Introduction

In literature there are few cases reported of AMSI, only patients complaining shoulder pain after a standstill period. One of the most frequent causes of AIOS is posterior-superior impingement (PSI).

Case Report

A 42-year-old male, manual worker comes to our clinic complaining chronic dominant shoulder pain. Nor history of fractures, neither dislocation. His pain did not improve nor after infiltrative therapy, neither after physical therapies. At clinical examinations, no deformities are reported, and ROM overlap the contralateral side. No neurological deficits or muscular atrophy is found. Neer, Howkins and Jobe test are positives [2].

There is no sign of shoulder instability. Shoulder pain occur when the arm is in abduction and retropulsion, related to the repetitive overhead microtraumas. MRI shows blurred T2 hyperintense-signal area relatable to bone oedema in the posteroinferior side of the humeral head, which also appears to be disrupted (Figure 2), anterior paralabial cysts (Figure1) and supraspinous, disrupted (Figure 3). MRI shows an AIOS pattern of micro instability due to repetitive traumas in overhead workers.

Figure 1: Paralabial cyst in T2-w MRI.

Figure 2: T2-w MRI bone edema.

Figure 3: T2-w MRI, Disomogeneus area in T2-W MRI.

Arthroscopy was performed in lateral position. Through posterior and lateral arthroscopic access, a complete rupture of supraspinatus and fibrillar connective degeneration in near bone insertion sutured using anchors. Across anterior-superior, a degenerative tear of medial glenohumeral ligament was sutured using a soft anchor.

After a 3-months follow-up pain improved until a full recovery, with no residual signs of impingement or stiffness.

Discussion

The presence of paralabial cyst remains a controversial topic, however it is associated with instability and rim repair leads to resolution of the instability.

Savoie FH, et al. shown that microtrauma in abduction and external rotation can lead to the detachment of the medial glenohumeral ligament [3]. Jobe CM reported that a recurrent abduction and external rotation movement leads to the weakening of the anterior-inferior translation of the humeral head [2]. Burkhart SS, et al. showed that abduction and external rotation might stress the bicipital anchor to the posterior glenoid labrum [4].

Internal impingement might progressively worse due to the repetitive stretching of the anterior structures [5,6]. This theory of anterior micro instability aggravating internal impingement lent credence initially to treating this problem using anterior reconstruction, although the results of this treatment for throwing athletes or overhead manual workers were unpredictable.

The base mechanism is still a debated argument; however, AIOS symptoms overlap SLAP isolated lesions.

Conservative treatment is an option in shoulders with minor structural abnormalities and limited pain. Surgery indicated in cases with rotator cuff lesions and glenoid labrum lesions, such as in the patient we reported [7-9].

Clinical examination, history and imaging can lead to AIOS diagnosis, but in most cases, diagnostic arthroscopy is gold standard, especially in overhead manual workers. Repairing multiple lesions improve pain even in presence of initial stiffness.

References

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