Survivorship and relative risk of revision in computer-navigated versus conventional total knee replacement at 8-year follow-up

Figures & data

Figure 1. Selection of patients. TKR: total knee replacement; NAR: Norwegian Arthroplasty Register; CAS: computer-navigated knee replacement; CON: conventionally operated knee replacement. ^a No information on use of computer navigation. ^b No information on fixation method.

Table 3. Reasons for revision in computer-navigated total knee replacement (CAS) and conventionally operated total knee replacement (CON) for all patients and for patients less than 65 years of age

		All ages						< 65 years old
		CAS		CON		CAS vs. CON^c		CAS		CON		CAS vs. CON^c
No^a		n	%^b	n	%^b	RR (95% CI)	p-value	n	%^b	n	%^b	RR (95% CI)	p-value
1	Deep infection	40	26	202	24	1.0 (0.6–1.4)	0.8	17	20	81	20	0.7 (0.4–1.3)	0.3
2	Malalignment	15	10	90	11	0.5 (0.3–0.9)	0.02	5	6	49	12	0.3 (0.1–0.8)	0.01
3	Aseptic loosening	33	21	190	23	1.1 (0.7–1.6)	0.7	17	20	99	24	1.0 (0.6–1.8)	0.9
4	Instability	29	19	112	14	0.7 (0.4–1.2)	0.2	22	27	63	15	0.9 (0.5–1.7)	0.7
5	Periprosthetic fracture	4	3	14	1.7	0.5 (0.1–2.1)	0.4	1	1	4	1.0	0.6 (0.04–7.9)	0.7
6	Decreased range of motion^d	5	3	34	4.1	0.8 (0.3–2.3)	0.7	5	6	22	5.4	1.4 (0.4–4.5)	0.6
7	Other^e	6	4	56	6.8	0.6 (0.2–1.6)	0.3	1	1	26	6.3	0.1 (0.01–1.0)	0.05
8	Pain only	24	15	125	15	1.1 (0.6–1.9)	0.7	15	18	66	16	1.2 (0.6–2.5)	0.6
	Missing	0	0	4	0.5			0	0	1	0.2
	No. of revisions	156		827				83		411
	No. of total knee replacements	3,665		20,019				1,292		6,481

a Listed in the same order as hierarchy for determination of main cause of revision.

b Percentage of number of revisions.

c Adjusted for age, sex, prosthesis brand, ASA category, fixation method (cemented, uncemented, hybrid), diagnosis (OA, other), and previous surgery of the knee (yes, no).

d Including arthrofibrosis and joint stiffness.

e Including dislocation (patella and other), polyethylene wear, and progression of arthrosis.

Table 1. Demographic data for computer-navigated total knee replacement (CAS) and conventionally operated total knee replacement (CON)

	CAS	CON	p-value
Number	3,665	20,019
Men, %	38	35	< 0.001
Age, years	68.4	69.2	< 0.001
95% CI	68.1–68.7	69.1–69.3
Right knee, %	54	54	0.9
MIS^a, n (%)	21 (0.6)	65 (0.4)	0.02
ASA category^b, n (%)			0.01
1	602 (16)	3316 (17)
2	2,378 (65)	12,506 (62)
3+	640 (18)	3,944 (20)
Missing	45 (1)	253 (1)
Diagnosis preoperatively, %			0.02
Primary gonarthritis	82	84
Other	18	16
Missing	0.1	0.2
Fixation method, n (%)			< 0.001
Cemented	2,081 (57)	16,418 (82)
Uncemented	1,456 (40)	344 (2)
Hybrid (uncemented femur)	114 (3)	3,144 (16)
Missing	14 (0.4)	113 (0.6)
Prosthesis brand, n (%)			< 0.001
AGC	94 (3)	2,054 (10)
Duracon	629 (17)	1,368 (7)
e.motion	352 (10)	8 (0)
LCS complete	1,387 (38)	8,408 (42)
Profix	1,203 (33)	8,181 (41)
Previous operations of the knee, %	38	31	< 0.001
Osteosynthesis affecting the knee joint	2.7	1.9	< 0.001
Osteotomy	3.5	3.3	0.6
Synovectomy	1.3	1.9	0.02
Other	33	25	< 0.001
Peroperative complication, %	1.8	2.1	0.2
Intact ACL^c preoperatively, %	76	81	< 0.001
Intact PCL^d preoperatively, %	95	94	0.1
Intact PCL postoperatively, %	57	56	0.3
Hospital volume 2005–2014, n^e
1–30	6	12
31–100	7	9
101–200	6	11
200	3	33
Total number of hospitals	22	65

a MIS: minimally invasive surgery.

b ASA category: American Society of Anesthesiologists physical status classification system.

c ACL: anterior cruciate ligament.

d PCL: posterior cruciate ligament.

e Number of hospitals.

Figure 2. Kaplan-Meier survival curves with 95% confidence intervals (broken lines) for computer-navigated total knee replacement (CAS) and conventionally operated (CON) total knee replacement. Log-rank test: p = 0.9. 8 years at risk: CAS, n = 354; CON, n = 2,836.

Figure 3 Cox regression survival curves with 95% confidence intervals (broken lines) for computer-navigated total knee replacement (CAS) and conventionally operated total knee replacement (CON) in patients who were more than or less than 65 years of age, adjusted for sex, ASA category, diagnosis, previous surgery, prosthesis brand, and fixation method. 8 years at risk: ≥ 65 years old: CAS, n = 228; CON, n = 1,881; < 65 years old: CAS, n = 126; CON, n = 955.

Table 2. Kaplan-Meier survival (KM) and Cox-adjusted relative risk of revision for computer-navigated total knee replacement (CAS) and for conventionally operated total knee replacement (CON)

		5 years		8 years
	MF^a, years (95% CI)	At risk	KM survival (95% CI)	At risk	KM survival (95% CI)	Cox-adjusted RR^b		Cox regression adjusted by PS^c
						(95% CI)	p-value	(95% CI)	p-value
All ages
CAS	5.3 (5.2–5.4)	1,965	95.7 (94.9–96.5)	354	94.8 (93.8–95.8)	0.8 (0.7–1.0)	0.1	0.8 (0.7–1.1)	0.1
CON	5.0 (4.9–5.0)	9,509	95.5 (95.1–95.9)	2,836	94.9 (94.5–95.3)	1		1
< 65 years
CAS	6.1 (5.7–6.5)	695	93.6 (92.2–95.0)	126	93.6 (92.2–95.0)	0.8 (0.6–1.1)	0.1	0.8 (0.6–1.1)	0.1
CON	5.4 (5.2–5.5)	3,102	93.1 (92.5–93.7)	955	92.4 (91.6–93.2)	1		1

a MF: median follow-up (reversed KM).

b RR: relative risk, CAS versus CON, adjusted for age, sex, ASA category, diagnosis, previous surgery of the knee, prosthesis brand, and fixation method.

c PS: propensity score. Covariates included in PS are the same as in the Cox-adjusted RR in addition to side, peroperative complications, and deficiency of anterior cruciate ligament preoperatively and posterior cruciate ligaments preoperatively and postoperatively.