ANTERIOR IMPINGEMENT, THE NEUROGENIC HYPOTHESIS

Abstract

Hypothesis: For Neer, humeral head ascension is caused by anterior impingement. The anatomic or ischemic factors favoring anterior impingement are well known, but have not been shown to have a determining effect. Our work on the comparative action of the rotator cuff muscles to lower the humeral head (1992), led to the conclusion that the infraspinatus muscle plays a highly dominant role. The frequent association of anterior impingement and a history of cervical pain might suggest that neurogenic paresia of the infraspinatus might be involved with the impingement effect as can be observed in intermittent paresia of the lower limbs revealing a narrow lumbar canal. Since this hypothesis was put forward, we have made converging observations in a prospective study of 200 cases.

Obervations:

1. When patients with anterior impingement were questioned, 80 were found to have a history of cervical pain which was confirmed radiographically and/or on computed tomography (CT).

2. Physical examination of the cervical spine revealed pain at pressure on the anterolateral aspect of the C4, C5, and C6 vertebrae, always homolateral to the impingement. Search for this sign has thus become part of our routine examination and, according to Maigne, confirms the vertebral origin of peripheral pain. We found it to be absent in anterior impingements caused by trauma in young subjects, and to be inconstant in traumatic anterior impingements observed in patients aged over 55 years.

3. After cervical arthrodesis for cervicobrachial pain, we observed five cases of progressive anterior impingement requiring decompression. In their series of 76 cervical arthrodeses for cervicobrachialgia, Hawkins et al on observed 13 cases of proven anterior impingement. They concluded there must be a relation between these two conditions.

4. Golg et al. provided a decisive contribution to the theory when the discovered that in anterior impingement patients, rotator cuff muscles exhibit specific histological markers of muscle denervation.

Conclusion: Most cases of degenerative anterior impingement result from atrophy of the rotator cuff muscles arising because of a cervical canal syndrome.