import { ComparisonTable, ContentSection, EvidenceCard, ExamCheatSheet, ExamPearl, ExamWarning, InfoCard, InfoCardGrid, MedicalImage, MnemonicCard, OnePagerSummary, SafetyAlert, Tab, Tabs, Timeline, TimelineItem, VivaScenario, VivaScenarioSection } from '@/components/mdx' **Valgus thrust gait with lateral compartment pain**. Young patients (under 60), BMI less than 30, high activity demand. Failed conservative management. Isolated lateral compartment disease on imaging. Correctable deformity (not fixed flexion contracture greater than 15 degrees). **Critical for surgical planning**. Intersection of proximal and distal mechanical axes. Usually at metaphyseal-diaphyseal junction. Osteotomy must be at CORA level. Misplacement creates translation deformity. **Opening wedge preferred over closing**. Use lateral distal femoral locking plate. Protect common peroneal nerve. Fill wedge gap greater than 10mm with bone graft or substitute. Check correction with intraoperative imaging. **Peroneal nerve palsy most feared**. Delayed union or nonunion at osteotomy site. Loss of correction. Patella alta requiring later patella tendon shortening. Conversion to arthroplasty in 15-20% at 10 years. Distal femoral osteotomy addresses **valgus knee malalignment** causing lateral compartment overload. While less common than varus deformity (treated with high tibial osteotomy), valgus deformity creates unique challenges: lateral soft tissue laxity, peroneal nerve proximity, and frequent associated LCL or posterolateral corner insufficiency. The surgery aims to realign the mechanical axis, reducing lateral compartment load and delaying or avoiding total knee arthroplasty in young, active patients. - **Age**: 40-60 years (too young for TKA) - **Activity level**: High demand, athletic - **Gender**: Females greater than males (constitutional valgus) - **BMI**: Ideally less than 30 for optimal outcomes - **Failed conservative care**: Bracing, injections, activity modification - **Mechanical overload**: Valgus alignment shifts load laterally - **Cartilage degeneration**: Lateral compartment wear, bone-on-bone - **Soft tissue laxity**: Medial structures stretched, lateral contracted - **Thrust gait**: Dynamic valgus increases with ambulation - **Progressive**: Deformity worsens without intervention The **Center of Rotation and Angulation (CORA)** is where the proximal mechanical axis and distal mechanical axis intersect. The osteotomy MUST be performed at the CORA level. If the osteotomy is placed away from CORA, the correction creates an undesirable **translation deformity**. For valgus knee, CORA is typically at the distal femoral metaphysis. - **Definition**: Mechanical axis at 62% from medial tibial edge - **Clinical significance**: Optimal load distribution - **Measurement**: On standing long-leg radiograph - **Overcorrection rationale**: Shifts load to healthier medial compartment - **Evidence**: Fujisawa 1979 study showed best outcomes at this point - **Long-leg standing films**: Essential for planning - **Draw mechanical axes**: Hip center to ankle center - **Identify intersection**: Where axes cross = CORA - **Measure correction needed**: Angle to achieve target alignment - **Plan osteotomy level**: At CORA to avoid translation ### Medial Opening Wedge Technique **Advantages**: - Preserves bone stock (no bone removal) - Easier to adjust correction intraoperatively - Safer for common peroneal nerve (no stretch) - Better fixation options with lateral locked plate - Can correct larger deformities **Disadvantages**: - Increases patellar height (patella alta risk) - Delayed union if gap greater than 15mm without graft - Requires bone graft or substitute for large gaps - Potential for loss of correction during healing This is the preferred technique for most DFO cases. ### Lateral Closing Wedge Technique **Advantages**: - Decreases patellar height (useful if pre-existing alta) - Inherently more stable (bone-to-bone contact) - No need for bone graft - Faster healing (compression at osteotomy site) **Disadvantages**: - **Common peroneal nerve at risk** - nerve stretch with bone removal - Less forgiving - difficult to adjust correction - Removes bone stock (problem for future TKA) - Limited correction possible (over 15 degrees risks nerve) - More complex surgical dissection When performing lateral closing wedge, the common peroneal nerve must be identified and protected throughout. Nerve palsy occurs in up to 10% of cases from stretch injury as the lateral cortex is closed. Consider prophylactic peroneal nerve decompression if correction is greater than 12 degrees. Reserved for select cases where patella alta is a concern. ### Biplanar Osteotomy **Indications**: - Combined deformities (valgus + procurvatum/recurvatum) - Rotational malalignment requiring correction - Complex multiplanar deformity **Technique**: - Two osteotomy cuts at different planes - Allows correction in coronal and sagittal planes - Requires specialized planning (often computer-assisted) - Fixation more complex (dual plates or custom implants) **Outcomes**: - Accurate correction of complex deformity - Higher complication rate (learning curve) - Longer operative time - Requires advanced surgical experience This technique is for complex cases not amenable to standard uniplanar correction. - **Pain location**: Lateral knee, worse with activity - **Valgus thrust**: Dynamic valgus with walking - **Activity level**: High demand, unable to continue sports - **Failed conservative**: Bracing, NSAIDs, injections, physio - **Young age**: Too young for arthroplasty (under 60) - **Functional goals**: Return to impact activities - **Gait**: Valgus thrust during stance phase - **Alignment**: Standing - visible valgus deformity - **Range of motion**: Flexion over 100°, FFD less than 15° - **Stability**: Assess LCL, posterolateral corner - **Palpation**: Lateral joint line tenderness - **Special tests**: Varus stress (LCL competence) **Absolute contraindications**: Inflammatory arthritis (rheumatoid, psoriatic), active infection, severe osteoporosis, unrealistic patient expectations, medical unfitness. **Relative contraindications**: Age over 65 years, BMI greater than 35, flexion contracture greater than 15 degrees, tricompartmental arthritis, patellofemoral arthritis, smoking (nonunion risk), noncompliance with rehab. **Weight-bearing AP hip-to-ankle films** are mandatory. Identify mechanical axis, measure MAD (mechanical axis deviation), calculate CORA, determine correction angle needed. Measure LDFA (lateral distal femoral angle) - normal 88 degrees. Assess joint line obliquity. **AP, lateral, skyline views** of affected knee. Grade compartment arthritis (Kellgren-Lawrence or Ahlback). Assess patellofemoral joint. Measure posterior tibial slope if planning combined procedures. **Assess cartilage status** in all compartments. Evaluate menisci (consider meniscal transplant if deficient). Check ligaments (LCL, PCL, posterolateral corner). Identify subchondral edema (predictor of pain). **Software-based planning** (TraumaCad, Materialise) for complex cases. Simulate correction, plan osteotomy cuts, create custom guides. Particularly useful for biplanar osteotomies. **Target**: Mechanical axis through Fujisawa point (62% from medial tibial edge), which corresponds to 3-5 degrees valgus overcorrection. **Calculation method**: 1. Measure current mechanical axis deviation (MAD) in mm 2. Measure width of tibial plateau 3. Calculate target MAD at 62% point 4. Use trigonometry or planning software to determine correction angle 5. Typically requires 10-15 degrees correction for symptomatic valgus **Example**: If tibial plateau is 80mm wide, Fujisawa point is at 49.6mm from medial edge (62%). If current MAD is 20mm lateral, need to shift axis 69.6mm medially - this usually requires 12-14 degree correction. ### Conservative Treatment First-Line **All patients should trial nonoperative management** for at least 6 months unless severe symptoms. Activity modification, NSAIDs, ice, weight loss if BMI over 30. Physical therapy for quadriceps strengthening, hamstring stretching, gait training. Unloader bracing (medial unloader for valgus knee - pushes knee into varus). Intra-articular corticosteroid injection (diagnostic and therapeutic). Consider viscosupplementation (hyaluronic acid). If symptoms persist despite optimal conservative care, patient remains high demand and meets surgical criteria, proceed to surgical planning. If improved, continue conservative management with annual follow-up. **Indications for surgery**: Persistent pain limiting activities, failed 6 months conservative care, suitable anatomy and patient factors. ### When to Operate Consider combined procedures: LCL or posterolateral corner reconstruction, meniscal allograft transplant, cartilage restoration (ACI, MACI). ### Preoperative Planning - **Nonunion/delayed union**: 5-10%, higher with large gaps - **Common peroneal nerve palsy**: 2-5% (opening wedge lower risk) - **Loss of correction**: 5-8% during healing - **Infection**: 2% superficial, 1% deep - **Patella alta**: Opening wedge increases height - **Conversion to TKA**: 15-20% at 10 years - **Implants**: Lateral distal femoral locked plate (appropriate size) - **Power**: Oscillating saw, drill - **Imaging**: C-arm - confirm can visualize full correction - **Bone graft**: Allograft or substitute if gap over 10mm - **Navigation**: Optional - improves accuracy - **K-wires**: For temporary fixation and guide pins ### Patient Positioning **Supine** on radiolucent table. Bump under ipsilateral hip (30 degrees) for lateral exposure. Knee flexed over bolster at 20-30 degrees. Thigh tourniquet applied but not inflated (preserve blood supply to osteotomy). - **Bony prominences**: Sacrum, contralateral heel - **Nerves**: Ensure no pressure on peroneal nerve at fibular head - **Position bolster**: Under distal femur/proximal tibia - **Landmarks exposed**: ASIS to ankle - **Limb**: Free drape to allow manipulation - **C-arm access**: Confirm AP and lateral views obtainable - **Prepare both legs**: For alignment comparison ### Surgical Approach - Lateral Distal Femur **Lateral longitudinal incision** 10-12cm, centered over distal femoral metaphysis. Start 5cm proximal to joint line, extend proximally. Incise along lateral aspect of vastus lateralis. **Incise iliotibial band** longitudinally. Develop plane between vastus lateralis anteriorly and lateral intermuscular septum posteriorly. Retract vastus anteriorly to expose lateral femur. **Elevate periosteum** from lateral distal femur. Expose anterior and posterior cortices for plate placement. Protect posteriorly - popliteal vessels behind bone. Place retractors carefully. **Fluoroscopy AP and lateral** to confirm adequate exposure of planned osteotomy site. Place K-wire as reference at CORA level (typically 3-4cm proximal to joint line). Key surgical landmarks: lateral femoral condyle, adductor tubercle (posteromedially), vastus lateralis muscle. ### Osteotomy Cut and Opening **Biplanar osteotomy** recommended. Ascending cut from lateral cortex aimed at medial cortex 1cm proximal to joint. Leave 1cm medial hinge intact. Mark with K-wires to define cut plane. **Two parallel K-wires** placed from lateral cortex toward medial cortex under fluoroscopy. Ensure wires stay above joint line medially (avoid intra-articular penetration). Check on both AP and lateral views. **Oscillating saw cut** between guide wires. Cut 90% through lateral to medial, leave 5-10mm medial hinge intact. Protect soft tissues posteriorly with retractor. Preserve medial cortex to act as hinge. **Use calibrated osteotomy spreaders** or lamina spreaders. Open wedge gradually while monitoring alignment with C-arm. Check mechanical axis cable - aim for Fujisawa point. Typical opening 10-15mm at lateral cortex. **Intraoperative alignment check**: Use alignment rod from hip center to ankle center on AP fluoroscopy. Confirm mechanical axis passes through 62% point (Fujisawa). Adjust if needed before fixation. The medial cortical hinge provides stability and compression for healing. If the hinge fractures during opening, stability is lost and nonunion risk increases significantly. Open the wedge slowly and monitor for medial hinge crack. If hinge breaks, consider adding medial support plate. ### Plate Fixation **Lateral distal femoral locked plate** (titanium or stainless steel). Choose length to achieve 4-5 screws proximal to osteotomy and 3-4 screws distal. Contour plate to match lateral femoral anatomy. **Apply plate to lateral femur** with distal screws in subchondral bone. Ensure plate does not block joint line. Temporarily fix with K-wires. Check position on fluoroscopy AP and lateral. **Insert distal locked screws first** (3-4 screws in distal fragment). Then insert proximal locked screws (4-5 screws in proximal fragment). Alternate sides to compress osteotomy slightly. Check all screw lengths on fluoroscopy. **If gap greater than 10mm**: Fill with structural allograft (tricortical iliac crest) or bone graft substitute (calcium phosphate, DBM). Pack graft into defect. Consider medial cortical support if large gap or hinge fracture. **Fluoroscopy AP, lateral, and obliques**: Confirm alignment, plate position, screw lengths adequate but not penetrating opposite cortex. Perform cable test - mechanical axis through target zone. ### Wound Closure **Meticulous hemostasis** - use electrocautery for bleeding. No tourniquet used during case, so achieve good hemostasis. Consider drain if significant oozing (remove at 24-48 hours). **Close iliotibial band** with absorbable suture (1-0 Vicryl). Approximate vastus lateralis to lateral septum. Close subcutaneous layer (2-0 Vicryl). Skin with staples or subcuticular suture. **Sterile dressing** over wound. Apply **hinged knee brace locked in extension** for first 6 weeks. Ice and elevation. Document neurovascular status post-procedure. ### Technical Pearls - **Biplanar osteotomy**: More stable than uniplanar - **Preserve medial hinge**: Critical for healing - **Use locked plate**: Better hold in metaphyseal bone - **Intraoperative alignment**: Cable test to confirm correction - **Bone graft gaps over 10mm**: Prevents delayed union - **Don't break medial hinge**: Open slowly, monitor fluoroscopy - **Don't under-correct**: Aim for 3-5 degree valgus overcorrection - **Don't penetrate joint**: Keep osteotomy 3cm proximal to joint line - **Don't forget graft**: Large gaps without graft = nonunion - **Don't use tourniquet**: Impairs bone healing at osteotomy ### Intraoperative Troubleshooting Peroneal nerve palsy typically manifests immediately post-op (stretch injury during surgery) or within 24-48 hours (hematoma compression). **Foot drop is the key finding** - loss of ankle dorsiflexion and toe extension. Most cases (80%) recover spontaneously over 3-6 months. Consider surgical exploration if complete palsy with no recovery at 3 months or progressive worsening. **Hinged knee brace locked in extension**. Neurovascular checks every 2 hours for 24 hours. Ice and elevation. DVT prophylaxis (LMWH or rivaroxaban). Pain management (multimodal - paracetamol, NSAIDs, opioids PRN). **Non-weight-bearing (NWB) with crutches**. Brace remains locked in extension for ambulation. Unlock brace for passive ROM exercises - 0-90 degrees. Quadriceps sets, straight leg raises. Drain removal at 24-48 hours if placed. **Remain NWB on affected leg**. Gradually increase ROM to 0-120 degrees. Quad strengthening, hamstring stretches. Brace locked in extension for ambulation, unlock for exercises. Wound check at 2 weeks, staples/sutures out at 14 days. Opening wedge osteotomy has no bone-to-bone contact - healing depends on graft incorporation and new bone formation bridging the gap. Early weight-bearing risks loss of correction or graft collapse. NWB for 6 weeks allows initial healing before load application. **Radiographs - AP and lateral knee**. Look for bridging callus across osteotomy site. If callus present, progress to touch-down weight-bearing (TDWB) with crutches. If no callus, continue NWB for 2 more weeks. **TDWB (10-20kg)** with crutches. Brace can be unlocked for ambulation if good quad control. Progressive ROM exercises. Begin closed chain exercises (mini squats, wall slides). Stationary cycling (no resistance). **Increase weight-bearing by 25% every 2 weeks** as tolerated. By week 12, aim for full weight-bearing (FWB) if radiographs show progressive healing. Wean off crutches gradually. Discontinue brace at 12 weeks if good quad strength and alignment maintained. Radiographs every 6 weeks to monitor healing and alignment. **Full weight-bearing without aids**. Progressive resistance training - quad, hamstring, glute exercises. Balance and proprioception training. Swimming, aquatic therapy. Avoid impact activities until 6 months. **Advance to functional exercises** - lunges, step-ups, leg press. Cycling with resistance. Elliptical trainer. Goal: return to ADLs without limitations. Address any persistent stiffness with aggressive ROM exercises. **Radiographs at 6 months** - confirm union and maintenance of correction. If healed, clear for **low-impact sports** (cycling, swimming, golf). **High-impact sports** (running, basketball) permitted at 9-12 months if asymptomatic and good strength. Return to full activities as tolerated. **Age over 55 years**: Lower survivorship, higher TKA conversion rate. **BMI over 35**: Increased load, higher failure rate. **Tricompartmental arthritis**: DFO does not address medial or PF disease. **Flexion contracture over 15 degrees**: Difficult to correct, poor function. **Under-correction**: Failure to achieve 3-5 degree valgus overcorrection leads to recurrent symptoms. **Smoking**: Nonunion risk, impaired healing. - Age under 55 years (too young for TKA) - High activity demand (impact sports) - Isolated lateral compartment disease - Desire to preserve native knee anatomy - Good bone quality and soft tissue envelope - Realistic expectations (DFO buys 10-15 years) - Age over 65 years (TKA longevity expected) - Low activity demand (sedentary lifestyle) - Tricompartmental arthritis - Severe flexion contracture (over 20 degrees) - Poor bone quality (severe osteoporosis) - Medical comorbidities limiting rehab compliance **Q: What is the Fujisawa point and why is it the target for mechanical axis correction in DFO?** A: The Fujisawa point is located at **62% of the tibial plateau width measured from the medial edge**. This corresponds to approximately 3-5 degrees valgus overcorrection from neutral. The mechanical axis passing through this point provides optimal load redistribution to the healthier medial compartment while avoiding excessive valgus and lateral soft tissue laxity. Original Fujisawa study (1979) showed best outcomes with mechanical axis at this location. **Q: What is CORA and why must the osteotomy be performed at the CORA level?** A: CORA stands for **Center of Rotation and Angulation** - the point where the proximal mechanical axis and distal mechanical axis intersect on long-leg radiographs. If the osteotomy is performed away from CORA, the correction creates an unwanted **translation deformity** in addition to the angular correction. For valgus knee, CORA is typically at the distal femoral metaphysis, 3-4cm proximal to the joint line. **Q: What are the advantages of medial opening wedge over lateral closing wedge DFO?** A: Opening wedge advantages: (1) **Preserves bone stock** - no bone removal, (2) **Safer for common peroneal nerve** - no stretch injury risk, (3) **More adjustable** - easier to modify correction intraoperatively, (4) **Allows larger corrections** - closing wedge limited by nerve proximity. Main disadvantage is opening wedge increases patellar height (patella alta risk) and may require bone graft for large gaps. **Q: What is the most feared complication of DFO and how can it be prevented?** A: **Common peroneal nerve palsy** is the most feared complication. Incidence is 2-5% with opening wedge, higher (10%) with closing wedge due to nerve stretch. Prevention strategies: (1) Choose opening wedge over closing when possible, (2) Meticulous nerve identification and protection during lateral approach, (3) Avoid excessive correction (over 15 degrees) with closing wedge, (4) Monitor for hematoma post-operatively which can compress nerve, (5) Consider prophylactic nerve decompression if high-risk case. **Q: What are the ideal patient characteristics for DFO?** A: Ideal DFO candidate: **Age 40-55 years** (too young for TKA), **high activity demand** (wants to return to impact sports), **isolated lateral compartment OA** (medial and PF compartments healthy), **BMI less than 30**, **good ROM** (flexion over 100 degrees, FFD less than 15 degrees), **stable ligaments** or amenable to combined reconstruction, **non-smoker**, **realistic expectations** that DFO buys 10-15 years before eventual TKA. **Q: What is the expected survivorship of DFO and what factors predict failure?** A: DFO survivorship (avoiding conversion to TKA): **85% at 5 years, 75% at 10 years, 60% at 15 years**. Predictors of failure: **Age over 55**, **BMI over 35**, **under-correction** (failure to achieve 3-5 degree valgus overcorrection), **tricompartmental arthritis at index surgery**, **patellofemoral arthritis**, **flexion contracture over 15 degrees**, **smoking**. Accurate correction to Fujisawa point is single most important technical factor. - **Osteotomy procedures rare**: Less than 1% of knee procedures registered - **Conversion to TKA**: Tracked as separate category - prior osteotomy - **Revision burden**: Lower than primary TKA, but outcomes after conversion variable - **Australian practice**: DFO less common than HTO due to valgus being less common - **Registry message**: Young patient joint preservation important public health goal - **ACSQHC VTE prophylaxis**: LMWH or DOAC for major orthopedic surgery - **DVT risk**: Moderate-high due to lower limb surgery and restricted mobility - **Duration**: Until mobile (typically 10-14 days minimum) - **Antibiotic prophylaxis**: Cefazolin 2g IV pre-incision (eTG guidelines) - **Blood conservation**: Tranexamic acid 15mg/kg IV at incision and closure **Key documentation requirements for DFO:** **Informed consent must include**: - Realistic timeline - 6-12 months to return to activities, longer for bone healing - Conversion to TKA expectation - 15-20% by 10 years, eventual endpoint for most - Nerve injury risk - common peroneal nerve palsy 2-5%, may be permanent - Nonunion risk - 5-10%, may require revision surgery - Loss of correction - may need revision osteotomy - Alternative of proceeding directly to TKA **Common litigation issues**: - **Nerve palsy without documented nerve protection** - ensure operative note details nerve identification - **Nonunion without bone graft** for large gaps - standard of care to graft gaps over 10mm - **Under-correction** - failure to achieve adequate realignment leads to early failure - **Patient selection errors** - performing DFO in poor candidate (tricompartmental OA, elderly) leads to predictable failure **Public System Coverage**: - Distal femoral osteotomy with internal fixation covered under public hospital system - Bone grafting procedures covered when required - Document medical necessity and failed conservative care - **Public hospital access**: Limited - typically reserved for younger patients, high demand - **Private coverage**: Most private insurers cover with orthopedic policy - **Gaps**: Implant costs can be significant (locked plates expensive) - **Rehabilitation**: Requires intensive physiotherapy - ensure patient has access - **DVT prophylaxis**: Mandatory in Australian hospitals (ACSQHC standard) - **Timing**: At least 48 hours before surgery (cooling-off period) - **Written material**: Provide handout with diagrams, complication rates - **Document alternatives**: TKA, ongoing conservative care, activity modification - **Realistic expectations**: DFO buys time, not curative, most eventually need TKA - **Nerve palsy risk**: Specifically mention peroneal nerve and foot drop possibility - **Revision risk**: Nonunion may require further surgery

Distal Femoral Osteotomy

Distal Femoral Osteotomy