Lesion Mechanisms

Between August, 1975, and July, 1989, we performed 386 operations for traumatic lesions of the brachial plexus and were able to do follow-up reviews on 262 of them between 1975 and 1985. Eighty-three percent of these cases were victims of motorbike accidents.

When a biker crashes into an obstacle, he is thrown from his bike; the shoulder is forcibly jerked down while the cervical spine flexes in the opposite direction, and the brachial plexus is thus put under great tension. This explains the severity of the lesions, which are most often proximal ruptures of the plexus or even intradural avulsions of the roots.

The severity of the lesions was considerable: 67% of the patients in our series presented intradural avulsions bearing on more than three roots. The most frequently involved were the C6, C8, and TI roots.

The patients were young: 50% were under 20 and 70% under 30 years old. The wearing of a helmet, as required by law, has apparently brought about an increase in the severity of brachial plexus lesions. The weight of the helmet augments the liberation of kinetic energy at the instant of the crash. The victim has better protection against catastrophic intracranial lesions, but this protection is offset by more severe plexus lesions.

In our study, we found that 67% of the lesions were essentially supraclavicular, 9% were retroclavicular, and 14% were infraclavicular. Extended lesions were observed in 10% of the cases; they are severe and difficult to assess. For this reason, we recommend complete surgical exploration of the plexus whenever the preoperative evaluation gives insufficient or ambiguous results. Repairing an obvious proximal lesion and neglecting an attendant distal lesion (or vice versa) would nullify any benefit derived from surgery. Supraclavicular lesions are produced by the lesion mechanism as described above. Infraclavicular lesions usually occur in bikers who saw the crash coming and had the good reflex of placing the arm up and forward with the elbow flexed to protect the face with the forearm. In this position, the clavicle and the pectoralis minor muscle act as a reflection pulley, which explains why the brachial plexus ruptures distally. This lesion mechanism, however, brings with it arterial ruptures and sometimes rupture of the pectoralis minor muscle at its origin on the corticoid.

Victims of motorbike accidents are often polytraumatized and have lower limb and forearm fractures plus cranial, thoracic, or other traumas.

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