lcp a clinical update

8/6/2019 LCP a Clinical Update

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Locked Plating in OrthopaedicTrauma: A Clinical Update

J Am AcadOrthopSurgJune 2008

George J. Haidukewych, MD

William Ricci, MD


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Abstract

.Locked plating for fracture fixation has enjoyedwidespread popularity despite a paucity of publisheddata on outcomes..Anatomically precontouredlocked plates that allow

fixation in various anatomic regions are widelyavailable..New technologies incorporate-Subchondralsupport locking pegs-Polyaxialbushings-Locking washers

To improve intraoperativeversatility


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.However, limited data are available on the efficacy ofthese new implants.


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.The clinical performance of locked plates generallyhas been good..However, several unique complications have beennoted, such as-Difficulty with implant removal-Malalignment

-Fracture distraction-Loss of diaphysealfixation, especially withpercutaneoustechniques and unicorticalscrews.


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.The expense of locked plate constructs is a concern.

.This technology typically costs three times more thansimilar unlocked constructs..Locked constructs should be reserved for problematicfractures that have demonstrated poor outcomeswith unlocked constructs


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Innovations in Locked PlateDesign and Surgical Techniques

.The first commercially available locked plate designedfor periarticularfracture fixation was the-Less Invasive Stabilization System (LISS)

.This titanium alloy, fixed trajectory locking plate withinstrumentation optimized for percutaneousinsertiondemonstrated a clear advantage over traditionalplates with regard to-Union rates without secondary surgery-Improved end-segment fixation


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.The LISS system relies on unicorticalshaft fixationand self-drilling, self-tapping screws..Published data have been encouraging..However, malalignmentis not infrequent, even whenused by experienced surgeons


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Anteroposteriorradiograph demonstrating malalignmentof a distal femoral fracturetreated percutaneously


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.Many locked plating designs are now available.

.In general, the designs fit into two broad categories-Those with fixed-trajectory locking screws-Those that allow variable axis screw locking


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.Unicorticalscrew fixation for the diaphysealportionof periarticularplating, popular in first-generationlocked plates, has been an area of concern, primarilybecause-Such constructs exhibit weakness in torsion,especially in patients with very thin cortices


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Anteroposteriorradiograph demonstrating proximal unicortical

screw fixation failure in an osteopenicpatient, resulting innonunion.


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.This unique complication of first-generation lockedplates has driven the development of plates withscrew holes that accept a variety of screw types.Currently, locking screws typically are inserted afterpredrillingholes..This allows tactile confirmation of bicorticalpurchase,

which may assist the surgeon in confirming plateposition on the diaphysis..No shaft fixation failure has been reported with theuse of bicorticalfixation


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.In these situations it may be difficult, if notimpossible, to achieve long screw fixation inperiarticularsegments.Since the screw trajectory is determined by themanufacturer.-The surgeon would have to either place a shorter

screw or-Angle the screw within a fixed trajectory lockinghole, resulting in cross-threading.


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.Even at small degrees of angulation(=5), crossthreading has been demonstrated biomechanically tosignificantly decrease the fixation strength at thescrew-plate interface


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.As a result, some manufacturers have introducedplates that allow screws to be angled, then locked atend-point tightening..Most of these designs rely on some sort of hoopstress and an additional interface between the screwhead and the plate.

.However, few data exist regarding their mechanicalstrength and clinical outcomes.


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.Any fixation that relies on an additional interfacebetween the screw and the plate rather than simplyon a corresponding threaded hole likely will notprovide equivalent mechanical strength


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.To date, no published comparative biomechanicalstudies exist regarding the various types of lockedplates.


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.Although the great majority of locking plates havebeen specifically anatomically designed forproblematic periarticularfractures, such as-Distal femur-Proximal tibia-Proximal humerus

-Distal radius,

Locking small-and large fragment straight platingsets are now available.


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.The indications for these plates remain undefined.

.Fractures that have historically been treatedsuccessfully with traditional plates (eg, humeralshaft, both-bone forearm, lateral malleolus)

require locked fixation only in

-very osteopenicpatients-Those with segmental loss or short end segmentsas a result of comminution.


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.The expense of a locked plating construct issubstantially higher than that of an equivalentunlocked construct..Much of the cost of such constructs is due to thelocking screws themselves, not the plates..Most systems now offer the surgeon the

.choice of inserting a locked or unlocked screwthrough the same hole.Thus ,the cost of various screw choices should beconsidered


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.Often ,traditional screws can be used to compressfractures and pull the plate down to bone,facilitating reduction..Locking screws can be used to further stabilize theconstruct..This hybridization of locked and unlocked

technologies was not available with first-generationlocking plates,


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.It is prudent to reserve locked plating for problematicfractures for which unlocked plates havedemonstrated an increased rate of mechanical failureeg-Proximal humerus-Distal radius

-Distal femur-Proximal tibia.


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Indications for Locked Plating

.Fractures for Which There Are Published DataSupporting the Use of Locked Plating-Intra-articularfracture of the distal femur,proximal tibia, distal radius

-Short, extra-articularmetaphysealfracture-Proximal humerusfracture, especially in theosteopenicpatient-Periprostheticfracture below THR-Periprostheticfracture above TKR-Nonunion of the humerus


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.Fractures for Which There Are Little or No ClinicalData to Support the Routine Use of Locked Plating-Diaphysealfracture of the forearm-Diaphysealfracture of the humerus-Fractures of the clavicle-Pediatric femur fracture

-Fibula (ankle) fracture-Fracture of the distal tibia and pilonfracture-Unicondylar(type B) fracture of the distal femurand proximal tibia-Intertrochantericor subtrochantericfracture


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Locked Plating of Fractures of theUpper Extremity.The relative advantages of locked plating-Improved fixation of metaphysealfractures that

are prone to collapse

-Improved fixation in osteoporotic bone

Make fractures of the proximal humerusand distalradius the upper extremity fractures most suited tobenefit from the application of locked plating

technology.


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Distal Radius Fracture.Associated with fewer complications than is lockedplating of proximal humerusfractures.Mechanical failures have been rare because of thereduced loads about the wrist.Although minor amounts of collapse of the distal

fragment have been reported.In general, union rates and time to union have beensatisfactory for locked plating of distal radiusfractures..Average time to union has been reported to bebetween 7 and 8 weeks


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.Alignment at union and range of motion (ROM) alsohave been generally satisfactory.One of the reported benefits of locked plating fordistal radius fractures is the safety of early ROMowing to the improved stability of the lockedconstruct.

.This is true even for comminuted fractures


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Anteroposterior(A) and lateral (B) radiographs of an unstable distal radiusfracture in a 50-year-old man. Anteroposterior(C) and lateral (D) postoperativeradiograph following internal fixation with a volarlocking plate. The fractureunited without complications


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Proximal HumerusFracture.Locked plates designed specifically for the proximalhumerushave in common multiple fixed-angle points

of fixation into the humeral head.

.Each screw acts as a miniature blade plate, with theadded benefit of providing fixed-angle support inmultiple planes


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.Recently, the importance of inferomedialscrewplacement in minimizing varuscollapse has beendemonstrated


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.When satisfactory fixation of the locked screws isachieved in the humeral head, stresses may becomeconcentrated at other areas of the construct..Locked screws may fracture at the plate interface.Without proximal failure.Stresses can become concentrated over the working

distance of the plate in the zone of the surgical neck,where fracture comminutionoften prevents screw

fixation


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.Despite these multiple potential modes of failure,evidence suggests that locked plating offers improved

fixation relative to other methods of internal fixation


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.Evidence suggests relatively low rates of fixationfailure, nonunion, and other complications.Average shoulder outcome scores have generallybeen good and have been remarkably consistent

after locked plating


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.In only one study has locked plating been directlycompared with other treatment methods for proximalhumerusfracture..In 2003, Lungershausenet al retrospectivelyreviewed 51 patients with Neertypes 2, 3, and 4proximal humerusfractures treated with locked

plating..The authors compared the results of the 24 patientsavailable for follow up with those of 32 patientstreated with conventional open reductionandinternalfixation without locking.


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.The risk of osteonecrosisis often cited as a relativeindication for shoulder arthroplastyin the patientwith a three-or four-part proximal humerusfracture..No direct comparisons have been done of lockedplating with hemiarthroplastyin this group ofpatients.

.However, indirect comparisons reveal favorableresults for locked plating


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.Despite these moderate rates of osteonecrosis,functional results after locked plating of three andfour-part fractures compare favorably with results ofhemiarthroplasty


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.High-level-of-evidence studies and even lower-levelcomparative studies have yet to validate a clearadvantage of locked plating over conventionalmeans..However, early cohort series indicate consistent andgood results with this method.

.These findings combined with the relative technical

ease have rapidly elevated locked plating to astandard method of treatment for these fractures.


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Unstable proximal humerusfracture treated with a locking proximal humerusplate in a 70-year-old woman. A, Anteroposteriorinjury radiograph. B,Postoperative anteroposteriorradiograph C, Postoperative lateral radiograph.Note that all screw holes in the plate do not need to be filled


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Locked Plating of Fractures of theLower Extremity.Obtaining and maintaining end-segment fixation ischallenging in fractures of the lower extremityespecially in osteopenicpatients with comminutedfractures.

.Given the additional loads inherent to lower extremityfunction it is not surprising that locked plating hasessentially replaced conventional plating for theseinjuries.


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Femoral PeriprostheticFracture.High union rates have been achieved with acombination of minimally invasive submuscularplating and the use of locked plates for fixation ofperiprostheticfractures above total knee arthroplasty

and below total hip arthroplasty


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.Multiple case series have reported favorable resultsusing locked plates for periprostheticfractures above.The ability to obtain multiple points of fixation aroundthe lugs and cement mantle of a TKA improves distalfixation, which has led to higher union rates andlower rates of secondary surgery compared with

historical controls.


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.When treating periprostheticfractures below a THR,combination of screws and cerclagecables is typicallypreferred..Screws placed around a stem are typically unicortical;.Cables control bending and torsion to some extent,and the locked screws can control length.

.It is now possible to insert a unicorticallocked screwand a cable in the same plate hold using buttonsthat fit into the screw head.


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.This ability to optimize fixation by using a cable and alocked unicorticalscrew at the same level aroundstems may obviate the need for orthogonally placedallograft struts in many patients..However, such treatment should be individualizedbased on bone quality and construct stability.

.The longtermeffects of drilling and inserting screwsinto the cement mantle around a femoral component

are unknown


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Anteroposteriorradiograph of a periprostheticfemur fracture below awell-fixed femoral component treated with a locked plate in a 65-year-oldwoman.


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.Most studies have demonstrated excellent unionrates and an acceptably low complication rate mostnotably-Less fixation failure and varuscollapse

compared with previously used techniques


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.Problems encountered with first-generation lockedplates included-valgusmalalignmentof the distal fragment-plate malposition on the femoral shaft-proximal fixation failure resulting from unicortical

shaft fixation

-fracture site distraction.

.These complications have been minimized with moremodern implant designs and reduction instruments


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Proximal Tibia Fracture

.Locked plating is rapidly replacing traditional platingfor complex fractures of the proximal tibia and tibial

plateau

.High-energy unstable fractures, such as Schatzkertype V and VI fractures and some type IVfractures,appearto have benefited from lockedplating technology


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.Multiple series have demonstrated excellent unionrates..However infection is a concern with higher-gradeopen injuries, even following a period of soft-tissuerecovery.


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.The utility of locked plating in obtaining proximalfragment fixation has led some authors to use suchconstructs for extra-articularfractures that havehistorically been very difficult to nail..These short, extra-articularfractures often require

alternative nail starting points,largersurgicalapproaches, and the use of blocking screws, externalfixators, small plates, or other reduction aids.

.With the development of percutaneousinsertion andscrewtargetingaids, plating has become an attractivealternative to nailing


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.Insertion site knee pain is not a concern when platingthese fractures..When such fractures are plated,theplate is insertedwith the knee in full extension..This negates the pull of the quadriceps muscle andminimizes extension deformity of the proximal

fragment.The plate is applied laterally under fluoroscopiccontrol, making valgusdeformity very unlikely aslong as there is appropriate surgical vigilance


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.In all but the most osteopenicpatients, locked platinglikely offers little or no advantage when treatinglower-energy unicondylarfractures (ie, ShatzkertypeI, II, III, many type IV)..These fractures can be treated effectively withtraditional plates which reduces cost


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.Locked constructs probably offer little benefit infractures that are double-plated.


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Calcaneusand Foot Fracture.Locking plates are available for the management ofcalcaneusfractures..Theoretically, these plates provide better coronalplane stability of the tuberosity, and they mayprovide more robust support of the reconstructed

articularsurface..Although biomechanical data have demonstrated thesuperior stability of locked plates, no clinical data areavailable documenting superior outcomes comparedwith conventional plates.


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.The plates are thicker, and plate bulk laterally maycause difficulty with the tenuous soft tissues whichmay irritate the peronealtendons


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Summary.Locking implants for complex fractures haveundergone many innovations during the past decade,and their relative advantages and indications areincreasingly understood..The theoretic advantages of improved stability

offered by locked constructs and the biologicadvantages afforded by muscle-sparing insertionhave generally been borne out, with reported higherunion rates.


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.Malalignment, nonunion, implant failure and fracture,

and a steep learning curve still present challenges,

.But most recent series demonstrate lower

complications with greater surgeon experience andbetter instrumentation..Future constructs likely will improve subchondralsupports, improve the strengthof screw angulationand locking ability, and further facilitate fracture

reduction with specialized instruments.


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.In general, locked constructs should be reserved forfixation in osteoporotic patients and for problematic

fractures that have demonstrated high failure rateswith conventional platingmost notably, comminuted

metaphysealfractures.

.Early data on newer polyaxialdesigns and various

anatomically designed plates are encouraging, butfurther research is needed to define the role of these

new technologies.


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