Perioperative morbidity in total knee arthroplasty

Introduction As the life expectancy and weight of patients are increasing, more old and obese patients are undergoing total knee arthroplasty (TKA). TKA may lead to several perioperative complications. These include anesthesia-related risks, exacerbation of comorbid medical issues and complications of surgical procedure. We have no studies reporting medical complications following TKA among our population. This study aimed to evaluate perioperative complications of TKA and to identify the related risk factors. Methods It was a monocentric retrospective including 410 observations in the local TKA registry. Data of patients operated for primary unilateral TKA during the period from January 2014 to December 2017 were reviewed. All patients had standardized protocols of anesthesia and post operative care for three days following surgery. Multivariate logistic regression was used to identify the predicting factors for complications. Results Incidence of perioperative complications was 37.1%. The most frequent were per operative hypotension (14.1%) and postoperative desaturation (21.7%, including pulmonary embolism in 2.4%). Multivariate logistic regression analysis identified: age ≥ 65 years (OR=1.9; p=0.006), respiratory diseases (OR=1.8; p=0.042) and general anesthesia (OR=2.8; p=0.009) as significant risk factors for any complications. Loss of autonomy (OR=4.8; p <0.001) and general anesthesia (OR=2.6; p=0.03) were significant risk factors for hypotension. Age ≥ 65 years (OR=2.6;p<0.001), female gender (OR=4.3;p=0.006) and respiratory diseases(OR=1.9;p=0.02) were associated with postoperative desaturation. Conclusion This study highlighted hemodynamic and respiratory complications as the most common early complications in TKA. Age ≥ 65years, general anesthesia and respiratory diseases were significant risk factors.


Introduction
Total knee arthroplasty (TKA) may be needed to alleviate pain and restore the ability of daily living's activities in advanced stages of Osteoarthritis. In the United States, logistic regression modelling suggests the incidence of TKA is expected to increase 69% by 2050 compared to 2012, from 429 procedures/100,000 in 2012 to 725 procedures/100,000 in 2050 [1]. In Tunisia although TKA has become a rife procedure because of the ageing of our population and the rising prevalence of overweight especially among women [2]. But, the prevalence of TKA is not known due to the lack of registries in orthopaedics. As we mentioned its drastic progression, TKA may lead to several perioperative complications. Adverse outcomes include acute myocardial infarction [3,4], venous thromboembolism [5], pulmonary complications [6], sepsis [7,8] and non myocardial cardiac complications [3,7,9]. Few well-designed studies, have examined all complications following TKA and with adjustment for potential confounding variables, have focused on risk factors such as age, sex, weight, specific medical co morbidities and surgical parameters and their effect on postoperative mortality, morbidity, and length of hospital stay following TKA. The aim of our study was to elucidate short-term complications occurring intra operatively and during the three days following primary TKA. The second aim was to identify risk factors for such complications.

Results
The mean age of our population was 65.8±7.8 years. The majority of the patients were female in 85.1% with a BMI of ≥30 kg/m 2 in 74.6% (  Table 3 and for length of stay were reported in (Table 4). Multivariate analysis ascertained that a patient older than 65 years was the most important risk factor for the development of one or more perioperative complications (Table 5).

Discussion
In our study we wanted to expose intra operative and early three days medical post operative complications while patients were admitted in postoperative recovery unit and to assess their predictive risk factors. We didn't report any death during the study period. In our study, 37.1% of the patients developed one or more complication.  [13]. BMI ≥40 kg/ m 2 was the most important risk factors for developing of any complication in one study [4]. In our study we didn't reported any case of myocardial infarction. In contrast, many studies showed that cardiac diseases were associated with the risk of a postoperative nonsurgical complication [9,13,14,19]. Few patients in our study suffered from either chronic heart failure or coronary artery diseases. Postoperative desaturation was the first highest incidence complication and the major finding that caught our attention while settling our TKA register, as we already mentioned. Most of the cases of postoperative desaturation (9.3%) happened early in postoperative period, lasted few hours and were classified as BCIS. In fact, its incidence following TKA is not clearly identified in literature since there is no agreed definition of this syndrome and thus it may be misdiagnosed.
Donaldson et al, recently proposed a severity classification of BCIS that we followed in our study [20]. In our study, an age over 65 years with poor pre-existing physical reserve were found as risk factor for  [20].
BCIS incidence seemed to be high in our patients. It may be explained by the poor pre-existing physical reserve and chronic respiratory diseases. In our study the rate of atelectasis among our patients was 9.8%. Only, old age was a risk factor for atelectasis. Austin et al. [21] found in a prospective study including 1058 TKA that among postoperative hypoxemia, atelectasis was the most common etiology with a rate of 33%. The main risk factors for developing atelectasis in the surgical patient include: general anaesthesia, the site of surgery, high BMI, blood transfusion and diabetes mellitus [21]. In our study, the rate of atelectasis seems to be high as regional anesthesia was performed in most patients. It can be explained by:

Competing interests
The authors declare no competing interest.

Authors' contributions
All the authors have read and agreed to the final manuscript.

Acknowledgements
We thank Professor Bechir Zouari for her contribution in statistical analysis.