Keywords ultrasound-guided percutaneous neuromodulation - invasive physical therapy - dynamometer
- femoral nerve - isometric contraction
Introduction
Weakness of the quadriceps muscle after either an injury to the knee or knee surgery
is a common impairment described in the literature.[1 ]
[2 ]
[3 ] This weakness is defined as muscle inhibition of articular origin.[4 ]
[5 ]
[6 ] The early restoration of the muscle contraction properties of the quadriceps is
essential to ensure appropriate recovery and facilitate the return to the activities
of daily living, as well as to work and/or sports activities.[7 ]
[8 ]
[9 ]
Among the various types of muscle contraction, maximal isometric strength (MIS, or
maximal isometric voluntary contraction [MIVC]), is an essential parameter of strength
for the correct functioning of the muscle motor unit.[10 ]
[11 ]
[12 ] Conditioned muscle inhibition can effectively decrease this variable.
Furthermore, a correlation exists between MIS and maximal concentric and eccentric
strength.[13 ]
[14 ] Several studies have found that MIS is vital during the performance of functional
activities, such as jumping, cycling or running.[15 ]
[16 ] Therefore, MIS is an essential variable in neuromuscular assessments.
The electrical stimulation of the peripheral nervous system is a therapeutic strategy
that has been primarily used for the treatment of chronic pain for the past 50 years.[17 ]
[18 ] This stimulation produces a modification of the input to the central nervous system,
known as neuromodulation[19 ]
[20 ]
[21 ]
[22 ]
.
Currently, various neuromodulation procedures have been described in the health sciences,[23 ] such as brain stimulation, spinal cord stimulation, and peripheral stimulation.
Ultrasound-guided percutaneous neuromodulation (US-guided PNM) is a recently developed
invasive physical therapy technique used for neurofunctional improvement and for the
treatment of pain.[23 ] To date, no studies have related this technique with muscle stimulation and dynamometry
changes. Dynamometric tests with devices that enable the calculation of variables
related with isometric movement are another form of functional assessment tools.[24 ]
[25 ]
The aim of the present study was to evaluate changes in isometric strength measured
using dynamometry, after the application of US-guided PNM in the femoral nerve.
Materials and Methods
Design
A quasi-experimental study with a single intervention group, in which the mean maximal
isometric strength (mMIS) was measured, using dynamometry, before and after an intervention
with PNM at the level of the femoral nerve of both quadriceps muscles.
Sample
The study subjects were voluntary participants > 18 years old recruited among patients
of the Fisiocéano clinic (Móstoles, Madrid, Spain). The inclusion criteria were: subjects
with previous pathology in one of their knees but without pain at the time of study,
with variation coefficients[26 ] < 15% and who were in the stage of quadriceps muscle recovery. Subjects with pathologies
that caused pain during the measurements and for whom dynamometry was contraindicated
were excluded (acute muscle injuries, important joint instability, or acute joint
inflammation, among others). For the use of US-guided PNM, the main contraindications
were needle phobia, epilepsy, pacemaker, and pregnancy. All of the subjects signed
the corresponding informed consent form to participate in the study.
Measurements Performed
An expert on dynamometry, external to the physiotherapist who performed the intervention,
performed the measurements and collected the strength data for statistical analysis.
An isometric measurement of the quadriceps muscle was performed using the KINEO (GLOBUS,
Codognè, Italia) dynamometry system. The assessment protocol consisted of a preintervention
measurement of the mMIS (3 seconds contraction and 6 seconds relaxation, for a total
of 3 repetitions) of both quadriceps muscles, and a postintervention measurement of
the mMIS of the quadriceps on the side of the pathological knee. The assessment position
was 90° of hip flexion and 45° of knee flexion, without straps and with manual grips
on lateral supports. The lever arm was placed 2 cm from the malleolus on the ventral
aspect of the ankle, without straps.[10 ]
Physiotherapy Interventions
The US-guided PNM intervention consisted specifically of the application of a biphasic
asymmetric electrical current compensated with a rectangular positive phase and a
negative triangular phase, with a frequency of 10 Hz, a pulse width of 240 μs, and
maximal tolerated intensity. This was in order to provoke a pain-free maximal muscle
contraction, according to the following protocol: 10 stimulations with a duration
of 10 seconds, with a 10-second rest period between each stimulation, as proposed
by Minaya et al.[23 ] The certified device employed for the percutaneous application of the electrical
current was the Physio Invasiva® CE0120 (Prim Fisioterapia y Rehabilitación, Madrid, Spain) using the PES modality,
with 0.30 mm × 40 mm Physio Invasiva® needles (Prim Fisioterapia y Rehabilitación, Madrid, Spain). The femoral nerve was
located over the femoral triangle, using the GE Logic R7 US machine (GE Healthcare,
Chicago, IL, USA) with a 12L linear probe, in a transverse section. The needle was
inserted using an inplane approach, with an angle of 45° to the skin surface, until
reaching the epineurium of the femoral nerve at its lower and lateral aspect ([Fig. 1 ]). The axonal topography described for this nerve[27 ] shows how, at this site, the greater part of the motor axons of the quadriceps muscle
are located ([Fig. 2 ]). Prior to the insertion of the needle, the skin was cleaned using isopropyl alcohol
and chlorhexidine (Lainco® 2% antiseptic for clean skin). The intervention was performed by a physiotherapist
with > 10 years of experience in invasive procedures and US assessments.
Fig. 1 Microscopic image of the transverse section of a peripheral nerve. Note the epineurium,
the perineurium and the endoneurium (Reproduced with permission from MVClinic Institute).
Fig. 2 Image of the therapeutic US-guided PNM procedure of the femoral nerve and explanatory
image of the axonal topographic distribution of the nerve (Reproduced with permission
of MVClinic Institute). Abbreviations: AC, acetabulum; FA, femoral arteri; HoF, head
of femur; Lat, lateral; Med, medial; MP, pectineus muscle; MRAC, rectus femoris anterior
muscle; MS, sartorius muscle; MVI, vastus intermedius muscle; MVL, vastus lateralis
muscle; MVM, vastus medialis muscle; NCA, anterior cutaneous femoral nerve; NCM, medial
cutaneous femoral nerve; FN, femoral nerve; NS, saphenous nerve; P, psoas; Deep, deep;
S, sartorius; Sup, superficial; FV, femoral vein.
Statistical Analysis
A descriptive analysis was performed by calculating the mean, the median and the mode
of the characteristics of the dependent and independent variables. Inferential statistics
were performed via the comparison of the means using the Student-t test (α= 0.05)
for related samples, after considering the normality of the sample and the distribution
of the kinetic samples assessed by dynamometry or via biomechanical systems. All of
the analyses were performed using the Microsoft Excel 2013 software (Microsoft Corporation,
Redmond, WA, USA).
Results
In total, 13 voluntary subjects participated in the present study, with a mean age
of 39.92 years old (standard deviation [SD]: 9.09), of which 2 were female and 11
were male. [Table 1 ] presents the sociodemographic and clinical characteristics of the sample.
Table 1
Subject
Gender
Age
Height (cm)
Weight (Kg)
Pathological side
Type of lesion
01
F
44
166
52
L
Condropathy
02
F
28
162
64
L
Rupture anterior cruciate ligament
03
M
38
188
78
R
Meniscopathy
04
M
39
182
89
R
Meniscopathy
05
M
41
175
71
R
Condropathy
06
M
59
169
90
L
Meniscopathy
07
M
27
183
77
L
Condropathy
08
M
38
167
92
L
Arthroscopy of the meniscus
09
M
51
178
87
L
Meniscopathy
10
M
49
178
84
R
Surgery of meniscus and anterior cruciate ligament
11
M
36
173
84
L
Meniscopathy
12
M
32
174
70
R
Arthroscopy of the meniscus
13
M
37
185
83
R
Arthroscopy of the meniscus
After the application of US-guided PNM on the femoral nerve, changes were obtained
for the mMIS of the quadriceps muscles that had undergone previous pathology. Prior
to the intervention, the mean strength was 25.91 kg (SD: 7.17 kg) compared to a mean
of 29.98 kg after the intervention (SD: 9.06 kg). The results obtained were statistically
significant with a p -value of 0.0019.
It is also important to note that the mMIS of the quadriceps on the healthy contralateral
side was 27.59 kg (SD: 7.86 kg), compared to 25.91 kg (SD: 7.17 kg) on the injured
side. This finding was statistically significant (p = 0.026) ([Fig. 3 ]). This data reveals a decrease of the maximal isometric strength on the affected
side prior to the intervention. These values, as can be observed in [Fig. 4 ], after the intervention, are equal or, in many cases, greater than the contralateral
measure of the initial reference.
Fig. 3 Summary of dynamometry data. The graph displays the data of the mean maximum isometric
strength of the quadriceps in the pathological knee. Preintervention and postintervention;
and the preintervention measurements of the healthy contralateral quadriceps along
with the standard deviation.
Fig. 4 In blue, the mean maximal isometric strength of the quadriceps of the knee with preintervention
pathology; in orange, the contralateral side preintervention; and, in gray, the mean
maximal isometric strength of the quadriceps with postintervention pathology. Note
the increase of > 15% in the mean of the pre- and postintervention measurements of
the quadriceps of the knee with previous pathology. It is also observed how, after
the intervention, the mean maximal isometric strength of the quadriceps of the pathological
knee, in many cases, was beyond the initial measurements of the mean maximal isometric
strength of the contralateral healthy knee.
Discussion
To the best of our knowledge, no study has measured the mMIS of the quadriceps muscle
using dynamometry after the application of US-guided PNM in the femoral nerve.
The preintervention measures gathered in the present study reveal that the mean mMIS
of the pathological side was 25.91 kg, whereas the mean mMIS of the contralateral
side was 27.59 kg. Therefore, there is evidence of weakness of the quadriceps muscle
on the leg with a previous injury when compared with the contralateral leg. Nonetheless,
according to a systematic review performed by Hart et al, bilateral deficiencies in
quadriceps activation are common.[28 ] This may explain why subjects 6, 8 and 11 presented values in which the mMIS was
greater in the leg with previous pathology when compared with the contralateral side.
After the intervention, there was a statistically significant improvement of the mMIS
of the quadriceps on the affected side, which increased from a mean of 25.91 kg, prior
to the intervention, to 29.98 kg postintervention. This indicates that the PNM was
effective for increasing, or hypothetically recovering, the strength of the quadriceps
muscles that were inhibited secondary to problems of the joint. The hypothesis regarding
this neuromuscular inhibition is a decrease in the corticospinal excitability and/or
changes in the spinal reflex.[29 ]
A systematic review by Sonnery-Cottet et al found moderate evidence for the effectiveness
of cryotherapy and physical exercise in the management of muscle inhibition of an
articular origin.[30 ] In contrast, Pietrosimone et al suggested that therapeutic interventions directed
at eliciting changes in the voluntary activation of the quadriceps may improve the
effectiveness of therapeutic exercise in strength improvements.[31 ] For this reason, US-guided PNM may be a suitable therapeutic procedure for use prior
to exercise programs.
Furthermore, US-guided PNM is a technique that may be employed in patients immediately
after either an injury or a surgical intervention, representing a physiotherapy tool
that may help prevent the appearance of muscle atrophy and the establishment of neuromuscular
inhibition, thus avoiding the negative consequences that may delay or hamper the return
to activity of a patient.[29 ]
[32 ]
This new treatment concept may open new lines of research and provide both the physiotherapist
and the patient with improved results regarding strength gains in these types of articular
disorders.
The results of the present study reflect preliminary conclusions due to the limitation
of the sample size. Future research should confirm these findings and analyze whether
similar strength improvements occur in other muscle groups after neural stimulation.
Additionally, it is necessary to perform both mid- and long-term assessments of strength
using a dynamometer to evaluate how long these improvements are maintained over time.
Conclusions
Ultrasound-guided PNM has been found to be an effective technique for the reestablishment
of isometric strength of the quadriceps in inhibited muscles.
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