Abstract
Introduction: Knee arthroplasty is exposed to demographic changes as patients age. An analysis of risk factors for surgical treatment decisions in patients over 80 years old is crucial. This study compared perioperative complications between groups of patients undergoing primary knee arthroplasty, under 60 years old and over 80 years old.
Materials and Methods: For this retrospective study, data from 400 patients with primary cemented bi- and unicondylar total knee endoprosthesis during inpatient stay from 2017 to 2018 were analyzed. Patients aged 61–79 years (257) were excluded. An analysis of the remaining 143 patients was performed. The incidence of surgery-related and systemic complications (eg, urinary tract infections, electrolyte imbalances, and cases of pneumonia), the blood supply and C-reactive protein (CRP) as well as hemoglobin progression were compared across both age groups. Furthermore, a correlation between prevalent diseases and systemic complications were investigated. Statistical analysis was performed using IBM SPSS (Armonk, US).
Results: Data analyses showed a significant difference in the occurrence of systemic complications and blood transfusion between the age groups (P = 0.001, phi = 0.44; phi= 0.55, P = 0.001). Surgical complications did not differ significantly between the age groups. Age-typical pre-existing conditions, especially arterial hypertension (P = 0.003), showed a significant association with the occurrence of systemic complications. In addition, high postoperative CRP values in elderly patients revealed an association to systemic complications (P = 0.008).
Discussion and Conclusion: The study shows that primary cemented knee arthroplasty is a safe procedure without an increased incidence of surgical complications, even in elderly patients. The increased incidence of internal complications in octogenarians, in turn, should receive more attention in the perioperative course. The interdisciplinary preoperative optimization of pre-existing conditions and drug therapy, as well as close interdisciplinary assessments of elderly patients, should be ensured.
The proportion of patients over 75 years of age undergoing primary knee arthroplasty in Germany in 2021 was 30.5%.1 In the United States, the proportion of patients 80 years of age and older with primary knee arthroplasty is approximately 20%, according to continuous data from 2012 to 2020.2 As a result, understanding age-related risks in endoprosthesis implantation is significant and is being studied worldwide.3-5 Some studies describe an increased prevalence of all types of pre-existing conditions in older patients, for example, up to 16% diabetes mellitus II and up to 11% chronic obstructive pulmonary disease (COPD).6,7 Overall, about 81% of patients aged 85 years and older have at least two pre-existing conditions. For patients under 65 years of age, the proportion is still around 50%.8 Despite the higher incidence of pre-cancerous conditions in older patients, some studies describe no difference in the outcome of primary total knee arthroplasty (TKA) with younger patients, while others show a worse outcome in older patients.9-14 Due to an advanced age, some studies described prolonged hospital stays, increased complications, and blood transfusions, while others mainly consider pre-existing conditions to be a more important factor.6,13,15-17 To our knowledge, a comparison of patients under 60 years of age against octogenarians after primary total knee arthroplasty has not been conducted. Therefore, this retrospective study analyzed surgical and systemic complications after cemented bicondylar and unicondylar knee arthroplasty in patients under 60 years old and over 80 years old. The hypothesis was, that complications and transfusion management more often occurred in octogenarians than in the particularly young patient group.
Surgical and systemic complications, as well as laboratory chemical differences, were assessed (a) in relation to both the age of the patients and (b) previously existing diseases to form a risk profile of the patients before TKA. To perform the study, demographic data, pre-existing conditions, length of the hospital stay, every documented complication, transfusion rates and laboratory parameters were compared between the two age groups of patients.
Methods
Study Design
The present study was performed according to Strengthening the Reporting of Observational Studies in Epidemiology (STROBE).18 This study was conducted in the Department of Orthopedic Surgery of a University Hospital in Germany. The study was conducted in accordance with the Declaration of Helsinki and approved by the Ethics Committee of RUB-Bochum University, HDZ Bad Oeynhausen, (2018-625-f-S).
Study Protocol
Data from patients who underwent primary TKA during 2017 and 2018 were retrieved. Data were retrieved using Pegasos 7 (Nexus Marabu GmbH, Berlin) and collected in Microsoft Excel (Microsoft Corporation, Redmond, US). The following data were collected at admission: age, sex, side, body mass index (BMI), length of hospital stay, length of intensive care unit stay, and American Society of Anaesthesiologists physical status (ASA). The ASA classification counts from 1-6 (normal health, mild, severe, severe with life-threatening conditions, moribund diseases and brain dead).16 The following data were collected during the hospitalization: preoperative and postoperative hemoglobin (Hb) and C-reactive protein (CRP), the incidence of systemic and surgical complications, and the frequency of blood unit transfusions. Systemic complications included pulmonary, cardiac, urogenital, and neurologic complications, as well as electrolyte imbalances and exceptional laboratory parameter changes. Surgical-related complications included early infections, neurologic disorders, fractures, and ligament damage. If patient data was not accessible, the patient was excluded from the present investigation (Figure 1).
Workflow of research
Eligibility Criteria
All patients undergoing primary uncemented THA or cemented TKA were retrieved and their eligibility was assessed. The inclusion criteria were: (1) Patients with primary and secondary osteoarthritis, (2) Patients aged ≤40 and ≥80 years, (3) accessible patient data, (4) primary knee arthroplasty. The exclusion criteria were: (1) revision surgery, (2) any blood abnormalities, (3) pregnancy, (4) peripheral arteriovenous or neurologic ailment.
Perioperative Management
The arthroplasties were done with Smith & Nephew Genesis II CR/PS, Journey II BCS/CR (S&N GmbH, Londo, UK). For the TKA a standard medial parapatellar approach was used. A stationary or ambulant rehabilitation was organized prior to a hospital release.
Blood Unit Supply
Indication for the blood units transfusion was according to the restrictive Cochrane guidelines: Hb-levels over 8.0 g/dl no transfusion, between 7 to 9 with concomitant clinical symptoms such as dizziness, nausea, malaise or loss of appetite and Hb-levels under 8 g/dl indicated transfusion.17
Statistical Analyses
All statistical analyses were performed using the software IBM SPSS version 28 (IBM, Armonk, US). Metric scaled data were analysed by mean, standard deviation, and variance. Nominal, dichotomous data were analysed by Fischer’s exact test. Age, BMI, length of hospitalization, length of intensive care stay, pre- and postoperative Hb and frequency of transfusion were listed metrically. Sex, systemic and surgical complications were listed nominally. ASA Score and preconditions were listed ordinally. For the analysis of metric and nominally scaled variables, the t-test for independent samples, Variance-analyses, the Levene test, and the Welch tests were used. Cohen`s d (small .20; medium .50; large .80) and 95% interval were used as effect sizes. The effect size used was phi (small .10; medium .30; large .50). The significance level was set two-sided with α = 0.05.
Results
Recruitment Process
For this retrospective study, data from 400 patients with primary cemented knee arthroplasty from 2017 to 2018 during inpatient stays were analyzed. Patients aged 61–79 years (n=257) were excluded. An in-depth analysis of the remaining 143 patients was performed. In total, 85 of the patients were under 60 years of age, and 58 of the patients were 80 years of age or older (Figure 2).
Diagram of enrollment process
Patient Demographics
Data from 143 patients were analyzed. Of these patients, 92 of 143 were women and 51 of 143 were men; 58 of 143 of the patients were 80 years or older, and 85 of 143 of the patients were 60 years or younger. ASA Score I occurred in 12 of 143 patients, ASA Score II in 112 of 143 patients and ASA Score III in 19 of 143 patients. Elderly patients had a longer hospital stay and longer stay in the intermediate care (IMC) unit (Table 1).
Demographic data of the patients
Preconditions and Age
The analysis of the predisposition of pre-diseases showed that cardiac pre-diseases were more frequent at older ages than at younger ages. Furthermore, renal insufficiency and aspirin intake were found to be more frequent in old age (Table 2).
Pre-existing conditions and frequencies in the age groups
Preconditions and Systemic Complications
The study of the relationship between age-typical pre-existing conditions and systemic complications showed that patients with arterial hypertension, renal insufficiency, aspirin intake and COPD showed higher occurrence of systemic complications. Slightly significant results were shown for depression and systemic complications as well. The other pre-diseases investigated showed no correlation with the occurrence of complications (Table 3).
The occurrence of systemic complications in relation to age-typical preconditions (numbers in % show the frequency of precondition in group B)
Systemic and Surgical Complications
Overall, in this study, 25.17% systemic (n = 36) and 11.88% (n = 17) surgery-associated complications were postoperatively recorded during hospitalization (Table 4).
Systemic and surgical complications. Preoperative inflammatory and electrolyte balances with normal values and postoperative values that were either too low or too high were valued as persistent electrolyte shifts. Nitrite-positive urine samples were considered urinary tract infections.
Occurrence of Complications and Blood Supply
Older patients (group B) showed a more frequent occurrence of systemic complications compared to the younger age group (group A). Regarding surgical complications, no clustered occurrence was observed in either group. The need for postoperative blood transfusions was more frequent for the older patients (group B) (Table 5).
Occurrence of complications and blood transfusion in age groups
Postoperative Progression of Hemoglobin and C-Reactive Protein
Regarding the decrease in hemoglobin between preoperative collection and 7 days post operation, there was no difference between the age groups (df 1; η2part 0.00; P = 0.867) (Figure 3). However, the occurrence of anemia requiring transfusion was not related to the frequency of blood transfusions (CI −0.661/0.067; Cohen’s d −0.298; P = 0.133). Regarding the postoperative CRP course, the group of patients 80 years or older showed significantly higher CRP values (df 1; η2part 0.09; P = 0.001) (Figure 4). A correlation of the occurrence of high CRP levels on day 7 post operation with the appereance of systemic complications alone (CI −1.351/−0.446; Cohen’s d −0.900; P = 0.023), as well as in combination with the occurrence in elderly patients, was found (df 1; η2part 0.056; P = 0.008)
Progression of postoperative Hb concentration
Progression of pre- to postoperative C-reactive protein (CRP) concentration
Discussion
The most important finding of this study was the more frequent occurrence of complications classified as systemic in elderly patients compared to the younger age group (P = 0.001; phi = 0.44). Furthermore, the rate of performed blood transfusions was significantly different in older patients compared to younger patients (P = 0.001; phi = 0.55). Older age-related preconditions like arterial hypertension, renal insufficiency, aspirin intake and COPD showed more frequent systemic complications. Depression, which was more associated with younger patients, also showed an increased association with systemic complications. In addition, older patients showed significantly higher postoperative CRP values (P = 0.001; η2part = 0.09). These high CRP values also correlated with the occurrence of systemic complications in elderly patients (P = 0.008; η2part 0.056). No significant correlation was found between the age of the patients and the occurrence of surgical complications.
In this study, atrial fibrillation, renal insufficiency, hypercholesterolemia, and coronary artery disease were more common in older than in younger patients. Furthermore, aspirin was taken more frequently as a blood-thinning medication. These results are in line with the significantly more frequent ASA Score III with 25.8% in the > 80 years old patients, which agrees with other results in the literature, where the ASA-III-score is described in about 30% of octogenarians.19,20 Furthermore, elderly patients were significantly more likely to be equipped with assistive devices (51.7% age group > 80). These preconditions could have influenced the prolonged hospital stay in this group (12.9 + 7.2 days; P = 0.011). Berger et al18 showed a significantly increased risk of cardiac and pulmonary complications in octogenarians versus non-octogenarians after primary knee arthroplasty, for example, atrial fibrillation (20.8 vs. 10.4%; P < 0.001) and pneumonia (4.5 vs. 2.2%; P = 0.002). Similarly, in this study, octogenarians had increased systemic complications (phi = 0.44; Std. Ri (A)−2.9, (B)3.5; P = 0.001), with the most common postoperative complication being the occurrence of urinary tract infections (n = 14). The reason for this could be the initially increased lying time with prolonged postoperative bladder catheterization, or possibly an increased urinary stasis caused by medication. Regarding surgical complications, no difference in age groups during hospitalization was apparent (phi = 0.03; Std. Ri (A)−0.2, (B) 0.3; P = 0.799). Further investigations were also able to demonstrate that the risk of periprosthetic fractures and infections was not increased in octogenarians compared to the younger age group.14,21 In terms of hospitalization, this investigation revealed a longer stay in hospital for octogenarians. On the other hand, the investigation of da Casa et al23 showed a similar stay in the hospital between octogenarians and the control group. This could potentially be explained by the more cautious and later mobilization of elderly patients during their inpatient stays before rehabilitation. Another indicator for delayed mobility in this study could be the increased administration of blood products in elderly patients. Blood transfusion rates of approximately 9% in octogenarians after TKA have been reported in the literature.19 However, in this study, the increased administration of blood products in this clinic did not correlate with the postoperative incidence of anemia requiring transfusion between the two age groups As expected, prolonged elevated CRP levels showed an association with the occurrence of systemic complications, especially in elderly patients (df 1; η2part 0.056; P = 0.008). However, multiple systemic complications were grouped together, so the precise attribution to a specific complication was not possible. In this regard, further studies should be conducted. In other studies, CRP was directly related to periprosthetic infections in orthopedic patients and was found to be the most specific marker (87.10%).24-26 Nevertheless, other parallel causes for an elevated CRP value, especially in elderly patients, should be excluded during hospitalization. Among the pre-diseases described above, arterial hypertension, renal insufficiency, aspirin intake and COPD were shown to be associated with the occurrence of systemic complications. A reason of the high incidence for arterial hypertension could be the poor preoperative management of the disease. Unfortunately, prescribed/administered medication was not investigated in detail in this study, but aspirin is one of the most given medications for arterial hypertension. However, other studies have also linked arterial hypertension to the occurrence of complications. For example, Gupta et al27 showed an increased risk of unplanned reintubation (OR 3.52; P = 0.008), urinary tract infection (OR 2.08; P = 0.011), and postoperative transfusion (OR 1.90; P < 0.001) in patients 80 years or older. Further studies underlined an increased risk of complications in connection with cardiovascular and renal pre-diseases of the patients.24,25 Therefore, in preoperative planning, increased attention should be paid to a well-controlled arterial hypertension.
This study has weaknesses that should be mentioned. First, the results are taken from single-center data and can only be generalized with caution. The comparatively small group of patients 80 years of age or older may have led to bias in the results. In addition, some of the results show only a medium strength effect, which could be caused by a smaller number of patients. Furthermore, possible insufficient documentation of complications or previous illnesses in a retrospective study is not comprehensible. Moreover, regular follow-ups after hospitalization could not be investigated in the absence of data. More specific investigations of the relationship between CRP progression and individual systemic complications could have provided further information and must be carried out in the future. In the case of the relationship between pre-existing conditions and systemic complications, additional attention should be paid to possible drug treatment to prevent potential bias.
Conclusions
The current study shows that there are real differences in the occurrence of perioperative complications between a young and old age group after knee arthroplasty implantation. Older patients showed more frequent comorbidities, a longer period of hospitalization, a more frequent occurrence of systemic complications, and increased blood transfusion rates. Cardiac and renal diseases in elderly patients were shown to be high-risk factors for the development of systemic complications. The high CRP values shown in the older patients were connected to the appearance of systemic complications. No correlation between age and surgical complications could be found. To avoid the prolonged risk of hospital stays, age-typical pre-existing diseases, especially cardiac and renal diseases should receive increased attention. Increased CRP values should lead to broader investigations in the future for elderly patients. Preoperative interdisciplinary cooperation and optimization with geriatricians, for example, could reduce the number of complications associated with the primary implantation of a knee prosthesis during the hospitalization phase.
- Received October 24, 2022.
- Revision received May 3, 2023.
- Accepted July 12, 2023.
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