Biodegradable bone plates and bonding systems
Inventors
McCarthy, Stephen • Weinzweig, Jeffrey
Assignees
NOVAPLAST Corp • University of Massachusetts Lowell
Publication Number
US-9597133-B2
Publication Date
2017-03-21
Expiration Date
2027-04-13
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Abstract
The invention relates to novel internal fixation devices, such as bone plates, generally and novel craniomaxillofacial bone plates more specifically and systems for bonding the same. More specifically, the invention relates to bone plates made of a polymer blend of (poly)lactic acid and Ecoflex as well as a novel hot-melt adhesive polymer blend of the same material.
Core Innovation
The invention provides internal fixation devices, particularly bone plates, constructed from a polymer blend comprising (poly)lactic acid (PLA) and a flexible, compatible, biodegradable polyester-based polymer such as Ecoflex. These devices are specifically designed to be biodegradable and resorbable, enabling their use as medical implants such as craniomaxillofacial bone plates, hand fracture plates, and plates for osteotomies. The invention also introduces a novel hot-melt adhesive polymer blend, also based on PLA and Ecoflex, for affixing the internal fixation devices to human tissue.
The key problem addressed is the drawbacks of existing internal fixation devices, such as the need for screws and power equipment for drilling, extended resorption times of existing resorbable polymers, and the lack of options to introduce controlled porosity and bioactive molecules for enhanced bone healing. The current methods still require screws, tacks, or secondary fixation devices, leading to additional surgical time, operational cost, and limitations especially in pediatric and complex craniofacial cases.
This invention solves these limitations by designing fixation plates made from a blend of PLA and polyester-based polymers (notably Ecoflex), which can be bonded to tissue using the hot-melt adhesive of similar composition. This approach enables fixation without the need for screws, drilling, or secondary fixation devices. Furthermore, the structure of the plates allows for selective porosity, enabling impregnation with biologically-active molecules and earlier, controlled resorption tailored to the needs of bone healing. The invention also describes methods of sterilization, processing, and application of the devices and adhesives.
Claims Coverage
There are two primary independent inventive features described in the claims.
Method of bonding an internal fixation device by melting and affixing without drilling
This inventive feature covers: - Applying energy to an internal fixation device, specifically a plate, to melt at least a portion of it. - Contacting the melted portion with a surface of tissue. - Allowing the melted portion to harden, affixing the device to tissue without drilling or perforating the tissue. Additional aspects explicitly stated include use with resorbable bone plates, porous bone plates, and heating via devices such as lasers, hot air guns, soldering guns, or bovie tips in a temperature range from about 50°C to about 300°C. The fixation device comprises a first polymer in co-continuous phase with a second polymer, specifically PLA (or its copolymer) with a polyester-based polymer component. The tissue may be craniofacial bone.
Method for bonding without use of secondary fixation devices
This inventive feature covers: - Applying energy to the internal fixation device to melt at least a portion thereof (where the device is a plate). - Contacting the melted portion with tissue. - Allowing the melted portion to harden, so that adhesion is provided without the use of a secondary fixation device (such as a screw, pin, or additional bone plate). - The bonding relies on the direct interface between the plate and tissue—no additional component or substance supplying adhesion. The method includes aspects such as resorbable bone plates, porous bone plates, heating by various means (laser, hot air gun, soldering gun, bovie tip), operating in a temperature range of approximately 50°C to 300°C, and composition as a blend of a PLA- or PLA-based polymer and a polyester-based polymer, in co-continuous phase. The application is explicitly to tissue such as craniofacial bone.
In summary, the claims protect methods for bonding biodegradable internal fixation devices, notably bone plates made from specific PLA/polyester blends, by melting the device and directly adhering it to tissue without drilling, perforation, or secondary fixation devices. The invention further specifies use with resorbable and porous bone plates, various heating means, and a defined compositional structure.
Stated Advantages
Eliminates the need for screws, drilling, and associated power equipment during plate fixation, simplifying and expediting the intra-operative application of plates.
Permits controlled, earlier resorption of bone plates within 3–6 months, matching bone healing timelines and reducing the duration of foreign material presence compared to current systems.
Allows for impregnation of plates with biologically-active molecules due to controlled porosity, enhancing the potential for improved bone healing.
Reduces operating room time and cost by eliminating additional steps and equipment.
Offers superior mechanical properties (such as stiffness, toughness, and elongation to break) compared to pure PLA or other conventional plate materials.
Enables fixation without secondary fixation devices, which is valuable in scenarios where plate or screw use is contraindicated or not feasible.
Documented Applications
Use as bone plates for craniomaxillofacial surgery, including pediatric and reconstructive craniofacial procedures.
Bone plates for use in treating hand fractures.
Bone plates used in conjunction with osteotomies.
Plate-less bonding for stabilization of wounds or fractures at a site of interest, by direct application of the adhesive blend without external devices.
Stabilization of hand and craniofacial fractures where bone plates are contraindicated, such as fractures near articular surfaces or growth plates, non-displaced or minimally displaced fractures, comminuted fractures, or in elderly patients with inadequate bone stock.
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