The Journal of Arthroplasty 29 (2014) 1216–1218
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Mortality Following Revision Total Knee Arthroplasty: A Matched Cohort Study of Septic versus Aseptic Revisions Ho-Rim Choi, MD, Hany Bedair, MD The Harris Orthopedic Laboratory and Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts
a r t i c l e
i n f o
Article history: Received 24 July 2013 Accepted 26 November 2013 Keywords: total knee arthroplasty septic revision aseptic revision mortality longer-term
a b s t r a c t We report the medium-term mortality after septic versus aseptic revision total knee arthroplasty (TKA) and factors that can contribute to mortality in revision TKA. Mortality rates of 88 patients undergoing septic revision (septic group) were compared with age- and year of surgery-matched 88 patients of aseptic revision (aseptic group). The overall mortality after revision TKA was 10.7% at a median of 4 years of follow-up (range, 2–7 years). However, the mortality after septic revision (18%, 16/88) was six times higher than that of aseptic revision (3%, 3/88) (P = 0.003). Infections with Staphylococcus aureus and/or methicillin resistance was not associated with higher mortality rates. Multivariate analysis indicated that increased age (P b 0.001), higher ASA class (P = 0.002), and septic revision (P b 0.001) were identified as independent predictors of increased mortality after revision TKA. © 2014 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) is a safe and effective procedure for reducing pain and restoring function in patients with end-stage arthritis of the knee. Many studies have reported on the perioperative mortality rates for primary TKA ranging from 0.24% at 30 days [1] to 0.46% at 90 days [2]. Longer-term patient survival after primary TKA is reported to range from 65% to 90% at 5–10 years [3,4], and certainly is predicated in part on the patient’s age at the time of surgery. The cumulative revision rate for TKA for 11 years was 6.1% in a large national registry report depending upon the age of the patient at the time of TKA with the top three reasons for revision surgery being loosening, infection, and pain, with the most costly and devastating failure mode being infection [5]. While several studies have investigated the perioperative mortality rates for revision TKA, little information is available regarding longer-term rates of mortality in this group of patients and specifically in the setting of revision surgery for periprosthetic joint infection. The purpose of this study was to (1) investigate the mortality rates for revision TKA beyond the perioperative period, (2) assess whether revision surgery for septic failures increases mortality rates compared to those for aseptic failures, and (3) identify independent predictors of mortality after revision TKA. Materials & Methods Using an institution-based registry database from 2000 to 2010, 88 consecutive patients diagnosed with chronic periprosthetic joint The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2013.11.026. Reprint requests: Hany Bedair, MD, Department of Orthopedic Surgery, Massachusetts General Hospital, Boston, MA 02114. http://dx.doi.org/10.1016/j.arth.2013.11.026 0883-5403/© 2014 Elsevier Inc. All rights reserved.
infection following primary TKA (septic group) who were treated by component removal and planned staged re-implantation (two-stage) procedures in accordance with contemporary treatment protocols [6–8] were identified. These 88 patients were individually matched with 88 patients who underwent revision TKA for failure reasons other than sepsis (aseptic group) by age at the time of surgery (+/− 3 years), and year of revision surgery. The diagnosis of infection for the septic group was made based upon the modified musculoskeletal infection society diagnostic criteria [9,10]. The underlying reasons for the primary TKA in the septic group were osteoarthritis (69), posttraumatic osteoarthritis (5), rheumatoid arthritis (7), osteonecrosis (1), and unknown in 6 patients. For the aseptic group, the reasons for primary TKA were osteoarthritis (68), posttraumatic osteoarthritis (9), rheumatoid arthritis (3), osteonecrosis (1), and unknown in 7 patients. Of the 88 patients in the septic group who underwent the removal of the primary implants (first stage of two stage procedure), 67 patients (76%) underwent reimplantation (second stage) and 12 did not receive a second operation with 10 patients retaining their temporary spacers and two with a resection arthroplasty. Seven patients went on to arthrodesis and two to an above knee amputation. In the aseptic group, 69 patients had revision of both the femoral and tibial components and 19 patients had revision of only one component. Each patient’s mortality status was identified through the Social Security Death Index (SSDI) and was cross-referenced with institutional medical records. The SSDI is a database of death records created from the United States Social Security Administration’s Death Master File Extract (http://www.genealogybank.com/gbnk/ssdi/). The age at the time of death was recorded. Demographic data recorded included age at the time of revision surgery, gender, laterality of the procedure, body mass index (BMI) and primary diagnosis. The presence or
H.-R. Choi, H. Bedair / The Journal of Arthroplasty 29 (2014) 1216–1218 Table 1 Comparison of Patient Characteristics and Mortality in TKA Revision (88 Septic Versus 88 Aseptic).
Age at index, yr Age group at index, yr ≤65 N65 Gender Male Female Side Left Right Obesity (BMI) ≥30 b30 ASA Class 1–2 3–4 Charlson index Follow-up, yr Mortality Deceased Alive
Aseptic Cohort (n = 88)
66.6 ± 10.4
66.4 ± 10.8
40 (46%) 48 (54%)
42 (48%) 46 (52%)
45 (51%) 43 (49%)
43 (49%) 45 (51%)
P Value 0.90 0.88
0.88
0.89 42 (48%) 46 (52%)
44 (50%) 44 (50%)
46 (52%) 42 (48%)
43 (49%) 45 (51%)
49 (56%) 39 (44%) 1 (0-7) 3.0 (1-12)
61 (69%) 27 (31%) 1 (0-11) 4.5 (1-11)
16 (18%) 72 (82%)
3 (3%) 85 (97%)
Table 3 Multivariate Predictors of Mortality for Septic Group Only (n = 88). Variable
P value
Odds Ratio
95% CI
Older age at index, yr Gender Side Obesity ASA (3–4 vs. 1–2) Charlson score Staphylococcus aureus Methicillin resistance
0.003a 0.93 0.28 0.68 0.033a 0.039a 0.17 0.52
1.13
1.03–1.24
4.7 1.5
1.1–20.9 1.1–2.2
a Statistically significant independent predictor of mortality. CI = confidence interval.
0.76
Results 0.09
0.42 0.19 0.003a
Charlson index and follow-up are median (range) compared by Mann–Whitney U-test. BMI, body mass index. a Statistically higher incidence of mortality in septic cohort.
history of the following medical comorbidities was identified: myocardial infarction, congestive heart failure, peripheral vascular disease, cerebrovascular disease, dementia, chronic pulmonary disease, connective tissue disease, ulcer disease, liver disease, diabetes mellitus, hemiplegia, renal disease, leukemia, lymphoma, or any tumor, metastatic cancer, acquired immunodeficiency syndrome. These parameters were analyzed as part of the Charlson Comorbidity Index (CCI) [11]. In addition, the patient’s American Society of Anesthesiologists (ASA) physical status classification score [12] was recorded. In the septic group, the causative microorganisms and their antimicrobial resistance (methicillin-resistant versus methicillinsensitive) patterns were also recorded. The two groups were evaluated using chi-square tests for categorical variables. Paired t-tests and Mann–Whitney U-test were used to compare continuous variables. Multivariate logistic regression was performed to identify independent predictors of mortality with eight candidate variables (age, gender, side, BMI, ASA level, CCI, follow-up, and septic vs. aseptic revision) with the likelihood ratio test used to assess significance. Odds ratios and 95% confidence intervals were derived for significant independent predictors of mortality. The mortality of the study groups was also compared with the natural mortality of general population (http://www.cdc.gov/nchs/fastats/ deaths.htm). Two-tailed values of P b 0.05 were considered significant. Statistical analysis was performed using SPSS version 19.0 (SPSS Inc/IBM, Chicago, IL).
Table 2 Multivariate Predictors of Mortality for Entire Cohort (n = 196).
Overall mortality after revision TKA was 10.7% (19/176) at a median of 4 years (interquartile range: 2–7 years). The mortality rate of the septic group (18%, 16/88) was significantly higher than that of the aseptic group (3%, 3/88) (P = 0.003). Mean age at the time of death was 79.2 and 84.3 years (P = 0.45) in the septic and aseptic groups, respectively. Patient demographic and comorbidity data were similar between the septic and aseptic groups with regards to age, gender, side, BMI, CCI, ASA and follow-up period (Table 1). Among the 88 patients in the septic group, eight of the 39 (21%) patients with Staphylococcus aureus (S. aureus) microorganism died compared to 8 of 49 (16%) patients with non S. aureus (P = 0.78). Six of 26 (23%) with resistant bacteria died compared to 10 of 62 (16%) with non-resistant bacteria (P = 0.55). Power given the sample sizes was low and analysis indicated that 90 patients per group would be needed to detect a 20% difference in mortality rates based on Fisher’s exact test. Multivariate logistic regression analysis demonstrated that in addition to an increased age (N 65 years) at the time of revision surgery (P b 0.001, OR 1.13; CI 1.05–1.21), revision for septic failure (P b 0.001, OR 7.7; CI 2.0–32.1) and ASA Class III or IV (P = 0.002, OR 6.6; CI 1.7–25.7) were independent predictors of mortality among the entire cohort (Table 2). Multivariate analysis on the septic group only, increased age (N65 years), higher ASA class, and higher CCI were identified as independent predictor of mortality (Table 3). Comparison of the mortality between the study groups and general population demonstrated that overall mortality of revision TKA was higher than that of general population based on each age group (Fig. 1).
Mortality Rates 80 70 60
mortality (%)
Variable
Septic Cohort (n = 88)
1217
50 40 30 20 10
Variable
P value
Odds Ratio
95% CI
Older age at index, yr Gender Side Obesity ASA (3–4 vs. 1–2) Charlson score Septic vs. aseptic Follow-up time, yr
b0.001a 0.31 0.16 0.43 0.002a 0.23 b0.001a 0.94
1.13
1.05–1.21
a
0 35-44
45-54
55-64
65-74
75-84
85-
Age (years) 6.6
1.7–25.7
7.7
2.0–32.1
Statistically significant independent predictor of mortality.
Septic group
Aseptic group
General population
overall (septic+aseptic)
Fig. 1. Overall mortality of revision TKA is higher than that of general population based on each age group.
1218
H.-R. Choi, H. Bedair / The Journal of Arthroplasty 29 (2014) 1216–1218
Discussion While there are reports of early perioperative mortality after primary and revision TKA, there is paucity of data regarding longerterm mortality after revision TKA, particularly after revisions for septic failures. In terms of longer-term mortality after primary TKA, survival rates have been reported to be 88.7% at 5 years and 64.4% at 9 years by Ozawa et al [4]. Clement et al [3] also reported that overall survivorship after TKA was 99% at one year, 90% at five years, and 84% at ten years. In the setting of revision, early perioperative mortality after revision TKA was reported to be 1.1% in the Medicare population [13]. Fehring et al [14] reported that perioperative mortality for revision knee surgery was 0.3%. In the present study, overall mortality after revision TKA was 10.7% at a median of 4 years after surgery, which was similar to previous reports for primary TKA over a similar timeframe [3,4,15]. However, mortality after septic revision was 18%, which was six times higher than that of aseptic revision (3%) and about two times higher compared to previous reports after primary TKA [3,4]. This finding suggests that revision for septic failures appears strongly correlated with increased mortality. In terms of risk factors that may predict mortality after arthroplasty, patient’s medical comorbidity and increasing age are well-known factors associated with an increased complication and mortality after TKA [1–3,16]. Clement et al [3] demonstrated that greater mortality rate was associated with increasing age, ASA grade, BMI and rheumatoid disease. Parvizi et al [1] also reported that age (more than seventy years), primary knee surgery (compared with revision), use of a cemented prosthesis, preexisting cardiopulmonary disease, and simultaneous bilateral arthroplasty were related to increased mortality after TKA. On the other hand, Fehring et al [14] reported that perioperative mortality rates following revision TKA were extremely low among all age groups, therefore, the age of patients undergoing revision surgery should not be the sole determinant of perioperative survival. In the present study, older age, higher ASA grade, and septic revision were identified as predictors of increased mortality after revision TKA. In addition, increased age, higher ASA grade, and higher CCI were identified as independent predictors of increased mortality for those patients undergoing revision for sepsis. While male gender was demonstrated as risk factor for increased early postoperative mortality following TKA in recent studies [17,18], male gender was not related to increased mortality in our study. There are several limitations in this study. First as a retrospective study, we determined the status of patient using institution based registry and the social security death index database, which might have underestimated the number of patients who were deceased. Second, we could not exactly match severity of revision surgeries between the groups. Although we tried to select control patients with extensive revision involving both femoral and tibial components to
avoid a selection bias, some less extensive revision cases were inevitably included in the aseptic group after the matching algorithm. Thirdly, we were unable to ascertain whether infection itself directly contributed to higher mortality rates, or whether an increased number of surgeries (two procedures for the treatment of chronic infection) was related to higher mortality rates. In summary, overall mortality after revision TKA was comparable to that of primary surgery at a median of 4 years after surgery. Most interestingly, revision for sepsis correlated with an approximate six fold increase in the rate of mortality compared to revisions for aseptic failures and was identified as an independent risk factor for increased mortality with an odds ratio of 7.7. Findings of this study are of primary importance for surgeons, patients, and their families to understand longer-term mortality risk of septic revision and can be utilized in preoperative risk stratification of patients that may ultimately impact treatment decisions.
References 1. Parvizi J, Sullivan TA, Trousdale RT, et al. Thirty-day mortality after total knee arthroplasty. J Bone Joint Surg Am 2001;83-A:1157. 2. Gill GS, Mills D, Joshi AB. Mortality following primary total knee arthroplasty. J Bone Joint Surg Am 2003;85-A:432. 3. Clement ND, Jenkins PJ, Brenkel IJ, et al. Predictors of mortality after total knee replacement: a ten-year survivorship analysis. J Bone Joint Surg Br 2012;94:200. 4. Ohzawa S, Takahara Y, Furumatsu T, et al. Patient survival after total knee arthroplasty. Acta Med Okayama 2001;55:295. 5. Australian Orthopaedic Association National Joint Replacement Registry. Available at: https://aoanjrr.dmac.adelaide.edu.au/en/annual-reports-2012, 2012. 6. Blom AW, Brown J, Taylor AH, et al. Infection after total knee arthroplasty. J Bone Joint Surg Br 2004;86:688. 7. Garvin KL, Cordero GX. Infected total knee arthroplasty: diagnosis and treatment. Instr Course Lect 2008;57:305. 8. Hanssen AD, Rand JA. Evaluation and treatment of infection at the site of a total hip or knee arthroplasty. Instr Course Lect 1999;48:111. 9. Parvizi J, Zmistowski B, Berbari EF, et al. New definition for periprosthetic joint infection: from the Workgroup of the Musculoskeletal Infection Society. Clin Orthop Relat Res 2011;469:2992. 10. Workgroup. New definition for periprosthetic joint infection. J Arthroplasty 2011;26:1136. 11. Charlson ME, Pompei P, Ales KL, et al. A new method of classifying prognostic comorbidity in longitudinal studies: development and validation. J Chronic Dis 1987;40:373. 12. Dripps RD, Lamont A, Eckenhoff JE. The role of anesthesia in surgical mortality. JAMA 1961;178:261. 13. Mahomed NN, Barrett J, Katz JN, et al. Epidemiology of total knee replacement in the United States Medicare population. J Bone Joint Surg Am 2005;87:1222. 14. Fehring TK, Odum SM, Fehring K, et al. Mortality following revision joint arthroplasty: is age a factor? Orthopedics 2010;33:715. 15. Schroder HM, Kristensen PW, Petersen MB, et al. Patient survival after total knee arthroplasty. 5-year data in 926 patients. Acta Orthop Scand 1998;69:35. 16. Parry MC, Smith AJ, Blom AW. Early death following primary total knee arthroplasty. J Bone Joint Surg Am 2011;93:948. 17. Singh JA, Kundukulam J, Riddle DL, et al. Early postoperative mortality following joint arthroplasty: a systematic review. J Rheumatol 2011;38:1507. 18. Singh JA, Lewallen DG. Ninety-day mortality in patients undergoing elective total hip or total knee arthroplasty. J Arthroplasty 2012;27:1417.
Contents lists available at ScienceDirect
The Journal of Arthroplasty journal homepage: www.arthroplastyjournal.org
Mortality Following Revision Total Knee Arthroplasty: A Matched Cohort Study of Septic versus Aseptic Revisions Ho-Rim Choi, MD, Hany Bedair, MD The Harris Orthopedic Laboratory and Department of Orthopaedic Surgery, Massachusetts General Hospital, Boston, Massachusetts
a r t i c l e
i n f o
Article history: Received 24 July 2013 Accepted 26 November 2013 Keywords: total knee arthroplasty septic revision aseptic revision mortality longer-term
a b s t r a c t We report the medium-term mortality after septic versus aseptic revision total knee arthroplasty (TKA) and factors that can contribute to mortality in revision TKA. Mortality rates of 88 patients undergoing septic revision (septic group) were compared with age- and year of surgery-matched 88 patients of aseptic revision (aseptic group). The overall mortality after revision TKA was 10.7% at a median of 4 years of follow-up (range, 2–7 years). However, the mortality after septic revision (18%, 16/88) was six times higher than that of aseptic revision (3%, 3/88) (P = 0.003). Infections with Staphylococcus aureus and/or methicillin resistance was not associated with higher mortality rates. Multivariate analysis indicated that increased age (P b 0.001), higher ASA class (P = 0.002), and septic revision (P b 0.001) were identified as independent predictors of increased mortality after revision TKA. © 2014 Elsevier Inc. All rights reserved.
Total knee arthroplasty (TKA) is a safe and effective procedure for reducing pain and restoring function in patients with end-stage arthritis of the knee. Many studies have reported on the perioperative mortality rates for primary TKA ranging from 0.24% at 30 days [1] to 0.46% at 90 days [2]. Longer-term patient survival after primary TKA is reported to range from 65% to 90% at 5–10 years [3,4], and certainly is predicated in part on the patient’s age at the time of surgery. The cumulative revision rate for TKA for 11 years was 6.1% in a large national registry report depending upon the age of the patient at the time of TKA with the top three reasons for revision surgery being loosening, infection, and pain, with the most costly and devastating failure mode being infection [5]. While several studies have investigated the perioperative mortality rates for revision TKA, little information is available regarding longer-term rates of mortality in this group of patients and specifically in the setting of revision surgery for periprosthetic joint infection. The purpose of this study was to (1) investigate the mortality rates for revision TKA beyond the perioperative period, (2) assess whether revision surgery for septic failures increases mortality rates compared to those for aseptic failures, and (3) identify independent predictors of mortality after revision TKA. Materials & Methods Using an institution-based registry database from 2000 to 2010, 88 consecutive patients diagnosed with chronic periprosthetic joint The Conflict of Interest statement associated with this article can be found at http:// dx.doi.org/10.1016/j.arth.2013.11.026. Reprint requests: Hany Bedair, MD, Department of Orthopedic Surgery, Massachusetts General Hospital, Boston, MA 02114. http://dx.doi.org/10.1016/j.arth.2013.11.026 0883-5403/© 2014 Elsevier Inc. All rights reserved.
infection following primary TKA (septic group) who were treated by component removal and planned staged re-implantation (two-stage) procedures in accordance with contemporary treatment protocols [6–8] were identified. These 88 patients were individually matched with 88 patients who underwent revision TKA for failure reasons other than sepsis (aseptic group) by age at the time of surgery (+/− 3 years), and year of revision surgery. The diagnosis of infection for the septic group was made based upon the modified musculoskeletal infection society diagnostic criteria [9,10]. The underlying reasons for the primary TKA in the septic group were osteoarthritis (69), posttraumatic osteoarthritis (5), rheumatoid arthritis (7), osteonecrosis (1), and unknown in 6 patients. For the aseptic group, the reasons for primary TKA were osteoarthritis (68), posttraumatic osteoarthritis (9), rheumatoid arthritis (3), osteonecrosis (1), and unknown in 7 patients. Of the 88 patients in the septic group who underwent the removal of the primary implants (first stage of two stage procedure), 67 patients (76%) underwent reimplantation (second stage) and 12 did not receive a second operation with 10 patients retaining their temporary spacers and two with a resection arthroplasty. Seven patients went on to arthrodesis and two to an above knee amputation. In the aseptic group, 69 patients had revision of both the femoral and tibial components and 19 patients had revision of only one component. Each patient’s mortality status was identified through the Social Security Death Index (SSDI) and was cross-referenced with institutional medical records. The SSDI is a database of death records created from the United States Social Security Administration’s Death Master File Extract (http://www.genealogybank.com/gbnk/ssdi/). The age at the time of death was recorded. Demographic data recorded included age at the time of revision surgery, gender, laterality of the procedure, body mass index (BMI) and primary diagnosis. The presence or
H.-R. Choi, H. Bedair / The Journal of Arthroplasty 29 (2014) 1216–1218 Table 1 Comparison of Patient Characteristics and Mortality in TKA Revision (88 Septic Versus 88 Aseptic).
Age at index, yr Age group at index, yr ≤65 N65 Gender Male Female Side Left Right Obesity (BMI) ≥30 b30 ASA Class 1–2 3–4 Charlson index Follow-up, yr Mortality Deceased Alive
Aseptic Cohort (n = 88)
66.6 ± 10.4
66.4 ± 10.8
40 (46%) 48 (54%)
42 (48%) 46 (52%)
45 (51%) 43 (49%)
43 (49%) 45 (51%)
P Value 0.90 0.88
0.88
0.89 42 (48%) 46 (52%)
44 (50%) 44 (50%)
46 (52%) 42 (48%)
43 (49%) 45 (51%)
49 (56%) 39 (44%) 1 (0-7) 3.0 (1-12)
61 (69%) 27 (31%) 1 (0-11) 4.5 (1-11)
16 (18%) 72 (82%)
3 (3%) 85 (97%)
Table 3 Multivariate Predictors of Mortality for Septic Group Only (n = 88). Variable
P value
Odds Ratio
95% CI
Older age at index, yr Gender Side Obesity ASA (3–4 vs. 1–2) Charlson score Staphylococcus aureus Methicillin resistance
0.003a 0.93 0.28 0.68 0.033a 0.039a 0.17 0.52
1.13
1.03–1.24
4.7 1.5
1.1–20.9 1.1–2.2
a Statistically significant independent predictor of mortality. CI = confidence interval.
0.76
Results 0.09
0.42 0.19 0.003a
Charlson index and follow-up are median (range) compared by Mann–Whitney U-test. BMI, body mass index. a Statistically higher incidence of mortality in septic cohort.
history of the following medical comorbidities was identified: myocardial infarction, congestive heart failure, peripheral vascular disease, cerebrovascular disease, dementia, chronic pulmonary disease, connective tissue disease, ulcer disease, liver disease, diabetes mellitus, hemiplegia, renal disease, leukemia, lymphoma, or any tumor, metastatic cancer, acquired immunodeficiency syndrome. These parameters were analyzed as part of the Charlson Comorbidity Index (CCI) [11]. In addition, the patient’s American Society of Anesthesiologists (ASA) physical status classification score [12] was recorded. In the septic group, the causative microorganisms and their antimicrobial resistance (methicillin-resistant versus methicillinsensitive) patterns were also recorded. The two groups were evaluated using chi-square tests for categorical variables. Paired t-tests and Mann–Whitney U-test were used to compare continuous variables. Multivariate logistic regression was performed to identify independent predictors of mortality with eight candidate variables (age, gender, side, BMI, ASA level, CCI, follow-up, and septic vs. aseptic revision) with the likelihood ratio test used to assess significance. Odds ratios and 95% confidence intervals were derived for significant independent predictors of mortality. The mortality of the study groups was also compared with the natural mortality of general population (http://www.cdc.gov/nchs/fastats/ deaths.htm). Two-tailed values of P b 0.05 were considered significant. Statistical analysis was performed using SPSS version 19.0 (SPSS Inc/IBM, Chicago, IL).
Table 2 Multivariate Predictors of Mortality for Entire Cohort (n = 196).
Overall mortality after revision TKA was 10.7% (19/176) at a median of 4 years (interquartile range: 2–7 years). The mortality rate of the septic group (18%, 16/88) was significantly higher than that of the aseptic group (3%, 3/88) (P = 0.003). Mean age at the time of death was 79.2 and 84.3 years (P = 0.45) in the septic and aseptic groups, respectively. Patient demographic and comorbidity data were similar between the septic and aseptic groups with regards to age, gender, side, BMI, CCI, ASA and follow-up period (Table 1). Among the 88 patients in the septic group, eight of the 39 (21%) patients with Staphylococcus aureus (S. aureus) microorganism died compared to 8 of 49 (16%) patients with non S. aureus (P = 0.78). Six of 26 (23%) with resistant bacteria died compared to 10 of 62 (16%) with non-resistant bacteria (P = 0.55). Power given the sample sizes was low and analysis indicated that 90 patients per group would be needed to detect a 20% difference in mortality rates based on Fisher’s exact test. Multivariate logistic regression analysis demonstrated that in addition to an increased age (N 65 years) at the time of revision surgery (P b 0.001, OR 1.13; CI 1.05–1.21), revision for septic failure (P b 0.001, OR 7.7; CI 2.0–32.1) and ASA Class III or IV (P = 0.002, OR 6.6; CI 1.7–25.7) were independent predictors of mortality among the entire cohort (Table 2). Multivariate analysis on the septic group only, increased age (N65 years), higher ASA class, and higher CCI were identified as independent predictor of mortality (Table 3). Comparison of the mortality between the study groups and general population demonstrated that overall mortality of revision TKA was higher than that of general population based on each age group (Fig. 1).
Mortality Rates 80 70 60
mortality (%)
Variable
Septic Cohort (n = 88)
1217
50 40 30 20 10
Variable
P value
Odds Ratio
95% CI
Older age at index, yr Gender Side Obesity ASA (3–4 vs. 1–2) Charlson score Septic vs. aseptic Follow-up time, yr
b0.001a 0.31 0.16 0.43 0.002a 0.23 b0.001a 0.94
1.13
1.05–1.21
a
0 35-44
45-54
55-64
65-74
75-84
85-
Age (years) 6.6
1.7–25.7
7.7
2.0–32.1
Statistically significant independent predictor of mortality.
Septic group
Aseptic group
General population
overall (septic+aseptic)
Fig. 1. Overall mortality of revision TKA is higher than that of general population based on each age group.
1218
H.-R. Choi, H. Bedair / The Journal of Arthroplasty 29 (2014) 1216–1218
Discussion While there are reports of early perioperative mortality after primary and revision TKA, there is paucity of data regarding longerterm mortality after revision TKA, particularly after revisions for septic failures. In terms of longer-term mortality after primary TKA, survival rates have been reported to be 88.7% at 5 years and 64.4% at 9 years by Ozawa et al [4]. Clement et al [3] also reported that overall survivorship after TKA was 99% at one year, 90% at five years, and 84% at ten years. In the setting of revision, early perioperative mortality after revision TKA was reported to be 1.1% in the Medicare population [13]. Fehring et al [14] reported that perioperative mortality for revision knee surgery was 0.3%. In the present study, overall mortality after revision TKA was 10.7% at a median of 4 years after surgery, which was similar to previous reports for primary TKA over a similar timeframe [3,4,15]. However, mortality after septic revision was 18%, which was six times higher than that of aseptic revision (3%) and about two times higher compared to previous reports after primary TKA [3,4]. This finding suggests that revision for septic failures appears strongly correlated with increased mortality. In terms of risk factors that may predict mortality after arthroplasty, patient’s medical comorbidity and increasing age are well-known factors associated with an increased complication and mortality after TKA [1–3,16]. Clement et al [3] demonstrated that greater mortality rate was associated with increasing age, ASA grade, BMI and rheumatoid disease. Parvizi et al [1] also reported that age (more than seventy years), primary knee surgery (compared with revision), use of a cemented prosthesis, preexisting cardiopulmonary disease, and simultaneous bilateral arthroplasty were related to increased mortality after TKA. On the other hand, Fehring et al [14] reported that perioperative mortality rates following revision TKA were extremely low among all age groups, therefore, the age of patients undergoing revision surgery should not be the sole determinant of perioperative survival. In the present study, older age, higher ASA grade, and septic revision were identified as predictors of increased mortality after revision TKA. In addition, increased age, higher ASA grade, and higher CCI were identified as independent predictors of increased mortality for those patients undergoing revision for sepsis. While male gender was demonstrated as risk factor for increased early postoperative mortality following TKA in recent studies [17,18], male gender was not related to increased mortality in our study. There are several limitations in this study. First as a retrospective study, we determined the status of patient using institution based registry and the social security death index database, which might have underestimated the number of patients who were deceased. Second, we could not exactly match severity of revision surgeries between the groups. Although we tried to select control patients with extensive revision involving both femoral and tibial components to
avoid a selection bias, some less extensive revision cases were inevitably included in the aseptic group after the matching algorithm. Thirdly, we were unable to ascertain whether infection itself directly contributed to higher mortality rates, or whether an increased number of surgeries (two procedures for the treatment of chronic infection) was related to higher mortality rates. In summary, overall mortality after revision TKA was comparable to that of primary surgery at a median of 4 years after surgery. Most interestingly, revision for sepsis correlated with an approximate six fold increase in the rate of mortality compared to revisions for aseptic failures and was identified as an independent risk factor for increased mortality with an odds ratio of 7.7. Findings of this study are of primary importance for surgeons, patients, and their families to understand longer-term mortality risk of septic revision and can be utilized in preoperative risk stratification of patients that may ultimately impact treatment decisions.
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