Achilles Paratenon Injection

Other Names

• Achilles Paratenon Injection
• Peritendinous Achilles Injection
• Achilles Peritendinous Corticosteroid Injection
• Achilles Tendon Sheath Injection
• Paratenon Sheath Injection
• Achilles Peritendinous Treatment

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Background

Posterior ankle anatomy: Achilles tendon (Ach), paratenon (P), Kager’s fat pad (KF), plantaris tendon (Pl), sural nerve (Sn), saphenous vein (Sv), flexor hallucis longus muscle and tendon (FHL), tibial nerve (Tn), tibial artery and nerves (Ta), flexor digitorum longus tendon (FDL), posterior tibialis tendon (PT), peroneus longus tendon (PL), peroneus brevis muscle and tendon (PB), Tibia (Tib), and fibula (Fib).

Key Points

• Needle: 25-27 gauge, 1-1.5 inche
• Transducer: high frequency linear arrway
• Avoid injecting directly into the tendon

Anatomy of the Achilles Tendon

• Longest, strongest tendon in the body; 12-15 cm in length, 6 mm in cross section
• The tendon fuses from the distal tendininous components of the soleus and gastrocnemius muscles
• It travels distally, inserting into the posterior surface of the calcaneus
• Approximately 2-6 cm proximal to insertion is an area of relative hypovascularity
• Paratenon: double layered connective tissue membrane
  • Not a true sheath, no synovium
  • Very vascular, provides blood supply to the tendon
• Kagars fat pad separates the anterior Achilles tendon from the flexor hallucis longus
• Retrocalcaneal Bursa lies anterior to the tendon, just proximal to the insertion on the calcaneus
• The long, thin plantaris tendon is found along the medial border of the Achilles in 90% of individuals
• The Sural Nerve and Saphenous Vein are found on the lateral aspect

Palpation Guidance vs Ultrasound Guidance

• You can not reliably inject the paratenon without ultarsound guidance
• One cadaveric study found sonographc injection was 100% accurate
• There are no studies comparing unguided injections

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Indications

• Chronic Achilles Tendinopathy

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Contraindications

• Absolute
  • Anaphylaxis to injectates
  • Overlying cellulitis, skin lesion or systemic infection
• Relative
  • Can be treated with less invasive means
  • Hyperglycemia or poorly controlled diabetes
  • Lack of symptom improvement with previous injection

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Procedure

Paratenonitis: A. Sagittal view of Achilles tendon with paratenonitis (white arrow). B. Short-axis view of Achilles tendinopathy with paratenonitis (white asterisk)

Patient position, transducer position, and needle orientation for short axis, in plane approach

Ultrasound view of short axis, in plane approach. Needle (arrow), paratenon (open arrow), short-axis view of Achilles tendon (asterisk), area of tendinopathy (asterisk).

Patient position, transducer position, and needle orientation for long axis, in plane approach

Ultrasound view of long axis, in plane approach. Needle representation (long arrow), paratenon (small arrows), Achilles tendon (open arrows)

Equipment

• Sterile prep (i.e. chloraprep, chlorhexidine, iodine, etc)
• Gloves
• Needle: typically 21-25 gauge, 1.5 inch
• Syringe: 5-10 mL
• Gauze
• Ethyl Chloride
• Bandage
• Injectate
  • Local anesthetic
  • Corticosteroid
• Sterile probe cover

Ultrasound Findings

• Best visualized in both long and short axis
  • Slight dorsiflexion can add some tension and improve visualization
  • Avoid confusing anistropy of the tendon with pathologic findings
  • Evaluate the full length and width of the tendon
• Normal
  • Normal fibrillar pattern of the tendon
  • Paratenon seen as a slightly more echogenic rim around the tendon
• Common pathologic findings
  • Interfibrillar distance (hypoechoic tendon appearance)
  • Tendon thickening
  • Complete, partial tears and full-thickness partial tears can be identified by gaps or fibrillar pattern interruption
• Paratenonitis
  • Irregular tendon margins
  • Peritendinous effusion
  • Edema of the pre-Achilles tendon fat pad

Paratenon Injection: Short Axis, In Plane

• Patient Position
  • Patient prone
  • Foot hanging off table
• Transducer Position
  • Short axis over the Achilles Tendon
• Needle Approach/ Orientation
  • In plane
  • Lateral to Medial
• Target
  • Anterior to paratenon (between paratenon and posterior Achilles tendon)
• Pearls & Pitfalls
  • Avoid the sural nerve, saphenous vein which are lateral to Achilles tendon
  • If you approach from the medial side, avoid the contents of the Tarsal Tunnel

Paratenon Injection: Short Axis, In Plane

• Patient Position
  • Patient prone
  • Foot hanging off table
• Transducer Position
  • Long axis over the Achilles Tendon
• Needle Approach/ Orientation
  • In plane
  • Proximal to distal
• Target
  • Anterior to paratenon (between paratenon and posterior Achilles tendon)
• Pearls & Pitfalls
  • The entry angle can be challenging, the needle may need to be bent at the hub

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Aftercare

• Motor exam should be intact
• No major restrictions in most cases
• Can augment with ice, NSAIDS
• Can consider Ankle Compression Sleeve after

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Complications

• Infection
• Damage to surrounding tissue

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See Also

Internal

• Procedures Main
• Foot And Ankle Anatomy
• Physical Exam Foot
• Foot Pain Main

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