For decades, external fixation was the best option for limb lengthening. Recent advances have resulted in less invasive alternatives that decrease complications associated with external fixation and improve results. Internal bone lengthening devices such as Precice method were developed to eliminate the need for external fixators and the associated problems during bone lengthening. Successful bone lengthening has been reported with the use of internal lengthening devices in the past; however, these old devices have their own unique complications, including infection, substantial pain during distraction, nail fracture, asymmetrical bone healing, premature ossification, pseudoarthrosis, failure of distraction mechanism, and uncontrolled distraction (the so-called runaway nail phenomenon). These complications often require manipulations under anesthesia or additional operative procedures. Previous designs of internal lengthening devices operate on diverse mechanisms. They have been fraught with imprecice distraction, resulting in nerve injuries, joint contractures, nonunions, and other complications. Recently, a magnet-operated telescopic PRECICE® internal lengthening device was approved for clinical use by the FDA. Distraction of this nail is claimed by the manufacturer to be accurately controlled via a custom-programmable external remote controller.
This internal lengthening nail is a valid option to achieve accurate and precice limb lengthening to treat a variety of conditions with limb shortening or leg length discrepancy. Randomized, larger-sample, long-term studies are required to further confirm clinical efficacy of these devices, monitor for any late failures and complications, and compare with other internal lengthening devices with different mechanisms of operation.
The PRECICE® nail of the selected size and diameter is assembled by connecting the two telescopic nail pieces as per manufacturer guidelines.
The internal architecture of the PRECICE® nail consists of a permanent rare earth magnet that is connected to a gear box and screw shaft assembly. The internal magnet within the nail is localized intraoperatively using a wire under fluoroscopic guidance. The external controller unit is placed directly over the internal nail magnet under fluoroscopy and the location is marked on the skin. You can also see Precice Method
Distraction of the nail is initiated during the early postoperative period, typically Day 5 for the femur and Day 7 for the tibia. The external remote controller unit is applied on the skin marking corresponding to the location of the internal nail magnet. Lengthening is done at approximately 1 mm per day until the desired length is achieved. Once the length is achieved the consolidation phase starts and the bone heals around the nail.
In summary, based on some initial series of 25 femoral and/or tibial lengthening procedures, the new PRECICE® internal lengthening nail appears to be a valid treatment option for straightforward bone lengthening procedures with mild to moderate deformity correction. Patients must be cautioned against undergoing an MRI study while carrying this nail within their body because of the possibility of magnet interaction and risk of bodily injury. As for the removal of the intramedullary nails, they can be removed after full consolidation of bones (which takes approximately 1-1.5 yrs). However, nail removal is optional in this method. The nails are designed biomechanically, which means they can remain inside bones and not cause a problem for the patient. These nails can be removed after several years or not removed at all.
Randomized, larger-sample studies are warranted to compare clinical efficacy of the PRECICE® nail to different internal lengthening devices available in the market.