Chronic Achilles tendinopathy

Chronic mid-portion Achilles tendinopathy is a degenerative condition affecting both recreational and elite athletes. However, sedentary individuals who commence regular, unaccustomed activity can also be affected. 

Figure 1. Longitudinal colour Doppler ultrasound of the Achilles tendon showing both hypoechoic regions and areas of neovascularisation(click to enlarge)

Clinical features

Presenting features include a ‘burning’ pain or stiffness localised 2-6cm above the insertion of the Achilles tendon to the calcaneus. This sensation is invariably exertional in nature. A detailed history may include a sudden increase in levels of physical activity or an increase in training intensity that precedes the onset of symptoms. Often, the intensity of training performed is excessive compared to baseline levels of fitness. 

In the case of the elite athlete, there may be a history of over-training without allowance for recovery of the tendon from recurrent micro-trauma. Use of poorly fitted or worn footwear and hill training are additional risk factors. Poor biomechanical function can put individuals at risk, particularly tight gastrocnemius and soleus muscles and the resultant excessive pronation. 

Chronic Achilles tendinopathy, as distinct from acute tendonitis, is defined when pain persists greater than three months. Lifetime incidence in competitive athletes is estimated to be 24%.¹ Clinical examination may reveal an enlarged and painful tendon. Peri-tendinous pain might indicate an alternative pathology, eg. ankle pathology. 

Complete rupture of the Achilles tendon should always be excluded using the Thompson-Simmonds’ calf-squeeze test.² Dorsiflexion and plantar flexion may elicit crepitus over the tendon. Pain can be reproduced by applying a loading force across the tendon, eg. single-leg heel raise.

Diagnosis and imaging

Achilles tendinopathy is a clinical diagnosis re-enforced by radiological imaging. Imaging should not be relied upon in isolation as neither T2-weighted MRI nor high quality ultrasound are highly specific.³

Although clinical features (ie. pain, tenderness, swelling, impaired function) may imply inflammation as an underlying process, histology does not demonstrate inflammatory cells but rather microfibre collagen disarray, increased ground substance, partial macroscopic tears and surrounding oedema. 

During surgical exploration, hyper-vascularity is present without evidence of effective healing. In fact, abnormal neovascularisation can be observed on ultrasound. Hypoechoic areas of the tendon signify regions of fibre disarray. Treatment options can be classified into conservative, injectable therapies and surgical interventions.

Conservative management

Eccentric exercise

Eccentric exercise involves focusing on the elongation phase of muscle action. Alfredson’s heel drop programme was first described in 1998.⁴ It consists of a 12-week programme incorporating two types of heel drops (the gastrocnemius and soleus drops). Although time-consuming and lengthy, successful completion of Alfredson’s protocol improves symptom scores at one year and is sustained at five years post-diagnosis.^5,6 Radiological findings also improve although the correlation between radiological improvement and clinical improvement remains questionable.⁷

The benefit of adding a night-time splint is controversial and studies have produced conflicting evidence.^8,9 Disadvantages of eccentric exercise as a mainstay of treatment include the difficulty in ensuring patient compliance with the regularity of the exercise programme. This is particularly true as exercises are likely to be painful during the initial phases of the programme. Also, the duration of treatment is also problematic, particularly for high-end athletes wishing to return to sport imminently. 

Extra-corporeal shockwave therapy 

Extra-corporeal shockwave therapy (ESWT) offers a cheap, relatively painless, easily administrable option in the treatment of chronic Achilles tendinopathy. ESWT stimulates soft-tissue healing primarily by inhibiting afferent pain-receptor function and by enhancing angiogenesis.^10,11 In practice, it is used more often to reduce pain for short periods allowing the patient to focus on eccentric exercise.¹²

Topical nitrate therapy

Application of topical glyceryl trinitrate (GTN) patches locally to the affected tendon provides sustained symptom relief during exercise by 12 weeks if used daily.¹³ A commonly used dose is 1.25mg of GTN per day. In chronic patellar tendinopathy, GTN in conjunction with eccentric exercise programmes shows average results at decreasing pain scores over 24 months.¹⁴

However, long-term outcomes for the use of GTN in Achilles tendinopathy are unclear. Dizziness and headaches are theoretical, but rare side-effects. 

Injectable therapies

Injection of sclerosing agents

Polidocanol is a sclerosing agent, with additional anaesthetic properties, used in the treatment of chronic tendinopathies (Achilles and patellar) as well as varicose veins.^15,16,17 Polidocanol is thought to work selectively in the vascular intima causing thrombosis of small vessels. This is particularly pertinent to chronic tendinopathies, where neovascularisation is thought to be part of the underlying pathophysiology. It can be administered under colour Doppler ultrasound guidance with the patient lying prone. The substance is injected into the tendon at regions where neovascularisation exists until vascular flow disappears. Small quantities (0.1-1ml) of the substance are required and concentration (5mg/ml versus 10mg/ml) does not appear to affect results.¹⁸

Following therapy, rehabilitation consists of one to three days of rest followed by a gradual increase in tendon-loading activity culminating in maximal loading after two weeks. 

Miscellaneous injectable therapies

High-volume image-guided injection and aprotinin

In more recent years alternative injectable therapies have been studied. Aprotinin is a basic pancreatic trypsin inhibitor derived from bovine lung. Previous uses of aprotinin include cessation of bleeding post-operatively.¹⁹ Allergic reaction is, unfortunately, a relatively common side-effect. High-volume, image-guided intra-tendinous injections have been studied with various combinations of substances. 

A case series of 94 athletes injected with a combination of 10ml of 0.5% bupivacaine, 25mg of aprotinin and 40ml of 0.9% normal saline showed promising results for the treatment of Achilles tendinopathy.²⁰ Another combination of 10mls of 0.5% bupivacaine, 25mg of hydrocortisone and 40ml of 0.9% saline also showed improvements in both symptomatic and radiological scores.²¹

Platelet-rich plasma

Injection of autologous, centrifuged platelet-rich plasma (PRP) is a novel therapy being studied and used in the treatment of various musculoskeletal disorders. 

It has been shown to be of benefit compared to other therapies in the treatment of tennis elbow (lateral epicondylitis).^22,23

In the treatment of chronic Achilles tendinopathy, several small, randomised, controlled trials have not demonstrated superiority of PRP over control (small volume saline injection), in both clinical and radiological outcomes.^24,25,26 Currently, PRP injections are not recommended in the treatment of chronic mid-portion Achilles tendinopathy.

Corticosteroid injection

Peri-tendinous injection of corticosteroid in Achilles tendinopathy is generally thought to have short-term analgesic effects. Intra-tendinous corticosteroid injection is contra-indicated due to its catabolic effects and inhibition of collagen synthesis.²⁷ Some reports of Achilles tendon rupture following intra-tendinous corticosteroid injection are also described.^28,29

Surgical intervention

Surgical intervention for mid-portion Achilles tendinopathy includes open removal of diseased tendon tissue and percutaneous tenotomy. Open surgery produces its most successful results in cases where diffuse tendon disease exists.³⁰ Percutaneous tenotomy offers good or excellent results in 75% of patients.³¹

Both open and percutaneous surgical methods require extensive and reliable rehabilitation in order to achieve successful outcomes. 

References 

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