Keywords fluoroscopy - nerve block - osteoarthritis, knee - pain - visual analog pain scale
Introduction
Knee osteoarthritis (KOA) is the most prevalent chronic joint disease,[1 ]
[2 ] affecting 12% of subjects over 60.[3 ] Its prevalence rate increases with age, ranging from 4.2 to 15.5. Approximately
80% of KOA patients are aged 65 years or older. Diagnosis may rely on imaging methods,
such as weight-bearing plain radiographs.
Around 60% of patients with KOA present clinical manifestations,[4 ]
[5 ] especially joint stiffness, and muscle atrophy. There is a 25% rate of patients
presenting with severe, limiting arthralgia.[6 ] Treatment includes noninvasive clinical therapy with medications, physical therapy,
and rehabilitation, and minimally invasive treatment with intra- and periarticular
injections.[7 ] Many patients suffer from chronic, incapacitating pain refractory to clinical treatment.
For these cases, surgical treatment is indicated, including arthroscopy, osteotomies,
and arthroplasties with implants, depending on patients' age and the degree of joint
involvement.[8 ]
As an alternative to surgical treatment, Choi et al.[9 ] described the genicular nerve block (GNB) technique, which has been effective in
relieving pain and improving joint functionality in KOA patients.[9 ]
[10 ]
[11 ]
[12 ]
[13 ] Therefore, it is a new option for relieving refractory chronic pain in these subjects.
There are four genicular nerves: superomedial, superolateral, inferomedial, and inferolateral.
The traditional technique blocks all nerves, except for the inferolateral genicular
nerve due to its proximity to the common fibular nerve and risk of neuropraxia.[14 ]
Ultrasound and fluoroscopy are two imaging methods that can increase the accuracy
of the technique, aiding in determining anatomical landmarks. Cadaveric studies clarified
the location of the genicular nerves (origin, termination, course) and their anatomical
relationship with the surrounding tissues.[15 ]
[16 ]
[17 ] Interestingly, this detailed description prompted several studies evaluating GNB
performance using imaging.[10 ]
[12 ]
[18 ] Additionally, it is possible to perform the procedure using anatomical parameters
alone, with no need for auxiliary imaging methods.[14 ]
To date, ultrasound-guided procedures have not proven consistently superior to their
fluoroscopy counterparts,[19 ] which is also more accessible, easier for the orthopedist, and does not require
additional expertise in musculoskeletal ultrasound. As such, the main objective of
this study was to compare the effectiveness of fluoroscopy versus anatomical parameters
(with no radiological resources) as an auxiliary method in GNB for pain relief in
KOA patients.
Materials and methods
The institutional Ethics Committee approved the study under number (58941322.5.0000.5505).
The present study was a quasi-randomized clinical trial and patient selection for
blocks with and without image assistance occurred on a first-come, first-served basis.
We collected demographic data from participants, including age at the time of the
procedure, gender, side of the lesion, and body mass index (BMI).
All data were obtained directly from the patient or the electronic medical record
after the researchers applied the informed consent form.
Selection criteria
Inclusion criteria
The study included patients from 50 to 80-years-old; osteoarthritis with pain for
at least 3 months; having knee radiographs demonstrating Kellgren-Lawrence 3 or 4
osteoarthritis; and/or symptomatic osteoarthritis refractory to clinical treatment
involving oral medications (such as analgesics, nonsteroidal anti-inflammatory drugs
[NSAIDs] etc.), and physical therapy for at least 6 months.
Exclusion criteria
The study excluded patients with: severe neurological or psychiatric diseases; history
of steroid injections within the last 3 months; sciatica; previous knee surgeries,
including knee replacement (total or unicompartmental), debridement arthroscopy, or
osteotomies; and those who make use of anticoagulants. We also excluded patients who
did not receive the scheduled intervention; lost to follow-up before 3 months; and
those with any adverse reaction to the procedure. In this last case, however, despite
being excluded from the final analysis, we documented and reported any adverse reactions
observed during the study.
Genicular nerve block
After using the reference methods according to the predefined group (fluoroscopy or
anatomical parameters), each patient underwent the GNB procedure with a solution containing
8 mL of methylprednisolone (500 mg), 6 mL of 0.5% bupivacaine, 1 mL of clonidine (150 μg),
and a saline solution to a final volume of 20 mL, with 5 mL applied at each point.
Fluoroscopy-guided
Through the anteroposterior view, we identified three reference points: the medial
and lateral transition areas of the femoral cortex, with the respective femoral condyles
and the transition area between the medial tibial condyle and tibial diaphysis ([Fig. 1 ]).[19 ]
Fig. 1 Anteroposterior radiograph demonstrating the reference points at fluoroscopy. Abbreviations: SL, superolateral; SM, superomedial; IM, inferomedial.
Anatomical parameter-based
We drew a longitudinal line from the fibular head towards the femur, extending up
to 4 cm superior to the lateral femoral epicondyle. Then, another line was drawn horizontally
between the femoral epicondyles, and a third one from the medial femoral epicondyle
to the medial tibial epicondyle. These were the reference points. We applied the solution
at the line intersections,[14 ] as shown in [Fig. 2 ].
Fig. 2 (A ) Anterior view with lines drawn through the head of the fibula; (B ) oblique view showing the line drawn 4 cm above the femoral epicondyle.
Outcome measures
We administered the Visual Analog Scale (VAS) for pain and the pain subscale of the
Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) to patients
enrolled in the study before undergoing GNB and at the following time points: 1 hour,
24 hours, 7 days, 28 days, and 90 days after the procedure. The questions were read
to the patients in person or by telephone, if they could not return for follow-up
appointments in person. Both questionnaires were translated into Portuguese and validated
for the Brazilian context.[20 ]
[21 ]
The outcome assessment was single blinded since the professional who performed the
GNB was not the same one evaluating the data. Additionally, the professional in charge
of the assessment was unaware of which group the patients belonged to.
Statistical analysis
After data collection, the analysis used the IBM SPSS Statistics for Windows (IBM
Corp., Armonk, NY, United States) software, version 23.0. Descriptive statistics determined
the clinical and sociodemographic characteristics of patients. The Shapiro-Wilk test
assessed continuous variables. Analysis and comparisons between preoperative and postoperative
clinical-functional scores used the Wilcoxon test (nonparametric; non-normally-distributed
variables) and the paired t test (parametric; normally-distributed variables) per sampling distribution. Comparisons
of self-administered clinical-functional scores in the primary analysis with the secondary
analysis and other continuous variables (age, follow-up, BMI) employed the unpaired
t test (parametric; normally-distributed variables) or the Mann-Whitney U test (nonparametric; non-normally-distributed variables) based on the sampling distribution.
The Chi-squared test evaluated the distribution of categorical variables between the
groups.
Results
Initially, 27 patients met the inclusion criteria and underwent the GNB guided by
radioscopy or clinical parameters. There were 4 patients (14.8%) lost to follow-up
before completing 3 months, which were excluded from the study. Therefore, the final
sample consisted of 23 patients, with a total follow-up of 85.2%, and a mean age of
64.5 ± 4.8 years. There were 16 (69.6%) females and the mean BMI was of 31.4 ± 6.1 Kg/m2 . We divided the eligible patients into two groups: the first group had 12 (52.2%)
patients who underwent fluoroscopy-guided GNB; and the second group had 11 (47.8%)
patients underwent a procedure based on anatomical parameters, that is, with no radiological
aid. There were no statistically significant differences in the distribution of demographic
variables between the groups ([Table 1 ]).
Table 1
Characteristics
Total (N = 23)
Fluoroscopy (N = 12)
Anatomical Parameter (N = 11)
p- value
Age (years): mean ± SD
64.5 ± 4.8
65.3 ± 4.4
63.9 ± 5.2
0.539
Gender: n (%)
Male
7 (30.4)
4 (36.4)
3 (25.0)
0.667
Female
16 (69.6)
7 (63.6)
9 (75.0)
0.444
BMI (Kg/m2 ): mean ± SD
31.4 ± 6.1
29.4 ± 6.2
33.1 ± 5.8
0.189
After analyzing the WOMAC pain subscale questionnaires, we observed a statistically
significant improvement (p < 0.05) at all times after GNB compared with the preprocedure pain level. The most
representative improvement was closer to the procedure. We detected no significant
differences between the outcomes from the two GNB types at any time point studied
([Table 2 ]). In the fluoroscopy group, the preprocedure pain level was 18.2 ± 3.9 of the 20
potential points. In the anatomical parameters group, it was 19.5 ± 1.3. We noted
the highest reduction in pain 1 hour after the procedure, with an improvement of 11.7 ± 3.8
(64.3%, p = 0.003) points in the fluoroscopy group, and in the anatomical parameters group,
of 13.3 ± 1.9 (68.2%, p = 0.002) after 24 hours. During the follow-up, we observed a tendency for increased
pain. After 90 days of the procedure, the reduction in pain in the fluoroscopy group
was 5.1 ± 6.0 (p = 0.024) points (35.7%) and, in the anatomical parameters group, it was 5.3 ± 3.2
(p < 0.001) points (44.6%) ([Fig. 3 ]).
Table 2
Assessment time
Group
Fluoroscopy (N = 12)
Anatomical Parameter (N = 11)
p- value
Pre-GNB (mean ± SD)
18.2 ± 3.9
19.5 ± 1.3
0.478
Post-GNB (mean ± SD)/Improvement (p- value for improvement)
1 hour
6.5 ± 2.1/11.7 ± 3.8 (p = 0.003)
6.9 ± 2.4/12.5 ± 1.9 (p = 0.002)
0.566
24 hours
7.8 ± 3.4/10.4 ± 5.0 (p = 0.003)
6.2 ± 1.8/13.3 ± 1.9 (p = 0.002)
0.347
7 days
8.3 ± 3.4/9.9 ± 5.5 (p = 0.007)
7.3 ± 1.9/12.1 ± 2.2 (p = 0.003)
0.654
28 days
11.7 ± 2.8/6.5 ± 3.8 (p < 0.001)
10.8 ± 3.9/8.6 ± 4.0 (p < 0.001)
0.423
3 months
13.1 ± 3.6/5.1 ± 6.0 (p = 0.024)
14.1 ± 3.2/5.3 ± 3.2 (p < 0.001)
0.401
Fig. 3 Graphical representation of the variation in the mean score on the pain subscale
of the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) at the
different evaluation times. Note: The mean pos-block scores are statistically lower than the mean preblock score for
all evaluation times (p < 0.05). Abbreviation: GNB, genicular nerve block.
The VAS analysis revealed a statistically significant improvement (p < 0.05) at all times after the procedure when compared with the pre-procedure pain
level. The more expressive improvement was closer to the procedure ([Table 3 ]). There was no significant difference between the groups at any time point studied.
The pain reduction after 1 hour of the procedure was more intense, with a score of
6.5 ± 1.4 (78.0%, p = 0.003) of the 10 potential points in the fluoroscopy group and 6.1 ± 2.7 (82.2%,
p = 0.002) in the anatomical parameters group. We noted a trend for increased pain
throughout the postprocedure follow-up. Despite this trend, at the end of the 90-day
follow-up, there was a pain reduction of 3.1 ± 1.6 (36.5%, p = 0.005) points in the fluoroscopy group and 1.8 ± 2.4 (24.6%, p = 0.032) in the anatomical parameters group ([Fig. 4 ]).
Table 3
Assessment time
Group
Fluoroscopy (N = 12)
Anatomical Parameter (N = 11)
p- value
Pre-GNB (mean ± SD)
8.2 ± 0.8
7.3 ± 2.3
0.566
Post-GNB (mean ± SD)/Improvement (p- value for improvement)
1 hour
1.8 ± 1.3/6.5 ± 1.4 (p = 0.003)
1.3 ± 1.8/6.1 ± 2.7 (p = 0.002)
0.235
24 hours
1.7 ± 2.4/6.5 ± 2.5 (p = 0.005)
1.6 ± 1.7/5.8 ± 3.1 (p = 0.003)
0.999
7 days
1.4 ± 1.6/6.9 ± 1.9 (p = 0.003)
2.3 ± 1.5/5.0 ± 2.7 (p = 0.003)
0.134
28 days
3.8 ± 1.3/4.5 ± 0.9 (p = 0.002)
4.2 ± 1.6/3.2 ± 2.7 (p = 0.007)
0.563
3 months
5.2 ± 1.4/3.1 ± 1.6 (p = 0.005)
5.5 ± 1.2/1.8 ± 2.4 (p = 0.032)
0.449
Fig. 4 Graphical representation of the variation in the mean score on the visual analog
scale (VAS) for pain at the different evaluation times. Note: The mean postblock scores are statistically lower when compared to the mean preblock
score for all assessment times (p < 0.05). Abbreviation: GNB, genicular nerve block.
Discussion
Cankurtaran et al.[14 ] compared the efficacy of blockades guided by ultrasound and anatomical parameters,
showing efficacy in pain reduction and function improvement, with similar outcomes
in both techniques. Kim et al.[19 ] compared the efficacy of ultrasound versus fluoroscopy guided blockades, and pain
relief, functional improvement, and safety were consistent between the groups. However,
considering radiation exposure, ultrasound may be superior to fluoroscopic guidance.
The results of this study confirmed the efficacy of GNB in reducing pain in patients
with KOA, regardless of the method used. These findings are consistent with other
studies[14 ]
[19 ] from different countries and ethnic profiles, suggesting the external validity of
the findings. Pain reduction was more significant immediately after the procedure
and gradually decreased over 90 days.
This study also demonstrated the non-superiority of fluoroscopy-guided GNB compared
with anatomic parameter-based GNB with no radiological resources. This is particularly
relevant in centers with relatively limited budgets and infrastructure, showing that
radiological methods are not required for an effective procedure. Another factor to
consider is radiation exposure, which is not present in anatomic parameter-based GNB.
These data were consistent even when different surgeons with distinct experience levels
performed the GNB, which indicates that this technique has a short learning curve
and predictable outcomes.
We observed a trend toward increased pain levels over the 90-day follow-up period,
although maintaining a significant reduction compared with preprocedure levels. These
findings agree with those of the international literature[14 ]
[18 ]
[19 ] and suggest that, at a certain point, a new GNB would be required for symptom control.
Study limitations included not achieving the minimum sample of 56 patients, calculated
in the preproject. Even so, we could achieve statistical significance in all postprocedure
periods. Additionally, we did not perform multivariate analysis for each comorbidity,
their relationships with preprocedure pain, and impacts on the respective outcomes
as independent variables. Due to the scarcity of studies on this topic, future investigations
are necessary to better correlate the outcomes and risk factors.
Conclusion
We observed no statistically significant differences (p < 0.05) between fluoroscopy-guided GNB and anatomic parameter-based GNB regarding
pain relief in patients with KOA.
Therefore, the choice of technique is at the physicians or patients' discretion for
GNB in KOA.
