OS ET 2017 Bellagio Las Vegas Evolving Technique Update Cup positioning to avoid Metalosis Bone preparation to avoid Failure of Ingrowth Thomas Gross 8:52 AM 33
#1 Preventing Metalosis in Hip Resurfacing using RAIL guidelines and NS IOR
Cause of Metalosis in HRA Poor cup posit ion S teep inclination and excessive anteversion Poor implant design DePuy AS R S maller S izes women Edge loading, loss of fluid film
R elative A cetabular I nclination L imit 2013 S afe zone t o prevent met alosis S maller bearing sizes need more horizont al posit ion Based on 777 cases wit h ions and st anding pelvis XR 99% confidence “A Safe Zone for Acetabular Component Position in Metal-On- Metal Hip Resurfacing Arthroplasty” Fei Liu PhD, Thomas P. Gross MD JOA 2013
RAIL chart for Biomet Magnum* *also for Corin, BHR, ICON
Principle we have learned: S hallower components must be placed more horizontal to avoid edge loading and AWF Deep cup S hallow cup 60mm/ 165 0 40mm/ cup154 0 Too vert ical horizontal
Caveats: RAIL is based on standing AIA MUS T be measured on st anding pelvis XR Ant eversion must be set + 10 0 wrt TAL IF TAL is not present , AV must be j udged qualit at ively on NS IOR
Dynamic pelvic tilt (5-10% ) S upine S tanding AIA=40 AIA =31 More anteverted!
How do you meet RAIL guidelines? NS IOR Preoperat ive st anding pelvis XR Digit al port able XR machine Implant acet abular component Use TAL as guide for AV Est imat e AIA t o meet RAIL
S himadzu Ra Dt wireless digital plate
Right hip rotated forward toward XR tube rotate OR table away from XR tube Preop standing Initial intraop
Posterior tilt too low tilt XR tube cephalad 2 nd intraop preop
Obturators match preop standing in width and height IOR measure “ standing” AIA achieved NS Preop standing Intraop “ standing” Third intraop film
RAIL achieved 46 mm bearing < 40 0 Intraop “ standing” AIA= 33 Postop standing AIA= 33
Now Validation of RAIL in a separate patient series 0% 1803 consecut ive cases 2010-2015 RAIL achieved in 100% cases Ions opt imal in 98.8%
#2 Bone preparation to avoid Failure of Ingrowth The Wedge Fit Acetabular Technique (developed in June 2012)
Failure of Ingrowth in HRA limited options for supplemental fixation S egmental defects solved with Trispike Others 0.7 % before 2 years Our hypothesis: Inadvertent apex contact
Magnum / recap Trispike (available 2007) Use with 30% wall deficiency
Cup fixation varies with standard preparation Apex Wedge Fit Contact Apex Edge “Loose” “Loose” Less contact pressure Cup wobbles Cup seats with weight in with bearing weight bearing
Failure of Acetabular ingrowth (without defect) DG 56 yo man nl bone initial postop XR
Failure of Acetabular ingrowth (without defect) Fit military man running regularly. S udden worsening 2 Presents with 2 months months later pain 22 months postop
Question ? If we could prepare the acetabulum so that every patient had a guarant eed wedge – fit, could we eliminate failure of ingrowth? We would want to take into account bone density S egmental defects are already treated by trispike
Comparison of bone preparation (only failures before 2 years are considered) Group I: 11/ 2004 through 5/ 2012 All Magnum cups (n=2414) All cases under reamed by 1 mm Group II: 6/ 2012 through 9/ 2015 All magnum cups (n=868) Wedge fit technique
Wedge fit Technique Line to line ream in good bone (T score > -1.0) I mm under ream in poor bone (T score < -1.0) Ream 1-2mm apex bone with small reamer Aft er init ial reaming, smaller reamer used at apex
Endpoints (before 2 years) Failure of ingrowt h Init ial (asympt omat ic) cup shift s (before 6 weeks) Unexplained pain Excluded: AWRF blood ions great er t han 10 ug/ L dysplasia before 2008
Results Group I Group II p n=2414 n=868 Failure of Ingrowth 0.7 % 0 0.02 Cup shift 0.7 % 0.1 % 0.04 Unexplained 3.8% 0.8% 0.004 pain
Interpretation 1. S upplemental Fixation is required when there is a 30% segmental wall defect after preparation Gaillard & Gross BMC 2016 no failure ingrowth in 242 dysplasia cases
Interpretation 2. Wedge Fit preparation eliminates the remaining failures of bone ingrowth 100% reduction (since 6/ 2012) Component wedges in with weight bearing achieving a progressively tighter fit and loading the peripheral porous coating promoting bone ingrowth Inadvertent cases of primary apex contact and subsequent toggling micromotion are avoided
Interpretation 3. Early asymptomatic cup shifts are also reduced by more secure initial wedge fit 0.1% 0.8% (90% reduction) previously unrecognized phenomenon x-ray techniques not standardized subj ect of another publication
Interpretation 4. Reduction of unexplained pain (HHS < 70) ------ 0.8% 3.8% (80% reduction) (NOT 20-30% as in THA and TKA) suggests many cases of unexplained pain in HRA may be due to fibrous ingrowth caused by inadequate initial fixation
Other causes of unexplained pain LBP Metalosis Infection Degenerative abductor tears Psoas cup edge impingement Nonspecific tendonitis Neck on cup impingement S econdary gain (work comp, liability) Excessive patient expectations (Minimal arthritis) Pain syndromes (multiple allergies, high anxiety or depression score)
Wedge Fit Acetabular preparation Eliminat es revisions for ingrowt h failure 100% Reduces init ial asympt omat ic cup shift s 90% Reduces unexplained pain 80% all st at ist ically significant
Wedge Fit Technique Line to line ream in good bone (T score > -1.0) I mm under ream in poor bone (T score < -1.0) Ream 1-2mm apex bone with small reamer Aft er init ial reaming, smaller reamer used at apex
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