TENNIS ELBOW SHOCK WAVE

 A comparative study of the efficacy of ultrasonics and extracorporeal shock wave in the treatment of tennis elbow: a meta analysis of randomized controlled trials

 

Chenchen Yan1, Yuan Xiong1, Lang Chen1, Yori Endo2, Liangcong Hu1, Mengfei Liu1, Jing Liu1, Hang Xue1, Abudula Abududilibaier1, Bobin Mi1* and Guohui Liu1*

 

  

Abstract

 

Background:  Tennis elbow or lateral epicondylitis is a common source of pain among craftsmen. Although it cannot be completely resolved, extracorporeal shock wave therapy (ESWT)  and ultrasonic (US)  have been Found to be effective  for tennis  elbow as highlighted  in  previously published  randomized controlled trials (RCTs)  and reviews.  However, the efficacy of these  two therapies in  treating tennis elbow is unknown.  This meta-analysis  compares the effectiveness of  ESWT  and US in relieving  pain and restoring the functions of Tennis elbow following  tendinopathy.

Methods:  RCTs  published in  the  PubMed, Embase,  Cochrane Library, and Springer Link databases  comparing ESWT  and US in  treating  tennis  elbow  were identified  by a software and manual search. The  risk of bias and clinical  relevance of the included  studies were assessed. Publication bias was explored using funnel  plot and statistical  tests (Egger’s  test and Begg’s  test).  The  major  outcomes  of  the  studies  were analyzed  using  theReview  Manager 5.3.

Results: Five RCTs comprising five patients were included in the present meta-analysis. The results revealed a significantly lower VAS score of pain in the ESWT group (1 month: MD = 4.47, p = 0.0001; 3 months: MD = 20.32, p < 0.00001; and 6 months: MD = 4.32, p < 0.0001) compared to US. Besides, the grip strength was markedly higher 3 months after the intervention in ESWT (MD = 8.87, p < 0.00001) than in the US group. Although no significant difference was observed in the scores of the elbow function after 3 months of treatment (SMD = 1.51, p = 0.13), the subjective scores of elbow functions were found to be better in the ESWT group (SMD = 3.34; p = 0.0008) compared to the US group.

Conclusions: Although there was no significant difference in the elbow function evaluation scores between ESWT and US, the superiority of the ESWT group in the VAS of pain (both at 1 month, 3 months, and 6 months follow-ups) raised grip strength in ESWT group and the scores for subjective evaluation of efficacy indicated that ESWT offers more effective therapy for lateral epicondylitis than US therapy.  

* Correspondence: This email address is being protected from spambots. You need JavaScript enabled to view it. This email address is being protected from spambots. You need JavaScript enabled to view it.

1Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Rd. 1277#, Wuhan

430022, Hubei, China

Full list of author information is available at the end of the article  © The Author(s). 2019 Open Access This article is distributed  under the terms of the Creative Commons Attribution 4.0

International License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons  license, and indicate  if changes were made. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Introduction

It  is  well  known  that  lateral  epicondylitis   (LE),  also known  as tennis  elbow, is one  of the  most  ubiquitous cause  of  elbow  pains  among  craftsmen  [1–3].  It  has an  incidence   of  1–3%  in  the  general  population  and constitutes 7 per  1000  primary  care  consultations an- nually  [4, 5]. Tennis  elbow  manifests  as a tenderness over  the  lateral  epicondyle  of the  humerus,  as well  as a pain  on  resisted  dorsiflexion  of the  wrist  [5, 6].  Al- though   the  cause  of  tennis   elbow  is  often  non-specific,  it   is   most   commonly    associated   with   work- related  or  sports-related  overuse  of  the  elbow  resulting in hypo vascularity  in the  area  [7–9].  Its  symptomscan  persist  for  half a year to  2 years, but  may  resolve naturally  in a year or  so [10, 11]. The  pain  mainly  affects  the  dominant arm,  and  the  severity  of this  condition   tends   to   be   high   and   persistent  for   longer duration in female [12].

Although   the  diagnosis   of  tennis   elbow  was  standardized   many  years  ago  based  on  its  symptoms   [5,13–15],  treatments  remain   largely  non-definitive  and variable.   There   are,   however,   many   therapies   with beneficial  effects,  as  revealed  in  some  clinical  studies [2,   3,   16].   Topical   non-steroidal   anti-inflammatory drugs  (NSAIDs)  are  mainly  prescribed   for  short-term pain  relief, whereas  oral  NSAIDs  are  aimed  at  short- term   improvement  in   pain   relief  and   function.   An extensor    fasciotomy    was   demonstrated   to   be   an effective  treatment  for  refractory   chronic   lateral  epicondylitis   [17].   Extracorporeal   shock   wave   therapy (ESWT),  ultrasonic   therapy  (US), corticosteroid injections,   physiotherapy,   and   acupuncture  are   effective therapies   for  long-term  pain  relief  and/or  functional improvement for patients  with  tennis  elbow [18]. Due to  their   non-invasive   and  convenient   nature,   ESWT and  US  are  considered  important  adjuvant   interventions  for treating  tennis elbow [19].

Indeed,  either  of  these  two  treatments  is  routinely used  as the  main  adjuvant  therapy  [20,  21].  However, there   is  no   consensus   as  to   which   method   is  the more   effective  in   treating   tennis   elbow   [22].  It   is therefore  meaningful  to make  a  direct  comparison be- tween   ESWT  and   US  on   their   efficacy  and   safety. This  study  compares   the  therapeutic  effects  of  these two  therapies   in   reducing   pain   intensity,   improving mobility   in    daily   activities   and    self-evaluation    of recovery.

 

Materials and methods

Searches

This  study  was conducted according  to  the  guidelines outlined   in  the  PRISMA  (Preferred  Reporting   Items for  Systematic   Review  and  Meta-Analysis).   The   following  databases   were   explored   to   extract   relevant data:   The   Cochrane    Library,   PubMed,   MEDLINE, Springer Link,    and    OVID.   Appropriate    randomized controlled  trials   (RCTs)   published   between   January 2001  and   March   2019  were  enrolled   in  this   study. The  following subject  terms  were employed  in the  literature   search:  tennis  elbow,  lateral  epicondylitis,  ultrasonics,   and   extracorporeal   shock   wave,  and   the entry  terms   related   to  the  subject  terms   mentioned above  were  applied   in   the   same   way.  The   specific search  employed  was  as  follows: (((((ultrasonic)   AND ultrasonics))   AND  (((((((((((((((((extracorporeal  shock- wave  therapies)  or  shockwave  therapies,   extracorporeal) or  shockwave  therapy,  extracorporeal) or  therapy, extracorporeal  shockwave)  or  shock  wave therapy)  or shock   wave  therapies)   or   therapy,   shock   wave)  or extracorporeal  shock  wave  therapy)  or  extracorporeal high-intensity  focused   ultrasound   therapy)   or  extra- corporeal   high  intensity   focused  ultrasound  therapy) or  HIFU therapy)  or  HIFU therapies)   OR  therapy,  HIFU) or high-intensity focused ultrasound therapy)  or high intensity  focused  ultrasound  therapy))   or  extracorporeal shock  wave))  and  ((tennis  elbow)  and  (((((((((((((elbow, tennis)  or  elbows,  tennis)  or  tennis  elbows)  or  lateral epicondylitis)  or  epicondylitiden,  lateral)  or  epicondylitis,  lateral)  or  lateral  epicondylitis)   or  epicondylitis, lateral   humeral)   or   epicondylitiden,  lateral   humeral) or  humeral  epicondylitis,  lateral)  or  humeral   epicondylitis,   lateral)   or   lateral   humeral    epicondylitis)   or lateral  humeral  epicondylitis)))  and  ((randomized  con- trolled  trial  [Publication  Type]  or  (randomized  [Title/  Abstract]    and   controlled    [Title/Abstract]   and   trial [Title/Abstract]))).

 

Study inclusion  and  exclusion  criteria

The  titles  and  abstracts   of  the  articles  that  appeared in  the  literature   search  were  reviewed  independently by two  authors   to  evaluate  their  eligibility for  enrollment.  The  authors   settled  any  disagreements through discussion.  A third  person  acted  as a referee  to  adjudicate  the  debate  between the  investigators.   The  following  criteria   were  used   to  select  the   articles:  (1) clinical  study  was  designed  and  conducted as  a  randomized  controlled trials  (RCTs),  (2)  the  study  made a  comparison between  ESWT  and  US on  efficacy for treating   lateral  epicondylitis,  (3)  the  article  was  writ- ten  in  the  English  language   or  had  been  translated into  English,  and  (4)  the  major  outcomes  measured were  the  efficacy of pain  relief  and  functional  restoration.  The  exclusion  criteria  were  as  follows:  (1)  the study   shared   the   same   data  set,  (2)  the   evaluation methods   did  not  address  the  major  outcome,  and  (3) the  participants  included  in the  study  had  co-morbidities  and/or  other  joint  diseases  such  as  hypertension and  rheumatoid arthritis.

Table 1 The characteristics of included studies

Study         Year      Country      Patients (n)           Age (year)                                   Gender                                                     Symptom duration (months)          Side of involvement                       Study

 

			ESWT	US		ESWT	US		ESWT		US			ESWT	US		ESWT		US		design
									Male	Female	Male	Female					Left	Right	Left	Right
Gunduz	2012	Turkey	20	19		44.9 ± 9.9	43.6 ± 9.1		8	12	5	14		30 (1–90)	30 (7–90)		5	15	4	15	RCT
Kubot	2017	Poland	30	30		47.6 ± 7.66	43.9 ± 9.44		8	22	17	13		> 2	> 2		–	–	–	–	RCT
Pawel	2015	Poland	25	25		47.9 ± 4.4	49.0 ± 4.5		–	–	–	–		14.9 ± 2.1	15.1 ± 1.9		0	25	0	25	RCT
Yalvac	2018	Turkey	20	24		43.75 ± 4.52	46.04 ± 9.24		5	15	8	16		7.9 ± 3.3	8.2 ± 3.6		3	17	4	20	RCT
Soheir	2013	Egypt	20	20		38.4 ± 3.67	38.25 ± 4.19		12	8	12	8		>10	>10		15	4	17	4	RCT

 

 

    

  Table 2 Characteristics of the four trials selected showing general intervention information

 

Study	Follow	Interventions		Outcome measures	Distribution kit	Calculation software
	month	ESWT	US
Gunduz	6	ESWT (pressure 1.4 bar, frequency	Ultrasound therapy (1 W/cm2, 5 min)	VAS, grip strength, pinch strength	Sealed numbered envelopes	Statistical Package for Social
		4.0 Hz, number 500) for ten	and friction massage (5 min) for ten		without strata	Sciences, version 11.5
		sessions	sessions
Kubot	6	First phase: 2000 pulses with a wavelength of 8 Hz and a	First phase 3 min, a 5 cm2  with 1 MHz, producing a wave of 0.5 W/cm2; second	VAS, subjective pain, frequency f pain, use of analgesic drugs.	Randomized by unspecific way	SPSS 24 program
		pressure of 1.5–2.5 bar; second:	lasting 2 min, same as before	Mobility limitation of the affected
		2000 pulses at 8 Hz and 2.5–3.5 bar		limb
Pawel	3	1000, 1500, and 2000 pulses,	Intensity, 0.8 W/cm2; 100%  fill; carrier	VAS (rest,  grip, palpation,	MedCalc statistical	MedCalc statistical software
		pressure, 2.5 bar; frequency, 8 Hz; energy density, 0.4 mJ/mm2	frequency, 1 MHz. Ten treatments 3 times per week	Thomsen test, Chair test); overall outcome score	software	version 15.2.1
Yalvac	3	10e15 Hz, 1.5e2.5 bar energy	1 cm2  application area, at 1.5 W/cm2, 1 MHz	VAS, grip strength evaluation,	Coin tossing method	Number Cruncher Statistical
		density, 2000 pulses, once a week	frequency, continuous mode in painful area,	pressure-pain, DASH/quickDASH,		System (NCSS)
		for three sessions	5 min once a day, 5 days a week, for	short Form-36
			10 sessions in total
Soheir	6	Orthospec (Medispec LTD,	Ultrasound shack wave Phyaction 190 serial	VAS at ease/work, grip strength,	The use of computer-	Computer program SPSS 16
		Germantown, MD) portable ESWT	number 2745,  230 V, 300 mA/50–60 Hz,	Chair test, Cozen test, tennis	based 1:1 randomization
		shack wave; single phase 60/50 Hz and	Pus: 8w. Continuous mode 1.5 w/cm,	albow test	scheme
		10/5A	frequency 1 MHz

 

 

 Fig. 1 Flow diagram for the included studies

 

 

Data extraction strategy

Based  on  the   pre-determined  criteria,   the   following data   was  extracted   independently  from   the   selected articles  by  the  two  authors:  background  information such  as  the  country   of  the  study,  interventions,  and major  and  minor  outcomes,  and  the  characteristics of the  study  subjects  such  as  ethnicity,  age, gender,  and duration  of the  symptoms.  A third  investigator  examined  the  discrepancies   in  data  extraction.  The  results are provided  in Additional  file 1.

 

 

Quality and  risk of bias assessments

The   modified   Jadad  scale  was  used  to  evaluate  the quality  of the  studies,  while  the  Cochrane  Handbook for  Reviews  of  Interventions  (RevMan   version   5.3) was used  to  assess the  risk  of bias.  The enrolled  articles   were   reviewed   by   two   authors.    Each   of   the

studies  was  assigned  a  score  corresponding to  “low,”

“high,”  or  “unclear”  according  to  the  following  items:

selection    bias,    performance   bias,    detection    bias, attrition  bias,  reporting   bias,  and  other  biases.  Any

 

disagreements   between    the   authors    were   resolved through  discussion.

 

 

Data synthesis and  presentation

The  RevMan  statistical  software  (RevMan  version  5.3) was  used  to  analyze  the  data  extracted   from  the  en- rolled  articles.  In  this  study,  binary  data  was  analyzed to  provide   a  statistical   summary   of   the   risk  ratios (RR) and  the  associated  95%  confidence  intervals  (CI) (α = 0.05  for  the  inspection  standards).   The  continuous  data  were  expressed  as means  and  standard deviations   (SD),  which  were  then   pooled   to  a  weighted mean  difference  (WMD)  and  95% confidence  interval

(CI).  Heterogeneity  was  examined   by  the  I2   statistic.

Outcomes with  an I2  statistic  of 25–50%  were  considered  to have a low heterogeneity,  and  50–75%  a mod-

erate    heterogeneity,    while   I2 > 75%   reflected    high

heterogeneity.   For  the  outcomes  with  the  I2   statistic exceeding  50%, subgroup   analyses  were  conducted to

investigate  the  sources  of  heterogeneity.  A  statistical significance  was  indicated   by  a  p  value  < 0.05.  The

 

 

Fig. 2 Risk of bias summary of the included studies  fixed  effects  were  employed,   for  a  greater  statistical power.

 

Results

Literature search  and  study  characteristics

The  literature   search  yielded  706  articles  which  were considered  as potential  studies.  Three  hundred  eighty- four  publications remained  after  removal  of  the  duplicates  based  on  the  title  and  abstracts.  After  the  preliminary  screening   of  the  384  studies,  a  total  of  21 manuscripts  were  further  evaluated   comprehensively. Finally,  5  articles  were  found   to  be  eligible  for  the present   meta-analysis.   A  total   of  115  patients   were enrolled  in  the  ESWT group,  while 118 patients  were enrolled  in  the  US group.  Tables  1 and  2 summarize the  demographic  characteristics of  the  study  subjects and  quality  scores  of the  studies.  Figure  1  shows  the literature  selection   process   as  described   above   (see Additional   file  2).  This  study  followed  the  PRISMA

2009 checklist  as provided  in Additional  file  3.

 

Risk of bias in included studies

The  risk  of  bias  for  each  of the  assessed  studies  and the   results   are  summarized  in  (Fig.  2  and   Fig.  3). While  specific  methods   for  random  sequence   generation  were  not  mentioned in two  trials  [23, 24], all of the  selected  studies  claimed  a  randomized trial design. One   trial   [25]   did   not   explain   their   methods    for allocation   concealment.  Blinding  processes   were  not clearly  described   in   two  studies   [25,  26].  The   one remaining   trial  [27]  was  considered   to  have  a  high risk due  to  inadequate blinding.

 

Pain scores

The  visual analogue  scale (VAS) was adopted  by all five [23–26, 36] trials to evaluate the degree of pain relief. As shown  in Fig. 4, there  were  no  differences  in the  pain

 

 

 caused  by tennis  elbow  between  the  treatment  groups before  the  intervention  (MD = 0.84,  p = 0.54,  I2 = 0%). However,  the  ESWT group  showed  a  significantly  large reduction in the  level of pain  after  the  treatment at  1 month     follow-up    (MD = 4.47,    p = 0.0001,    I2 = 92%) (Fig. 5) while the  difference  in  the  pain  relief  between the  treatment  groups  persisted   at  3 months   follow-up (MD = 20.32, p < 0.00001, I2 = 98%) in four [23–26] trials (Fig. 6).  On  the  other   hand,  a  remarkable   difference (MD = 4.72, p = 0.0001, I2 = 53%) in VAS score existed at

6 months  between ESWT group and US group (Fig. 7) in three  [23, 24, 36] trials.  These  results  suggest  that  the ESWT has a superior  efficacy than  the US in eliminating  the pain in both short-  and long-term.

A subgroup  analysis based on the race of the subjects was conducted to explore the sources of the high heterogeneity  observed  in  the  pain  scores  across  the  studies. The results  of subgroup  analysis for the Polish subgroup

(MD = 6.17, p < 0.00001, I2 = 72%) and Turkish subgroup

(MD = 3.09, p = 0.002, I2 = 92%), as well as the  total  effect (MD = 6.54, p < 0.0001, I2 = 88%) at 1 month follow-up  are shown  in Fig. 8. The  results  for the  Polish  sub- group (MD = 2.67, p = 0.008, I2 = 93%), Turkish subgroup  (MD = 1.00, p = 0.32, I2 = 96%), and  total  effect  (MD = 1.84, p = 0.07, I2 = 99%) at 3 months follow-up  are  summarized in Fig. 9. The results of the subgroup analysis are explained in the “Discussion” section.

Grip strength at 6 months after  intervention

Two  [23, 36] of the  five trials  were enrolled  to  prepare  evaluation  of grip  strength at  6 months   after  intervention. A comparison was made between ESWT group  and US group  at  1 and  6 months  (Fig.  10). The  results  revealed  that  the  ESWT  group  had  a better  recovery  of grip  strength compared to  the  US  group  (MD = 2.75,

p = 0.06, I2 = 66%) 1 month   after  the  treatment.  Mean-

while, the difference  in comparison between  ESWT and US group  at  6 months  after  therapy  revealed  the  same outcome   (MD = 8.87,  p < 0.00001,  I2 = 44%).  For  these reasons,   ESWT   resulted   in   better   recovery   of  grip strength in LE patients  than  US therapy  in the long and short run.

 

Evaluation  of the  elbow  functions

Three  of the five trials [23, 25, 26] made  a  comparative  evaluation  of the  elbow functions  at  follow-ups  varying from  1 to 6 months.  Elbow  function evaluation  covered the range of motion  of joints, muscle strength,  pain, and activities of daily living. Some special function  evaluation items  included  the  Chair  test, Thomas  test,  and  tennis elbow  test.  The  common time  point  for  follow-up  in these  trials  was 3 months  after  the  treatment (Fig.  11). There   were  no  significant  differences  in  the  function scores  between  the  treatment groups  at  3 months   follow-up  (SMD = 1.51, p = 0.13, I2 = 95%), indicating  that

 ESWT  and  US  have  similar  effects  on  the  functional improvement.

 

Subjective evaluation of therapy efficacy

Of the four  studies,  three  trials  [24–26]  performed  a subjective    evaluation    of    efficacy   in    pain    relief,

Restoration of the   elbow functions,   impact   on   subjects’ ability to  work,  and  so  on.  There  was a  signify- cant    difference    (SMD = 3.34,   p = 0.0008,    I2 = 51%) between   the   ESWT  and   US  groups,   as   shown   in Fig. 12;  thus,  ESWT  provided  more  efficacy in  treatment  than  the  US.

 

Discussion

Tennis   elbow  is  a  common  chronic   joint  condition, which  is  characterized  by  pain  and  tenderness  over the   elbow  [5,  6].  Limited   movements  at  the   elbow joint  may  severely  disrupt  daily  activities  and  work, resulting  in  economic  burden  to  the  society  [27]. Ac- cording  to  previous  studies  [2, 3, 16], there  are  many therapies  for  tennis  elbow,  including  topical  and  oral NSAIDs,   corticosteroid  injections,   ultrasonic   (US), and  extracorporeal  shock  wave  therapy  (ESWT).  Due to the  non-invasive  nature  and  little  to no  side effects or  adverse  events  associated  with  ESWT and  US, they are  preferred   by  many  patients  and  clinicians  as  the main   adjuvant   therapies   for   tennis   elbow   [19].  In addition,  the  efficacy of  these  two  therapies  has  been supported  by  a   growing   number   of  clinical  studies

 

[28–31].  In most  cases, either  the  US or  the  ESWT  is elected  per  case  because  of their  similar  functionality. In  spite  of  that,  there   is  no  consensus  as  to  which therapeutic  approach   is  superior   in  efficacy [22].  To address  this  question,  the  current study  compares  the efficacy of  ESWT  and  US  in  the  treatment of  tennis elbow.

Studies  that  met  the  criteria  for  meta-analysis  were examined  to  extract  data  on  pain  relief and  functional improvement  following   ESWT   or   US   treatment  in subjects  suffering  from  tennis  elbow.  In  addition,  the risk  of  bias  in  each  of  the  studies  was  evaluated  via the  modified  Jadad scale. In  this  meta-analysis,  it was observed  that  ESWT group  had  a higher  reduction in pain  after  1 month   of  treatment as  compared  to  the

US  group   (MD = 3.88,  p = 0.0001,  I2 = 92%);   similar

results  were  obtained  after  3 months  (MD = 20.32,  p <

0.00001, I2 = 98%) of treatment. These  results  indicate that  ESWT  is  a  superior   therapy  compared  with  US

in  providing  a  long-term  pain  relief  in  tennis  elbow. More  importantly,   these  results  were  consistent  with the    previous    findings    by   Rompe    et   al.   [28–31].

However,   there   was  high  heterogeneity  in  the   pain scores   results.   Thus,   a  subgroup   analysis   was  con- ducted   by  dividing  the  short-term  and  intermediate- term  pain  scores  based  on  race. It was  found  that  the Turkish   subgroup   had  a  higher  heterogeneity  (MD =

3.09,  p = 0.002,  I2 = 92%)  than   the   Polish   subgroup

(MD = 6.17,  p < 0.00001,  I2 = 72%) at  1 month  follow-

     

 up,  and  the  same  relationship  was  true  at  3 months follow-up   for  the   Polish   subgroup   (MD = 2.67,  p =

0.008,  I2 = 93%)  and   Turkish   subgroup    (MD = 1.00,

p = 0.32, I2 = 96%). However,  the  study  by Smidt  et  al. [32] revealed  that  there  is a uniform  course  of  recovery  for  tennis  elbow  without  a  clinical  heterogeneity, suggesting   that   a  high  heterogeneity   attributable  to the  ethnic  variation  may not  be  clinically relevant.

In  term   of  the  functional   recovery,  there   was  no

significant   difference   in  the   functional   scores   when the  two  treatment  groups  (SMD = 1.51,  p = 0.13,  I2 =

95%) were  compared,   as  summarized  in  Fig. 8.  This outcome  of function  evaluation  was different  from  the others  because  of  the  following  reasons.  The  content

 

of  function  evaluation  consisted  of  varied  parts  from trial  to  trial  and  could  be  accounted  for.  Besides,  it was difficult  to  perform  assessment  quantitatively  and in  a  timely  manner due  to  the  complexity  of certain operation.    Further,   the   diversity   of  function   assess scores    would    offset    some    meaningful    differences internally   caused   by   therapies,   which   exhibited   an ultimate   smooth  trend.  Taking  these  two  points  into consideration,  we did not  pay much  attention into  the different     consequence    from     function     evaluation section    and    the    result    should    also    be    treated cautiously.   Further,   a  significant   difference   was   ob- served   in   the   average   scores   between   the   ESWT

group   and   US  group   (SMD = 3.34,  p = 0.0008,  I2 =

51%) after  subjective  evaluation  of efficacy.  Therefore,  it  can  be  concluded   that  ESWT  is  more  effective  in enhancing   recovery  from  tennis  elbow  compared  to US. A  moderate heterogeneity  was  noted  among  the studies.  A subsequent  subgroup  analysis  revealed  that variations   in  the  judgment   scores  adopted   by  these trials  partly  accounted for the  observed  heterogeneity,  for   which   SMD   was   used   to   offset   some   of  the effects.

The  higher  efficacy of ESWT  in pain  relief and  subjective   improvements  in   tennis   elbow   may   be  ex- plained    by   two    mechanisms.    Firstly,    the    energy released  by  ESWT  is  greater   than  that  of  ultrasonic wave.  This  would  likely enable  it  to  better   stimulate pain  receptors  located  in the  skin,  muscle,  connective  tissue,  bone,  and  joint,  as  well  as  to  activate  unmy- elinated   C  fibers  and   A   delta   fibers  to  initiate   the

“gated”  pain  control   system,  leading  to  an  analgesic

effect [33]. Secondly,  ESWT causes  a large  number  of tiny  bubbles  created  within  tissues,  which  rapidly  ex- pand   and   burst   under   the   action   of  shock   wave, resulting   in  high-speed   liquid   micro-jet   and   impact effect.  This   cavitation   effect  is  particularly   effective

 

for   re-opening  occluded   micro vessels   and   releasing the  soft tissue  adhesion  at joints  [34].

The   present   study   has  some   shortcomings   which

need  to be highlighted.  Firstly, the  number of  enrolled trials   is  small  which   limits   the   generalizability   and contingency   of  the  results.  Secondly,  the  side  effects of ESWT and  US, such  as  temporary  reddening  of the skin,  pain,  and  formation  of  small  hematomas,  were not   evaluated   during   follow-up,   which   differs  from the  study  by  Haake  et al. [35]. The  high heterogeneity among  the  results   weakens  the  reliability  of  the  results.  Therefore,  a longer  study  duration is needed  to assess  the  efficacy  of  ESWT  and  US  on  the  tennis elbow function  and  to  explore  the  optimal  therapeutic setting  of ESWT.

Nevertheless,  the  results  from  this meta-analysis  indicate that  the efficacy of ESWT is superior  to that of US in  terms  of  pain  relief  and  overall  recovery  in  tennis elbow.

 

Conclusions

This  meta-analysis   reveals  that  ESWT  effectively  relieves  tennis   elbow   pain   at   1 month   and   3 months

follow-ups  compared to  US. The  subjective  evaluation of efficacy showed  that  ESWT  group  was superior  to US  group,  although  no  significant  difference  was  observed  in  the  elbow  function  scores  between  the  two groups.  Together,  these  results  lead  to  the  conclusion  that  ESWT  is  a  superior   adjuvant  therapy  for  tennis elbow  compared to US.

 

Additional files

Additional file 1: Data extraction excel.  (XLSX 22 kb)

Additional file 2: PRISMA 2009 flow diagram word version. (DOC 34 kb)

Additional file 3: PRISMA 2009 checklist. (DOC 62 kb)

 

 

Abbreviations

ESWT: Extracorporeal shock wave; LE: Lateral epicondylitis; RCTs: Randomized controlled trials; US: Ultrasonic;  VAS: Visual analogue scale/score

 

Acknowledgements

This study was funded by the National Major  R&D Program of China and supported by the Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology.

 

Authors’ contributions

CCY and YX contributed equally to this paper. CCY and YX designed and conceived the experiment. CCY performed the experiments. CCY and LC analyzed the data. CCY and YE wrote the manuscript. LH and ML operated the software. HX and AA carried out the investigation.  JL carried out the project administration. GL and BM participated in the sequence alignment and reviewed the manuscript. All of the authors listed have reviewed the manuscript. All authors read and approved the final manuscript.

 

Funding

This study was funded by the National Major  R&D Program of China (Item

NO.2018YFB1105705).

 

Availability of data  and materials

We state that the data will not be shared because all the raw data are present in the figures included in the article.

 

Ethics approval and consent to participate

Not applicable.

 

Consent  for publication

Not applicable.

 

Competing interests

The authors declare that they have no competing interests.

 

Author details

1Department of Orthopedics, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Jiefang Rd. 1277#, Wuhan

 

430022, Hubei, China. 2Department of Plastic Surgery, Brigham and Women’s

Hospital, Harvard Medical School, Boston 02152,  USA.

 

Received: 10 May 2019 Accepted: 24 July 2019

 

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