Abstract:
The present invention relates various embodiments of a laminoplasty implant comprising a telescopic spacer configured to attach to the vertebra and adjust the space between two cut portions of a vertebra.

Description:
[0001]    Related U.S. Application Data: Continuation-in-part of application Ser. No. 10/299,624 filed on Nov. 19, 2002 now U.S. Pat. No. 6,660,007, which is a continuation of application No. Ser. 10/035,281 filed on Jan. 3, 2002 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    Cervical stenosis with spinal cord compression and consequent myelopathy is a very common problem encountered by the spine surgeon. The usual cause of multilevel cervical stenosis is spondylosis and/or ossification of the posterior longitudinal ligament. Surgical decompression either through an anterior or posterior approach can be undertaken. 
         [0000]    An anterior approach usually involves multilevel corpectomy with fusion and stabilization. The main drawback of this technique is the increased time and complexity of the procedure as well as the risk of pseudoarthrosis and accelerated degeneration at the levels above and below the fusion. 
         [0003]    A posterior approach has traditionally involved a simple laminectomy, laminectomy with facet fusion, or laminoplasty. The drawback of a simple laminectomy is the risk of late clinical deterioration from either kyphosis, instability, or post-laminectomy scar formation. Laminectomy with facet fusion decreases the risk of kyphosis but it also decreases the range of motion in the spine and increases the risk of accelerated degeneration at the levels above and below the fusion. 
         [0000]    Laminoplasty either through open door or double door technique provides greater stability and range of motion when compared with laminectomy alone. This technique entails laminoplasty for decompression and fixation with a plate with or without laminar fusion. The principle behind laminar fixation is that it maintains the decompression following laminoplasty as well as the displaced lamina in a fixed position thereby also providing stabilization since facet motion is preserved. 
         [0004]    U.S. patent application Ser. No. 10/035,281 by the applicant describes several laminar fixation plates with and without a bone spacer that allow for lamina fixation and fusion. U.S. Pat. No. 6,660,007 assigned to the applicant also describes laminoplasty plates for open door and double door techniques with a spacer in the middle to maintain the decompressed lamina position. Different sized spacers are required depending on the extent of the laminar displacement required. 
         [0005]    There is a need for a laminoplasty fixation implant that can also be placed through a minimally invasive approach with a variable size adjustable to the spinal anatomy of the patient. The present invention is an apparatus for use in either the open door or double door laminoplasty technique to stabilize the lamina in the spine thereby preserving the range of motion as well as maintaining stability. It also provides for a universal laminoplasty implant with a spacer that can be expanded or reduced in size depending on the patient anatomy and the degree of spinal canal decompression required. 
       SUMMARY OF THE INVENTION 
       [0006]    The present invention relates a laminar fusion and fixation system following either open door or double door laminoplasty technique. This system with the spacer and plate reduces surgical time and simplifies laminar fixation and fusion if needed after laminoplasty. 
         [0007]    In one embodiment the lamina fixation device consists of a plate contoured at each end with a hollow telescopic spacer in the middle with adjustable length but uniform width and thickness specific for the cervical, thoracic or lumbar spine. The contoured ends of the plate allows screw placement in the lamina or spinous process on one side and the facet on the other side. The spacer edges can be straight, curved, or contoured with a notch to encase the lamina edge and allow securement to the lamina on one side and the lateral mass or facet on the other side. The hollow spacer can be packed with allograft or autograft bone to provide for lamina fusion. This implant is made of titanium or similar alloy with magnetic resonance imaging compatibility. Alternatively, part of the implant or spacer is solid and made of allograft bone, hydroxyapatite, or similar absorbable fusion material. The spacer can also be made of a radiolucent material like polyaryletherketone or polyetheretherketone (PEEK) which is packed with bone fusion material to allow radiographic assessment of the fusion. 
         [0008]    In another embodiment, the hollow spacer contains a compression spring which expands once implanted into the spine thereby pushing the spacer ends to firmly rest and attach to the lamina and facet. This device would be most suitable for a minimally invasive approach undertaken through a small exposure, whereby the implant can be positioned in the spine in a compressed position with a removable instrument and after implantation, the spring distracts the telescopic spacer and fixates the ends against the bones. 
         [0009]    In another embodiment, the lamina fixation device is a telescopic spacer construct with extensions on one or both ends designed for lamina fixation following a double door laminoplasty. The spacer in the middle of the plate allows for laminar fusion in the decompressed position once packed with either allograft bone, autograft bone, or bone morphogenic protein and the spacer extensions on both ends securing the device to the lamina on both sides. 
         [0010]    In another embodiment, the lamina fixation device telescopic spacer also comprises a compression spring. The longitudinal spacer ends comprise of extensions to secure to the lamina and/or facet edges. 
         [0011]    The telescopic spacer allows the extent of the laminar displacement to be adjustable by increasing or decreasing the spacer length after lamina fixation device has been implanted. Henceforth, it avoids the need for different size implants as one implant can be adjusted to fit all variations in spinal anatomy as well as the extent of the spinal canal decompression desired. The spacer telescopic components can also contain an engaging mechanism to interlock with each other through ratchet teeth to maintain the adjusted length. Alternative spacer telescopic engaging mechanisms can include screws, ridges, hooks, recesses, or a ball and socket mechanism. 
         [0012]    The procedure as would be undertaken with the use of the laminoplasty fixation system is described as follows. An open door laminoplasty entails creating a gutter at the junction of the lamina and medial aspect of the facet on both sides with the use of a drill. On the side of the laminoplasty opening, the drilling is carried through into the canal or the opening completed with a small kerrison rongeur. At the other side, the inner cortex at the lamina and facet junction is not drilled. The lamina at the open end is elevated and the spinous process pushed away in order to create a greenstick osteotomy and allow for the laminoplasty decompression. Typically, 6-12 millimeters of distraction between the lamina and the facet provides for a good spinal decompression but this can vary dependent on the degree of spinal canal decompression required. In order to maintain the position of the lamina, the pre-contoured laminar fixation implant with the telescopic spacer is positioned between the displaced lamina and the facet. The spacer maintains the displaced position of the lamina and the implant with the contoured ends secures the construct via screws to the lamina and facet. The telescopic spacer length can be adjusted to increase the distance between the lamina and the facet and increase the extent of the spinal canal space if needed. 
         [0013]    A trap door or double door laminoplasty is created by drilling on each side at the laminar and lateral mass junction the outer laminar cortex and sparing the inner laminar cortex. The spinous process may also be resected and a midline gutter is also created which extends through the inner cortex which can be opened with a small kerrison rongeur. 
         [0014]    The lamina on either side are lifted and opened creating a greenstick osteotomy on each side. In order to maintain the decompressed position of the lamina, a spacer is placed in between the split lamina. The spacer can either be fixated with screws to the lamina or the facets. 
         [0015]    A minimally invasive approach is undertaken with small incisions and serial dilation of the soft tissue along with splitting of the paraspinal muscles from the skin to the spine. A tubular port or any other shape retractor is then placed to maintain the exposure. The drilling of the lamina and if needed the spinous process is undertaken with this exposure using either an endoscope or microscope magnification and subsequently the lamina are displaced to widen the spinal canal. A laminoplasty implant is then placed and secured to the lamina and facet. Due to the small exposure, a laminoplasty implant that can contract to allow placement in the spine and then expand to the position desired after implant is ideal for this approach. The telescopic spacers described herein are ideal for this approach. The tubular port is then removed and the skin incision closed. Intra-operative x-rays or a navigation system can be used to localize the spine level and confirm correct implant placement. 
         [0000]    Another variation of the open door laminoplasty is the expansive laminoplasty most suited for the thoracolumbar spine. In this method, the lamina on either side at the junction of the facets are drilled and opened. A lateral spinal canal recess decompression and/or foraminotomy is undertaken and the lamina replaced with the spacer construct on both sides between the displaced lamina and facets. The present invention relates a laminar fusion and fixation system following laminoplasty. This system with the telescopic spring spacer reduces surgical time and simplifies laminar fixation after laminoplasty. 
         [0016]    The spacer longitudinal ends can be contoured with a notch to allow securement to the lamina on one side and the lateral mass or facet on the other side. The contoured end shape can be curved, straight, or any other shape to encase and secure the lamina or facet edge. 
         [0017]    In another embodiment of the bone spacer, the edges have a superior cuff or shoulder that allows securement against the lamina and facet on both sides as well prevent migration of the spacer into the spinal canal. The spacer can also be resorbable and made of hydroxyapatite or similar absorbable material which is eventually resorbed and/or replaced with autologous bone during the fusion process. 
         [0018]    The laminoplasty device can also comprise of a plate made of titanium or similar alloy with magnetic resonance imaging compatibility which is contoured at the edges to allow fixation of the laminoplasty and securement of the spacer. The contoured design of the plate allows screw placement in the lamina or spinous process on one side and the facet on the other side. 
         [0019]    In another embodiment the allograft bone or resorbable graft and plate are constructed as a unit with the bone graft/spacer attached to the plate in the middle through either screws or an adhesive material. 
         [0000]    In another embodiment, the bone graft and plate are designed for laminar fusion and fixation following double door laminoplasty. The bone graft or spacer in the middle allows for laminar fusion in the decompressed position with the plate design bent on either end securing the spacer to the lamina and facet. 
         [0020]    The spacer can be made of any bio-compatible material, including autograft, allograft or xenograft bone, and can be resorbable or non-resorbable in nature. Resorbable materials can include polylactide, polyglycolide, tyrosine-derived polycarbonate, polyanhydride, polyorthoester, polyphosphazene, calcium phosphate, hydroxyapatite, bioactive glass, and combinations thereof. Further examples of non-resorbable materials are non-reinforced polymers, carbon-reinforced polymer composites, PEEK (polyetheretherketone), and PEAK (polyaryletherketone) composites, shape-memory alloys like nitinol, titanium, titanium alloys, cobalt chrome alloys, stainless steel, ceramics and combinations thereof and others as well. 
         [0021]    In another embodiment of the lamina fixation device, the plate has two extensions perpendicular to the longitudinal plate axis that engage the lamina and facet in a fixed position. The perpendicular extensions can be straight, curved, L-shaped, or contoured with a notch to secure the lamina or facet ends. The plate has a telescopic component between the two extensions that allow adjustment of the distance between the extensions to contour to specific spinal anatomical variations. The plate telescopic components interlock with each other through ratchet teeth to maintain the adjusted length. Alternative plate telescopic engaging mechanisms can include screws, ridges, hooks, recesses, and ball and socket mechanism. The plate ends can also be angled up or down if needed to contour to the spinal anatomy and the laminoplasty technique undertaken. 
         [0022]    The procedure as would be undertaken with the use of the laminoplasty fixation system is described as follows. An open door laminoplasty entails creating a gutter at the junction of the lamina and medial aspect of the facet on both sides with the use of a drill. On the side of the laminoplasty opening, the drilling is carried through into the canal or the opening completed with a small kerrison rongeur. At the other side, the inner cortex at the lamina and facet junction is not drilled. The lamina at the open end is elevated and the spinous process pushed away in order to create a greenstick osteotomy and allow for the laminoplasty decompression. Typically, about 6-12 millimeters of distraction between the lamina and the facet provides for a good spinal decompression but this can vary depending on the spinal anatomy. In order to maintain the position of the lamina, a pre-designed plate is placed with curved ends to allow one end to secure to the lamina and the other end to the facet with screws. The plate has two extensions perpendicular to the longitudinal plate axis with a telescopic component in between the extensions which can be adjusted to increase the distance between the extensions and therefore, the lamina and the facet and increase the extent of the spinal canal space. 
         [0023]    Another variation on the open door laminoplasty is the expansive laminoplasty most suited for the thoracolumbar spine. In this method, the lamina on either side at the junction of the facets are drilled and opened. A lateral spinal canal recess decompression and/or foraminotomy is undertaken and the lamina repositioned with a plate construct on both sides between the facets and lamina. 
         [0000]    A trap door or double door laminoplasty is created by drilling on each side at the laminar and lateral mass junction the outer laminar cortex and sparing the inner laminar cortex. The spinous process also be resected and a midline gutter is also created which extends through the inner cortex which can be opened with a small kerrison rongeur. The lamina on either side are lifted and opened creating a greenstick osteotomy on each side. In order to maintain the decompressed position of the lamina, a plate construct is placed with the plate longitudinal ends fixated with screws to the lamina or even the facets. The perpendicular telescopic plate extensions in the middle can be adjusted to maintain the displaced lamina positions. 
         [0024]    The telescopic component of the fixation system allows the two portions of the plate to slide into or away from each other thereby adjusting the spacer length and provides for laminar displacement after the device has been implanted. This avoids the need for manually displacing the lamina during surgery at which time with the traditional procedure, several spacer implant sizes are tested to find the right size that conforms to the patient&#39;s spine anatomy. 
         [0025]    The laminoplasty implants can be made of metal, polymers, ceramics, composites, and/or any bio-compatible material with sufficient strength to maintain the open position of the divided lamina. The implants can be constructed of titanium or titanium alloy for MRI imaging compatibility. It could also be made of a bio-absorbable material (polyesters, poly amino acids, polyanhydrides, polyorthoesters, polyurethanes, polycarbonates, homopolymers, copolymers of poly lactic acid and poly glycolic acid, copolyesters of e-caprolactone, trimethylene carbonate, and para-dioxanone), or allograft or xenograft bone that is absorbed by the body over time once the divided lamina have fused. Alternatively, it could be made of a radiolucent material (polyetheretherketone), plastic, or a combination of plastic and metal to reduce CT and MRI imaging artifact. 
         [0026]    The laminoplasty implants can be of a unitary construction, such that the spacer portion, lamina engaging portions and/or the facet engaging portions can be integral or formed from a single piece of material. Alternative embodiments contemplate that the components of the laminoplasty implant can be non-integral, and can be attached to and/or coupled to other components of laminoplasty plate. Embodiments of the laminoplasty implants also describe an expandable spacer portion and/or one or more bendable lamina engagement portions in order to conform to the anatomy of a particular patient. The spacer portions and/or lamina engagement portions can also be pre-bent to accommodate patient anatomy based on anatomical considerations encountered during surgery. The spacer has open ends along the longitudinal plate axis and in other embodiments can also contain open top end to pack the spacer with bone fusion material after implantation and set expansion of the spacer. The bottom end of the spacer is solid and prevents any bone fusion material to migrate into the spinal canal. 
         [0027]    Various embodiments and advantages of the current invention are set forth in the following detailed description and claims which will be readily apparent to one skilled in the art. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0028]      FIG. 1  is a side view of an embodiment of the laminoplasty device. 
           [0029]      FIG. 2  is a top view of the laminoplasty device. 
           [0030]      FIG. 3  is a cross-sectional top view of the laminoplasty device. 
           [0031]      FIG. 4  is a bottom view of the laminoplasty device. 
           [0032]      FIG. 5  is a cross-sectional side view of the laminoplasty device. 
           [0033]      FIG. 6  is a side view of another embodiment of the laminoplasty device. 
           [0034]      FIG. 7  is a top view of the laminoplasty device. 
           [0035]      FIG. 8  is a cross-sectional top view of the laminoplasty device. 
           [0036]      FIG. 9  is a bottom view of the laminoplasty device. 
           [0037]      FIG. 10  is a cross-sectional side view of the laminoplasty device. 
           [0038]      FIG. 11  is a top view of another embodiment of the laminoplasty device. 
           [0039]      FIG. 11B  is a cross-sectional side view of the laminoplasty device. 
           [0040]      FIG. 11C  is a bottom view of the laminoplasty device. 
           [0041]      FIG. 12  is a side view of another embodiment of the laminoplasty device. 
           [0042]      FIG. 13  cross-sectional top view of the laminoplasty device. 
           [0043]      FIG. 14  is a top view of the laminoplasty device. 
           [0044]      FIG. 15  is a bottom view of the laminoplasty device. 
           [0045]      FIG. 16  is a cross-sectional side view of the laminoplasty device. 
           [0046]      FIG. 17  is a side view of another embodiment of the laminoplasty device in a contracted position. 
           [0047]      FIG. 18  is a cross-sectional side view of the laminoplasty device in a contracted position. 
           [0048]      FIG. 19  is a top view of the laminoplasty device in a contracted position. 
           [0049]      FIG. 20  is a side view of the laminoplasty device in a distracted position. 
           [0050]      FIG. 21  is a cross-sectional side view of the laminoplasty device in a distracted position. 
           [0051]      FIG. 22  is a top view of the laminoplasty device in a distracted position. 
           [0052]      FIG. 23  is a top view of a vertebra. 
           [0053]      FIG. 24  is a cross-sectional view of a vertebra with a laminoplasty device in place following an open door laminoplasty. 
           [0054]      FIG. 25  is a side view of another embodiment of the laminoplasty implant in a contracted position. 
           [0055]      FIG. 26  is a cross-sectional side view of the laminoplasty implant in a contracted position. 
           [0056]      FIG. 27  is a top view of the laminoplasty implant in a contracted position. 
           [0057]      FIG. 28  is a side view of the laminoplasty device in a distracted position. 
           [0058]      FIG. 29  is a cross-sectional side view of the laminoplasty device in a distracted position. 
           [0059]      FIG. 30  is a top view of the laminoplasty device in a distracted position. 
           [0060]      FIG. 31  is a side view of another embodiment of the laminoplasty implant in a contracted position. 
           [0061]      FIG. 32  is a cross-sectional side view of the laminoplasty implant in a contracted position. 
           [0062]      FIG. 33  is a top view of the laminoplasty implant in a contracted position. 
           [0063]      FIG. 34  is a side view of the laminoplasty device in a distracted position. 
           [0064]      FIG. 35  is a cross-sectional side view of the laminoplasty device in a distracted position. 
           [0065]      FIG. 36  is a top view of the laminoplasty device in a distracted position. 
           [0066]      FIG. 37  is a cross-sectional view of a vertebra with a laminoplasty device in place following an open door laminoplasty. 
           [0067]      FIG. 38  is a side view of another embodiment of the laminoplasty device 
           [0068]      FIG. 39  is a top view of the laminoplasty device 
           [0069]      FIG. 40  is a cross-sectional top view of the laminoplasty device. 
           [0070]      FIG. 41  is a cross-sectional side view of the laminoplasty device. 
           [0071]      FIG. 42  is a bottom view of the laminoplasty device. 
           [0072]      FIG. 43  is a cross-sectional side view of the laminoplasty device taken along line A in  FIG. 41 . 
           [0073]      FIG. 44  is a cross-sectional view of a vertebra with a laminoplasty device in place following an open door laminoplasty. 
           [0074]      FIG. 45  is a side view of another embodiment of the laminoplasty device. 
           [0075]      FIG. 46  is a cross-sectional side view of the device. 
           [0076]      FIG. 47  is a cross-sectional top view of the device. 
           [0077]      FIG. 48  is a bottom view of the device. 
           [0078]      FIG. 49  is a top view of the device. 
           [0079]      FIG. 50  is a top view of another embodiment of the laminoplasty device. 
           [0080]      FIG. 51  is a side view of another embodiment of the laminoplasty device in an extended position. 
           [0081]      FIG. 52  is a top view of the device in an extended position. 
           [0082]      FIG. 53  is a cross-sectional side view of the device in an extended position. 
           [0083]      FIG. 54  is a side view of the device in a retracted position. 
           [0084]      FIG. 55  is a top view of the device in a retracted position. 
           [0085]      FIG. 56  is a cross-sectional side view of the device in a retracted position. 
           [0086]      FIG. 57  is a side view of another embodiment of the laminoplasty device in an extended position. 
           [0087]      FIG. 58  is a top view of the device in an extended position. 
           [0088]      FIG. 59  is a cross-sectional side view of the device in an extended position. 
           [0089]      FIG. 60  is a side view of the device in a retracted position. 
           [0090]      FIG. 61  is a top view of the device in a retracted position. 
           [0091]      FIG. 62  is a cross-sectional side view of the device in a retracted position. 
           [0092]      FIG. 63  is a side view of another embodiment of the laminoplasty device in a retracted position. 
           [0093]      FIG. 64  is a cross-sectional side view of the device in a retracted position. 
           [0094]      FIG. 65  is a top view of the device in a retracted position. 
           [0095]      FIG. 66  is a side view of the device in an extended position. 
           [0096]      FIG. 67  is a cross-sectional side view of the device in an extended position. 
           [0097]      FIG. 68  is a top view of the device in an extended position. 
           [0098]      FIG. 69  is a side view of another embodiment of the laminoplasty device. 
           [0099]      FIG. 70  is a cross-sectional side view of the device. 
           [0100]      FIG. 71  is a cross-sectional top view of the device. 
           [0101]      FIG. 72  is a bottowm view of the device. 
           [0102]      FIG. 73  is a top view of the device. 
           [0103]      FIG. 74  is a side view of another embodiment of the laminoplasty device in a retracted position. 
           [0104]      FIG. 75  is a cross-sectional side view of the device in a retracted position. 
           [0105]      FIG. 76  is a top view of the device in a retracted position. 
           [0106]      FIG. 77  is a side view of the device in an extended position. 
           [0107]      FIG. 78  is a cross-sectional side view of the device in an extended position. 
           [0108]      FIG. 79  is a top view of the device in an extended position. 
           [0109]      FIG. 80  is a cross-sectional view of a vertebra with a laminoplasty device seen in  FIG. 38  or  FIG. 63  in place following a double door laminoplasty. 
           [0110]      FIG. 81  is a cross-sectional view of a vertebra with a laminoplasty device seen in  FIG. 51  in place following a double door laminoplasty. 
           [0111]      FIG. 82  is a cross-sectional view of a vertebra with a laminoplasty device seen in  FIG. 69  or  FIG. 74  in place following a double door laminoplasty. 
           [0112]      FIG. 83  is a top view of another embodiment of the laminoplasty device. 
           [0113]      FIG. 84  is a side view of the device. 
           [0114]      FIG. 85  is a cross-sectional side view of the device. 
           [0115]      FIG. 86  is a cross-sectional view of a vertebra with the laminoplasty device in place following an open door laminoplasty. 
           [0116]      FIG. 87  is a top view of another embodiment of the laminoplasty device. 
           [0117]      FIG. 88  is a side view of the device. 
           [0118]      FIG. 89  is a cross-sectional side view of the device. 
           [0119]      FIG. 90  is a top view of another embodiment of the laminoplasty device. 
           [0120]      FIG. 91A  is a side view of the device. 
           [0121]      FIG. 91B  is a cross-sectional side view of the device. 
           [0122]      FIG. 92  is a top view of another embodiment of the laminoplasty device. 
           [0123]      FIG. 93  is a side view of the device. 
           [0124]      FIG. 94  is a cross-sectional side view of the device. 
           [0125]      FIG. 95  is a cross-sectional view of a vertebra with the laminoplasty device in place following an open door laminoplasty. 
           [0126]      FIG. 96  is a top view of another embodiment of the laminoplasty device. 
           [0127]      FIG. 97  is a side view of the device. 
           [0128]      FIG. 98  is a cross-sectional side view of the device. 
           [0129]      FIG. 99  is a cross-sectional view of a vertebra with the laminoplasty device in place following an open door laminoplasty. 
           [0130]      FIG. 100  is a top view of another embodiment of the laminoplasty device. 
           [0131]      FIG. 101  is a side view of the device. 
           [0132]      FIG. 102  is a cross-sectional side view of the device. 
           [0133]      FIG. 103  is a cross-sectional view of a vertebra with the laminoplasty device in place following a double door laminoplasty. 
           [0134]      FIG. 104  is a top view of another embodiment of the laminoplasty device. 
           [0135]      FIG. 105  is a side view of the device. 
           [0136]      FIG. 106  is a cross-sectional side view of the device. 
           [0137]      FIG. 107  is a cross-sectional view of a vertebra with the laminoplasty device in place following a double door laminoplasty. 
           [0138]      FIG. 108  is a top view of another embodiment of the laminoplasty device. 
           [0139]      FIG. 109  is a side view of the device. 
           [0140]      FIG. 110  is a cross-sectional side view of the device. 
           [0141]      FIG. 111  is a cross-sectional view of a vertebra with the laminoplasty device in place following a double door laminoplasty. 
           [0142]      FIG. 112  is a cross-sectional view of a vertebra with the laminoplasty device in place following an open door laminoplasty. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0143]    The present invention describes a device and method for fixation of lamina following a laminoplasty. The laminoplasty device as shown in  FIGS. 1-5  comprises a spacer  3  with an extension  1  and a spacer  4  with an extension  2 . The spacers  3  and  4  are telescopically engaged to each other with ridges or ratchet teeth  6  on the spacer  4  with the recesses  5  in the spacer  3 . The spacers  3  and  4  are hollow with open ends  7  and  8  respectively. The spacer  3  and  4  walls are open at the top  15  and  16  and ends  7 ,  14  and  8 ,  13  respectively to allow packing of the hollow spacers after or before implantation with bone fusion material to fuse the lamina with the facet. Bone fusion material can comprise of autograft bone, allograft bone, xenograft bone, demineralized bone matrix, bone morphogenic protein, hydroxyapatite, and other bone fusion extenders. The solid floors  9  and  10  face the spinal canal and prevent the bone fusion material from migrating into the spinal canal. The extension  1  is angled upwards and comprises of holes  11  for placement of a screw into the facet. The extension  2  is angled downwards and comprises of holes  12  for placement of a screw into the lamina. The spacer engaging ends  7  and  8  can be curved, straight, or L-shaped. The telescopically coupled spacers  3  and  4  can be expanded or retracted into each other with a removable instrument depending on the extent of the lamina displacement required after the device is implanted into the spine. In another variation of the above embodiment as shown in  FIGS. 6-10 , the telescopic hollow spacers  19  and  20  have smaller openings  21  and  22  in the top wall rather than a completely open top wall. In another variation of the above embodiment, as shown in  FIGS. 11A-11C , the telescopic spacers  23  and  24  comprises of multiple screw holes  25   a  and  26   a  respectively with screw  25   b  placed into the facet and screw  26   b  placed into the lamina. Once the desired length of the telescopic spacers is obtained a screw  192  is placed through the overlapping holes  25   a  and  26   a  to secure the two spacers in that position. In another variation of the above embodiment as shown in  FIGS. 12-16 , the telescopic spacers  27  and  28  contain ratchet teeth  29  that engage with each other. The ratchet teeth on the spacer  27  are inside and the ratchet teeth  29  on the spacer  28  are on the outside. 
         [0144]    In another embodiment as shown in  FIGS. 17-22 , the laminoplasty device comprises a spacer  30  with an extension  32  and a spacer  31  with an extension  33 . The spacers  30  and  31  are hollow and telescopically linked to each other. The spacer  30  and  31  ends  34  and  35  are solid and can be curved, straight or L-shaped to engage the facet at the end  34  and the lamina at the end  35 . The extension  32  is angled upwards and comprises of holes  40  for placement of a screw into the facet. The extension  33  is angled downwards and comprises of holes  41  for placement of a screw into the lamina. The spacers contain a compression spring  39  that is attached at one side to the spacer  30  end wall  34  and at the other side to the spacer  31  end wall  35 .  FIGS. 17-19  illustrate the device with the telescopic spacers  30  and  31  in a retracted position with the spring  39  contracted.  FIGS. 20-22  illustrate the device telescopic spacers  30  and  31  in an extended position with the spring  39  in a distracted position. The hole  37  in the spacer  30  top wall and the hole  38  in the spacer  31  top wall engage a removable instrument that holds the device in a retracted position and once disengaged after implantation the spacers are distracted by the compression spring  39 . The telescopically coupled spacers  30  and  31  are expanded by the spring  39  and engage the lamina at one end and the facet at the other end displacing the lamina. 
         [0145]      FIGS. 23 and 24  illustrate the method of laminoplasty with the use of the lamina fixation device. As shown in  FIG. 23  the spine vertebra comprises of a vertebral body  42 , facets  43  and  44 , lamina  47  and  48 , spinous process  46 , and spinal canal  45 .  FIG. 24  shows the unicortical greenstick osteotomy  51  with the displaced lamina  48  from the facet  44 . The device is attached to the severed lamina  48  with a screw  49  and attached to the facet  44  with a screw  50 . 
         [0146]    In another embodiment of the laminoplasty device as shown in  FIGS. 25-30 , the spacer  54  comprises an extension  52  and a facet engaging end  56 . The end  56  has a L-shaped lip to engage the facet. Similarly the spacer  55  has an extension  53  and a lamina engaging end  57  that is L-shaped. The telescopic spacers  54  and  55  also contain a compression spring  60  along with holes  58  and  59  to engage the removable device applicator (not shown).  FIGS. 25-27  show the device in a retracted position and  FIGS. 28-30  show the device in a distracted position. 
         [0147]    In another embodiment of the laminoplasty device  76  as shown in  FIGS. 31-36 , the spacer  62  has a facet engaging end  68  and extension  61  with screw holes  67 . The spacer  63  has an end  64  with lamina engaging extensions  65  and  66 . The spacers  62  and  63  are telescopically linked by a compression spring  69 .  FIGS. 31-33  illustrate the device in a retracted position and  FIGS. 34-36  illustrate the device in a distracted position. The device  76  illustrated in  FIGS. 31-36  is seen implanted in  FIG. 37 . The lamina greenstick osteotomy  70  allows displacement of the lamina  72  from the facet  73  increasing the spinal canal space  71 . The device is placed with the spacer  63  end engaging the lamina  72  and the spacer extension  61  attached to the facet  73  through a screw  74 . 
         [0148]    The embodiments described in  FIGS. 1-37  are designed for use with the open door laminoplasty technique. 
         [0149]    In another embodiment of the laminoplasty device  77  shown in  FIGS. 38-43 , the spacer  78  comprises a straight extension  80  and a bone engaging end  84 . The spacer  79  has a straight extension  81  and a bone engaging end  85 . The spacers  78  and  79  are hollow and telescopically linked with ratchet teeth  82  and recesses  83 . The top wall of the spacers also comprises of holes  86  to pack the hollow portions with bone fusion material. The holes  86  can also be used to engage a removable instrument to implant the device in the spine and distract the spacers  78  and  79  if needed. The extensions  80  and  81  prevent the device from migrating into the spinal canal. The device is shown implanted in  FIG. 44 . The device  77  is seen placed between the split lamina  72  and facet  73 . In another variation of the above embodiment as shown in  FIGS. 45-49 , the telescopic spacer extensions comprise spikes  87  and  88  that engage the bone edges. In another variation of the above embodiment as shown in  FIG. 50 , the spacers comprise of holes  89  and  90  that engage a screw to fixate the telescopic spacers into the spinal bone. 
         [0150]    In another embodiment of the laminoplasty device  137  as shown in  FIGS. 51-56 , the spacer  91  bone engaging end  93  comprises of extensions  95  and  97 . The spacer  92  bone engaging end  94  also comprises of extensions  96  and  98 . The spacers  91  and  92  are telescopically linked with a spring  101  and also comprise of holes  99  and  100  to temporarily engage a placement device which maintains the compressed position of the telescopic spacers and once implanted the placement device is disengaged and allows the spring to distract the spacers. The bone engaging end extensions engage with the lamina and/or facet and prevent inward or outward migration of the device.  FIGS. 51-53  illustrate the distracted position of the device and  FIGS. 54-56  illustrate the contracted position of the device. In a variation of the above embodiment, the bone engaging ends comprise of spikes. As shown in  FIGS. 57-62 , of the bone engaging extensions  102  and  103  on one side and  104  and  105  on the other side, the lower extensions  103  and  105  comprise of spikes. The spikes  103  and  105  extend into the bone to secure the device whereas the extensions  102  and  105  rest on the bone and prevent inward migration of the device into the spinal canal.  FIGS. 57-59  illustrate the distracted position of the device and  FIGS. 60-61  illustrate the contracted position of the device. In another variation of the above embodiment, the bone engaging ends comprise of only one extension on each side. As shown in  FIGS. 63-68 , the spacer  106  comprises a top extension  108  and the spacer  107  comprises an extension  109 . The compression spring  112  telescopically links the spacers  106  and  107 . The holes  110  and  111  allow for engagement of a placement device. The top extensions  108  and  109  prevent the device from migrating into the spinal canal.  FIGS. 63-65  illustrate the contracted position of the device  134  and  FIGS. 66-68  illustrate the distracted position of the device. 
         [0151]    The embodiments described in  FIGS. 38-68  can be used for any of the laminoplasty techniques (open door, double door, or expansive laminoplasty). 
         [0152]    Another embodiment of the laminoplasty device for use in the double door laminoplasty technique is shown in  FIGS. 69-73 . The telescopic spacer  113  is hollow and comprises an extension  114 , side wall recesses  117  and top wall holes  121 . The telescopic spacer  115  is hollow and comprises an extension  116 , side wall ratchet teeth  118  and top wall holes  122 . The extensions  114  and  116  are angled downwards and also comprise screw holes  119  and  120  for fixation to the lamina. The spacer  113  and  115  longitudinal ends are open and bone fusion material can be packed inside the hollow spacers. 
         [0153]    In another embodiment of the laminoplasty device  138  for use in the double door laminoplasty technique as shown in  FIGS. 74-79 , the spacer  123  comprises an extension  128  angled downwards and the spacer  124  comprises an extension  129  also angled downwards. The spacers  123  and  124  are telescopically linked by a compression spring  125 . The spacer  123  comprises of a hole  126  and an extension screw hole  130 . The spacer  124  comprises of a hole  127  and an extension screw hole  131 .  FIGS. 74-76  show the device in a contracted position and  FIGS. 77-79  show the device in an extended position. 
         [0154]      FIG. 80  illustrates the device  134  described in  FIGS. 63-68  in place in the spine. With the double door laminoplasty technique, a greenstick osteotomy is created at the junction of the lamina and facet on both sides  132  and  133 . The lamina  135  and  136  are also divided in the middle and opened out to increase the spinal canal space. The device  134  is then placed to maintain the opened lamina position as illustrated in  FIG. 80 .  FIG. 81  illustrates the device  137  described in  FIGS. 51-56  in place following the double door laminoplasty technique.  FIG. 82  illustrates the device  138  described in  FIGS. 74-79  in place following a double door laminoplasty. The device  138  is attached to the lamina  135  via screw  139  and the lamina  136  via screw  140 . 
         [0155]    Another embodiment of the open door laminoplasty device is shown in  FIGS. 83-86 . The device comprises an elongated telescopic plate  141  with recesses  146  and a perpendicular extension  147 . The non-telescopic plate end is angled upwards and comprises of screw holes  143  for attachment to the facet. The device also comprises of another elongated telescopic plate  142  with ratchet teeth  145  and a perpendicular extension  148 . The non-telescopic plate end is angled downwards and comprises of screw holes  144  for attachment to the lamina. The telescopic ends of plates  141  and  142  are coupled with each other through ratchet teeth  145  and recesses  146  allowing adjustment of the plate length and distance between the extensions  147  and  148 . The extension  147  engages the facet end and the extension  148  engages the lamina end. These perpendicular extensions can be straight, curved, or L-shaped. The device is shown implanted in  FIG. 86 . The device telescopic plate  141  is attached to the facet  149  via screw  152  and the telescopic plate  142  is attached to the lamina  150  via screw  151 .  FIGS. 87-89  illustrate another embodiment with the telescopic plate  151  and  152  perpendicular extensions  149  and  150  comprising a curved shape. 
         [0156]    In another embodiment of the laminoplasty device as shown in  FIGS. 90 and 91 , the elongated telescopic plates  153  and  154  comprises of multiple holes  155  and  156  and perpendicular extensions  157  and  158 . The holes  155  and  156  overlap the telescopic plate components and are fixed in a particular desired distracted or contracted position with a screw  161 . The screw  159  at the upward angled plate end attaches to the facet and the screw  160  at downward angled plate end attaches to the lamina. 
         [0157]    In another embodiment of the laminoplasty device shown in  FIGS. 92-95 , the plates  162  and  163  are telescopically linked with ratchet teeth. The plate  163  comprises of a perpendicular extension  164  for engagement with the lamina end.  FIG. 95  illustrates the device in place with the plate  163  attached to the lamina  150  via screw  166  and the device plate  162  attached to the facet  149  via screw  165 . 
         [0158]    In another embodiment of the laminoplasty device shown in  FIGS. 96-99  the telescopic plate  167  comprises of screw holes  169  for attachment to the facet and the telescopic plate  168  comprises of a perpendicular extension  170  that engages the lamina end.  FIG. 99  illustrates the device in place with the plate  167  attached to the facet  149  via screw  165  and the plate  168  secured to the lamina  150  without a screw. 
         [0159]    Another embodiment of the double door laminoplasty device is shown in  FIGS. 100-103 . The elongated telescopic plate  171  comprises recesses  176  for engagement with the ratchet teeth  175  in the elongated telescopic plate  172 . The plate  171  and  172  ends are angled downwards and comprises of screw holes  173  and  174 . The plates  171  and  172  also comprise of perpendicular extensions  177  and  178  for attachment to the lamina ends. The telescopic component of the plates allows for adjustment of the distance between the extensions  177  and  178 .  FIG. 103  illustrates the device in place with the screws  180  and  179  secured to the lamina and greenstick osteotomies on both sides  181  and  182 . In another variation of the device described above, the non-telescopic plate ends  183  and  184  are straight rather than angled downwards as shown in  FIGS. 104-107 . The device is secured to the lamina with screws  185  and  186 . 
         [0160]    In another embodiment of the laminoplasty device  191 , the plate non-telescopic ends are straight rather than being angled downwards. This allows the device to be used for both the open door and the double door laminoplasty techniques. As shown in  FIGS. 108-112 , the plates  187  and  188  are telescopically linked and comprise of perpendicular extensions  189  and  190  which can be straight, curved or L-shaped.  FIG. 111  illustrates the device  191  in place following a double door laminoplasty technique and  FIG. 112  illustrates the device  191  in place following an open door laminoplasty technique. 
         [0161]    The telescopic component of the device allows the two portions of the plate to slide into or away from each other thereby adjusting the spacer length and provides for laminar displacement after the device has been implanted. This avoids the need for manually displacing the lamina during surgery as well as determining the right spacer size that conforms to the patient&#39;s spine anatomy. It provides for a universal laminoplasty implant that can be used in minimally invasive or open laminoplasty techniques. The plate telescopic components interlock with each other through ratchet teeth to maintain the adjusted length. Alternative plate telescopic engaging mechanisms can include screws, ridges, hooks, recesses, ball and socket mechanism among other variations. 
         [0162]    While the inventions described here are specific, any variations to the described embodiments falls within the scope of the current invention and the protection granted therein.