Contoured Bone Plate With Differential Locking Screw Compression
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Solution Overview
Problem
Existing surgical methods for aligning and fixing bones are inadequate in efficiently realigning and fixing bones, particularly in anatomically misaligned bones, such as those in the foot, to achieve effective angular correction and promote healing.
Innovation Solution
A bone plate with a bend and locking screws that deform to apply asymmetric compression across bone ends, using screws with differential threading to interlock and compress the plate, facilitating angular correction and healing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a standard bone plate is used to fixate bones, then the bones can be held in position, but effective angular correction and compression cannot be achieved
Solution Approach 1:
The bone plate incorporates a bend that creates asymmetric geometry, allowing differential compression across the bone interface. This asymmetric design enables angular correction by positioning the plate to leverage compressive forces on one side of the bone joint, facilitating realignment while promoting healing through controlled compression.
Solution Approach 2:
The locking screw utilizes differential threading with different pitch values on the head portion versus the shaft portion. This parameter change allows the screw to simultaneously achieve interlocking (through head thread engagement) and compression (through shaft thread engagement with greater pitch), transforming a single fastening action into a dual-function mechanism for both fixation and compression.
2Strength
If a locking screw with uniform threading is used, then the bone plate can be secured to bone, but compression between bone ends cannot be achieved
Solution Approach 1:
The locking screw features local quality variation through differential threading, where the head portion has one pitch value for interlocking with the bone plate, while the shaft portion has a different pitch value for generating compression. This localized differentiation allows each section of the screw to perform its specific function optimally without compromising the other.
3Productivity
If the bone plate is deformed to apply compression, then healing is promoted, but the plate may lose structural integrity
Solution Approach 1:
The bone plate is pre-formed with a controlled bend during manufacturing, creating a stored elastic energy state. When the locking screw is inserted and tightened, this pre-positioned bend allows the plate to deform in a controlled manner, applying compression to the bone while the differential screw threading ensures the deformation remains within structural limits, maintaining integrity while promoting healing.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The bone plate system effectively aligns and fixes misaligned bones by applying asymmetric compression, promoting healing and reinforcing the corrected alignment.
Implementation Method 1
The shaft thread has a pitch greater than a pitch of the head thread... causing the bone plate to deform when the head thread is fully engaged with the threading defined by the first fixation hole and the screw is further turned
Data Source
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AI summary
A method of applying a bone plate across a tarsometatarsal joint or two different portions of a metatarsal may involve positioning a bone plate across a separation between two bone portions. The bone plate can have at least two fixation holes and a bend between the holes. A locking screw can be inserted through one or both holes that has a head thread and a shaft thread, where the shaft thread has a pitch greater than a pitch of the head thread. The locking screw can be screwed into an underlying bone portion until the bend in the bone plate is deformed.