Postoperative treatment of flexor tendon injuries is done by dynamic mobilisation. Most treatment regimes include all digits in the mobilisation as they move in a synergistic motion. Four weeks the patients are treated in a "Kleinert" splint followed by two weeks in a so-called “wrist-band’’. Practically this means that only the extensors have been utilised actively. At six weeks the splints are removed and the patients are encouraged to engage in active movement. At this time patients report initial clumsiness in task performance which is not explained by stiffness of the fingers. In this Positron Emission Tomography (PET) study we report the effect of prolonged functional immobilization on the cerebral organization subserving movement of the hand.

Patients and methods:

Regional increase of cerebral perfusion was used as indicator for local neuronal activation and measured with oxygen-15 labelled water at the two stages. The first study was performed at the moment when treatment with the traction device ended. The second study followed 6-8 weeks later. In both studies, movement related activation was established by comparing 6 scans acquired during hand movement with 3 scans made during a resting state (3 patients with a left-hand lesion were studied, PET analysis was done by Statistical Parametric Mapping). During the 90 seconds scanning period, patients listened to randomly presented beeps (20 per min). In the movement condition they responded to each beep by making 2 flexion movements with the fingers of the treated hand with the wrist in a neutral and supported position. In the control condition, they only listened to the beeps.

Results:

In all movement conditions activation of the contralateral sensorimotor cortex and ipsilateral cerebellum were present. In the initial study, movement-related responses in the sensorimotor cortex were larger, and additional activation of the parietal cortex was present. The latter may indicate an increased demand on body scheme representation needed for instructing the appropriate parts of the hand to move. In the second study, performed 6-8 weeks later, additional activation of the striatum suggests that simple movements have been learned again.

Discussion/conclusion:

The current study demonstrates that during the rehabilitation of flexor tendons reversible cerebral changes occur in programming movement. It is important that physicians involved in treating these injuries be aware of this phenomenon. At the same time these results may be yet another argument to support active flexor rehab programs. Future treatment regimes may include ‘motor re-education’.