[Biomechanical experiments for measuring traction lengthening of the lumbar spine during weight bath therapy].

Introduction: Weight-bath as an effective traction therapy has successfully been applied in Hungary for nearly a half century, however, it has still been constrained exclusively to empirical bases until the numerical biomechanical analysis of Bene and Kurutz appeared in 1993. Due to their calculations, for cervical suspension in traction bath, the value and distribution of tensile force along the spine became known, however, the most important information, namely, the deformation of spine segments to be stretched by the therapy is so far unknown.

Aims: In this paper the results of a wide-ranging in vivo biomechanical experimental analysis are presented, aimed partly to obtain the traction deformation effects of weight-bath therapy, partly to obtain the biomechanical traction model of human lumbar segments. The analysis aimed to clear the effect of decompression, extra weights, sex, aging, body height and weight.

Patients/methods: The experiments have been executed during the prescribed 20 minutes long weight-bath treatment of patients having indication for cervical suspension. Patients with other forms of suspension, like armpit bars, have been excluded from the analysis. Two groups of patients have been distinguished: 67 patients without and 88 patients with extra weight loads of 20-20 N (2-2 kgf) applied on the ankles. Extension values of lumbar segments LIII-IV, LIV-V and LV-SI have been measured. Tensile deformations have been specified as the change of the distance between two spinous process of vertebrae, measured by a special subequal ultrasound method developed by the research group. The experimental results have been evaluated by using special software for analyzing ultrasound pictures. More than 3500 ultrasound pictures of 400 lumbar segments of 155 patients have been measured and evaluated.

Results: As for the results, at the end of the treatment, elongation of lumbar segments has been demonstrated practically in 60% of patients without and in 75% of patients with extra weights. The mean extension of a lower lumbar segment after a 20 minutes long weight-bath treatment is about 1.2-1.4 mm, while with extra weights it is about 1.3-1.6 mm, in the average of the deformed segments only. In the average of all segments, the above mean extensions are 0.7-0.9 mm, and with extra weights yield 0.8-1.4 mm.

Conclusions: Just being suspended in water, due to the decompression, even without any extra weights, significant extension has been registered: a mean value of 1.0-1.2 mm per segments for the deformable, and 0.4-0.6 mm for all segments. The 20 minutes long treatment time in itself has a significant effect: the average additional extension is 0.2-0.4 mm per segments without, and about 0.5 mm with extra weights. The deformation capacity of lumbar segments decreases with increasing age of patients. Elongations increase with increasing body height. Body weight shows different tendency depending on the sudden elastic and time-dependent viscous deformations. Significant difference has been observed in reaction time of male and female patients: female patients react later, however the final traction effect seems to be equal.