In addition to devices for dynamic stabilization of the spine, Orthonex is also developing minimally-invasive diagnostic devices that can provide Neurosurgeons and Orthopedic Surgeons with objective, quantitative, and precisely-controlled clinical information concerning each of the multiple dimensions of spinal movement.  This information can help Neurosurgeons and Orthopedic Surgeons to decide which therapeutic approach is optimal for each patent.  

Currently, surgeons have to make clinical decisions with limited objective quantitative information concerning the multiple dimensions of spinal movement.  There is no currently-available minimally-invasive device that provides surgeons with objective, quantitative, and precisely-controlled clinical information concerning each of these multiple dimensions: spinal flexion, extension, lateral bending, decompression, compression, and torsion.  As a result, there is considerable subjectivity in assessing a patient's range of spinal motion in order to determine the best therapeutic course of action for a particular patient.  Not surprisingly, there is tremendous variation in practice patterns concerning which therapies are chosen for which conditions.   It is unlikely that quality is being optimized and that risks and costs are being optimally controlled with such subjective assessment and such high variation in practice patterns. 

To address this unmet clinical need, Dr. Hart Garner, a Board-Certified Neurosurgeon, invented Orthonex's patent-pending Vertamotion™ spinal motion measurement device.  The Vertamotion™ device, which is still under development and not yet approved by the FDA for patient care, has the potential to provide surgeons with objective, quantitative, and precisely-controlled clinical information concerning each of the multiple dimensions of spinal movement: flexion, extension, lateral bending, decompression, compression, and torsion.   This information can help surgeons to select the optimal therapeutic approach for each patent, improving the quality of care, reducing risk, and managing costs.

Orthonex's patent-pending Vertamotion™ spinal motion measurement device includes rods that are inserted into two or more spinal vertebrae in a minimally-invasive manner.  These rods are then automatically moved to cause and measure spinal flexion, extension, lateral bending, decompression, compression, or torsion.   With the Vertamotion™ device, each of these dimensions of movement can be independently and precisely controlled.  The resulting quantitative information concerning spinal motion can be analyzed to determine the optimal therapeutic approach for a particular patient.  Advantages of the Vertamotion™ device over earlier approaches include: objective and quantitative information concerning spinal motion dynamics; independent control and measure of flexion, extension, lateral bending, decompression, compression, or torsion, without confounding by multiple types of movement; and minimally-invasive spinal motion control and measurement without the need for invasive tissue removal.
 
As one example of how the Vertamotion™ device may be applied, a surgeon may have to decide whether or not to implant stabilization hardware to provide stabilization to support spinal fusion.  If the objective analysis of spinal motion provided by this device indicates that the vertebrae are sufficiently stable on their own, then stabilization hardware may not need to be implanted.  As another example, a surgeon may have to decide whether or not to replace a natural intervertebral disc, which may have become dysfunctional, with an artificial intervertebral disc.  If the objective analysis of information provided by this device indicates that the natural intervertebral disc is doing a good job of resisting compression, then an artificial intervertebral disc may not need to be implanted.  As another example, if the results of this device indicate asymmetry in spinal range of motion, then asymmetric dynamic stabilization of the spine may be appropriate.  

Figure 1 shows one example of how the Vertamotion™ device may be designed.  This example includes four rods whose distal ends have been minimally-invasively inserted into the spinal vertebrae.   The rods are threaded to enable tapping into pedicles in a manner analogous to the manner used for pedicle screws.  The proximal ends of the rods extend into a control unit.  This control unit exerts forces on the rods, in a manner that enables full control over the angle of each rod, and then measures the resulting movement of the vertebrae in response to these forces.   The motion-analyzing program in the control unit analyzes the relationship between the forces that are applied to the vertebrae through the rods and the resulting movement of the vertebrae.  Analysis of this relationship can help to guide the selection of a therapeutic approach from among different therapeutic approaches such as exercise, dynamic stabilization of the spine, and spinal fusion.

In the example shown in Figure 1, the four rods have been inserted into the body in a minimally-invasive percutaneous manner with x-ray assistance through small openings in the tissue of the patient's back.  Insertion of the rods is guided from the surface tissue into the pedicles via x-ray imaging.  The rods may then be manipulated within the control unit by electric actuators, hydraulic actuators, pneumatic actuators, or other means.

Spinal movements are often categorized into flexion, extension, lateral bending, decompression, compression, and torsion.  These movements may be informally defined as follows: spinal flexion is "bending forward"; spinal extension is "bending backwards"; spinal lateral bending is "bending to the right or left"; spinal decompression is "vertical elongation"; spinal compression is "vertical shortening" of the spine; spinal torsion is "vertical twisting."  However, these informal definitions are not sufficiently precise for our purposes.  These informal definitions are inadequate for isolating these movements from each other.  In earlier devices, these individual movements are either confounded or not measured at all.  For these reasons, we now present more formal and precise definitions of spinal flexion, extension, lateral bending, decompression, compression, and torsion.

Spinal flexion may be formally defined as spinal movement that changes a linear angle formed by the intersection of the lateral cross-sectional planes of two vertebrae, wherein the vertex of this angle is anterior to the center of the vertebrae.  The amount of flexion is the degree of the linear angle formed by the intersection of the lateral cross-sectional planes of two vertebrae, wherein the vertex of this angle is anterior to the center of the vertebrae.

Spinal extension may be formally defined as spinal movement that changes a linear angle formed by the intersection of the lateral cross-sectional planes of two vertebrae, wherein the vertex of this angle is posterior to the center of the vertebrae.  The amount of extension is the degree of the linear angle formed by the intersection of the lateral cross-sectional planes of two vertebrae, wherein the vertex of this angle is posterior to the center of the vertebrae.  

Spinal lateral bending may be formally defined as spinal movement that changes a linear angle formed by the intersection of the lateral cross-sectional planes of two vertebrae, wherein the vertex of this angle is to the right or left of the center of the vertebrae.  The amount of lateral bending is the degree of the linear angle formed by the intersection of the lateral cross-sectional planes of two vertebrae, wherein the vertex of this angle is to the right or left of the center of the vertebrae.

Spinal decompression may be formally defined as spinal movement that increases the average distance between all points in the lateral cross-sections of two spinal vertebrae.   Spinal compression may be formally defined as spinal movement that decreases the average distance between all points in the lateral cross-sections of two spinal vertebrae.   Spinal torsion may be formally defined as spinal movement that rotates the lateral cross-sectional plane of one vertebra around the vertical axis of the vertebra relative to the cross-sectional plane of a second vertebra.  

Figure 2 shows the same example of the Vertamotion™ device that was shown in Figure 1, except that now the angles of the four rods have been adjusted by the control unit in order to cause and measure flexion of the spinal vertebrae.   The control unit analyzes the relationship between the forces applied to the vertebrae by the rods and the resulting flexion of the vertebrae.  The results of this analysis are then used by a surgeon in order to guide selection of a therapeutic approach.   Figure 3 shows the same example, but for extension of the spinal vertebrae.  
 

Figure 2: Vertamotion™ Spinal Motion Measurement Device
During Controlled Flexion

Figure 3: Vertamotion™ Spinal Motion Measurement Device 
During Controlled Extension

Figure 4 shows the same example of the Vertamotion™ spinal motion measurement device that was shown in Figure 1, except that now the two pairs of two rods have been separated, in a manner that maintains their parallel configuration, in order to cause and measure pure decompression.   Measurement of pure compression is not possible with earlier devices without invasive removal of tissue, such as to insert a device into the intervertebral space.  Also, application of expansive forces to a single points on each vertebrae, as in some earlier devices, causes motion that confounds decompression with flexion. Figure 5 shows the same example, but for spinal compression.  Figure 6 shows the same example, but with the Vertamotion™ device causing and measuring spinal torsion.

To summarize, Orthonex's Vertamotion™ device for measuring spinal motion is a minimally-invasive device that can provide surgeons with objective, quantitative information concerning spinal flexion, extension, lateral bending, decompression, compression and torsion in order to select the best therapeutic course of action for each patient.   This information can help surgeons to select the optimal therapeutic approach for each patient, to improve the quality of care, and to reduce the risk and expense of unnecessary spinal procedures and hardware.  Orthonex's Vertamotion™ device is under development and is not yet approved by the FDA for use in patients.