The Effects of Extracorporeal Shock Wave Therapy in Patients with Coccydynia: A Randomized Controlled Trial

Coccydynia is pain in the coccygeal region, and usually treated conservatively. Extracorporeal shock wave therapy (ESWT) was incorporated as non-invasive treatment of many musculoskeletal conditions. However, the effects of ESWT on coccydynia are less discussed. The purpose of this study is to evaluate the effects of ESWT on the outcomes of coccydynia. Patients were allocated to ESWT (n = 20) or physical modality (SIT) group (n = 21) randomly, and received total treatment duration of 4 weeks. The visual analog scale (VAS), Oswestry disability index (ODI), and self-reported satisfaction score were used to assess treatment effects. The VAS and ODI scores were significantly decreased after treatment in both groups, and the decrease in the VAS score was significantly greater in the ESWT group. The mean proportional changes in the ODI scores were greater in the ESWT group than in the SIT group, but the between-group difference was not statistically significant. The patients in the ESWT group had significantly higher subjective satisfaction scores than SIT group. We concluded that ESWT is more effective and satisfactory in reducing discomfort and disability caused by coccydynia than the use of physical modalities. Thus, ESWT is recommended as an alternative treatment option for patients with coccydynia. Trial Registration ClinicalTrials.gov NCT02313324

discography indicates that the following five causes may play a role in these traumatic and idiopathic coccydynia: anterior luxation, hypermobility, coccygeal spicules, subluxation, and luxation. 2,6 MRI studies show that mobility during tightening of the muscles of the pelvic floor and defecation is independent of age, gender, and the presence or absence of coccydynia. The coccyx usually consists of four bony segments that are attached cranially to the sacrum at the sacrococcygeal joint. Between the first two segments, a rudimentary intervertebral disc may be present and can form a potential localization point for post-traumatic hypermobility. 3 The other segments are synarthroses and have no mobility. Due to a more posteriorly situated sacrum and coccyx, 7 and a longer coccyx relative to men, 8 females have a greater chance of developing coccydynia. A clear relationship exists between coccydynia and the female gender; the female/male incidence ratio is 5:1. 9 Treatment of coccydynia includes conservative treatment methods such as nonsteroidal anti-inflammatory drugs (NSAIDs), opioid drugs, gabapentin, pregabaline, myorelaxants, postural education, use of special cushion, physical therapy (massage, hot pack, electrical stimulation, and manual therapy), 8,[10][11][12] and interventional treatment methods such as local anesthetic, steroid injections, radiofrequency (RF) treatment. 8,13,14 Some patients may need surgical treatment such as coccygectomy. [15][16][17] In general, most treatments have been evaluated in retrospective studies, but there have been few controlled studies showing the efficacy of any known coccydynia treatments.

【Conservative Management】
In the acute phase of a post-traumatic coccydynia, a conservative policy has been proposed.
This conservative approach includes NSAIDs and an adapted sitting posture. 8 In a controlled pilot study, conservative treatment, in the sense of mobilization of the coccyx, has been shown to have a long-term effect in 25% of patients. 10 A subsequent randomized controlled study, by the same group, compared intrarectal manipulation (applied in three 5-minute sessions over a period of 10 days) to shortwave magnetic field physiotherapy (delivered in three sessions over a period of 10 days). Intrarectal manipulation was more effective than the control treatment in improving visual analog scale (VAS) scores as well as functional and pain questionnaires. However, the efficacy was modest. 11 Infrared thermography before and after manual therapy and diathermy in patients with coccydynia objectively showed decrement of surface temperature correlating (r = 0.67, P < 0.01) with changes of subjective pain intensity after treatment. 12 【Interventional Management】 簡易審查計畫案計畫書 文件編碼 KMUH/IRB/AF/02-008/09.0

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In a prospective study, the combination of local injections of corticosteroids/local anesthetic with mobilization was shown to have a positive effect in 85% of cases, while local injections of corticosteroids/local anesthetic alone produced a 60% success rate. 1 The effect of intradiscal corticosteroid injections into the coccyx has yet to be demonstrated. 2 In addition to local injections of corticosteroids/local anesthetic, interventional pain management techniques include radiofrequency (RF) treatment of the sacral roots. The use of RF with a minimal invasive procedure for this group of patients as an alternative to surgical treatment and it might be an additional option among non-surgical treatment methods. 18 But further randomized prospective controlled studies in patients with coccydynia are needed to fully evaluate the effectiveness of RF.
【Surgical Management】 In the subacute and chronic phases, many forms of treatment for coccydynia are advised, up to and including surgical removal of the coccyx. Although retrospective studies are still being published concerning coccygectomy, 19 there are strong contraindications to this surgical intervention due to the long-term moderate results and the chance of major complications. 8 In brief, interventional or surgical management always carries the risk of going through the disc and penetrating the rectum. Based on the results and complications reported, these treatments are not recommended for the principal treatment tools. 20 【Shockwave therapy】 Some recent studies have shown that shockwave therapy is promising recovery in musculoskeletal disorders patients. The sources of shockwave generation include electrohydraulic, electromagnetic and piezoelectric principles. Electrohydraulic shockwaves are high-energy acoustic waves generated under water explosion with high voltage electrode. Shockwave in urology (lithotripsy) is primarily used to disintegrate urolithiasis, whereas shockwave in orthopedics (orthotripsy) is not used to disintegrate tissues, rather to induce tissue repair and regeneration. 21 The most important physical parameters of shockwave therapy for the treatment of orthopedic disorders include the pressure distribution, energy flux density and the total acoustic energy. In contrast to lithotripsy in which shockwaves disintegrate renal stones, orthopedic shockwaves are not being used to disintegrate tissue, but rather to microscopically cause interstitial and extracellular responses leading to tissue regeneration. 21 The application of shockwave therapy in musculoskeletal disorders has been around for more than a decade and is primarily used in the treatment of sports related over-use tendinopathies such as proximal plantar fasciitis of the heel, lateral epicondylitis of the elbow, calcific or non-calcific tendonitis of the shoulder and patellar tendinopathy etc. [22][23][24][25][26][27][28][29][30][31][32][33][34][35][36][37] The success rate ranged from 65% to 91%, and the complications were low and negligible. shockwave These findings imply the possibility of shockwave therapy in inducing tissue repair and regeneration in coccydynia patients. Therefore, a better understanding of the mechanism in recovery of coccydynia is a prerequisite for improving our rehabilitation services in the future. Although there are other interventional treatments relative to coccydynia, there is no shockwave therapy specifically focused on this disorder. However, to our knowledge, the effects of shockwave therapy on the underlying mechanisms responsible for recovery in coccydynia patients are not well understood. In the present study, we aimed to investigate the effectiveness of shockwave therapy in patients with coccydynia that could be more effect than conventional treatment protocols.

Study design:
(1) Sample We will recruit a total of 40 patients with a diagnosis of Coccydynia referred to Department of

2.)
Patients who were over 21 years and older and skeletally matured.

4.)
Patients who have good knowledge to complete the questionnaire assessment.

5.)
Patients who understood and complied with the nature of the study participation.

6.)
Patients who agree to sign the informed consent form.

2.)
Patients on immunosuppressant agents and/or corticosteroid within 6 months.

5.)
Patients with neuropathic sign which could influence treatment effect.
【Sample Size Estimation】 Because the sample size calculation for this study can't determine from the previous finding, An estimate of patients for each group required for a power of 80%, a one-sided type I error of 5%, and the dropout rate of 15% assumed from our experience with follow up evaluation of patients.
Taken these considerations together, we plan to recruit 20 patients for each group to have an adequate sample size to test the proposed hypotheses.

(2) Randomized Controlled Trial:
All the patients gave their informed consent, after which they were randomized to the experimental group or control group. Each patient was given a sealed envelope that bore his or her enrollment number and contained the treatment to which he or she was randomized. The letter was opened in the presence of the patient.

(3) Treatment Protocol:
【Shockwave Therapy Group】 Patients in the study group received shockwave treatment as outpatients with no local or regional anesthesia. The source of shockwave was from the BTL-5000 series (BTL Industries Ltd; Hertfordshire, United Kingdom). Each patient was treated with the frequency of 10 Hz, 4 bar pressure, 2000 shocks, applied once a week, with a maximum of 4 treatments. The dosage was chosen based on our previous experience in shockwave application for other musculoskeletal disorders. [38][39][40][41][42][43][44][45] The point of maximal tenderness was elicited by palpation, and the location of the lesion was focused with the laser control guide of the device. The depth of treatment was estimated clinically and confirmed with an ultrasound guide. Surgical lubricant was applied to the skin in contact with the shockwave tube. Treatment began with slow frequency at 1 impulse of shock per second and gradually increased to 2 shocks per second as the patient could tolerate the procedure.
Any side effect within both groups will be recorded by the therapist. 46 【Control Group】 Patients in the control group were treated with conventional physiotherapy including short-wave diathermy and interference current therapy (IFC). The patient is asked to lay prone with the lower back and buttocks exposed. A pelvic pillow support was given. Firstly, a qualified therapist applied continuous short-wave diathermy using the machine (SW50, Cosmogamma, Italy).
The hinge-type drum of the inductive electrode was used with 2 lateral sections containing the actual electrodes and the central unit consisting of the lead connections only. The drums were spread widely and placed so that the entire coccygeal area of the patient was in the contact field. A towel was placed under the drum to separate the lead wires from the patient's skin. The short-wave diathermy treatment was carried out for 20 minutes. 12 Secondly, the therapist administered the IFC which was a 4 KHz sinusoidal biphasic electric current with amplitude that was modulated between 60 and 100 Hz, with a ramp and fall of one second each and constant phases of two seconds in between to the subject who keep the same position as short-wave diathermy. 29,30,36,47 For each patient two paired reusable hypoallergic vacuum circular electrodes were used (Minato Inc, SK-9S, Japan). Four electrodes were placed widely in order to cover the entire coccygeal area. This electrotherapeutical concept is commonly recommended and used. 48 The position of all electrodes was kept fixed during all treatment sessions for 20 minutes. Hence, the control group accepts totally

(4) Outcome Measures:
All the subjects' demographic characteristics and related measurements were recorded before the experiment include age, gender, body mass index (BMI), duration of the complaints, and traumatic or nontraumatic etiology.
Primary outcome variables for this study will be the visual analogue scale (VAS) 11,12,18 and the Oswestry Disability Index (ODI). 49 The first subjective assessment of pain intensity was analyzed applying visual analogue scale (VAS). The VAS is used to measure pain on a 100 mm horizontal axis between the extreme left endpoint of no coccyx pain and the extreme right endpoint of the worst pain. The distance is then measured and pain is recorded on a 100-point scale. 11,12,18 The second subjective assessment of pain intensity was Oswestry Disability Index version 2.1 (also known as the Oswestry Low Back Pain Disability Questionnaire) which is an extremely important tool that researchers and disability evaluators use to measure a patient's permanent functional disability. The test is considered the "gold standard" of low back functional outcome tools. There are totally 10 sections within ODI. For each section the total possible score is 5: if the first statement is marked the section score = 0; if the last statement is marked, it = 5. The percentage of the total scores divided by total possible score means level of disability (0% to 20%：Minimal disability；21%-40%：Moderate disability；41%-60%：Severe disability；61%-80%：Crippled； 81%-100%：Bed-bound). 49 The clinical measures will be administered to patients by the same blinded rater at pre intervention, 2 weeks intervention, post intervention, 1-month follow-up. Prior to administration of clinical measures, the blinded rater will be trained to properly administer these measures. The assessor was also blinded to know each other's group during the study period.

(5) Data analysis
In this study, repeated measures analysis of variance (ANOVA), treating time as a within subject factor and group as a between-subject factor, followed by post hoc multiple comparisons were used to evaluate treatment efficacy with group as the between-subjects factor and scores of the visual analogue scale (VAS) and the Oswestry Disability Index (ODI) as the dependent variables.
To take into consideration the effect of multiple testing, the Sharpened Bonferroni method was used to adjust for individual alpha level, while the overall level of significance was set at 0.05. (

1) Anticipated Results
When the study is completed, there will be some breakthroughs in the field of shockwave therapy in coccydynia. This will be the first study comprehensively investigating the effects of shockwave therapy in patients with coccydynia. According to regaining functional activity on decreasing pain based on clinical scales such as VAS, ODI scores, the effectiveness of optimal therapeutic parameter settings will be evaluated. The results of this study will help to clarify the effects and suitability of shockwave intervention, and keep our domestic research team the leader position in this field. After completing this project, we will continue to promote the function of shockwave treatment system. Based on above-mentioned results and the evidence-based combination of parameters, we will be in a pole position to further investigate the feasibility of the program for shockwave usage.

(2) Training effect of staff
The researcher can familiar with treatment protocol and operation of shockwave therapy, understanding the process of recovery in patient with coccydynia. That clinician can improve their technique using on other patient with coccydynia. Moreover, the rater will well-known about those assessment tools.

Possible adverse effects and managements:
Shockwave therapy is a novel non-invasive therapeutic modality without surgery or surgical risks, and the clinical application of shockwave therapy steadily increases over the years. Although Postoperative management included ice pack to the treatment site and a prescription of nonnarcotic analgesic, such as acetaminophen, when subject have any side effect during the intervention management. Patients were allowed to resume light activity; however, heavy activities including sports were not permitted and following by clinical doctor for 4 to 6 weeks.

Enrollment method:
■Oral introduction and explanation □Poster □Internet □Others： □Not applicable

Please describe the ethical concerns of this study:
We propose to recruit about 40 eligible patients with coccydynia during the study period.
Clinical information about the patients will be obtained from medical records. Therefore, an invitation letter will be sent out to obtain written informed consent from each participant. The letter will explain plainly and in simple terms to address the purposes of the study, the procedures, and the risks and benefits, as well as the processes of informed consent in this project. In addition, we will obtain the approval of the IRB (Institution Review Board) of the Kaohsiung Medical University Chung-Ho Memorial Hospital. The results of this project will remain confidential.
Furthermore, the participants' data will be kept in locked file cabinets located in research office, accessible only to the study personnel.

Management of recruited participants' samples:
Not applicable

State if informed consents will be provided to participants:
Yes, the informed consents will be provided to participants before entering the study.