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Navicular bursa: injection

ISSN 2398-2977

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Introduction

  • Intra-articular analgesia of the navicular bursa can help to differentiate navicular pain from that of other parts of the palmar foot.

The significance of a positive response to analgesia of the navicular bursa has not been established.

  • Injection of various medications into the bursa has been advocated as a treatment for navicular syndrome and other pathology within this anatomical region.
  • Recent techniques have concentrated on a lateral approach to the bursa to decrease iatrogenic damage to the DDFT.
  • Ultrasound guided approaches have recently been validated and offer advantages over radiographic control.

Uses

Advantages

  • Accurate deposition of analgesic/therapeutic agent.
  • Weightbearing or non-weightbearing techniques may be used.
  • Ultrasound-guided techniques allow accurate needle placement without the need for radiographic control.
  • Lateral approaches cause less iatrogenic damage.
  • The 'navicular position' (non-weightbearing) technique:
    • Relaxes the deep digital flexor tendon and opens the bursal space between the tendon and the navicular bone.

Disadvantages

  • Difficult.
  • Multiple techniques described.
  • Some techniques require penetration of the deep digital flexor tendon.
  • Non-weightbearing technique may pose additional hazard to personnel.

Technical problems

  • Sound knowledge of anatomy.
  • Need to adjust positioning according to conformational differences.

Alternative techniques

Time required

Preparation

Procedure

  • Depends on technique used and whether validation of placement of needle in the correct position is used: 5–15 min.

Decision taking

Criteria for choosing test

  • Lameness localized to the foot by clinical signs and/or regional analgesia techniques.
  • Injection of therapeutic agent into navicular bursa.

Risk assessment

  • Iatrogenic damage to DDFT and/or navicular bone or bursa.
  • Introduction of injection into bursa.

Requirements

Personnel

Veterinarian expertise

  • Veterinarians should be experienced in regional analgesia and synovial structure injection techniques.
  • Inexperienced vets should practice the various techniques on cadaver limbs.

Nursing expertise

  • Experience in aseptic preparation and restraint for intrasynovial injection techniques.

Materials required

Ideal equipment

  • Depending on the technique chosen radiography or ultrasonography machines will be required to confirm the correct placement of the needle.
  • An optimal ultrasound probe should have a high frequency (6.5 MHz or greater) and a small footprint (curvilinear).

Minimum consumables

  • Surgical gloves.
  • 18-20 gauge disposable spinal needle (5-8 cm long) and 2-5 ml syringe.
  • Mepivacaine chloride Mepivacaine 3-5 ml is often suggested for the navicular bursa but as little as 1 ml will adequately anesthetize the bursa and adjacent surfaces.
  • 1 ml local anesthetic Anesthesia: local - overview for skin anesthesia.
  • Appropriate dosage of medications such as triamcinolone Triamcinolone, methylprednisolone Methylprednisolone and hyaluronic acid Sodium hyaluronate.

Preparation

Pre-medication

If the injection is part of a diagnostic lameness work-up then the use of sedation compromises the assessment of the post block lameness.

Site preparation

  • Fine clip, surgical scrub and aseptic preparation of injection site and whole of distal pastern region up to the level of the fetlock.
  • Routine sterile techniques should be used when handling the needles, syringes and medication/local anesthetic.

Other preparation

  • It may be useful to mark the ‘navicular position’ on the hoof wall with a tack or adhere a small coin. The position is 1 cm distal to the coronary band and halfway between the most dorsal and palmar aspect of the hoof wall.
  • If an ultrasound guided technique is to be used then examination of the limb, prior to the injection being carried out, is essential to confirm that the bursa is distended beyond the margins of the DDFT, either laterally or medially:
    • The technique can be carried out in a weight-bearing position resting on a wooden block, or, with the foot resting on a Hickman block in a 60-degree flexed position. The latter increases the chance of retrieving synovial fluid on entering the bursa.
    • The probe is placed proximal to the heel bulbs, on the distal palmar pastern, and images obtained in longitudinal and transverse planes.
    • The bursa should be identified in the midline in a sagittal plane before the probe is swept laterally and medially at the same level.
    • Identification of the effusion laterally or medially needs to be confirmed in a transverse orientation, deep to the DDFT and superficial to the collateral sesamoidean ligament.
    • Once the bursa is identified, the probe head is covered with a sterile glove and the area re-sterilized.
    • Sterile alcohol is applied to the skin immediately prior to the gloved probe being re-applied to increase probe contact and improve image quality.

Restraint

  • Support foot in a Hickman block, ie toe supported such that dorsal foot is vertical and plane of sole is approximately 45° to the ground, for non-weightbearing injection technique.

Technique

Approach

Step 1 - Position the foot

  • For the 'navicular position' technique, place the toe in a Hickman block, such that the metacarpophalangeal and distal interphalangeal joints are flexed.
  • Infuse the skin at the injection site (between blubs of heel immediately above coronary band) with 1 ml local anesthetic Anesthesia: local - overview.

Core procedure

Step 1 - Navicular position technique

  • The navicular position is the point on the lateral hoof wall, 1 cm distal to the coronary band, and halfway between the most dorsal and most palmar aspect of the coronary band.
  • Insert the needle midway between the heel bulbs, proximal to the coronary band.
  • Advance it in the sagittal plane towards the point bisecting the sagittal plane and the long axis of the navicular bone, until significant resistance is encountered.

The long axis of the navicular bone is assumed to be the connecting line between the 'navicular position' points on the lateral and medial hoof wall.

  • When the needle contacts bone the injection can be made easily (2-3 ml anesthetic solution and 0.5-1 ml radiographic contrast medium). In a regular-sized foot and using an 8 cm spinal needle, the bone should be contacted approximately 60% along the length of the needle. It should be possible to aspirate the injected contents back into the syringe if within the bursa.
  • Radiographic examination: identification of contrast medium in bursa confirms successful bursal injection Navicular bursa: contrast study 01 - LM radiographNavicular bursa: contrast study 02 - LM radiograph.

Step 2 - Alternative techniques (weightbearing)

Correct placement of needle using any of these techniques will be influenced by variations in conformation.

Distal palmar approach parallel with the coronary band

  • Advance the needle in the sagittal plane of the limb, parallel with the coronary band, until significant resistance is encountered.

Distal palmar approach parallel with the sole

  • Insert needle midway between the heel bulbs, immediately proximal to the coronary band.
  • Advance the needle dorsally in the sagittal plane of the limb, parallel with the solar surface of the foot, ie horizontally, until significant resistance is encountered.

Proximal palmar approach

  • Insert the needle into the hollow of the heel and advance it dorsally in the sagittal plane of the foot at an angle of 30° to the horizontal, until significant resistance is encountered.

Lateral approach

  • Insert the needle just proximal to the lateral cartilage of the third phalanx, between the lateropalmar border of the second phalanx and the lateral border of the deep digital flexor tendon. The limb is placed on a block in a standing position.
  • Advance the needle distally at an angle of 45° to the horizontal in the frontal plane of the limb until significant resistance is encountered.
  • This technique uses radiographic control to confirm correct positioning. Multiple radiographs may be required with re-positioning attempts increasing exposure to radiation for personnel. Attempts at re-positioning also increase the chances of iatrogenic trauma and prolongs the time required for the technique.

This latter technique avoids penetration of the deep digital flexor tendon.

Step 3 – Ultrasound-guided technique

  • The foot is placed on a wooden block with the axis of the limb behind the vertical either in a 60-degree flexed position or weight-bearing depending on the clinician’s preference.
  • Once the navicular bursa is identified on ultrasound there are few significant overlying structures, and it is possible to introduce a needle laterally or medially (depending bursal distension on the ultrasound) through the skin at an oblique angle and directly into the bursa under ultrasound guidance:
    •  An 8 cm 18-20-gauge spinal needle is suitable.
    • The needle is placed abaxial to the probe in the plane of the ultrasound beam.
    • Once it is identified on the ultrasound image, as it penetrates the skin, it is repositioned as necessary in real time so that it is aligned with the bursal distension and followed into the bursa.
    • A small volume of fluid should be injected under direct visualization to confirm intrabursal location.
    • Fluid may also be aspirated if necessary.
  • The local anesthetic or medication is injected.
  • The needle is removed.
  • This technique has the advantage of avoiding damage to the DDFT, less attempts at re-positioning, less time to carry out the centesis, no need to use contrast agents, and no exposure of personnel to radiation.
  • It is essential that good ultrasound images are obtained if this technique is to be successful. If they are not possible then another technique should be used. In a recent paper, 78% of cases were successfully aspirated with all unsuccessful cases being due to poor ultrasound imaging.

Aftercare

Immediate Aftercare

Monitoring

  • After the technique is carried out, the case should be monitored closely for 48 h for any increase in lameness suggesting reaction to the injection or iatrogenic infection.

Wound protection

  • After removal of the needle for injection, the skin should be wiped with a sterile swab soaked in sterile surgical spirit before dressing with a sterile gauze or dressing, Kling bandage and Vetwrap.
  • This can be removed after 48 h.

Potential complications

Long term Aftercare

  • Determined by clinical condition.

Outcomes

Complications

  • Iatrogenic damage or infection in the bursa or surrounding structures.
  • Injection of peribursal soft tissues, distal interphalangeal joint, and distal deep digital flexor tendon sheath is increased in those cases where they are distended and using the lateral approach under radiographic control.

Reasons for treatment failure

  • Needle not placed in bursa.
  • In ultrasound-guided techniques, poor acquisition of images significantly deteriorates the chances of accurate centesis.
  • Incorrect diagnosis.

Prognosis

  • Determined by clinical condition.

Further Reading

Publications

Refereed papers

  • Recent references from PubMed and VetMedResource.
  • Nottrott, K et al (2017) An ultrasound-guided, tendon sparing, lateral approach to injection of the navicular bursa. Equine Vet J 49 (5), 655-661 PubMed.
  • Daniel A J et al (2016) An optimised injection technique for the navicular bursa that avoids the deep digital flexor tendon. Equine Vet J 48 (2), 159-64 PubMed.
  • Perrin R et al (2016) Ex vivo assessment of an ultrasound-guided injection technique of the navicular bursa in the horse. Anat Histol Embryol 45 (6), 450-456 PubMed.
  • Labens R & Redding W R (2012) The dilemma of whether to inject the navicular bursa. Vet Rec 171 (25), 641-642 PubMed.
  • Manfredi J M et al (2012) Steroid diffusion into the navicular bursa occurs in horses affected by palmar foot pain. Vet Rec 171 (25), 643 PubMed.
  • Schramme M C et al (2000) An in vitro study to compare 5 different techniques for injection of the navicular bursa in the horse. Equine Vet J 32 (2), 263-267 PubMed.