Discrimination of motor imagery-induced EEG patterns in patients with complete spinal cord injury.

EEG-based discrimination between different motor imagery states has been subject of a number of studies in healthy subjects. We investigated the EEG of 15 patients with complete spinal cord injury during imagined right hand, left hand, and feet movements. In detail we studied pair-wise discrimination functions between the 3 types of motor imagery. The following classification accuracies (mean +/- SD) were obtained: left versus right hand 65.03% +/- 8.52, left hand versus feet 68.19% +/- 11.08, and right hand versus feet 65.05% +/- 9.25. In 5 out of 8 paralegic patients, the discrimination accuracy was greater than 70% but in only 1 out of 7 tetraplagic patients. The present findings provide evidence that in the majority of paraplegic patients an EEG-based BCI could achieve satisfied results. In tetraplegic patients, however, it is expected that extensive training-sessions are necessary to achieve a good BCI performance at least in some subjects.

[Functional electrical stimulation instead of surgery? Improvement of grasping function with FES in a patient with C5 tetraplegia]. / Funktionelle Elektrostimulation anstatt Operation? Verbesserung der Greiffunktion mittels FES bei einem Patienten mit Tetraplegie C5.

The aim of this study was to restore the grasp function of a tetraplegic patient with a C5 spinal cord injury (SCI) by means of functional electrical stimulation (FES). Using three pairs of surface electrodes and orthotic wrist stabilisation a simple palmar grasp was realised. The FES was controlled with a switch mounted on a wheelchair or-for the first time-with an EEG-based brain-computer interface (BCI). Application of this stimulation system enabled the patient to drink for the first time after the accident from a glass without any additional help.

Critical decision-speed and information transfer in the "Graz Brain-Computer Interface".

The "Graz Brain-Computer Interface (BCI)" transforms changes in oscillatory EEG activity into control signals for external devices and feedback. These changes are induced by various motor imageries performed by the user. For this study, 2 different types of motor imagery (movement of the right vs. left hand or both feet) were classified by processing 2 bipolar EEG-channels (derived at electrode positions C3 and C4). After a few sessions, within some weeks, 4 young paraplegic patients learned to control the BCI. In accordance with the participants, decision-speed (trial length) was varied and the information transfer rate (ITR) was calculated for each run. All experimental runs have been feedback-runs employing a simple computer-game-like paradigm. A falling ball had to be led into a randomly marked target halfway down the screen. The horizontal position was controlled by the BCI-output signal and the trial length was varied by the investigator across runs. The goal was to find values for trial length enabling a maximum ITR. Three out of 4 participants had good results after a few runs. Analysis of their last 2 experimental sessions, each containing between 10 and 16 runs, showed that the trial length can be reduced to values around 2 s to obtain the highest possible information transfer. Attainable ITRs were between 5 and 17 bit/min depending on the participant's performance and condition.

[Mental activity hand orthosis control using the EEG: a case study]. / Mentale Handorthesensteuerung über das EEG: Eine Fallstudie.

A report is given on the realization of a steering mechanism of a hand orthosis for a patient with paraplegia. An EEG-based Brain-Computer Interface (BCI) was used here for the first time, transferring purely mental activity to a control signal. This means that the patient has the capability to open or close the hand orthosis only by imagination of a movement. At this time, after a training period of about four months, the patient is able to move the hand orthosis with a certainty of almost hundred percent. The restored grasp function was verified by a grasp function test. Results are compared to those obtained using a conventional EMG-controlled orthosis.

The wider application of Ender's nailing in fractures of the femur--a study of 60 cases.

Having had wide experience in the use of Ender's nails in 387 fractures of the femur based on the traditional indications, the authors decided to extend its use to more atypical and complex cases. They report their experience in 60 such cases, which again confirmed the extremely favourable conditions of fixation and biomechanical advantages of this flexible osteosynthesis.

[Diacondylar V osteotomy of the femur]. / Die diakondyläre V-Osteotomie am Femur.

V-shaped osteotomy is an excellent means to correct axis deviations in the frontal and sagittal plane. As diacondylar V-osteotomy, it is a technically very simple procedure because of the anatomic conditions found in the distal end of the femur, and it offers all of the positive biologic effects of an osteotomy carried out near to the joint. Thanks to the large spongious contact surfaces of the fragments, the diacondylar V-osteotomy heals very quickly under full loading within the walking plaster applied to the thigh. This intervention which is not very stressful for patients may be applied for axis corrections in the distal femur end from the moment of closing of the distal epiphyseal cartilage of the femur until high age of the patients.