Early mobilization of patients with SCI

If these principles of “spinal intelligence” are incorporated appropriately into the rehabilitation scheme, they can be successfully applied to reduce the initial problems of patients with SCI. During the very acute stage after injury, spinal reflexes are absent in most patients (spinal shock). Venous pooling occurs in the lower extremities, and the circulatory system is unstable. Together these symptoms are the cause for the extended period of immobilization. Standard therapy during this period consists of static verticalization of patients using a tilt table and application of passive movements of the legs by physiotherapists for about 10 minutes once per day. However, bedrest studies have shown that prolonged immobilization leads to quick loss of muscle mass, negative hemodynamic effects, and severe bone demineralization.⁴¹

In order to provide the clinical basis for an effective mobilization therapy at this very early stage of rehabilitation, two centers dedicated to the rehabilitation of SCI patients (Orthopedic University Hospital, Heidelberg, Germany and Balgrist University Hospital, Zurich, Switzerland) developed a novel robotic tilt table called the Erigo. This device moves the patient’s legs in a manner comparable to the physiological gait pattern. In contrast to conventional devices that provide continuous passive motion, the Erigo achieves not only appropriate physiological kinematics in terms of adequate hip extension but also kinetics (loading/unloading of the foot sole) that are close to a normal gait. The importance of these factors as triggers for the central pattern generator has been shown in experiments in spinalized cats¹¹ and in humans.¹⁰ A main design criterion of the device was the possibility of increasing the stepping frequency to a value comparable to that of normal walking.

Erigo device

The Erigo is based on a traditional tilt table (Fig. 50-1). The upper body part can be continuously tilted from the supine position up to 80 degrees. When the patient is lying on the tilt table, the patient’s upper body is secured through a harness, with chest and shoulder fixed. Each thigh is fastened by a cuff to a linear drive mechanism that is controlled by a microcomputer. In order to generate hip extension according to the physiological principles, the upper body part of the device also can be tilted downward up to 20 degrees in relation to the leg part. The foot is fixed by a strap onto a proprietary footplate. For physiological loading of the foot, a special spring damper mechanism is integrated into the footplate. Load is applied to the foot sole during the stance phase (hip and knee extension) by clamping of a spring beneath the plate. When the hip and the knee are flexed, the spring is released from the plate, and no load is generated.⁸ The overall load on the foot increases with the degree of tilting, as a greater percentage of the patient’s body weight counteracts with the spring-damped footplate.

Fig. 50-1 Simplified overview of the basic components of the Erigo robotic stepping device.

With these design principles, the Erigo combines the generation of a physiological load pattern with a continuously adjustable tilt and a stepping frequency up to one step cycle per second.

Clinical results of the Erigo

Early work suggests that blood pressure may stabilize with use of this device, leading to better postural adjustments and earlier onset of mobilization in wheelchair in rehabilitation.

To prove the hypothesis that this device leads to stabilization of the cardiovascular system, we initiated a clinical pilot study where we included six acutely injured patients with clinically complete injury of the cervical spinal cord (ASIA impairment scale A, lower extremity motor score 0) 4 weeks after injury and analyzed relative changes in blood pressure compared to baseline measurements recorded with patients in the initial resting position.⁸ Baseline measurements were recorded in the horizontal position because patients could not tolerate 10 minutes of upright standing position without signs of presyncope, especially at the onset of study participation. With the automated movement therapy, blood pressure increased up to 5% even though patients were tilted to the 60-degree upright position after the baseline interval (Fig. 50-2). After stopping the movement in this position, mean arterial pressure decreased significantly (−30%), thus showing the direct effect of passive movement on the circulatory system in these patients.⁸ From these results, this robotic stepping device seems to help reduce the negative side effects that occur during the early immobilization phase and shorten the time to functional training in a wheelchair. The Erigo device is commercially available (Hocoma, Volketswil, Switzerland).

Fig. 50-2 Application of the Erigo device to a patient with a very high lesion (C3), complete spinal cord injury.

Plasticity of neural structures

Experiments with spinalized cats with complete transection of the spinal cord in the thoracic region have shown the occurrence of training-induced reorganization of neural networks in the spinal cord. Lovely et al.²⁶ and Edgerton et al.¹² demonstrated that a spinalized cat that undergoes locomotor training walks much better than a cat without training. However, when locomotor training was stopped, the cat’s walking function deteriorated. This finding leads to the conclusion that the structure of the neural network responsible for movement generation is highly flexible and that it can adapt to changes caused by injuries to the central nervous system. The described phenomenon is called training-induced neural plasticity. The plasticity is based on feedback of afferent signals coming from force and joint position sensors and increased afferent input to the spinal cord when a dedicated functional task, such as walking, is performed. The increased stimulation results in reorganization of axonal connections and leads to improvement of function.

Treadmill training with partial body weight support

The traditional method for mobilization of patients with restrictions in gait function during the subacute phase of rehabilitation is the use of parallel bars, where patients strut themselves on the bars with their arms and thereby are able to walk a few steps. This kind of mobilization is considered ineffective with respect to the principles of training-induced plasticity. Repetition of a dedicated movement leads to accelerated skill acquisition of a motor function.¹³ This is the main reason why locomotor training on the treadmill has been established as a standard therapy for rehabilitation of neuromuscular gait disorders over the last 10 years.^18,47 Whereas patients can walk only a dozen steps in parallel bars, they can walk up to 20 times the distance on a treadmill. During treadmill training, patients are first secured in a harness and then attached to a counterweight, which ensures constant body weight support during all gait phases (Fig. 50-3). Initial support up to 60% of the body weight can be used; higher percentages appear to be less effective because of insufficient loading of the foot soles. The initial slow walking speed, which is chosen by the patient, is increased during the training course up to a normal walking speed.

Fig. 50-3 Manually assisted treadmill training by an incomplete paraplegic patient. The counterweights (seen in the right lower corner) are attached to the patient’s harness for body weight support.

Robot-assisted locomotion therapy

In general, patients with only a few residual functions at the beginning of the subacute rehabilitation phase and patients with severe spasticity are not able to walk independently, even with a high degree of body weight support. Their stepping movements must be manually assisted by one or two therapists, who stabilize the knee during stance phase and lift the foot during swing phase, and possibly by a third therapist, who stabilizes the trunk. This manual assistance is provided under ergonomically bad conditions; in some cases, a remarkable effort is required from the therapists to get the patient walking. This results in shorter training times and makes the quality of therapy highly dependent on the physical capacity of the therapists.

To overcome these limitations of manually assisted treadmill training, Colombo et al.⁷ (ParaCare, University Hospital Balgrist, Zurich, Switzerland) developed the Lokomat motor-driven gait orthosis, which is commercially available in combination with a treadmill. The Lokomat consists of a steel frame, which can be adjusted to the patient’s body properties, and a motorized bilateral hip and knee joint (Fig. 50-4). The Lokomat is fixed to the patient’s thigh and shank by three cuffs of different sizes made of hook-and-loop material (Fig. 50-5). Joint movements are generated by linear spindles at walking speeds comparable to a normal gait (up to 3.5 km/h). With implementation of a recently released adaptive impedance control algorithm, the Lokomat can precisely produce the amount of force necessary to support the patient’s preserved motor functions for achievement of a physiological gait pattern.³⁵

Fig. 50-4 Overview of the Lokomat robotic gait training device.

Fig. 50-5 Application of the Lokomat device.

A multicenter study of 20 chronic, incomplete SCI patients (injury for more than 2 years, stable neurological status) performed at four SCI centers (Schweizerisches Paraplegikerzentrum, Basel, Switzerland; Department of Physical Medicine and Rehabilitation, University of Illinois, Chicago, Illinois; Orthopaedic University Hospital, Heidelberg, Germany; and Balgrist University Hospital, Zurich, Switzerland) showed positive effects of a 4-week Lokomat training program (45-minute training session, 3–5 times per week). Patients who were able to walk with walking aids at the beginning of the training were able to walk almost two times faster and two times further after training. However, only two of the 20 patients were able to achieve significantly reduced dependency on their walking aids (walkers, crutches).⁴⁸

Another robotic device, a commercially available gait trainer developed by Hesse group (Berlin, Germany), has shown beneficial effects in patients with stroke and in a few patients with subacute incomplete SCI.¹⁹ However, our experience with the device revealed handling problems when training SCI patients with severe limitations of body and lower limb posture control. The basic design principle of the gait trainer, which generates walking movements only by motor-driven positioning of the foot, does not provide sufficient stabilization of the trunk and the legs and seems to be less effective in terms of physiological afferent stimulation of the spinal pattern generator.