Cerclage Wire Tensioning Drum for Fracture Fixation
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Solution Overview
Problem
Cerclage systems often result in poor bone unions and wire migration due to high load on cerclage wires during femoral fractures, especially in total hip arthroplasty, where additional support is not desirable or possible.
Innovation Solution
A fracture fixation system comprising a medial and lateral plate connected by cerclage wires, with a tensioning drum mechanism to maintain wire tension, ensuring stable bone alignment and fusion by applying linear pressure without rotational force, thereby preventing wire migration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If cerclage wires are used for bone fixation, then the fixation method is simple and does not require additional support devices, but the high load on cerclage wires results in adjacent boney erosion and loss of fixation due to wire migration
Solution Approach 1:
A tensioning drum is introduced as an intermediary device between the cerclage wire and the bone. The drum maintains wire tension through a ratchet mechanism, preventing wire migration and boney erosion while keeping the overall fixation method relatively simple
Solution Approach 2:
The tension in the cerclage wire is dynamically adjusted and maintained at optimal levels using the tensioning drum. This parameter control prevents both excessive tension (causing erosion) and insufficient tension (causing migration), resolving the reliability issue
2Reliability
If additional support devices are used with cerclage, then bone union reliability is improved, but the device complexity and surgical invasiveness increase
Solution Approach 1:
The tensioning drum serves multiple functions: it maintains wire tension, prevents wire migration, reduces boney erosion, and facilitates bone union. This single multi-functional device replaces the need for multiple separate support devices, improving reliability while minimizing added complexity
3Reliability
If cerclage wire tension is increased to prevent migration, then fixation stability is improved, but adjacent boney erosion occurs due to excessive pressure
Solution Approach 1:
The tensioning drum incorporates a ratchet mechanism that provides mechanical feedback control. It maintains wire tension within safe limits, allowing sufficient tension for stability while preventing excessive tension that would cause boney erosion. The ratchet prevents over-tensioning by allowing tension application in one direction only
Data Source
AI summary
A fracture fixation system includes a plate having a laterally extending bore passing therethrough and configured to receive a first wire when the plate is placed in contact with a bone. The plate has a recess for receiving and securing a first end of a first wire, and includes an entry hole and an exit hole to at opposite ends of a first bore to allow the first wire to pass through the plate. A screw is configured to capture said the wire in the first bore to maintain a desired tension on the first wire.