Effects of microcurrent and cryotherapy on C-reactive protein levels and muscle tone of patients with rotator cuff reconstruction (2025)

Abstract

[Purpose] The purpose of the present study was to apply early intervention viamicrocurrent and cryotherapy in patients who underwent rotator cuff reconstructionsurgery, and to investigate the effects of such interventions on pain and inflammationlevels based on the analysis of C-reactive protein (CRP) levels, and on changes in muscletone. [Subjects and Methods] The study population consisted of 30 patients who hadundergone rotator cuff reconstruction surgery, with 10 patients each assigned to thecontrol, experimental I (E-1), and experimental II (E-II) groups. On the day aftersurgery, muscle tone, blood CRP level, and pain were measured. For the following twoweeks, continues passive motion (CPM), icing, cryotherapy, and microcurrent were appliedto the each group. After the respective interventions, CRP levels, pain, and muscle tonenear the shoulder area were measured again. [Results] In the post-hoc test ofbetween-group comparison, a statistically significant difference in CRP level was found inthe cryotherapy group. A difference in shoulder muscle tone appeared only in thesupraspinatus muscle, with post-hoc test results showing that the biggest change occurredin the cryotherapy group. [Conclusion] Cryotherapy may be able to help stabilizeinflammation as well as reduce pain and muscle tension when applied in patients followingrotator cuff reconstruction.

INTRODUCTION

Rotator cuff injury can have a negative effect on shoulder abduction and rotation, as wellas on the function that maintains stability in the glenohumeral joint, and can manifestvarious forms of mechanical damage stemming from a glenohumeral tendon sprain or limitedmotion, fluid leakage in the surrounding area, and muscle load imbalance1⁾. Various surgical techniques, such asminimally invasive arthroscopic repair, are being performed to treat arthrosis that occurssubsequent to rotator cuff injury, and the development of arthroscopic techniques hasresulted in an increasing trend in their use due to easier accessibility to diagnostic andsurgical techniques2⁾. These surgicaltechniques cause pain from deep infection or inflammation, and in particular, arthroscopicshoulder surgery can be accompanied by severe postoperative pain, which may be difficult tocontrol without the use of analgesics3^, 4⁾. Analgesics may cause dizziness, vomiting,and sedation, while also failing to adequately control the pain at times5⁾. Inflammatory cytokines that are secretedduring inflammation not only stimulate the afferent nerve endings to cause pain, but arealso known to have an effect on the degenerative process due to catabolism of theextracellular matrix that comprises the subacromial bursa. Meanwhile, interleukins insidethe subacromial bursa (interleukin-1β, IL-1β) and IL-1β receptor antibodies are known toplay an important role in causing shoulder pain6^,7⁾. Physical therapy interventions forthe alleviation of inflammatory symptoms that appear early postoperative phase and thatpromote bone union and wound healing include icing and cryotherapy to reduce the tissuetemperature, in addition to microcurrent and low intensity pulsed ultrasound8^,9^,10^,11⁾.However, because their efficacies are still debatable, evaluation of such techniques isstill in need12⁾. Accordingly, the presentstudy applied early intervention via microcurrent and cryotherapy on the day after surgeryin patients who underwent rotator cuff repair surgery, as part of an investigation of theeffects of such interventions on pain and inflammation levels via C-reactive protein (CRP)measurement, as well as on changes in muscle tone. Moreover, the study also aimed to provethe efficacy of these intervention measures to provide basic clinical data for systematicand effective methods for postoperative patient care.

SUBJECTS AND METHODS

The present study was conducted over a period of approximately two months, from October 10,2016 to November 30, 2016. The study was conducted following the reception of approval fromthe Institutional Review Board at Sehan University (IRB) (Approval number: 2016-13). Thestudy participants were male patients, 40–55 years of age, who had undergone en-masse suturebridge repair for shoulder rotator cuff tear at a medical institution located in SouthJeolla Province. The selection criteria included patients who underwent rotator cuffreconstruction surgery following the diagnosis of a partial rotator cuff tear (<3 cm),and who did not have any other musculoskeletal or neurological disorders that may affect theoutcomes of the present study. A total of 30 participants who fully understood the contentsof the study and who voluntarily signed an informed written consent form were selected forinclusion. The selected participants were divided into three groups of 10 each for thecontrol, experimental I (E-I), and experimental II (E-II) groups, respectively, and on theday after their surgeries, a myotonometer was used to measure their muscle tone around theshoulder area, while their inflammation levels were determined via blood CRP levelmeasurement. CPM and icing were applied to the control group using ice pack; CPM andcryotherapy were applied to the E-I group; and CPM and microcurrent were applied to the E-IIgroup (Table 1). Each intervention was applied six times per week for two weeks, with CPMcommonly applied for 20 min; icing applied for 15 min; cryotherapy applied for 30 sec eachfor four repeated applications; and microcurrent applied for 20 min each with a stimulationsetting of intensity of 30–40 μA, pulse frequency of 10 Hz, and pulse width of 50 ms. Aftertwo weeks of intervention application, CRP levels, pain, and muscle tone near the shoulderarea were measured again. All 30 participants complied with an analgesic prescription duringthe intervention period.

The cryotherapy (Cryo-master; MESH Co., Ltd., Korea) method used in the present study wasbased on a CO₂ spray method that utilized cryogenic shock waves at −78°C and 50bar. The device is used for reducing pain and alleviating inflammation in patients aftersurgery or during a period of high inflammation. The microcurrent (MC PLUS; Cybermedic Co.,Ltd., Korea) technique used a portable device with two attachable carbon electrodes; thetherapy was applied following the application of gel to facilitate current delivery to theskin.

Muscle tone was measured by using Myoton^® PRO (Myoton AS, Tallinn, Estonia) onthe upper trapezius and SCM. Myoton^® PRO is able to diagnose musclecharacteristics in simple and non-invasive manner, and provides highly reliable data withintra-rater reliability correlation coefficient of 0.94–0.9913^, 14⁾. With the participantseated in a chair with back support, the probe of the Myoton PRO device was placedvertically on the area around the supraspinatus and infraspinatus muscles to measure tone(Hz), elasticity (log decrement), and stiffness (N/m). With respect to the measurementmethod, the skin was pressed down with a force of 0.18 N; 0.4 N of impulse was then appliedinstantaneously for a total of five times in 15 ms intervals15⁾. Subsequently, skin surface vibration caused by theMyoton^® PRO device was measured to confirm the mechanical parameter values.Measurements were repeated three times in 15 s intervals, and the mean value of the repeatedmeasures was recorded.

Following the collection of 5 cc of blood from each patient, CRP was tested by monoclonalantibody-based latex agglutination test using the A15 analyzer (Biosystems SA, Barcelona,Spain). Moreover, a visual analog scale (VAS) developed by Scott and Huskisson16⁾ was used to assess the level of subjectivepain in participants.

SPSS 18.0 for Windows (IBM Corp., Armonk, NY, USA) was used for data analysis. Normality ofthe general characteristics of participants, and group CRP levels were tested by using theShapiro-Wilk test. A two-way ANOVA was used for between-group comparisons, while the Tukeytest was used for post-hoc analysis. The significance level was set to p=0.05.

RESULTS

In the present study, post-hoc test results from between-group comparisons showed that thecryotherapy group had the largest change in CRP levels (p<0.05; Table 2). With regards to shoulder muscle tone, a difference in muscle tone was foundonly in the supraspinatus muscle, with post-hoc test results showing the largest changebeing present in the cryotherapy group (p<0.05; Table 3) (Table 4).

DISCUSSION

With respect to the icing, cryotherapy, and microcurrent techniques that are applied forthe purpose of reducing postoperative inflammation in clinical settings, the present studyapplied these techniques in the early rehabilitation process of patients who had undergonerotator cuff repair surgery, in order to investigate their effects on the reduction ofinflammation as shown by changes in CRP levels, along with related muscle tone changes. Forthis purpose, interventions were applied for two weeks to 30 participants who had undergonerotator cuff repair, and pre- and post-hoc tests were performed.

Inflammatory complications that occur during the early stage of postoperativerehabilitation can slow down aggressive rehabilitation, while proper intervention in theinflammation process early on can relieve symptoms by causing reduced tissue metabolism andenzyme activities17^, 18⁾.

Speer et al.19⁾ divided 50 shouldersurgery patients into experimental and control groups to test the efficacy of cryotherapy,and found that the application of cryotherapy led to the patients sleeping better at nightand demonstrating less injuries during the rehabilitation period, which were attributed tothe reduction in pain and swelling .

Murgie and Cassard20⁾ reported thatsimultaneously applying cryotherapy and dynamic intermittent compression on anteriorcruciate ligament reconstruction patients resulted in a reduced use of analgesics and inimproved knee function. Lessard et al.21⁾also reported that patients who underwent cryotherapy following arthroscopic knee surgerywere able show early weight-bearing and a reduced use of analgesics. A study by Kang etal.22⁾ also reported that the combinedapplication of cryotherapy and pulsed ultrasound on total knee arthroplasty patientsresulted in a significant difference in CRP levels, showing a positive effect on the aspectsof pain, function, and inflammation relief.

In the post-hoc test involving between-group comparisons, the cryotherapy group showed astatistically significant change in CRP levels, which supported the results of previousstudies. Notably, some studies have suggested that reduced joint temperature due tocontinuous cryotherapy after surgery may stimulate the activities of proteolytic enzymes,which can have a negative impact on the cartilage of joints, while others have recognizedits efficacy for non-pharmacological pain suppression and explained that this was a basicpain suppression mechanism from reduced tissue temperature23⁾. Moreover, the reason why the findings were contrary to thoseachieved with the use of an ice pack, which is based on the same temperature mechanism, canbe explained by the therapeutic mechanism of cryotherapy used in the present study. Highlypressurized gas yielding low temperature therapy takes away nearby heat through a processthat deposits solid dioxide (dry ice) that turns white when liquid carbon is applied to theskin. The amount of heat absorption through this process is larger than the amount of heatabsorption activated through convection with an ice pack, while also causing a rapiddecrease in skin temperature24⁾. Moreover,a skin temperature of ≤13.6 °C is needed to induce local pain, while nerve conductionvelocity is reduced at ≤12.5 °C25⁾, and atissue temperature decreased to 10–11 °C can reduce metabolic enzyme activities26⁾. A sudden temperature change that occursin this manner can increase the activities of the sympathetic nerves, and such activities ofthe sympathetic nerves regulate inflammation and the release of cytokines. Moreover, thereis a theoretical background that states that association with the sympathetic nervous systemis important for treating inflammation, and thus, attention should be paid to thisaspect27⁾. Kim et al.28⁾ indicated that if the value for muscletone is high among the various measured elements of a myotonometer, then an increased levelof pain or exercise overload would appear. Shoulder muscle tone in the present study alsoshowed a difference only in the supraspinatus muscle, and post-hoc test results showed thatthe biggest change occurred in the cryotherapy group. It is believed that such a decreasewas the result of a reduced inflammatory response from the protective reflex contraction ofthe muscles surrounding the shoulder, which may be attributed to the anti-inflammatorymechanism of cryotherapy.

Based on the findings in the present study, it was confirmed that cryotherapy can helpreduce pain and muscle tension by stabilizing the inflammation process following rotatorcuff reconstruction. However, the present findings cannot be generalized because the studyconsidered patients from only a single medical institution, the study period was short, andthe patients’ different activities of daily living were not adequately controlled. Moreover,the theoretical background on the therapeutic effects of cryotherapy has not yet been firmlyestablished, and still remains under debate. Therefore, it is believed that futureprospective studies that take into consideration the various aspects, with changes to theduration of treatment and application methods, are needed.

Acknowledgments

This paper was supported by the Sehan University Research Fund in 2017.

REFERENCES