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-11998255-B1
Publication Date
2024-06-04
Expiration Date
2043-09-30
Interested in licensing this patent?
MTEC can help explore whether this patent might be available for licensing for your application.
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. The tension member may be configured such that, at a minimum length of the bone screw, the tension member is pre-stretched so that the tension member is under tension to urge the bone screw to shorten. The bone screw may be inserted in the pre-stretched state. A pre-stretch driver may be used to tension the bone screw prior to or during insertion.
Core Innovation
The invention provides a bone screw system for insertion into bone, comprising a distal member with bone-engaging threads, a proximal member slidably engaging the distal member, and a tension member that couples both ends and is configured to elongate during relative motion. The tension member is designed so that when the distal member moves away from the proximal member, it is placed under tension and urges the distal member toward the proximal member, thereby applying compression across the bone portions.
The system further includes a proximal member head that resists insertion into the bone, so that distal advancement of the bone-engaging threads elongates the tension member. Engagement surfaces are provided between the proximal and distal members to transmit bending loads without transmitting torque. Additionally, a length limiting mechanism prevents the screw from extending beyond preset minimum and maximum lengths. The screw may be formed with a cannulated shaft for guidewire placement and may be pre-stretched prior to or during insertion using a pre-stretch driver, which enables controlled tensioning independently of engagement with bone.
According to the background, conventional bone screws may fail or loosen under bending loads, multi-axial forces, and off-axis loads, resulting in subsided initial compression and inadequate fixation over time. The present invention addresses this by maintaining continuous compression with a superelastic tension member, controlling elongation to avoid over-straining, and enabling pre-stretching for desired force application. This approach aims to improve bone fixation, stabilization and bone loading characteristics compared to existing systems.
Claims Coverage
The patent contains three independent claims, each specifying key inventive features related to a bone screw structure, an associated system, and an insertion method.
Bone screw with tension member for continuous compression
A bone screw comprises: - A distal member with bone-engaging threads. - A proximal member configured to slidably engage the distal member. - A tension member having a proximal end coupled to the proximal member and a distal end coupled to the distal member. When the distal member moves away from the proximal member, the tension member elongates and urges the distal member to return toward the proximal member. Additional inventive points explicitly mentioned: - The proximal member includes a head configured to resist insertion into bone so that elongation occurs with distal thread movement. - The proximal and distal members define a longitudinal axis; a distal engagement surface (distal member) and a proximal engagement surface (proximal member) are positioned so bending loads are transmitted from distal to proximal member, without transmitting torque about the longitudinal axis between those surfaces.
System for providing bone compression with pre-stretch driver
A system includes: - A bone screw with a distal member comprising bone-engaging threads and a proximal member resiliently coupled and slidably engaging the distal member. - A pre-stretch driver comprising: - A sleeve engaging the proximal member. - A driver shaft, slidably retained within the sleeve, that engages the distal member. - An actuator configured to urge the driver shaft distally relative to the sleeve, so the distal member is urged distally relative to the proximal member, elongating the bone screw. The system feature enables pre-stretching and tightening of the screw prior to or during insertion.
Method for bone screw insertion with tension member stretching
A method comprises: 1. Positioning a bone screw (comprising a distal member with bone-engaging threads, a proximal member slidably engaging the distal member, and a coupled tension member) near the bone. 2. With the screw at a minimum length, stretching the tension member from a relaxed to a stretched state. 3. Inserting the bone screw into the bone with the tension member in the stretched state. This process enables controlled pre-stretching of the tension member to apply desired compression upon insertion.
The inventive features establish a compressive bone screw with a tension member, a system with a pre-stretch driver for controlled elongation, and a method for pre-stretched insertion—each addressing continuous bone compression and mechanical load transfer without transmitting torque at the engagement surfaces.
Stated Advantages
The bone fixation devices provide improved fixation and stabilization between bone portions and/or implants, even under bending, multi-axial, and off-axis loads, compared to available bone screws.
The invention maintains a continuous, stable compressive force across the bone interface over time, addressing the loss of pressure in conventional bone fixation systems due to subsidence, resorption, or loosening.
The tension member, preferably formed of a superelastic material, allows for significant elongation while maintaining generally constant compression, which aids healing and osteogenesis.
A length limiting mechanism prevents over-elongation and potential failure of the tension member, providing safer and more predictable operation.
The system can be pre-stretched prior to or during insertion, optimizing the amount of compression applied and allowing more consistent compression post-insertion.
Engagement surfaces are designed to transmit bending loads efficiently without transferring torque, improving mechanical load handling.
Documented Applications
Trauma procedures, including fracture fixation.
Post-traumatic reconstruction, such as pelvic or joint fusions.
Spine procedures, including SI fusion and facet fixation.
Joint reconstruction procedures such as total hip arthroplasty and total knee arthroplasty.
Sports-related procedures.
Extremity procedures.
Cranio-maxillo-facial procedures.
Rib plating procedures.
Veterinary procedures.
Bone plating procedures such as femur plates, humerus plates, and tibial plates.
Intramedullary nail fixation procedures.
Amputee connection procedures.
Sarcoma procedures.
Shoulder/glenoid fixation.
Small bone fixation, correction, or fusion (e.g., foot/ankle, hand/wrist).
Joint fusions and osteotomies.
Procedures involving osteoporotic or compromised bone.
Interested in licensing this patent?