Uni Knee for Perfection Phil Davidson MD Davidson Orthopedics Park City UT Dec 6 2018 No conflicts to report PSI Uni Knee Resurfacing Advantages Better Bone Fit Bone Preservation ID: 783351
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Patient Specific Implants - PSIUni Knee for Perfection
Phil Davidson, M.D.Davidson OrthopedicsPark City, UTDec 6 , 2018
Slide2No conflicts to report
Slide3PSI Uni Knee Resurfacing AdvantagesBetter Bone FitBone PreservationConvertability – Bridge in “younger” ptsImproved BiomechanicsProtect other compartmentsSimplicityBetter OutcomesPoor Alternatives for Lateral UniLower Cost
Slide4PSI Uni Knee Implants & JigsImplants and Jigs 3D printedMore accurate fit may increase longevityImproved Load bearingAccommodate morphologic variability, “odd sizes and shapes”
Slide5PSI Uni Knee Implants and Jigs Fit Better Patient-specific implants vs off-the-shelf implantsGreater cortical rim surface area coverage 77% v. 43% medially60% v. 37% laterally
Slide6Tibial Uni Component Sizing Does size matter? Implication of mismatchOverhang of tibial tray by >3mm occurred in 9% of Oxford UKR in series n=1605 yrs post op, this group had significantly worse Oxford Knee Scores (p=.0001) than those without overhangDon’t want to undersize tray either, risk subsidence Chau R, Gulati A, Pandit H, Beard DJ, Price AJ, Dodd CAF, Gill HS, Murray DW: Tibial component overhang following unicompartmental knee replacement - does it matter? Knee 2009, Vol. 16, pp. 310 - 313.
Slide7PSI Knee - Bone Preservation No subchondral bone resected from distal femurRelatively small proximal tibial resection vs. Mobile bearingEasier conversion to TKA for young pts
Slide8PSI Knee Biomechanics Precise match of femoral “J” anatomy replicates roll backMore natural feelEnhanced stability through ROMPreservation of “other” knee regions
Slide9Finite element analysis PSI vs Off Shelf UKABone coverage better, bone resection less for PSIMedial PSI improved mechanics in Lateral compartment
Slide10PSI Uni Knee Implants and Jigs - SIMPLERDigitize limb, including size and alignment PRE-OPMRI or CT Avoid intraop “fiddling”Avoid necessity for robotWhy not preserve subchondral bone????
Slide11Excellent Fit and Outcomes 31 patients with medial OAMean age 60 years. Minimum follow-up 17 months. One aseptic loosening needed exchange; one acute late-onset infectionNo further revisions/reoperations or complications. X-rays showed an ideal fit of the implant with less than 2 mm subsidence or overhang in all cases. VAS changed from 6.51 preoperatively to 1.11 postoperatively.KSS improved from 111.23 preop to 180.61 postopFunctional KSS improved from mean 60.39 to 94.51.
Slide12Excellent Fit and AlignmentAccuracy of Implant Match: Mean: 0mm AP, 1mm Med-LatSlope maintained5 degree pre op slope unchangedWB Fem-Tib alignment correctedMean preop 7 degrees varusMean postop 1 degree varus
Slide13Patient Specific Jigs and Implants ONLY good Lateral Side Option
Slide14Tibial fit was much better in patient specific vs legacy implants1.0 mm mismatch vs 3.3mm mismatch p<.01Survivorship at mean 36 mos 97% vs 85%
Slide15PSI OnlayResurfacing
Slide16Residual cartilage subjacent to implant removed
Slide17Holes for implant pegs and cement interdigitation
Slide18Slide19Slide20Mobile Bearing… really????DisadvantagesHuge bone resectionSuboptimal fitNon anatomicAdvantagesNHS formulary35+ year historyVCR, pagers, cassettes
Slide21Robot- an expensive marketing tool???…..Robot costs >1M $Newer handhelds are expensive tooImplants are off the shelfMarked intraop complexityA “work-around” for PSI Jig and Implant IP
Slide22Patient Specific Jigs and Implants are the only way to go….SimplerFasterMore AccurateLess CostBetter BiomechanicsSEEMINGLY BETTER
Slide23Thank You phildavidsonmd@gmail.comdavidsonorthopedics.com