High Yield Overview

DISTAL FEMORAL OSTEOTOMY

Valgus Correction | Lateral Compartment OA | Opening vs Closing Wedge

Critical DFO Exam Points

Indications

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).

CORA Identification

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.

Surgical Technique

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.

Key Complications

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.

Quick Decision Guide: Opening vs Closing Wedge DFO

Mnemonic

VALGUSDFO Indications Assessment

Memory Hook:Think VALGUS deformity when considering DFO - the clinical presentation drives the indication!

Mnemonic

CORAPreoperative Planning Steps

Memory Hook:Find the CORA before you cut - accurate planning prevents translation deformities!

Mnemonic

NERVEComplications to Discuss

Memory Hook:Mind the NERVE - peroneal nerve palsy is the nightmare complication to avoid!

Overview and Epidemiology

Clinical Context

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.

Demographics

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

Pathophysiology

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

Biomechanics and Mechanical Axis

Understanding CORA is Essential

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.

Mechanical Axis Alignment Goals

Fujisawa Point Target

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

CORA Determination

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

Classification of DFO Techniques

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.

Clinical Assessment and Patient Selection

History

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

Examination

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)

Contraindications - Know When NOT to Operate

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.

Patient Selection Criteria

Investigations and Surgical Planning

Imaging Protocol

EssentialStanding Long-Leg Radiographs

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.

StandardKnee Radiographs

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.

If AvailableMRI Knee

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).

AdvancedComputer-Assisted Planning

Software-based planning (TraumaCad, Materialise) for complex cases. Simulate correction, plan osteotomy cuts, create custom guides. Particularly useful for biplanar osteotomies.

Correction Angle Calculation

Target: Mechanical axis through Fujisawa point (62% from medial tibial edge), which corresponds to 3-5 degrees valgus overcorrection.

Calculation method:

Measure current mechanical axis deviation (MAD) in mm
Measure width of tibial plateau
Calculate target MAD at 62% point
Use trigonometry or planning software to determine correction angle
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.

Management Algorithm

Conservative Treatment First-Line

All patients should trial nonoperative management for at least 6 months unless severe symptoms.

Conservative Treatment Pathway

0-6 weeksInitial Management

Activity modification, NSAIDs, ice, weight loss if BMI over 30. Physical therapy for quadriceps strengthening, hamstring stretching, gait training.

6-12 weeksAdvanced Conservative

Unloader bracing (medial unloader for valgus knee - pushes knee into varus). Intra-articular corticosteroid injection (diagnostic and therapeutic). Consider viscosupplementation (hyaluronic acid).

3-6 monthsDecision Point

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.

Surgical Technique - Medial Opening Wedge DFO

Preoperative Planning

Consent Points

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

Equipment Checklist

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

Setup Checklist

Step 1Position

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).

Step 2Padding

Bony prominences: Sacrum, contralateral heel
Nerves: Ensure no pressure on peroneal nerve at fibular head
Position bolster: Under distal femur/proximal tibia

Step 3Draping

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

Exposure Steps

Step 1Skin Incision

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.

Step 2Superficial Dissection

Incise iliotibial band longitudinally. Develop plane between vastus lateralis anteriorly and lateral intermuscular septum posteriorly. Retract vastus anteriorly to expose lateral femur.

Step 3Subperiosteal Exposure

Elevate periosteum from lateral distal femur. Expose anterior and posterior cortices for plate placement. Protect posteriorly - popliteal vessels behind bone. Place retractors carefully.

Step 4Confirm Level

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.

Technical Pearls

Do's (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'ts (Pitfalls)

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

Common Problems and Solutions

Complications

Peroneal Nerve Palsy Timeline

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.

Postoperative Care and Rehabilitation

Early Rehabilitation

Immediate Post-opDay 0-1

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).

Initial MobilizationDay 1-14

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.

Progressive ROMWeek 2-6

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.

Why Non-Weight-Bearing Early?

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.

Weight-Bearing Protocol Summary

Outcomes and Prognosis

Predictors of Poor Outcome

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.

Factors Favoring DFO Over TKA

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)

When TKA is Better Option

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

Evidence Base and Key Trials

Puddu Classification and Opening Wedge DFO Technique

Puddu G, Cipolla M, Cerullo G, Franco V, Gianni E • Orthopedics (2007)

Clinical Implication: Opening wedge is the preferred technique for most DFO cases - safer for peroneal nerve and allows larger corrections.

Limitation: Case series without control group, relatively short follow-up

Long-Term Survivorship After DFO

Backstein D, Morag G, Hanna S, Safir O, Gross A • Clin Orthop Relat Res (2007)

Clinical Implication: DFO provides durable pain relief and function for 10-15 years in appropriately selected young patients.

Limitation: Retrospective study with variable techniques over time period

Complications After Distal Femoral Osteotomy

Nelissen EM, van Langelaan EJ, Nelissen RG • Int Orthop (2010)

Clinical Implication: Opening wedge DFO has lower nerve injury risk but requires careful attention to bone healing with grafting for large gaps.

Limitation: Heterogeneous studies with varying techniques and definitions of complications

Fujisawa Point - Optimal Mechanical Axis Target

Fujisawa Y, Masuhara K, Shiomi S • J Bone Joint Surg Am (1979)

Clinical Implication: Target mechanical axis at Fujisawa point (62% from medial tibial edge) for optimal load redistribution and outcomes.

Limitation: Originally described for HTO, extrapolated to DFO. Older study with limited follow-up.

Computer-Assisted DFO vs Conventional Technique

Ehlinger M, Spoor AB, Ollivier M, et al • Knee Surg Sports Traumatol Arthrosc (2020)

Clinical Implication: Computer-assisted surgery improves accuracy of correction but does not necessarily improve clinical outcomes. Consider for complex or biplanar osteotomies.

Limitation: Single center study, relatively short follow-up, learning curve not accounted for

Exam Viva Scenarios

Practice these scenarios to excel in your viva examination

VIVA SCENARIOStandard

Scenario 1: Standard DFO Case (2-3 min)

EXAMINER

"A 48-year-old recreational tennis player presents with lateral knee pain for 2 years. Failed physiotherapy, bracing, and intra-articular injections. Examination shows valgus thrust on gait, lateral joint line tenderness, ROM 0-130 degrees, stable to varus stress. Long-leg radiographs show 12 degrees valgus alignment with isolated lateral compartment Ahlback Grade 2 osteoarthritis. Mechanical axis passes 25mm lateral to knee center. What is your assessment and management?"

EXCEPTIONAL ANSWER

This is a symptomatic valgus knee deformity with isolated lateral compartment osteoarthritis in a young, active patient. I would take a systematic approach: First, confirm this patient has exhausted conservative management including activity modification, NSAIDs, physiotherapy for quadriceps strengthening, and unloader bracing. Second, on examination I would document the valgus thrust, assess range of motion (excellent at 0-130 degrees), check ligamentous stability (LCL and posterolateral corner), and examine patellofemoral joint for crepitus. Third, on imaging I would confirm isolated lateral compartment disease, measure the mechanical axis deviation (25mm lateral indicates significant valgus), identify the CORA at the distal femoral metaphysis, and calculate required correction to achieve Fujisawa point target (62% from medial tibial edge, typically 3-5 degrees valgus overcorrection). My surgical plan would be medial opening wedge distal femoral osteotomy with lateral locked plate fixation. I would counsel about 85% survivorship at 5 years, realistic expectations of pain reduction and functional improvement, complications including nonunion (5-10%), nerve injury (2-5%), and eventual conversion to TKA in 15-20% by 10 years.

VIVA SCENARIOChallenging

Scenario 2: DFO Surgical Technique (3-4 min)

EXAMINER

"Walk me through your surgical technique for medial opening wedge distal femoral osteotomy. Include positioning, approach, osteotomy technique, fixation, and how you confirm adequate correction intraoperatively."

EXCEPTIONAL ANSWER

For medial opening wedge DFO, patient positioning is supine on radiolucent table with bump under ipsilateral hip for lateral exposure, knee flexed 20-30 degrees over bolster. No tourniquet to preserve blood supply to osteotomy. My approach is lateral longitudinal incision 10-12cm centered over distal femoral metaphysis, incise iliotibial band, develop plane between vastus lateralis and lateral intermuscular septum, subperiosteal exposure of lateral femur. For the osteotomy, I use a biplanar technique: place two parallel K-wire guides from lateral cortex aimed at medial cortex 1cm proximal to joint line under fluoroscopy, use oscillating saw to cut between wires leaving 5-10mm medial hinge intact, open wedge gradually with calibrated spreaders while monitoring alignment. Intraoperative correction is verified using alignment cable from hip center to ankle center on AP fluoroscopy - aim for mechanical axis through Fujisawa point (62% from medial tibial edge). For fixation, I use lateral distal femoral locked plate with 3-4 distal locked screws and 4-5 proximal locked screws, fill gaps greater than 10mm with structural allograft or bone graft substitute. Closure includes iliotibial band repair, subcutaneous layer, skin, and application of hinged knee brace locked in extension. Postoperative protocol is non-weight-bearing for 6 weeks, then progressive weight-bearing based on radiographic healing.

VIVA SCENARIOCritical

Scenario 3: Complication Management (2-3 min)

EXAMINER

"A 52-year-old patient is 6 months post-DFO. Radiographs show no bridging callus across the osteotomy site. The patient has ongoing lateral knee pain and cannot weight-bear fully. How do you manage this delayed union or nonunion?"

EXCEPTIONAL ANSWER

This presentation is concerning for nonunion at the DFO osteotomy site. My immediate assessment would include detailed history about compliance with weight-bearing restrictions (early weight-bearing can cause nonunion), smoking status, nutritional status, and current symptoms. I would examine for tenderness at osteotomy site, assess alignment maintenance, and check for hardware failure. Investigations would include CT scan to definitively assess union (radiographs can underestimate healing), inflammatory markers to rule out infection, vitamin D and calcium levels. The differential diagnosis includes delayed union (still has healing potential), nonunion (no healing by 6 months), infection (low-grade), or hardware failure. Treatment depends on several factors: if alignment is maintained and patient has minimal symptoms, I would trial bone stimulator (ultrasound or electrical) with continued protected weight-bearing for 3 more months. If symptomatic nonunion with maintained alignment, I would perform revision surgery with bone grafting (iliac crest autograft or structural allograft), evaluate and augment fixation if needed, consider exchange to larger plate or add medial support plate. If alignment is lost or infection present, more extensive revision is needed - debridement, new fixation, staged grafting if infected. Prevention strategies for future cases include avoiding nonunion risk factors (optimize nutrition, smoking cessation mandatory), using bone graft for gaps over 10mm, ensuring adequate fixation, strict adherence to non-weight-bearing protocol early. I would counsel this patient that revision surgery has 80% success rate for achieving union, but timeline to full recovery is extended by 6-12 months.

MCQ Practice Points

Biomechanics Question

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.

CORA Concept Question

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.

Technique Comparison Question

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.

Complication Question

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.

Indication Question

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.

Outcome Question

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.

Australian Context and Medicolegal Considerations

AOANJRR Data

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

Australian Guidelines

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

Medicolegal Considerations

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

Hospital Systems

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)

Consent Best Practice

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