A Funhouse Mirror: Muscular Co-Contractions as a Reflection of a Spontaneous Aberrant Regeneration of the Brachial Plexus Injury in the Adults: Anatomical Background, an Attempt to Classify and their Clinical Relevance within the Reconstruction Strategies

A certain number of spontaneously recovering birth injuries to the brachial (BPI) plexus are known to be accompanied by muscle co-contractions (Co-Cs). The process of aberrant spontaneous regeneration contributes to the appearance of this phenomenon. Treatment strategies are mostly narrowed down to temporarily “switching off” the antagonist, allowing the agonist to perform. Less is known about the incidence of BPI-associated Co-Cs in adults (a-BPI), the control of which mainly presumes the extrapolation of a treatment strategy that has been shown to be effective in infants. Nowadays, surgical reconstruction of independent elbow flexion at BPIs relies heavily on redirection (transfer) of nerves that produce their own Co-Cs. These induced Co-Cs could potentially be reduced. Selecting the appropriate nerve transfer strategy (when the donor pool is narrowing), with its potential impact on the already complex and intricate global and segmental biomechanics of the upper extremity, becomes challenging. The chapter presents the anatomical background for the occurrence of muscular Co-Cs, a work on clinical classification of both regeneration associated and induced Co-Cs, possible surgical strategies, their benefits and limitations, in the presence of regeneration-associated muscle Co-Cs at a-BPI and clinical examples.