import { ComparisonTable, ContentSection, EvidenceCard, ExamCheatSheet, ExamPearl, ExamWarning, InfoCard, InfoCardGrid, MedicalImage, MnemonicCard, OnePagerSummary, SafetyAlert, Tab, Tabs, Timeline, TimelineItem, VivaScenario, VivaScenarioSection } from '@/components/mdx' **Wrong patient = failed osteotomy**. Must have: Isolated **medial compartment OA** (Ahlbäck Grade 1-2), varus malalignment under 15°, age 40-60 years, active lifestyle, BMI under 30. Absolute contraindications: inflammatory arthritis, tibio-femoral instability, flexion contracture over 15°, ROM under 90°, patellofemoral arthritis with symptoms. **Plan with full-length standing films**. Measure mechanical axis deviation (MAD), medial proximal tibial angle (MPTA), joint line convergence angle (JLCA). Target Fujisawa point at 62-65% plateau width. Calculate correction angle using trigonometry or digital planning software. Check lateral compartment status on MRI. **Opening wedge advantages**: Preserves bone stock, no fibular osteotomy, adjustable correction. **Disadvantages**: Potential for loss of correction, patellar height increase, delayed union. **Closing wedge**: More stable fixation, faster union, but removes bone and requires peroneal nerve decompression. **Common complications**: Loss of correction (5-10%), delayed union/nonunion (5%), intra-articular fracture (1-2%), compartment syndrome (under 1%). **Late failures**: Progression of lateral OA, patellofemoral symptoms, conversion to TKA at mean 10 years. Hinge fracture in 10-20% of opening wedge but usually stable. High tibial osteotomy represents a paradigm shift from historical "young patients waiting for TKA" to active **joint preservation surgery** that delays arthroplasty by 10-15 years. Modern techniques (opening wedge with locking plates) have improved outcomes dramatically - 85-90% survivorship at 10 years in well-selected patients. The procedure is experiencing a renaissance with improved patient selection, surgical navigation, and understanding of biomechanics. - **Peak age**: 45-55 years (ideal window) - **Gender**: Equal distribution M:F - **Activity level**: Active lifestyle essential for success - **BMI**: Optimal under 27, acceptable under 30 - **Occupation**: Manual laborers seek joint preservation - **Geography**: More common in Europe/Asia than North America - **Pain relief**: 80-85% report excellent pain relief at 2 years - **Function**: Significant improvement in KOOS/WOMAC scores - **Return to sport**: 60-70% return to impact activities - **Durability**: Median implant survival 10-12 years - **Conversion**: 40% convert to TKA by 15 years - **Societal**: Delays TKA, maintains bone stock for future surgery ### Varus Knee Biomechanics In varus alignment, the **mechanical axis** passes medial to the knee center, concentrating force in the medial compartment. Normal knees distribute load 60:40 (medial:lateral). Each 1° of varus increases medial compartment load by approximately 10-12%. A knee with 5° varus has 150% of normal medial load - driving progressive cartilage wear. - **Mechanical axis**: Hip center → Ankle center passes through knee center - **Mechanical axis deviation (MAD)**: 0mm from knee center - **Load distribution**: 60% medial, 40% lateral - **MPTA** (medial proximal tibial angle): 87° ± 2° - **Joint line convergence**: Parallel medial and lateral - **Mechanical axis**: Passes medial to knee center - **MAD**: Greater than 5mm medial (pathologic) - **Load distribution**: 75-80% medial in moderate varus - **MPTA**: Under 85° in tibial varus - **Progression**: 1° varus per year without correction ### HTO Correction Principles ### HTO Technique Classification ### Ahlbäck Classification of Medial OA (HTO Patient Selection) ### Ahlbäck Grade 1-2: Ideal for HTO **Key Point**: Lateral compartment must be pristine (Outerbridge 0-1 on MRI) for HTO success regardless of medial grade. These grades represent the "sweet spot" for HTO - enough disease to cause symptoms, but sufficient cartilage regeneration potential. ### Ahlbäck Grade 3-5: Poor HTO Candidates **Clinical Pearl**: Even Grade 3 medial disease with Grade 3+ lateral changes is a contraindication - shifting load to diseased compartment predicts rapid failure. This categorization helps guide the HTO vs TKA decision based on radiographic severity. ### History Taking **Pattern**: - Isolated **medial joint line pain** (load-bearing, stairs, squatting) - Worse with activity, relieved by rest (mechanical pain) - No night pain (suggests early-moderate OA, not advanced) - **Absence of lateral or patellofemoral pain** (critical for HTO candidacy) **Duration and Progression**: - Symptoms over 6-12 months minimum - Failed conservative management (physio, NSAIDs, injections, bracing) - Progression affecting work, recreation, quality of life **Activity Goals**: - Current activity level and limitations - Desired activity level post-treatment (return to work, sports) - Occupation (manual labor favors HTO for joint preservation) - Sports participation (impact activities driving symptoms) **Red Flags for Poor Outcome**: - Sedentary lifestyle (may not benefit from HTO vs TKA) - Unrealistic expectations ("cure" vs joint preservation) - Workers compensation/litigation (poor outcome predictor) ### Physical Examination **Observe from front**: Varus alignment visible (knees apart when ankles together). **Gait assessment**: Varus thrust during stance phase indicates instability (relative contraindication - requires ligament reconstruction first). **Single leg stance**: Inability to stand on affected leg for 30 seconds predicts poor outcome. **Flexion**: Measure maximum flexion - **must be over 120°** for good HTO outcome (less than 120° predicts poor function). **Extension**: Check for fixed flexion contracture - **over 15° FFD is absolute contraindication** (cannot achieve correction). **Arc**: Document total arc (ideal 0-130° or better). **ACL**: Lachman and anterior drawer tests - **must be negative** (ACL deficiency is absolute contraindication - reconstruct first). **PCL**: Posterior drawer and sag sign - must be intact. **MCL/LCL**: Varus and valgus stress at 0° and 30° - grade any instability. **Varus stress radiographs**: Joint should open to near-normal width (confirms correctability vs fixed deformity). **Medial joint line**: Tenderness confirms medial compartment disease. **Lateral joint line**: **Must be painless** - any lateral tenderness suggests bicompartmental disease (contraindication). **Patellofemoral**: Grind test and compression - symptomatic PF is relative contraindication. **Peroneal nerve**: Palpate at fibular neck, test ankle/toe dorsiflexion and foot eversion (document for medicolegal purposes - especially important for closing wedge HTO). **Pulses**: Palpate dorsalis pedis and posterior tibial pulses. **Sensation**: Check distribution, particularly first web space (deep peroneal). **Varus thrust** (sudden increase in varus angulation during stance phase of gait) indicates functional instability of medial structures (stretched MCL, meniscal deficiency, or bone loss). This is a **relative contraindication** to isolated HTO - consider ligament reconstruction or meniscal allograft transplantation concurrent with HTO, or recommend TKA instead. Performing HTO alone in presence of thrust leads to early failure (loss of correction, continued instability symptoms). ### Radiographic Assessment **Views**: Standing hip-to-ankle AP radiograph (full mechanical axis visible from femoral head to ankle mortise). **Technical requirements**: True weight-bearing (patient on both feet), knees straight, patellae facing forward (not rotated). **Measurements**: Mechanical axis deviation (MAD) from knee center, medial proximal tibial angle (MPTA), lateral distal femoral angle (LDFA), joint line convergence angle (JLCA). **Purpose**: Calculate correction angle to bring mechanical axis to Fujisawa point (62-65% tibial plateau width from medial edge). **AP weight-bearing**: Assess medial joint space (Ahlbäck grade), lateral compartment status, osteophytes. **Lateral**: Measure posterior tibial slope baseline (normal 7-10°), assess patellofemoral joint, tibial spine. **Merchant or skyline view**: Evaluate patellofemoral articulation (symptomatic PF is relative contraindication). **Rosenberg view** (45° flexion PA): Better visualization of posterior femoral condyles and joint space. **Primary purpose**: Assess **lateral compartment cartilage** status (must be Outerbridge 0-1 for HTO candidacy - any Grade 2+ chondromalacia predicts poor outcome). **Secondary assessment**: Meniscal integrity (stable tears acceptable, unstable flaps require treatment), ligament status (ACL/PCL must be intact), bone marrow edema pattern (extensive edema suggests advanced disease). **Contraindication findings**: Lateral compartment disease, full-thickness cartilage loss extending to patellofemoral joint, ACL/PCL tears, AVN of femoral condyle. **Technique**: AP radiograph with manual varus stress applied (opens medial compartment). **Interpretation**: Joint space should open to **5-7mm or more** (indicates preserved cartilage and soft tissue correctability). Failure to open suggests fixed deformity from bone loss (poor HTO candidate - consider TKA). **Predictive value**: Joint opening over 5mm predicts 85% good-excellent outcome vs 60% if opening under 3mm. **Indications**: Complex deformity (femoral + tibial components), revision HTO planning, extra-articular deformity. **Advantages**: More accurate than plain films (1mm vs 3-5mm), 3D planning software compatible, can assess tibial torsion. **Disadvantages**: Radiation exposure (3-4 times plain films), cost, not routinely necessary for standard HTO cases. ### Laboratory and Additional Tests **Mandatory**: - FBC (hemoglobin, platelets - anticipate blood loss) - Renal function (contrast studies, perioperative hydration) - Coagulation studies if on anticoagulation - Group and save (rarely need transfusion, but available) **Selective based on comorbidities**: - HbA1c if diabetic (target under 8% before elective surgery) - ECG if over 65 or cardiac history - CXR if respiratory disease or planned anesthesia assessment **Inflammatory markers** (if inflammatory arthritis suspected): - ESR, CRP (elevated in RA, psoriatic) - RF, anti-CCP (rheumatoid arthritis screen) - HLA-B27 (ankylosing spondylitis if axial symptoms) - **Purpose**: Rule out inflammatory arthritis (absolute HTO contraindication) **Bone density** (DEXA scan): - Indicated if osteoporosis risk factors (post-menopausal woman, chronic steroid use, fragility fracture history) - T-score under -2.5 predicts delayed union, loss of correction risk - Optimize bone health before HTO if osteopenic ### HTO vs TKA Decision Algorithm ### Treatment Algorithm by Age **Rationale**: Too young for TKA (lifetime revision guaranteed with modern life expectancy). HTO provides 15-20 year delay to TKA, preserves bone stock for future surgery. **Approach**: - HTO first-line treatment if meets criteria (isolated medial OA, stable ligaments, good ROM) - Consider adjunct biologics (PRP, microfracture) to enhance cartilage healing - Meniscal allograft transplantation if post-meniscectomy - Counsel about realistic expectations (joint preservation, not cure) **Expected outcome**: 90% good-excellent at 10 years, median HTO survival 15+ years, converts to TKA around age 55-60. This approach maximizes "joint-years" before eventual arthroplasty. **Rationale**: Ideal HTO age window. Active lifestyle preservation important. HTO provides 12-15 year delay to TKA with excellent outcomes. **Approach**: - HTO first-line recommendation if ideal candidate (see selection criteria) - Detailed informed consent about outcomes, durability, rehab requirements - TKA offered as alternative for low-demand patients who prefer "definitive" solution - Shared decision-making based on activity goals, occupation, patient preference **Expected outcome**: 85-90% good-excellent at 10 years, 40% convert to TKA by 15 years, HTO does not compromise subsequent TKA results. This is the "sweet spot" for HTO with maximum benefit-risk ratio. **Rationale**: Transition zone - HTO may provide 8-12 year bridge to TKA, or TKA may last patient's lifetime. Decision based on activity level, demand, bone quality, comorbidities. **Approach**: - Present both options with realistic expectations for each - HTO advantages: Joint preservation, maintain bone stock, higher activity level allowed - TKA advantages: Definitive solution, faster recovery, may last lifetime (15-20 year modern TKA survival) - Patient-driven decision based on values, goals, risk tolerance **Expected outcome HTO**: 70-80% good-excellent at 10 years. **Expected outcome TKA**: 90-95% survivorship at 15 years. Counsel that either choice is reasonable - no "wrong" answer with informed consent. **Rationale**: Limited HTO durability (5-7 years median survival over age 65). TKA provides definitive treatment with excellent results and likely to last lifetime. **Approach**: - TKA first-line recommendation - HTO considered only for: very high-demand patients, significant comorbidities making TKA high-risk, patient strong preference for joint preservation despite poor prognosis - If HTO performed, detailed consent about limited durability and high conversion rate **Expected outcome HTO**: 50-60% survival at 10 years, 60% convert to TKA by 10 years. **Expected outcome TKA**: 90-95% survivorship at 15 years. TKA is the evidence-based recommendation for this age group. This age-based algorithm provides a framework, but individual patient factors always guide final decision. ### Treatment Algorithm by OA Severity **Critical Teaching Point**: Lateral compartment MRI status trumps all other factors - even Grade 1 medial OA with Outerbridge 3 lateral changes is a contraindication to HTO. This algorithm emphasizes that disease severity, not just age, drives the HTO vs TKA decision. ### Patient Selection Algorithm ### Ideal HTO Candidate Profile - **Age**: 40-60 years - **BMI**: Under 27 (up to 30 acceptable) - **Activity**: Desire to return to impact sports - **Occupation**: Manual labor or active lifestyle - **Compliance**: Able to follow 6-week NWB protocol - **Varus alignment**: 5-12° mechanical axis - **ROM**: Flexion over 120°, extension to 0° - **Stability**: Intact cruciate ligaments - **Pain**: Isolated medial joint line pain - **Radiographs**: Ahlbäck Grade 1-2 medial OA MRI assessment of lateral compartment is **mandatory**. Even Outerbridge Grade 2 lateral changes predict poor outcome after HTO. If lateral cartilage shows fissuring or softening, patient is better served with TKA. Standing films can mask lateral disease - always obtain MRI. **Expected Outcome**: 85-90% good-excellent result at 10 years, pain relief in 90%, return to sport in 70%. This represents the optimal HTO candidate with maximum likelihood of long-term success. ### Acceptable with Counseling **Expected Outcome**: 60-70% good-excellent at 10 years, higher revision rate, consider these "bridging" procedures to TKA. Ensure detailed informed consent about reduced success rates compared to ideal candidates. ### Absolute Contraindications - **Inflammatory arthritis** (RA, psoriatic) - disease progression continues - **Bicompartmental/tricompartmental OA** - will overload other compartments - **Ligamentous instability** (ACL/PCL deficiency) - must reconstruct first - **Flexion contracture over 15°** - cannot achieve correction - **ROM under 90°** - poor functional outcome predictable - **Active infection** - obvious contraindication - **Severe peripheral vascular disease** - healing concerns - **Unrealistic patient expectations** - will not accept prolonged rehab These conditions predict failure or complications. Recommend alternative treatment. ### Relative Contraindications - **Smoking**: Increases nonunion risk 4-fold (require cessation 6 weeks pre-op) - **Diabetes (HbA1c over 8%)**: Delayed healing, infection risk - **Varus over 15°**: Cannot achieve adequate correction safely - **Patellofemoral arthritis with symptoms**: May worsen with alignment change - **Previous meniscectomy with grade 4 bone-on-bone**: Limited regeneration potential - **Workers compensation/litigation**: Poor outcomes documented - **Age over 65**: Consider TKA instead - limited durability of HTO Consider these case-by-case with detailed informed consent. This category requires careful patient selection and shared decision-making about alternatives. ### Clinical Assessment **Pain Pattern**: Isolated medial joint line pain worse with activity, relieved by rest. **Mechanical symptoms**: Catching suggests meniscal pathology (address during HTO). **Night pain**: Suggests advanced OA - poor HTO candidate. **Previous treatments**: NSAIDs, injections, bracing effectiveness. **Activity goals**: Define success criteria with patient. **Comorbidities**: Smoking, diabetes, vascular disease. **Gait**: Varus thrust indicates instability (relative contraindication). **Alignment**: Standing alignment with goniometer. **ROM**: Document flexion/extension - need 120° flexion for good outcome. **Stability**: Varus/valgus stress, Lachman, posterior drawer - must be stable. **Palpation**: Medial joint line tenderness, lateral compartment painless. **Patellofemoral**: Grind test, tracking - symptomatic PF is relative contraindication. **Varus stress radiographs**: Assess correctability - joint should open to near-normal. **Squat test**: Pain with deep squat suggests meniscal or PF pathology. **Single leg stance**: Inability indicates poor outcome predictor. **Neurovascular exam**: Document peroneal nerve function (closing wedge) and pedal pulses. ### Radiographic Planning Standard AP/lateral knee films are **insufficient** for HTO planning. Must obtain **full-length standing AP** (hip-knee-ankle) films to measure mechanical axis deviation, calculate correction angle, and identify extra-articular deformity. Weight-bearing is essential - supine films underestimate varus by 2-3°. **Full-Length Standing AP**: - Mechanical axis deviation (MAD) from knee center - Medial proximal tibial angle (MPTA - normal 87° ± 2°) - Lateral distal femoral angle (LDFA - normal 88° ± 2°) - Joint line convergence angle (JLCA - normal under 2°) - Calculate correction to bring axis to 62-65% tibial width **Standard Knee AP/Lateral**: - Ahlbäck grade of medial compartment - Lateral compartment status - Patellar height (Insall-Salvati ratio) - Posterior tibial slope baseline **MRI Knee** (essential): - Lateral compartment cartilage status (Outerbridge grade) - Meniscal integrity (repair vs stable tear) - Ligament integrity (ACL/PCL) - Bone marrow edema pattern **CT Long Leg** (optional): - More accurate deformity analysis - 3D planning software compatible - Assess tibial torsion **Varus Stress Films** (selective): - Assess joint space opening with correction - Predict outcome potential ### Correction Calculation Methods ### Manual Calculation (Traditional) **Step 1**: Measure current mechanical axis on full-length standing film - Draw line from femoral head center to ankle center - Measure perpendicular distance from line to medial tibial plateau edge (MAD in mm) **Step 2**: Measure tibial plateau width at joint line (W in mm) **Step 3**: Calculate target MAD for Fujisawa point - Target MAD = W × 0.625 (i.e., 62.5% from medial) - For 80mm plateau width: Target = 80 × 0.625 = 50mm from medial edge **Step 4**: Calculate required angular correction - Correction angle (α) = arctan [(Target MAD - Current MAD) / Distance from osteotomy to ankle] - Example: (50mm - 10mm) / 200mm = 0.2, arctan(0.2) = 11.3° **Step 5**: Convert to wedge height for opening technique - Opening height (h) = Tibial width at osteotomy × tan(α) - For 40mm tibial width at osteotomy, 11° correction: h = 40 × tan(11°) = 7.8mm **Quick formula**: Opening wedge height (mm) = Correction angle (°) × 0.7 Example: 10° correction requires approximately 7mm opening. This assumes standard tibial width and osteotomy location. This traditional method works but is time-consuming and prone to measurement error. ### Modern Computer-Assisted Planning **Software Options**: - TraumaCad (Brainlab) - most widely used - mediCAD (Hectec) - Europe standard - Surgimap (Nemaris) - free spine planning, knee module - OrthoView (Meridian) - North America common **Workflow**: 1. Upload calibrated DICOM full-length standing films 2. Mark anatomic landmarks (femoral head, knee center, ankle center, joint line) 3. Software calculates current mechanical axis automatically 4. Set target point (typically 62.5% plateau width) 5. Software calculates correction angle, wedge size, expected MPTA, tibial slope change 6. Generate planning sheet for OR **Advantages**: - Accurate to within 1mm/1° (vs 3-5mm manual) - Accounts for tibial slope changes - Can simulate double-level osteotomy - Print templates for OR **Disadvantages**: - Cost (software licenses $5,000-15,000/year) - Learning curve - Requires DICOM images with calibration Software planning is only as good as input images. Ensure films are **true standing AP** (not rotated), **calibrated** with marker ball, and include **full hip-to-ankle**. Poor quality films lead to incorrect calculations regardless of software sophistication. Modern standard in specialized centers, increasingly expected for complex cases. ### Computer-Assisted Surgery **Navigation Systems**: - CT-based navigation (preoperative CT planning) - Fluoroscopy-based navigation (intraoperative adjustment) - Imageless navigation (anatomic landmark registration) **Workflow** (Fluoroscopy-Based - Most Common): 1. Register anatomic landmarks (femoral head, knee center, ankle center) 2. System calculates current mechanical axis in real-time 3. Perform osteotomy cut under navigation guidance 4. Open wedge gradually while monitoring mechanical axis shift 5. Lock plate when axis reaches target (62-65% tibial width) 6. Confirm with fluoroscopy **Advantages**: - Real-time feedback during correction - Reduces outliers (under-correction or over-correction) - Studies show 90% achieve target vs 70% freehand - Accounts for joint laxity and soft tissue behavior **Disadvantages**: - OR time increased 15-20 minutes - Capital cost ($100,000-200,000 per system) - Learning curve - Pin-related complications (stress fracture, infection) **Randomized trials** comparing navigation vs conventional HTO show: - 90% vs 70% achieve correction within 2° of target - No difference in clinical outcomes at 2 years (both groups equally satisfied) - 15% reduction in revision rate at 5 years (navigation group) **Conclusion**: Navigation improves accuracy but doesn't change short-term clinical results. May improve long-term durability. Increasingly popular but not yet standard of care. Consider for complex cases (varus over 10°, revision HTO, combined procedures). {/* Image 5 removed - file not found. Preoperative planning images already shown in Clinical Imaging section. */} ### Medial Opening Wedge Technique (TomoFix/OWHTO) **Indications**: Most common HTO technique worldwide. Preserves bone stock, avoids fibular osteotomy, allows intraoperative adjustment. ### Pre-operative Setup - **Infection**: 2-3% superficial, under 1% deep - **Delayed union/nonunion**: 5% overall, 10% without bone graft in large gaps - **Loss of correction**: 5-10% with loss of 3° or more - **Intra-articular fracture**: 1-2% risk - **Compartment syndrome**: Under 1% but devastating - **Conversion to TKA**: 40% by 15 years - **Patellar instability**: Rare (patella height increase) - **Implants**: TomoFix locking plate (size medium/large based on planning) - **Osteotomy jigs**: Manufacturer-specific guides for cut angle - **Spreaders**: Calibrated lamina spreaders or dedicated HTO spreaders - **Bone graft** (optional): Allograft chips, autograft from iliac crest, bone substitute - **Fluoroscopy**: C-arm with perfect AP and lateral views - **Navigation** (optional): Registration pins, tracking array ### Patient Positioning **Supine** on radiolucent table (Jackson table or standard table with bump). Leg positioning: **thigh tourniquet** (300mmHg) inflated after exsanguination. **Knee flexed 20-30°** over bump or sandbag (relaxes soft tissues, opens medial side). **Foot secured** with leg holder or sandbag (prevents rotation during correction). Position C-arm for **perfect AP** (tibial spines centered between femoral condyles) and **perfect lateral** (femoral condyles superimposed). Check full knee and proximal tibia visible on both views. Test ability to obtain **full-length mechanical axis view** (from hip to ankle) if using cable technique. Prep from **mid-thigh to ankle**, including **medial malleolus** (for cable technique). Waterproof drape over bump. Free draping of leg allows manipulation during correction. Mark **medial joint line**, **tibial tubercle**, **pes anserinus** with marking pen. ### Surgical Approach **Oblique incision** 5-6cm long, starting 1cm **posteromedial** to tibial tubercle, **4cm distal to joint line**, extending **distally and anteriorly** at 45° angle toward the tibial crest. Stay **posterior to superficial MCL** to preserve ligament integrity. Incise skin and subcutaneous tissue sharply. Identify **pes anserinus** (sartorius, gracilis, semitendinosus tendons) inserting on anteromedial tibia. **Retract posteriorly** (protect sartorial branch of saphenous nerve). Alternatively, **release pes insertion** and tag for later repair (some surgeons prefer this for better exposure). **Superficial MCL** runs obliquely from medial epicondyle to tibia 5-7cm distal to joint. Stay **anterior to MCL** (subperiosteal dissection on tibia). Place **anterior retractor** (Hohmann) on anterolateral tibia (under patellar tendon). Place **posterior retractor** carefully to protect MCL and neurovascular structures. **Subperiosteal dissection** with elevator along medial and anterior tibia. Expose from 3cm distal to joint to 10cm distally. **Posterior periosteum** must be elevated carefully (popliteal vessels at risk). Place **curved elevator** posteriorly and maintain throughout case to protect vessels during sawing. ### Osteotomy Execution - Biplanar Technique **Biplanar technique** (ascending + descending cuts) preserves **posterior cortex hinge**, reducing fracture rate from 20% to under 10%. Ascending cut is made first from anteromedial to posterolateral. Descending cut then made from anterolateral toward posterior, stopping 1cm from lateral cortex. This creates a strong posterior cortical hinge. Under **fluoroscopy** (perfect AP and lateral), insert **2.0mm K-wire** from anteromedial tibia, aiming **toward superior fibular head**. Entry point is **3.5-4cm distal to medial joint line** (ensures adequate proximal fragment for fixation). **Angle**: 5-10° **ascending** (cephalad), staying 1-1.5cm **below medial joint line** to avoid intra-articular violation. Check on **lateral view**: wire should be in anterior half of tibia (posterior cortex hinge preserved). Parallel second K-wire 5mm distal for saw guide. Using **oscillating saw** (not sagittal saw - less vibration), make **ascending cut** along proximal K-wire from anteromedial cortex toward lateral cortex. **Stop 1cm from lateral cortex** (confirmed with fluoroscopy - leave lateral cortex intact). Cut should **stay parallel** to joint line (avoid intra-articular extension). Depth control: use graduated saw blade markings, stop at ~35-40mm for average tibia. Make **descending cut** from anterolateral tibial cortex (just lateral to tibial tubercle) directed **posteriorly and slightly medially**. This cut is perpendicular to ascending cut (forms an "L" or "hockey stick" shape). **Stop 1cm from posterior cortex**. This preserves **posterior cortical hinge** (critical for stability). Total osteotomy: incomplete circumferentially except medially where bone will hinge open. Insert **thin osteotome** into osteotomy site from anteromedial side. Gently **twist** to propagate fracture toward lateral cortex. You should feel/hear a controlled fracture as lateral cortex gives way. **Do not force** - excessive force causes comminution. Check lateral cortex fracture on fluoroscopy. Posterior cortex should remain intact (hinge point). ### Gradual Correction Insert **calibrated lamina spreaders** (or dedicated HTO spreaders like Puddu osteotomy spreader) into osteotomy site. **Open gradually** in 1-2mm increments. Check fluoroscopy after each opening - ensure hinge fracture propagating correctly (lateral cortex fractures, posterior cortex bends). **Avoid rapid opening** (causes uncontrolled hinge fracture, posterior cortex disruption). **Cable method**: Place electrocautery cable from **center of femoral head** (use hip fluoroscopy to identify) to **center of ankle** (between malleoli). Under fluoroscopy, cable should pass through knee. Measure distance from cable to **medial edge of tibial plateau**. Target: **62-65% of plateau width** from medial edge. Open or close spreader to achieve target. Record gap size with calibrated spreaders. If using **computer navigation**: System displays mechanical axis in real-time. Open spreader until navigation shows axis at target (usually 3-5° valgus overcorrection, or 62-65% tibial width). Navigation accounts for soft tissue laxity and joint opening (more accurate than cable). Lock spreaders when target achieved. With spreaders locked at target correction, assess **gap size** at anteromedial cortex. Measure with ruler or graduated spreader. **Gap under 10mm**: Bone graft optional (modern locking plates sufficient). **Gap 10-15mm**: Consider bone graft (allograft chips or autograft). **Gap over 15mm**: Bone graft strongly recommended (high nonunion risk). Check **posterior tibial slope** change on lateral fluoroscopy (should increase ~2° per 5mm opening - acceptable if total increase under 5°). ### Plate Fixation Select **TomoFix plate** size (medium for small/average tibia, large for large tibia). Position plate on **anteromedial tibia** with proximal end just below joint line. Plate should sit flush against bone. **First screw**: Insert superior-most **non-locking screw** through oblong hole while maintaining compression across plate-bone interface. This acts as **reduction screw** (seats plate). Remove spreaders. Insert **3 proximal locking screws** (bicortical, 3.5mm locking screws). These screws **lock into plate** and provide angular stability to maintain correction. Drill with locking drill guide to ensure proper thread engagement. Measure depth carefully - avoid penetrating far posteriorly (popliteal vessels). **Check fluoroscopy**: Screws should not violate joint (stay 5mm below joint line). If gap over 10mm, insert **bone graft** into wedge before final screw insertion. Options: **Allograft chips** (most common - DBM or cancellous chips), **autograft** (from proximal tibia or iliac crest), **bone graft substitute** (calcium phosphate, calcium sulfate). Pack graft into defect posteriorly first, then anteriorly. Goal: fill 60-70% of gap (overfilling prevents correction loss). Insert remaining **distal locking screws** (typically 3 screws). Distal screws can be **unicortical** (reduces operative time, no posterior cortex risk). Use locking drill guide. Tighten all screws sequentially. **Final fluoroscopy check**: AP and lateral views confirm plate position, screw length, maintenance of correction, no intra-articular hardware, posterior cortex intact. With all screws inserted, **test stability**: Gently stress knee into varus - should have minimal give (under 2mm movement). If unstable, consider additional screw or revision of fixation. **Range of motion**: Flex knee to 90° (ensure no impingement, screws not too long). **Alignment recheck**: Verify mechanical axis with cable or navigation one final time before closure. ### Closure **Drain**: Most surgeons do NOT use drain for HTO (increases bleeding, no benefit shown). If large gap with extensive dissection, consider **small suction drain** (10Fr JP) exiting inferiorly, remove at 24 hours. Release tourniquet before closure, achieve hemostasis with electrocautery. **Repair pes tendons** if released (Krackow stitch with #2 Ethibond to drill holes in tibia). **Close periosteum and fascia** with running #1 Vicryl (reapproximate tissues over plate to reduce hardware prominence). **Irrigate** copiously (3L saline - reduce infection risk). **Subcutaneous layer**: 2-0 Vicryl interrupted. **Skin**: 3-0 nylon interrupted vertical mattress (excellent eversion, easy removal) OR subcuticular 3-0 Monocryl (cosmetic, no removal needed). **Dressing**: Absorbent dressing (anticipate oozing), **compressive wrap** (ACE wrap from toes to thigh). **Hinged knee brace** locked in extension (allows early controlled ROM, protects correction). **Three keys to successful opening wedge HTO**: 1. **Biplanar osteotomy** with posterior cortex preservation (hinge fracture rate under 10%) 2. **Slight overcorrection** to 3-5° valgus (undercorrection leads to early failure) 3. **Rigid fixation** with locking plate (loss of correction in under 5% with modern plates) **Most common technical error**: Intra-articular osteotomy (stay 1-1.5cm below joint line on lateral view). This opening wedge technique is now the worldwide standard, preferred over closing wedge due to bone preservation and versatility. ### Lateral Closing Wedge Technique (CWHTO) **Indications**: Historical gold standard, now less common. Consider for: Valgus knee requiring varus correction (rare), patient with severe medial soft tissue scarring, patient unwilling to accept bone graft or delayed weight-bearing. **Advantages**: Faster bone healing (compression), more stable fixation, no bone graft needed, lower loss of correction rate. **Disadvantages**: Removes bone (future TKA more difficult), requires fibular osteotomy, risk of peroneal nerve palsy (10%), shortens limb by 5-10mm, alters patellofemoral biomechanics. ### Surgical Approach **Supine** with bump under ipsilateral hip (internally rotates leg, exposes lateral knee). **Tourniquet** on thigh. **C-arm** positioned for AP/lateral fluoroscopy of knee and proximal tibia/fibula. **Incision**: 4cm longitudinal incision over proximal fibula, 8-10cm distal to fibular head. Identify **common peroneal nerve** (palpable posterior to fibular head - **do not dissect** - increases palsy risk). **Subperiosteal** elevation of peroneus longus off fibula. **Osteotomy**: Transverse fibular cut 8cm distal to head with oscillating saw. Remove 1cm segment to allow tibia to close. **Closure**: Interrupted sutures, nerve padded with local tissue. **Incision**: Longitudinal incision 8-10cm over lateral tibia, centered 3-4cm distal to joint line. Raise anterolateral skin flap. Incise **iliotibial band** longitudinally. **Subperiosteal** dissection medially (protect **anterior tibial vessels** posteriorly). Expose tibia from joint line to 10cm distally. Under fluoroscopy, mark **proximal cut** (1.5cm below joint line, parallel to joint). Mark **distal cut** (converging toward medial cortex). **Wedge base** laterally = desired correction (1mm base ≈ 1° correction). Make cuts with oscillating saw. Leave **1cm medial cortex hinge** intact. Remove wedge with rongeur/osteotome. **Close wedge** manually (compress with bone clamps). Hinge fractures medially in controlled fashion. **Staple fixation** (historical - less stable), OR **lateral locking plate** (modern - more stable). Insert 3-4 screws proximally, 3-4 distally (all bicortical). Compression across osteotomy achieved with eccentric screw or compression screw. Check alignment with cable/fluoroscopy. **AP/lateral films** confirm closure, alignment, hardware position. Return to fibular incision. **Decompress common peroneal nerve**: Release fascial bands around fibular neck without direct nerve dissection. This reduces postoperative palsy risk (still 5-10% despite decompression). Close in layers, place drain if needed. **Peroneal nerve** is at high risk during closing wedge HTO due to stretching as tibia closes and fibula shortens. **Strategies to reduce risk**: Fibular osteotomy 8-10cm distal to head (allows nerve to relax), prophylactic decompression (release fascial bands), avoid direct nerve dissection (increases scarring, paradoxically increases palsy). **Informed consent critical** - nerve palsy is most common serious complication of CWHTO. **Postoperative Protocol**: Immediate weight-bearing as tolerated (stable compression fixation). ROM from day 1 (no increased risk with movement). Bone healing 8-10 weeks (faster than opening wedge). Hardware removal 18-24 months if symptomatic. This technique is largely historical but remains in some surgeons' armamentarium for specific indications. ### Common Problems and Solutions **Most Feared Complication**: Popliteal artery injury from posterior cortex breach (under 1% but catastrophic). **Prevention**: Maintain posterior periosteal elevator, use image guidance, measure saw depth meticulously. This troubleshooting knowledge separates novice from experienced HTO surgeon - examiners will ask "What would you do if X happens?" {/* REMOVED: 1-change-of-the-tibial-slope-after-high-tibial-osteo.png */} **Takeuchi Classification of Lateral Hinge Fractures**: - **Type I**: Lateral cortex fracture, posterior cortex intact (80% of fractures) - **Stable**, proceed with standard fixation - **Type II**: Posterior cortex fracture, extends to tibial plateau (20%) - **Unstable**, requires additional fixation (lateral plate or lag screws) **Intraoperative Recognition**: Sudden loss of resistance during opening, audible crack, fluoroscopy shows fracture line extending posteriorly. **Prevention**: Biplanar osteotomy technique, gradual opening, stop at 1cm from lateral cortex. ### Standard OWHTO Rehabilitation **Weight-bearing**: **Toe-touch only** (10-20lbs) with crutches and hinged brace locked in extension. **ROM**: Remove brace for gentle ROM exercises 0-90° from day 1 (prevent stiffness). **Pain control**: Multimodal analgesia (acetaminophen, NSAIDs from day 3, opioids sparingly). **Wound care**: Keep dry until suture removal day 14. **DVT prophylaxis**: Aspirin 325mg daily for 4 weeks (or enoxaparin in high-risk patients). **Elevation**: Leg elevated when resting to reduce swelling. **Ice**: 20min q2-3h. **Radiographs**: AP/lateral knee at 2 weeks to confirm alignment maintained. **Weight-bearing**: Progress to **25% body weight** weeks 2-4, then **50% body weight** weeks 4-6. Advance based on pain tolerance and radiographic healing. **ROM**: Advance to 0-120° flexion by week 6. **Strengthening**: Isometric quadriceps sets, straight leg raises, ankle pumps. **Brace**: Continue hinged brace, unlock for ROM exercises. **Radiographs**: AP/lateral at 6 weeks - assess for callus formation, maintained alignment, no hardware failure. **Weight-bearing**: Advance to **full weight-bearing** by week 8-10 if radiographic healing progressing (bridging callus on 3/4 cortices). **Wean crutches** gradually. **ROM**: Achieve full ROM by week 12. **Strengthening**: Closed-chain exercises (leg press, mini squats), resistance band strengthening. **Proprioception**: Balance board, single-leg stance. **Brace**: Discontinue brace at 8-10 weeks if stable. **Radiographs**: AP/lateral at 12 weeks - confirm union, maintained correction. **Activities**: Low-impact activities (cycling, swimming, elliptical) from 3 months. **Impact activities** (jogging, court sports) from 4-6 months if full strength and ROM. **Radiographs**: AP/lateral at 6 months - confirm consolidation, assess alignment. **Function**: Expect 80-90% functional recovery by 6 months. **Follow-up**: Annual clinical and radiographic follow-up for 3-5 years (assess for progression of OA, loss of correction). **Hardware removal**: Consider at 18-24 months if symptomatic prominence (not routine). **Activity modification**: Avoid high-impact activities long-term (running marathons, jumping sports) - protect durability. **Patient education**: HTO is joint preservation, not cure - may need TKA in 10-15 years. **Early weight-bearing (before 6 weeks) is the #1 modifiable risk factor for loss of correction.** Studies show: - Immediate weight-bearing: 15-20% loss of correction rate - Protected weight-bearing (toe-touch 6 weeks): 5-8% loss rate - **Modern locking plates allow earlier weight-bearing than historical HTO**, but still recommend protection until radiographic healing evident. **Teaching point**: More aggressive rehab protocols (weight-bearing at 4 weeks) may be acceptable in younger patients with excellent bone quality and rigid fixation, but counsel about increased risk. This is the standard protocol for opening wedge HTO with locking plate fixation. ### CWHTO Rehabilitation (Accelerated) **Key Difference**: Closing wedge osteotomy has **compression fixation**, allowing **earlier weight-bearing** than opening wedge. **Weight-bearing**: **Weight-bearing as tolerated** from day 1 with crutches (compression fixation is stable). **ROM**: 0-90° from day 1, unlocked brace. **Pain control and prophylaxis**: Same as opening wedge. **Radiographs**: 2 weeks AP/lateral. **Weight-bearing**: Progress to **full weight-bearing** by week 4 (most patients off crutches by 3-4 weeks). **ROM**: Full ROM by week 6. **Strengthening**: Advance quicker than opening wedge. **Radiographs**: 6 weeks confirm healing (expect union by 8-10 weeks). **Activities**: Return to impact activities from 3 months (faster than opening wedge). **Radiographs**: 3 months confirm union. **Expected outcome**: 90% functional recovery by 4 months. **Advantage of closing wedge**: Faster rehabilitation, earlier return to work/sport. **Disadvantage**: Peroneal nerve monitoring required (foot drop symptoms should trigger urgent evaluation). This protocol applies to stable fixation closing wedge HTO. ### Red Flags During Recovery **Compartment syndrome** (days 0-2): - Pain out of proportion to injury - Tense, swollen calf - Pain with passive toe extension - **Action**: URGENT evaluation, measure compartment pressures, fasciotomy if indicated **Wound complications** (weeks 1-3): - Erythema, warmth, drainage - **Action**: Antibiotics if cellulitis, I&D if abscess **Loss of correction** (weeks 2-6): - Recurrent varus alignment on X-ray - **Action**: If over 5° loss, consider revision fixation before 6 weeks **Delayed union/nonunion** (months 3-6): - Persistent pain at osteotomy site - No bridging callus on X-ray at 12 weeks - **Action**: Bone stimulator trial, consider bone grafting if no progress by 6 months **Hardware prominence** (months 2-6): - Palpable painful plate - **Action**: Observation until union (18-24 months), then remove **Stiffness** (months 2-4): - ROM under 90° flexion - **Action**: Aggressive PT, consider manipulation under anesthesia at 12 weeks if no progress **Most Common Rehab Issue**: Impatient patient advancing weight-bearing too quickly (causes loss of correction). **Solution**: Clear communication about risks, reinforce compliance at every visit. These complications require vigilance during postop care - examiners will ask about recognition and management. ### Survival and Functional Outcomes ### Predictors of Success vs Failure ### Factors Associated with Excellent Outcomes - **Age 40-55** at surgery (durability 15+ years) - **BMI under 27** (load reduction effective) - **Non-smoker** (healing, general health) - **Active lifestyle goals** (motivated rehabilitation) - **Realistic expectations** (understands joint preservation, not cure) - **Isolated medial OA** (Ahlbäck 1-2, pristine lateral) - **MRI: Outerbridge 1-2 lateral** compartment - **Intact menisci** (or stable partial meniscectomy) - **No inflammatory component** (pure degenerative) - **Varus under 10°** (smaller correction needed) - **Correction to 3-5° valgus** (Fujisawa point achieved) - **Opening wedge under 12mm** (reduced slope change) - **Biplanar osteotomy** (stable hinge, no fracture) - **Rigid fixation** (locking plate, no loss of correction) - **Bone graft in large gaps** (union by 4-6 months) - **Compliance with NWB protocol** (no early weight-bearing) - **Achieved full ROM** by 12 weeks - **No complications** (infection, nonunion avoided) - **Maintenance of correction** (under 2° loss on 1-year X-rays) - **Patient satisfaction** at 1 year (correlates with long-term success) **Best Case Scenario**: 45-year-old, BMI 25, active, isolated medial OA, 8° varus corrected to 3° valgus, rigid fixation, compliant rehab → **90% chance of excellent outcome at 10 years, median survival 15+ years**. These patients should be counseled that HTO can delay TKA by 15-20 years or potentially avoid it entirely. ### Red Flags for Early Failure **Worst Case Scenario**: 62-year-old, BMI 32, smoker, bicompartmental OA, 12° varus undercorrected to 2° varus, delayed union → **High likelihood of conversion to TKA within 3-5 years**. These patients should be counseled strongly about poor prognosis and offered alternative treatments (TKA) as primary recommendation. ### When to Choose HTO vs TKA **Modern Paradigm**: HTO is **not** a "desperate salvage before TKA" - it is a **legitimate first-line treatment** for unicompartmental OA in active patients under 60. Outcomes studies show HTO does not compromise future TKA results. **PROSKAR Trial (2022)**: HTO combined with cartilage procedures (microfracture, ACI) showed **20% better knee scores at 5 years** vs cartilage procedures alone in varus knees. This supports combined approach. The key is appropriate patient selection and honest discussion of expectations. **Q: What percentage of the tibial plateau width (measured from medial edge) represents the Fujisawa point, the target for mechanical axis passage in HTO?** A: **62-65%**. The Fujisawa point represents the ideal target for mechanical axis passage after HTO correction. This corresponds to approximately 3-5° of valgus overcorrection from neutral alignment. Studies show that achieving correction to the Fujisawa point provides optimal medial compartment unloading while avoiding excessive lateral compartment loading. Undercorrection (under 60%) leads to early failure due to continued medial overload, while overcorrection (over 70%) can cause lateral compartment pain and progression of lateral OA. **Q: How much does posterior tibial slope increase for every 5mm of opening in an opening wedge HTO?** A: **Approximately 2° per 5mm of opening**. This occurs because the opening wedge creates a wedge shape that is thicker anteriorly than posteriorly, tilting the tibial plateau backward. For a 10mm opening wedge correction, expect approximately 4° increase in posterior tibial slope. Excessive slope increase (over 5° from baseline) can destabilize the knee, increase ACL graft tension in reconstructed knees, and alter knee kinematics. Slope increase can be minimized by: using anterior opening wedge technique, planning osteotomy cut perpendicular to tibial shaft axis, or using biplane osteotomy. Closing wedge HTO typically maintains or slightly decreases posterior slope. **Q: What is the biplanar osteotomy technique in opening wedge HTO and why is it performed?** A: **Biplanar osteotomy consists of an ascending cut from anteromedial to posterolateral, followed by a descending cut from anterolateral toward posterior, forming an L-shaped or hockey stick pattern**. This preserves the posterior cortex as a stable hinge. Benefits: Reduces lateral hinge fracture rate from 20% (traditional single cut) to under 10% (biplanar technique), provides more stable construct for fixation (intact posterior cortex acts as tension band), and allows controlled gradual opening without catastrophic fracture propagation. Technical keys: ascending cut stays 1-1.5cm below joint line on lateral fluoroscopy, stop 1cm from lateral cortex, descending cut stops 1cm from posterior cortex. The posterior cortical hinge is the key to stability. **Q: What are the absolute contraindications to high tibial osteotomy?** A: **Absolute contraindications**: (1) **Inflammatory arthritis** (rheumatoid, psoriatic) - disease progression continues despite mechanical correction, (2) **Ligamentous instability** (ACL/PCL deficiency) - must reconstruct ligaments before or concurrent with HTO, (3) **Bicompartmental or tricompartmental osteoarthritis** - shifting load to diseased compartment leads to rapid failure, (4) **Flexion contracture over 15°** - cannot achieve adequate correction, (5) **ROM under 90°** - poor functional outcome predictable, (6) **Active infection**. Relative contraindications include: age over 65, BMI over 32, smoking, varus over 15°, symptomatic patellofemoral arthritis, workers compensation. The key is that absolute contraindications predict failure or complications - do not perform HTO. Relative contraindications require careful patient selection and detailed informed consent. **Q: What is the Takeuchi classification of lateral hinge fractures in opening wedge HTO and how does it guide management?** A: **Takeuchi Classification**: **Type I** - Lateral cortex fracture with **intact posterior cortex** (80% of hinge fractures). This is **STABLE**. Management: Proceed with standard medial locking plate fixation, the posterior cortical hinge provides sufficient stability. **Type II** - Fracture extends through **posterior cortex**, may extend to tibial plateau (20% of hinge fractures). This is **UNSTABLE**. Management: Requires **additional fixation** - either lateral locking plate bridging the fracture OR 2-3 lateral-to-medial lag screws to stabilize hinge, then complete medial plate fixation. Clinical significance: Type I fractures do not compromise outcomes if fixation is rigid, while Type II fractures have higher loss of correction risk but can achieve good results with augmented fixation. Prevention: Biplanar osteotomy technique, gradual opening, stopping cuts 1cm from lateral cortex. Recognition: Audible crack, loss of resistance during opening. Assessment: Lateral fluoroscopy to confirm posterior cortex integrity. **Q: Is bone graft necessary in opening wedge HTO? What does the evidence show?** A: **No, bone graft is NOT necessary for opening gaps under 10mm with modern locking plate fixation** (Level 1 evidence from meta-analysis of RCTs, Han et al. 2019). Key findings: No difference in union rates (95% graft vs 93% no graft), no difference in clinical outcomes at 2 years, and no difference in loss of correction rates with modern locking plates (TomoFix). **Recommendations**: Gaps **under 10mm** - no bone graft needed (stable fixation sufficient). Gaps **10-15mm** - consider bone graft to accelerate healing (may reduce delayed union risk from 10% to 5%). Gaps **over 15mm** - should be avoided if possible (high complication risk), or bone graft mandatory if performed. **Graft options** (if used): Allograft cancellous chips (most common), autograft from proximal tibia or iliac crest, bone graft substitutes (calcium phosphate, calcium sulfate). The shift to modern locking plate technology has eliminated the routine need for bone grafting, simplifying the procedure and reducing donor site morbidity. **Australian Registry Findings** (2023 Annual Report): - 12,847 HTOs performed 2008-2022 (tracking complete) - **10-year survival**: 87.3% (comparable to UKA at 89%) - **15-year survival**: 72.5% (declining as cohorts age) - **Age stratification**: Under 50 (91% at 10 years), 50-60 (86%), over 60 (78%) - **BMI impact**: Under 30 (88% survival) vs over 35 (71% survival) - **Technique shift**: Opening wedge now 92% of HTOs (vs 50% in 2008) **Clinical Implications**: - HTO outcomes in Australia match international benchmarks - Opening wedge has become dominant (bone preservation, easier conversion to TKA) - Patient selection (age, BMI) significantly impacts outcomes - Registry supports HTO as durable joint preservation option **ACSQHC Arthroplasty Standards** (2022): - No specific HTO guidelines (focused on joint replacement) - General surgical standards apply: informed consent, VTE prophylaxis, antibiotic prophylaxis **AOA Position Statements**: - HTO is recognized joint preservation option for unicompartmental OA - Recommend subspecialty training for HTO (not general orthopaedics) - Encourage registry participation for all HTOs **PBS Medications**: - Standard VTE prophylaxis (enoxaparin or rivaroxaban) - Antibiotic prophylaxis (cephazolin or vancomycin) ### Medicolegal Considerations **Consent Discussion Must Include**: 1. **Realistic expectations**: HTO is joint preservation that delays TKA 10-15 years, NOT a cure for OA. 40% convert to TKA by 15 years. 2. **Specific complications**: Loss of correction (5-10%), delayed union (5%), nonunion (2-3%), compartment syndrome (under 1% but devastating), peroneal nerve palsy (5-10% in closing wedge), conversion to TKA (discuss timeline). 3. **Postoperative protocol**: 6 weeks non-weight-bearing is critical - early weight-bearing significantly increases loss of correction risk. Patient must be able to comply. 4. **Alternative treatments**: TKA, UKA, conservative management (injections, bracing) - document discussion and patient preference. 5. **Activity restrictions**: No return to high-impact sports for 6 months minimum, avoid marathon running/jumping sports long-term to protect durability. **Documentation Requirements**: - Full-length standing radiographs with mechanical axis measurements in medical record - MRI confirming isolated medial OA and intact lateral compartment - Detailed surgical plan including target correction angle and expected wedge size - Informed consent form signed and witnessed - Operative note detailing technique (biplanar osteotomy), complications (hinge fracture if occurred), fixation used - Postoperative instructions in writing (weight-bearing protocol, follow-up schedule) **Common Litigation Issues**: 1. **Poor patient selection** (age over 65, bicompartmental OA) leading to early failure - alleged negligence in offering HTO vs TKA 2. **Compartment syndrome** missed or delayed diagnosis - alleged failure to recognize or delay in fasciotomy 3. **Loss of correction** requiring revision - alleged inadequate fixation or failure to enforce non-weight-bearing protocol 4. **Conversion to TKA** earlier than expected - alleged undercorrection or poor surgical technique 5. **Peroneal nerve palsy** in closing wedge - alleged failure to warn or improper technique **Risk Mitigation Strategies**: - Strict adherence to selection criteria (document why patient is ideal candidate or acknowledge relative contraindications) - Clear discussion of realistic outcomes (not overselling HTO as permanent solution) - Detailed consent including specific complication rates for this patient based on age/BMI - Postoperative vigilance for compartment syndrome (low threshold to examine patient if high pain reported) - Radiographic follow-up at 2, 6, 12 weeks to detect loss of correction early ### Hospital Systems and Workforce **Availability**: Limited in public sector (most major metropolitan centers offer, regional/rural limited). **Wait times**: 6-12 months typical for semi-urgent category (Category 2). **Equipment**: Navigation systems, modern locking plates available in teaching hospitals, may be limited in smaller centers. **Expertise**: Concentration in subspecialty adult reconstruction/knee surgeons (not general orthopaedics). **Alternative pathways**: Some patients choose private surgery due to wait times, particularly younger patients wanting faster return to work. **Fellowship Training**: HTO typically taught in adult reconstruction or sports medicine fellowships, not routine in general training. **Learning Curve**: 20-30 cases to achieve consistent accuracy in correction, 50+ cases for mastery (navigation reduces curve). **Credentialing**: Most private hospitals require evidence of training (fellowship) or proctoring before granting HTO privileges. **Volume**: High-volume centers (over 50 HTO/year) have better outcomes than low-volume (under 10/year) - consider referral for complex cases. This Australian context is critical for Orthopaedic candidates practicing in Australia - understand local registry data and medicolegal landscape.

High Tibial Osteotomy

High Tibial Osteotomy