Abstract:
A spine surgery modeling system simulates the spine with various vertebral body or disc conditions and allows a user to make adjustments and examine the three dimensional outcome of such adjustments. The spine surgery modeling system includes a spine model and a drive mechanism. The spine model has vertebral bodies and a disc space defined between adjacent vertebral bodies. The drive mechanism includes a worm gear, a worm, a rigid shaft, and a button. The worm engages the worm gear such that rotation of the worm causes rotation of the worm gear. The rigid shaft extends through a through hole defined in the worm and is configured to rotate the worm. The button is operatively engaged with the worm gear such that rotation of the worm gear causes movement of the button between collapsed and expanded states to change a height of the disc space.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
       [0001]    This application claims the benefit of, and priority to, U.S. Provisional Patent Application Ser. No. 61/902,334, which was filed on Nov. 11, 2013, the entire contents of which is hereby incorporated herein by reference. 
     
    
     TECHNICAL FIELD 
       [0002]    The present disclosure relates to orthopedic surgical devices for stabilizing and fixing the bones and joints of a body. Particularly, the present disclosure relates to a growing spine model that simulates the effects of changing relative positions of vertebral bodies in a spinal column (e.g., expansion and contraction) and the resulting three dimensional impact on the spinal column. 
       BACKGROUND 
       [0003]    The spinal column is a complex system of bones and connective tissues that provides support for the human body and protection for the spinal cord and nerves. The human spine is comprised of thirty-three vertebrae at birth and twenty-four as a mature adult. Between each pair of vertebrae is an intervertebral disc, which maintains the space between adjacent vertebrae and acts as a cushion under compressive, bending, and rotational loads and motions. 
         [0004]    There are various disorders, diseases, and types of injury that the spinal column may experience in a lifetime. The problems may include, but are not limited to, scoliosis, kyphosis, excessive lordosis, spondylolisthesis, slipped or ruptured disc, degenerative disc disease, vertebral body fracture, and tumors. Persons suffering from any of the above conditions typically experience extreme and/or debilitating pain, and often times diminished nerve function. 
         [0005]    Conventionally, surgeons receive training in the use of orthopedic devices to correct vertebral column injuries and diseases by the application of methods and devices on cadavers. The amount of training for each surgeon is necessarily limited by the expense, availability, scheduling, and other logistic requirements associated with the use of cadavers. One drawback of using cadavers is that the biomechanical behavior and particularly soft tissue forces on the spinal column when applying methods and devices to a cadaver are far different from that which are normally experienced in a surgical procedure on a living patient. 
         [0006]    Further, spine surgeons, when planning for a surgical procedure on a specific patient, normally study two-dimensional imaging data of the patient and lack an opportunity for a hands-on rehearsal of a method prior to operating on the patient. In recent years there has been a growing number of orthopedic practices and hospitals that have made the transition from film to all digital environments. Software based tools for orthopedic image review, analysis, and preoperative planning are becoming conventional tools of the orthopedic surgeon. While advances in surgical planning have been made, they are simply limited to improvements in providing two-dimensional data for study and planning. To receive hands-on training or to rehearse a surgical method, a surgeon is still limited to the use of cadavers. 
         [0007]    With such training and rehearsal limitations, it is not uncommon during an actual surgical procedure for a surgeon to encounter unforeseen anatomical or biomechanical conditions that may require an immediate revision of the surgical plan as it proceeds. The need to provide more numerous and less expensive ways to train surgeons or to permit hands-on surgery planning and rehearsal in the use of spinal surgery methods and devices is particularly needed in the treatment of conditions, such as scoliosis. It is not uncommon in the surgical treatment of scoliosis that the forceful manipulation and realignment of the spinal column can be a long, complicated mechanical effort that may include a potential of damage to anatomical structures in the proximity of the spinal column. In addition to the obvious training benefits that a three dimensional hands on device could provide, the manual rehearsal of planned methods in the treatment of scoliosis could potentially provide a faster, more effective, and safer surgical correction for the patient. 
         [0008]    One known modeling system is disclosed in U.S. Pat. No. 8,113,847 to Boachie-Adjei that is assigned to K2M, Inc. The entire contents of this patent are incorporated herein by reference. 
         [0009]    Thus, a need exists for a three dimensional hands on system to provide a spinal surgery modeling system that can be used by surgeons for training in the use of new devices and methods and can also be used in the planning and manual rehearsal of surgical procedures for patients. 
       SUMMARY 
       [0010]    The present disclosure relates to orthopedic surgery and, in particular, to surgical devices, prosthesis, and methods for stabilizing and fixing bones and joints of a body. Particularly, the present disclosure relates to a system for modeling surgical procedures using surgical methods, devices, and instruments as a training or surgery rehearsal system that can provide a user with an anatomically and biomechanically realistic model in a non-surgical environment. More particularly, the present disclosure relates to a spinal surgery modeling system that can engage with a model of a spine so as to configure the spine in a desired alignment and with selected degrees of force vectors biasing the spine model in selected positions so as to provide a spine modeling system that can be used as a surgeon training device or as a spinal surgery rehearsal platform. 
         [0011]    The spinal surgery modeling system of the present disclosure provides a hands on device that is capable of presenting a three dimensional model of a spinal column that can be configured to have any desired variation of spinal alignment and can be positioned in the three dimensional model of the spinal column with the application of tension members that provide a bias so as to simulate the biomechanical feel and behavior of a patient&#39;s spinal column. 
         [0012]    Also provided is a spinal surgery modeling system that is capable of securing any of a variety of models of spinal columns that can be selected by size and conformation to simulate, for example, pediatric, adult, and geriatric spinal columns. 
         [0013]    Also provided is a spinal surgery modeling system useful for simulating common deformities such as scoliosis, kyphosis, sagittal imbalance, and other spinal abnormalities. 
         [0014]    Also provided is a spinal surgery modeling system that can be prepared to simulate the anatomy and biomechanics of a surgery patient such that a three dimensional hands on surgery rehearsal platform is provided. 
         [0015]    The present disclosure provides a device that can simulate a spine as it is growing, simulating the growth of the vertebral bodies and the discs. 
         [0016]    In one embodiment, the device contains two sets of worm and worm gear mechanisms that are anchored to a spine model and to an angled bracket, respectively. The worm gear on the angled bracket may be driven by a screw driver or other such instrument, which, in turn, drives the worm on the spine model and drives a button that is attached to the worm gear of the spine model in an upward direction which, in turn, moves the vertebral bodies apart. 
         [0017]    The foregoing and other features, aspects, and advantages will become apparent to one skilled in the art to which the disclosed system and devices relate upon consideration of the following description of exemplary embodiments with reference to the accompanying drawings. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0018]      FIG. 1  is a top perspective view of a spine surgery modeling system in accordance with an embodiment of the present disclosure; 
           [0019]      FIG. 2   a  is an exploded view, with parts separated, of a drive mechanism and a vertebral body of the spine surgery modeling system of  FIG. 1 ; 
           [0020]      FIG. 2   b  is an assembled, perspective view of the drive mechanism attached to the vertebral body of  FIG. 2   a  in a collapsed state; 
           [0021]      FIG. 2   c  is a perspective view of a worm and a worm gear of the drive mechanism of  FIGS. 2   a  and  2   b;    
           [0022]      FIG. 2   d  is a perspective view of the drive mechanism attached to the vertebral body of  FIG. 2   a  in an expanded state; 
           [0023]      FIG. 3   a  is a side view of the spine surgery modeling system of  FIG. 1  in a pre-growth state; 
           [0024]      FIG. 3   b  is a side view of the spine surgery model system of  FIG. 1  in a post-growth state; 
           [0025]      FIG. 3   c  is an enlarged view of the area of detail  3 C of  FIG. 3   b  showing the worm and the worm gear of  FIG. 2   c  attached to vertebral bodies; 
           [0026]      FIG. 4   a  is a side view of the spine surgery modeling system of  FIG. 1  in a pre-growth state showing the drive mechanism of  FIG. 2   b  in cross-section; 
           [0027]      FIG. 4   b  is an enlarged view of the area of detail  4   b  of  FIG. 4   a  showing the vertebral bodies and the drive mechanisms in a pre-growth state; 
           [0028]      FIG. 4   c  is a side view of the spine surgery modeling system of  FIG. 1  in a post-growth state showing the drive mechanism of  FIG. 2   d  in cross-section; 
           [0029]      FIG. 4   d  is an enlarged view of the area of detail  4   d  of  FIG. 4   c  showing the vertebral bodies and the drive mechanisms in an expanded state; 
           [0030]      FIG. 5   a  is a perspective view of an angled bracket assembly of the spine surgery modeling system of  FIG. 1 ; 
           [0031]      FIG. 5   b  is an exploded view, with parts separated, of the angled bracket assembly of  FIG. 5   a ; and 
           [0032]      FIG. 6  is a top perspective view of a spine surgery modeling system in accordance with an alternate embodiment of the present disclosure. 
       
    
    
     DETAILED DESCRIPTION 
       [0033]    Detailed embodiments of the spine surgery modeling system of the present disclosure are disclosed herein; however, it is understood that the following description and each of the accompanying figures are provided as being exemplary embodiments of the present disclosure. Thus, the specific structural and functional details provided in the following description are non-limiting, and serve merely as a basis for the subject matter defined by the claims provided herewith. The device/system described below can be modified as needed to conform to further development and improvement of materials without departing from the disclosed concept. Accordingly, various modifications may be made without departing from the spirit and scope of the present disclosure. 
         [0034]    Embodiments of the present disclosure are now described in detail with references to the drawings in which like reference numerals designate identical or corresponding elements in each of the several view. As used herein, the term “clinician” refers to a doctor, nurse, or other care provider and may include support personnel. Throughout this description, the term “proximal” refers to the portion of a device or component thereof that is closer to a clinician and the term “distal” refers to the portion of a device or component thereof that is farther from a clinician. In addition, the term “cephalad” is used in this application to indicate a direction toward a patient&#39;s head, whereas the term “caudad” indicates a direction toward a patient&#39;s feet. Further still, for the purposes of this application, the term “lateral” indicates a direction toward a side of the body of a patient, i.e., away from the middle of the body of the patient, whereas “medial” refers to a position toward the middle of the body of a patient. The term “posterior” indicates a direction toward the patient&#39;s back, and the term “anterior” indicates a direction toward the patient&#39;s front. Additionally, in the drawings and in the description that follows, terms such as front, rear, upper, lower, top, bottom, and similar directional terms are used simply for convenience of description and are not intended to limit the disclosure. 
         [0035]    Referring now to  FIGS. 1-5   b , a spine surgery modeling system  10  includes a spine model  37 , a drive mechanism  30  attached to the spine model  37 , and a gear mechanism  20  attached to an angled bracket  26 . The spine model  37  and the angled bracket  26  may be attached to a base  12  of the spine surgery model system  10 . The drive mechanism  30  and the gear mechanism  20  are tethered to each other with a flexible shaft  50 . While the drive mechanism  30  and the gear mechanism  20  are discussed singularly, a person of ordinary skill in the art can readily appreciate that the spine surgery modeling system  10  of the present disclosure may also include a plurality of substantially identical drive mechanisms  30  and gear mechanisms  20  tethered together by flexible shafts  50 . 
         [0036]    The spine model  37  includes vertebral bodies  38  which define disc  39  spaces between adjacent vertebral bodies  38 . The spine model  37  is a model of a spinal column that can be selected by size and conformation to simulate, for example, pediatric, adult, and geriatric spinal columns. The spine model  37  may have one or more spinal constructs attached thereto, such as a rod  40  and/or other implant including, but not limited to, pedicle screws  60 . The spine model  37  may simulate common spinal deformities and other spinal abnormalities, and/or spinal growth via movement of the drive mechanism  30  and the gear mechanism  20 . Although the present disclosure refers to vertebral bodies  38 , the vertebral bodies  38  of the present disclosure are human analogues formed from artificial materials that have characteristics substantially similar to human vertebral bones. Suitable materials include polyurethane foams having either an open cell structure or a closed cell structure for emulating either cortical bone and/or cancellous bone. Other suitable analogues are commercially available from suppliers such as Pacific Research Laboratories, Inc. under the trade name SAWBONES®. 
         [0037]    As shown in  FIGS. 2   a - 2   d , in conjunction with  FIG. 1 , the drive mechanism  30  is inserted into a vertebral body  38  of the spine model  37 . The drive mechanism  30  includes a worm  32 , a rigid shaft  33 , a worm gear  34 , a pin  35 , and a button  36 . The rigid shaft  33 , which is attached to an end of the flexible shaft  50 , extends through the worm  32  and is pinned to the worm  32  via pin  35 . The worm  32  has threads  32   a  on an external surface thereof which engage teeth  34   a  on an external surface of the worm gear  34 . The button  36  extends into a through hole  34   b  of the worm gear  34  and includes partial threads  36   a  which engage threads  34   c  disposed in the through hole  34   b  of the worm gear  34 . Rotation of the rigid shaft  33  rotates the worm  32  which, in turn, rotates the worm gear  34  which, in turn, moves the button  36  in or out of the through hole  34   b  of the worm gear  34  depending on the direction of movement of the worm gear  34 . For example, as the rigid shaft  33  is rotated in the direction of arrow R in  FIG. 2   d , the button  36  moves in an upward direction along arrow G towards an expanded state and drives adjacent vertebral bodies  38  apart to represent an increase in disc  39  height, as shown, for example, in  FIGS. 3   a - 4   d . The button  36  may be moved in a downward direction towards a collapsed state (e.g.,  FIG. 2   b ) to represent a decrease in disc  39  height. 
         [0038]    As shown in  FIGS. 5   a  and  5   b , in conjunction with  FIG. 1 , the gear mechanism  20  is attached to the angled bracket  26  which together are part of an angled bracket assembly  25 . The gear mechanism  20  include a rigid shaft  21 , a worm gear  22 , and a worm  24 . The rigid shaft  21  is attached to an end of the flexible shaft  50  opposite the rigid shaft  33  of the drive mechanism  30 . The rigid shaft  21  extends through a hole  26   a  defined in the angled bracket  26 , a bushing  27   a , and the worm gear  22 . The worm gear  22  has teeth  22   a  which interact with threads  24   a  of the worm  24  and can transfer motion to the worm  24 . The bushing  27   a  is used with a bushing  27   b  having an adjustable screw  27   d  which may be loosened to move the rigid shaft  21  relative to the worm  24  and then tightened to keep the rigid shaft  21  in place so that the worm gear  22  does not disengage from the worm  24 . The bushings  27   a  and  27   b  may also be adjusted to move the rigid shaft  21  and disengage the worm gear  22  from the worm  24  or offset the position of the worm gear  22  relative to the worm  24  to change a rate of rotation of the worm gear  22 . The worm  24  is pinned in place onto a rigid shaft  28  via pin  28   a . The rigid shaft  28  is inserted through holes  23   c  defined in wall segments  23   b  of the angle bracket assembly  25  and into a bushing  27   c . The wall segments  23   b  are screwed into place on the angled bracket  26  through holes  26   b  in the angled bracket  26  via screws  23   a . An end  28   b  of the rigid shaft  28  can be attached to a driver or other like instrument in order to rotate the gear mechanism  20 . Rotation of the gear mechanism  20  causes a corresponding rotation of the rigid shaft  33  of the drive mechanism  30  via the flexible shaft  50 . 
         [0039]    In an exemplary method of use, a clinician will apply a rotational force to the rigid shaft  28  in order to cause the buttons  26  of the drive mechanisms  30  to move up in the direction of arrow G in  FIG. 2   d , which drives the vertebral bodies  38  further apart, as shown for example in  FIGS. 3   b  and  4   d , which simulates a spine growing as would happen in a child or young adult. A clinician may adjust the rigid shaft  21  of one or more gear mechanisms  20  to move the respective worm gears  22  relative to the worms  24  prior to applying the rotational force to the rigid shaft  28  to simulate a deformity or abnormality of the patient&#39;s spine. 
         [0040]    Referring now to  FIG. 6 , another embodiment of the spine surgery modeling system  10 ′ is shown. Spine surgery modeling system  10 ′ includes a spine model  37 , a drive mechanism  30  attached to the spine model  37 , and a gear mechanism  20  attached to an angled bracket  26 . Spine surgery modeling system  10  is substantially identical to spine surgery modeling system  10  except that it includes clutches  52  as are known in the art. Each clutch  52  is coupled to a flexible shaft  50  and each clutch  52  is independently operable to move the worm gear  22  of a respective gear mechanism  20  relative to the worm  24 . Accordingly, a clinician can individually engage or disengage each of the gear mechanisms  20  and control the rate of rotation of each gear mechanism  20 . This arrangement allows the clinician to manipulate the spine model  37  by controlling which vertebral bodies  38  are moved when the gear mechanisms  20  are actuated.