Rhomboid Major Muscle Ultrasound-Guided Trigger Point Injection : A Case Report and Technique Description

Introduction: Myofascial pain syndrome is an acute and chronic painful musculoskeletal condition that involves muscle and surrounding connective tissue. Trigger point injection is a common treatment for this condition providing long-term relief. The procedure is generally safe; however some side effects have been reported including pain, nerve injury, bleeding, infection, and pneumothorax. Objective: To report a case of a patient with myofascial pain syndrome successfully treated by Ultra Sound-guided infiltration of a myofascial trigger point in the rhomboid major muscle. Case description: A 39-year-old presented with cervical and dorsal pain of 4 months of evolution. She had physical and occupational therapy, with partial improvement of cervical pain but persistence of dorsal pain. No abnormal finding was noted on the neurological examination. On palpation, the patient had a myofascial trigger point in the left rhomboid major muscle. Given the persistence of the myofascial trigger point after physical therapy, it was considered the patient might benefit from Ultra Sound-guided infiltration. No adverse events were reported. At the end of the procedure, the patient reported a 70% reduction in pain. The patient returned for a follow-up visit one month after the procedure, reporting pain relief of 80%. Conclusions: The use of an Ultra Sound-guided technique for trigger point injection decreases the risk of iatrogenic complications. The blind method may result in poor localization of the point. Further studies are required to develop Ultra Sound based criteria to determine its clinical use. Słowa kluczowe mięśniowo-powięziow y zespół bólowy, kontrola USG, mięśniowo-powięziowe punkty spustowe, iniekcja punktu spustowego Abstrakt Wstęp: Mięśniowo-powięziowy zespół bólowy jest ostrym, przewlekłym i bolesnym stanem układu mięśniowo-szkieletowego, który obejmuje mięśnie oraz otacząjącą je tkankę łączną. Zastrzyk do punktu spustowego jest powszechnym sposobem leczenia tego schorzenia, dającym długotrwałą ulgę. Procedura jest generalnie bezpieczna; jednakże zgłaszano pewne objawy niepożądane takie jak ból, uszkodzenie nerwu, krwawienie, infekcję, oraz odmę opłucnową. Cel: Opis przypadku pacjentki z mięśniowo-powięziowym zespołem bólowym leczonej skutecznie za pomocą infiltracji pod kontrolą USG mięśniowo-powięziowego punktu spustowego w mięśniu równoległobocznym większym. Opis przypadku: 39-letnia pacjentka, z występującym od 4 miesięcy bólem szyjnym i grzbietowym. Po fizjoterapii oraz terapii zajęciowej, ból szyi częściowo złagodniał ale ból grzbietu utrzymywał się. W badaniu neurologicznym nie stwierdzono żadnych nieprawidłowości. Podczas badania palpacyjnego, w lewym mięśniu równoległobocznym większym pacjentki wykryto mięśniowo-powięziowy punkt spustowy . Biorąc pod uwagę utrzymywanie się mięśniowo-powięziowego punktu spustowego po fizjoterapii, uznano, że pacjentce mogłaby pomóc infiltracja po kontrolą ultrasonografii. Nie zgłoszono żadnych niepożą-

Introduction: Introduction: Myofascial pain syndrome is an acute and chronic painful musculoskeletal condition that involves muscle and surrounding connective tissue. Trigger point injection is a common treatment for this condition providing long-term relief. The procedure is generally safe; however some side effects have been reported including pain, nerve injury, bleeding, infection, and pneumothorax. Objective: Objective: To report a case of a patient with myofascial pain syndrome successfully treated by Ultra Sound-guided infiltration of a myofascial trigger point in the rhomboid major muscle. Case description: Case description: A 39-year-old presented with cervical and dorsal pain of 4 months of evolution. She had physical and occupational therapy, with partial improvement of cervical pain but persistence of dorsal pain. No abnormal finding was noted on the neurological examination. On palpation, the patient had a myofascial trigger point in the left rhomboid major muscle. Given the persistence of the myofascial trigger point after physical therapy, it was considered the patient might benefit from Ultra Sound-guided infiltration. No adverse events were reported. At the end of the procedure, the patient reported a 70% reduction in pain. The patient returned for a follow-up visit one month after the procedure, reporting pain relief of 80%. Conclusions: Conclusions: The use of an Ultra Sound-guided technique for trigger point injection decreases the risk of iatrogenic complications. The blind method may result in poor localization of the point. Further studies are required to develop Ultra Sound based criteria to determine its clinical use.

INTRODUCTION
Myofascial pain syndrome (MPS) is an acute and/or chronic painful musculoskeletal condition that involves muscle and surrounding connective tissue. It is characterized by a myofascial trigger point (MTrP) with firm, discrete, palpable nodules in the taut band of muscle that may be sponta-neously painful or painful with pressure 1 . MPS is a frequent cause of outpatient visits in Physical Medicine and Rehabilitation practice. Trigger point injection is a common treatment for MPS, providing temporary or long-term relief. The procedure is generally safe; however, some side effect s have been reported, including: pain, nerve injury, bleed-ing, infection, and pneumothorax 2,3 . Using ultrasound guidance benefits patients due to improve localization of the injection site by visualization of the MTrP, with subsequent reduction of side effects 2 .
The MTrp located in the rhomboid major muscle (RMM) is a frequent cause of dorsalgia. It is originated from the spinous processes of the T2 through T5 vertebrae and inserts into the inferomedial part of the scapula. It is a thin muscle situated between the middle trapezius and the pleura and major neurovascular structures 4 . The muscle has a quadrilateral shape, and its action is to displace the scapula medially, holding it close to the chest wall and rotating the scapula down.
We report a case of a patient with MPS who was successfully treated by ultrasound-guided (US-guided) infiltration of MTrp in the RMM.

CASE DESCRIPTION
A 39-year-old woman with unremarkable medical history presented with cervical and dorsal pain of 4 months evolution. She had physical and occupational therapy with partial improvement of cervical pain but persistence of dorsal pain. The maximum pain site was located in the left interscapular region. No abnormal finding was noted on the neurological examination, including the evaluation of deep tendon reflexes, strength muscle testing, and sensory examination. On palpation the patient had MTrP in the right RMM. Given the persistence of the MTrP after physical therapy, it was considered the patient may benefit from US-guided infiltration. The patient was informed of the risk and benefits of the procedure, and an informed consent form was signed.
The patient was seated in a neutral position, her affected side hand was  month after the procedure, reporting NRS of 2/10, a pain relief scale (PRS) score of 80% (NRS has fallen from 10/10 before procedure to 2/10 at 1 month follow-up), with minimal pain to palpation.

DISCUSSION
MTrP of RMM is a frequent cause of dorsalgia and trigger point injection is the treatment of choice. Palpation of a thoracic rib is suggested to reduce the risk of pneumothorax during puncture of this muscle. Cushman et al showed the safety of needle electromyography (EMG) examination of the RMM. Two Physical Medicine & Rehabilitation (PM&R) staff, with 4 and 7 years of experience performing EMG, palpated 44 healthy subjects to attempt to identify the center of a rib located beneath the RMM. The identified location was examined with US to determine its accuracy and anatomical depths, demonstrating only a 66.3% accuracy rate of palpation compared to US, with significantly more incorrect palpations seen with larger muscle thickness and body mass index 5 . Major complications, including pneumothorax and neuropathy, have been described in literature: Patel et al presented a case of a 44-year-old man who had dry needling of the infraspinatus, supraspinatus, rhomboid major, and paraspinal muscles with subsequent development of a left apical pneumothorax 6 . Also, Lee and Chang reported the case of a 38-yearold male patient who presented with right dorsal scapular neuropathy after a trigger point injection into the RMM, confirmed by nerve conduction study and EMG 7 .
As for the depth of the needle, Seol et al examined the appropriate depth for needle insertion into the RMM and determined that the distance from skin to rib was dependent upon the BMI, yet the muscle thickness was not. For patients with a BMI <23 kg/m 2 , as with our patient (BMI 22 kg/m 2 ), the depth of the needle was 1.4 to 1.7 cm (8).
Dinesh Kumbhare et al, in a literature review about ultrasound-guided positioned on the opposite shoulder to relax the RMM (Figure 1). The point of greatest pain was palpated and marked with a band. The pain was rated as 10/10 according to the Numerical Rating Scale (NRS). A 16-MHz linear probe (Aplio™ i800 ultrasound system; Canon Medical Systems, USA) in transversal plane was placed 1 cm medial from the medial border of left scapula identifying the trigger point as a hypoechogenic area within the muscle and coinciding with the marked point identified by palpation ( Figure 2). Skin asepsis was conducted with soap, 4% chlorhex-idine and sterile gauze. A 26-gauge needle was inserted into the RMM, at a 45° angle and noting that it was inside the trigger point and directed on a rib. Given that a thin gauge of the needle was used, only the tip was seen on US ( Figure 3). The needle penetrated a distance of 10.25 mm from the skin. 1 ml Xylocaine® and 1 ml Betaduo® was injected following aspiration, and absence of vessel damage was confirmed with color Doppler (Figure 4). At the end of the procedure, the patient rated the pain with a NRS of 3/10. The patient returned for a follow-up visit one From the anatomical point of view, the puncture of the RMM is difficult with the blind technique, because it is under the trapezius muscle and with multiple overlapping muscles. A double-blind study was conducted that included 65 patients with a diagnosis of MPS who were randomized into 2 groups. In group 1 (33 patients), US-guided RMM injection was performed and in group 2 (32 patients), US-guided trapezius muscle injection was performed. This study concluded that US-guided deep injection of the RMM was more effective than superficial injection of the trapezius muscle for pain, disability reduction, and increased quality of life 4 .

CONCLUSIONS
We presented the case of a patient successfully treated with US-guided RMM infiltration and described the technique used. The use of an US-guided technique for RMM trigger point injection could decrease the risk of iatrogenic complications compared to the blind method, with additional potential benefits to patients improving localization and appropriate injection into the MTrP.