DIAGNOSIS ADVANTAGES OF MSKUS

■ Safe, with no ionising radiation ■ Relatively cheap (can repeat and monitor)

■ Relatively quick to perform ■ Interactive ñ usually patients like it ■ Comparative (split screen on some machines)

■ Real-time dynamic scanning possible

■ Can perform 'needle-guided' interventions

■ Better than MRI for claustrophobic patients

■ 'All in one' - scanner, reporter and clinician

■ Doppler can look for neovascularisation

■ Extended field of view images possible

■ Calipers can measure lesions to within 0.1mm

Figure 3: Common pros and cons of MSKUS

Disadvantages These are summarised in Figure 3. The pri- mary disadvantage is that both the perfor- mance of ultrasound and the interpretation of the images are very highly 'operator dependent'; most well informed authors acknowledge that the 'learning curve to competence level' for a useful spectrum of examinations in MSKUS is long and slow. For example it is one thing to learn how to scan and interpret the easily recognised Achilles tendon and quite another to suc- cessfully interpret dynamic groin scans with its reliance on various soft tissue landmarks in 3-dimensions.

In addition, ultrasound beams cannot pen- etrate bone to any practical useful level, hence this leads to the disadvantage of MSKUS only being able to visualise the periphery of any joint.

Nevertheless,

MSKUS can detect bony erosions, callous (even stress fracture) and other bony swellings such as enthesiophytes and osteophytes; these can be very useful in the diagnostic process.

Artefacts are part and parcel of MSKUS. They take several forms, but the most com- mon one is called anisotropy, and this phe- nomenon is largely unique to peripheral superficial MSKUS.

interpreting reflected sound waves from soft tissue structures. It is important in

www.sportex.net AB Ultrasound works by

Anisotropy: In the left image (A), the probe is held so it is the plane of the biceps tendon fibres, and these show up clearly in transverse section (arrow) On the right image (B), the probe and beam are tilted to be at an angle with the biceps tendon; the anisotropy effect is so pronounced that the biceps tendon appears missing!

Figure 4: Anisotropy 23

MSKUS to achieve maximum echo ampli- tude by angling the beam perpendicular to the structure being investigated. This helps to reduce the appearance of the anisotropy artefact. (11). Poor scanning technique and incorrect interpretation of anisotropy can lead to both false positives and false negatives and these can seriously under- mine the value of MSKUS.

Depending on the level of difficulty of the area being scanned and the experience and skill of the sonographer, MSKUS can mean extending consultations by anywhere between 2 to 10 minutes. If you add an ultrasound-guided intervention, this can add a further 5-7 minutes (approximately). Therefore while there are many advantages

DISADVANTAGES OF MSKUS

■ Operator dependent ■ Long learning curve for competence in scan skills

■ Artefacts common and need correct interpretation

■ Can only visualise the periphery of joints

■ Extends normal consultation time ■ Added PDP commitment ■ US machine impacts on service bud- get

■ If sonographer leaves, scanner may be redundant

to incorporating MSKUS into the tradition- al consultation or treatment process, there is invariably a significant 'time penalty'. This must be factored into the planning and administration of clinics, especially in the early phases of learning when scans take longer. Alternatively, patients may return at a later date for their scan.

Equipment and costs Technical advances in equipment have been fundamental in opening up the use of ultrasound to a broader spectrum of mus- culoskeletal conditions.

Low frequency

probes (around 3-8MHz) are better for deeper structures or thick muscle, and del- icate superficial structures such as tendons and nerves need the higher frequency probes (typically 8-17MHz).

Often the

probe will account for 80-90% of the total value of the scanner package.

Equipment procurement will usually follow on from a solid business plan. This needs to consider individual commitment, profes- sional enthusiasm, clinical needs, protect- ed time and projected costs of equipment, consumables, training and maintenance (12). Pilot projects can utilise redundant 'practice equipment' ñ and often such scan- ners can be negotiated through representa- tives of the major equipment manufactur- ers for free, or for a peppercorn rent, for perhaps 3-6 months. By this time the clin- ician should have a sense of whether they have a knack for scanning and also if they enjoy doing it. My advice would be if you don't find some professional fun in MSKUS, it is probably not for you.

Only a few years ago MSKUS was beyond the capability of portable equipment, and the 'quality image machines' were prohibi- tively expensive (up to £100,000) however