5. Results
5.4 Mortality after hip or knee joint replacement (Study 3)
Median follow-up time was 7.8 years (IQR 5.8-10.0 years) postoperatively. Among the survivors, the longest follow-up time was over 14 years and the shortest over four years. During the 90 postoperative days, 70 patients (0.4%) died as one-year mortality rate was 1.7% (241 deaths).
5.4.1 Mortality in different CKD stages (Study 3)
When compared to CKD stage 1, mortality increased with every step of advancing CKD stage when confounding factors were taken into account (Table 17). Median survival times for stage 1-5 CKD were; stage 1, 11 years (95% CI, 11.3-11.5 years) in Stage 2, 9 years (9.2-9.7 years) in stage 3, 7 years (5.6-7.5 years) in stage 4, and 6 years (4.9-8.0 years) in stage 5. Figure 4 shows Kaplan-Meier plot of different CKD stages and survival.
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(Table 17).SCr recognized CKD with a sensitivity of 72% (1,531 out of 2,139 patients) and specificity of 98% (16,140 out of 16,436 patients).
Table 16. Prevalence of CKD [eGFR < 60mL/min], according to different formulae, among 16,748 patients with normal SCr levels
Older age and BMI < 25kg/m2
≥ 75 203 [14.7%] 775 [56.1%] 274 [19.8%]
Primary osteoarthritis 279 [2.0%] 985 [7.8%] 528 [3.8%]
Secondary osteoarthritis 10 [1.1%] 33 [4.0%] 19 [2.1%]
Rheumatoid arthritis 6 [1.1%] 54 [10.0%] 8 [1.4%]
MDRD = Modification of Diet in Renal Disease, CG = Cockcroft-Gault, CKD-EPI = Chronic Kidney Disease Epidemiology Collaboration
1Anemia was defined as hemoglobin <117 g/l in women and <134 g/l in men.
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Table 17. Survival of patients depending on their renal function Survival, %
†Adjusted by for BMI, congestive heart failure, coronary disease, diabetes, and hypertension; *adjusted for BMI, congestive heart failure, coronary disease, diabetes, and hypertension; CKD = chronic kidney disease; HR = hazard ratio;
CKD-EPI = Chronic Kidney Disease Epidemiology Collaboration; eGFR = estimated glomerular filtration rate.
5.4 Mortality after hip or knee joint replacement (Study 3)
Median follow-up time was 7.8 years (IQR 5.8-10.0 years) postoperatively. Among the survivors, the longest follow-up time was over 14 years and the shortest over four years. During the 90 postoperative days, 70 patients (0.4%) died as one-year mortality rate was 1.7% (241 deaths).
5.4.1 Mortality in different CKD stages (Study 3)
When compared to CKD stage 1, mortality increased with every step of advancing CKD stage when confounding factors were taken into account (Table 17). Median survival times for stage 1-5 CKD were; stage 1, 11 years (95% CI, 11.3-11.5 years) in Stage 2, 9 years (9.2-9.7 years) in stage 3, 7 years (5.6-7.5 years) in stage 4, and 6 years (4.9-8.0 years) in stage 5. Figure 4 shows Kaplan-Meier plot of different CKD stages and survival.
66 Figure 4. Survival of patients according to CKD stage
Over 90 postoperative days, 1% of patients with CKD stage 3 died, whereas 2% of CKD 4-5 patients died. At five and ten years postoperatively, 21% and 68% of patients with CKD stage 3 had died, whereas five- and ten-year mortality rate was 47% and 87% among patients with CKD stage 4-5 (Table 17). In Study 4, cumulative incidence of death was also higher in more advanced CKD stages (Table 18).
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Table 18. The cumulative incidence of different outcomes at different time intervals
Hips n = 7,753 Knees n = 11,226
CKD 1
n=2,623 CKD 2
n=4,259 CKD 3 n=832 CKD 4-5
n=39 CKD 1
n=3,809 CKD 2
n=6,235 CKD 3
n=1,139 CKD 4-5
n=43
90 days Revision 37 (1.4%) 70 (1.6%) 11 (1.3%) - 20 (0.5%) 26 (2.4%) 6 (0.5%) -
PJI 10 (0.4%) 26 (0.6%) 4 (0.5%) - 17 (0.4%) 18 (0.3%) 3 (0.3%) -
Death 4 (0.2%) 10 (0.2%) 12 (1.4%) - 4 (0.1%) 6 (0.1%) 5 (0.4%) -
1 year Revision 52 (2.0%) 98 (2.3%) 18 (2.2%) - 59 (1.5%) 61 (1.0%) 10 (0.9%) 1 (2.3%)
PJI 15 (0.6%) 30 (0.7%) 5 (0.6%) - 29 (0.8%) 32 (0.5%) 5 (0.4%) 1 (2.3%)
Death 14 (0.5%) 41 (1.0%) 22 (2.6%) - 16 (0.4%) 43 (0.7%) 20 (1.8%) 1 (2.3%)
2 years Revision 63 (2.4%) 117 (2.7%) 21 (2.5%) - 99 (2.6%) 107 (1.7%) 21 (1.8%) 1 (2.3%)
PJI 15 (0.6%) 33 (0.8%) 5 (0.6%) - 30 (0.8%) 39 (0.6%) 6 (0.5%) 1 (2.3%)
Death 32 (1.2%) 96 (2.3%) 42 (5.0%) 3 (7.7%) 33 (0.9%) 106 (1.7%) 51 (4.5%) 2 (4.7%)
5 years Revision 83 (3.2%) 151 (3.5%) 30 (3.6%) - 158 (4.1%) 152 (2.4%) 23 (2.0%) 3 (7.0%)
PJI 18 (0.7%) 34 (0.8%) 6 (0.7%) - 37 (1.0%) 45 (0.7%) 6 (0.5%) 2 (4.7%)
Death 92 (3.5%) 278 (6.5%) 106 (12.7%) 10 (25.6%) 115 (3.0%) 333 (5.3%) 149 (13.1%) 15 (34.9%)
8 years Revision 92 (3.5%) 163 (3.8%) 35 (4.2%) - 178 (4.7%) 169 (2.7%) 27 (2.4%) 3 (7.0%)
PJI 18 (0.7%) 38 (0.9%) 6 (0.7%) - 40 (1.1%) 51 (0.8%) 6 (0.5%) 2 (4.7%)
Death 130 (5.0%) 436 (10.2%) 163 (19.6%) 14 (35.9%) 173 (4.5%) 575 (9.2%) 226 (19.8%) 20 (46.5%) Overall
rate of Revision 93 (3.5%) 165 (3.9%) 35 (4.2%) - 182 (4.8%) 170 (2.7%) 29 (2.5%) 3 (7.0%)
PJI 18 (0.7%) 38 (0.9%) 6 (0.7%) - 40 (1.1%) 52 (0.8%) 6 (0.5%) 2 (4.7%)
Death 146 (5.6%) 498 (11.7%) 183 (22.0%) 14 (35.9%) 207 (5.4%) 701 (11.2%) 260 (22.8%) 20 (46.5%) Median follow up in
years (IQR) 5.6 (3.4–7.8) 5.2 (3.1–7.3) 5.0 (2.9–7.1) 4.3 (2.5–
6.1) 6.0 (3.4–8.6) 5.7 (3.3–8.1) 5.2 (3.0–7.4) 3.4 (2.0–4.8) CKD = Chronic kidney disease, PJI = periprosthetic joint infection, Revision = All-cause revision
5.4.2 Mortality compared with other previously known risk factors (Study 3)
In the multivariable model with all-cause mortality as an outcome, hazard ratio for stage 3 (3.8; 95% CI 3.4-4.2) and stages 4-5 (8.1; 95% CI 6.3-10.3) CKD was higher when compared to the HR of diabetes (1.7; 95% CI 1.5-1.9) hypertension (1.4; 95%
CI 1.3-1.5), CHF (2.1; 95% CI 1.8-2.5) or CD (1.5; 95% CI 1.4-1.7).
5.4.3 Mortality in different risk factor combinations (Study 3)
Risk of mortality was increased when CKD was combined with diabetes, congestive heart failure or coronary disease when compared to CKD, diabetes, CHF or CD alone. However, among patients with both CKD and diabetes, HR for mortality was 3 times higher than the sum of HRs of CKD and diabetes alone 90 days and one year postoperatively. (Table 19)
66 Figure 4. Survival of patients according to CKD stage
Over 90 postoperative days, 1% of patients with CKD stage 3 died, whereas 2% of CKD 4-5 patients died. At five and ten years postoperatively, 21% and 68% of patients with CKD stage 3 had died, whereas five- and ten-year mortality rate was 47% and 87% among patients with CKD stage 4-5 (Table 17). In Study 4, cumulative incidence of death was also higher in more advanced CKD stages (Table 18).
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Table 18. The cumulative incidence of different outcomes at different time intervals
Hips n = 7,753 Knees n = 11,226
CKD 1
n=2,623 CKD 2
n=4,259 CKD 3 n=832 CKD 4-5
n=39 CKD 1
n=3,809 CKD 2
n=6,235 CKD 3
n=1,139 CKD 4-5
n=43
90 days Revision 37 (1.4%) 70 (1.6%) 11 (1.3%) - 20 (0.5%) 26 (2.4%) 6 (0.5%) -
PJI 10 (0.4%) 26 (0.6%) 4 (0.5%) - 17 (0.4%) 18 (0.3%) 3 (0.3%) -
Death 4 (0.2%) 10 (0.2%) 12 (1.4%) - 4 (0.1%) 6 (0.1%) 5 (0.4%) -
1 year Revision 52 (2.0%) 98 (2.3%) 18 (2.2%) - 59 (1.5%) 61 (1.0%) 10 (0.9%) 1 (2.3%)
PJI 15 (0.6%) 30 (0.7%) 5 (0.6%) - 29 (0.8%) 32 (0.5%) 5 (0.4%) 1 (2.3%)
Death 14 (0.5%) 41 (1.0%) 22 (2.6%) - 16 (0.4%) 43 (0.7%) 20 (1.8%) 1 (2.3%)
2 years Revision 63 (2.4%) 117 (2.7%) 21 (2.5%) - 99 (2.6%) 107 (1.7%) 21 (1.8%) 1 (2.3%)
PJI 15 (0.6%) 33 (0.8%) 5 (0.6%) - 30 (0.8%) 39 (0.6%) 6 (0.5%) 1 (2.3%)
Death 32 (1.2%) 96 (2.3%) 42 (5.0%) 3 (7.7%) 33 (0.9%) 106 (1.7%) 51 (4.5%) 2 (4.7%)
5 years Revision 83 (3.2%) 151 (3.5%) 30 (3.6%) - 158 (4.1%) 152 (2.4%) 23 (2.0%) 3 (7.0%)
PJI 18 (0.7%) 34 (0.8%) 6 (0.7%) - 37 (1.0%) 45 (0.7%) 6 (0.5%) 2 (4.7%)
Death 92 (3.5%) 278 (6.5%) 106 (12.7%) 10 (25.6%) 115 (3.0%) 333 (5.3%) 149 (13.1%) 15 (34.9%)
8 years Revision 92 (3.5%) 163 (3.8%) 35 (4.2%) - 178 (4.7%) 169 (2.7%) 27 (2.4%) 3 (7.0%)
PJI 18 (0.7%) 38 (0.9%) 6 (0.7%) - 40 (1.1%) 51 (0.8%) 6 (0.5%) 2 (4.7%)
Death 130 (5.0%) 436 (10.2%) 163 (19.6%) 14 (35.9%) 173 (4.5%) 575 (9.2%) 226 (19.8%) 20 (46.5%) Overall
rate of Revision 93 (3.5%) 165 (3.9%) 35 (4.2%) - 182 (4.8%) 170 (2.7%) 29 (2.5%) 3 (7.0%)
PJI 18 (0.7%) 38 (0.9%) 6 (0.7%) - 40 (1.1%) 52 (0.8%) 6 (0.5%) 2 (4.7%)
Death 146 (5.6%) 498 (11.7%) 183 (22.0%) 14 (35.9%) 207 (5.4%) 701 (11.2%) 260 (22.8%) 20 (46.5%) Median follow up in
years (IQR) 5.6 (3.4–7.8) 5.2 (3.1–7.3) 5.0 (2.9–7.1) 4.3 (2.5–
6.1) 6.0 (3.4–8.6) 5.7 (3.3–8.1) 5.2 (3.0–7.4) 3.4 (2.0–4.8) CKD = Chronic kidney disease, PJI = periprosthetic joint infection, Revision = All-cause revision
5.4.2 Mortality compared with other previously known risk factors (Study 3)
In the multivariable model with all-cause mortality as an outcome, hazard ratio for stage 3 (3.8; 95% CI 3.4-4.2) and stages 4-5 (8.1; 95% CI 6.3-10.3) CKD was higher when compared to the HR of diabetes (1.7; 95% CI 1.5-1.9) hypertension (1.4; 95%
CI 1.3-1.5), CHF (2.1; 95% CI 1.8-2.5) or CD (1.5; 95% CI 1.4-1.7).
5.4.3 Mortality in different risk factor combinations (Study 3)
Risk of mortality was increased when CKD was combined with diabetes, congestive heart failure or coronary disease when compared to CKD, diabetes, CHF or CD alone. However, among patients with both CKD and diabetes, HR for mortality was 3 times higher than the sum of HRs of CKD and diabetes alone 90 days and one year postoperatively. (Table 19)
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Table 19. Combinations of different comorbid conditions and risk of death
Morbidities 90-day 1-year 5-year
CK D
CD CH F
DM
Number survival
% OR for
mortality 95% CI survival
% OR for
mortality 95 % CI survival
% OR for
mortality 95% CI
- - - - 15,164 99.7 reference 99.0 reference 92.1 reference
+ - - - 1,805 99.1 3.38 1.89–6.05 97.3 2.75 1.98 – 3.83 78.6 3.19 2.80–3.63
- + - - 1,272 99.4 2.39 1.12–5.12 97.9 2.19 1.45 – 3.31 82.9 2.41 2.05–2.83
+ + - - 334 98.2 6.92 2.19–16.43 94.9 5.40 3.23 – 9.04 72.4 4.46 3.47–5.47
- - - - 16,162 99.7 reference 99.0 reference 91.7 reference
+ - - - 2,000 99.0 3.72 2.21–6.24 97.2 2.79 2.06 – 3.80 78.4 3.06 2.70–3.46
- - + - 274 99.3 2.58 0.62–10.67 96.0 4.06 2.18 – 7.56 73.8 3.94 2.99–5.20
+ - + - 139 99.3 2.54 0.35–18.54 93.5 6.71 3.36 – 13.42 66.9 5.49 3.82–7.88
- - - - 15,241 99.7 reference 98.9 reference 91.7 reference
+ - - - 1,914 99.2 2.67 1.48–4.79 97.5 2.36 1.70 – 3.28 78.7 3.00 2.64–3.40
- - - + 1,195 99.7 0.85 0.26–2.74 98.7 1.19 0.70 – 2.03 87.7 1.56 1.29–1.88
+ - - + 225 96.9 10.84 4.84–24.31 92.0 8.15 4.9 – 13.51 68.7 5.05 3.77–6.77
CKD = chronic kidney disease (estimated glomerular filtration rate < 60 mL/minute/1.72 m2); CD= coronary disease; CHF = congestive heart failure; DM = diabetes mellitus;
OR = odds ratio
5.4.4. Mortality of AKI patients (Study 1)
A Kaplan-Meier survival plot shows remarkably poorer survival for those patients who had postoperative AKI after joint replacement. At ten years, over 70% of the non-AKI patients were alive, while only 36% of AKI patients survived. (Figure 5)
Figure 5. Survival of AKI patients
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