The biomechanics of gravity-dependent traction of the lumbar spine.

STUDY DESIGN: This study evaluated the biomechanical responses evoked by the use of a gravity-dependent, self-operated traction device. These responses were determined by radiographs and were correlated with the body weight of the patient who was supported by a seat strap. OBJECTIVES: To examine the biomechanical effectiveness of the LTX 3000 Lumbar Rehabilitation System. SUMMARY OF BACKGROUND DATA: The LTX 3000 Lumbar Rehabilitation System (Spinal Designs International, Minneapolis, MN) was used to administer the lumbar fraction. No previous study has been conducted on this device. METHODS: For each of the 14 healthy male patients (age range, 19-69 years), lumbar lengthening, alterations in spinal curvature, and thoracic spine movement were assessed using radiographs taken: 1) before traction; 2) at 2, 10, and 15 minutes after the onset of traction; and 3) 2 minutes after traction was completed. Strain on the buttocks-supporting seat strap was recorded continuously during study sessions. RESULTS: The entire patient pool displayed an average maximal lumbar lengthening of 6.39 +/- 4.21 mm. The amount of lumbar lengthening was influenced by the degree of thoracic immobilization and by the amount of prior LTX 3000 (Spinal Designs International) use. Significant curvature reduction was observed during and after traction for the entire patient pool. Strain measurements correlated well with the measured response in the radiographs. CONCLUSIONS: Proper use of the LTX 3000 (Spinal Designs International) induces significant lumbar lengthening and curvature reduction in healthy patients. Measurements of body weight supported by the seat strap could help determine if thoracic immobilization has been achieved and if the patient is responding to the lumbar unloading.