Keywords
infection - arthroplasty - predictor - diagnosis
Introduction
Total arthroplasties have a high success rate, improving pain and quality of life
for virtually all patients.1 However, their complications include periprosthetic joint infection (PJI), which
is hard to diagnose and treat, generally requiring an additional surgical intervention
and prolonged antibiotic therapy.[2]
Several protocols try to stratify the preoperative risk of infection and optimize
the patient most appropriately before the procedure.3 However, despite this care, PJI cases occur in all services.
According to the literature, the main avoidable factors associated with PJI are inadequate
glycemic control, obesity, malnutrition, and smoking. Additionally, authors cite adequate
antibiotic prophylaxis, asepsis with alcoholic chlorhexidine, reduced staff in the
operating room, and proper postoperative anticoagulation (to avoid hematoma formation)
as significant variables.[4]
As there are no Brazilian studies with a significant number of cases on this subject,
our work aims to evaluate the risk factors for PJI after an elective primary total
knee or hip arthroplasty.
Methods
This is a retrospective case-control study with 706 medical records of patients undergoing
elective primary total hip or knee arthroplasty from January to December 2018. The
institutional ethics committee and the Brazil Platform (Plataforma Brazil, CAAE number 30995420.2.0000.8114) approved the study.
We used the Strengthening the Reporting of Observational Studies in Epidemiology (STROBE)
initiative[5] that guides observational studies to outline the general methodology of our research.
Additionally, we followed the good clinical practices and the Declaration of Helsinki.
Data collection
The TechSallus (Felipe e Menezes LTDA. Salvador, Bahia, Brazil) software for hospital
medical records provided the required consecutive data. Variables included were gender,
age, operated joint, previous comorbidities, surgical time, laterality, and culture-identified
pathogen.
Inclusion criteria
-
Medical records from patients aged 40 to 90 years old.
-
Previous diagnosis of hip or knee osteoarthritis, Kellgren 3 or 4.
-
Incapacitating pain, diagnosed with the visual analog scale (VAS) for pain > 7, with
bad response to analgesia/joint infiltrations/motor physical therapy.
-
Patients undergoing primary total knee or hip arthroplasty in 2018.
-
Infection diagnosis followed the Musculoskeletal Infection Society criteria updated
in 2018:6 presence of an active fistula and two positive cultures with the same etiologic agent
or a minor criteria score of > 5 points confirm an infection; a minor criteria score
of < 2 excludes an infection. In patients with scores ranging from 2 to 5, 3 months
after the initial screening, we request erythrocyte sedimentation rate (ESR) and C-reactive
protein levels. If these test findings are abnormal, we perform an ultrasound-guided
joint puncture in the operating room for cytology and culture. A score > 5 at this
new staging confirms the infection.
Patient preparation and surgical technique
Patient preparation and surgical technique
Candidates for total arthroplasty went through a preparation program consisting of
the following:
-
Ten sessions of preoperative motor physical therapy during 5 consecutive weeks (2
sessions per week).
-
An orientation lecture for the patient and their family/caregivers about the surgical
procedure, risks, benefits, postoperative care, home adjustments, and routine medications.
-
Oral supplementation with Whey Protein, 50 mg per day, for 7 days before surgery.
-
Referral of morbidly obese patients to a specialized center before arthroplasty. If
required, the patient underwent bariatric surgery before the orthopedic procedure.
-
Referral of patients with hemoglobin A1C levels > 5.5% to the diabetes center for
control before surgery.
Hospitalization occurred on the same day of surgery, and patients were under an abbreviated
fasting protocol. Expected discharge was within 24 hours after the procedure, except
in cases of orthopedic or clinical complications.
All surgeries occurred in the same conventional operating rooms with no laminar flow.
Prophylactic antibiotic therapy consisted of cefuroxime sodium, 1.5 g, 1 hour before
skin incision (patients allergic to cephalosporin, penicillin, or both received vancomycin,
2 g, 2 hours before incision). We administrated tranexamic acid per our routine unless
formally contraindicated due to a previous severe thromboembolic event; the dosage
was 10 mg/kg of body weight applied during anesthetic induction. Spinal anesthesia
with sedation was the choice whenever there was no contraindication. Skin asepsis
used alcoholic chlorhexidine after previous local degermation. After placing the sterile
drapes, the exposed area was again treated with alcoholic chlorhexidine, dried, and
received an incise drape.
There was no routine urinary catheter placement. At the end of the procedure, we provided
a 7/8 elastic stocking with medium compression and requested follow-up radiographs.
The sterile dressing used, a hydrocolloid, remained occluded for the first 24 hours,
as long as there was no significant bleeding. In case of surgical wound bleeding and
issues with the dressing, we changed it using a sterile protocol at the hospital.
We resumed prophylactic anticoagulant (routine: enoxaparin, 0.5 mg/kg) administration
within 6 to 12 hours per hemoglobin curve findings. Additionally, we requested follow-up
tests at the end of the surgery, 6 hours after the procedure, and in the morning of
the following day.
The motor physical therapy protocol consisted of sitting the patient up in bed during
the immediate postoperative period and training gait with a walker and partial load
on the first postoperative days. The perioperative antibiotic agent administered was
sustained for up to 24 hours. At hospital discharge, patients got a prescription for
a simple analgesic agent, an opioid analgesic agent, and an oral anticoagulant (rivaroxaban,
10 mg/day for 30 days).
The patients received instructions on how to care for the surgical wound. They would
clean the wound with a neutral soap daily during the shower. Next, dry it with a separate
towel and a blow-dryer at a cool temperature. Keep the dressing up to suture removal
in the specialized outpatient clinic in the second or third postoperative week.
Total hip arthroplasty
Surgeons with a hip specialization and more than 5 years of experience performed all
arthroplasties via the right lateral approach (Hardinge, Inc. Berwyn, PA, USA)[7]. All patients received a cementless prosthesis, with the potential addition of acetabular
screws according to the initial press fit. The femoral component was from a taper
type.
We assign the tribological pair according to the following age distribution: patients
younger than 75 years old receive a ceramic femoral head and a highly cross-linked
polyethylene acetabular insert; those aged 75 or older receive a metallic femoral
head with the same insert. Simple, monofilament sutures closed the wound. We did not
use a suction drain or abduction triangle on a routine basis.
Total knee arthroplasty
All arthroplasties were performed by surgeons with a knee specialization and more
than 5 years of experience via the medial parapatellar approach.[8] All procedures were from the cemented type, with no addition of antibiotics to the
polymethylmethacrylate. The tribological pair consisted of metal-polyethylene. Simple,
monofilament sutures closed the wound. We did not use a suction drain on a routine
basis.
Statistical analysis
Statistical analysis used the descriptive method for nominal (proportion) and continuous
(mean and standard deviation) variables. Additionally, the Shapiro test was used to
classify the normality of continuous variables,9 while the Pearson chi-square test or the Fisher exact test were used to analyze nominal
variables.
Next, a univariate analysis assessed the influences of variables on the outcome using
individual logistic regression. The multivariate analysis included variables with
p < 0.20, based on a multiple logistic regression using the iteratively reweighted
least squares method. Odds ratio (OD) and 95% confidence intervals (95% CI) estimated
associations. Statistical significance was set at p < 0.05. The R software (R Foundation for Statistical Computing. Vienna, Austria)
were used to perform the analyzes.[10]
Results
Most patients were women (79.6%), with an afflicted right side (50.6%), and underwent
a total knee arthroplasty (61.3%). A total of 706 patients underwent surgery in 2018,
including 273 hip arthroplasties and 433 knee arthroplasties.
The prevalence of infection in the entire sample was 2.0% (14 cases). Infection rates
were 2.93% within the hip surgery group and 1.38% within the knee surgery group. The
number of periprosthetic infection cases was higher in females (2.31%) compared with
males (0.69%). Additionally, the right side was affected (2.52%) more often than the
left side (1.43%).
[Table 1] shows the epidemiological features of the case and control groups, and highlights
their homogeneity.
Table 1
|
Cases (n = 14)
|
Controls (n = 692)
|
p-value
|
|
Gender
|
13 female
1 male
|
549 female
143 male
|
0.21*
|
|
Side
|
9 at the right side
5 at the left side
|
348 at the right side
344 at the left side
|
0.29*
|
|
Prosthesis type
|
8 hip prostheses
6 knee prostheses
|
265 hip prostheses
427 knee prostheses
|
0.15*
|
The most common pathogen in cultures was Staphylococcus aureus, corresponding to 66.6% of the identified organisms, followed by coagulase-negative
Staphylococcus (11%) and Escherichia coli (11%). The multivariate analysis revealed that the factors associated with the development
of infection after hip or knee arthroplasty were a surgical time greater than 120 minutes
(OR = 6.55 [1.33–25.58]; p = 0.009) and diabetes (OR = 3.46 [1.16–10.88]; p = 0.025). [Table 2] shows all tests, both for the univariate and multivariate analyzes.
Table 2
|
Outcome
|
Univariate
|
Multivariate
|
|
p-value
|
OR (95% CI)
|
p-value
|
|
Gender
|
0.24
|
−
|
−
|
|
Prosthesis type
|
0.16
|
0.34 (0.10–1.09)
|
0.07
|
|
Side
|
0.30
|
−
|
−
|
|
Systemic arterial hypertension
|
0.67
|
−
|
−
|
|
Diabetes mellitus
|
0.02
|
3.46 (1.16–10.88)
|
< 0.05
|
|
Dyslipidemia
|
0.99
|
−
|
−
|
|
Hypothyroidism
|
0.80
|
−
|
−
|
|
Osteopenia
|
0.99
|
−
|
−
|
|
Osteoporosis
|
0.14
|
4.24 (0.21–27.10)
|
0.19
|
|
Age ≤ 65 years old
|
0.98
|
−
|
−
|
|
Age > 65 years old
|
0.50
|
−
|
−
|
|
Age ≥ 80 years old
|
0.59
|
−
|
−
|
|
Surgical time ≤ 60 minutes
|
0.56
|
−
|
−
|
|
Surgical time > 60 minutes
|
0.55
|
−
|
−
|
|
Surgical time ≥ 120 minutes
|
0.03
|
6.55 (1.33–25.58)
|
< 0.001
|
Discussion
The infection rate found in our study (2%) is consistent with the literature, ranging
from 1 to 2.5%.6 The main findings of our study were that a surgical time above 120 minutes and a
history of diabetes, even if compensated before surgery, represented significant risk
factors for PJI.
Although our findings corroborate data from the international literature, we demonstrated
that even patients with compensated blood sugar levels present an increased infection
rate. The literature reports serum glucose concentrations ranging from 6.1 to 10 mmol/L
and hemoglobin A1C levels of 7.0% as critical values.[3] Diabetes remained a risk factor even when we were more rigorous regarding the cut-off
point of hemoglobin A1C (< 5.6%). This fact evidences a potential immunological compromise
associated with the disease despite normal test results.[11]
Furthermore, the literature is controversial regarding a cut-off surgical time associated
with a higher infection rate.12 In our study, with an adequate sample for the Brazilian population, a surgical time
higher than 2 hours resulted in higher infection rates. This fact implies that a lengthier
exposure of the surgical wound increases the risk of infection. Additionally, the
surgical time is usually longer in complex orthopedic cases that may require higher
surgical exposures, along with greater intra- and postoperative bleeding.
Advanced age patients are more susceptible to prosthetic infections, mainly due to
comorbidities that lower the body's immune response.13 However, we did not detect an increase in the infection rate when stratifying patients
into three age groups (< 65, 65 to 80, and > 80 years old). Since most of the subjects
were aged 65 to 80, the other age groups potentially had a lower statistical power
in the comparative analysis.
There was no statistical difference in the infection rate after hip or knee arthroplasties.
Although there were more infection cases in females (13 females and 1 male), gender
did not represent an isolated risk factor for PJI in the statistical analysis. This
finding is not consistent with the literature, that shows a higher risk in males.14 The most isolated pathogen was Staphylococcus aureus, agreeing with the literature.[15]
It is worth mentioning that the preoperative investigation of methicillin-resistant
Staphylococcus aureus (MRSA) is not part of our protocol. Populational strategies guide antibiotic prophylaxis,
and we routinely use cefuroxime sodium at a 1.5 g dosage. However, if the patient
is a healthcare professional or an institutionalized subject (with a higher probability
of MRSA colonization), prophylaxis changes to vancomycin, 2 g, administered 2 hours
before skin incision.[11] In both scenarios, antibiotic therapy continues for 24 hours with the same drug
given before surgery.
Factors such as smoking and obesity are related to a higher PJI rate.3 However, since our study seeks a quantitative assessment of these variables—especially
the body mass index (BMI) and smoking time and intensity—the data are incomplete,
not allowing statistical analysis.
Thus, the main limitation of our research is information bias, as it is a retrospective
study with data from medical records, lacking complete, quantitative information on
smoking and obesity. On the other hand, our work has two strengths. The first strength
is its robust sample (706 cases) within the Brazilian scenario. The second strength
is the definition of a cut-off point of 2 hours of surgical time and diabetes (even
if controlled from a laboratory point of view) as risk factors for PJI in primary
elective total hip and knee arthroplasty procedures.
For future studies, our group aims to prospectively follow up and catalog all elective
arthroplasties in the service. We also plan a new study on the rate of complications,
including infection, in partial and total hip arthroplasties performed due to trauma
(femoral neck fractures).
Conclusion
Primary total knee or hip arthroplasties have a higher risk of infection when the
surgical procedure is protracted (over 120 minutes) and the patient presents diabetes
mellitus.
