Cannulated continuous compression screw
Inventors
Gregersen, Colin S. • Fallin, T. Wade • Saltzman, Charles L. • HAGMAN, Chase
Assignees
University of Utah • University of Utah Research Foundation Inc
Publication Number
US-12178485-B1
Publication Date
2024-12-31
Expiration Date
2043-09-30
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Abstract
A bone screw may be insertable into a bone. The bone screw may have a distal member with bone-engaging threads, a proximal member configured to slidably engage the distal member, and a tension member with a proximal end coupled to the proximal member, and a distal end coupled to the distal member such that, in response to motion of the distal member away from the proximal member, the tension member elongates and urges the distal member to move toward the proximal member.
Core Innovation
The invention provides a bone screw that is insertable into bone, featuring a distal member with bone-engaging threads, a proximal member configured to slidably and/or rotatably engage the distal member, and a tension member coupled between them. The tension member is designed such that its elongation, in response to motion of the distal member away from the proximal member, urges the distal member to return toward the proximal member, thereby applying continuous compression across bone interfaces.
This screw specifically addresses the problem encountered with traditional bone fixation systems, where initial compressive forces applied across bone interfaces subside over time due to factors like subsidence, motion, bone resorption, and loosening of the fastener. Additionally, conventional bone screws may not provide sufficient fixation and strength to withstand bending loads, multi-axial forces, or off-axis loading during healing, leading to fixation failure or loosening.
The disclosed device employs design features including a cannulated tension member (which may be made from a superelastic material), a length-limiting mechanism to maintain strain within desired limits, torque transmission features configured to minimize hoop stress, and specialized engagement surfaces for efficient transfer of bending loads. The proximal and distal members may have specifically shaped shanks, heads, and engagement features to optimize fixation, durability, and compatibility with surgical techniques such as insertion along a guide wire.
Claims Coverage
The independent claims cover several inventive features related to a bone screw with a variable length and continuous compression capabilities.
Bone screw with distal and proximal members, tension member, and direct driver engagement
A bone screw comprises a distal member with bone-engaging threads and a driver engagement feature, a proximal member with a proximal opening through which a driver can be inserted to engage the driver engagement feature, and is configured to slidably and rotatably engage the distal member. The device includes a tension member having proximal and distal ends coupled respectively to the proximal and distal members so that, when the distal member moves away from the proximal member, the tension member elongates and urges the distal member toward the proximal member.
Variable-length bone screw with differing shaft widths
A bone screw includes a distal member with bone-engaging threads, a proximal member configured to slidably and rotatably engage the distal member resulting in minimum and greater maximum lengths, and a tension member coupled between them. The proximal shaft has a greater width than the distal shaft at both minimum and maximum lengths.
Bone screw with shafts of circular cross-section maintained at both lengths
A bone screw wherein the proximal member has a proximal shaft and the distal member has a distal shaft, and both shafts exhibit circular cross-sectional shapes from the portion of the proximal shaft adjacent the head to the portion of the distal shaft adjacent the bone-engaging threads, maintained both at minimum and maximum screw lengths.
Bone screw with distal driver engagement directly insertable and removable
A bone screw with a distal member having bone-engaging threads and a driver engagement feature, a proximal member configured to slidably engage the distal member such that the driver engagement feature remains accessible, and a tension member coupled as above. When fully assembled, the driver engagement feature can mate with a driver for direct torque application for insertion and removal of the screw.
Bone screw with distalmost rim of proximal member not abutting at minimum length
A bone screw where the proximal member comprises a proximal shaft with a proximal shaft width, the distal member comprises a distal shaft with a distal shaft width, the proximal shaft width is greater than the distal shaft width, and the proximal member has a distal-most rim that does not abut the distal member at the minimum length.
Bone screw with driver engagement feature accessible through proximal opening
A bone screw wherein the distal member provides bone-engaging threads and a driver engagement feature configured to mate with a driver for direct torque input, the proximal member is configured to slidably engage the distal member such that the driver engagement feature is accessible while the members are engaged, and the proximal member includes a proximal opening through which the driver is insertable to engage the driver engagement feature.
Bone screw providing for a rotatable engagement between proximal and distal members
A bone screw wherein the proximal member is configured to rotatably engage the distal member in addition to being able to slide relative to it, facilitating torque transmission and positional adjustments.
Bone screw with constant cross-sectional distal shaft and length limiting mechanism
A bone screw wherein at each minimum and maximum length, the distal shaft has a constant cross-sectional shape from the proximal member to the bone-engaging threads, and the screw includes a length limiting mechanism configured to prevent the overall length from exceeding a maximum or falling below a minimum.
The claims collectively protect a bone screw system featuring a variable-length mechanism using a tension member for continuous compression, direct and modular driver engagement, dimensional optimizations between shaft segments, and safety mechanisms to prevent overextension or over-shortening, suitable for variable bone fixation needs.
Stated Advantages
Provides improved bone fixation and stabilization between two or more bone portions or implants.
Maintains continuous compressive force across the bone interface, even after subsidence, bone motion, or loosening.
Offers better resistance to bending loads, multi-axial forces, and off-axis loading scenarios during the healing process.
Prevents over-elongation and potential failure by incorporating a length-limiting mechanism.
Torque transmission features minimize hoop stress, increasing mechanical strength of the device under load.
Enhances healing of fractures and fusion by sustaining pressure at the bone interface.
Facilitates use with guidewires and various surgical insertion techniques.
Documented Applications
Trauma procedures such as fracture fixation.
Post-traumatic reconstruction including pelvic or joint fusion.
Spine procedures including SI fusion and facet fixation.
Joint reconstruction procedures such as total hip and total knee arthroplasty.
Sports-related procedures.
Extremity procedures.
Cranio-maxillo-facial procedures.
Rib plating procedures.
Veterinary procedures.
Bone plating procedures, such as femur, humerus, or tibial plates.
Intramedullary nail fixation procedures.
Amputee connection procedures.
Sarcoma procedures.
Shoulder/glenoid fixation.
Small bone fixation, correction, or fusion including foot/ankle and hand/wrist.
Osteotomies and procedures involving osteoporotic or compromised bone.
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