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Pathos 2016; 23; 3. Online 2017, Jan 26
Pulsed radiofrequency in patients with chronic shoulder pain
Radiofrequenza pulsata in pazienti con dolore cronico della spalla
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Antonino Genovese,1 LuigiCardia,2 Epifanio Mondello,2 Antonino Fugazzotto,3
Salvatore Bartolone,4 Maria De Florio,1 Carmelo Costa,5
1 Anaesthesia, Intensive CU and Pain Therapy, ASP Messina, Patti, Italy
2 Anaesthesia, Intensive CU and Pain Therapy Unit, Messina University, Italy
3 Department of Orthopaedic Surgery, Hospital Cantonal Fribourgeois, Riaz, Switzerland
4 Radiology, ASP Messina, Milazzo, Italy
5 Pain Therapy - Humanitas Cancer Center, Catania, Italy
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Summary The purpose of this study is to evaluate the efficacy and safety of suprascapular nerve pulsed radiofrequency, in patients affected by chronic shoulder pain. In the study were included sixteen (16) patients affected by chronic shoulder pain for a period of more than six months. Of which: 3 suffering from frozen shoulder, 5 for lesions (injury) of the rotator cuff, and 8 for osteoarthritis.
After a favorable response to a diagnostic suprascapular nerve block (pain relief > 50% NRS), PRF neuromodulation was performed. Shoulder pain and quality of life were assessed using a Numeral Rating Scale (NRS), before the diagnostic block and every month after PRF neuromodulation for a 6-month period. The mean NRS score in all (16) patients before PRF was 6.75±1.05, and the scores at 6-month follow-up were 1.30±0.50. A significant pain reduction (p<0.001) was observed. Pulsed radiofrequency of the suprascapular nerve is an effective treatment in patients affected by chronic shoulder pain, providing a relatively long period of pain relief.
Key words Pulsed radiofrequency, chronic shoulder pain, pain
Riassunto  Lo scopo di questo studio è di valutare l'efficacia e la sicurezza della radiofrequenza pulsata in pazienti affetti da dolore cronico alla spalla. Nello studio sono stati inclusi sedici (16) pazienti affetti da dolore cronico alla spalla per un periodo superiore a sei mesi. Di questi pazienti, tre erano affetti da spalla congelata, cinque da lesioni della cuffia dei rotatori, otto da artrosi. Dopo una risposta diagnostica favorevole di un blocco del nervo sovrascapolare (sollievo dal dolore> 50% NRS), è stata eseguita la neuromodulazione con radiofrequenza pulsata. Il dolore alla spalla e la qualità della vita dei pazienti sono stati valutati utilizzando la scala verbale numerica (NRS), prima e dopo il blocco ssovrascapolare e una volta al mese dopo la neuromodulazione con radiofrequenza pulsata, per un periodo di 6 mesi. Il punteggio medio NRS in tutti i pazienti prima della procedura era di 6,75 ± 1,05, e i risultati del follow up dei successivi sei mesi sono stati mediamente 1,30 ± 0,50. È stata osservata una significativa riduzione del dolore (p <0.001). La radiofrequenza pulsata del nervo soprascapolare è un trattamento efficace in pazienti affetti da dolore cronico della spalla, fornendo un periodo relativamente lungo di sollievo dal dolore.
Parole chiave Radiofrequenza pulsata, dolore cronico della spalla, dolore

Introduction
Chronic shoulder pain is a debilitating and disabling phenomenon. It is very frequent among population.1 The most common conditions affecting the shoulder are the rotator cuff tear, adhesive capsulitis and osteoarthritis.2 A treatment for this painful syndrome may be represented by nerve block suprascapular. But, if this procedure with the infiltration of local anesthetic ensures a reduction in pain for a short time, other techniques can be used for long term pain relief.3-5 Many clinical studies showed that pulsed radiofrequency of the suprascapular nerve can provide pain relief and ensure better quality of life to the patients.6-10 In this study we included 16 patients with chronic shoulder pain and assessed the reduction in pain for the first six months after treatment.

Materials and methods
From April 2016 to December 2016, were selected and included in the study, 16 patients suffering from chronic shoulder pain from at least 6 months, that does not obtain sensible improvement in pain relief with medical therapy and intra-articular blocks and that can't undergo surgery. The clinical diagnosis was performed by ultrasonography or magnetic resonance imaging. All patients were treated with drug therapy, physiokinesitherapy and intra-articular blocks with corticosteroids and local anesthetics, but without obtaining sensible variations on pain relief. They were excluded from the study patients who were suffering from diabetes and neurodegenerative disorders. All patients received a diagnostic block of the suprascapular nerve with ropivacaine 0.3% 2 ml and dexamethasone 4 mg. Temporary pain relief (> 50% NRS)  or improvement of muscle movements, valued with the Brief Pain Inventory (short form) questionnaire, was considered positive for treatment with pulsed radiofrequency. The PRF was performed in the operating room under fluoroscopy, using a radiofrequency generator (Top Lesion Generator TLG-10). The C-arm was angled about 10-20° in cephalo-caudal and oblique scans. The suprascapular notch was identified, as show in Figure 1. It is superior to the scapular spine and medial to the coracoid process. We have drawn a line along the spinous processes of the spine, then we identified the spine of the scapula and traced another line from the acromion to the medial border of the scapula. Finally, we provided at the center of this a line, parallel to that traced along the spine. The angle of the upper outer quadrant was bisected with a line, and an "X" was marked on the line, 1 cm from the apex of this angle. (Figure 1 mentioned and Figure 2).
After the disinfection of the puncture site and after preparing a sterile field, we introduced the needle in the marked point, reaching our target under fluoroscopy. Sensory stimulation at 50 Hz was performed, and reproducible paresthesias in the shoulder joint occurred at a voltage ≤0.3 V. (Figures 3, Figure 4)
Motor stimulation at 2 Hz was performed and contractions of the infraspinatus and supraspinatus muscles occurred at 0.4 V. After positive stimulation we performed treatment with pulsed radiofrequency at 42 degrees for 300 seconds. The subjective pain intensity was measured with numeral rating scale (NRS) before performing the procedure, and after 1,3,6 months.
The average of the NRS values before the procedure were compared with those obtained at the last follow-up (six months) after the execution of the PRF. P values <0.05 were considered statistically significant. The U-Mann test was used for the statistical analysis.

Results
16 patients were included in the study (6 females and 10 males), aged between 47 and 81 years. In all cases, the patients first got the diagnosis by ultrasound or magnetic resonance imaging. The patient's characteristics are summarized in Table 1.
Three patients suffered from frozen shoulder, five patients from rotator cuff lesions, and seven from osteoarthritis. All 16 patients suffering from chronic shoulder pain for more than six months.
The follow up was conducted up to six months after treatment. The NRS values are represented in Table 2, and the statistical analysis in Table 3.
The statistical analysis and clinical evaluation shows that patients achieved a significant relief from pain, up to six months (p> 0.001). The average of NRS values before the diagnostic and the radio-frequency block treatment was 6.75±1.05, and the values at 6th month of follow-up were 1.30±0.50.
 
Discussion
There are many doubts about the mechanism of action of radiofrequency currents, both the continuous radiofrequency (CRF) and, especially, the pulsed radiofrequency (PRF). About the pulsed radiofrequency (PRF) is whether to act mainly, or exclusively, on the unmyelinated C fibers (this would explain their ability to provide pain relief without interfering with the motility and the sensitivity) or on myelinated A Delta and A Beta (this would explain the ability of the PRF in controlling peripheral neuropathic pain in which the fibers are often involved A beta). In literature, there are conflicting opinions. The study of Protasoni et al.11 shows in the dorsal root ganglia of rats after 1 hour by exposure to PRF, examined with an electron microscope, a damage to the myelin sheath of nerve fibers. However, the study of Erdine et al.12 shows the afferent axons of sciatic nerves of rats subjected to PRF, examined after 10 days with electron microscope, a more pronounced damage to the unmyelinated C fibers rather than the myelinated A and A Delta Beta. From the analysis of these two studies would seem that the PRF could act on different nerve structures at different times: the myelinated fibers in the early stage and on unmyelinated in a later stage. The suprascapular nerve (NSS) is a mixed nerve, sensory and motor. It originates as a side branch of the brachial plexus in the spinal cord of the cervical spine. In addition to the electrical pulses delivered to the aforesaid rotator cuff muscles, to harness the movement of the shoulder, the NSS is also responsible for the perception of sensitivity of approximately 65-70 percent of the shoulder joint. In the international scientific literature, there are many studies on the use of pulsed radiofrequency neuromodulation for the relief from pain, but only a few studies regarding the pulsed radiofrequency applied to chronic shoulder pain. Gurbet et al.13 examined eight patients with chronic shoulder pain, and observed a pain relief lasting for 3 months. In a recent study, published in 2013, Ji Su Jang et al.14 examined 11 patients with painful shoulder disease, they report  that the treatment with PRF has given a good compliance of pain up to 9 months. We have observed that in 16 patients, suffering from various chronic diseases causing shoulder pain, treatment with PRF has had a noticeable effect. Indeed, we have obtained a reduction in the NRS values > 50%, in all patients, treated for a period of 6 months. The PRF of the suprascapular nerve is a safe method and easy to perform, with minimal risks to the patient, which can guarantee a global pain reduction and an improvement in the joint mobility and in the patient's quality of life.
 
Conclusion
The PRF of the suprascapular nerve is a safe technique and easy to perform and allows a good reduction of pain in patients suffering from chronic shoulder pain.

References

Acknowledgements
The authors are grateful and mention the beloved Prof. Tommaso Mandolfino, MD, for his undisputed cultural and human depth, for the precious teachings and the passion that every day transmitted to his students and for being a pioneer in the field of pain therapy.
Photos
Courtesy of Carmelo Costa
Published
26th, January 2017
Corresponding author:
Antonino Genovese, Anesthesia and Intensive Care Unit, ASP Messina, Patti, Italy,
email: vesegeno@gmail.com
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