Spinal distraction system

A spinal distraction system including a bearing connector fastened to a fixated rod and a sliding rod, wherein the sliding rod includes a spring and a stop ring is disclosed. A method of distracting vertebrae is also disclosed.

FIELD OF THE INVENTION

The invention relates generally to a spinal distraction system including a first set of rods, a second set of rods, a fastener, a connector, and a spring. The spinal distraction system can be active and/or dynamic in nature.

BACKGROUND OF THE INVENTION

Spinal deformation during skeletal growth is a disorder with potential devastating consequences. Surgical treatment options are bothersome because correction and fusion of the deformation is incompatible with maintaining growth of the spine. Growing systems have also been used like growing rods, VEPTR, and recently magnetically controlled growing rods. However, these growing systems may require repeat operations or repeat elongations at certain intervals. These intervals are not similar to normal gradual growth of the spine, allow the spine to stiffen between lengthenings, lead to unphysiological strains on the tissues at the moment of lengthening, and can be a burden on the patient. In cases where surgical releases of the spine are to be performed, such as congenital deformations, the spine can re-fuse soon after operative release and static fixation with any current growth system and further growth may be impossible even with repetitive distractions.

SUMMARY OF THE INVENTION

In an aspect, there is disclosed a spinal distraction system comprising a bearing connector fastened to a fixated rod and a sliding rod, wherein the sliding rod includes a spring and a stop ring.

In another aspect, there is disclosed a method for distracting vertebrae, including inserting a first set of a plurality of fasteners into adjacent vertebrae in a first region; inserting a fixation rod into the first set of the plurality of fasteners; inserting a caudad end of the fixation rod into a bearing connector; inserting a second set of a plurality of fasteners into adjacent vertebrae in a second region; loading a stop ring and a spring onto the sliding rod; sliding the cephalad end of the sliding rod into the bearing connector so that the spring is disposed between the bearing connector and the stop ring; and inserting the caudad end of the sliding rod into the second set of a plurality of fasteners.

DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

Various embodiments will now be described in detail with reference to the drawings, wherein like reference numerals identify similar or identical elements. In the drawings and in the description that follows, the term “proximal”, as is traditional, will refer to the end of the device which is closest to the operator while the term “distal” will refer to the end of the device which is furthest from the operator. The term “cephalad” is used in this application to indicate a direction toward a patient's head, whereas the term “caudad” indicates a direction toward the patient's feet. Further still, for the purposes of this application, the term “medial” indicates a direction toward the middle of the body of the patient, whilst the term “lateral” indicates a direction toward a side of the body of the patient (i.e. away from the middle of the body of the patient). The term “posterior” indicates a direction toward the patient's back, and the term “anterior” indicates a direction toward the patient's front. Additionally, in the drawings and in the description that follows, terms such as front, rear, upper, lower, top, bottom and the similar directional terms are used simply for convenience of description and are not intended to limit the disclosure attached hereto.

As shown inFIGS. 1A and 1B, the present disclosure is directed to a spinal distraction system10including a bearing connector20fastened to fixated rod14and a sliding rod16, wherein the sliding rod16includes a spring22and a stop ring18. The spinal distraction system10can provide continuous distraction to vertebrae. The magnitude of the distraction force can be adjusted intraoperatively by a surgeon based upon tactile feedback or a pre-tension/length table. Additionally, the spinal distraction system10can be used in combination with existing posterior spinal fusion systems.

FIGS. 2A-2Eillustrate the bearing connector20. The bearing connector20includes a set screw24, a bearing30, and a housing21. The housing21can include a top surface36, a bottom surface38, and side surfaces46,47, as shown inFIGS. 3A-3B. The top surface36and the bottom surface38define a hollow40that can be configured and dimensioned to receive a rod, such as the fixated rod14, as shown inFIGS. 1A-1B. The rod can be side-loaded into the hollow40and then secured in place by rotation of the set screw24. Alternatively, the top surface36can have a defined hollow (not shown) that can be configured and dimensioned to receive the fixated rod14. In this manner, the rod can be top-loaded into the hollow and then secured in place by rotation of a set screw that would be located on a side surface46,47. In an alternative embodiment, the bottom surface38can define a hollow that can be configured and dimensioned to receive the fixated rod14. In this manner, the rod can be bottom-loaded into the hollow and then secured in place by rotation of a set screw that would be located on a side surface46,47.

As shown inFIGS. 2B, 3A, and 3Bthe housing21of the bearing connector20can include a first bore42that can extend from a first beveled side surface49to a second beveled side surface50. In an aspect, the spring22can abut either of the first beveled side surface49or second beveled side surface50. The first bore42can be configured and dimensioned to receive the bearing30. In particular, the first bore42can include a concave inner surface44that mates with a convex outer surface34of the bearing30. In this manner, the bearing30can freely rotate in a polyaxial manner within the housing21of the bearing connector20. As shown inFIGS. 4A-4C, the bearing30can include a second bore32configured and dimensioned to receive the sliding rod16.

The bearing connector20aligns passively with a rod, such as the sliding rod16with minimal friction. In this manner, there can be a reduction in growth resistance and metal debris. Metal debris can be associated with foreign body reactions, granuloma's and even low grade infections. The bearing connector20can also allow some sagittal motion, which can be enlarged by adding an extra rotational axis between the bearing connector20and the fastener12. The ability of the spinal distraction system10to allow some sagittal motion also enables the spinal distraction system10to absorb energy which can prevent the spinal distraction system10from fatigue failure.

The spinal distraction system10can include, instead of the bearing connector20, any connector that would provide for parallel connection of the fixated rod14and the sliding rod16. For example, the connector could be two bores adjacent to one another with two set screws to secure the rods within, where one set screw is left out to allow sliding.

As shown inFIG. 7, the sliding rod16can be loaded with a spring22and a stop ring18. In an aspect, the spinal distraction system10can include a stop ring18. The stop ring18can include a bore (not shown) and a set screw. The sliding rod16can be inserted through the bore of the stop ring18. The stop ring18can be positioned anywhere along the length of the sliding rod16. At a predetermined position, the set screw of the stop ring18can be tightened to secure the stop ring18along the sliding rod16at the predetermined position, such as after compression of the spring22.

The spring22also contains a bore (not shown) that can be configured and dimensioned to receive a rod, such as the sliding rod16. The spring22should be loaded so that one end of the spring22abuts the stop ring18, as shown inFIG. 7. The spring22can be made of any biocompatible material including metals and polymers, such as titanium. The spring22can be any gauge so long as the spring22is able to distract the vertebrae over a period of time. In an aspect, the distraction force provided by the spring22should be about 50 to about 250 Newtons, for example from about 55 to about 225 Newtons, and as a further example from about 60 to about 200 Newtons. This distraction force can be provided by a spring22with a compressed length from about 3 to about 5 centimeters, such as about 3.2 to about 4.9 centimeters, and as a further example from about 4.3 to about 4.8 centimeters. The spring22can have an uncompressed (relaxed) length of about 3 to about 15 centimeters, for example from about 8 to about 13.8 centimeters, and as a further example from about 8.4 to about 9.6 centimeters. It should be noted that the spring22can be compressed during the initial installation of the spinal distraction system10, but can also be compressed at any time thereafter depending upon the spinal growth. It is envisioned that any compression of the spring22after the initial compression would not be needed until several years later and would involve a minimal surgical procedure.

In an aspect, the spinal distraction system10can include one spring, two springs, three springs, etc. The number of springs22can be determined based upon the uncompressed length of the spring22as well as the optimal distracted length of the vertebrae. For example, the spinal distraction system10can include one spring22having an uncompressed length of 6 centimeters and a compressed length of 3 centimeters because the optimal distracted length of the involved vertebrae is 3 centimeters. Alternatively, the spinal distraction system10can include two springs22in series, each having an uncompressed length of 3 centimeters because the optimal distracted length of the involved vertebrae is 6 centimeters.

In an aspect, the spring22can be a mini-spring (not shown), for example, having an uncompressed length ranging from about 0.5 cm to about 3 cm, such as from about 0.75 cm to about 2.75 cm, including an uncompressed length from about 1.0 cm to about 2.5 cm. The mini-spring can be loaded onto a rod, such as the sliding rod16of the spinal distraction system10. The mini-spring22can also be used with conventional growing rods and/or magnetically controlled rods, in combination with a sliding connector, leading to a more dynamic spinal fixation. Such a spinal distraction system including at least one mini-spring22can be less prone to fatigue failure and spontaneous fusion.

In an aspect, the spinal distraction system10can include a sleeve or sheath (not shown) that can extend over at least a portion of a length of the spring22to minimize tissue ingrowth. In an aspect, the sleeve extends over 50% of the length of the spring22, for example over 75% of the length, and as a further example over 100% of the length of the spring22. The sleeve or sheath could be a flexible tube, cloth, or woven material, for example. In another aspect, the spring22can be coated with a biocompatible material, such as a polymer, that prohibits and/or minimizes tissue growth. In another aspect, the spring22can be integrated in cellular foam with closed cells. The combination of the sleeve/sheath and spring22should not allow for any dead space which could provide an area susceptible to infection.

The spinal distraction system10can be used in multiples. For example, a spinal distraction system10can be used singly or can be used as a pair.

The spinal distraction system10can be used in a method for distracting vertebrae. The method includes forming a hole in a vertebra. In an aspect, two holes can be formed in a vertebra. In another aspect, two holes can also be formed into an adjacent vertebra. The vertebrae can each have two holes formed therein and can be in a first region52, such as a cephalad region of a spinal column. Similarly, two holes can be formed in a vertebra and two holes can also be formed into an adjacent vertebra in a second region54, such as a caudad region of a spinal column. The method can further include inserting into the formed holes a first set of a plurality of fasteners12into adjacent vertebrae in the first region52, as shown inFIGS. 1A, 1B, and 5. One of ordinary skill in the art can determine the location along a length of the spinal column for the first region52relative to the second region54.

The method can include inserting a first set of a plurality of fasteners12into the formed holes of adjacent vertebrae in the first region52. An insertion tool can be used. The fasteners12can be any mechanical hardware, such as screws, including pedicle screws. In an aspect, each fastener of the plurality of fasteners12can include a head having a trough56configured and dimensioned to receive a rod, such as a fixated rod14and/or a sliding rod16. In an aspect, the method can include inserting a fixated rod14into the first set of the plurality of fasteners12. A caudad end of the fixated rod14can be inserted into a bearing connector20, as shown inFIG. 5, such as the hollow40of the bearing connector20. In another aspect, the bearing connector20can be inserted onto the caudad end of the fixated rod14, and then the fixated rod14can be inserted into the troughs56of the first set of the plurality of fasteners12. In an aspect, the method can further include locking the fixated rod14into the first plurality of fasteners12.

The method can include inserting a second set of a plurality of fasteners12into adjacent vertebrae in a second region54, as shown inFIG. 6. One of ordinary skill in the art will realize that this step can also be performed at the same time as inserting the first set of a plurality of fasteners12into adjacent vertebrae in the first region52. In particular, the first and second set of the plurality of fasteners12can be inserted into the insertion holes in any order, i.e., first region52and then second region54, or second region54and then first region52. Additionally, both of the first and second set of the plurality of fasteners12can be inserted before the fixated rod14is inserted into the first region52. In an aspect, the method can further include locking the sliding rod16into the second set of plurality of fasteners12.

The method can include loading a stop ring18and a spring22onto a sliding rod16, as shown inFIG. 7. Once the stop ring18is positioned at a predetermined location along a length of the sliding rod16a set screw associated with the stop ring18can be rotated to tighten the stop ring18. In an aspect, the set screw associated with the stop ring18can be left loose until a later time, such as after the spring22are compressed. In an aspect, the sliding rod16can be bent along its length before loading of the spring22and the stop ring18.

The method can include sliding an end of the sliding rod16into the bearing connector20so that the spring22is disposed between the bearing connector20and the stop ring18, as shown inFIG. 8. In particular, a cephalad end of the sliding rod16can be inserted into a bearing of the bearing connector20. A portion of the sliding rod16can extend through and beyond the bearing connector20. The spring22can abut a beveled side surface49of the bearing connector20at one end and the stop ring18on another end. In an aspect, the portion of the sliding rod16that extends beyond the bearing connector20can be parallel to the fixated rod14. An opposite end of the sliding rod16can extend towards and beyond the second set of the plurality of fasteners12in the second region54. The opposite end of the sliding rod16can be inserted into the second set of a plurality of fasteners12. The bearing connector20can provide continuous alignment with the sliding rod16and sagittal motion.

The method can further include compressing the spring22, as shown inFIG. 9. An instrument58can be positioned so that the bearing connector20, spring22, and stop ring18are between the ends of the instrument58. A force can be applied to a handle of the instrument58so that the stop ring18applies a force against the spring22thereby compressing the spring22against the bearing connector20. A force can be applied to the set screw associated with the stop ring18locking the stop ring18in place against the compressed spring22.

The method can further include compressing the spring22a second time after a period of time to provide a continuous distraction of the vertebrae.