle	176 (8.1)	174 (8.7)	171 (12)
Preoperative KSS	27 (11)	22 (17)	25 (21)
Preoperative KSS (function)	14 (18)	14 (21)	5 (11)

^a RA: rheumatoid arthritis; OA: osteoarthritis; SA: sequelae after septic arthritis.

Figure 1. CONSORT flow chart.

Figure 2. Migration in maximum total point motion (MTPM) (mean and standard deviation) according to the duration of follow-up in the hydroxyapatite (HA) group (green boxes), the uncoated group (red boxes), and the cemented group (blue boxes). The direct postoperative RSA radiograph is the reference. The groups differed significantly in migration (p < 0.001, GLMM). Missing values at 4-year follow-up were estimated as the mean of the 3-year and 5-year follow-up.

Figure 3. Migration from 1 to 10 years in maximum total point motion (MTPM) (mean and standard deviation) according to the duration of follow-up in the hydroxyapatite (HA) group (green boxes), the uncoated group (red boxes), and the cemented group (blue boxes). The 1-year postoperative RSA radiograph is the reference. The groups differed significantly in migration (p < 0.001, GLMM). Missing values at 4-year follow-up were estimated as the mean of the 3-year and 5-year follow-up.

Figure 4. Migration from 1 to 16 years in maximum total point motion (MTPM) of individual cases with 10 years of RSA follow-up or more according to the duration of follow-up in the hydroxyapatite (HA) group (upper row), the uncoated group (middle row), and cemented group (lower row). The 1-year postoperative RSA radiograph was the reference.

Table 2. Clinical and radiographic results

		Cement	HA	Uncoated
		Mean SD (95% CI)	Mean SD (95% CI)	Mean SD (95% CI)
Knee score ^a	5-year	81 11 (75–88)	81 13 (74–88)	83 5 (80–86)
	10-year	81 15 (71–91)	85 7 (80–90)	87 7 (81–92)
	Last FU ^f	76 18 (68–84)	86 10 (81–90)	81 14 (74–87)
Knee function score ^b	5-year	69 21 (55–82)	38 30 (20–55)	52 35 (30–75)
	10-year	45 29 (25–65)	46 33 (23–69)	42 32 (18–67)
	Last FU ^f	29 34 (14–44)	29 32 (15–43)	23 31 (8–38)
HSS ^b	5-year	48 8 (44–53)	46 11 (40–51)	49 5 (47–52)
	10-year	48 4 (45–50)	49 7 (44–53)	47 5 (43–51)
	Last FU ^f	41 17 (33–48)	51 14 (45–57)	41 14 (33–47)
Flexion ^d	5-year	109 16 (100–118)	100 15 (92–108)	101 14 (93–110)
	10-year	110 16 (100–120)	103 13 (93–113)	106 12 (95–110)
	Last FU ^f	105 13 (99–111)	106 12 (101–111)	101 17 (93–108)
FTA angle ^e	1-year	176 2.8 (175–177)	177 3.4 (176–178)	176 2.4 (175–177)
	5-year	177 2.3 (175–178)	177 4.1 (175–179)	177 2.9 (175 178)
	10-year	177 2.2 (175–178)	178 4.4 (175–181)	176 2.8 (174–178)
Alfa angle ^g	1-year	93 2.6 (92–95)	94 2.7 (93–95)	94 3.0 (93–96)
Beta angle ^h	1-year	90 1.7 (89–90)	88 3.0 (87–89)	89 2.0 (88–90)
Delta angle ^i	1-year	88 3.1 (86–89)	88 2.8 (87–89)	87 3.5 (86–89)

^a p = 0.86, GLMM.

^b p = 0.43, GLMM.

^c p = 0.64, GLMM.

^d p = 0.15, GLMM.

^e p = 0.28, GLMM.

^f Last FU at mean 9.0 years (range 3 months to 16 years) was calculated using the clinical score

at the last available FU for each patient.

^b HSS: Hospital for Special Surgery score

^e FTA angle: femoral–tibial alignment

^g Alfa angle: frontal angle of the femoral component

^h Beta angle: frontal angle of the tibial component

ⁱ Delta angle: sagittal angle of the tibial component.

Figure 5. Individual migration patterns of the liner exchange and revised cases (with the postoperative radiograph as reference). For the insert exchanges, the letters at the top indicate the time of insert exchange with blue C for cemented tibial components, green H for HA-coated tibial components, and red U for uncoated tibial components. The tibial components remained securely fixed after the exchange of insert.