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Arthrocentesis of the Foot

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Authors

Miguel F. Agrait González MD FACEP, FAAEM, CAQ-SM
Assistant Professor of Emergency Medicine Ponce Health Sciences University
San Lucas Episcopal Hospital Emergency Medicine Residency
Ponce, PR
Sports Medicine Director Pravan Health Clinic
San Juan, PR

Summary

  • This chapter reviews 1st metatarsophalangeal (MTP) Joint Arthrocentesis as well as arthrocentesis of other MTP Joints and Interphalangeal Joints

Introduction

  • Joint fluid aspiration with synovial fluid analysis is the most important modality used to diagnose the cause of an acutely painful, effused joint.
  • Whenever possible, the procedure should be done with the aid of ultrasound which has demonstrated greater success rates in both aspiration and therapeutic injection when compared to palpation guided techniques.
  • 1st MTP joint pain will be a common presentation to the ED, most commonly as a result of gout (sometimes referred to as podagra).
  • Arthrocentesis can be used both diagnostically and therapeutically in these cases by performing aspiration of the inflamed joint and, in certain cases, the joint can be injected with anesthetic and/or corticosteroids for pain control.
  • Septic arthritis of the MTP joint should also be considered in the appropriate clinical scenario and arthrocentesis must be performed if infection is suspected.
  • There are currently no clinical, radiographic or laboratory findings which are sensitive enough to rule out a septic joint without performing arthrocentesis and joint fluid analysis.

Anatomy

  • The bony foot is made up of the talus, calcaneus, tarsus (navicular, cuboid and cuneiforms), metatarsals and phalanges.
  • The metatarsophalangeal joint of greatest interest is the 1st MTPJ, as it is the largest and most often associated with pathology (black circle)
  • The remaining MTP and IP joints are small and less commonly require aspiration
Bones of the Foot Anatomy
Bony anatomy of the foot. The metatarsophalangeal joints (blue), 1st MTPJ (black circle) and interphalangeal joints (red, green) are marked.[1]Image courtesy of HSS.edu, “Hallux Rigidus (Stiff Big Toe)”

Ultrasound Evaluation

  • High frequency (5-10 MHz) linear transducer will be used
    • If available, consider the small footprint linear transducer (aka hockey stick) which uses a higher frequency for visualizing very superficial structures
    • Use superficial MSK, vascular or small parts setting for optimal visualization
  • Will help visualize joint and help in directing needle to effusion while avoiding bony structures
  • The transducer will be positioned in long axis (sagittal plane) of the toe and extensor tendon which will be visualized on top of screen
    • For 1st MTP joint in particular, can also perform with a short axis (transverse view) of the joint as described below
  • If an effusion is present, it is easily visualized as a hypoechoic fluid collection within the joint
Normal appearing ultrasound of the 1st MTPJ.
Foot US 1st MTPJ Effusion
Ultrasound with longitudinal view of first MTPJ, showing synovial thickness (white arrow) and effusion (head arrow).
Ultrasound video demonstrating a 1st MTP joint effusion

Procedure

  • Landmark vs. Ultrasound Guided Approach
    • US guided arthrocentesis is generally considered to be superior to palpation guided arthrocentesis of small, medium and large joints.
    • In a study of EM residents, US guidance reduced the number of attempts and time to procedural success with US guidance when compared to landmark guidance[2]Berona K, Abdi A, Menchine M, et al. Success of ultrasound-guided versus landmark-guided arthrocentesis of hip, ankle, and wrist in a cadaver model. Am J Emerg Med. 2017;35(2):240-244. … Continue reading
    • This is known to be true for other joints as well[3]Wiler JL, Costantino TG, Filippone L, Satz W. Comparison of ultrasound-guided and standard landmark techniques for knee arthrocentesis. J Emerg Med. 2010;39(1):76-82. … Continue reading
    • For this reason, only the ultrasound guided approach is described in this chapter.
  • Materials
    • 18 gauge draw needle
    • 1.5 – 2 inch, 25 – 27 gauge needle for local anesthetic administration
    • 1.5 – 2 inch, 21 – 25 gauge needle for aspiration
    • 3 – 5 cc syringe (at least 2)
    • Local anesthetic
    • Sterile equipment (gauze, skin prep, gloves, probe cover, etc)
    • Additional equipment as needed (sterile collection tubes, culture bottles)
    • Skin marker (optional)
    • Other medications (optional)
      • Corticosteroid (triamcinolone, methylprednisolone, etc)
      • 0.5mL of steroid generally enough for these small joints

1st MTP Joint

  • General
    • Position
      • The patient is supine or seated
      • The foot is plantarflexed against against the stretcher or exam table
      • Can have toe slightly off bed if manipulation is needed
      • Can have assistant flex toe 15-20 degrees and provide traction to help increase joint space and improve visualization
    • Ultrasound: The linear transducer is used
Demonstration of foot positioning prior to procedure. Note the toe is off the bed with traction applied.
  • Needle Out-of-plane Approach
    • Ultrasound
      • Position ultrasound in long axis to digit, parallel to the toe and extensor hallucis longus (EHL) tendon which will be located on top of screen
      • Visualize joint and effusion and position in middle of screen
      • Mark needle insertion point with skin marker
    • Anesthetize skin of medial aspect of MTP joint with lidocaine or ethyl chloride spray
Transducer position over 1st MTP in long axis.
    • Procedure
      • Insert needle medial to lateral out of plane guided directly into joint
      • Needle will be perpendicular to ultrasound transducer
      • Only needle tip will be visualized in joint space
    • Aspirate if necessary or inject up to 1ml total anesthetic/corticosteroid combination
    • Retract needle and provide local pressure for hemostasis
Transducer and needle position for out of plane technique.
Ultrasound demonstration for out of plane technique.
  • Needle In-Plane Approach
    • Ultrasound
      • Position ultrasound in long axis to digit, parallel to the toe and extensor hallucis longus (EHL) tendon which will be located on top of screen
      • Visualize joint and effusion and position in middle of screen
      • Rotate transducer 90 degrees to visualize joint in transverse orientation
        • Can scan cranial to see MT head, caudal to see proximal phalanx
        • Want to see joint space between the two bony structures
      • Mark needle insertion point with skin marker
    • Anesthetize skin of medial aspect of MTP joint with lidocaine or ethyl chloride spray
    • Procedure
      • Insert needle medial to lateral in-plane guided directly into joint
      • Full length of needle will be visualized
    • Aspirate if necessary or inject up to 1ml total anesthetic/corticosteroid combination
    • Retract needle and provide local pressure for hemostasis
Ultrasound demonstration for in plane technique.
Ultrasound demonstration for in plane technique.

Interphalangeal Joint, 2nd-5th MTP Joints

  • Position
    • The patient is supine or seated
    • The foot is plantarflexed against against the stretcher or exam table
    • Can have toe slightly off bed if manipulation is needed
    • Can have assistant flex toe 15-20 degrees and provide traction to help increase joint space and improve visualization
  • Ultrasound
Ultrasound demonstration for in plane technique.
    • The linear transducer is used
    • Position ultrasound in long axis to digt, parallel to the toe and extensor tendon which will be located on top of screen
  • Anesthesize skin immediately medial or lateral to midline of toe and extensor tendon with lidocaine
  • Insert needle dorsally medial or lateral to ultrasound transducer in parasagittal orientation orienting towards joint
    • Avoid inserting through extensor tendon
    • Needle will be partially in plane, full length of needle will not be visualized
  • Aspirate if necessary or inject up to 1ml total anesthetic/corticosteroid combination
  • Retract needle and provide local pressure for hemostasis

Pearls & Pitfalls

  • Crystal arthropathy and septic arthritis commonly coexist and the presence of crystals on joint fluid analysis does not eliminate the possibility of joint infection
  • Arthrocentesis of small joints can be technically challenging. Fluid aspiration is often limited so proceduralists should try to optimize joint traction and needle position to maximize aspirant volume.
  • Avoid intratendinous injection or inserting needle through tendon whenever possible
  • Use an assistant to flex joint slightly (15-20 degrees plantar flexion) and provide traction, this will significantly increase your target size and joint space as visualized on US
  • Small joints will only hold ~1mL of fluid, do not try to inject more volume

References

References[+]