Accuracy of Rib Palpation for Dry Needling of Deep Periscapular Musculature, Measured With Ultrasound
Conditions: Trigger Point Pain, Myofascial
Sponsor: University of Utah

Study:  Proper identification of ribs underlying the rhomboid major and trapezius muscles 
using palpation.  
 
Dated 8/19/19, originally created 6/18/2015 
 
NCT number: 0084226 
 
Principle Investigator:  
Dan Cushman, MD  
 
Co-Investigators: 
 
A. Michael Henrie, DO 
 
 
 
 
Alexandra Flis, MD 
 
Project summary: This study will determine the accuracy of medical practitioners in locating 
the posterior ribs underlying the rhomboid major and trapezius muscles in individuals of 
different Body mass indices.  
 
 
 

Project description: 
Rationale:  
Cervical pain with associated myofascial trigger points is a common musculoskeletal issue with 
prevalence ranging from 30-85% (Gerwin 1995, Skootsky 1989). Treatment options for 
myofascial trigger points include both non-invasive and invasive treatments. Non-invasive 
treatments include deep pressure, massage, heat, TENS, and spray and stretch (de las penas 
2005, Hou 2002). More aggressive, invasive treatment options include dry needling, anesthetic 
injection, or Botulinum toxin A injections (Liu 2015, Cummings 2001, Ho 2006, Scott 2009). 
Complications associated with dry needling are rare but include infection, bleeding, pain, 
epidural hematoma, and pneumothorax (Conway 2013, Cummings 2014, Ding 2013, He 2012, 
Juss 2008, Lee 2011, Karavis 2015, McCutcheon 2011).  
 
Pneumothorax, which is a collapse of the lung, can result from trigger point injections to the 
muscles in close proximity to the ribs such as rhomboid major, rhomboid minor, trapezius, 
diaphragm, shoulder muscles, and neck muscles, where the needle is penetrated too deep and 
passes the pleura. Though the reported incidence of pneumothorax has been reported to be 
around 1 in 100,000 (Witt 2009, Melchart 2004), there is some thought that pneumothoraces 
may be underreported for two reasons - patients may have a subclinical pneumothorax or fail 
to report to their practitioner about shortness of breath or dry cough.  
 
The rhomboid major muscle originates on the spinous processes of the T2-T5 vertebra and 
inserts on the medial border of the scapula. There has been a study to address the appropriate 
depth for needle insertion when dry needling or injecting the rhomboid major (Seol 2014). To 
our knowledge, there have been no studies to investigate a practitioner’s ability to properly 
identify rib location with palpation.  In fact, a recent case report outlines a pneumothorax 
caused by an extremely experienced practioner inserting a needle into the rhomboid 
(Cummings 2014). Use of an electromyography (EMG) needle for trigger point injection has also 
been described to help limit the danger of pneumothorax (Botwin 2007).  Additionally, 
ultrasound has been used as a modality to identify safe needling of the diaphragm (Amirjani 
2012).  
 
Electromyographers frequently need to insert a needle into the same muscles. The rhomboid 
major, which is innervated by the dorsal scapular nerve, is one of just a few muscles that is 
innervated almost exclusively by the C5 nerve root, which can help differentiate levels of a 
nerve root lesion.  For the same reasons as dry needling, improper needle placement of an EMG 
needle can cause a pneumothorax. 
 

When performing dry needling or EMG of the rhomboid major muscle, proper identification of 
the ribs provides an anatomic landmark to prevent needle insertion into the pleural space (Seol 
2014, Travell/Simons).  The technique is often called “blocking,” where the practitioner places 
the index finger in the intercostal space above or below a rib, with the middle finger on the 
intercostal space on the other side of the rib.  This theoretically means that if a needle is 
inserted too deeply, it will only hit the rib and not go into the intercostal space.  However, to 
our knowledge, this has never been investigated.  Anecdotally, this is difficult to perform on 
someone with a large body habitus. 
 
Objective: 
1. Identify the accuracy of palpation guided identification of the ribs underlying the 
rhomboid major muscles. 
2.  
 
Subjects to study: 
Inclusion criteria:  
Adults >18 years old 
Main exclusion criteria: 
Prior surgery or scarring to the posterior aspect of the shoulder, which will make 
accurate localization of the rib using ultrasound difficult. 
 
Methodology: 
Subjects will be identified using inclusion criteria and consented.  No personally identifiable 
patient information will be collected.  The subject’s age, height, weight, and gender will be 
recorded. The patient will be positioned in the prone or seated position, as per the 
practitioner’s usual custom.  The practitioner will then palpate to identify a posterior rib 
location under the rhomboid major. They will then place a single dot over what they 
perceive as the midline of the rib using a felt tip, skin-marking pen. 
 
A second practitioner, trained in ultrasound identification, will then use a linear probe on an 
ultrasound machine to obtain a clear view of the ribs in a perpendicular alignment over the 
placed skin marking.  The linear probe has a line signifying the middle of the probe, which 
will be placed directly over the center of the skin marking.  This will be done with the rib in 
short axis to the ultrasound probe.  Images will be saved for review, and will be analyzed for 
skin-to-rib depth as well as the rib location (e.g. middle 50%, outer 25% of the rib). 
 
Data management and analysis: 

Data will be collected in an Excel spreadsheet file.  As there will be no personally-
identifiable information contained, it will not be password-protected.  Our primary outcome 
will be a simple percentage of accurate vs. inaccurate rib identifications.  Secondarily, data 
will be examined for normality by Kolmogorov-Smirnov testing.  Logistic regression testing 
will be used to examine a relationship between BMI & accuracy and between depth & 
accuracy. 
 
Sample size needed for the study: 
As no data has been published on this study, we are using clinical opinion.  Anecdotally, we 
feel that on patients with a normal BMI, the inaccuracy rate will be almost zero.  However, 
in obese subjects, this value is probably much larger.  We would estimate that 10% of 
overweight individuals would have inaccurate readings.  For a p value of 0.05, this would 
require 46 overweight subjects.  If we make the assumption that half of subjects are 
overweight, we should recruit 92 total subjects. 
 
Ethical considerations: 
Recruitment plans: Participants will be recruited for participation from patients in our 
musculoskeletal clinics at the University of Utah. 
 
Compensation: None 
Risks of the study: There is minimal risk associated with participation in the study. There 
is a very low risk of a local reaction to the skin-marking ink or ultrasound gel. 
 
Benefits of the study: There is no benefit to the participants in this study. 
 
Informed consent: Informed consent will be obtained  
 
IRB approval: *** 
 
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