Case Study: Diagnostic Ultrasound of Achilles Tendinopathy – how does Diagnostic Ultrasound fit into physiotherapy practice?

Suegnet

Author: Suegnet Meyer, MSc, BPHYST, PGCert MSK US (cand).

© 2020 Suegnet Meyer. All rights reserved.

Slide 1: Non-insertional or Mid-portion Achilles tendinopathy: Does Diagnostic Ultrasound fit into Physiotherapy Practise?

This presentation was constructed as part of completing a postgraduate qualification in Musculoskeletal Sonography at Brunel University, 2020. This case has been anonymised and patient consent obtained.

Slide 2 : Case description

A 54-year-old female walker, presented at the clinic with left mid-portion achilles pain that was present for the last 3 months (Figure 1). No co-morbidities or red flags were present. The athlete was taking NSAIDS that provided some relief.

The athlete had very high expectation to return to sport. The question was if the US imaging can predict the outcome and safely return to sport?

Slide 3: Clinical presentation and Diagnostic Tests.

On assessment, the cardinal symptom was pain, 3cm proximal to the insert of the achilles tendon on the calcaneus. The tendon contours presented with swelling and tendeness over the AT mid-portion.

A functional limitation was demonstrated during a single heel raise when comparing to the opposite side. Biomechanically, the left forefoot was in a varus stance. Weakness of the posterior kinetic chain was observed.

The Victorian Institute of Sport Assessment- Achilles Questionnaire (VISA-A), demonstrated a low score, (Robinson et al, 2001). A reduced VISA-A score usually indicate an increased pain and severity of Achilles tendinopathy.

No difference exists between different the three clinical tests for Achilles tendinopathy: Palpation of 2-6cm proximal to AT insertion and crepitus, the Painful arc sign and the Royal London Hospital test (Sensitivity = 0.568, Specificity = 0.833), were present, (Maffulli, 2003; 2020). By performing clinical testing, is usually sufficient to diagnose mid-portion Achilles tendinopathy. However, the current case, an US Scan, Doppler studies and measurements were considered, to rule out further pathology for instance partial tears.

Slide 4: Prevalence and region of the injury

Achilles tendinopathy is a common overuse injury. The prevalence of mid-portion achilles tendinopathy is high, at approximately 60% of all reported achilles injuries in runners between the ages of 21 to 60 years. De Jongh et al (2011), determined the incidence of 2.35 in every 1000 runners.

The location of the injury has been described as the mid-portion of the Achilles which is located between 2-6cm proximal of the Achilles insertion onto the calcaneus, (Figure 2).

Slide 5 : Aetiology of Achilles tendinopathy

The aetiology of Achilles tendinopathy is mostly unknown. It is hypothesised that the cause may be multifactorial with key element of overuse that will affect the healing response of the hypo-vascular middle third of the AT. Other extrinsic and intrinsic factors may also have an influence on the AT.

Extrinsic factors include : Changes in training patterns which a loading component together with errors in foot wear causes overuse. Other factors for instance hard surfaces or changing of the surface that the athlete is training or playing on may aggravte the tendon. The dysfunction ie weakness or length of Gastrocnemicus and particularly Soleus may play a role. The incraesed body weight in correlation with the athlete’s height (Leung et al 2008). Biomechanical factors for instance a cavus or forefoot varus or chronic lateral ankle instability may also contribute to the development of Achilles tendinopathy (Maffulli, 2003).

Medication for instance Fluoroquinolones enhances MMP3 release and inhibit tenocyte proliferation while cortico-steroids reduce collagen & matrix synthesis, (Parmar, 2007).

Intrinsic factors that influence the tendon composition for instance metabolic diseases – Diabetes Mellitus and Hypercholesterolemia, may cause early ruptures of AT. Inflammatory Arthropathic & other rheumatologic disorders will also have a negative effect on tendons, (Maffulli, 2003; Maffulli, 2019; Molyneux, 2017).

Slide 6 : Pathophysiology of Achilles Tendinopathy

Many pathophysiological tendinopathy theories have been proposed.

Cook & Purdam (2009), proposed the Tendinopathy Continuum. The Continuum consist of three phases: the Reactive phase, the Disrepair phase and the Degenerative phase. The three phases may be well established on Diagnostic Ultrasound imaging but do not correlate with the patient’s symptoms and cannot predict outcome. Furthermore, Cook (2012), proposed the effect of excessive compressive loads the may also have an effect on tendinopathy.

The role of the stretch shortening cycle & transferring force from the gastrocnemius & soleus has also been researched, (Sibernagel, 2007). Recent studies have assessed tendon morphology and mechanical properties (Arya, 2010; Coombes, 2018; Corrigan, 2020; Zhang, 2017). This new research may hold the key in predicting tendinopathy management and outcome.

Slide 7 : Performing the scan and creating images

Prior to performing the ultrasound scan, patient consent was obtained. The patient was placed with the feet over the side of the plinth, with the ankles at 90 degrees of dorsiflexion (Figure 3). The ESSR scan protocol was followed. Some of the ultrasound images are presented here.

Slide 8 : Ultrasound images: Longitudinal view of the AT insertion.

The image produced here demonstrates the calcaneal insertion of the AT. Note the Anisotropy that is displayed by the open arrow. The AT is slightly hypo-echoic and the fibrillar pattern is not very well defined. The Kager’s fat pad appears normal and no retro-calcaneal bursa is present (Figure 4).

Slide 9 : Longitudinal view of Mid-portion AT

The mid-portion of the AT is distended, and presents hypo-echoic with a loss of the fibrillar pattern. It is measured at 1.04cm, (Figure 5). An advantage of ultrasound is to perfom a quick measurement of the opposite AT. Biachi et al (2014), estimate that a normal AT thickness is approximately 0.5cm.

Many have debated which is more accurate view to perform the tendon thickness measurements. In this study, longitudinal or cross-sectional and wide-view studies produced very similar measurements.

Slide 10 : Ultrasound image of cross-section of the mid-portion AT

The mid-portion cross-sectional view identifies some an-echoic regions in the posterior medial quadrant of the tendon which may indicate some moderate tendon degeneration. The fibrillar pattern is not well defined and the tendon presents hypo-echoic, indicating moderate degenerative tendinopathy, (Figure 6). The anterior-posterior cross-sectional tendon measurements are measured (1.09 x 1.92cm).

Slide 11 : Power Doppler study of the Mid-portion AT

The Ultrasound Power Doppler is a valuable novel tool of Diagnostic Ultrasound. This useful tool is unique to Diagnostic Ultrasound and one of the biggest differences when compared to MRI. Doppler Ultrasound is more sensitive than Colour Doppler when assessing soft tissue structures. Power Doppler, which is not bound by the direction of blood flow, but simply indicate that blood flow is present. If it is taken in consideration that a normal mid-portion AT is hypo-vascular, then this increased signalling on Power Doppler is most certainly abnormal, (Figure 7a & b). The Power Doppler is more sensitive to smaller blood vessels. The signalling indicate an increase of blood flow or vascularisation which is associated with hyperemia, an inflammatory reaction and tendinopathy.

Many have discussed the clinical significance of Doppler signalling. It was thought that an increased Power Doppler presentation indicate an increased severity and worse clinical outcome of tendinopathy, (Yang et al, 2010). However, recent studies have demonstrated that Doppler blood flow is not a reliable measure to correlate patient symptoms, (De Vos et al, 2007; Docking et al, 2015). However, ongoing studies are researching the possibility of Doppler Surface Area Quantification that may be a reliable method to correlate with the severity of symptoms, (Van der Vlist et al, 2020).

Further attention should be paid to the small Saphenous vein posterior-lateral aspect of ankle, that must not be confused with hyperemia, (Martonoli, 1993).

Slide 12 : Diagnostic Ultrasound Machine settings

The ultrasound scan was performed by using a GE LogiqQ (GE Healthcare, Wautwatosa, WI). A Linear Transducer L4-12t was used at a frequency setting of 13MHz. The frequency setting is determined by the structure depth. If the structure is superficial, the frequency used will be higher with a shorted wavelength. The higher the frequency setting will reduce the ultrasound wavelength (λ) and reduce the wave penetration. Thus ultrasound beam will penetrate less due the shorter wavelength (f=1/λ). Further settings will also optimise the image for instance the gain, focus and depth settings, (Figure 9).

Slide 13 : Physics Principles in Diagnostic Ultrasound

For easy comprehension of the physics principals of the Diagnostic Ultrasound scan of tendons, it is important to consider the tendon histopathological changes that occur. This will explain the pathological appearances of structures on the scan imaging.

Histology in tendinosis

During tendinopathy an increase in cell numbers occur. Due to this cell proliferation, tenocytes arrangement changes. The shift of proteoglycan content to hydrophilic proteoglycans are caused by an increased water content. This presents as oedema and thickening of the affected tendon. On Diagnostic Ultrasound a reduction in echogenicity (thus darker) will be presented and the tendon thickness dimensions will increase, (Docking, 2015, Smith et al 2009a; Smith et al 2009b).

Fibrillar disorganisation

In a normal tendon, Type 1 Collagen is presented as hyper-echoic ultrasound image. The healthy fibres are arranged parallel towards each other. The ultrasound beam is projected at a perpendicular angle, the reflected single beam image will be presented as a well-defined fibrillar pattern. The healthy tendon will appear hyper-echoic or bright.

During tendinopathic changes the haphazard arrangement of the fibres occur. Collagen Type 1 changes to Type 2 & 3. The fibrillar pattern is now aberrant. The perpendicular ultrasound beam is projected upon the tendon, creating multiple reflections & shadowing due to fibrillar disorganisation. The tendon will then appear hypo-echoic (darker) with the absence of the fibrillar pattern. For this reason, black or an-echoic regions determined in longitudinal and cross-sectional views, usually indicate tearing or degeneration, (Docking et al 2015; Smith et al 2009a; Smith et al 2009b).

Slide 14 : Physics Principles in Diagnostic Ultrasound

Anisotropy

Anisotropy is the major pitfall in any MSK ultrasound. This occur when the ultrasound beam lack reflection since the beam was not perpendicular to the structure, (Smith et al 2009a; Smith et al 2009b). This will appear darker and can easily be mistaken for tears or tendinosis, (Docking, 2015; Leung et al 2007). By moving the transducer at various angles and interrogating the structure in longitudinal and cross-sectional views, will eliminate this error, (Figure 10 a & b).

Slide 15 : Physics in Diagnostic Ultrasound

Error in Measurements

Errors in the measurement of tendons may occur due to incorrect probe skills. This may result in overestimating the tendon calibre. In the cross-sectional measurement (Figure 11), it is important to ensure that the US beam is perpendicular to avoid any artifactual hypo-echoic pattern (Leung et al 2007). During longitudinal measurements, the anatomical torsion of the AT must be taken in consideration to avoid any measurement errors, (Pekala et al, 2017).

Slide 16 : The Diagnostic Ultrasound report

Slide 17 : Evidence based literature relating to Diagnostic Ultrasound

Which Image is gold standard when assessing AT tendinopathy?

The accuracy, sensitivity and validity of Diagnostic Ultrasound compared to MRI when assessing AT tendinopathy to determine what is the gold standard imaging modality (Table 1). Accuracy is defined by the number of correct imaging diagnoses, both abnormal and normal imaging, divided by the total number of cases. While sensitivity – number of correct abnormal imaging diagnoses divided by the total number of symptomatic cases, (Khan, 2003). According to

Contrast-enhanced MRI (CME-MRI) good correlation histopathology in chronic Achilles tendinopathy (Shalabi, 2002). CME-MRI showed a greater sensitivity in comparison to US when assessing hypoechoic achilles tendinopathy, (Docking, 2015; Movin et al, 1998).

Slide 18 : Evidence based literature relating to Diagnostic Ultrasound

Which Imaging modality is the gold standard in the assessment of AT tendinopathy?

MRI is expensive but provide good soft tissue contrast detail. US is cheaper assessment and easy to perform as a point of care in clinic but is operator depended. It has the advantage functionality of Doppler blood flow (Smith, 2009a; Smith, 2009b).

It is suggested that if ultrasound is inconclusive, MRI should be considererd but MRI is more objective in the assessment of Achilles tendinopathy (Neuhold, 1992).

Slide 19 : Evidence based literature relating to Diagnostic Ultrasound

Is the scan telling the whole story?

The mechanisms of tendon injury remain poorly understood, but the characteristics of injured tendons are well documented histologically, biochemically and at imaging. These three investigation techniques reveal distorted tendon appearance, hypercellularity, disorganized collagen bundles, increased proteoglycan content and neovascularization in chronic tendinopathic tendons. (Longo, 2009; Rees, 2009).

Can Imaging Predict the Onset of Pain or Clinical Outcome in Achilles tendinopathy?

Clinical usefulness of imaging have been criticised extensively. The clinical assessment of AT tendinopathy is sufficient, and it is unnecessary to determine morphological changes as it does not represent the patient symptoms or clinical outcome (De Jonge, 2015; Ryan, 2015). 

Other studied – Structural changes & measurements may be a predictor for the likelihood of developing symptoms, (Jhingan, 2011; Hirschmuller, 2012, Leung, 2007).

Good patient outcome: It is important to assess the tendon morphology and structure aim to provide better patient expectations. Currently, the norm is to manage patients with 3 months of exercise therapy prior to consider any other treatment, (Alfredson, 2007). 

It is agreed that to image the shape, size and measurement of tendons does not correlate with capabilities of the tendon load transferring & absorption. 

However, a recent study compared the initial diagnostic measurements, patient reported outcome Visa-A,  Calf muscle endurance single heel raise until fatigue , and continues shear-wave elastography  that was followed it up at 6 months and again at 1 year, n=59.

The result was that an initial US AT measurements thickness are associated with VISA-A outcome and muscle function that can be used as an outcome predictor for patients with symptoms up to 1 year, (Corrigan, 2020)

Slide 20: Summary of Evidence Based Practice

In clinical Physiotherapy practice:

Assess Achilles tendinopathy by clinical assessment, single heel raise, VISA-A outcome s and measurements in combination with the VISA-A scores to guide the outcome. Consider MRI if any doubts exists.

Shear-wave Elastography, in combination with US, outcome measurements and single heel raise assessment hold promising results to predict outcome for patients with symptoms less than 1 year.

Uncertainty whether measures of Achilles tendon structure and morphology can inform decisions regarding correct type of exercise treatment or safe return to sport.

Slide 21 : Learning points

Point of Care Assessment of Achilles tendinopathy: Clinical Assessment, USS, VISA-A outcome measurement and single leg heel raise may predict a better outcome.

If USS result is inconclusive perform an MRI.

Shear-wave Elastography, in combination with US, outcome measurements and single heel raise assessment hold promising results to predict outcome for patients with symptoms less than 1 year.

Uncertainty whether measures of Achilles tendon structure and morphology can inform decisions regarding correct type of exercise treatment or safe return to sport.

Future research: Shear-wave elastography in combination with USS to determine effective AT exercise programmes and RTS.

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