High Yield Overview

COMPREHENSIVE KNEE OSTEOTOMY: HTO, DFO, AND TTO

HTO: Medial approach to proximal tibia (longitudinal or oblique over pes anserinus). DFO: Lateral approach to distal femur (longitudinal over lateral femoral condyle). TTO: Anterior or anterolateral approach to tibial tubercle. | advanced

Critical Danger Structures - 5 Specific Zones

Danger Zone 1: Popliteal Vessels

Location: HTO - popliteal artery and vein lie 1-2cm posterior to posterior tibial cortex at level of osteotomy

Protection Strategy: Confirm all screw lengths on lateral fluoroscopy before insertion. Use depth gauge for every screw. Never breach posterior cortex. Keep osteotomy cuts anterior to posterior cortex safe zone.

Danger Zone 2: Common Peroneal Nerve

Location: Wraps around fibular neck 2-3cm distal and lateral to knee joint line, stays within 1-2cm of posterolateral joint margin

Protection Strategy: Limit lateral dissection in HTO. For closing wedge requiring fibular osteotomy, identify and protect nerve. Avoid excessive valgus correction >15mm causing stretch injury.

Danger Zone 3: Saphenous Nerve and Vein

Location: Courses posteromedially 5-10cm from midline, runs posterior to pes anserinus insertion in superficial subcutaneous plane

Protection Strategy: Identify early during medial approach to HTO. Gentle retraction only. Avoid aggressive cautery. Split or elevate pes anserinus as flap to protect neurovascular bundle.

Danger Zone 4: Patellar Tendon Insertion

Location: Inserts on anterior tibial tubercle, forms anterior boundary of HTO dissection, at risk during opening if ascending cut not performed

Protection Strategy: Use biplanar technique with ascending cut posterior to tubercle. This allows opening without stretching tendon. Maintain 1cm bone thickness for TTO to prevent avulsion.

Danger Zone 5: Lateral Collateral Ligament

Location: DFO - inserts on lateral femoral epicondyle, retracts posteriorly during lateral approach to distal femur

Protection Strategy: Identify LCL during exposure and retract gently posteriorly. Subperiosteal dissection anterior to LCL between vastus lateralis and ligament. Avoid deep posterior dissection.

Mnemonic

HINGEHINGE - Critical Elements for HTO Success

Mnemonic

CORRECTCORRECT - Planning Knee Osteotomy Alignment

Indications

High Tibial Osteotomy (HTO)

Primary indication: Medial compartment osteoarthritis or chondral defect with varus malalignment
Patient selection: Young active patients <60-65 years
Deformity: Varus malalignment with mechanical axis passing through medial compartment
Joint status: Isolated medial compartment disease, intact lateral compartment
Range of motion: >90° flexion required
Stability: Intact or reconstructable ligaments (ACL/PCL)
Activity level: Desire to maintain or return to impact activities
Failed conservative management: Physiotherapy, injections, bracing, weight loss

Distal Femoral Osteotomy (DFO)

Primary indication: Lateral compartment osteoarthritis or chondral defect with valgus malalignment
Patient selection: Young active patients <60 years (less common than HTO)
Deformity: Valgus malalignment with mechanical axis passing through lateral compartment
Joint status: Isolated lateral compartment disease, intact medial compartment
Extra-articular deformity: Femoral-based valgus deformity
Combined with HTO: For double-level osteotomy in severe deformity

Tibial Tubercle Osteotomy (TTO)

Primary indication: Patellofemoral osteoarthritis or chondrosis with patellar maltracking or overload
Patient selection: Young patients <50-55 years
Pathology: Isolated patellofemoral compartment disease
Maltracking: Lateral patellar tilt, subluxation (J-sign), alta or baja
Chondral damage: Focal lateral or distal patellar lesions
Failed conservative management: Physiotherapy, bracing, activity modification

Contraindications

Absolute Contraindications

Inflammatory arthritis (rheumatoid, psoriatic) - systemic disease continues
Severe tricompartmental osteoarthritis - osteotomy ineffective
Active infection - local or systemic
Severe peripheral vascular disease - healing concerns
Patient unable to comply with protected weight-bearing protocol

Relative Contraindications

Age >65 years - consider arthroplasty instead
Obesity (BMI >35) - increased failure rate, delayed healing
Current smoker - doubles non-union risk
Flexion contracture >15° - limits functional improvement
Ligamentous instability - address concurrently or contraindication
Significant patellofemoral arthritis (for HTO/DFO) - may worsen symptoms
Unrealistic patient expectations

Preoperative Planning - CRITICAL for Success

Long Leg Standing Radiographs

Technique: Full weight-bearing, hip-knee-ankle on single 51-inch cassette
Patient position: Feet shoulder-width apart, knees straight, patella forward
Image quality: Must visualize center of femoral head, knee joint, ankle joint

Mechanical Axis Measurement

Draw mechanical axis: Line from center of femoral head to center of talus
Measure MAD (Mechanical Axis Deviation): Distance (mm) from mechanical axis to center of knee
- Varus: Axis passes medial to knee center (positive MAD)
- Valgus: Axis passes lateral to knee center (negative MAD)
Calculate percentage: Where axis crosses tibial plateau (0% = medial edge, 100% = lateral edge)
- Normal: 50% (axis through knee center)
- Varus OA: Typically 20-30% (medial overload)
- Valgus OA: Typically 70-80% (lateral overload)

Target Correction

HTO for varus: Fujisawa point 62-66% lateral tibial plateau width
- Corresponds to 3-5° valgus mechanical axis
- Slight overcorrection unloads medial compartment
DFO for valgus: Target 55-60% medial (slight varus)
- Unloads lateral compartment
Undercorrection = early failure
Excessive overcorrection = opposite compartment overload

Correction Angle Calculation Methods

Critical Yield Data

Additional Imaging

CT scan: If intra-articular deformity suspected
MRI: Assess cartilage status, meniscus, ligaments, bone marrow edema
Stress X-rays: Evaluate correctability of deformity

Step 1: Preoperative Planning - Mechanical Axis and Correction Angle

CRITICAL PLANNING STEP: Standing LONG LEG RADIOGRAPHS (hip-knee-ankle) with patient weight-bearing required. Measure current mechanical axis line (center of femoral head to center of ankle). Document mechanical axis deviation (MAD) - how many mm medial or lateral of knee center. Determine percentage of tibial plateau width where axis passes.

TARGET CORRECTION:

HTO for varus: Fujisawa point 62-66% lateral (3-5° valgus)
DFO for valgus: 55-60% medial (slight varus)

Calculate CORRECTION ANGLE using:

Miniaci method: Trigonometric calculation
Dugdale method: Geometric approach
Digital planning software (TraumaCad, Orthoview): Most accurate

Consider wedge SIZE: opening wedge HTO typically 8-15mm gap, closing wedge removes 8-15mm. Plan screw trajectory and plate position. Templating with digital software ideal.

Exam Pearl

Technical Tip: EXAM KEY: 'Planning on LONG LEG STANDING films is CRITICAL. I calculate mechanical axis currently (varus measures MAD medial to knee center), and TARGET axis (Fujisawa point 62-66% lateral for HTO = 3-5° valgus mechanical axis). This determines correction angle. I use Miniaci or digital planning. Undercorrection fails quickly; overcorrection overloads opposite compartment. Goal: neutral to slight overcorrection.'

Dangers at this step

Undercorrection = persistent overload, early failure (MOST COMMON planning error)
Overcorrection = overload opposite compartment, poor outcomes
Incorrect mechanical axis measurement (ensure full weight-bearing films)
Inadequate planning = intraoperative guessing

Step 2: Patient Positioning and Fluoroscopy Setup

Position supine with bump under ipsilateral hip (internal rotation exposes medial tibia for HTO or lateral femur for DFO). Radiolucent triangle bolster at distal thigh allows knee flexion. Prep and drape entire limb from groin to toes with leg free.

Test C-arm imaging: obtain PERFECT AP and LATERAL views of proximal tibia (HTO) or distal femur (DFO) - must see joint line and osteotomy site clearly. Ensure ability to obtain full-length hip-to-ankle AP view intraoperatively for final alignment check.

Mark anatomic landmarks on skin: joint line, pes anserinus, patellar tendon, tibial tubercle, fibular head.

Exam Pearl

Technical Tip: EXAM KEY: 'Perfect imaging is essential for accuracy. I test C-arm positioning before incision - need clear AP and lateral of osteotomy site AND ability to get full hip-to-ankle view for final alignment check. Bump under hip rotates limb internally exposing medial tibia. I mark key landmarks before draping to guide incision placement.'

Dangers at this step

Inadequate fluoroscopy setup = inability to confirm correction intraoperatively
Poor AP/lateral views = malpositioned osteotomy or hardware
Unable to obtain full-length view = unknown final alignment

Step 3: Surgical Approach and Exposure - HTO

FOR OPENING WEDGE HTO (most common): Longitudinal or oblique incision 6-8cm over anteromedial proximal tibia, starting at joint line and extending distally.

Identify and protect SAPHENOUS NERVE and vein (posterior to pes anserinus).

Identify PES ANSERINUS (gracilis, semitendinosus, sartorius) - elevate as flap or split. Expose medial proximal tibia from posteromedial corner to anterior (protect patellar tendon insertion anteriorly). Subperiosteal elevation. Palpate POSTERIOR BORDER of tibia to ensure complete medial exposure.

FOR CLOSING WEDGE HTO (less common): Similar approach but may need fibular osteotomy first for lateral closing.

Exam Pearl

Technical Tip: EXAM KEY: 'For OPENING WEDGE HTO, I use anteromedial approach. I identify and protect saphenous nerve posteriorly. Pes anserinus identified - can elevate as flap or split through. COMPLETE medial exposure from posteromedial corner to anterior, staying subperiosteal. I palpate posterior border to confirm exposure - important for guide wire trajectory.'

Dangers at this step

Saphenous nerve injury (posterior to pes, 5-10cm from midline)
MCL injury (deep fibers insert on tibia)
Patellar tendon injury (anterior boundary)
Inadequate exposure = malpositioned osteotomy

Step 4: Surgical Approach and Exposure - DFO

FOR DISTAL FEMORAL OSTEOTOMY: Lateral longitudinal incision 8-10cm over distal lateral femoral metaphysis, from lateral epicondyle extending proximally.

Incise fascia lata and iliotibial band in line with fibers. Identify and protect LATERAL COLLATERAL LIGAMENT (LCL) - typically retracts posteriorly.

Elevate vastus lateralis off lateral intermuscular septum (anterior) and identify posterior border. Subperiosteal exposure of lateral distal femur. Stay anterior to LCL and posterior to vastus. Expose adequately for plate placement.

Exam Pearl

Technical Tip: EXAM KEY: 'For DFO lateral approach, I incise through IT band over distal femur. Identify and protect LCL posteriorly. Subperiosteal elevation between vastus lateralis anteriorly and LCL/posterior structures. Need adequate exposure for distal femoral locking plate placement.'

Dangers at this step

LCL injury (causes valgus instability)
Common peroneal nerve (deeper, posterior - usually not at risk unless dissect posteriorly)
Vastus lateralis denervation from aggressive dissection
Inadequate anterior or posterior exposure

Step 5: Guide Wire Placement and Osteotomy Planning - HTO

CRITICAL STEP FOR HTO: Place guide wire on MEDIAL cortex 4-5cm below JOINT LINE (measured on fluoroscopy), angled toward FIBULAR HEAD (lateral and proximal), stopping 1cm from LATERAL CORTEX (this will be the hinge).

Wire trajectory is 5-10° posterior-to-anterior angulation (matches posterior tibial slope).

Confirm wire position on BOTH AP (toward fibular head, 1cm from lateral cortex) and LATERAL (parallel to joint, respecting slope). Wire serves as guide for osteotomy cut. This wire position is CRITICAL for proper hinge location and avoiding complications.

Exam Pearl

Technical Tip: EXAM KEY: 'Guide wire is CRITICAL - determines osteotomy trajectory. I place wire 4-5cm below joint line on medial cortex, aim toward fibular head, stop 1cm from lateral cortex. That lateral cortex is my HINGE - must preserve or get hinge fracture. I confirm on AP (toward fibular head) and lateral (parallel to joint, respects slope). Wire typically 5-10° posterior slope matching native.'

Dangers at this step

Wire too close to joint line (<3.5cm) = intra-articular fracture
Wire too distal (>6cm) = stress riser, fracture risk
Wire violates lateral cortex = NO hinge, unstable osteotomy
Wire not parallel to joint = alters tibial slope
Wire too anterior or posterior = non-anatomic

Step 6: Osteotomy Cut - Biplanar Technique HTO

BIPLANAR OPENING WEDGE TECHNIQUE: Using oscillating saw along guide wire, make HORIZONTAL cut from medial cortex toward lateral, stopping 1cm from lateral cortex (preserve hinge). Cut depth approximately 75-80% of tibial width.

Second cut: ASCENDING cut posterior and proximal behind patellar tendon insertion (anterior to horizontal cut level) - this protects patellar tendon during opening and prevents patella baja. The ascending cut angles 15-20° posterior.

Use multiple osteotomes to complete cut but DO NOT breach lateral cortex hinge. Check mobility before full completion.

Exam Pearl

Technical Tip: EXAM KEY: 'BIPLANAR cut: HORIZONTAL along wire to 1cm from lateral cortex, then ASCENDING cut behind patellar tendon. The ascending cut is KEY - protects patellar tendon during opening and prevents patella BAJA (common complication of HTO). I use saw for cortical cuts, then multiple osteotomes to complete, checking mobility progressively but preserving hinge.'

Dangers at this step

Lateral hinge fracture (MOST COMMON complication HTO, 10-25%)
Patellar tendon injury (ascending cut prevents this)
Intra-articular fracture (wire/cut too proximal)
Posterior cortex fracture (aggressive osteotome use)
Incomplete cut (prevents opening)

Step 7: Osteotomy Cut - DFO Technique

FOR DISTAL FEMORAL OSTEOTOMY: Place guide wire on LATERAL cortex 6-7cm PROXIMAL to joint line, angled toward medial cortex, stopping 1cm from medial cortex (hinge). Confirm on AP and lateral fluoroscopy.

For OPENING WEDGE DFO (more common now): Saw cut along wire to 1cm from medial cortex. Progressive osteotome completion preserving medial hinge.

For CLOSING WEDGE DFO: Mark wedge based on planned correction angle, make two saw cuts converging laterally, remove bone wedge, close osteotomy.

Exam Pearl

Technical Tip: EXAM KEY: 'For DFO, guide wire 6-7cm ABOVE joint line on lateral cortex, aimed toward medial, stop 1cm from medial cortex (that's the hinge). Opening wedge DFO now more common than closing. Principles same as HTO but on femur: preserve hinge, adequate fixation with locking plate, gradual opening.'

Dangers at this step

Medial hinge fracture in DFO
Supracondylar fracture into joint
Neurovascular injury (femoral vessels medially, avoid deep dissection)
Inadequate fixation in distal femoral bone (osteoporotic)

Step 8: Gradual Osteotomy Opening and Alignment Correction

Insert calibrated SPREADER into osteotomy cut. GRADUALLY open in 1-2mm increments - slow opening protects hinge from fracture. Open to PRE-CALCULATED correction.

Intraoperative alignment check methods:

CABLE TEST: Sterile cable from center of femoral head to center of ankle, should pass through Fujisawa point (62-66% lateral) - use C-arm to verify
INTRAOPERATIVE LONG LEG X-RAY if available
Clinical assessment with limb alignment

Adjust opening if needed for perfect correction. For CLOSING WEDGE: close osteotomy after wedge removal, align, check correction same methods.

Exam Pearl

Technical Tip: EXAM KEY: 'I open GRADUALLY with calibrated spreaders - 1-2mm increments. Too rapid opening FRACTURES hinge. Open to calculated correction then CHECK alignment. CABLE TEST: sterile cable from hip center to ankle center, use C-arm to verify passes through Fujisawa point (62-66% for HTO). Intraop long leg film is gold standard but not always available. Fine-tune opening if needed.'

Dangers at this step

Rapid opening = hinge fracture (COMMON)
Undercorrection = failure to offload compartment
Overcorrection = overload opposite compartment, stiffness
No intraoperative alignment check = unknown final correction

Step 9: Bone Graft or Substitute for Opening Wedge

For OPENING WEDGE gaps >10mm: Consider bone graft or substitute to promote healing and support correction.

Options:

AUTOGRAFT from iliac crest (gold standard, best biology, donor site morbidity)
Local bone from tibial or femoral cuts if available
ALLOGRAFT cancellous chips (no donor morbidity, osteoconductive)
BONE SUBSTITUTE (calcium phosphate, hydroxyapatite - osteoconductive but slower incorporation)

Wedges <10mm often heal without graft. Place graft to support medial opening (HTO) or lateral opening (DFO), behind and beneath plate.

Exam Pearl

Technical Tip: EXAM KEY: 'For gaps >10mm I use bone graft or substitute. ALLOGRAFT cancellous chips are my preference - no donor morbidity, reliable healing. Autograft iliac crest is gold standard but donor site pain. Synthetic substitutes work but slower. Wedges <8-10mm often heal without graft. Graft supports correction and promotes faster healing, reduces non-union risk (5-10% without graft in large gaps).'

Dangers at this step

Large gap without graft = delayed union or non-union (5-10%)
Graft collapse = loss of correction
Iliac crest donor site morbidity (pain, hematoma, infection) if autograft

Step 10: Internal Fixation - Locking Plate Application

HTO: Apply medial proximal tibial LOCKING PLATE (Tomofix, Puddu, numerous brands available). Plate contours to medial tibia. Secure plate to tibia first with proximal locking screws (typically 3-4 screws in proximal metaphyseal segment above osteotomy) and distal screws (3-4 screws in diaphysis below osteotomy).

Locking screws provide angular stability - critical in metaphyseal bone. Confirm screw lengths don't penetrate posterior cortex (risk to popliteal vessels) or lateral cortex (hinge damage).

DFO: Apply lateral distal femoral LOCKING PLATE. Proximal screws in femoral shaft, distal screws in distal metaphyseal fragment. Similar principles. Confirm alignment and fixation on fluoroscopy.

Exam Pearl

Technical Tip: EXAM KEY: 'LOCKING PLATES essential for angular stability in metaphyseal bone. For HTO, medial plate with 3-4 screws proximal and distal to osteotomy. Check screws on LATERAL fluoroscopy - must not penetrate posterior cortex (popliteal vessels risk). Locking technology allows better purchase in osteoporotic or metaphyseal bone compared to conventional plates.'

Dangers at this step

Screws too long penetrating posterior cortex (HTO - popliteal vessels 1-2cm posterior)
Screws violating lateral hinge (causes fracture)
Screws into joint (proximal screws must be below joint line)
Inadequate fixation (too few screws, non-locking in poor bone)
Plate malposition (not contoured, proud, irritation)
Loss of correction due to fixation failure

Step 11: Tibial Tubercle Osteotomy (TTO) - Anteriorization or Medialization

FOR PATELLOFEMORAL OVERLOAD/MALTRACKING: TTO ANTERIORIZATION (Fulkerson osteotomy): Anterior approach or anterolateral approach to tibial tubercle. Mark tibial tubercle and patellar tendon insertion.

Create oblique osteotomy of tubercle starting distally and angling anteriorly and medially (anteromedial transfer). Osteotomy 5-6cm long, maintaining 1cm bone thickness beneath tubercle.

Transfer tubercle anteriorly 10-15mm (decreases patellofemoral contact forces) and/or medially 5-10mm (corrects lateral maltracking). Fix with 3-4 cortical screws from anterior tubercle into tibia. TTO DISTALIZATION less common, for patella alta. Ensure no posterior cortex violation (popliteal vessels).

Exam Pearl

Technical Tip: EXAM KEY: 'TTO for patellofemoral pathology. FULKERSON anteromedial transfer: tubercle osteotomy angled anteriorly and medially. ANTERIORIZATION decreases patellofemoral contact force (treats chondrosis/arthritis). MEDIALIZATION corrects LATERAL maltracking (J-sign, subluxation). Typically combined anteromedial. 5-6cm osteotomy length, maintain 1cm bone thickness, fix with screws. Transfer 10-15mm anterior and/or 5-10mm medial.'

Dangers at this step

Fracture propagation into tibial articular surface
Patellar tendon avulsion (inadequate bone thickness, <1cm)
Compartment syndrome (anterior compartment swelling from bleeding)
Hardware irritation (screws prominent anteriorly)
Insufficient correction (inadequate transfer)
Excessive medialization (medial overload)

Step 12: Final Alignment Check and ROM Assessment

CRITICAL STEP: Final intraoperative alignment verification.

Options:

CABLE TEST with C-arm - cable from hip to ankle, document mechanical axis passing through target (Fujisawa 62-66% for HTO, 55-60% for DFO)
INTRAOPERATIVE LONG LEG STANDING X-RAY if available (most accurate)
Clinical assessment - limb appears aligned, varus/valgus stress test neutral

Cycle knee through FULL ROM - smooth? No impingement? Hardware not limiting ROM? Test stability - osteotomy site stable? Check neurovascular status. Document final fluoroscopic images of alignment and hardware position.

Exam Pearl

Technical Tip: EXAM KEY: 'FINAL ALIGNMENT CHECK is essential - I've opened/corrected to plan but must VERIFY. Cable test with C-arm or intraop long leg film confirms mechanical axis at target. Cycle knee through ROM - should be smooth, no impingement. Test stability - osteotomy doesn't move. Any concerns, address before closure. Undercorrection is failure; overcorrection causes problems. Must get it right NOW.'

Dangers at this step

Undercorrection not recognized (early failure)
Overcorrection not recognized (opposite compartment overload)
Loss of correction during final steps
ROM limitation not recognized
Neurovascular injury not identified

Step 13: Closure and Post-Operative Protocol

Release tourniquet if used. Achieve meticulous hemostasis - minimize hematoma risk.

For HTO: Close pes anserinus fascia over plate (soft tissue coverage).

For DFO: Close vastus lateralis and IT band.

For TTO: Close anterior compartment fascia (watch for compartment tightness).

Subcutaneous closure, skin closure. Drain optional (remove 24-48 hours if used). Apply compressive dressing. HINGED KNEE BRACE for protection and to allow ROM exercises.

Post-op: Elevation and ice. X-rays to document correction and hardware position. DVT prophylaxis. Pain control.

Exam Pearl

Technical Tip: EXAM KEY: 'Meticulous hemostasis important - hematoma delays healing. I close pes fascia over plate for HTO (soft tissue coverage). Hinged brace allows protected ROM while preventing varus/valgus stress. Post-op X-rays document correction and hardware. For TTO, monitor for compartment syndrome in first 24 hours (anterior compartment at risk).'

Dangers at this step

Hematoma (delayed healing, infection risk)
Wound complications (especially over plate/hardware)
Compartment syndrome (especially TTO - anterior compartment)
Hardware irritation (prominent plate/screws)
DVT/PE risk

Step 14: Rehabilitation - Protected Weight Bearing Protocol

PHASE 1 (0-6 weeks): NWB or TOUCH weight-bearing (TWB) with crutches to protect osteotomy healing. Hinged brace for ambulation. ROM exercises in brace - goal 0-90° by 2 weeks, full ROM by 6 weeks. Quad sets, ankle pumps, gentle isometrics. NO varus/valgus stress. X-rays at 6 weeks to assess healing.

PHASE 2 (6-12 weeks): If X-ray shows healing progressing (callus formation), advance to PWB (50% then 75%). Wean crutches as tolerated. Continue ROM and strengthening.

PHASE 3 (3-6 months): FWB by 10-12 weeks if healed. Wean brace. Progressive strengthening, balance, proprioception. Stationary bike, swimming. X-rays at 3 months confirm healing.

Exam Pearl

Technical Tip: EXAM KEY: 'Protected weight-bearing 6-12 weeks until HEALING CONFIRMED on X-ray - looking for bridging callus, no gap widening. Opening wedge heals slower than closing (larger bone void). ROM encouraged early - helps cartilage and prevents stiffness. FWB when healed, typically 10-12 weeks. Return to impact activities 6-9 months, sport 9-12 months. Brace protects osteotomy from varus/valgus stress during healing.'

Dangers at this step

Early weight-bearing = loss of correction, non-union (5-10%)
Delayed union or non-union (5-10% overall, higher in large gaps without graft, smokers)
Stiffness from inadequate ROM exercises
Return to sport too early = fixation failure or re-injury

Step 15: Hardware Removal and Long-term Outcomes

HARDWARE REMOVAL: Typically elective after 12-18 months once fully healed and remodeled. Indications: hardware irritation (common with medial HTO plates - superficial position), patient request, pre-planned removal. Can often leave hardware if asymptomatic.

LONG-TERM OUTCOMES: HTO for medial compartment OA: 70-80% survival at 10 years, 60-70% at 15 years. Best outcomes: younger patients (<55), corrected to target alignment, minimal baseline arthritis, addressed concurrent pathology. DFO: similar 70-75% at 10 years. TTO: 70-80% good results for patellofemoral symptoms.

FAILURE: Gradual loss of correction, progression of arthritis, requires TKA eventually. Osteotomy DELAYS but doesn't prevent arthroplasty - buys 10-15 years in ideal patients.

Exam Pearl

Technical Tip: EXAM KEY: 'Hardware removal is common 12-18 months after HTO - plate is superficial, can be prominent. Outcomes: 70-80% survival at 10 years. HTO/DFO is BRIDGE procedure in young patients - delays TKA by 10-15 years in best cases. Not curative but protective. Best outcomes: young <55, mild-moderate arthritis, accurate correction to target, addressed instability/meniscus. Failure from undercorrection, progression of arthritis, or overcorrection damage to opposite compartment. Eventual TKA typically easier after prior osteotomy.'

Dangers at this step

Hardware failure requiring early removal (infection, loosening)
Difficulty with removal after full incorporation
Eventual need for TKA (osteotomy delays but doesn't prevent)
TKA after osteotomy may be more complex (altered anatomy, hardware)

Complications - Recognition, Prevention, Management

Major Complications of Knee Osteotomy

Post-operative Care

PHASE 1 (0-6 weeks): NWB or TWB with crutches, hinged knee brace for ambulation, ROM exercises 0-90° by 2 weeks goal (full by 6 weeks), quad sets and gentle isometrics, NO varus/valgus stress, elevation and ice, DVT prophylaxis, X-rays at 6 weeks for healing assessment.

PHASE 2 (6-12 weeks): If healing on X-ray (callus formation, no gap widening), progressive PWB 50-75-100%, wean crutches as tolerated, continue ROM to full, progressive strengthening (closed chain preferred), stationary bike when 90° flexion.

PHASE 3 (3-6 months): FWB by 10-12 weeks if healed on X-ray, wean brace by 3-4 months, advanced strengthening and balance, swimming and elliptical, functional activities, X-ray at 3 months confirms healing.

PHASE 4 (6-12 months): Return to impact activities 6-9 months (jogging, sports), full return to sport 9-12 months when strength >90%, full ROM, no pain/effusion. Hardware removal optional 12-18 months if symptomatic. Annual X-rays first 3-5 years to monitor alignment and arthritis progression.

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

EXAMINER

"Explain mechanical axis and Fujisawa point for HTO planning. Why is this critical?"

EXCEPTIONAL ANSWER

MECHANICAL AXIS is the line from center of femoral head to center of ankle - represents overall limb alignment and force transmission through the knee. NORMAL: axis passes through knee center (50% of tibial plateau width). VARUS DEFORMITY: axis shifted MEDIALLY (passes through medial 20-30% of plateau), overloading medial compartment causing medial OA and cartilage breakdown. FUJISAWA POINT is the TARGET for HTO correction: 62-66% LATERAL tibial plateau width, corresponding to 3-5° VALGUS mechanical axis. This shifts forces from diseased medial compartment to healthier lateral compartment. CRITICAL because: 1) Undercorrection to <62% leaves medial overload and early failure, 2) Overcorrection beyond 70% overloads lateral compartment and causes new problems, 3) Accurate correction to Fujisawa gives best outcomes - 80% survival at 10 years. I measure current axis on standing long leg films, calculate correction angle needed using Miniaci method or digital planning, and verify intraoperatively with cable test or long leg X-ray. This is THE most important planning step.

VIVA SCENARIOStandard

EXAMINER

"Compare opening wedge versus closing wedge HTO - which do you prefer and why?"

EXCEPTIONAL ANSWER

I prefer OPENING WEDGE HTO, which is now the most common technique worldwide. OPENING WEDGE: Single biplanar cut on medial tibia (horizontal + ascending cuts), gradually open to target correction, insert bone graft/substitute if gap >10mm, fix with medial locking plate. ADVANTAGES: 1) Single cut faster and less traumatic than double cuts, 2) Adjustable intraoperatively - can fine-tune opening to perfect correction, 3) Preserves bone stock - no bone removal, 4) No fibular osteotomy needed (closing often requires this), 5) Easier to combine with other procedures (ACL, meniscus). DISADVANTAGES: 1) Creates gap requiring healing - slower union (10-12 weeks vs 8 weeks closing), 2) Needs bone graft if gap >10mm (donor morbidity for autograft or cost for allograft), 3) Higher delayed union/non-union rate 5-10%, 4) Increases posterior tibial slope which can affect ACL. CLOSING WEDGE: Two converging cuts to create wedge, remove bone, close osteotomy. ADVANTAGES: Bone-to-bone contact heals faster. DISADVANTAGES: 1) Removes bone stock, 2) Often requires fibular osteotomy (peroneal nerve risk), 3) Less adjustable, 4) More extensive dissection. OUTCOMES: Level 1 evidence shows no difference in clinical results at 5 years, but opening has become preferred for technical advantages despite slower healing.

VIVA SCENARIOStandard

EXAMINER

"Describe guide wire placement for HTO and why it's critical. What are the consequences of getting this wrong?"

EXCEPTIONAL ANSWER

Guide wire is CRITICAL - it determines the entire osteotomy trajectory, hinge location, and ultimate success. TECHNIQUE: I place wire on MEDIAL CORTEX exactly 4-5cm BELOW the joint line (measured with fluoroscopy), angled toward FIBULAR HEAD (proximal and lateral direction), stopping EXACTLY 1cm from LATERAL CORTEX. I confirm perfect position on BOTH views: AP shows wire aimed toward fibular head and stops 1cm from lateral cortex, LATERAL shows wire parallel to joint line respecting native posterior slope (typically 5-10°). That 1cm of intact LATERAL CORTEX is the HINGE - absolutely must preserve. WHY CRITICAL: 1) DISTANCE FROM JOINT LINE: Too proximal <3.5cm risks intra-articular fracture into joint, too distal >6cm creates stress riser and fracture risk at excessive distance, 2) HINGE LOCATION: Must stop 1cm from lateral cortex - if violate lateral cortex you have NO hinge and unstable osteotomy prone to fracture (most common complication 10-25%), 3) SLOPE: Wire must be parallel to joint on lateral view to maintain native posterior tibial slope - if angled wrong you inadvertently change slope affecting patellofemoral mechanics and cruciate ligaments, 4) DIRECTION: Must aim toward fibular head for proper varus correction - if aimed wrong the correction plane is incorrect. CONSEQUENCES OF ERRORS: Wire too proximal = intra-articular fracture. Wire violates lateral cortex = hinge fracture type III, instability. Wire wrong slope = altered tibial mechanics. Wire too distal = tibial fracture through stress riser.