Ruptured ‘Baker's-type cyst’ of the arm—a case study

E. Roddy, V. Lim1, K. J. Fairbairn2 and I. Pande3

Department of Rheumatology, Derbyshire Royal Infirmary, London Road, Derby DE1 2QY,
1 Rheumatology Department, Leicester Royal Infirmary, Infirmary Square, Leicester LE1 5WW,
2 Department of Radiology and
3 Department of Rheumatology, Nottingham City Hospital, Hucknall Road, Nottingham NG5 1PB, UK

SIR, In rheumatoid arthritis, involvement of the tendons and bursae in the shoulder region is a common finding. Rupture of the long head of biceps tendon is classically recognized by the contraction of the belly of the biceps into a prominent lump on active flexion of the elbow, the so-called ‘pop-eye’ sign. Subacromial bursitis is usually secondary to impingement and presents with pain around the shoulder. We report a case in which rupture of the long head of biceps tendon and subacromial bursitis presented as a soft tissue mass on the anterolateral aspect of the left upper arm in a patient with rheumatoid arthritis.

A 58-yr-old lady with longstanding rheumatoid arthritis presented with a 1 week history of pain in her left anterior upper arm. Over the previous 3 days she had also noticed the painful area becoming swollen and weakness of the arm. There was no history of trauma or overexertion of her arms. Her arthritis had been well controlled on leflunomide and she was systemically well.

Examination revealed a diffuse, soft, tender swelling overlying the belly of the biceps anteriorly. The swelling was more diffuse than that classically seen in a ruptured tendon of the long head of the biceps. There was weakness of left elbow flexion and supination and left shoulder flexion. Examination of the ipsilateral shoulder joint was unremarkable. There were no signs of a painful arc or impingement.

C-reactive protein and erythrocyte sedimentation rate were elevated at 77 mg/l and 105 mm/h, respectively. The total white cell count was 11.1x109/l with a normal differential count and the platelet count was 544x109/l.

Ultrasonography showed a large fluid collection in the anterior aspect of the arm with a thin neck proximally (Fig. 1Go). There was a large distended subacromial bursa extending below the deltoid, the bicipital groove was empty and the rotator cuff not visualized (Fig. 2Go). Despite the appearance on ultrasonography, attempted aspiration of the subacromial bursa was unsuccessful.



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FIG. 1. Ultrasound showing fluid collection in anterior aspect of the arm.

 


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FIG. 2. Ultrasound demonstrating enlarged subacromial bursa and empty bicipital groove.

 
Aspiration of the arm swelling yielded 45 ml of clear, straw-coloured, synovial-type fluid and the patient felt more comfortable after the procedure. Culture of both fluid obtained on aspiration and blood was negative.

Magnetic resonance imaging performed 2 weeks later confirmed rupture of the long head of biceps tendon and a massive rotator cuff tear. The fluid collection on the anterior aspect of the arm was reduced, but there was also some fluid deep to the muscle sheath of brachialis. The subacromial bursa remained enlarged containing pannus and rice bodies (Fig. 3Go) in keeping with rheumatoid disease, although rice bodies are also seen in tuberculous arthritis and synovial osteochondromatosis [13].



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FIG. 3. MRI findings. Enlarged subacromial bursa containing rice bodies.

 
Rheumatoid arthritis is characterized by inflammation of tendons and bursae in addition to synovial joints. Involvement of both articular and peri-articular tissues in the shoulder region is common [4]. Studies employing ultrasound and magnetic resonance imaging have demonstrated the occurrence of subacromial bursitis and involvement of the rotator cuff and biceps tendons in patients with rheumatoid arthritis [58]. The occurrence of bilateral subacromial bursitis in rheumatoid arthritis without significant glenohumeral joint disease is also described [9].

We describe a patient with rheumatoid arthritis who presented following the rapid onset of a fluid-filled soft tissue swelling on the anterior aspect of the upper arm. She was found to have chronic rotator cuff disease, a large subacromial fluid collection and an acute tear of the long head of biceps tendon. We hypothesize that with the tear of the long head of biceps tendon and its synovial sheath, fluid from the subacromial bursa tracked down into the anterior compartment of the upper arm manifesting clinically as a soft tissue mass, analogous to a ruptured Baker's cyst. Subacromial bursitis mimicking a soft tissue tumour and presenting as a mass around the shoulder is described [3, 10], but the masses described in these reports were more proximal (shoulder region) to that seen in our patient (upper arm). Furthermore, coexistent rupture of the subacromial bursa and the long head of biceps presenting as a diffuse soft tissue mass in the upper arm is not described in the rheumatological literature.

This case illustrates an unusual presentation of subacromial bursitis and rupture of the long head of biceps tendon and we suggest that this should be included in the differential diagnosis of a soft tissue mass in the upper arm, especially in a patient with rheumatoid arthritis.

Notes

Correspondence to: E. Roddy. E-mail: edroddy{at}doctors.org.uk Back

References

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Accepted 9 October 2002





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