Existing data sources for clinical epidemiology: The Danish Knee Arthroplasty Register

Figures & data

Table 1 Number of knee arthroplasty procedures registered in the Danish Knee Arthroplasty Registry, period 1997–2010

Type of surgery	1997–2000	2001–2007	2008	2009	2010	Total
Primary arthroplasty (n)	7368	31,865	7107	8347	7899	62,586
Revision (n)	922	3012	803	993	953	6683

Figure 1 Annual incidence rates of primary knee arthroplasty procedures per 100,000 inhabitants (on y-axis) in Denmark in the period 1997–2010 (on x-axis).

Figure 2 Incidence rates of primary knee arthroplasty procedures per 100,000 inhabitants (on y-axis) in Denmark according to specific age and sex (on x-axis).

Table 2 Diagnosis for primary knee arthroplasty registered in the Danish Knee Arthroplasty Register, 1997–2010

Diagnosis*	1997–2000		2001–2007		2008		2009		2010		Total
	n	%	n	%	n	%	n	%	n	%	n	%
Primary osteoarthritis	5.690	77.3	26.269	82.7	6.208	87.9	7.185	86.6	6.774	86.2	52.126	83.6
Secondary osteoarthritis	741	10.1	3409	10.7	617	8.7	796	9.6	854	10.9	6.417	10.3
Rheumatoid arthritis	564	7.7	1173	3.7	159	2.3	164	2.0	153	1.9	2.213	3.5
Sequelae after fracture of tibia condyle	201	2.7	588	1.9	84	1.2	90	1.1	101	1.3	1.064	1.7
Other diagnoses	160	2.2	474	1.5	82	1.2	107	1.3	114	1.5	937	1.5
Sequelae after other arthritis	67	0.9	229	0.7	39	0.6	54	0.7	61	0.8	450	0.7
Sequelae after fracture of femoral condyle	54	0.7	161	0.5	18	0.3	31	0.4	27	0.3	291	0.5
Sequelae after fracture of patella	20	0.3	100	0.3	14	0.2	23	0.3	20	0.3	177	0.3
Hemophilia	9	0.1	13	0.0	3	0.0	1	0.0	0	0.0	26	0.0
Total	7.363	100.0	31.767	100.0	7.063	100.0	8.295	100.0	7.856	100.0	62.344	100.0

Notes:

* Several diagnoses could be registered for the same primary procedure.

Table 3 The most-commonly used femoral and tibia components for primary knee arthroplasty registered in the Danish Knee Arthorplasty Arthroplasty Registry, 1997–2010

	n	%*
Femoral components
PFC Sigma Cruciate-Retaining (Johnson and Johnson)	15.225	24.3
AGC V2 Universal (Biomet)	11.590	18.5
NexGen CR (Zimmer)	7.209	11.5
PFC Sigma Cruciate-Substituting (Johnson and Johnson)	5.588	8.9
Vanguard CR (Biomet)	2.905	4.6
Oxford Phase II (Biomet)	2.062	3.3
Tibia components	n	%
AGC V2 (Biomet)	1.917	19.0
PFC Modular (Johnson and Johnson)	11.593	18.5
NexGen CR (Zimmer)	6.333	10.1
PFC Sigma Rotating Platform (Johnson and Johnson)	3.781	6.0
PFC Sigma Cruciate-Retaining (Johnson and Johnson)	2.995	4.8
Vanguard CR (Biomet)	2.830	4.5

Notes:

* Percentages are calculated as proportions, with the nominator numerator containing the number of uses of the particular component used and the denominator containing the total number of primary arthroplasty procedures in the period 1997–2010.

Abbreviations: AGC, anatomical femoral component; CR, cruciate retaining; PFC, posterior fixed component.

Table 4 Indication for revision of primary knee arthroplasty registered in the Danish Knee Arthroplasty Registry, 1997–2010

Indication*	1997–2000		2001–2007		2008		2009		2010		Total
	n	%	n	%	n	%	n	%	n	%	n	%**
Aseptic loosening	307	33.3	987	32.8	196	24.4	273	27.5	273	28.6	2.036	30.7
Pain without loosening	204	22.1	607	20.2	139	17.3	147	14.8	159	16.7	1.256	20.4
Secondary insertion of patella component	177	19.2	235	7.8	50	6.2	61	6.1	41	4.3	564	17.7
Deep infection	152	16.5	578	19.2	255	31.8	287	28.9	246	25.8	1.518	15.2
Knee instability	145	15.7	556	18.5	139	17.3	175	17.6	171	17.9	1.186	14.5
Polyethylene wear, tibia	115	12.5	247	8.2	34	4.2	39	3.9	41	4.3	476	11.5
Polyethylene wear, patella	83	9.0	171	5.7	24	3.0	19	1.9	23	2.4	320	8.3
Other	88	9.5	354	11.8	88	11.0	145	14.6	128	13.4	803	8.8

Notes:

* Several indications could be registered for the same revision procedure.

** Percentages are calculated as proportions, nominator with the numerator containing the number of instances of a particular indication registered in a particular time period and the denominator containing the total number of revisions performed in the same time period.

Figure 3 Revision rates in Denmark within 1, 2, and 5 years of primary knee arthroplasty procedures in percentages (on y-axis) for patients operated on in the period 1997–2010 (on x-axis).

Figure 4 Survival of primary total knee arthroplasties according to years of surgery. Endpoint: first revision due to any cause.

Abbreviation: CI, confidence interval.