Extracorporeal shock wave therapy (ESWT) and radial pressure waves (RPW) May improve post-operative recovery following insertional Achilles tendon surgeries: a case-control pilot study

Abstract

Background

Insertional Achilles tendinopathy (IAT) is a common cause of posterior heel pain. While non-surgical management for IAT can result in satisfactory relief, a portion of patients may elect surgical intervention. Post-operative recovery can take on average 7 months to return to physical activity. Identifying treatments to improve post-operative healing is desirable to enhance recovery and return to full physical activity.

Materials/Methods

All cases from a single surgeon were reviewed from January 2015 to November 2021. Patients (intervention group) were identified who received perioperative extracorporeal focused shockwave (ESWT) and/or radial pressure wave (RPW) therapies and matched by age, sex and surgical technique. The treatment was performed prior to surgery (n = 6), post-operatively (n = 3), or both pre- and post-operatively (n = 3). The primary outcome measure was return to activity (RTA) defined as time from surgery to initiating their athletic activities. The secondary outcome measure was scores on the Roles and Maudsley (RM) obtained at last follow-up visit. Overall group differences were compared using two-sided Student’s T-test for RTA and Fisher exact test for RM, with P-value set at < 0.05.

Results

We reviewed all cases and identified 12 patients receiving ESWT/RPW who were matched to conventional treatment by age, sex and type of surgery. Seven males and five females were in each cohort, and the average age ± standard deviation of cohort were similar receiving ESWT/RPW and conventional treatment (47.2 ± 11.1 and 48.2 ± 10.6 year-old). Four patients had calcific tendon disease and eight had retrocalcaneal bursitis in each group, and the surgical approach was similar for each condition. The RTA was shorter in those receiving ESWT/RPW (5.5 ± 1.3 compared to 6.8 ± 1.3 months (CI 95%, -2.4 to -0.2, P =.02). The RM trended toward improved values for those receiving ESWT/RPW compared to conventional treatment(P =.07).

Conclusions

Findings from this study suggest that patients with IAT who underwent perioperative ESWT/RPW therapies may have experienced a faster RTA following surgery.

Introduction

Tendinopathy is a condition attributed to overuse, resulting in pain which can be debilitating and challenging to treat [1]. [2] This terminology for tendon injuries reflects the combination of pain, swelling and impaired performance resulting from chronic injury to tendon which may not be explained solely by inflammation [3]. Despite updates in terminology, the exact pathophysiology of tendinopathy is unknown and creates challenges in addressing underlying mechanisms for injury [4]. [5]

Insertional Achilles tendinopathy (IAT) is a common cause of posterior heel pain in sedentary and athletic individuals [6]. Compared to mid-portion Achilles tendinopathy, IAT is less common and causes pain, swelling, and impaired function at and around the area of insertion of the Achilles tendon and the posterior aspect of the calcaneus [6]. The current understanding of the pathophysiology of this condition is IAT is the result of combined mechanical stress, inflammation, dysregulation of the extracellular matrix and impaired vascularity [7].

The management of IAT includes a trial of non-operative treatment including exercise loading program [8]. In those who do not achieve satisfactory relief of symptoms, surgery can be performed using open, minimally invasively or endoscopic approach. Techniques may involve detaching the Achilles tendon from its insertion on the calcaneus, debridement, and reattachment of the tendon with anchors and augmentation with a flexor hallucis longus transfer [6]. However, post-operative recovery can be unpredictable for time to return to activity [4]. In a prior cohort of 166 patients receiving surgical management for a mix of calcific and non-calcific IAT, Saxena et al. reported that patients required an average of 7 months for RTA and functional outcomes were improved in male patients compared to females [9]. Recognizing the desire to facilitate faster and more predictable RTA for all patients, additional treatments may be used perioperatively to minimize both post-operative pain and complications and reduce recovery time.

Extracorporeal shockwave therapy is a nonsurgical treatment that has been recommended for the management of IAT [10]. While not fully understood, the primary mechanisms of action for shockwave is through mechanotransduction where radial pressure waves (RPW, previously referred to as shockwaves) and sound waves produced by focused shockwave (ESWT) have cellular effects on target tissues in focal zones resulting in tissue healing and pain relief [11]. Despite updated terminology, both therapies may be beneficial for management of orthopedic conditions [12]. One goal for tissue engineering is for the intervention to result in regenerative effects at the tendon level to resolve injury [4]. In tendons, shockwave may stimulate tenocyte proliferation and metabolism as well as collagen and protein synthesis [13]. [14] Shockwave may also increase glycosaminoglycan content and transforming growth factor-beta 1 [15]. Further, shockwave may promote neovascularization at the bone-tendon interface [16]. [17] Additional benefits of shockwave include reduction of pain through the stimulation of nociceptive c-fibers and disrupting aberrant pain pathways [18]. [19] Animal models also suggest the potential role of shockwave to improve joint mobility and promote biomineralization [20]. [21] As a result, the combined effects of shockwave on tissue and bone healing, pain modulation, and overall mobility may, in theory, benefit patients in the perioperative period.

Studies have described the effects of shockwave in non-surgical management of IAT. Early work by Rompe described improved outcomes with RPW added to exercise program [22]. However, other studies with RPW have not observed similar benefits [23–25] perhaps due to low energy settings reached during treatment [26]. [27] Other studies have described improved outcomes when combining use of ESWT and RPW [28]. [29] However, encouraging findings in clinical studies limited by shorter-term follow-up requires ongoing work to understand long-term outcomes [30]. Further, no studies have evaluated whether use of ESWT and/or RPW around time of surgery may enhance tissue healing. The purpose of this study was to evaluate the use of ESWT and RPW in the perioperative period following surgical management of IAT. Compared to a historical cohort, we hypothesized that patients receiving ESWT and RPW would see faster return to activity. Additionally, we explored whether patients receiving ESWT and RPW would observe improved functional outcomes measured by the Roles and Maudsley (RM).

Methods

All cases of insertional Achilles tendinopathy who underwent surgery with or without ESWT/RPW were reviewed from January 2015 to November 2021. The diagnosis was made by clinical exam with all patients completing pre-operative x-rays. Institutional review board approval was obtained, and study design was described as a pilot study due to use of available clinical data without randomization to receive ESWT/RPW. Inclusion criteria were patients undergoing surgery during the above time frame with medical records available that included demographic information with a minimum one-year follow-up from the index procedure. The primary outcome of return to activity (RTA) and secondary outcome of Roles and Maudsley (RM) were obtained from the chart and recorded on final clinical follow-up visit. Patients were excluded if this information was not complete. We identified patients who completed surgery by the same surgeon (A.S.) with perioperative ESWT and/or RPW therapies (some received either one or both types of treatment) and compared these cases to conventional treatment matched by age, sex, and diagnosis. Return to activity and functional outcomes in patients was compared with or without perioperative ESWT/RPW. Patients in the control group were matched by sex, diagnosis, activity level and age ± four years to patients in the intervention group. Data was entered into Excel™(Redmond, WA, USA) and two-sided Student’s T-test was used to evaluate differences between the two groups in RTA and Fisher’s Exact test were used for RM with P-value set at < 0.05 to define statistical significance.

In the clinic of A.S., shockwave treatment consisted of ESWT and RPW therapy for three sessions, with an energy level of 0.15 mJ/mm² for 2500 pulses, 6 Hz and/or 2.4 bars for 2500 pulses, 11 Hz respectively. These treatments were directed to the area of tenderness in the Achilles insertional region. The therapy protocol described for patients in clinic (A.S.) was not standardized to others who had perioperative treatment elsewhere. In some patients, only two sessions of either ESWT (Duolith, Storz Medical AG, Tägerwilen, CH) or RPW (OrthoPulse, Storz Medical AG, Tägerwilen, CH) were utilized either pre-operatively, post-operatively, or both at the energy levels described previously. We recommend completing at least two sessions of 2,500 pulses of ESWT to be rendered to the surgical site post-operatively at 0.15 mJ/mm² between two and eight weeks.

Surgery for IAT consisted of open approach removing exostoses with tenodesis of the Achilles tendon, using bioabsorbable suture anchors and calcific tendon debridement [9]. The same standardized post-operative protocol was used for all patients; non-weightbearing in a gravity equinus below knee cast for two weeks followed by a below knee boot with an 1/8” heel cushion for another two weeks. Ankle plantarflexion exercises along with inversion/eversion strengthening was initiated, with care taken to avoid going beyond neutral. Immobilization in a walking boot with a heel lift was maintained until 10 weeks post-operative. Formal physical therapy was also initiated at 10 weeks, avoiding stretching and eccentric loading until concentric heel raise was achieved [32]. Progression to running was evaluated, when possible, with an anti-gravity treadmill, using the threshold of 85% bodyweight to clear the patient for regular full bodyweight running [33].

Results

We reviewed all cases from a single surgeon (A.S.) but identified a younger average age of those receiving ESWT/RPW than conventional treatment. Therefore, we performed a smaller case-control pilot study resulting in twelve patients with surgery receiving ESWT/RPW were matched to individuals receiving conventional surgical management without ESWT/RPW (48.2 ± 10.6 and 47.2 ± 10.4 years, P =.82) with equal number of men (seven) and women (five) in each group. Four had calcific tendon disease and eight had retrocalcaneal bursitis in each group. The treatment was performed prior to surgery (n = 6), post-operatively (n = 3), or both pre- and post-operatively (n = 3). The RTA was significantly faster in surgery with ESWT/RPW (5.5 ± 1.3 months) compared to conventional treatment at 6.8 ± 1.3 months, (CI 95%, -2.4 to -0.2, P =.02). RM trended toward lower values in the intervention group compared to conventional treatment (Table 1, P =.07).

Table 1.

Matched subject demographics and outcomes

	Group 1 (Surgery)	Group 2 (Surgery + ESWT/RPW)	P-value
Subject number	12	12
Demographics
Age	47.2 ± 10.4	48.2 ± 10.6	0.82
Female	5	5
Male	7	7
Procedure Details
Surgical site
Right	7	5
Left	5	7
Outcome Measures
RTA	6.8 ± 1.3 months	5.3 ± 0.7 months	0.02
RM Scores			0.07
1	11	6
2	1	4
3	0	2

Discussion

The purpose of this study was to evaluate whether the addition of ESWT/RPW would improve post-operative management of IAT. The results of this study suggest that patients with IAT who completed ESWT/RPW had an associated faster RTA compared to conventional surgery without ESWT/PRW by an average of 1.7 months and improved outcomes using RM. The improved time for RTA may be important for athletes and have implications for other populations requiring clearance on return to work.

The mechanism for benefits of ESWT/RPW on shortening post-operative recovery cannot be determined by study design. Prior animal models have demonstrated improved vascularity at the tendon-bone interface [16], [17] and achieving faster tissue integration is important for advancing rehabilitation after surgery. While speculative, ESWT and RPW may help with soft tissue management of inflammation and pain and does not have concerns of side effects seen in other analgesics, such as opioid medications. In the post-operative course, focused ESWT consisted of electromagnetically generated sound waves directed at the tendon/bone interface. The RPW were delivered to soft tissues away from the bone-tendon interface and over myofascial sites of pain similar to protocols described in non-surgical management of AT [34]. Notably, prior animal work suggests RPW can result in indirect effects on calcified tissue [21]. The combined use of ESWT with RPW may address some of the prior limitations in high level randomized clinical trials that failed to detect benefits over 3–4 months following treatment with RPW for non-operative management [23]. [25] [35] The generation of RPW involves a pneumatic chamber that strikes an applicator head, with maximal energy generated at point of contact [36]. The resulting pressure waves can be painful when delivered over bone, and in authors collective experience, ESWT can generate more effective energy settings delivered to bone to address impairments at the tendon-bone interface.

There are limitations to the current study. This includes patients were not blinded or randomized. We cannot account for the decision of patients to elect to receive ESWT/RPW given the financial considerations as this treatment is typically not covered by insurance. To account for differences in age, we matched those receiving ESWT/RPW to surgery only cohort and saw similar RTA differences. As numbers were small, there was no adjustment for patients who had ESWT versus RPW, and no differences by presurgical vs. post-operative treatment. The cross-sectional study design and using available clinical patient reported outcomes limits understanding the mechanisms for how ESWT and/or RPW may improve surgical outcomes. We matched for primary condition but had fewer cases of calcific tendinopathy versus retrocalcaneal bursitis in each group and performed matching between the groups. The surgery was performed by a single surgeon which leads to a more standard surgical approach and post-operative management program. A prospective, randomized control trial can further clarify whether faster RTA, improved return to work time, and better RM scores can be achieved with ESWT/RPW post-operatively. Further, the Victorian Institute of Sports Assessment - Achilles (VISA-A) is commonly used to evaluate Achilles tendinopathy [28]; we elected to use RM given prior work in shockwave using this measure. As VISA-A is more commonly used, this measure could be used in future work. Improvement in RTA and RM may help overall psycho-social-medical health status for recovery in patients who have undergone surgery for insertional Achilles tendinopathy.

The management of IAT requires careful patient-specific consideration for selection to receive surgery. Notably, IAT has been proposed to be an indication for trial of shockwave [10] for non-surgical management and would be reasonable to trial prior to surgery. Based on the authors experiences and applying current findings to post-operative management, the authors propose a post-operative protocol for IAT following surgery with one treatment of ESWT 0.15 mJ/mm² for 2500 pulses 6 Hz within two to four weeks post-operatively directly on the surgical site. This can be combined with RPW 2.0-2.4 Bar, 2500 pulses at 8–15 Hz over tendon (away from surgical site to avoid skin dehiscence) and repeated for 1–2 weekly sessions. The addition of ESWT/RPW does not change the overall goals of post-operative management including progressive loading after immobilization. Results suggest use of ESWT/RPW may offer opportunities for faster return to activity.

Author contributions

AS was responsible for IRB approval, study methodology and design and statistical analysis and guarantees the data quality. AS, LB, LG, and AST participated in drafting, editing and approving the final manuscript.

Data availability

Data requests can be directed to corresponding author.

Declarations

Competing interests

Drs. Saxena and Gerdesmeyer receive equipment, honoraria, research and travel support from Storz Medical AG and Curamedix. Dr. Saxena has received support from Depuy Synthes. Dr. Tenforde has received equipment support from Storz Medical AG and Enovis. No funding for this study was received.

Institutional review board provided ethical approval and waiver of written informed consent. Limited deidentified data set inquiries can be requested from corresponding author. Authors declare no competing interests to this work. AS was responsible for IRB approval, study methodology and design and statistical analysis and guarantees the data quality. AS, LB, LG, and AST participated in drafting, editing and approving the final manuscript. We are grateful and acknowledge Logan Gaudette for his review of statistical methods and consultation. Drs. Saxena and Gerdesmeyer receive equipment, honoraria, research and travel support from Storz Medical AG and Curamedix. Dr. Saxena has received support from Depuy Synthes. No funding for this study was received.