Imaging Goals

Technique

The basal joint of the thumb or the first CMCJ is best examined with the patient seated opposite and placing the ulnar aspect of their hand against the examination couch (karate chop position) (Fig. 14.1). The probe is placed in the sagittal plane aligned along the long axis of the thumb. The first metacarpal is distinguished from the much shorter tripezium and, from this landmark, the CMCJ is easily found. The tripezium separates the CMCJ from the adjacent scaphoid and scaphotrapeziotrapezoid joint in between. Degenerative changes in these two joints are a common cause of radial-side symptoms. Both are visualized from the sagittal probe position described above and can be injected together, or separately, as symptoms and ultrasound findings dictate.

The first MCPJ is reinforced by collateral ligaments medially and laterally and by a volar plate on the flexor side. Assessment of the UCL of the thumb is a commonly performed examination as this ligament is frequently injured. The injury will be dealt with in detail in a later section; however, the technique for identifying the ligament, its important relationships and the method for stressing the ligament will be covered here.

The UCL is best examined by asking the patient to place their hand palm downwards on the examination couch. For an examination of the right hand, the examiner sits opposite and places the probe in their left hand and takes the painful thumb in their right hand, raising the thumb and hand off the table slightly. The patient’s first proximal phalanx rests on the examiner’s middle finger in a position that allows the interphalangeal joint to be moved by the examiner’s thumb. The examiner’s index finger is placed on the ulnar side of the patient’s first metacarpal (Fig. 14.2). In this position the examiner can use their thumb to gently flex the interphalangeal joint and can use their index finger and thumb combined to induce valgus stress in the UCL.

The imaging goals for patients with UCL injuries are: firstly, to determine if the ligament is torn and secondly, to detect displacement. The ligament is displaced if it lies proximal and superficial to the adductor aponeurosis that overlies it. To make this determination, the aponeurosis must be located first. Flexion of the interphalangeal joint moves the aponeurosis over the UCL. It is seen as a thin line with the ultrasound configuration of a ligament moving to the subcutaneous fat and overlying the UCL. It is usually relatively straightforward to identify whether the ligament lies deep to it or has been displaced proximally. Once a torn ligament and overlying aponeurosis have been detected, the extent of the injury can be classified. This is discussed in more detail on page 158, but simply put, if the ligament is disrupted but remains deep to the aponeurosis, the injury can be treated conservatively. If the ligament is disrupted and has been displaced (called a Stener lesion), surgery may be a preferential form of treatment.

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Disorders of the Elbow: Anterior Disorders of the Ankle and Foot: Lateral Disorders of the Groin and Hip: Paediatric Hip Ultrasound Imaging of Joint Disease Shoulder 1: Supraspinatus Tendon Ankle Joint and Forefoot: Anatomy and Techniques

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