Back pain effects about 80% of the population. Sometimes, the cause is pressure exerted on nerves branching out from the spinal column into the lower or upper extremities. For pain caused by compressive injury of the spine, one approach to relief that is proving successful is spinal decompression.
Axiom’s spinal decompression system, the DRX9000™.
Axiom Worldwide, Tampa, Fla., was founded in 2000 by Jim Gibson, current President and CEO, and Nick Exarhos, Executive Vice President, to develop the DRX9000™ spinal decompression system. They recognized that other systems on the market were unable to deliver individual treatment. In addition, few systems accommodated motion of the patient spine using a moving mattress.
Those systems that do use a moving mattress use plastic slides or other composite materials to facilitate that motion. However, the friction produces an inconsistent ‘stick and slip’ type movement.
“Friction, slip-stop, gearbox binding and other such obstacles must be removed before you can focus on the patient,” says Scot Johnson, engineering director at Axiom. “These problems exist in all mechanical systems and we have gone to great lengths to produce a device that provides proper logarithmically applied forces. Our device uses steel bearings and shafts in our floating lower mattress. Plastic slides don’t have as favorable a friction characteristic.”
A patient lays flat on a padded, two-part table contoured to keep the knees slightly bent. The lower half of the mattress, called the ‘floating lower mattress,’ supports the lower body and can move independently of the upper mattress half. The floating lower mattress can travel 3.5 in. away from the upper mattress. Sensors in the table weigh the patient and measure various parameters. The upper body is secured to the upper mattress. The lower body is secured to a strap that exits the tower in front of the patient. The strap applies tension to the patient’s lower body. This tension tends to stretch the body out. In general, as the body elongates, pressures on the spine’s intervertebral discs are reduced.
The TOPBALL bearings from NB Corp., have load plates with ends that are thinner than their centers. The floating load plate adjusts the clearance automatically. Axiom engineers chose to use both the single and double wide block-housed bearings.
Said Johnson, “One of the most critical parts of the DRX9000 is the floating lower mattress. As the spine elongates and decompresses, instead of having the body dragged along a stationery mattress, we let it float freely and elongate at its own rate and direction. The floating lower mattress really facilitates that effect.”
Linear bearings on precision ground shafts ensure that the electronically controlled motions of the floating lower mattress are precise. Also, each bearing’s load plate is precision-ground — not stamped — and checked for consistency at manufacture. These bearings, the TOPBALL from NB Corp., have load plates with ends that are thinner than their centers—making the center a fulcrum for self-alignment. Because wiper seals on the bearings are floating, they don’t restrict self-alignment and the floating load plate adjusts the clearance automatically. Axiom uses both the single and double wide block-housed bearings: TWA 12 UU.
The bearings must accommodate loads in excess of four hundred pounds. The TOPBALL line has greater ball contact in its ground circular arches, tripling load capacity. The bearings can carry a load of up to one ton (2000 lbs).
The DRX9000C™ helps decompress cervical spinal vertebra, and moves horizontally on a different type of linear bearing, the NB SYT Slideway. Because it has great roller-to-rail contact, though more compact than other crossroller bearings, it, too, can support a ton.
Axiom engineers focus on what they refer to as the ‘five critical subsystems,’ of which, the floating lower mattress is one. For less friction, the engineers focused on a lubricant from X-1R Corp. X-1R’s lubricants have been used successfully in NASCAR racing engines and have been adopted by for use in the NASA Space Shuttle Crawler.
The engineers requested NB perform static and kinetic friction and lifetime testing on the steel bearings and shafting used in the DRX9000. The testing would compare NB’s current lubricant for the application and the X-1R lubricant. The testing, completed in late 2007, demonstrated a decrease in static and kinetic friction by up to 27% over NB’s current lubricant for the application.
X1R lubricants impregnate certain metal surfaces, increasing surface density and decreasing friction. Thus, the bearings can operate for a longer period of time. X-1R lubricants are also eco-friendly.
Noted Johnson, “Our most recent prospective pilot study indicates a success rate of 88.9% in pain and symptom reduction. For a lot of people, that is the difference between forced immobility and being able to walk again.”
Filed Under: Medical, Linear motion • slides, Motion control • motor controls