Cerebral consequences of dynamic immobilisation after primary digital flexor tendon repair

Current treatment protocols for flexor tendon injuries of the hand generally result in an acceptable function, which can be quantified by objective parameters such as range of motion. The latter does not always match the patients' subjective experiences of persisting dysfunction. This raises the question whether changes in the cerebral control of movement might contribute to the perceived deficit. The main objective of the present positron emission tomography (PET) study was to characterise the cerebral responses in movement-associated areas during simple finger flexion immediately after dynamic immobilisation and after a subsequent 6-week period of active training. Ten subjects with flexor tendon injury participated in the PET study. Electromyography (EMG) recordings were made during finger flexion and extension in an additional subject. The main finding was that the (ventral) putamen contralateral to flexor movement was not activated immediately after release from splinting, while such activation reappeared after a period of training. This indicates a temporary loss of efficient motor control of over-learnt movements. The increase of unwanted co-contractions during flexion in a first EMG session, and not during extension, supports a concept of lost skills.