Thompson Test

Thompson Test (or as it called Calf Compression Test or Simmonds’ test) is used to identify the presence of a complete Achilles tendon rupture. It was first described by Franklin Adin Simmonds (1911-1983), an English Orthopedic Surgeon at the Rowley Bristow Hospital, Surrey. ¹

How do you perform Thompson test?

• In this test, the patient lies in the prone position or in kneeling with the feet over the edge of the bed.
• With the patient relaxed, the clinician gently squeezes the calf muscle and observes for the production of plantar flexion.

See Also: Ankle Anatomy

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What does a positive Thompson Test mean?

Compressing the calf muscles should normally provoke rapid passive plantar flexion of the foot.

• Absence of this plantar flexion suggests a torn Achilles tendon (Positive Thompson Test).
• The response to the compression test is not always unambiguous in patients with partial tears and will depend on the degree of disruption.
• In an Achilles tendon tear, the patient will be unable to stand on tip toe, especially when standing only on the injured leg, and the Achilles tendon reflex will be absent.

In cases where the gastrocnemius aponeurosis is separate from soleus, the Thompson test may be falsely positive as the “squeeze” has predominant effect on gastrocnemius muscle belly rather that soleus.

Accuracy

Thompson Test has a high Sensitivity and Specificity according to one study by Maffulli ^2–3 on 174 patients with suspected Achilles tendon tear referred to orthopaedic clinic (The Reference Standard surgical confirmation for subjects with the diagnosis; magnetic resonance imaging (MRI) and ultrasound for subjects without the diagnosis.):

• Sensitivity: 96 %
• Specificity: 93 %

The Thompson test seems to show very good diagnostic utility in both identifying and ruling out subcutaneous tears of the Achilles tendon.

Notes

• The Thompson Achilles tendon tear test can also be performed with the patient prone and the knee flexed 90°. In this position, the examiner grasps the patient’s calf with both hands and forcefully com presses the musculature. Loss of plantar flexion is a sign of an Achilles tendon tear (Simmonds’ test).

• It’s possible that the plantaris muscle and deep toe flexors can still plantar flex the foot although the Achilles tendon is ruptured.

To make sure that the Achilles tendons is torn, look for these clinical signs that can be seen to confirm the diagnosis:

1. With the patient prone, and ankle relaxed , the foot on the affected side hangs straight down because of the absence of the tendon tone.
2. A palpable gab can be felt in the Achilles tendon, about 3-6 cm proximal to its insertion onto the calcaneus.
3. The strength of the plantar flexion is reduced compared to the other side.

Related Anatomy

• Achilles tendon consists of uniting three muscles which the plantaris, gastrocnemius and soleus muscles, it rotates 90 degrees laterally to insert on the posterior aspect of the calcaneal tuberosity.
• Achilles tendon is hypovascular 4 to 6 cm proximal to the calcaneal insertion.

Muscle	Origin	Insertion	Action	Innervation
Gastrocnemius	Posterior medial and lateral femoral condyles	Calcaneus	Plantar flexing foot	Tibial (S1) nerve
Soleus	Fibula/tibia	Calcaneus	Plantar flexing foot	Tibial (S1) nerve
Plantaris	Lateral femoral condyle	Calcaneus	Plantar flexing foot	Tibial (S1) nerve

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Rupture of the Achilles Tendon

Rupture of the Achilles tendon was first described in 1575, and first reported in the literature in 1633.

Although the etiology of a spontaneous rupture remains incompletely understood, a number of theories have been proposed, including:

1. microtrauma,
2. inhibitor mechanism malfunction,
3. hypoxic and mucoid tendon degeneration,
4. decreased perfusion,
5. systemic or locally injected steroids.

However, the fact that the peak incidence of Achilles, tendon rupture occurs in the middle age group rather than in the older population tends to lend credence to a mechanical etiology.

Three specific activities have been implicated in rupturing the Achilles tendon:

1. Pushing off on the forefoot while extending the knee.
2. Sudden dorsiflexion with full-weight-bearing as might occur with a slip or fall.
3. Aggressive dorsiflexion such as that occurs when jumping or falling from a height and landing on a plantar flexed foot.

The diagnosis of an Achilles tendon rupture is based almost solely on the history and physical findings:

• The classic history includes reports of sudden pain in the calf area, often associated with an audible snap, followed by difficulty in stepping off on the foot.
• Physical examination reveals swelling of the calf as well as a palpable defect in the tendon (hatchet strike), as well as ecchymosis around the malleoli.
• Perhaps, the most reliable sign of a complete rupture is a positive Thompson Test.

Treatment options for an Achilles tendon rupture include surgical and non-surgical approaches, although opinions are divided as to what is the best course of action:

• The conservative intervention of Achilles tendon rupture traditionally consisted of short- or long-leg cast immobilization in the gravity equinus position (10–20 degrees of plantar flexion). However, this approach was found to result in a high incidence of re-rupture (10–30%)^4–5 and a decrease in maximal function. This may be because it is impossible to restore the correct length of the Achilles, tendon with nonoperative treatment. Recent studies have produced superior results with a much quicker rehabilitation using fixed or hinged boots.
• The results from the surgical approaches have varied with the recent studies reporting small, but statistically significant benefits from surgery.^{6 – 7}

References

1. Simmonds FA (1957). “The diagnosis of the ruptured Achilles tendon”. The Practitioner. 179 (1069): 56–8. PMID 13453094.
2. Chad Cook, Pt, Phd, Mba. “Diagnostic Accuracy Of Physical Examination Tests Of The Ankle/Foot Complex: A Systematic Review”. Sports Physical Therapy Section 2013 Aug; 8(4): 416–426. Pmcid: Pmc3812842.
3. Lea RB, Smith L. Non-surgical treatment of tendo achillis rupture. J Bone Joint Surg Am. 1972 Oct;54(7):1398-407. PMID: 4655535.
4. Nistor L. Surgical and non-surgical treatment of Achilles Tendon rupture. A prospective randomized study. J Bone Joint Surg Am. 1981 Mar;63(3):394-9. PMID: 7204438.
5. Metz R, van der Heijden GJ, Verleisdonk EJ, Tamminga R, van der Werken C. Recovery of calf muscle strength following acute achilles tendon rupture treatment: a comparison between minimally invasive surgery and conservative treatment. Foot Ankle Spec. 2009 Oct;2(5):219-26. doi: 10.1177/1938640009348338. Epub 2009 Sep 4. PMID: 19825777.
6. Willits K, Amendola A, Bryant D, Mohtadi NG, Giffin JR, Fowler P, Kean CO, Kirkley A. Operative versus nonoperative treatment of acute Achilles tendon ruptures: a multicenter randomized trial using accelerated functional rehabilitation. J Bone Joint Surg Am. 2010 Dec 1;92(17):2767-75. doi: 10.2106/JBJS.I.01401. Epub 2010 Oct 29. PMID: 21037028.
7. Reiman M, Burgi C, Strube E, Prue K, Ray K, Elliott A, Goode A. The utility of clinical measures for the diagnosis of achilles tendon injuries: a systematic review with meta-analysis. J Athl Train. 2014 Nov-Dec;49(6):820-9. doi: 10.4085/1062-6050-49.3.36. PMID: 25243736; PMCID: PMC4264655.
8. Figliuzzi A, Alvarez R, Al-Dhahir MA. Achilles Reflex. [Updated 2021 Jul 31]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2022 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK459229/
9. Clinical Tests for the Musculoskeletal System 3rd Edition.
10. Dutton’s Orthopaedic Examination, Evaluation, And Intervention 3rd Edition.