The Experts below are selected from a list of 354 Experts worldwide ranked by ideXlab platform

Johnson, Wesley M. - One of the best experts on this subject based on the ideXlab platform.

  • Adaptation sphere saddle
    Digital Commons @ University of South Florida, 2018
    Co-Authors: Johnson, Wesley M., Freeman, Thomas B.
    Abstract:

    An improvement of a Polyaxial Screw head disclosed in the U.S. Pat. No. 8,277,490. A saddle resides within a tulip. The saddle is configured to mate with a rod. An outer set Screw engages an inner surface of the tulip. An inner set Screw is disposed within a lumen of an outer set Screw. A force distributor has a concave surface configured to mate with the rod. The force distributor has a bore configured to accept a conical end of the inner set Screw. The force distributor is configured to distribute the force applied onto the bore by the inner set Screw along the contact area with rod. The force distributor allows the rod to pivot and have sagittal motion when the inner set Screw is untightened. The force distributor immobilizes the rod within the saddle when the inner set Screw is tightened

  • Apparatus for occipital-cervical fixation enabling supplemental occipital bone fixation
    Scholar Commons, 2016
    Co-Authors: Uribe, Juan S., Johnson, Wesley M.
    Abstract:

    An apparatus for stabilization of a patient\u27s head relative to the patient\u27s neck joint includes an occi-cervical base member having a “C”-shaped central part and first and second attachment rods respectively connected to and extending transversely from free ends of the central part. An occiput attachment has a first end slideably engaged to the central part and a flat, straight second end that extends radially outwardly relative to the first end. First and second Polyaxial Screw heads are adapted to be implanted in first and second occipital condyles of a patient, respectively. The first and second Polyaxial Screw heads are adapted to engage first and second stabilizing rods, respectively, that are placed in-line with the cervical spine of a patient and to engage the first and second attachment rods, respectively

  • Apparatus for occipital-cervical fixation enabling supplemental occipital bone fixation
    Scholar Commons, 2013
    Co-Authors: Uribe, Juan S., Johnson, Wesley M.
    Abstract:

    An apparatus for stabilization of a patient\u27s head relative to the patient\u27s neck joint includes an occi-cervical base member having a shaped “C”-shaped central part and first and second attachment rods respectively connected to and extending transversely from free ends of the central part. An occiput attachment has a first end slideably engaged to the central part and a flat, straight second end that extends radially outwardly relative to the first end. First and second Polyaxial Screw heads are adapted to be implanted in first and second occipital condyles of a patient, respectively. The first and second Polyaxial Screw heads are adapted to engage first and second stabilizing rods, respectively, that are placed in-line with the cervical spine of a patient and to engage the first and second attachment rods, respectively

  • Translational manipulation Polyaxial Screw head
    Digital Commons @ University of South Florida, 2012
    Co-Authors: Freeman, Thomas B., Johnson, Wesley M.
    Abstract:

    A novel surgical Screw is presented as a Polyaxial, multiaxial, or monoaxial Screw. The Polyaxial Screw allows versatile angulation between a bone anchor section and a Screw body and allows the surgeon to attach a rod to the invention in a top-loading manner and manipulate the rod to accommodate a patient\u27s body and the surgical goals. The Screw uses a rod saddle to seat a rod, and permits the surgeon to sagitally manipulate the rod. After implantation of the Screw and insertion of the rod, a locking Screw is used to fix the angle and position of the rod and Screw body

Michael Blauth - One of the best experts on this subject based on the ideXlab platform.

  • influence of Screw positioning in a new anterior spine fixator on implant loosening in osteoporotic vertebrae
    Spine, 2006
    Co-Authors: M Reinhold, Karsten Schwieger, Joerg Goldhahn, Berend Linke, Christian Knop, Michael Blauth
    Abstract:

    STUDY DESIGN: A biomechanical study was designed to assess implant cut-out of three different angular stable anterior spinal implants. Subsidence of the implant relative to the vertebral body was measured during an in vitro cyclic loading test. OBJECTIVES: The objective of the study was to evaluate two prototypes (Synthes) of a new anterior spine fixator with different Screw angulations in comparison to the established MACSTL(R) Twin Screw Concept (Aesculap). The influence of factors like load-bearing cross-sectional area, Screw angulation and bone mineral density upon implant stability should be investigated. SUMMARY OF BACKGROUND DATA: Epidemiologic data predict a growing demand for appropriate anterior spinal fixation devices especially in patients with inferior structural and mechanical bone properties. Although different concepts for anterior spinal instrumentation systems have been tried out, implant stability is still a problem. METHODS: Three angular stable, anterior spinal implants were tested using 24 human lumbar osteoporotic vertebrae (L1-L5; age 84 (73-92)): MASC TL system (Aesculap); prototype 1 (MP1) with 18 degrees and prototype 2 (MP2) with 40 degrees Screw angulation (both Synthes). All implants consisted of two Screws with different outer Screw diameters: 7-mm Polyaxial Screw with 6.5-mm stabilization Screw (MASC TL), two 5-mm locking-head Screws each (MP1 and MP2). Bone mineral density (BMD) and vertebral body width of the three specimen groups were evenly distributed. The specimens were loaded in craniocaudal direction (1Hz) for 1000 cycles each at three consecutive load steps; 10-100 N, 10-200 N and 10-400 N. During cyclic loading subsidence of the implant relative to the vertebral body was measured in the unloaded condition. Cycle number at failure (defined as a subsidence of 2 mm) was determined for each specimen. A survival analysis (Cox Regression) was performed to detect differences between implant groups at a probability level of 95%. RESULTS: High correlations were found between BMD and number of cycles until failure (MP1; r = 0.905, P = 0.013; MP2: r = 0.640, P = 0.121; MACS TL: r = 0.904, P = 0.013) and between load bearing cross sectional area and number of cycles until failure (MP1: r = 0.849, P = 0.032;MP2: r = 0.692, P = 0.085; MACS TL: r = 0.902, P = 0.014). Both Prototypes survived significantly longer than the MACS TL implant (MP1: P = 0.012, MP2: P = 0.014). The survival behaviour of MP1 and MP2 was not significantly different (P = 0.354). CONCLUSIONS: Implant stability within each implant group was influenced by BMD and load bearing cross-sectional area. The angulation of the two Screws did not have a significant influence on cut-out. As conclusion from this study, promising approaches for further implant development are: 1) increase of load-bearing cross-sectional area (e.g., larger outer diameter of the anchorage device), 2) Screw positioning in areas of higher BMD (e.g., opposite cortex, proximity to pedicles or the endplates).

  • influence of Screw positioning in a new anterior spine fixator on implant loosening in osteoporotic vertebrae
    Spine, 2006
    Co-Authors: M Reinhold, Karsten Schwieger, Joerg Goldhahn, Berend Linke, Christian Knop, Michael Blauth
    Abstract:

    Study Design. A biomechanical study was designed to assess implant cut-out of three different angular stable anterior spinal implants. Subsidence of the implant relative to the vertebral body was measured during an in vitro cyclic loading test. Objectives. The objective of the study was to evaluate two prototypes (Synthes) of a new anterior spine fixator with different Screw angulations in comparison to the established MACSTL® Twin Screw Concept (Aesculap). The influence of factors like load-bearing cross-sectional area, Screw angulation and bone mineral density upon implant stability should be investigated. of Background Data. Epidemiologic data predict a growing demand for appropriate anterior spinal fixation devices especially in patients with inferior structural and mechanical bone properties. Although different concepts for anterior spinal instrumentation systems have been tried out, implant stability is still a problem. Methods. Three angular stable, anterior spinal implants were tested using 24 human lumbar osteoporotic vertebrae (L1-L5; age 84 (73-92)): MASC TL system (Aesculap); prototype 1 (MP1) with 18° and prototype 2 (MP2) with 40° Screw angulation (both Synthes). All implants consisted of two Screws with different outer Screw diameters: 7-mm Polyaxial Screw with 6.5-mm stabilization Screw (MASC TL), two 5-mm locking-head Screws each (MP1 and MP2). Bone mineral density (BMD) and vertebral body width of the three specimen groups were evenly distributed. The specimens were loaded in craniocaudal direction (1Hz) for 1000 cycles each at three consecutive load steps; 10-100 N, 10-200 N and 10-400 N. During cyclic loading subsidence of the implant relative to the vertebral body was measured in the unloaded condition. Cycle number at failure (defined as a subsidence of 2 mm) was determined for each specimen. A survival analysis (Cox Regression) was performed to detect differences between implant groups at a probability level of 95%. Results. High correlations were found between BMD and number of cycles until failure (MP1; r = 0.905, P = 0.013; MP2: r = 0.640, P= 0.121; MACS TL: r = 0.904, P = 0.013) and between load bearing cross sectional area and number of cycles until failure (MP1: r = 0.849, P = 0.032; MP2: r = 0.692, P = 0.085; MACS TL: r = 0.902, P = 0.014). Both Prototypes survived significantly longer than the MACS TL implant (MP1: P = 0.012, MP2: P = 0.014). The survival behaviour of MP1 and MP2 was not significantly different (P = 0.354). Conclusions. Implant stability within each implant group was influenced by BMD and load bearing cross-sectional area. The angulation of the two Screws did not have a significant influence on cut-out. As conclusion from this study, promising approaches for further implant development are: 1) increase of load-bearing cross-sectional area (e.g., larger outer diameter of the anchorage device), 2) Screw positioning in areas of higher BMD (e.g., opposite cortex, proximity to pedicles or the endplates).

Kevin T Foley - One of the best experts on this subject based on the ideXlab platform.

  • percutaneous pedicle Screw fixation of the lumbar spine preliminary clinical results
    Journal of Neurosurgery, 2002
    Co-Authors: Kevin T Foley, S Gupta
    Abstract:

    Object. Standard techniques for pedicle Screw fixation of the lumbar spine involve open exposures and extensive muscle dissection. The purpose of this study was to report the initial clinical experience with a novel device for percutaneous posterior fixation of the lumbar spine. Methods. An existing multiaxial lumbar pedicle Screw system was modified to allow Screws to be placed percutaneously by using an extension sleeve that permits remote manipulation of the Polyaxial Screw heads and remote engagement of the Screw-locking mechanism. A unique rod-insertion device was developed that linked to the Screw extension sleeves, allowing for a precut and -contoured rod to be placed through a small stab wound. Because the insertion device relies on the geometrical constraint of the rod pathway through the Screw heads, minimal manipulation is required to place the rods in a standard submuscular position, there is essentially no muscle dissection, and the need for direct visual feedback is avoided. Twelve patients ...

  • percutaneous pedicle Screw fixation of the lumbar spine
    Neurosurgical Focus, 2001
    Co-Authors: Kevin T Foley, Sanjay K Gupta, Jeff R Justis, Michael C Sherman
    Abstract:

    Object Standard techniques for lumbar pedicle Screw fixation involve open exposures and extensive muscle dissection. The purpose of this study was to report the initial clinical experience with a novel device for percutaneous posterior fixation of the lumbar spine. Methods An existing multiaxial lumbar pedicle Screw system was modified so that Screws could be placed percutaneously by using an extension sleeve that would allow for remote manipulation of the Polyaxial Screw heads and remote engagement of the Screw locking mechanism. A unique rod insertion device was developed that linked to the Screw extension sleeves, allowing for a precut, precontoured rod to be placed through a small stab wound. Because the insertion device relies on geometrical constraint of the rod pathway through the Screw heads, rods can be placed in a standard submuscular position with minimal manipulation, essentially no muscle dissection, and without the need for direct visual feedback. Twelve patients (six men and six women who r...

Robert P Melcher - One of the best experts on this subject based on the ideXlab platform.

  • posterior c1 c2 fusion with Polyaxial Screw and rod fixation
    Spine, 2001
    Co-Authors: Jurgen Harms, Robert P Melcher
    Abstract:

    Study Design. A novel technique of atlantoaxial stabilization using individual fixation of the C1 lateral mass and the C2 pedicle with miniPolyaxial Screws and rods is described. In addition, the initial results of this technique on 37 patients are described. Objectives. To describe the technique and the initial clinical and radiographic results for posterior C1-C2 fixation with a new implant system. Summary of Background Data. Stabilization of the atlantoaxial complex is a challenging procedure because of the unique anatomy of this region. Fixation by transartic-ular Screws combined with posterior wiring and structural bone grafting leads to excellent fusion rates. The technique is technically demanding and has a potential risk of injury to the vertebral artery. In addition, this procedure cannot be used in the presence of fixed subluxation of C1 on C2 and in the case of an aberrant path of the vertebral artery. To address these limitations, a new technique of C1-C2 fixation has been developed: bilateral insertion of Polyaxial-head Screws in the lateral mass of C1 and through the pars interarticularis into the pedicle of C2, followed by a fluoroscopically controlled reduction maneuver and rod fixation. Methods. After posterior exposure of the C1-C2 complex, the 3.5-mm Polyaxial Screws are inserted in the lateral masses of C1. Two Polyaxial Screws are then inserted into the pars interarticularis of C2. Drilling is guided by anatomic landmarks and fluoroscopy. If necessary, reduction of C1 onto C2 can be accomplished by manipulation of the implants, followed by fixation to the 3-mm rod. For definitive fusion, cancellous bone can be added. No structural bone graft or wiring is required. In selected cases, e.g., C1-C2 subluxation or fractures in young patients in whom only temporary fixation is necessary, the instrumentation can be removed after an appropriate time, Because the joint surfaces stay intact, the patient can regain motion in the C1-C2 joints. Results. Thirty-seven patients underwent this procedure. No neural or vascular damage related to this technique has been observed. The early clinical and radiologic follow-up data indicate solid fusion in all patients. Conclusion. Fixation of the atlantoaxial complex using Polyaxial-head Screws and rods seems to be a reliable technique and should be considered an efficient alternative to the prevlously reported techniques.

Michael C Sherman - One of the best experts on this subject based on the ideXlab platform.

  • percutaneous pedicle Screw fixation of the lumbar spine
    Neurosurgical Focus, 2001
    Co-Authors: Kevin T Foley, Sanjay K Gupta, Jeff R Justis, Michael C Sherman
    Abstract:

    Object Standard techniques for lumbar pedicle Screw fixation involve open exposures and extensive muscle dissection. The purpose of this study was to report the initial clinical experience with a novel device for percutaneous posterior fixation of the lumbar spine. Methods An existing multiaxial lumbar pedicle Screw system was modified so that Screws could be placed percutaneously by using an extension sleeve that would allow for remote manipulation of the Polyaxial Screw heads and remote engagement of the Screw locking mechanism. A unique rod insertion device was developed that linked to the Screw extension sleeves, allowing for a precut, precontoured rod to be placed through a small stab wound. Because the insertion device relies on geometrical constraint of the rod pathway through the Screw heads, rods can be placed in a standard submuscular position with minimal manipulation, essentially no muscle dissection, and without the need for direct visual feedback. Twelve patients (six men and six women who r...