Research Review by Dr. Shawn Thistle©

Date:

Jan. 2008

Study Title:

Eccentric loading compared with Shock Wave Treatment for chronic insertional Achilles tendinopathy: A randomized controlled trial

Authors:

Rompe JD, Furia J & Maffulli N
Authors’ Affiliations: OrthoTrauma Clinic, Gruenstadt, Germany

Publication Information:

Journal of Bone & Joint Surgery (America) 2008; 90: 52-61.

Summary:

Achilles tendon injuries can be debilitating, and occur frequently in competitive and recreational athletes, particularly those involved in sports involving running and jumping. Recently, the term “tendinopathy” has been introduced to describe classic tendon pathology that was once commonly referred to as “tendonitis”. This new terminology reflects the discovery that overuse injuries to tendons do not involve as much of an inflammatory component as once thought – hence the replacement of the suffix “itis”. Rather, fibrotic connective tissue changes resulting from failed healing of the extracellular matrix lead to pain and functional impairment.

This pathology forms the basis of most of these injuries. The terms “tendinopathy” and “tendinosis” were born out of this research, and can be applied to many tendons in the body, including the Achilles tendon, the focus of this review. It is worth noting that Dr. Nicola Maffulli, one of the authors of this study, was a leader in the initial research that led to this new line of thinking.

Achilles tendinopathy is a common affliction, and is classified into one of two categories: insertional (bone-tendon junction) and non-insertional. Despite being a common condition, the literature to date has failed to provide a clear recommendation for ideal management. A previous Cochrane Review1 concluded that there was insufficient evidence from randomized, controlled trials to identify which method of treatment is most appropriate for Achilles tendinopathy (note the use of “tendonitis” in the title of this Cochrane Review referenced below – which was completed a year or two before this new line of research emerged). In this review, it was noted that not a single trial specifically investigated treatment for insertional Achilles tendinopathy.

There are numerous studies demonstrating that eccentric (ECC) training can be an effective treatment for Achilles tendinopathy – although distinctions have not always been made when selecting subjects between those with insertional and non-insertional tendinopathy. It should be noted that this body of evidence lacks a substantial, well-designed trial demonstrating superiority of ECC training over other treatments, but remains promising nonetheless.

There is also a lack of high-quality studies regarding the application of Shock Wave Therapy (SWT) for Achilles tendinopathy, despite industry claims of its effectiveness, and some anecdotal evidence. SWT is thought to stimulate soft tissue healing, enhance angiogenesis, and inhibit pain receptors.

This study compared the efficacy of two protocols - ECC calf strengthening and repetitive low energy SWT – for the treatment of chronic insertional Achilles tendinopathy. Conducted in a primary care setting, this randomized controlled trial recruited patients consulting one of three orthopedic physicians for Achilles tendon complaints. All patients included in the study had to receive a diagnosis of chronic insertional Achilles tendinopathy (defined as localized pain over the distal part of the Achilles tendon at its calcaneal insertion, with localized tenderness and a reduced activity level).

Symptoms had to be present for at least 6 months, and have not responded to non-surgical management, including at least one injection of anesthetic/corticosteroid, prescription NSAIDs, and physiotherapy with or without prescription of a heel lift. Ultrasound examination was performed on all subjects to exclude those with thickening of the tendon or irregular tendon structure and/or fiber orientation in the midportion of the tendon. Patients were also excluded if they had retrocalcaneal fluid on ultrasound examination (which would indicate isolated or concomitant bursitis).

Patients also underwent radiographic evaluation to exclude patients with a Haglund deformity (osseous prominence on the posterosuperior and lateral aspect of the calcaneus with a Fowler-Philip angle of > 75°). Patients were also excluded if they had:
  • received a peritendinous injection within the previous 4 weeks
  • ankle arthritis
  • radiculopathy
  • prior surgery to the ankle or Achilles tendon
  • congenital or acquired deformity of the foot or ankle
  • dislocation or fracture in the area in the preceding 2 months
  • systemic or neurological conditions
Fifty patients were randomized into 2 treatment groups (see below). All patients were asked to avoid pain-provoking activities for the duration of the 12-week study period. Both walking and cycling were allowed provided they could be performed with no more than “mild discomfort”. Light jogging could be introduced at 6 weeks, provided it was on a flat surface and did not cause pain. If necessary, paracetamol (2000-4000mg/d) or naproxen (1000mg/d) was permitted in each group. At 4 months, all subjects had the option to cross-over treatment groups if they felt they had not adequately recovered.

Treatment Groups
  1. Eccentric Training (n=25): patients stood on a step with the knee straight and all bodyweight on the forefoot, raising the bodyweight with both feet (ankles into plantar flexion) and reversing the motion on only the injured leg (ankle into dorsiflexion). Bodyweight alone was used at first, and weight was added via a weighted back pack as tolerated (5 Kg increments). Patients only loaded the involved tendon eccentrically, and performed 3 sets of 15 repetitions twice per day. Patients were advised to perform the exercises through mild or moderate pain (according to previous literature), stopping only if the pain became severe.
  2. Shock Wave Therapy (n=25): a radial shock wave device (EMS Swiss Dolor-Clast, Munich, Germany) was used to deliver shock wave input through standard ultrasound gel. SWT was performed 3 times, spaced 1 week apart. At each session, 2000 pulses were delivered with a pressure of 2.5 bars (equal to an energy flux density of 0.12 mJ/mm2) – treatment frequency was 8 pulses per second. The area of maximal tenderness was treated in a circumferential pattern with no anesthetic.
Outcomes were measured at baseline, 4 months (and 15 months for those that crossed-over), were observer-blinded, and included: VISA-A score (Victorian Institute of Sport Assessment – Achilles), general assessment using a 6-point Likert scale, pain assessment using an 11-point numeric pain rating and pressure algometer readings.

Pertinent Results:

  • VISA-A scores were similar at baseline, and both groups showed similar significant improvements at 4 months [p = 0.005] (this was the primary outcome measure)
  • however, 64% of patients (16/25) in the SWT group reported being “completely recovered” or “much improved” on the Likert scale at 4 months, versus only 28% (7/25) in the ECC group
  • the SWT group showed greater improvement in pain level (p = 0.004), and pain-pressure threshold (p = 0.002) compared to the ECC group (no significant baseline differences existed in these two measures)
  • 18 patients in the ECC group crossed-over to SWT treatment at four months – 13 of these 18 reported successful outcomes with SWT 15 months from baseline
  • 8 patients in the SWT group crossed-over to ECC – only 2 of these 8 reported successful outcomes with ECC 15 months from baseline, and 1 patient ended up having surgery
  • 21/25 patients in the ECC group reported performing the exercises twice daily in their logs, indicating good adherence
  • no serious complications were reported in either group – in the SWT group, transient skin reddening occurred in all patients after treatment, but no bruising occurred

Conclusions & Practical Application:

This study attempted to address a recent challenge to the oft-cited Scandanavian research which previously indicated that ECC training is effective for treating Achilles tendinopathy – that being the discrepancy in its efficacy for treating insertional versus non-insertional tendinopathy. A recent study2 demonstrated much higher success of ECC training for treating non-insertional Achilles tendinopathy (89% success) versus insertional tendinopathy (only 32% success).

This study was one of the first to focus solely on insertional Achilles tendinopathy and provided further evidence that perhaps ECC training is better suited to non-insertional cases. Further, it provided preliminary evidence that SWT may be an effective treatment option for insertional cases. Further research is required to replicate these results for SWT, and perhaps identify the most effective treatment parameters.

The results of this study should be viewed with the following study limitations in mind:
  • there was no control group
  • treatment was not blinded (although outcomes assessment was)
  • no reliable long-term follow-up data

Additional References:

  1. McLaughlin GJ, Handoll HH. Interventions for treating acute and chronic Achilles tendonitis. Cochrane Database Syst Rev 2001; 2: CD000232.
  2. Fahlstrom M et al. Chronic Achilles tendon pain treated with eccentric calf muscle training. Knee Surg Sports Traumatol Arthrosc 2003; 11: 327-333.