It is important to distinguish a ruptured Achilles tendon from both an incomplete tear of the tendon, and from a tear of the soleus muscle. Up to 25% of ruptures are missed at first presentation and the delay in their treatment may significantly impede subsequent recovery.
Tests for a ruptured Achilles tendon include:
- tiptoe test:
- a patient whom is able to stand on tiptoe on their affected leg is very unlikely to have a ruptured achilles tendon
- other causes of a painful foot or ankle may also prevent standing on tiptoes (i.e. it is a highly sensitive but non-specific test)
- Simmond's squeeze test and Copeland's pressure test are both sensitive tests for Achilles tendon rupture
diagnostic process:
The diagnosis of acute Achilles tendon rupture may be missed by non specialist in 20% of the cases. This may be due to several reasons:
- clinician may think of local bruising (rather than a rupture) based on the patients explanation (kicked or hit on the back of the heel tendon by a ball or racquet)
- the injury may be considered trivial due to:
- absence of an audible snap on patient history
- absence of pain in around a third of patients
- mild external bruising and swelling (since tendon usually ruptures within its paratenon sheath)
- a gap may not be felt in longitudinal tears
- other plantarflexors may mask the weakness from a ruptured Achilles tendon (1,2,3)
Physical examination
Instruct patient to lie prone on the examination couch with feet hanging over the edge.
- defect in the Achilles tendon is visible in most of the patients accompanied by swelling due to peritendinous haemotoma
- defect is usually palpable (with a sensitivity of 0.71 and specificity of 0.89)
- specific test for diagnosis include: Simmonds or Thompsons’ test
- Thompsons’ test - muscles of the calf is squeezed gently while the motion of the foot is observed
- in an intact tendon - the foot planterflexes (negative test)
- false negative can occur in
- when the patient has an intact plantaris tendon
- in the setting of a chronic rupture, where scar tissue and fibrosis of the paratenon can mimic continuity between the gastroc-soleus muscle belly and the calcaneus
- in ruptured tendon - little or no plantar flexion of the foot relative to the contralateral leg (positive test) (1,2)
Simmonds’ triad (angle of declination, palpation for a gap, and calf squeeze) is the preferred examination method since it yields a more accurate diagnosis when compared to Thomson’s calf squeeze test alone (2).
- look (observe for angle of declination of the foot)
- altered angle of declination (or “angle of dangle”) indicates the loss of tension caused by the ruptured tendon
- when compared to the normal leg, ankle and foot of the affected leg is positioned in a more dorsiflexed position
- a modified test was introduced by Matels
- patient is instructed to actively flex the knee through 90° while observing whether the foot of the injured leg falls into a more dorsiflexed position
- this test alone has a sensitivity of 0.88 and a positive predictive value of 0.92
- feel - palpate for the gap
- palpate the tendon along its entire length to identify a gap
- sensitivity is only 0.73 and the positive predictive value is 0.82
- move - calf squeeze
- similar Thomson’s calf squeeze test
- results should be recorded as as “plantarflexion noted” or “plantarflexion not noted” (since “calf squeeze test positive” could mean either positive plantarflexion or positive rupture)
- has a sensitivity of 0.96 and a positive predictive value of 0.98 (2)
Imaging
- usually not required since the condition can be diagnosed clinically
- if diagnosis is unclear (partial rupture or tendinopathy), ultrasonography or MRI may be helpful
- ultrasound:
- is better than radiography
- may distinguish:
- complete rupture
- partial rupture
- paratenonitis
It is important that a patient with suspected acute Achilles rupture is referred to an orthopaedic surgeon on the same day rather than requesting investigations which may delay treatment (2).
Note:
- the Simmonds triad is preferred to Thomson’s isolated calf squeeze test
- comparative studies have reported that two of the three tests were positive in all ruptures making the sensitivity 100% for this triad
Reference: