The Practice Of Minimally Invasive Spinal Technique-Part III Discussion Ramos arid Martin studied intradiscal pressures during VAX-D treatment. Five cases with subligamentous disc herniation at L4-5, confirmed by MRI and scheduled for percutaneous discectomy, were chosen. Using lateral and antero-posterior fluoroscopy, a cannula was inserted into the nucleus pulposus of the L4-5 intervertebral disc. The pressure measurements were recorded by an Ohmeda pressure transducer connected to a Hewlett Packard pressure monitor via a saline bridge and a Camino fiberoptic intracranial transducer adapted for intradiscal measurements. Since the pressure transducers were designed to measure changes in the positive range, calibration was necessary. The pressure transducer and monitor for each patient were individually calibrated, and a correction curve was plotted showing the transducer readings versus actual pressures to correct for the nonlinearity of the instrumentation in the range of the negative pressures achieved. A pneumatic calibration analyzer was employed. Distraction tensions ranging from 50 to100 pounds were monitored on a digital readout and recorded on a continuous graph tracing by a chart printer incorporated in the control console. Intradiscal pressure changes were observed on the pressure monitor. Intradiscal pressures were significantly reduced to negative levels, ranging from 100 mm of Hg to a negative of 160 mm of Hg. Changes in intradiscal pressure were minimal until a threshold distraction tension was reached. The relationship between percentage maximum tension and time was a logarithmic function. If one plots the percentage of maximum tension reached in 60 seconds vs. time, it takes 17-20 seconds to reach 50%, 25-28 seconds to reach 70%, and 42-45 seconds to attain 90% of the maximum. The retraction phase followed a linear time/tension relationship and returned tobaseline in 25-30 seconds. The first large-scale retrospective study7 involved over 700 patients with low back pain and with/ without radicular symptoms. Over 70% achieved a positive outcome. Even though the study was not a randomized blinded trial, the majority of patients were suffering beyond the period where natural resolution would be expected. All had failed treatment with other modalities and demonstrated positive response during treatment and/or immediately thereafter. Sherry et al conducted a prospective randomized controlled trial of VAX-D versus TENS. All patients had chronic symptoms (average duration of pain 7 years). TENS was regarded as a placebo. The data revealed an attributable success rate of 68.4% for VAX-D, significantly superior when compared to TENS (p
Posted on: Thu, 01 Aug 2013 05:14:36 +0000
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