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Lengthen Your Own Limbs

Wed, 10/26/2011 - 9:40am
Chris Fox , Product Design & Development

People who suffer from congenital abnormalities, major fractures, or even cancer have experienced the pain and difficulty of shortened limbs. Living with a shortened limb can cause discomfort, pain, and even cause trauma to other joints and limbs in compensation.

In August, Ellipse Technologies announced that it had received FDA marketing clearance for their PRECICE Limb Lengthening device in the United States, bringing a new light to the limb lengthening process. This system gives new capabilities for limb lengthening and better options to those who suffer from shortened limbs.

Ellipse’s initial models are based on the bones of the leg, as these are quite common to have impairing abnormalities. When the long bones of the leg, the femur or tibia, need to be lengthened, contemporary methods usually use external fixators. These external devices are notoriously bulky and consist of heavy rings with pins that attach to the bone. These pins cause permanent wounds while they are in place as they extend from the bone to the rings outside of the patient.  

As Ed Roschak, president and CEO of Ellipse Technologies, explains, “they often cause pain and are potential sites for infection.” There are also mechanical distraction devices that can be placed in the bone canal, but, Roschak continues, “these devices are not able to consistently lengthen at precise amounts, creating the risk of either early bone consolidation, or non-union, when the bone never solidifies.” 

The PRECICE Limb Lengthening system functions essentially the same as their external counterparts. The Ellipse Intramedullary Limb Lengthening System (IMLL) is comprised of a magnetic actuator, extension rods, locking screws, instruments, and a hand-held external remote controller (ERC). The magnetic actuator is a sterile single-use device that along with a sterilizable extension rod is surgically implanted using the instruments and locking screws. The ERC is used at various times after implant to non-invasively lengthen or shorten the IMLL.  

Following implantation (inside the bone), the IMLL utilizes distraction osteogenesis to produce a longer limb. Traditional intramedullary surgical techniques are used to implant and secure the proximal and distal sections of the IMLL to the target bone. The magnetic actuator of the IMLL includes a small internal magnet and gearing. After positioning the ERC against the skin in the vicinity of the internal magnet, activation of the ERC causes the magnet to rotate and lengthen the IMLL.

The bone is controllably broken and the patient non-invasively distracts (or lengthens) the bone about one millimeter per day. New bone then grows in, and when the desired amount of lengthening is reached, the process is stopped, and the bone solidifies completely. The IMLL remains implanted for at least six months after the last distraction to allow bone consolidation to occur. Once the physician determines that the implant has achieved its intended use and is no longer required, the IMLL is removed using standard surgical techniques. 

The majority of mechanical components are external on the patient, allowing ease of operation. As Roschak says, “There are no batteries to go dead and no electrical wires to break on the implant.” 

Technology and advancement always has hurdles to overcome. Roschak continues, “The biggest ongoing challenge remains the fact that, because the ideal approach is for the patient to self-lengthen the device daily, consistent patient training and patient compliance will remain very important, and will continue to get deep our deep attention.” He explains that even though the actual operation of the device is fairly simple, it is vital for a patient to stay compliant and well educated for their safety and the best results from lengthening.  

The device is capable of lengthening a total of 65 millimeters, which is sufficient for the vast majority of cases. If more than 65 millimeters of lengthening were ever required, then a second device could be implanted to replace the first, though the company intends to add a longer distraction length device, to handle these special cases.  

At this time, the PRECISE technology is based on applications in the legs, but future applications are coming to light. Basically, the technology has utility anywhere that an implanted device needs to be manipulated non-invasively, either for size change, shape change or even mechanical property change.

Roschak explains, “We have already been using this technology for straightening pediatric scoliosis via non-invasive lengthenings of our spinal implant we call MAGEC (Magnetic Expansion Control). Additional applications include a lengthening plate for placement on the outside of the bone, but still internal to the patient. There are also multiple spine applications in older patients. This technology can help patients, many of them young children, avoid multiple surgeries."

The future applications of this technology are becoming more apparent everyday. Strangely enough, this technology was first developed for a non-orthopedic application, namely adjustable gastric banding for obesity surgery. Roschak says, “it didn’t take long to realize how the technology could be modified to significantly improve the lives of children with scoliosis, children and adults with leg length discrepancies- our first two applications.” This technology could be applied anywhere a patient would benefit from adjusting an implant after surgery in response to healing, growth or aging. 

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