Computer-assisted Treatment of Distal Radius Malunion€¦ · Distal Radius Malunion Author: Prof....
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32 ORTHOPRENEUR • September/October 2010 FUTURETECH Computer-assisted Treatment of Distal Radius Malunion Author: Prof. Filip Stockmans, M.D., Ph.D. Intra-articular malunions represent an exceptional technical challenge for the treating surgeon. Multidetector CT scans (MDCT) with three-di- mensional (3D) surface rendered images are increasingly used not only for the evaluation of malunions, but also to develop a road map for sur- gery in patients who have been selected for corrective osteotomy. 1,10,12 CT- based virtual pre-operative planning, including virtual osteotomy, predic- tion of final positioning 11 and additive manufacturing of patient-specific instruments based on the 3D bone structure are clinical reality. 8,9 Computer-assisted Planning The 3D information present in the data set of a CT scan can be used for computer-assisted planning. The MDCT scans consist of a series of sequential slices with preset thickness and slice intervals. With the multi- detector helicoidal CT scans, resolution of up to 0.3 mm can be achieved, though at the “cost” of a higher radiation dose. 8 From the CT dataset, 3D images can be reconstructed with two distinctly different techniques. The most commonly used technique is surface rendering, 11,13 which re- constructs the bone soft tissue interface presented as a 3D surface that can be viewed from all angles. On the other hand, the segmentation tech- nique identifies the bony structure in each slice (surface x height equal to slice thickness) which is restacked in an orderly manner, resulting in mathematically described volume, 8,9 with distinct mathematical sizes and shapes that can be manipulated as a geometric structure (sliced, repositioned, measured, etc.) into new configurations. Mimics software (Materialise NV, Leuven, Belgium) was used for segmentation and vir- tual planning. When dealing with a distal radius malunion, the first step is to seg- ment the radius and make a virtual 3D reconstruction. (See Exhibit 1.) Next, the different parts of the malunion are isolated as individual struc- tures. (See Exhibit 2.) Treatment of an intra-articular malunion usually involves recreating the original fracture pattern with a series of 1mm drill holes. (See Exhibit 3.) In cases where length needs to be reconstruct- ed, it is preferable to use the mirror image of the contralateral non-af- fected radius as a reference. (See Exhibit 4.) Once the virtual reduction is performed (See Exhibit 5.), a digital image of the implant (typically plate and screws) can be imported into the project. This step allows optimiza- tion of the osteotomy site and implant choice. The implant can also be used as an assembly guide for the recon- struction. In these cases, the drill holes for the fixation of the implant have to be predrilled on the malunited radius. (See Exhibit 6.) The loca- Exhibit 1: Virtual 3D reconstruction of distal radius Exhibit 2: Parts of radius malunion are isolated Exhibit 3: Recreating the original fracture pattern of an intra-articular radius malunion
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Transcript of Computer-assisted Treatment of Distal Radius Malunion€¦ · Distal Radius Malunion Author: Prof....
32 ORTHOPRENEUR • September/October 2010
FUTURETECH
Computer-assisted Treatment of Distal Radius Malunion
Author: Prof. Filip Stockmans, M.D., Ph.D.
Intra-articular malunions represent an exceptional technical challengeforthetreatingsurgeon.MultidetectorCTscans(MDCT)withthree-di-mensional(3D)surfacerenderedimagesareincreasinglyusednotonlyfortheevaluationofmalunions,butalsotodeveloparoadmapforsur-geryinpatientswhohavebeenselectedforcorrectiveosteotomy.1,10,12
CT-basedvirtualpre-operativeplanning,includingvirtualosteotomy,predic-tionoffinalpositioning11andadditivemanufacturingofpatient-specificinstrumentsbasedonthe3Dbonestructureareclinicalreality.8,9
Computer-assisted PlanningThe3DinformationpresentinthedatasetofaCTscancanbeused
forcomputer-assistedplanning.TheMDCTscansconsistofaseriesofsequentialsliceswithpresetthicknessandsliceintervals.Withthemulti-detectorhelicoidalCTscans,resolutionofupto0.3mmcanbeachieved,thoughat the“cost”ofahigherradiationdose.8FromtheCTdataset,3Dimagescanbereconstructedwithtwodistinctlydifferenttechniques.Themostcommonlyusedtechniqueissurfacerendering,11,13whichre-constructsthebonesofttissueinterfacepresentedasa3Dsurfacethatcanbeviewedfromallangles.Ontheotherhand,thesegmentationtech-niqueidentifiesthebonystructureineachslice(surfacexheightequaltoslicethickness)whichisrestackedinanorderlymanner,resultinginmathematically described volume,8,9 with distinct mathematical sizesand shapes that can be manipulated as a geometric structure (sliced,repositioned,measured,etc.)intonewconfigurations.Mimicssoftware(MaterialiseNV,Leuven,Belgium)wasusedforsegmentationandvir-tualplanning.
Whendealingwithadistalradiusmalunion,thefirststepistoseg-menttheradiusandmakeavirtual3Dreconstruction.(SeeExhibit1.)Next,thedifferentpartsofthemalunionareisolatedasindividualstruc-tures.(SeeExhibit2.)Treatmentofanintra-articularmalunionusuallyinvolves recreating the original fracture pattern with a series of 1mmdrillholes.(SeeExhibit3.)Incaseswherelengthneedstobereconstruct-ed, it ispreferabletousethemirror imageof thecontralateralnon-af-fectedradiusasareference.(SeeExhibit4.)Oncethevirtualreductionisperformed(SeeExhibit5.),adigitalimageoftheimplant(typicallyplateandscrews)canbeimportedintotheproject.Thisstepallowsoptimiza-tionoftheosteotomysiteandimplantchoice.
The implantcanalsobeusedasanassemblyguide for therecon-struction. In these cases, thedrillholes for thefixationof the implanthavetobepredrilledonthemalunitedradius.(SeeExhibit6.)Theloca-
Exhibit 1: Virtual 3D reconstruction of distal radius
Exhibit 2: Parts of radius malunion are isolated
Exhibit 3: Recreating the original fracture pattern of an intra-articular radius malunion
September/October 2010 • ORTHOPRENEUR 33
tionofthedrillholesonthemalunitedboneisdeterminedbyfittingtheimplanttothevirtualreconstructionandsubsequentlyreverseengineer-ingthedrillholepositionsinthemalunitedposition.
Executing the Surgery Using Patient-specific InstrumentsSince the goal of these procedures is to reconstruct the anatomy
with(sub)millimeterprecision,5it’sdifficulttorelyonclinicaljudgmentand fluoroscopy only. Various solutions have been suggested rangingfromarthrotomy,10arthroscopywithinsideoutosteotomy,3experimen-talnavigation6andpatient-specificinstrumentsproducedusingadditivemanufacturing.8,9
Thesepatient-specificSurgiCase®surgicalguides(MaterialiseNV)areproducedassurfacemoldsofthe3Dbonemodelandhaveauniquefittothebone.Additionally,theseguidesaredesignedwithK-wireholesforfixationtothebone,cylindersthatarefittedwithdrillsleeves,andslitstoperformosteotomiesalongdefinedcuttingplanesasdeterminedinthepre-surgicalplan.
Note:whenconfrontedwithcombinedintra-andextra-articularmal-unions,theprocedurerequirestheuseofmultipleconsecutiveguides.Inthesecases,theintra-articularosteotomyisperformedfirstbydrillingaseriesof1.1mmdrillholesalongtheoriginalfracturelinethatstructur-allyweakens theboneand facilitates recreating the fracturealong thepreset pattern. (See Exhibit 7.) Second, the drill holes for the implantfixationaremade.Usually,themetaphysicalosteotomyisthelaststep.
Atthispointallpartsareseparated.Drilling(perforating)thebonestructurallyweakensittotheextentthatitwillbreakalongthepresentpattern. (SeeExhibit8.)Sincethedrillholesforthefixationof the im-plantarepre-drilledinthepositionofthefullyreducedmalunion,theimplantisusedasafinalreductiontemplate.(SeeExhibit9.)
ConclusionThistechnologywasfirstusedinourdepartmentin2005,initially
forthesurgicalplanningofaMadelung’sdeformitywithouttheuseofpatient-specific instruments. Patient-specific instrumentation was thenintroducedin2007withourfirstintra-articularmalunionoftheradius.Sincethen,fivetotencasesofvaryingnatureshavebeenperformedev-eryyearutilizingtheengineeringservicesprovidedbyMaterialise.Fur-ther,thistechnologyhasbeenusedfortreatmentsofmalunionsoftheproximalradius,distalhumerus,distalfemur,proximaltibia,etc.
Asreportedpreviously,thepre-surgicalplanningaloneofcomplexosteotomies in 3D offers multiple advantages. The surgeon not onlygainsmore insight in thecomplexityof thedeformity,buthecanalsofine-tune the surgery and evaluate different, sometimes conflicting,treatmentstrategiessuggestedinliterature.4Thedifferenttrialsaredoneinavirtualsystematnoadditionalcost,incontrasttotrialsurgeryonphysicalmodelsthatasarulecanonlybeperformedonce.
FUTURETECHExhibit 4: Using Mimics to create a mirror image of the contralateral non-affected radius as a reference for reduction
Exhibit 5: Virtual reduction of segments
Exhibit 6: Determining the drill holes for plate fixation
Exhibit 7: Intra-operative use of Materialise’s SurgiCase guide
The different trials are done in a virtual system at no additional cost, in contrast to trial surgery on physical
models that as a rule can only be performed once.
34 ORTHOPRENEUR • September/October 2010
Soonafterthepossibilitiesofvirtualsurgeryplanningwerereported,surgeonstriedtobringplanningintotheoperatingtheater.Onepossibilityistouploadtheprojectintonavigationsoftware.Theproblemintheupperextremity,however,istheuseoftrackingmarkersontheupperextremityand instruments due to size limiting factors. The first attempts to bringthesurgeryintotheoperatingtheaterproducedspacingblockstoexactlymatch thevoidspaceafteropeningwedgeosteotomies.11Ofcourse, thiswasofnouseinclosingwedgeorintra-articularosteotomies.
Along came the next technological advancement for surgery plan-ningviathedevelopmentofpatient-specificinstruments,suchassurgicalguides.Thistechnologyhasbeenusedformanyyearsindental implan-tology14,15andmorerecently,wasintroducedtokneearthroplasty.7Thesepatient-specificinstrumentsserveasanintra-operativenavigationtooltoperformsurgical functionswithhighprecision; thegreencolor indicates<1mmaccuracy.(SeeFigures9.1,9.2and9.3inExhibit9.)Theaccuracyfa-cilitatesauniquefittingofthepatient-specificinstrumentontothesurfaceoftheaffectedbone.Themoreirregularitiescanbeincludedinthemoldedsurface,themorereliablethefit.
Withtheintroductionofpatient-specificinstrumentstotheorthopae-dicfield,itbecamepossibletoperformintra-andextra-articularosteoto-mieswithahighdegreeofprecision9aspre-surgicallyplannedforthein-dividualpatient.Furtherintroducingthefixationdeviceintotheplanningprocessallowsassembling thedifferent fragmentsusing thefixation im-plantasadistractiontemplate.Althoughconventionalsurgicalskillsandpre-operativefluoroscopyaresufficientinmanycases,themorecomplexcaseslikecombinedintra-andextra-articularosteotomieswithlengthre-constructionorrotationalmalunion,mostcertainlyarefacilitatedwiththeuseofthefixationdeviceasanassemblytemplate.
REFERENCES
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3. delPinalF,Garcia-Bernal,FJ,DelgadoJ,SanmartinM,RegaladoJandCerezalL.“Cor-rectionofmalunitedintra-articulardistalradiusfractureswithaninside-outosteotomytechnique,”J Hand Surg Am31(6):1029-34,2006.
4. JupiterJB,RuderJandRothDA.“Computer-generatedbonemodelsintheplanningofosteotomyofmultidirectionaldistalradiusmalunions,” J Hand Surg Am17(3):406-15,1992.
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FUTURETECHExhibit 8: Recreating the original fracture after the bone has been weakened
Exhibit 9: Plate fixation
Figure 9.1:
Figure 9.2:
Figure 9.3:
With the introduction of patient-specific instruments to the orthopaedic field, it became possible to perform intra- and extra-articular osteotomies with a high degree of precision9
as pre-surgically planned for the individual patient.
September/October 2010 • ORTHOPRENEUR 35
7. Lombardi AV Jr, Berend KR and Adams JB. “Patient-specific ap-proachintotalkneearthroplasty,”Orthopedics31(9):927-30,2008.
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9. OkaK,MoritomoH,GotoA,SugamotoK,YoshikawaHandMu-raseT.“Correctiveosteotomyformalunitedintra-articularfractureof thedistal radiususingacustom-madesurgicalguidebasedonthree-dimensional computer simulation: case report,” J Hand Surg Am 33(6):835-40,2008.
10. PrommersbergerKJ,RingD,delPinoJG,CapomassiM,SlullitelMandJupiterJB.“Correctiveosteotomyfor intra-articularmalunionofthedistalpartoftheradius.Surgicaltechnique,”J Bone Joint Surg Am88Suppl1Pt2:202-11,2006.
11. RiegerM,GablM,GruberH,JaschkeWRandMallouhiA.“CTvir-tualreality inthepreoperativeworkupofmaluniteddistalradiusfractures:preliminaryresults,”Eur Radiol 15(4):792-7,2005.
12. Ring D, Prommersberger KJ, Gonzalez del Pino J, Capomassi M,Slullitel M and Jupiter JB. “Corrective osteotomy for intra-articu-larmalunionofthedistalpartoftheradius,”J Bone Joint Surg Am87(7):1503-9,2005.
13. Vannie,MW,TottyWG,StevensWG,WeeksPM,DyeDM,Daum WJ,GilulaLA,MurphyWAandKnappRH.“Musculoskeletalap-
plications of three-dimensional surface reconstructions,” Orthop Clin North Am16(3):543-55,1985.
14. Verstreken K, Van Cleynenbreugel J, Martens K, Marchal G, vanSteenbergheDandSuetensP.“Animage-guidedplanningsystemfor endosseous oral implants,” IEEE Trans Med Imaging 17(5):842-52,1998.
15. VrielinckL,PolitisC,SchepersS,PauwelsMandNaertI.“Image-based planning and clinical validation of zygoma and pterygoidimplantplacementinpatientswithsevereboneatrophyusingcus-tomizeddrillguides.“Preliminaryresultsfromaprospectiveclini-calfollow-upstudy,”Int J Oral Maxillofac Surg 32(1):7-14,2003.
Professor Filip Stockmans, M.D. is a professor at Katholieke Universiteit, Campus Kortrijk Belgium. Trained in Hand & Microsurgery at the Kleinert Institute in Louisville, Kentucky and University of Umea in Sweden, Dr. Stockmans has been in private practice for over 20 years. For clinical follow up, please contact Dr. Stockmans at [email protected]. For technology follow up, please contact Bill McIlhargey at [email protected].
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