Master instructors from the Musculoskeletal POCUS Workshop at SONIC 2022, share their top tips for the stations they taught.
Knee Effusion & Tendons
By Dr Stephen Risson
Scan the achilles tendon with the patient prone
Use dynamic dorsiflexion of the foot to demonstrate subtle achilles tendon tears
Beware of anisotropy. Ensure that the ultrasound beam is perpendicular to the tendon fibres
Identify the patella and quadriceps tendon as landmarks prior to looking for knee joint effusions
By Lynne Johnson
Have patients prone with feet hanging off the bed
Use high frequency linear array probe and use lots of gel with dorsiflexion of the foot if possible
Scan in the longitudinal plane from calcaneal insertion to musculotendinous junction. Also evaluate in the transverse plane in the same manner. (be aware of anisotropy)
Look for signs of tendonosis (thickened tendon with hypoechoic areas)
If a tear is suspected, perform the Thompson test or passively move the foot with the probe longitudinally over the tear to assess the retracted ends of the tendon. Be aware the hemorrhage, fluid or scar tissue may be present in the gap
Intercostal scanning may be required for the IVC identification. The IVC should be identified in the transverse plane in the mid axillary line and then rotate the transducer in order to see it in the long axis
Measurement of the IVC with calipers or M-mode is difficult due to the motion of the IVC. Better to gain experience and eyeball 'full' and 'empty'
Skin & Soft Tissue Abscesses
By Dr Nadi Pandithage
1 Don’t miss deeper lesions - use the curvilinear probe to exclude
2. Don’t mistake a lymph node for an abscess
3. Use colour to check vasvularity
4. Look for compressibility and posterior acoustic enhancement
5. Don’t forget to look in 2 planes and measure
6. Recognise gas and risk of necrotising fasciitis
7. If in doubt compare to other side
Skin & Soft Tissue Abscesses
By Dr Jon Theoret
1) “Cobblestoning” only indicates the presence of fluid in the subcutaneous tissue. Infection will look the same as lymphoedema.
2) Always perform a Colour Doppler evaluation of a suspected cavity before incising it - a pseudoaneurysm will have internal flow, but an abscess will not!
3) Measure Optic Nerve Sheath Diameter (ONSD) 3 mm behind the retina. ONSD > 5.5 mm correlates to ICP > 21 mmHg
4) Dynamic guidance for LP is difficult and probably not helpful. Static guidance can help estimate the likely depth of the ligamentum flavum. You can adjust your needle length based on this information!
Sternum & Rib Fractures including Serratus Anterior & Erector Spinae Blocks
By Dr Georgia Livesay
I use US for rib fracture identification in patients where I can’t see anything on CXR, I’m not concerned enough to CT but a diagnosis is nice for patients and helps reassure. Doesn’t really change management.
Sternal fracture identification is helpful in those you aren’t otherwise planning to CT scan as it is a measure of mechanism and may change your mind on the CT.
Serratus Anterior Block: in-plane approach best
Can use anterior approach to block early while patient still in spinal precautions, provided you can abduct the arm on that side
Can use posterior approach with patient lying on their side if shoulder/ clavicle injury prevents arm abduction (but obviously need to clear C spine first)
If fascial plane isn’t obvious, look for the contrast between lat dorsi muscle fibres in cross-section and serratus anterior parallel fibres
Advance needle a little beyond fascial plane and get assistant to apply gentle pressure as you slowly withdraw: the fascial plane will “give” (a bit like doing an epidural) and you will see the hydrodissection separate the two muscles
Erector Spinae Block: in-plane approach best
Easiest to do with patient sitting with arms over table or pillow (like epidural), but can do with them lying on their side or semi-prone
To avoid intra-muscular injection, advance needle until just touches the transverse process, then withdraw fractionally and look for leaf-shaped appearance of fluid as the hydrodissection separates the facial planes
Sternum & Ribs
By Dr Allan Whitehead
1. Long axis on sternum and ribs works best. Sternum US better than Xray and better than CT
2. Sternal US is useful when CT not required eg isolated chest injury, low speed mechanism eg fell over, punch, kick etc together with extended/lung part of eFAST
3. Usefulness of rib US not so clear - maybe where there is delay to CT in suspected several rib #s with view to follow-up analgesia such as Serratus Anterior Plane (SAP) Block