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Sore Back Relief Rests on Precision Bearings

Fri, 04/30/2010 - 5:14am
Axiom Worldwide

At some point in eighty percent of people’s lives, back pain will be their worst enemy. In many cases, the cause is pressure exerted on nerves branching out from the spinal column into the lower or upper extremities. This article discusses newly engineered technologies in spinal decompression. 

 

Axiom’s spinal decompression system, the DRX9000

Axiom’s spinal decompression system, the DRX9000

The causes of back pain are several, and proposed cures are too numerous for less than a book to cover. But for pain caused by compressive injury of the spine, one approach to relief, spinal decompression on the DRX9000, is continuing to demonstrate overwhelming patient success. As noted in the January 2008 issue of the peer reviewed journal, Pain Practice, “At follow up, patients reported a mean rate of low back pain reduction of 90% (SD 1.15) and a satisfaction score of 8.55 on a scale ranging from 0 to 10 (median, 9).”

One of the oldest ways to reduce the pressure on the spine was to put a person in traction in an attempt to increase the distance between vertebra. But putting a person out of commission for days in strange positions and possibly with weights attached to their legs seems, today, like medieval torture.

High tech approaches to back pain relief include spinal decompression, where a regimen of brief periods of increased and then reduced tension on the lower body alleviate pain associated with herniated and bulging discs, facet joint pain and sciatica. This approach is convenient, non-pharmaceutical, and far more comfortable than typical traction.

 

Engineering the Therapy

One company that specializes in the treatment of back pain is Axiom Worldwide of Tampa, Florida. Jim Gibson, current President and CEO, and Nick Exarhos, Executive Vice President, founded Axiom and started developing its spinal decompression system, the DRX9000, in 2000. They recognized that spinal decompression systems on the market at that time were poorly engineered and weren’t individualizing treatment. In addition, few systems attempted to accommodate motion of the patient’s spine using a moving mattress. Most systems that did incorporate a moving mattress used, and still do use, plastic slides or other composite materials to facilitate that motion. Friction in the moving mattress resulted in decreased performance and inconsistent ‘stick and slip’ type movement. Precise, controlled movement was lacking.

"Friction, slip-stop, gearbox binding and other such obstacles must be removed before you can focus on the patient", says Scot Johnson, Engineering Director for Axiom Worldwide. "These problems exist in all mechanical systems and we have gone to great lengths to produce a device that provides proper logarithmically-applied forces. One major advantage of our device is that we utilize steel bearing and shafting technology in our floating lower mattress. Some of our competition utilizes plastic slides, which don’t have as favorable a friction characteristic.”

How It Works
A patient on the DRX9000 from Axiom

A patient on the DRX9000



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 three and one half inches 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 that is 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.

Scot Johnson explains the action of the half of the mattress supporting the lower half of the body, “One of the most critical parts of the DRX9000 is the floating lower mattress. While the upper half of the body remains stationery, we want the lower body to be able to extend freely as our system provides a tension pull. 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. We think it is a competitive advantage over our competitors. Very few spinal decompression products have a floating lower mattress.”

Precise Motion Makes It Work
NB Corporation’s high load capacity slide product: the double wide, block-housed, TOPBALL bearing.
NB Corporation’s high load capacity slide product, the double wide, block-housed, TOPBALL bearing.

To ensure the electronically controlled motions are realized precisely, the floating lower mattress moves via linear bearings on precision ground shafts. Also, each bearing’s load plate is precision-ground (not stamped) and checked for consistency when it’s manufactured. These unique bearings have load plates whose ends 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. NB Corporation is the designer and manufacturer of these bearings. NB Corporation calls this unique line of bearings its TOPBALL line. Axiom utilizes both the single and double wide block-housed TOPBALL bearings identified as TWA 12 UU.

Obesity Is No Problem

The weight of patients who will rest on the bed of the system can be as much as four hundred pounds. The bearings, therefore, have to accommodate loads far in excess of four hundred pounds. To achieve this high load capacity, NB Corporation suggested the TOPBALL line because it has greater ball contact in its ground circular arches, thereby tripling load capacity. The bearings can actually carry a load of up to one ton (2000 lbs).

A Crossroller Bearing for the Neck

The DRX9000C provides spinal decompression for the neck, and moves horizontally on a different type of linear bearing. It is the NB Corporation SYT Slideway. Because it has great roller-to-rail contact, though more compact than other crossroller bearings, it, too, can support a ton.

Finding the Perfect Lubricant

Axiom engineers continue to improve their technology. They focus on what they refer to as the ‘five critical subsystems’. The floating lower mattress is considered one of those critical subsystems. Axiom determined the next step towards improving the floating lower mattress was to reduce friction by improving the bearing lubricant. Based on a review of the lubricant products then available, X-1R Corporation’s lubricant line was an ideal candidate. X-1R’s lubricant technology had been used successfully in NASCAR racing engines and had been adopted by for use in the Space Shuttle Crawler by NASA. Axiom discussed testing the lubricant in their mattress bearings and forming an exclusive strategic partnership to further development. The strategic partnership between these companies was completed in early 2007.

Axiom 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. In early 2007, Axiom and NB formed an exclusive strategic partnership, through the development of the testing and expertise utilizing 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 lubricant technology impregnates certain metal surfaces, increasing density of those surfaces and decreasing friction. The bearings can go without the addition of lubricants for a longer period of time, extending the life of the bearings. This characteristic, along with X-1R lubricants being eco-friendly, led to NASA’s approval for use on the Space Shuttle Crawler. The Space Foundation recognized X-1R lubricant technology for its use by NASA, and designated the lubricant as Certified Space Technology. The Space Foundation also recognized exclusively the strategic partnership between Axiom and X-1R, improving spinal decompression products utilizing Certified Space Technology.

Understanding How to Facilitate New Product Development

To clarify how Axiom has benefited from working with NB Corporation, Scot Johnson describes the NB working relationship during

NB Corporation’s high load capacity slide product: the single wide, block-housed, TOPBALL bearing.
NB Corporation’s high load capacity slide product, the single wide, block-housed, TOPBALL bearing.

product development, “NB went out of their way to get product to us, sample, and stock what we needed. We were incorporating some very low profile table slides into the DRX9000C for neck vertebral decompression. That bearing is a precision part and not easy to come by. I recall there were times when they, of their own accord, would have additional parts made (and stock them) when they knew we were in the development and problem solving mode. There was no purchase order. They were just doing that so that if we placed a purchase order they would have it in stock. I was very impressed.”

Future Developments

Axiom is dedicated to extensive research and development into several areas, including spinal decompression. Through their strategic partnership and long-term success with NB, all linear motion bearings will continue to be provided by NB Corporation. Their products are identified as the DRX9000, DRX9000C and the DRX9500. They are designed to meet the quality and regulatory needs of the U.S. and international markets, and are sold in over 22 countries worldwide.

Scot Johnson summarizes the benefits of the DRX system, “Our technology is extremely effective, it takes twenty treatments spread over six weeks, which are about 28 minutes long, to improve most patient’s situations tremendously. Patients are encouraged to wear a lower back support during the first weeks of treatment. 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.”

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