[Effect of posture on spinal cord stimulation in patients with chronic pain syndromes: analysis of energy requirements in different patient postures].

BACKGROUND AND OBJECTIVE

Patients being treated with spinal cord stimulation for chronic pain complain of variable paresthesias, particularly in relation to changes in posture. Such changes affect the great majority of patients with implantable pulse generators, requiring them to use the external programmer for avoidance of painful paresthesias or even to disconnect the generator, leading to loss of pain relief. The aim of this study was to determine the relationship between the pulse charge needed for stimulation and the patient's different postures.

MATERIAL AND METHODS

Observational study of 70 patients treated with spinal cord stimulation in the following postures and situations: decubitus position, standing, seated, and walking. With the patients standing, we analyzed the thresholds of perception, pain, and pain relief, as well as the therapeutic range. Studies were performed in all patients. Later, data were analyzed by anatomical positioning of the stimulator (cervical, thoracic, sacral, occipital, or subcutaneous).

RESULTS

In the analysis of the therapeutic range in the overall group we identified statistically significant differences between decubitus and standing positions and between decubitus position and walking. At the level of the thoracic spine differences were identified between all positions except between standing and walking and between seated and decubitus positions. At the level of the cervical spine, no significant differences were detected. Analysis of the pulse charge showed a significant difference in the decubitus position, in which less charge was needed to achieve satisfactory stimulation. When electrodes implanted at the cervical and thoracic levels were compared, differences were found between standing and seated positions (P=.04) but none between decubitus position or walking and the other positions.

CONCLUSION

Stimulation systems are not currently designed to adapt to changes in distance between the electrodes and nerve fibers. Improvements are required in this respect.