J.R. Rudzki, MDJ.R. Rudzki, MDClinical Assistant ProfessorClinical Assistant ProfessorThe George Washington University School of MedicineThe George Washington University School of Medicine

Arthrex Knee MeetingArthrex Knee MeetingLos Angeles, CALos Angeles, CA

May 12, 2012May 12, 2012

Medial Opening WedgeMedial Opening WedgeHigh Tibial OsteotomyHigh Tibial Osteotomy

DisclosureDisclosure

Previous direct & indirect funding & support for Previous direct & indirect funding & support for research & education from:research & education from:

• Philips Medical ImagingPhilips Medical Imaging• Bristol-Myers-SquibBristol-Myers-Squib• Smith & NephewSmith & Nephew• NIH (CT Chen)NIH (CT Chen)• HSS Institute for Sports Medicine ResearchHSS Institute for Sports Medicine Research• Major League BaseballMajor League Baseball

Arthrex – ConsultantArthrex – ConsultantAJSM, JBJS, CORR – ReviewerAJSM, JBJS, CORR – ReviewerAAOS – Evaluation Committee, BOCAAOS – Evaluation Committee, BOCAccelerated Rehab Technologies – Board Accelerated Rehab Technologies – Board

INDICATIONSINDICATIONS

• Varus alignment with Varus alignment with medial compartment medial compartment arthrosisarthrosis

• Knee instability Knee instability

• Medial compartment Medial compartment overload following overload following meniscectomymeniscectomy

• Osteochondral defects Osteochondral defects requiring resurfacing requiring resurfacing proceduresprocedures

Sagital Plane StabilitySagital Plane StabilityPrimary Anteroposterior StabilizersPrimary Anteroposterior Stabilizers

ACLACL• Deficiency Deficiency →→ posteromedial posteromedial

tibial-sided wear (“tibial-sided wear (“cupulacupula””) ) • Deficiency Deficiency →→ ↑↑ risk of medial risk of medial

meniscal tear, need for meniscal tear, need for meniscectomy, worsening varus meniscectomy, worsening varus (viscious cycle)(viscious cycle)

• Intact Intact →→ more typical more typical anteromedial wear patternanteromedial wear pattern

PCL PCL • Deficiency Deficiency →→ patellofemoral, patellofemoral,

medial sided wearmedial sided wear

ROLE OF SLOPEROLE OF SLOPERADIOGRAPHIC DATARADIOGRAPHIC DATA

Bonnin, 1990Bonnin, 1990• Every 10Every 10°° increase in posterior tibial slope increase in posterior tibial slope →→ 6mm increase in 6mm increase in

anterior tibial translation (ATT)anterior tibial translation (ATT) DeJour, 2000DeJour, 2000

• Direct linear relationship between slope and ATTDirect linear relationship between slope and ATT• Hypothesis: Reduce posterior slope Hypothesis: Reduce posterior slope →→ reduce AP instability, reduce AP instability,

improve symptomsimprove symptoms Hohmann, 2006; Cullu 2005Hohmann, 2006; Cullu 2005

• Lateral closing wedge, Dome HTO Lateral closing wedge, Dome HTO →→ ↓ ↓ posterior tibial slope posterior tibial slope Marti , 2004; Sterett, 2009Marti , 2004; Sterett, 2009

• Medial opening HTO inadvertently Medial opening HTO inadvertently →→ ↑↑ posterior tibial slope posterior tibial slope• But no relation to outcomes/Lysholm scores (Sterett)But no relation to outcomes/Lysholm scores (Sterett)

• Sectioning the PCL caused posterior sagSectioning the PCL caused posterior sag• AOWO AOWO →→ increase in tibial slope increase in tibial slope →→ significantly significantly

reduced sag/translation throughout ROMreduced sag/translation throughout ROM• Hypothesis: AOWO may improve articular Hypothesis: AOWO may improve articular

contact forces in PCL deficient kneescontact forces in PCL deficient knees

Effect of OsteotomyEffect of Osteotomy

increasing slope causes an anterior shift in tibial resting position

accentuated under axial loads

Role of Slope

Effect of OsteotomyEffect of Osteotomy

7 fresh human cadaver knees7 fresh human cadaver knees

AOWO +/- ACL/PCL sectioningAOWO +/- ACL/PCL sectioning•Cartilage pressures, kinematicsCartilage pressures, kinematics•AOWO AOWO →→ ↑↑ATT, decompression of posterior half of ATT, decompression of posterior half of plateauplateau•Hypothesis: 3D valgus/flexion osteotomy beneficial to Hypothesis: 3D valgus/flexion osteotomy beneficial to knees s/p post horn meniscectomy, PCL/PL unstable knees s/p post horn meniscectomy, PCL/PL unstable knee w/ PM joint wear, varus thrustknee w/ PM joint wear, varus thrust

Role of Slope

Effect of OsteotomyEffect of Osteotomy

9 fresh human cadaver knees9 fresh human cadaver knees

AMOWO vs. PMOWO +/- ACL sectioningAMOWO vs. PMOWO +/- ACL sectioning•Increasing tibial slope in ACL deficient knees Increasing tibial slope in ACL deficient knees redistributes pressures posteriorlyredistributes pressures posteriorly•Recommendation: posterior plate placement for Recommendation: posterior plate placement for ACL deficient kneesACL deficient knees

Effect of OsteotomyEffect of Osteotomy

• Noyes et al. AJSM 2005Noyes et al. AJSM 2005• 3 dimensional geometric analysis 3 dimensional geometric analysis • Gap angle at tubercle should be half Gap angle at tubercle should be half

posterior cortex to maintain slopeposterior cortex to maintain slope• Error of 1mm created 2 degree changeError of 1mm created 2 degree change

• Intraoperative Assessment Intraoperative Assessment used to confirm used to confirm Preoperative Preoperative PlanningPlanning

• Preoperative planning Preoperative planning guide guide intraoperative wedge thicknessintraoperative wedge thickness

• Intraoperative confirmation Intraoperative confirmation based on reliable assessment based on reliable assessment of:of:• Anatomic AxisAnatomic Axis• Mechanical AxisMechanical Axis• Weight-bearing LineWeight-bearing Line

Osteotomy Planning & AssessmentOsteotomy Planning & Assessment

Important AxesImportant Axes• Mech Axis (a):Mech Axis (a):

• center of knee center of knee center of hip center of hip• 0-2.20-2.2° valgus° valgus

• Anat Axis (b):Anat Axis (b): • center of fem shaft center of fem shaft center of tibial shaftcenter of tibial shaft• 5-75-7° valgus° valgus

• WBL: WBL: • center of hip center of hip center of ankle center of ankle• Congruent with MA if passes through center of the Congruent with MA if passes through center of the

kneeknee• Physiologic is slightly medial to center of knee Physiologic is slightly medial to center of knee • 62.5% of the tibial plateau width62.5% of the tibial plateau width

DonDon’t forget the sagittal plane…’t forget the sagittal plane…

Slope:Slope:• Longitudinal tibial axis and line Longitudinal tibial axis and line

parallel to medial plateau joint parallel to medial plateau joint surfacesurface

• Varies from 0-10Varies from 0-10° ° posterior slopeposterior slope• Affected by AP plate position with Affected by AP plate position with

HTOHTO• Useful with ACL/PCL deficiencyUseful with ACL/PCL deficiency

KeypointsKeypoints

• Preoperative and intraoperative Preoperative and intraoperative correction based on total varus correction based on total varus angulationangulation

• Native tibiofemoral varus alignmentNative tibiofemoral varus alignment• Medial joint space degenerationMedial joint space degeneration• Lateral capsuloligamentous laxityLateral capsuloligamentous laxity

–Must consider to avoid over-correctionMust consider to avoid over-correction

–Evaluate contralateral normal sideEvaluate contralateral normal side

Avoiding overcorrection…Avoiding overcorrection…

• Rosenberg (WB Bilateral in 45° flexion)Rosenberg (WB Bilateral in 45° flexion)

• Measure Measure ΔΔ in lateral joint separation in lateral joint separation

• Overcorrection angle Overcorrection angle

• = 76.4 x [(Δ lat joint)/total plateau width]= 76.4 x [(Δ lat joint)/total plateau width]

• Defines extent of varus due to Defines extent of varus due to slack lateral restraintsslack lateral restraints

• per mm separation ~ 1 deg of per mm separation ~ 1 deg of angular deformity on WB filmangular deformity on WB film

• Subtract from correction Subtract from correction suggested by WB filmsuggested by WB film

What is the goal correction?What is the goal correction?• Coventry Coventry 8 8° of anatomic valgus° of anatomic valgus

• Hernigou Hernigou 3-6° valgus mechanical axis 3-6° valgus mechanical axis

• Dugdale Dugdale WBL 62-66% of tibial plateau width through the WBL 62-66% of tibial plateau width through the lateral compartmentlateral compartment

• Fujisawa Fujisawa 30-40% width lateral to center of knee 30-40% width lateral to center of knee

• Miniaci Miniaci 60-70% width of tibial plateau in lateral compartment 60-70% width of tibial plateau in lateral compartment

iBalanceiBalance HTO System HTO System

FDA Approved & CE MarkedFDA Approved & CE MarkedAnatomically SizedAnatomically Sized

• Profile flush with boneProfile flush with bone

• Built in corrective anglesBuilt in corrective angles

iBalanceiBalance HTO System HTO SystemAnatomically SizedAnatomically Sized

• Profile flush with boneProfile flush with bone• Built in corrective anglesBuilt in corrective angles

StabilityStability• PEEK implant shaped to PEEK implant shaped to

distribute loading with distribute loading with KeyholesKeyholes

• Designed to improve Designed to improve progressive weight bearingprogressive weight bearing

iBalanceiBalance HTO System HTO System Anatomically SizedAnatomically Sized• Profile flush with boneProfile flush with bone• Built in corrective anglesBuilt in corrective angles

StabilityStability• PEEK implant shaped to distribute loading with PEEK implant shaped to distribute loading with

KeyholesKeyholes• Designed to improve progressive weight bearingDesigned to improve progressive weight bearing

Bone GrowthBone Growth• PEEK material closely matches PEEK material closely matches

modulus of bonemodulus of bone

• Allows micro strain transfer to Allows micro strain transfer to stimulate new bone growthstimulate new bone growth

iBalanceiBalance HTO System HTO System

• Instrumented Instrumented SystemSystem

• Provides highest level Provides highest level of cut accuracyof cut accuracy

• Built in retractors Built in retractors create a cutting create a cutting “envelope” to “envelope” to significantly reduce N/V significantly reduce N/V complications and complications and lateral cortex fractureslateral cortex fractures• After learning After learning

system, average OR system, average OR time was 1 hourtime was 1 hour

iBalanceiBalance HTO System HTO System

iBalanceiBalance HTO System HTO System

iBalanceiBalance HTO System HTO System

Biplanar Alignment Guide facilitates precise placement of cutting guides

Align Fluoro with hinge-pin hole for a Perfect Circle

iBalanceiBalance HTO System HTO System

iBalanceiBalance HTO System HTO System

ContourLock HTO Plate SystemContourLock HTO Plate System

• Anatomically pre-contouredAnatomically pre-contoured• Distal and proximal bendsDistal and proximal bends

• Lower Profile!Lower Profile!• New low profile New low profile

bushings=thin plate designbushings=thin plate design• Provides strong locking Provides strong locking

constructconstruct• Polyaxial screw motionPolyaxial screw motion

• Simplified Screw Insertion-No Simplified Screw Insertion-No locking guide sleeve locking guide sleeve

required!required!• Straight, A/P sloped and flat Straight, A/P sloped and flat

plate options in RT and LT plate options in RT and LT sidessides

Assessing the CorrectionAssessing the Correction

• Determine WBL intraoperativelyDetermine WBL intraoperatively• Radiolucent tableRadiolucent table• EKG lead marks fem head center EKG lead marks fem head center • Bovie cordBovie cord

• Must apply axial load with Must apply axial load with measurementmeasurement

How good is the bovie cord?How good is the bovie cord?

Sabharwal & Zhao, JBJS 2008Sabharwal & Zhao, JBJS 2008•102 limbs in 80 patients102 limbs in 80 patients

•Full-length WB XR vs. intraoperative cord; Full-length WB XR vs. intraoperative cord; r=0.88r=0.88

•13.4-mm MA deviation13.4-mm MA deviation•2.8° difference in joint convergence angle2.8° difference in joint convergence angle

•BEST for:BEST for:• Normal BMINormal BMI• <2-cm deviation of the mechanical axis<2-cm deviation of the mechanical axis• <3° joint convergence angle<3° joint convergence angle

J.R. Rudzki, MDJ.R. Rudzki, MDClinical Assistant ProfessorClinical Assistant ProfessorThe George Washington University School of MedicineThe George Washington University School of Medicine

Arthrex Knee MeetingArthrex Knee MeetingLos Angeles, CALos Angeles, CA

May 12, 2012May 12, 2012

Medial Opening WedgeMedial Opening WedgeHigh Tibial OsteotomyHigh Tibial Osteotomy

Thank You

Other OptionsOther Options

Radiolucent alignment grid Under mattress on table Less vulnerable to body habitus No parallax and kinking of cord

Drop rod Prep hip -> ankle Full size fluoro machine

Computer navigation

Techniques (Miniaci)Techniques (Miniaci)

WBL

“Hinge” point at osteotomy site

Define arc of correction to center oftibiotalar joint

Defines correction angle for openingor closing wedge procedure

Techniques (Dugdale)Techniques (Dugdale)

Angle betweenMA to the desiredcorrection point onplateau

Cut film at desiredosteotomy site andshift until WBL is corrected

Techniques (Coventry)Techniques (Coventry)

Calculate difference between thepreoperative anatomic axis and theplanned anatomic axis

The common theme…The common theme…

• How do I translate How do I translate correction angle to correction angle to

useful intraoperative useful intraoperative measures?measures?

• Wedge SizeWedge Size• Varies with level of Varies with level of

osteotomyosteotomy

• TTW (true tibial width)TTW (true tibial width)

• Ø correction angleØ correction angle

• = TTW x (tan = TTW x (tan Ø)Ø)

• can be readily can be readily measured in the ORmeasured in the OR

ConclusionsConclusions

•Preoperative planning is the Preoperative planning is the MOST IMPORTANTMOST IMPORTANT

•Wedge geometry for HTO is Wedge geometry for HTO is complex – complex – must adjust for both must adjust for both coronal and sagittal planescoronal and sagittal planes

•Intraoperative tools are Intraoperative tools are limitedlimited

• Bovie cord OK for thin people with moderate correction Bovie cord OK for thin people with moderate correction as a confirmatory tool as a confirmatory tool

• Intraoperative grids or computer navigation Intraoperative grids or computer navigation may prove to be much better tools... may prove to be much better tools...

How good is the bovie How good is the bovie cord?cord?

• Sabharwal & Zhao, Sabharwal & Zhao, JBJS 2008JBJS 2008

• 102 limbs in 80 102 limbs in 80 patientspatients

• Full-length WB XR Full-length WB XR vs. intraoperative vs. intraoperative

cordcord• 13.4-mm MA 13.4-mm MA

deviationdeviation

• 2.82.8° difference in joint ° difference in joint convergence angleconvergence angle

• BEST for:BEST for:• Normal BMINormal BMI

• <2-cm deviation of the <2-cm deviation of the mechanical axismechanical axis

• <3° joint convergence <3° joint convergence angleangle

Ideal intraoperative assessment of alignment Ideal intraoperative assessment of alignment has not been found…has not been found…

Paley and Herzenberg et al

51 cm radiolucent alignment grid

5cm x 5cm grid pattern

Under mattress on table

Less vulnerable to body habitus

No parallax and kinking of cord

WhatWhat’s the point?’s the point?

• Preoperative planning is the MOST IMPORTANTPreoperative planning is the MOST IMPORTANT

• Wedge geometry for OW or CW is complex – must Wedge geometry for OW or CW is complex – must adjust for coronal and sagittal plane!adjust for coronal and sagittal plane!

• Intraoperative tools are limited…Intraoperative tools are limited…

• Bovie cord OK for thin people with moderate Bovie cord OK for thin people with moderate correction as a confirmatory toolcorrection as a confirmatory tool

• Intraoperative grids or computer navigation may prove Intraoperative grids or computer navigation may prove to be much better tools...to be much better tools...

Clinical Results/OutcomesClinical Results/Outcomes

PL Instability and/or Hyperextension ThrustPL Instability and/or Hyperextension Thrust

• Naudie, CORR 2004Naudie, CORR 2004

• 17 AMOWO in 16 pts w/ instability (Isolated PCL 4, PCL/PL 7, 17 AMOWO in 16 pts w/ instability (Isolated PCL 4, PCL/PL 7, ligamentous laxity 5)ligamentous laxity 5)

• 15/16 satisfied, all reported improvement in stability15/16 satisfied, all reported improvement in stability

• Post-op average coronal alignment: 6 degrees valgusPost-op average coronal alignment: 6 degrees valgus

• Mean increase in posterior slope: 8 degreesMean increase in posterior slope: 8 degrees

• However, 5 pts had subsequent PCL reconstruction surgery to gain However, 5 pts had subsequent PCL reconstruction surgery to gain additional stabilityadditional stability

Clinical Results/OutcomesClinical Results/Outcomes

PL Instability and/or Hyperextension ThrustPL Instability and/or Hyperextension Thrust

• MacGillivray and Warren, Operative Techniques in Orthopedics, MacGillivray and Warren, Operative Techniques in Orthopedics, 19991999

• Valgus-producing HTO alone can provide sufficient relief of Valgus-producing HTO alone can provide sufficient relief of chronic posterolateral instability symptomschronic posterolateral instability symptoms

• Not necessarily role for ligamentous reconstuction in all casesNot necessarily role for ligamentous reconstuction in all cases

• May be staged, with assessment of results of osteotomy guiding May be staged, with assessment of results of osteotomy guiding treatment plantreatment plan

Clinical Results/OutcomesClinical Results/Outcomes

ACL Deficient + VarusACL Deficient + Varus

• Dejour, CORR 2004Dejour, CORR 2004

• 50 patients w/ chronic ACL deficiency + acquired varus alignment50 patients w/ chronic ACL deficiency + acquired varus alignment

• Osteotomy (74% lateral closing wedge) + ACL reconstruction (BTB auto)Osteotomy (74% lateral closing wedge) + ACL reconstruction (BTB auto)

• All pts w/ slope >10All pts w/ slope >10°° had biplanar closing wedge (to decrease slope) had biplanar closing wedge (to decrease slope)

• Mean f/u 3.6 yrsMean f/u 3.6 yrs

• PT satisfaction 91%PT satisfaction 91%

• Contact/pivot sports 37% (pre-op) Contact/pivot sports 37% (pre-op) →→ 14% (post-op); Leisure sports 45% 14% (post-op); Leisure sports 45% (pre-op) (pre-op) →→ 60% (post-op) 60% (post-op)

• No OA progressionNo OA progression

Clinical Results/OutcomesClinical Results/Outcomes

ACL Deficient, PL Instable + VarusACL Deficient, PL Instable + Varus

• Noyes, AJSM 2000Noyes, AJSM 2000

• 41 patients w/ ACL deficiency (15 pts, 19 prior ACL recon failures) , varying 41 patients w/ ACL deficiency (15 pts, 19 prior ACL recon failures) , varying degrees of PL deficiency + varus alignmentdegrees of PL deficiency + varus alignment

• Mean age 32 y/o (range, 16-47 y/o)Mean age 32 y/o (range, 16-47 y/o)

• 73% no medial meniscus, 65% marked OA73% no medial meniscus, 65% marked OA

• Lateral closing wedge osteotomy/fibular osteotomy + (staged, 8 mo) ACL Lateral closing wedge osteotomy/fibular osteotomy + (staged, 8 mo) ACL reconstruction (83%) +/- PL reconstruction (58%)reconstruction (83%) +/- PL reconstruction (58%)

• Heterogenous group in presentation/surgeryHeterogenous group in presentation/surgery

• Significant improvements in 2 yr f/u pain, swelling, giving waySignificant improvements in 2 yr f/u pain, swelling, giving way

• Cinncinati Knee Score (63 Cinncinati Knee Score (63 →→ 82) 82)

• Key to success: preservation of joint to allow for anatomic (PL) Key to success: preservation of joint to allow for anatomic (PL) ligament/insertion lengths and prevent proximal fibular (head) migrationligament/insertion lengths and prevent proximal fibular (head) migration

TakeawaysTakeaways• Osteotomy has Osteotomy has

potential to address potential to address pain, swelling, pain, swelling,

instability at onceinstability at once• Role for combined Role for combined

osseous/soft tissue osseous/soft tissue proceduresprocedures

• Soft tissue procedures Soft tissue procedures in a malaligned limb in a malaligned limb

will failwill fail• Alignment is key, as is Alignment is key, as is

preop understanding preop understanding and plan for desired and plan for desired

changeschanges

TakeawaysTakeaways

• Symptomatic Symptomatic chronic isolated chronic isolated PCL PCL deficiency/genu deficiency/genu recurvatum (back recurvatum (back knee thrust/ knee thrust/ hyperextension) hyperextension) →→ pure sagital pure sagital osteotomy (Ant osteotomy (Ant OWO)OWO)

TakeawaysTakeaways

• PCL deficiency, varus, PCL deficiency, varus, medial OA medial OA →→ biplanar Ant biplanar Ant

Med OWOMed OWO

• ACL Deficiency ACL Deficiency →→ Increasing posterior tibial Increasing posterior tibial slope should be avoided, slope should be avoided, decreasing slope may be decreasing slope may be

beneficialbeneficial• LCWO may be easier, LCWO may be easier,

MOWO has benefits and MOWO has benefits and can work if slope is can work if slope is

maintained/decreasedmaintained/decreased

TakeawaysTakeaways

• ACL Deficiency w/ varus ACL Deficiency w/ varus malalignment malalignment →→ some some authors feel osteotomy authors feel osteotomy

should be done should be done empirically; others only if empirically; others only if

varus thrusvarus thrus

• HTO/reconstruction may HTO/reconstruction may be staged, but some be staged, but some

suggestion that combined suggestion that combined may do as well w/ shorter may do as well w/ shorter

rehabrehab

•Mechanical Axis (a):Mechanical Axis (a): • Center of fem head Center of fem head center of knee center of knee• 0-2.20-2.2° valgus° valgus

•Anatomic Axis (b): Anatomic Axis (b): • Center of fem shaft Center of fem shaft center tibial shaftcenter tibial shaft• 5-75-7° valgus° valgus

Important AxesImportant Axes

What is the goal correction?What is the goal correction?

• Coventry Coventry 8 8° of anatomic valgus° of anatomic valgus• Hernigou Hernigou 3-6° valgus mechanical axis 3-6° valgus mechanical axis

• Dugdale Dugdale 62-66% of tib plateau width through lateral compartment 62-66% of tib plateau width through lateral compartment• Miniaci Miniaci 60-70% width of tibial plateau in lateral compartment 60-70% width of tibial plateau in lateral compartment

• All agree that some overcorrection is necessaryAll agree that some overcorrection is necessary

• Fujisawa Fujisawa 62% width lateral to the center of the knee 62% width lateral to the center of the knee best results after 54 closing wedge HTO’s achieved when

MA line crossed LTP at 62% tibial plateau width (~3-5deg valgus) Fujisawa et al. Orthop Clin North Am. 1979; 10(3):585-608.

Avoiding OvercorrectionAvoiding Overcorrection• Rosenberg (WB Bilateral in 45Rosenberg (WB Bilateral in 45° flexion)° flexion)

• Measure Measure ∆ ∆ in lateral joint separationin lateral joint separation• Overcorrection angle Overcorrection angle

• = = 76.4 x (76.4 x (∆∆ lat joint) lat joint) (Dugdale, Noyes) (Dugdale, Noyes) total plateau widthtotal plateau width• defines extent of varus due to slack lateral restraintsdefines extent of varus due to slack lateral restraints• per mm separation ~ 1 deg of angular deformity on WB film per mm separation ~ 1 deg of angular deformity on WB film • subtract from correction suggested by WB filmsubtract from correction suggested by WB film

Preop Planning Preop Planning (Dugdale/Noyes 1992)(Dugdale/Noyes 1992)

• full length NWB AP

• line from center of fem head to 62%

• line from center of plafond to 62%

• angle subtended = angle of correction required

• full length NWB AP

• line from center of fem head to 62%

• line from center of plafond to 62%

• angle subtended = angle of correction required

• cut film at desiredosteotomy site andshift until WBL is corrected

•angle of wedge should = angle of correction required

Preop Planning Preop Planning (Dugdale/Noyes 1992)(Dugdale/Noyes 1992)

Calculate Wedge HeightCalculate Wedge Height

•ØØ

Calculate Wedge HeightCalculate Wedge Height

•ØØTibial width

Wedge Height

Wedge angle ØWedge angle Ø

Calculate Wedge HeightCalculate Wedge Height

•ØØ

Wedge angle ØWedge angle Ø

Tibial width

Wedge Height

Tan Ø = Ø = oppositeopposite adjacentadjacent

Tan Ø = Ø = Wedge heightWedge height Tibial widthTibial width

Tibial width x Tibial width x Tan Ø = Ø = Wedge Wedge heightheight

Accommodate Sagittal Slope

• Proximal tibia geometry:• Perpendicular to posterior

cortex laterally• Oblique (~45deg) medially

Noyes et al. AJSM 2005

Accommodate Sagittal Slope

• Proximal tibia geometry:• Perpendicular to posterior

cortex laterally• Oblique (~45deg) medially

Noyes et al. AJSM 2005

Medial opening wedge with equal anterior and posterior gaps would INCREASE slope

Accommodate Sagittal Slope

• Proximal tibia geometry:• Perpendicular to posterior

cortex laterally• Oblique (~45deg) medially

Noyes et al. AJSM 2005

Medial opening wedge with equal anterior and posterior gaps would INCREASE slope

To maintain slope, anterior gap at tubercle should be HALF of gap at posteromedial cortex

Every 1-mm error will result in a 2° change in tibial slope

Summary - Preop PlanningSummary - Preop Planning

•Determine desired correction angle, subtracting for soft-tissue component

•Calculate anticipated wedge size

•Varies with level of osteotomy

•TTW (true tibial width)•Ø correction angle•= TTW x (tan Ø)•can be readily measured

in the OR•Adjust anterior vs.

posterior wedge height prn for

desired slope

Intraop: Assessing CorrectionIntraop: Assessing Correction

•Location of Location of osteotomy osteotomy consistent consistent

with with preoperative preoperative

planplan•ConfirmatioConfirmatio

n of n of compatible compatible wedge sizewedge size

•Reassess Reassess slope with slope with lateral xraylateral xray

Dugdale’s Trig

Techniques (Miniaci)Techniques (Miniaci)

WBL

“Hinge” point at osteotomy site ~2cm distal to joint line

Define arc of correction to center oftibiotalar joint

Defines correction angle for openingor closing wedge procedure

Techniques (Coventry)Techniques (Coventry)

Calculate difference between thepreoperative anatomic axis and theplanned anatomic axis

Noyes et al, AJSM 2005Noyes et al, AJSM 2005

•Three triangle geometric analysisPlaces Keith needles in anteromedial and posteromedial joint line to

assess slope2 guide pins placed distally for medial osteotomy line (from anterior to

posterior) must be perpendicular to joint line to maintain slope •With a standard metaphyseal osteotomy…

•Anterior gap at tubercle should be HALF of gap at posteromedial cortex•Advocates triangular wedges of bicortical iliac crest to maintain •Every 1-mm error will result in a 2° change in tibial slope

Incr Slope Dec Slope

Creation of Wedge

Creation of Wedge

Creation of Wedge