Vertebral Body Manipulation Device and Methods

Unmet Need
Spinal deformity occurs frequently and may affect up to 68% of the elderly population. Left untreated, these deformities may develop into spondylolisthesis, a spinal misalignment caused by a stress fracture in the vertebra and displacement of the vertebra from its original location. Spondylolisthesis occurs in about 5.8% of men and 9.1% of women, and can be corrected through a spinal reduction surgery. In a spinal reduction, surgeons implant pedicle screws into the misaligned vertebrae and use the screws to move the vertebrae into the correct location, and then affix the screw heads to a straight metal frame to stabilize the vertebrae in the realigned position. Currently, spinal reduction surgery involves switching between multiple plier-type instruments to make many corrective maneuvers in different planes, increasing the number of steps and making the procedure technically demanding. Also, it is challenging for surgeons to achieve fine control over vertebral adjustments because current instruments make it difficult for surgeons to gauge the amount of corrective force needed. Since current instruments lack the ability to provide accurate force feedback, surgeons may exert excessive force during vertebral adjustment, which can result in bone fracture. Existing instruments also restrict surgeons’ mobility and range of freedom to make adjustments, especially when moving from one plane to another. Additionally, current procedures are complicated by the lack of a specialized instrument to ensure that the heads of the pedicle screws stay in a parallel configuration during surgery. Since the screw heads will eventually be affixed to a straight metal support frame, any deviation in screw positions from a parallel configuration forces the metal frames to be reshaped to accommodate for discrepancies in the profile. Moreover, since existing devices were originally developed for the classic open surgery, they are unsuitable for use with newer, minimally invasive techniques. Hence, there is a need for a vertebral manipulation device compatible with minimally invasive surgeries that minimizes the number of instruments and maneuvers required, provides accurate force feedback and fine control, holds the pedicle screws in a parallel configuration, and maximizes surgeons’ range of mobility.

Technology Overview
The ReduX is a device for controlled vertebral body manipulation. Two ReduX devices are used to manipulate a pair of adjacent vertebral bodies, one on each side (left and right) of the spine. Compared to current surgical procedures which involve the use of many plier-type tools, the ReduX device minimizes the number of tools required by integrating its functionality into a single pair of devices. The device consists of two quick-lock connections linked to screw extensions which allow it to connect to pedicle screws on adjacent vertebrae. The extensions extend upward into hollow poles, which are linked to each other through an X-mechanism. A single ReduX device has 3 degrees of freedom (DoF) between the screws to which it is attached, which is one more degree of freedom than existing state-of-the-art alternatives. When coupled together, two ReduX devices provide 5 DoF of maneuverability, which covers almost a full range of mobility. Full mobility can be achieved by simultaneously using the ReduX device to maintain the position of the unlocked screws while also using traditional instruments to manipulate the vertebrae. Additionally, the ReduX device allows surgeons to laterally translate vertebrae independently from compressing them, which is not offered by any existing instruments. The greater DoF of the ReduX device offers greater mobility and enhances surgeons’ ability to dynamically maneuver the vertebral position compared to alternative instruments. Furthermore, the X-mechanism connecting the two adjacent vertebrae is used to align the screw heads in a parallel configuration during surgery, facilitating the placement of a straight metal frame onto the screws. This eliminates the need to bend and reshape the frame prior to locking it in the screws, which is often the case with classic tools. The ReduX device also includes a novel screw-nut-thread combination connected by two bushings in a single component. This design reduces internal friction, which provides surgeons with enhanced force feedback compared to existing alternatives. The compactness of the ReduX design enables it to take advantage of newly pioneered minimally invasive surgery techniques, unlike classic plier-type instruments that are unsuitable for use in minimally invasive procedures.

Stage of Development
The inventors have developed a prototype and proposed surgical procedures to use the device. Preclinical experiments with the device were conducted and the results are pending review for publication in Neurosurgery.

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