Locked plates use and abuse Anders Jordy Traumesektoren, Kolding Sygehus AO advanced principles Middelfart, april 2016
Learning outcomes Compare indications for using locked and nonlocked plates. Identify indications for the use of locked plating techniques vs conventional plating techniques. Formulate the advantages of locked plates in special clinical circumstances, e.g.. osteoporosis. Identify patient populations where plates are most useful. Outline areas where locking compression plates may fail or may be used incorrectly leading to failure.
Locking plates - principper En intern ekstern fixator Ikke synonymt med bridging plate men meget anvendelig som bridging plate Stabiliteten opnås idet skinne og skrue låses til hinanden og bliver et Således er stabiliteten ikke afhængig af friktion mellem knogle og skinne Skinnen skal nu ikke længere presses mod knoglen, men kan svæve Locking kan referere til to pointer: Skinne og skrue låses Det gør knoglen også kan ikke flyttes mod skinnen efterfølgende > derfor lack before you lock
Locking plates advantages Opnår stabilitet med færre skruer Således har locking plates gjort det muligt at opnå bedre stabilitet ved osteosyntese af lednære frakturer Låsningen medføre vinkelstabilitet Større pull-out styrke Giver mulighed for MIPO teknik Blodforsyning i knogle bevares bedre da knoglen ikke får tryksår
Locking plates - disadvantages Større pull-out flytter stress til et andet sted, hvor der kan opstå fraktur Når du har låst så har du låst Tekniske problemer Skruehovedet låser ikke Går skævt i Koldsvejser Skruer bliver for lange Får kirurger der ikke har været på AO til at glemme basale principper
Optimize fixation hvordan kan man variere fixationsstyrken når man anvender locking plates? The strength and stability of a fixation performed using the locking plate can be altered by the following factors: Poitioning of screws Number of screws Plate length
Screw placement Stoffel K et al (2003) Injury Working length Moving first screw further from fracture site: Increases the working length Decreases axial load by 64%, decreases torsional rigidity by 36% Increasing working length by leaving a single screw hole unfilled will decrease stability by 10% bridging length screw holes 6, 1 6, 3 6, 5
Application principles flexible or stiff? How many screws and in what positions for relative stability? stress dissipation stress concentration
Screw number Stoffel K et al (2003) Injury A 3rd screw increases axial stiffness, not torsional rigidity (only number of screws) The closer a 3rd screw is positioned to fracture gap, the stiffer a construct number of screws screw holes 6, 2, 1 6, 5, 4, 3, 2, 1 6, 4, 3 6, 5, 4, 3
Avoid short middle
Length of LCP relative stability Plate length should be at least 2 or 3 times fracture length [Gautier E, et al 2003]
Clinical indications for locked plating Osteopenia/osteoporosis Metaphyseal comminution or short metaphyseal fragment Periprosthetic fractures Special circumstance Early unprotected weightbearing, eg, a noncompliant patient Osteotomies MIPO
Complications Failure to achieve reduction Screw heads not locked Inability to remove screws Too little or too much fixation Penetration of joint surface by implant Mixed techniques - relalut stabilitet Catastrophic failure
Pitfalls that can lead to failure Der er flere fælder ved brug af locking plates Her er nogle eksempler
Which screw type for Gautier E et al (2003) Dept of Orthop Surg Monocortical Excellent bone quality Diaphyseal bone Bicortical Poor bone quality If in any doubt always use bicortical screws.
Osteoporotic bone and working length Gautier E et al (2003) Dept of Orthop Surg sufficient working length good bone quality insufficient working length osteoporotic bone
Screw pull-out and cut-out
Screws locked but not inserted in bone
Failure to achieve locking of the screw heads into the plate cross threading
Screws penetration of the joint surface Unforgiving cortical protrusion with articular erosion intraoperative error
Misapplication failure to achieve reduction OIF instead of ORIF No R = no Reduction
Failure to achieve reduction Distal femur: valgus
Catastrophic failure Osteoporotic bone Stiff constructs Larger core diameter screws
Summary LCP can be used to achieve absolute or relative stability Use longer plates and leave more screw holes unfilled Achieving a good functional reduction is critical before application of the plate New complications occur due to lack of tactile feedback ie, penetration of the joint, plates not actually on the bone AO-danmark.dk