What is the best clinical test for Achilles tendinopathy?

Abstract

Background

Differential diagnosis of Achilles pathology is demanding. This study evaluates the diagnostic accuracy of clinical tests identified for a chronic mid body Achilles tendinopathy. Ultrasound scanning provides the reference standard.

Methods

Twenty-one participants with, and without, an Achilles tendinopathy, had an ultrasound scan followed immediately by the application of ten clinical tests. The accuracy and reproducibility of each test was determined.

Results

The most valid tests are; pain on palpation of the tendon (sensitivity 84%, specificity 73%, kappa 0.74–0.96) and the subjective reporting of pain 2–6 cm above the insertion into the calcaneum (sensitivity 78%, specificity 77%, kappa 0.75–0.81).

Conclusion

Only location of pain and pain on palpation were found to be sufficiently reliable and accurate, to be recommended for use.

Introduction

Accurate clinical diagnosis of a chronic mid body Achilles tendinopathy is not straightforward. There are numerous differential diagnoses: retrocalcaneal bursitis, bone anomalies (painful os trigonum), anomalous soleus, complete or partial rupture of the Achilles, tarsal tunnel syndrome [1], neuroma/neuritis of the sural nerve, rupture posterior tibial tendon, arthritic conditions of the ankle, plantar fasciitis [2], [3], tenosynovitis of flexor hallius longus (FHL), oseteochondral lesions of talus [4], stress fracture and infection [4], [5].

For appropriate treatment it is essential that accurate clinical diagnostic tests are used. Moreover, such tests are critical to the validity of clinical trials assessing the efficacy of intervention.

Diagnostic tests include clinical examination tests, MRI scans and ultrasound scans. Radiological investigations are expensive and not always readily available. Principle diagnosis of Achilles tendinopathy relies on an array of subjective and physical clinical tests.

A literature review identified current clinical examination tests used in the diagnosis of mid body Achilles tendinopathy. Medline, Pub Med, AMED, Ovid, CINAHL, Embase and Cochrane databases were searched. No restriction was placed on the type of papers to be included in the review compensating for the paucity of literature on clinical diagnosis of chronic mid body Achilles tendinopathy. All reviews, reports, guidelines and clinical trials that contained details regarding the clinical diagnosis of a chronic mid body Achilles tendinopathy were included. Papers that included insertional tendinopathies, were excluded.

The review identified 10 clinical diagnostic tests (Table 1). These fall broadly into three categories: subjective tests, palpation tests and tendon loading tests. Ultrasound scanning was the only radiological investigation identified.

This study evaluates the diagnostic accuracy of these ten clinical tests used to diagnose a chronic mid body Achilles tendinopathy using ultrasound scanning as the reference standard.

To the authors knowledge only three of the clinical tests had been investigated for accuracy. Maffulli et al. [6], reported the sensitivity and specificity of “Palpation”, “The Arc Sign” and “The Royal London Test” (see methods for a description of each test) [6].

Three participant groups were recruited; (A) patients with known chronic mid body Achilles tendinopathy, (B) patients with known posterior ankle pain, not caused by an Achilles tendinopathy and (C) participants with no posterior ankle pain or tendinopathy pathology. The inclusion criteria for group A were participants with: ultrasound evidence of Achilles tendinopathy and symptom duration of three months or more. Group B inclusion criteria were: no ultrasound evidence of Achilles tendinopathy but presence of posterior ankle pathology. Group C inclusion criteria were: healthy asymptomatic subjects with no evidence of Achilles tendinopathy on ultrasound examination. Exclusion criteria for all three groups included participants who: (1) were unable to follow commands or instructions, (2) were aged below 18 years or (3) had medical conditions that could confound the test results. Group A and B patients were recruited from the physiotherapy department and out patient orthopaedic clinic of the hospital where the study was conducted. Group C participants were recruited from colleagues and associates of the chief investigator. A consultant radiologist conducted an ultrasound examination of participants Achilles tendons prior to their entry into the study. The study was approved by the local Research and Ethics Committees (10/WMWO2/7).

Immediately following ultrasound examination each subject, was examined by two orthopaedic surgeons and one senior physiotherapist. The clinicians were blind to the ultrasound and other examination findings. The clinicians received training and had participated in a pilot study in order to standardise the tests. The chief investigator (AMH) invigilated the examination process to ensure standardisation. The clinical assessments were conducted in two separate sessions (n = 10 and n = 11). The order, which the participants were assessed, was randomised.

To account for potential confounding by pain/discomfort elicited by repeated testing, pain levels were assessed before each examination using a Visual Analogue Scale (VAS). To test the reliability and reproducibility of the clinical tests the entire procedure of the clinical tests examination was repeated. The sequence of the second assessment was also randomised.

A Consultant Musculoskeletal Radiologist (RE), performed the ultrasound examination using a Toshiba Aplio 80 Machine with an 8 MHz linear probe. Each patient was positioned prone with their feet off the end of the examination couch. The Achilles tendon was examined from the musculotendinous junction to its insertion on the calcaneus in both the longitudinal and transverse planes. The ultrasound reference standard criteria for an Achilles tendinopathy was defined as the presence of hypoechogenic area within the substance of the tendon, with loss of normal, well organised, ribbon-like intratendinous echo structure [7], [8], [9] or an increase of the anterior diameter of the tendon greater than 50% of the asymptomatic contralateral [6].

The tests identified from the literature (Table 1) were reviewed by four orthopaedic surgeons (PW, CT, NV & IP) and three senior physiotherapists (AMH, DJB & VM). Not all the clinical tests had been clearly defined in the literature. In such cases a definition of each test was agreed by consensus amongst the clinicians. All 10 tests were selected to be investigated for accuracy and are described in Table 2.