Intern Ultrasound of the Month: Achilles Tendon Tear

The Case

A 52-year-old male presented to the emergency department with left heel and lower leg pain. He stated he was running outside the day prior and stepped into a pothole on the trail. There was immediate pain that initially got better with rest; however, it became worse again today. He had dull pain that began a few weeks prior but was manageable with ice and ibuprofen. He has been able to walk but has had limited range of motion at the ankle. He denied any pain or issues with the knee. He is overweight and recently started a running program to lose weight. His medical history was significant for non-insulin dependent diabetes, for which he is on metformin, and obstructive sleep apnea. He quit smoking about 10 years ago and drinks 3-4 beers per week. Six months ago he quit his office job to work in construction renovating homes. 

Physical exam was significant for reduced range of motion in the ankle due to pain and mild tenderness with palpation of the calf, however was otherwise unremarkable. Equivocal Thompson test. There was no point tenderness at the medial or lateral epicondyles. X-rays of the foot, ankle, tibia and fibula were negative for fractures or bony abnormalities. Suspecting an Achilles injury, point-of-care ultrasound was performed to evaluate.

POCUS findings: enlargement of the achilles tendon with near complete disruption of the fibers, retracted and hyperechoic edges, and multiple hypoechoic areas within the tendon. Compare to the unaffected tendon.

Case continued: He was placed in a splint, and Orthopedic surgery was consulted to help facilitate follow up. He was discharged home with crutches, non weight-bearing instructions, and supportive care. Subsequently underwent outpatient surgery without complication.

Achilles Injuries

The Achilles tendon is the strongest tendon in the body, yet, athletes and non-athletes alike often injure it [1]. The common calf muscles, the gastrocnemius and the soleus, meet in the distal leg forming the Achilles tendon before inserting at the posterior calcaneus. These muscles are major players in plantarflexion of the foot. Therefore, when it becomes compromised, there may be a general disruption to the patient’s gait, however ambulation is usually still possible due to accessory muscles, such as the tibialis posterior. The weakest point of the Achilles tendon is 2-6 cm proximal to the insertion at the calcaneus. This is the site of least blood flow to the tendon and is also the site of the greatest tenderness with palpation on exam [2]. It is generally accepted that weakness, inflammation, or a systemic disease usually precipitates Achilles tendon tears, unless one injures it during high energy sports [1]. The Thompson test is a physical exam maneuver that can aide in the diagnosis of an Achilles injury. With the patient laying prone, squeeze the gastrocnemius muscle belly. A lack of plantarflexion with this action is indicative of an Achilles injury. The Thompson test is a well-supported component of the physical exam with a sensitivity of 96% and specificity of 93% [3]. If there is high suspicion of Achilles injury but a negative Thompson test, further imaging should be obtained.

 

Review of Imaging Modalities

Ultrasound and MRI are the imaging modalities most used to assess muscle, soft tissue and ligamentous injuries. Specifically in the emergency department, ultrasound is a readily used and widely accepted modality to evaluate musculoskeletal complaints [4]. Many studies have recommended ultrasound for the diagnosis of Achilles tendon rupture, specifically over MRI, as it is “cheaper, more dynamic, less time-consuming, [correlates] better with the clinical picture, and showed tendon defects in higher number” [5]. The sensitivity of ultrasound ranged from 80-100% while some studies report a 100% specificity. One study found that performing the Realtime Achilles Ultrasound Thompson (RAUT) test during ultrasound examination is both more sensitive and specific. The RAUT test increased the sensitivity of ultrasound from 76.8% to 87.2% and specificity from 74.8% to 81.1% for novice users [6].

MRI has been shown to have a sensitivity as high as 91% with a specificity of 100% [5]. However, one of the drawbacks of MRI imaging is that it often detects subtle abnormalities that may overestimate the severity of an Achilles injury when compared to the clinical presentation, leading to potentially unwarranted and harmful intervention [7]. Some studies suggest that partial Achilles tears are more difficult to diagnose with ultrasound and recommend MRI for definitive diagnosis [8-Kayser].

Nevertheless, ultrasound may help with patient disposition, especially when MRI is not immediately available, such as in the emergency department. The ease and accessibility of ultrasound is also a good tool to monitor progression of treatment [5]. However, in general, imaging abnormalities outlast functional recovery, so caution should be used with frequent or repetitive monitoring as a benchmark for return to work or sport [7].  

Ultrasound Techniques for Achilles

Point-of-care ultrasound is quick, relatively easy and provides immediate answers. The Achilles tendon is set up well for ultrasound imaging, as it is very superficial and unguarded by bone or other structures [6].

To ultrasound the Achilles tendon, have the patient lay prone on the bed with the feet hanging off the edge of the bed [9]. As with other musculoskeletal scans, use the linear probe in the MSK setting. You’ll want to scan the tendon in both the longitudinal and transverse axis [9-10]. Start by placing the probe in longitudinal axis close to the foot and identify the hyperechoic stripe of the calcaneus [11]. Knowing this is the point of insertion of the Achilles tendon, scan superiorly identifying and following the tendon.

Normal tendon will appear as layered, continuous, linear fibers. Conversely, an Achilles injury appears discontinuous, with hypoechoic disruption of the tendon fibers, often resulting in heterogeneity [11-12]. The tendon will likely have an increased anterior-posterior diameter due to swelling [9, 12]. In a complete Achilles rupture, an anechoic space may separate portions of the tendon [12]. Finally, performing a Thompson test (squeezing the gastrocnemius muscle) while visualizing with ultrasound would show retraction of the superior portion of the tendon [11].

 

Conclusion

Once the diagnosis is made, patients should be referred to either a sports medicine specialist or orthopedic surgeon to review and discuss treatment options. Management of Achilles tendon rupture is debated and includes both operative and conservative measures. Such conservative measures include physical therapy, shockwave therapy, and local injections [13]. Of note, there is no evidence yet to suggest platelet-rich plasma injections improve functional outcomes in patients who are treated conservatively [14]. As with any surgery, there are inherent complications that accompany repair making it less desirable. However, conservative measures may result in incomplete or improper healing which may have functional consequences down the road as well [15].

 

Take Home Points

  • Ultrasound is quick and easily accessible in the emergency department to evaluate musculoskeletal complaints, including Achilles tendon pathology.

  • Ultrasound and MRI have similar sensitivity and specificity for diagnosing Achilles tendon tears.

  • Look for disruption to tendon fibers, increased tendon diameter, and hypoechogenicity within the tendon or a completely anechoic space within the tendon to diagnose Achilles tendon partial or complete tear.

  • Use the Realtime Achilles Ultrasound Thompson (RAUT) test to increase diagnostic accuracy.  

POST BY: DR. VINCENT MARSHALL (R1)

FACULTY EDITING BY: DR. LAUREN MCCAFFERTY

References

  1. Järvinen TA, Kannus P, Paavola M, Järvinen TL, Józsa L, Järvinen M. Achilles tendon injuries. Curr Opin Rheumatol.  2011; 13(2): 150-155.

  2. Maughan KL, Boggess BR. Achilles tendinopathy and tendon rupture. In Post TW, Fields K, Grayzel J. (Eds.), UptoDate. 2022. Accessed December 2022.

  3. Maffulli N. The clinical diagnosis of subcutaneous tear of the Achilles tendon. A prospective study in 174 patients. Am J Sports Med. 1998;26(2):266

  4.  Situ-LaCasse E, Grieger RW, Crabbe S, Waterbrook AL, Friedman L, Adhikari S. Utility of point-of-care musculoskeletal ultrasound in the evaluation of emergency department musculoskeletal pathology. World J Emerg Med. 2018;9(4):262-266.

  5. Dams OC, Reininga IHF, Gielen JL, Akker-Scheek IVD, Zwerver J. Imaging modalities in the diagnosis and monitoring of Achilles tendon ruptures: A systematic review. Injury, 2017; 48(11):2383–2399.

  6. Griffin MJ, Olson K, Heckmann N, Charlton TP. Realtime Achilles Ultrasound Thompson (RAUT) test for the evaluation and diagnosis of acute Achilles tendon ruptures. Foot Ankle International. 2017; 38(1): 36-40.

  7. Khan KM, Forster BB, Robinson J, et al. Are ultrasound and magnetic resonance imaging of value in assessment of Achilles tendon disorders? A two year prospective study. Br J Sports Med. 2003; 37(2):149-153.

  8. Kayser R, Mahlfeld K, Heyde CE. Partial rupture of the proximal Achilles tendon: a differential diagnostic problem in ultrasound imaging. Br J Sports Med. 2005;39:838-842.

  9. Dong Q, Fessell DP. Achilles tendon ultrasound technique. Am J Roentgenol. 2009; 193(3): W173-W173.

  10. Rudy CC, Thompson JA, Bengtzen RR. Ultrasonographic findings of acute Achilles tendon rupture. JETem. 2019; 4(4):V14-16

  11. Atta M, Jafari S, Moore K. Analyzing the Use of Ultrasound: Achilles Tendon Rupture. Open J Emerg Med. 2017; 7(3): 41-47.

  12. Kälebo P, Allenmark C, Peterson L, Swärd L. Diagnostic value of ultrasonography in partial ruptures of the Achilles tendon.  Am J Sports Med. 1992; 20(4): 378-381.

  13. Magnussen RA, Dunn WR, Thomson AB. Nonoperative treatment of midportion Achilles tendinopathy: a systematic review. Clin J Sport Med. 2009; 19(1): 54-64.

  14. Keene DJ, Alsousou J, Harrison P, et al.  Platelet rich plasma injection for acute Achilles tendon rupture: PATH-2 randomised, placebo controlled, superiority trial. BMJ. 2019: 367:l6132

  15. Maffulli N, Peretti GM. Surgery or conservative management for Achilles tendon rupture?. BMJ. 2019; 364:k5344.

UltrasoundLauren McCaffertypocus, ultrasound, msk ultrasound