DIAGNOSIS

BOX 2: THE MOST COMMON SHOULDER PATHOLOGIES WHERE MSKUS CAN BE A USEFUL DIAGNOSTIC AID

■ Rotator cuff tendon tears – partial and complete. Supraspinatus tears are most common, though deep surface infraspinatus lesions may be seen more in throwing sports like cricket, baseball, and javelin/discus (see figure 3)

■ Rotator cuff tendinopathy, including calcific tendinopathy ■ Bursitis and bursal fluid ■ Joint effusion ■ Acromio-clavicular joint lesions ■ Biceps tendon tear or avulsion ■ Pectoralis major tear ■ Ganglion cysts and labral lesions ■ Unstable biceps (tranverse ligament tear) ■ Avulsion fracture ■ Soft tissue lesion

up towards its attachment around the superior glenoid and labrum (see figure 2). When scanned higher up towards the rotator cuff, the biceps normally should be seen sitting between the supraspinatus tendon (laterally) and the subscapularis tendon (medially). This area is generally referred to as the rotator cuff interval and usually measures between 1.0 and 1.4mm (see figure 2).

Each major shoulder tendon structure should be scanned both transversely and longitudinally. The complexity of the shoulder is a good example of why adhering to a commonly accepted protocol is useful. This one joint examination example also serves to highlight how MSKUS requires both a detailed knowledge of functional anatomy and careful examination technique to be a sensitive and specific diagnostic tool for the clinician.

The main findings or pathologies that are sensitive to MSKUS of the shoulder are summarised in box 2.

Other upper limb problems such as enthesopathies at both elbow

FIGURE 3: THE APPEARANCES OF NORMAL AND TORN SUPRASPINATUS TENDONS

DEL SSP HH DEL HH SSP

The above images vividly demon- strate the difference between a normal supraspinatus tendon, with some anisotropy (yellow arrow, top image) and a full thickness tear of the tendon (bottom image).

The

torn tendon is seen retracted away to the right of the screen (white arrow), and in its place is a thin dark, low echo area (red arrow),

often containing a mixture of sero-sanguinous bursal fluid. In freshly torn tendons, this fluid is usually seen to move around in dynamic scanning. With supraspinatus retracted, the deltoid muscle (DEL) is seen to sit directly on the humeral head (HH) (green arrows) - one pitfall for the inexperienced sonographer is to misinterpret the deltoid for the ‘missing’ supraspinatus and report the image as ‘rotator cuff intact’.

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joint epicondyles can be visualised and treated very well. Also, comparative studies of nerves at common points of entrapment or neuropathy are useful in more experienced hands and act as an adjunct to clinical and neurophysiological examination. An example of a Guyon’s canal ganglion cyst is illustrated in figure 1. This particular case is an excellent example of how the addition of MSKUS can help create a one-stop-shop for certain conditions. With the right equipment, MSKUS for forms of upper limb tenosynovitis (such as de Quervain’s), finger tendon structures and carpal tunnel syndrome, also aid the diagnostic process. MSKUS can be used to detect foreign bodies as well, but as this often progresses to minor surgery, its use is probably restricted to GP surgeries and A/E departments. As with other anatomical regions in MSKUS, it is possible to augment the clinical evaluation of soft tissue lumps and bumps with MSKUS scanning. But unless the practitioner has been specifically tutored in this skill, it is recommended that any soft tissue mass uncovered on MSKUS should be referred to a radiologist for further examination, especially if it has a positive signal on Power Doppler.

KNEE AND LEG Away from MSKUS of the shoulder, experience indicates that there is less need for a strict examination protocol. This should be especially so for sonographer-clinicians where the ultrasound scanner is essentially a tool to help focus on a particular area where the pain (or perhaps swelling) is more easily specified by the patient. As long as the examiner knows the anatomy of the area, the generic principles of MSKUS apply, irrespective of what you are scanning (Box 3).

BOX 3: THE GENERAL PRINCIPLES OF MSKUS

■ Check the settings on the scanner and adjust as needed for probe, frequency, depth and focus (and others as required)

■ Make sure you have registered the patient details and labelled the images correctly

■ Look at the structure both longitudinally and transversely ■ Use plenty of US jelly (or even a special US ‘stand-off’ gel pad) especially when the area is very bony and superficial

■ Always watch out for the anisotropic effect and other artefacts

■ Scan with a light touch to minimise patient discomfort ■ Vary probe pressure carefully to see if a superficial lesion is compressible (blood, effusion, bursal fluid) or solid

■ Use Power Doppler when available, especially for soft tissue lump or tendon lesion

■ To help place it in the perspective of other adjacent anatomical structures (or measure a structure larger than the size of the probe) try using the ‘extended field of view’ facility (if available) (see figure 3)

■ Use the electronic scanner callipers to measure and document lesion size and orientation

■ When there is doubt over the clinical significance of a sonographic finding, it is often useful to do a comparative scan of the same contra-lateral structure, using a split screen if available (figure 3). The patient may have exactly the same (asymptomatic?) bursa on the other side!

■ Always consider the addition of dynamic scanning techniques.

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