Introduction
One frequent muscular impairment observed in individuals with chronic
pain is myofascial pain syndrome (MPS), characterized by the presence of
myofascial trigger points (MTrPs). A MTrP is defined as a hyperirritable
spot in a taut band of a skeletal muscle which is painful on stimulation
(e.g., palpation, stretch, contraction, or needling), elicits referred
pain, and induces motor or autonomic disturbances1.
Active MTrPs are those which pain referral reproduces the symptoms of
the patient, whereas latent MTrPs are those which referred pain does not
reproduce the symptoms of the patient1.
Myofascial trigger points have been found to be highly prevalent in
spinal pain disorders2. Simons et
al.1 suggest that one relevant muscle for the
development of thoracic spine pain is the rhomboid muscle. In fact,
patients with cervical radiculopathy show a prevalence of 10.2% of
active MTrPs in the rhomboid musculature3. In
addition, up to 75% of patients with thoracic pain also exhibit active
MTrPs in the rhomboid4.
The rhomboid major is a quadrangular muscle located in the thoracic
spine innervated by the dorsal scapular nerve which contributes to the
positioning and motion of the scapula. The rhomboid major muscle
originates from the supraspinous ligament and the spinous processes of
T2-T5 vertebrae and inserts into the line between the scapular spine
root and the inferior angle on the medial margin of the scapular
spine5. It lies superficial to the posterosuperior
serratus (immediately superficial to the ribs) and deeper to the middle
trapezius muscle.
Manual therapy and dry needling are the most common therapeutic
interventions applied for the management of MTrPs. Dry needling consists
of the insertion of a solid filament needle into the muscle targeting a
potential MTrP and has received increasing attention in the literature
in the last years6. Since dry needling is an invasive
technique, improving its safety is crucial7.
Despite the fact that dry needling is declared as a safe intervention
safety, several adverse events have been described in the literature. It
has been reported that the most common adverse events associated to dry
needling can be considered minor and include bruising, bleeding, pain
during treatment and pain after treatment8,9.
Nevertheless, serious adverse events cannot be excluded, Brady et
al.8 gave an estimated risk rate of ≤ 0.04% for
significant adverse events. Pneumothorax is one of the most serious
adverse events occurring when dry needling the thorax or rib cage and
resulting from an improper needle insertion into the pleural space
during the technique. In fact, several case reports describing
iatrogenic pneumothorax after the application of dry needling into
posterior thoracic muscles are described10.
Due to the anatomical location of the rhomboid musculature, a correct
safety and prevention is needed due to the severity of this
complication. In fact, different strategies have been proposed to ensure
patient’s safety and decrease relative risk during invasive procedures.
Cushman et al have suggested palpation of the ribs before dry needling
could prevent pneumothorax; however, these authors reported poor
accuracy in subjects with larger muscle thickness and higher body mass
index11. As conclusion of their study, they
recommended the use of ultrasound evaluation during or before dry
needling to ensure the correct needle length. Folli et al. recently
reported, as assessed with ultrasound imaging, a mean thickness of the
major rhomboid muscle of 16.3mm (males muscle thickness: 25.4mm; women
muscle thickness: 20.4mm)12. However, the routinely
use of ultrasound in clinical practice is not always possible due to its
high economic costs.
Seol et al.13 provided tentative needle lengths and
safe margins based on the Body Mass Index of subjects based on a 3-group
classification (BMI>25; 23<BMI<25; and
BMI<23). A similar procedure including more potential
predictors (e.g. age, thorax circumference, respiratory moment, gender)
could help clinicians to determine the depth of the pleura and rhomboid
major muscle, and, hence, determining the appropriate length of the
needle. Therefore, the aim of this study was to evaluate if
anthropometric features can predict rhomboid major muscle and pleura
depth, as assessed with ultrasound imaging, in a sample of healthy
subjects. Our hypothesis is that a prediction model based on age,
height, weight, respiratory moment, thorax circumference, BMI and gender
could assist during the application of dry needling into the rhomboid
musculature.