Diagnosis and Treatment

The diagnosis and treatment of injuries to the UCL involves the following:

Examination

Examination of the injured thumb should always be preceded by examination of the normal uninjured thumb. Administration of a local anaesthetic facilitates the clinical assessment.

Normally there is some laxity in the UCL of 15 degrees (+/-5 degrees), but little variability from left side to right side. Pain, swelling, tenderness and joint stiffness localised to the ulnar side of the MCP joint are all likely to be present.

Delayed presentation may be associated with considerable pain, local swelling and tenderness, which may make clinical examination difficult. It is, however, useful to identify the point of greatest tenderness.

A palpable lump or fullness on the ulnar side of the MCP joint may represent an avulsion fracture or a Stener lesion [2].

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A Stener lesion is a palpable lump on the ulnar side of the MCP joint of the thumb. It signifies a ruptured and retracted UCL with its proximal stump separated from its distal stump by the interposed adductor pollicis aponeurosis.

Radiographs

Before stress testing the UCL of the thumb, it is advisable to obtain radiographs.

In the presence of a fracture, treatment can be based on the position of the thumb and displacement of the fracture, instead of stress testing [2].

Stress testing

In the absence of an associated fracture, stress testing of the ulnar stability of the thumb MCP joint can be performed in full extension (accessory UCL) and 30o flexion (UCL proper), since the UCL proper is under maximal tension in this position.

Care is needed while stress testing, since too vigorous an examination carries the risk of conversion of an undisplaced UCL rupture into a Stener lesion, or may displace a previously undisplaced fracture [2].

In patients with a partial UCL tear, the MCP joint should be either stable, or minimally lax in both flexion and extension, when the proximal phalanx is stressed radially. The presence of a distinct end point to the opening of the joint to radialward stress suggests an incomplete tear of the UCL [3].

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UCL laxity of over 35o in extension and over 15o in 30o MCP joint flexion, in comparison to the contralateral side on stress testing, are considered diagnostic of a complete rupture of the UCL [3].

Ultrasound

Ultrasound scanning has been shown to be of value in the diagnosis of UCL injuries of the thumb.

Ultrasound has been shown to improve the positive predictive value of clinical examination alone from 80% to 94% in a study undertaken in a British ED.

Other options include stress radiography and arthrography.

Referral to a hand clinic

Indications for referral to a hand clinic are:

• Stener lesion
• Complete rupture of the UCL
• Displaced, rotated or large fracture fragment of the base of the proximal phalanx bone
• Subluxation or instability of the MCP joint
• Ongoing uncertainty of the severity of the UCL rupture or Stener lesion

Conservative treatment

For incomplete UCL tears the authors preferred treatment is by immobilisation in a short thumb spica cast for four weeks to allow the ligament to heal. Thereafter, the cast can be discarded in favour of a short thermoplastic splint.

Supervised mobilisation is commenced at four weeks with all splints discarded after six weeks. Patients should avoid stressful activities with the injured thumb for 10-12 weeks [3].