Efficacy of Extracorporeal Shock Wave Therapy for Lower-Limb Tendinopathy: A Meta-analysis of Randomized Controlled Trials : American Journal of Physical Medicine & Rehabilitation

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Original Research Articles CME Article . 2018 Series . Number 9

Efficacy of Extracorporeal Shock Wave Therapy for Lower-Limb Tendinopathy

A Meta-analysis of Randomized Controlled Trials

Liao, Chun-De MSc; Tsauo, Jau-Yih PhD; Chen, Hung-Chou MD; Liou, Tsan-Hon MD, PhD

Author Information
American Journal of Physical Medicine & Rehabilitation 97(9):p 605-619, September 2018. | DOI: 10.1097/PHM.0000000000000925

Abstract

Lower-limb tendinopathy is a common musculoskeletal problem that develops due to sport-induced tendon injuries in athletes or overuse conditions in nonathletes,1 with an overall prevalence rate of approximately 12 per 1000 person-years.2 On the basis of its histological and pathological characteristics and clinical presentations,3 tendinopathy can be difficult to treat and might impair muscle and joint function,4,5 which can further exert negative effects on not only sports participation but also the ability to work and the quality of life.6–8 The most common practical tendinopathy-related problem encountered by patients with lower-limb tendinopathy is the pain-induced limitation in sports and related activities, particularly walking or running. Under such circumstances, the development of preventive interventions is crucial.

Extracorporeal shock wave therapy (ESWT) is widely used in clinical practice for managing orthopedic conditions.9 ESWT devices induce acoustic impulses that reduce the expression of matrix metalloproteinases and proinflammatory interleukins and promote the healing process by increasing the expression of growth factors as well as the release of anti-inflammatory cytokines, prefiguring a rationale for the application of ESWT to treat tendinopathies that failed to heal.10,11 On the basis of the delivery pathway that propagates acoustic energy through biological tissues, shock wave therapy can be divided into 2 types: focused shock wave (FoSW) and radial shock wave (RaSW).12 The differences in the application properties of FoSW and RaSW have been discussed,12–15 and each therapy should be considered as an independent treatment modality derived from multiple techniques that generate shock wave pulses.12,14,15 However, the difference in the therapeutic effects between the 2 shock wave modalities on lower-limb tendinopathies remains unclear.

The intensity at the focal point of the shock wave, measured as energy flux density (EFD) in mJ/mm2 per impulse, may influence the effects of ESWT.13 In clinical practice, ESWT applications can be divided into different EFD levels (ranging from 0.001 to 0.5 mJ/mm2).13,14 Accordingly, the total energy dose (TED), calculated as EFD × number of shock wave impulses, is considered a more appropriate reference for determining the shock wave dosage.13,16 Several studies have investigated the effectiveness of ESWT in lower-limb tendinopathies through systemic reviews or meta-analyses,13–15,17,18 most of which have involved study selections limited to a specific language. The application of language restrictions, wherein English-language only is the most common case, in study inclusion criteria may result in a high risk of bias (i.e., language bias) in this area of research where ESWT serves as an alternative to conservative medicine for musculoskeletal conditions.19 The overall pooled effects of different shock wave types and dosage levels on lower-limb tendinopathies require further investigation.

Increasing the number of treatment sessions may increase the risk of unsuccessful ESWT, and a considerably high dosage (HD) may lead to the potential onset of adverse events.20 Therefore, it is critical to optimize the efficiency of ESWT applications by identifying the effects of different shock wave types and dosages on treatment efficacy and safety. Through a systematic review and meta-analysis, this study determined the effect of different ESWT types and applied dosages (based on TED) on the treatment efficacy for lower-limb tendinopathy.

METHODS

Design

This study was approved by the Ethical Review Board of Taipei Medical University (protocol number: N201708010). This study conforms to all Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines21 and reports the required information accordingly (see Checklist, Supplemental Digital Content 1, https://links.lww.com/PHM/A588). The study involved a comprehensive electronic search of online sources. Original research articles on the clinical efficacy of ESWT for lower-limb tendinopathy with no restriction of publication year and language were aggregated and coded. The articles were obtained from the following online databases and search engines: Medline, PubMed, the Excerpta Medica dataBASE, the Cochrane Library Database, the Physiotherapy Evidence Database (PEDro), the China Knowledge Resource Integrated Database, and Google Scholar. Secondary sources were papers cited in the articles retrieved from the aforementioned sources and articles published in journals that were not available in the aforementioned databases. The search was restricted to published or in-press articles on human studies. If English titles were not provided in non-English articles, they were translated to English by using the translation software (Ginger Software, Inc.). Two reviewers (C-DL and T-HL) independently searched for articles, screened studies, and extracted data in a blinded manner. Any disagreement between the reviewers was resolved through consensus, with other team members (H-CC, J-YT) acting as arbiters.

Search Strategy

We used the following search terms to identify articles on lower-limb musculoskeletal disorders and associated conditions: “Achilles tendinopathy or peritendinopathy,” “tibialis tendinopathy or tendinosis,” “peroneal tendinopathy or tendinosis,” “medial tibial stress syndrome,” “patellar tendinopathy or peritendinopathy or apicitis,” “jumper’s knee,” “Osgood–Schlatter lesion,” “pes anserine tendinopathy,” “quadriceps tendinopathy or tendinosis,” “iliotibial tract syndrome,” “hamstring syndrome,” “gluteal tendinopathy,” and “greater trochanteric pain syndrome.” Furthermore, search terms used for ESWT were “shock wave therapy,” “extracorporeal shock wave therapy,” and “ESWT.”

Study Selection Criteria

Articles were included if they fulfilled the following criteria: (1) the trial design was a randomized controlled trial (RCT); (2) the control groups received a placebo through a sham shock wave application or underwent active treatment (e.g., exercise, injections, or surgery); (3) the primary outcome included pain, which was measured using a quantifiable scale, such as a visual analog scale (VAS), and the ratio of successful treatment was measured using a rank scale, such as the Roles and Maudsley score22; (4) the secondary outcomes included physical function or disability; and (5) the following application parameters could be extracted: wave characteristics, EFD, number of shock impulses, number and duration of treatment sessions, and frequency of treatment.

Articles were excluded if any of the following exclusion criteria were fulfilled: (1) the article reported a study that used an animal model, (2) the article was a case report or case series, and (3) the study was a prospectively designed trial without a comparison group.

Data Extraction

We developed a data extraction sheet for the included studies and refined it.14,17 An author (C-DL) extracted relevant data from the included studies, and another author (H-CC) reviewed the extracted data. Any disagreement between the 2 authors was resolved through consensus. A third author (T-HL) was consulted if the disagreement persisted.

Outcome Measures

The primary outcomes, namely, pain intensity and the ratio of successful treatment, were calculated as standardized mean differences (SMDs) and odds ratios between the placebo and active control groups, respectively. Secondary outcomes, namely, physical function and disability, were also calculated as SMDs between the placebo and active control groups.

Assessment of Bias Risk and Methodological Quality

The PEDro classification scale was used to assess the bias risk in RCTs.23 The methodological quality of all the included studies was independently assessed by 2 researchers (C-DL and H-CC) in accordance with the PEDro classification scale. Any disagreement between the 2 researchers was resolved through consensus. A third researcher (T-HL) was consulted if the disagreement could not be resolved.

The PEDro classification scale, a valid measure of the methodological quality of clinical trials,24 contains 11 items (including the item “Eligibility Criteria,” which is not used to calculate the total score). Each item is scored as 1 if present or 0 if absent, yielding a total score ranging from 0 to 10 through the summation of all 10 item scores. The methodological quality of the included studies was rated on the basis of the PEDro score as follows: 9–10 (excellent), 6–8 (good), 4–5 (fair), and <4 (poor).

We also examined adverse events when reported; however, they were not specified a priori. The follow-up (FU) duration was assessed and defined as immediate (1 month), short term (>1 month, 3 months), medium term (>3 months, 6 months), and long term (>6 months).25

Statistical Analysis

We computed effect sizes in each study for the primary and secondary outcome measures separately after ESWT. One of the primary outcomes, pain intensity, was defined as pooled estimates of the mean difference in changes between the mean of the treatment and placebo (or active control) groups, weighted by the inverse of the standard deviation (SD) for each study that was included. If the exact variance of paired differences was not derivable, it was approximated by assuming a correlation coefficient of 0.8 between the baseline and post-treatment pain scores.26,27 If the data were reported as the median (range), they were recalculated algebraically from the trial data for imputing the sample mean and SD.28 The odds ratio with a 95% confidence interval (CI) was evaluated for dichotomous outcomes (i.e., the ratio of successful treatment). For the secondary outcomes of functional mobility and disability, the effect size was defined as the SMD, which was a combined outcome measurement without units.

Fixed effects or random effects models were used, depending on the presence of heterogeneity. Statistical heterogeneity was assessed using the I2 statistics for significance (P < 0.05) and χ2 and F values of >50%.29 The fixed effects model was used when significant heterogeneity was absent (P > 0.05), whereas the random effects model was used when the heterogeneity was significant (P < 0.05).

A subgroup analysis was performed on the basis of the shock wave type (i.e., FoSW and RaSW), application dosage, and comparison type (i.e., placebo, noninvasive, or invasive active control) in the included studies. The shock wave dosage level was identified by determining a reference of TED.13,16 A cutoff value of 0.12 mJ/mm2 for EFD has been used in clinical applications for identifying different energy levels,30–33 and a cutoff value of 2000 impulses per treatment session for the number of shock wave impulses has been recommended for ESWT applications34; accordingly, an applied TED of ≤240 mJ/mm2 was considered as a low-dosage (LD) shock wave, and a TED of >240 mJ/mm2 was considered as an HD shock wave in this study.

Potential publication bias was investigated through the visual inspection of a funnel plot for exploring possible reporting bias,35 and Egger’s regression asymmetry test36 was conducted using the SPSS statistical software (Version 17.0; IBM, Armonk, NY). A P value of < 0.05 was considered statistically significant. All analyses were conducted using RevMan 5.3 (The Nordic Cochrane Center, Copenhagen, Denmark).

RESULTS

Trial Flow

Figure 1 presents a flowchart of the selection process. The final sample comprised 29 RCTs with a placebo or active control group37–65 published between 2003 and 2017. A sample of 1865 patients with an overall mean (SD) age of 38.2 (11.2) yrs was enrolled in the 29 included RCTs. Of all the patients, 873 received ESWT and 992 received a placebo application or other active treatments.

F1
FIGURE 1:
Flowchart of study selection. EMBASE, Excerpta Medica dataBASE; CNKI, China Knowledge Resource Integrated Database.

Study Characteristics

Table 1 summarizes the demographic data and study characteristics of the included trials. All patients enrolled in the included trials experienced symptoms for at least 3 months. Regarding the diagnosis, 5 RCTs employed ESWT for patients with hip tendinopathy,44,51,56,58,65 13 RCTs used ESWT for knee tendinopathy,37–41,43,52–55,57,60,63 10 RCTs treated ankle musculoskeletal pain,45–50,59,61,62,64 and 1 RCT enrolled patients with medial tibial stress syndrome,42 which is associated with tibialis posterior and tibialis anterior tendinopathy.66

T1
TABLE 1:
Summary of included study characteristics

Table 2 summarizes the applied parameters of ESWT and treatment protocols. In total, 12 RCTs used FoSW, among which 9 RCTs used HD-FoSW37,42,45,47,52,54,55,57,59 and 3 used LD-FoSW.43,46,53 Among the 17 RCTs that used RaSW, 8 applied HD-RaSW39–41,44,56,58,60,65 and 9 applied LD-RaSW.38,48–51,61–64 All the included RCTs applied an ESWT protocol that comprised 3 to 36 treatment sessions with an intersession interval of 2 days to 1 month, apart from 1 RCT that administered only a single treatment session.55 No local anesthesia at the treatment site was administered during application in all the included RCTs.

T2
TABLE 2:
Type of wave characteristics, source of stimulation energy, and application parameters

Risk of Bias in the Included Studies

The individual scores of methodological quality are listed in Table 3. The inter-rater reliability associated with the cumulative PEDro score was acceptable, with an interclass correlation of 0.95 (95% CI, 0.92–0.98; P < 0.001). The methodological quality was classified as good or excellent for all the included RCTs with a median (range) PEDro score of 8 (6–9).

T3
TABLE 3:
Summary of methodological quality based on the PEDro classification scalea

Success or Improvement Rates

In total, 23 RCTs reported categorical data for pain and general outcomes (Table 1).37,39,41,43,44,46,48–60,62–65

General ESWT yielded a higher treatment success rate (TSR) than did the placebo or active control as assessed at the immediate FU by using a random effects model (OR = 2.39, P = 0.02; I2 = 55%) as well as at the short-term (OR = 2.82, P = 0.009; I2 = 67%) and long-term (OR = 3.18, P = 0.04; I2 = 78%) FU (Fig. 2A). The details of each comparison are presented in Supplemental Figure 1 (Supplemental Digital Content 2, https://links.lww.com/PHM/A589).

F2
FIGURE 2:
Forest plot of success rates of extracorporeal shock wave therapy during follow-up periods. A, Subgroup analysis for shock wave types and dosage levels. B, Subgroup analysis for comparison types. IV, inverse variance; Fixed, fixed effects model; Random, random effects model; non-ESWT, no application of shock wave treatment; MSE, muscle strength training; TEA, traditional electro-acupuncture; Cons, conservative treatment; PRP, platelet-rich plasma injection; HA, hyaluronan injection; ET, eccentric training; MT, manual therapy; HT, home training; ST, stretching exercise; MWD, microwave diathermy; USD, ultrasound diathermy.

A subgroup analysis based on the different shockwave types and dosage levels revealed that HD-RaSW yielded significantly higher ORs for TSR at short-term (OR = 2.44, P = 0.03; I2 = 0%) and long-term (OR = 7.49, P < 0.0001; I2 = 44%) FU, and LD-RaSW yielded significantly higher ORs for TSR at short-term (OR = 2.82, P = 0.009; I2 = 67%) and medium-term (OR = 3.27, P < 0.00001; I2 = 0%) FU (Fig. 2A). A combined effect of HD-RaSW and LD-RaSW on TSR showed a significant OR favoring ESWT at the short-, medium-, and long-term FUs (Supplemental Figure 2, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). HD-FoSW or LD-FoSW did not demonstrate a significant OR favoring ESWT at all FU periods, except that HD-FoSW used by 1 RCT57 yielded a significantly higher OR for TSR at the immediate FU (OR = 3.82, P = 0.01). A combined effect of HD-FoSW and LD-FoSW on TSR showed no significant OR favoring ESWT at each FU (Supplemental Figure 3, Supplemental Digital Content 2, https://links.lww.com/PHM/A589).

Another subgroup analysis based on the different interventions in the control groups revealed that general ESWT yielded significantly higher ORs for TSR than did the noninvasive active control at the immediate FU with a pooling OR of 2.41 (P = 0.002; I2 = 52%) as well as at the short-term (OR = 2.70, P < 0.0001; I2 = 73%), medium-term (OR = 2.26, P = 0.0008; I2 = 43%), and long-term (OR = 3.81, P = 0.05; I2 = 76%) FU, irrespective of the shock wave type and application dosage (Fig. 2B and Supplemental Figure 4, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). In addition, the RaSW subgroup exhibited a significant OR favoring ESWT at the immediate (OR = 2.77, P = 0.004; I2 = 57%), short-term (OR = 2.91, P = 0.0002; I2 = 65%), and medium-term (OR = 2.68, P = 0.0003; I2 = 54%) FU, whereas the FoSW subgroup exhibited a significant OR favoring ESWT at the long-term FU (OR = 3.35, P = 0.05; I2 = 6%). Compared with the placebo control, a significant effect of ESWT on TSR was observed at the immediate FU (OR = 3.82, P = 0.01), as reported by one RCT,57 as well as at the short-term (OR = 4.73, P = 0.007; I2 = 54%) and medium-term (OR = 4.54, P = 0.01; I2 = 0%) FU (Fig. 2B and Supplemental Figure 5, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). The pain relief provided by TSR did not differ between ESWT and invasive active control at all FU time points (Fig. 2B and Supplemental Figure 6, Supplemental Digital Content 2, https://links.lww.com/PHM/A589).

Effect on Pain Relief

Pain severity was reported using a VAS by 22 RCTs37–41,43–47,52–55,57–61,63–65 and an 11-point numerical rating scale by 6 RCTs.42,48–51,56 All pain severity data were transformed to 0 to 100 mm of continuous data. The data analysis of the transformed pain scores revealed that pain significantly decreased immediately after general ESWT with an overall pooled SMD of −1.41 (P < 0.00001; I2 = 95%) compared with the control groups, irrespective of the shock wave type, application dosage, and control intervention type (Fig. 3A and Supplemental Figure 7, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). Similar results were observed at the short-, medium-, and long-term FU.

F3
FIGURE 3:
Forest plot of extracorporeal shock wave therapy for pain score reduction during follow-up periods. A, Subgroup analysis for shock wave type and dosage level. B, Subgroup analysis for comparison types. IV, inverse variance; Random, random effects model; non-ESWT, no application of shock wave treatment; MSE, muscle strength training; TEA, traditional electro-acupuncture; Cons, conservative treatment; PRP, platelet-rich plasma injection; HA, hyaluronan injection; ET, eccentric training; MT, manual therapy; HT, home training; ST, stretching exercise; CS, local corticosteroid injection; MWD, microwave diathermy; USD, ultrasound diathermy.

A subgroup analysis of shock wave types and dosage levels revealed that HD-FoSW exerted significant effects on pain reduction at all FU periods except the long-term FU; however, LD-FoSW did not exert significant effects on pain reduction (Fig. 3A). A combined effect of both TED levels demonstrated a significant SMD favoring FoSW at the immediate (SMD = −1.87, P = 0.01; I2 = 95%), short-term (SMD = −1.13, P = 0.03; I2 = 95%), and medium-term (SMD = −1.74, P = 0.03; I2 = 97%) FU (Supplemental Figure 8, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). In addition, HD-RaSW and LD-RaSW individually as well as a combination of HD-RaSW and LD-RaSW exhibited significant SMDs favoring ESWT at all FU periods (Fig. 3A and Supplemental Figure 9, Supplemental Digital Content 2, https://links.lww.com/PHM/A589).

The subgroup analysis based on control comparisons is presented in Figure 3B and Supplemental Figures 10 to 12 (Supplemental Digital Content 2, https://links.lww.com/PHM/A589). Compared with the noninvasive active control, significant treatment effects favoring ESWT were observed at the immediate FU (SMD = −1.46, P < 0.0001; I2 = 94%) as well as at all other FUs; in the same subgroup, a separate pooling of the treatment effects of the 2 shock wave types showed a similar effect on pain reduction between FoSW and RaSW. In addition, a significant SMD favoring general ESWT compared with placebo control was observed at each FU, whereas no difference in the treatment effect was observed between the ESWT and invasive active control at all FU periods.

Effect on Functional Outcome

In total, 21 RCTs reported functional and general outcomes (Table 1).37,39–41,43–50,52–55,57,58,62,63,65 The combined analysis revealed the significant effect of general ESWT, with an SMD of 2.59 (P < 0.00001; I2 = 97%) favoring ESWT at the immediate FU as well as all other FU time points (Fig. 4A and Supplemental Figure 13, Supplemental Digital Content 2, https://links.lww.com/PHM/A589).

F4
FIGURE 4:
Forest plot of extracorporeal shock wave therapy for function recovery during follow-up periods. A, Subgroup analysis for shock wave type and dosage level. B, Subgroup analysis for comparison types. IV, inverse variance; Random, random effects model; non-ESWT, no application of shock wave treatment; Cons, conservative treatment; ET, eccentric training; USD, ultrasound diathermy; PRP, platelet-rich plasma injection; MSE, muscle strength training; ST, stretching exercise; HA, hyaluronan injection.

A subgroup analysis of the shock wave types and dosage levels revealed that HD-FoSW, but not LD-FoSW, exhibited higher functional gains than did the control comparisons at all FU time points, except at the long-term FU (Fig. 4A). A combined effect of both TED levels indicated significant SMDs favoring FoSW at the immediate, medium-term, and short-term FUs (Supplemental Figure 14, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). Both HD-RaSW and LD-RaSW had significant effects on functional improvement at each FU, except for LD-RaSW at the short-term FU; a combined effect of both TED levels exhibited significant SMDs favoring RaSW at each FU (Fig. 4A and Supplemental Figure 15, Supplemental Digital Content 2, https://links.lww.com/PHM/A589).

Another subgroup analysis for different control group types showed that both FoSW and RaSW exerted favorable effects on functional outcomes compared with the noninvasive active control at the immediate FU with a combined SMD of 2.95 (P < 0.0001; I2 = 96%) as well as at the long-term FU (Fig. 4B and Supplemental Figure 16, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). Compared with the placebo control, ESWT had significant effects on functional outcomes at all FU time points (Fig. 4B and Supplemental Figure 17, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). No difference between the ESWT and invasive active control was identified at each FU (Fig. 4B and Supplemental Figure 18, Supplemental Digital Content 2, https://links.lww.com/PHM/A589).

Side Effects of ESWT

No clinically relevant adverse events, side effects, or serious complications (e.g., hematomas, tendon rupture, and other abnormal musculoskeletal events) were reported after ESWT by all included RCTs (Supplemental Table 1, Supplemental Digital Content 3, https://links.lww.com/PHM/A590). Of the 9 RaSW RCTs that reported adverse events,39,48–51,56,62–64 6 reported skin irritations (i.e., transient reddening or bruising) with 109 events,48–51,56,64 1 reported pain during or after ESWT applications with 13 events,51 and 1 reported other complications, such as swelling, with 3 events.51 Of the 8 FoSW RCTs that reported adverse events,37,42,45,46,53–55,57 1 reported skin irritation with 23 events,54 2 reported pain during or after ESWT applications with 23 events,45,46 2 reported other complications, such as transient numbness around the treated site (1 event)55 or complications that were not related to the device or procedure (5 events),46 and 2 reported that FoSW treatment applications were well tolerated by all patients.53,57

Publication Bias

Visual inspection of the funnel plots of pain reduction at all FU periods did not reveal any substantial asymmetry (Supplemental Figure 19, Supplemental Digital Content 2, https://links.lww.com/PHM/A589). In addition, Egger’s linear regression test did not indicate any evidence of reporting bias among the studies (t = 1.75; P = 0.09).

DISCUSSION

In this study, a comprehensive search of previous RCTs that investigated the clinical efficacy of ESWT in patients with lower-limb tendinopathy was conducted. Compared with previous meta-analyses on the efficacy of ESWT,13–15,17,18,33,67 the current meta-analysis focused on tendinopathies that impair the lower-limb muscle function and on pooled comprehensive data to distinguish between the clinical efficacies of different shock wave types, applied dosage levels in TED, and intervention types in the control groups at the immediate, short-term, medium-term, and long-term FU periods. The differences in the occurrence rate of adverse events between shock wave types and dosage levels were also evaluated. This study provided a significant evidence of the safety and efficacy of general ESWT for treating pain and function deficits associated with lower-limb tendinopathy during all FU periods, irrespective of the shock wave type, dosage level, and control group comparison type. While considering shockwave types together with dosage levels, HD-FoSW exerted superior effects on pain reduction and functional outcomes than did LD-FoSW at all FU periods, whereas no difference in treatment efficacy was observed between HD-RaSW and LD-RaSW.

Several systemic reviews that have investigated the effectiveness of ESWT for lower-limb tendinopathies13,17,18 did not report the overall pooled effects of general ESWT, and the difference in efficacy between different shock wave types or dosage levels remains unclear. Our meta-analysis provides evidence of the combined effects of ESWT based on shock wave types and dosage levels in TED; the results revealed that HD-FoSW, HD-RaSW, and LD-RaSW sequentially have superior effects on overall clinical outcomes in common lower-limb tendinopathies. In addition, the results of this study showed that HD-FoSW, but not LD-FoSW, exhibited a significant treatment efficacy, whereas the combined effects of both resulted in either no effects on TSR or attenuated effects on pain reduction and function. This may indicate that different dosage levels can be independently considered rather than pooling them as a whole to examine the treatment efficacy of ESWT. Furthermore, the present study also demonstrated that ESWT yielded superior results compared with traditional conservative treatment and that ESWT is an effective noninvasive alternative to injection or surgery for treating lower-limb tendinopathy.

Studies comparing the effects of different shock wave types and intensity levels have reported inconsistent results related to the superiority of approaches for treating plantar fasciitis,13,15,67–69 Achilles tendinopathy,13,15 or patellar tendinopathy.70 Some studies have compared shock wave types without distinguishing the applied intensity, whereas others have identified the intensity level using EFD.15 Shock wave energy can be divided into different levels using various cutoff values of EFD,15,32,71 which has been widely used in clinical practice.14,15 The applied dosage in terms of TED is another application parameter for determining the clinical efficacy of ESWT.13 In addition, the results of a previous study indicated that an effectively applied FoSW had a significantly higher EFD than did RaSW, whereas no significant difference in TED was observed between the 2 ESWT types14; this finding implies that using only EFD to classify intensity levels may result in an underestimation of the total applied energy; therefore, using TED may be the optimal choice for comparing different shock wave types. Furthermore, using TED as a comparator facilitates the integration of EFD and the number of impulses, which vary among different application protocols. Therefore, we considered both shock wave types and dosage levels in TED rather than EFD to evaluate the efficacy of ESWT.

In this study, ESWT exerted immediate, short-term, and medium-term effects on functional recovery, which was concurrent with pain reduction at each FU period. Hip, knee, or Achilles tendinopathy resulted in a considerable functional deficit and disability in untrained individuals and trained athletes.72–74 The decreased physical activity or functional limitation is mainly a result of tendon injury. Therefore, pain relief in the early stage of the tendon healing process allows increased physical mobility, which provides mechanical loading and further enhances the healing process in a tendon with chronic tendinopathy.75 A combined analysis of these factors may explain the concurrent pain relief and functional recovery at all FU periods in this study.

In a systematic review, Schmitz et al.14 compared the intensity and dosage levels between FoSW and RaSW studies and reported a significant positive outcome in some cases for both upper-limb and lower-limb tendinopathies; the results presented no scientific evidence in favor of either FoSW or RaSW with respect to a positive clinical outcome. A similar network meta-analysis was conducted for upper-limb tendinopathy only, and the results revealed the superiority of RaSW over HD-FoSW,33 which is contrary to the findings of this study that focused on lower-limb tendinopathy. Compared with the upper-limb, the musculoskeletal system of the lower-limb plays a prominent role in weight-bearing activities such as walking and standing; therefore, the recovery nature or pattern might be different between upper-limb and lower-limb tendinopathy. Accordingly, the mechanism mediating treatment efficacy may be potentially different between upper-limb and lower-limb tendinopathy, which may explain the discrepancy among the results of Schmitz, Wu, and our current meta-analysis. Thus, the efficacy of ESWT in upper-limb and lower-limb tendinopathy should be independently computed rather than pooling both conditions together.

Our study had some limitations. First, only lower-limb tendinopathy was included, and the results may not be generalizable to other prevalent orthopedic disorders such as osteoarthritis and plantar fasciitis. Second, although the data did not suggest a substantial publication bias and demonstrated a significant effect on pain reduction from general ESWT, heterogeneity among the included studies was noted. The high heterogeneity may be due to the varying designs and application protocols of the included studies. Third, other application parameters, such as the rate of shocks (impulses per second, Hz), number of treatments, and interval between treatments, which may interfere with the therapeutic response9,20 were not considered for comparisons in this current study. Finally, other confounding factors, such as age, sex, participation in sports, physical activity level, work type, and rate of return to sports and work, which may have contributed to treatment efficacy, were not computed for TSR.

CONCLUSIONS

This study demonstrated that general ESWT application exerted beneficial effects on pain and functional outcomes for lower-limb tendinopathy, particularly for common tendinopathies and soft tissue disorders. In addition, this study provided evidence that HD-FoSW applications are generally superior to LD-FoSW applications, although a similar efficacy was observed between HD-RaSW and LD-RaSW for managing lower-limb tendinopathy. Furthermore, ESWT can be effectively performed with few minor side effects. Our findings can facilitate the decision making of clinicians regarding alternatives to the conventional management of lower-limb tendinopathy to determine the optimal treatment strategy.

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Keywords:

Extracorporeal Shock Wave Therapy; Radial Shock Wave; Focused Shock Wave; Tendinopathy; Lower Limb; Function Outcome

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