PCL AVULSION FRACTURES
Posterior Tibial Avulsion | Posterior Approach | Screw or Suture Fixation
AVULSION TYPES
Critical Must-Knows
- PCL avulsion fracture = PCL avulses from posterior tibia with bone fragment (better prognosis than midsubstance tear)
- Posterior approach - patient prone, popliteal vessels at risk, must protect neurovascular bundle
- Optimal timing: Within 3 weeks - earlier fixation has better outcomes (85-95% good results)
- Fixation options: Screw (large fragment) or suture anchors (small fragment) - both achieve excellent outcomes
- Advantage over reconstruction: Bony healing is faster and more reliable than ligament reconstruction
Examiner's Pearls
- "PCL avulsion fracture = PCL avulses from posterior tibia with bone fragment - better prognosis than midsubstance tear
- "Posterior approach with patient prone - popliteal artery at risk, must protect neurovascular bundle
- "Optimal timing within 3 weeks - earlier fixation achieves 85-95% good results
- "Screw fixation for large fragments, suture anchors for small fragments - both excellent outcomes
Critical PCL Avulsion Fracture Exam Points
Better Prognosis Than Midsubstance Tear
PCL avulsion fracture has better prognosis than midsubstance PCL tear. Bony healing is faster and more reliable than ligament reconstruction. 85-95% good results with proper fixation. Always attempt fixation if fragment is adequate.
Posterior Approach Critical
Posterior approach with patient prone - popliteal artery and tibial nerve at risk. Must protect neurovascular bundle. Use posterior midline or posteromedial approach. Identify vessels before any dissection.
Optimal Timing
Within 3 weeks for best outcomes - earlier fixation achieves 85-95% good results. Delayed fixation (over 6 weeks) may require reconstruction instead of fixation. Timing is critical for success.
Fixation Options
Screw fixation (large fragment) or suture anchors (small fragment) - both achieve excellent outcomes. Screw provides compression, suture anchors for small or comminuted fragments. Choose based on fragment size.
PCL Avulsion Fractures - Quick Decision Guide
| Fragment Size | Timing | Fixation Method | Outcome |
|---|---|---|---|
| Large (over 1cm) | Within 3 weeks | Screw fixation | 85-95% good results |
| Small (under 1cm) | Within 3 weeks | Suture anchors | 85-95% good results |
| Comminuted | Within 3 weeks | Suture anchors | 80-90% good results |
| Any size | Over 6 weeks | May need reconstruction | 60-80% good results |
PCL AVULSIONPCL Avulsion Fracture Features
Memory Hook:PCL AVULSION: Posterior approach, Critical timing (3 weeks), Large fragment = screw, Anchors for small, Vessels at risk, Under 3 weeks optimal, Ligament better than midsubstance, Screw or suture both good, Identify vessels first, Outcomes 85-95%, Non-weight bearing 6 weeks!
POSTERIORPosterior Approach Steps
Memory Hook:POSTERIOR approach: Prone position, Open approach, Safely identify vessels, Tibial fragment exposure, Expose posterior tibia, Reduce fragment, Internal fixation, Outcomes excellent, Repair PCL!
RISKSComplications
Memory Hook:RISKS: Retraction injury to vessels, Inadequate fixation causes nonunion, Stiffness from immobilization, Killer curve not applicable (avulsion), Stiffness prevention with early ROM!
Overview and Epidemiology
PCL avulsion fractures occur when the PCL avulses from its insertion on the posterior tibia, taking a bone fragment with it. This is better than midsubstance PCL tears because bony healing is faster and more reliable than ligament reconstruction. Treatment involves surgical fixation via posterior approach.
Mechanism of Injury
Dashboard injury (classic mechanism):
- Motor vehicle accident: Knee strikes dashboard with knee flexed
- Posterior force: Posteriorly directed force on proximal tibia
- PCL avulses: PCL insertion on posterior tibia avulses with bone fragment
- High energy: Usually high-energy trauma
Other mechanisms:
- Hyperflexion: Extreme knee flexion
- Direct trauma: Posterior blow to proximal tibia
- Fall: Landing on flexed knee
The PCL inserts on the posterior tibia, 1-1.5cm below the joint line. When excessive posterior force is applied, the PCL avulses from the tibia, taking a bone fragment with it.
Better Prognosis Than Midsubstance Tear
PCL avulsion fracture has better prognosis than midsubstance PCL tear. Bony healing is faster and more reliable than ligament reconstruction. 85-95% good results with proper fixation vs 60-80% for midsubstance tears. Always attempt fixation if fragment is adequate.
Epidemiology
- Incidence: 5-10% of PCL injuries
- Age: Peak 20-40 years (trauma population)
- Gender: Male predominance (3:1 ratio)
- Laterality: Usually unilateral
- Associated injuries: PLC injury (20-30%), ACL injury (10-15%), meniscal tears (10-20%)
Anatomy and Pathophysiology
PCL Anatomy
The posterior cruciate ligament (PCL):
- Origin: Posteromedial lateral femoral condyle (intercondylar notch)
- Insertion: Posterior tibia, 1-1.5cm below joint line (posterior intercondylar area)
- Two bundles: Anterolateral (AL) and posteromedial (PM)
- Blood supply: Middle genicular artery
- Function: Primary restraint to posterior tibial translation (95% at 90 degrees flexion)
PCL insertion site:
- Location: Posterior tibia, 1-1.5cm below joint line
- Size: 1-2cm area
- Relationship: Close to popliteal artery (separated by popliteus muscle)
- Bone quality: Good cancellous bone for fixation
Pathophysiology
Avulsion mechanism:
- Posterior force: Excessive posterior force on proximal tibia
- PCL tension: PCL experiences excessive tension
- Bone weaker than ligament: In some cases, bone-ligament interface fails
- Avulsion: PCL avulses from tibia with bone fragment
Why avulsion is better:
- Bony healing: Faster and more reliable than ligament healing
- Anatomic: Can restore native PCL insertion
- Outcomes: 85-95% good results vs 60-80% for midsubstance tears
- Timing: Earlier fixation has better outcomes
Fragment characteristics:
- Size: Usually 1-2cm (varies)
- Location: Posterior tibia, PCL insertion site
- Quality: Usually good bone quality
- Displacement: Usually displaced posteriorly
Popliteal Artery at Risk
Popliteal artery lies directly posterior to the tibia, separated by only the popliteus muscle. During posterior approach, the neurovascular bundle must be carefully protected. Tethering at the soleal arch makes it vulnerable to injury with posterior displacement.
Classification Systems
Fragment Size Classification
Large fragment (over 1cm):
- Usually single fragment
- Good bone quality
- Treatment: Screw fixation (compression)
- Outcomes: 85-95% good results
Small fragment (under 1cm):
- May be single or multiple fragments
- Treatment: Suture anchors
- Outcomes: 85-95% good results
Comminuted:
- Multiple fragments
- May be difficult to fix
- Treatment: Suture anchors or reconstruction
- Outcomes: 80-90% good results
Fragment size determines fixation method and predicts outcomes.
Clinical Assessment
History
Mechanism: Dashboard injury (classic)
- Motor vehicle accident (knee strikes dashboard)
- Posterior force on proximal tibia
- High-energy trauma
Symptoms:
- Immediate pain and swelling
- Inability to bear weight
- Knee "giving way" (instability)
- Posterior knee pain
Physical Examination
Inspection:
- Knee effusion (hemarthrosis)
- Antalgic gait
- Knee held in slight flexion
Palpation:
- Tenderness over posterior knee
- Posterior tibial step-off (abnormal - normal is 1cm anterior)
Range of Motion:
- Limited flexion (pain, effusion)
- Limited extension (pain, effusion)
Ligament Testing:
- Posterior drawer: Positive (posterior translation) - most sensitive
- Posterior sag sign: Positive (tibia sags posteriorly)
- Quadriceps active test: Positive (tibia reduces with quadriceps contraction)
- Dial test: May be positive (if PLC injured)
Clinical Examination Key Point
Posterior drawer test is most sensitive for PCL injury - assess posterior tibial translation and endpoint quality. Normal tibial step-off is 1cm anterior to femoral condyle. PCL injury causes posterior translation.
Associated Injuries
- PLC injury: 20-30% (posterolateral corner)
- ACL injury: 10-15%
- Meniscal tears: 10-20%
- Bone bruises: Anterior tibia, anterior femur (kissing contusion pattern)
Investigations
Standard X-ray Protocol
Views: AP and lateral knee.
Key findings:
- PCL avulsion fragment: Visible on lateral view (posterior tibia)
- Fragment size: Assess size and displacement
- Posterior tibial step-off: Abnormal (normal is 1cm anterior)
- Associated fractures: Tibial plateau, femoral condyle
Lateral view is critical - shows fragment and posterior displacement.
Management Algorithm
Management Pathway
PCL Avulsion Fracture Management
Determine fragment size, displacement, and timing. Assess for associated injuries (PLC, ACL, meniscus). Plan surgical approach.
Optimal timing. Posterior approach, reduce fragment, fix with screw (large) or suture anchors (small). Excellent outcomes (85-95% good results).
May still be fixable. Attempt fixation if fragment mobile. May need reconstruction if fixed. Good outcomes (75-85%).
Fragment usually fixed. May require PCL reconstruction instead of fixation. Outcomes lower (60-80%).
Surgical Technique
Posterior Approach Technique
Patient Positioning:
- Prone on standard operating table
- Tourniquet on thigh (may deflate for exposure)
- Contralateral leg abducted
- Image intensifier positioned
Incision:
- Posterior midline or posteromedial approach
- 8-10cm incision
- Full-thickness flaps
Exposure:
- Identify neurovascular bundle first (popliteal artery, tibial nerve)
- Protect with vessel loops
- Retract medially or laterally
- Expose posterior tibia
- Identify PCL avulsion fragment
Critical: Popliteal artery at risk - must identify and protect before any dissection.
Popliteal Artery Protection
Popliteal artery lies directly posterior to the tibia, separated by only the popliteus muscle. During posterior approach, identify and protect the neurovascular bundle before any dissection. Use vessel loops to retract. Avoid excessive retraction. The artery is vulnerable to injury with posterior displacement.
Complications
| Complication | Incidence | Risk Factors | Prevention/Management |
|---|---|---|---|
| Neurovascular injury | Less than 5% | Inadequate exposure, excessive retraction | Identify vessels first, protect with vessel loops |
| Nonunion | 5-10% | Inadequate fixation, poor reduction | Secure fixation, good bone apposition |
| Residual laxity | 10-15% | Malreduction, inadequate fixation | Anatomic reduction, secure fixation |
| Stiffness | 5-10% | Prolonged immobilization | Early ROM (2-4 weeks) |
| Hardware issues | 5-10% | Prominent hardware | Countersink screws, use suture anchors if prominent |
Neurovascular Injury
Less than 5% incidence:
- Cause: Inadequate exposure, excessive retraction, direct injury
- Prevention: Identify popliteal artery and tibial nerve first, protect with vessel loops, avoid excessive retraction
- Management: Immediate vascular surgery consultation if arterial injury
Nonunion
5-10% incidence:
- Cause: Inadequate fixation, poor reduction, fragment devascularization
- Prevention: Secure fixation, good bone apposition, proper timing
- Management: Revision fixation with bone graft if needed
Residual Laxity
10-15% incidence:
- Cause: Malreduction, inadequate fixation, fragment resorption
- Prevention: Anatomic reduction, secure fixation
- Management: Revision fixation if symptomatic, PCL reconstruction if needed
Postoperative Care
Immediate Postoperative
- Immobilization: Hinged knee brace locked in extension (4-6 weeks)
- Weight bearing: Non-weight bearing initially (4-6 weeks)
- ROM: Begin passive ROM at 2-4 weeks (unlock brace)
- PT: Quadriceps sets, straight leg raises (immediate)
Rehabilitation Protocol
Weeks 0-2:
- Brace locked in extension
- Non-weight bearing
- Quadriceps sets, straight leg raises
- Ice and elevation
Weeks 2-4:
- Unlock brace for passive ROM (0-90 degrees)
- Continue non-weight bearing
- Stationary bike (when ROM allows)
- Continue quadriceps strengthening
Weeks 4-6:
- Progressive weight bearing (partial to full)
- Full passive ROM
- Continue quadriceps strengthening
- Balance and proprioception
Weeks 6-12:
- Full weight bearing
- Progressive strengthening
- Sport-specific training
- Return to sport (when strength and ROM normal)
Return to Sport
Criteria:
- Full ROM (equal to contralateral)
- Quadriceps strength greater than 90% of contralateral
- No instability (negative posterior drawer)
- Functional testing passed
Timeline: Usually 6-9 months postoperatively.
Outcomes and Prognosis
Overall Outcomes
Surgical fixation outcomes:
- Success rate: 85-95% (excellent with proper technique and timing)
- Functional outcomes: 80-85% return to pre-injury level
- Complications: 10-15% (nonunion, residual laxity, stiffness)
Timing effects:
- Acute (under 3 weeks): 85-95% good results
- Subacute (3-6 weeks): 75-85% good results
- Chronic (over 6 weeks): 60-80% good results (may need reconstruction)
Functional Outcomes
Return to sport:
- Timeline: 6-9 months postoperatively
- Rate: 80-85% return to pre-injury level
- Factors: Age, sport level, rehabilitation compliance, timing of fixation
Functional testing:
- Quadriceps strength: 90%+ of contralateral
- No instability (negative posterior drawer)
- Full ROM
Long-Term Prognosis
Residual laxity:
- 10-15% have some residual posterior laxity
- Usually asymptomatic (does not affect function)
- May require revision if symptomatic
Arthritis risk:
- Low risk with proper treatment (less than 5% at 10 years)
- Higher risk with malreduction or persistent instability
- Proper reduction and fixation minimize risk
Factors Affecting Outcomes
Positive factors:
- Early fixation (within 3 weeks)
- Anatomic reduction
- Secure fixation
- Complete rehabilitation
Negative factors:
- Delayed fixation (over 6 weeks)
- Malreduction
- Inadequate fixation
- Incomplete rehabilitation
Prevention and Return to Sport
Prevention
Primary prevention:
- Proper seatbelt use (prevents dashboard injury)
- Airbag deployment
- Safe driving practices
- Protective equipment in sports
Secondary prevention (after injury):
- Complete rehabilitation before return to sport
- Continued strength and conditioning
- Gradual return to activity
Return to Sport Criteria
Clinical:
- Full ROM (equal to contralateral)
- Quadriceps strength greater than 90% of contralateral
- No effusion
- No instability (negative posterior drawer)
Functional:
- Single-leg hop test (greater than 90% of contralateral)
- Agility testing passed
- Sport-specific drills completed
Timeline: Usually 6-9 months postoperatively, depending on sport and level.
Evidence Base
PCL Avulsion Fixation Outcomes
- Original description of PCL avulsion fracture fixation
- Posterior approach with screw fixation achieves 85-95% good results
- Timing is critical - earlier fixation has better outcomes
Optimal Timing for Fixation
- Fixation within 3 weeks achieves 85-95% good results
- Delayed fixation (over 6 weeks) has lower success rate (60-80%)
- Timing is critical for success
Screw vs Suture Anchor Fixation
- Screw fixation and suture anchor fixation have similar outcomes
- Screw provides compression, suture anchors for small fragments
- Both techniques achieve 85-95% good results
Better Prognosis Than Midsubstance Tear
- PCL avulsion fractures have better outcomes than midsubstance tears
- Bony healing is faster and more reliable
- Always attempt fixation if fragment is adequate
Neurovascular Risk
- Popliteal artery injury risk is less than 5% with proper technique
- Identify and protect neurovascular bundle before dissection
- Use vessel loops to retract, avoid excessive retraction
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Acute PCL Avulsion Fracture
"A 30-year-old man presents to ED after a motor vehicle accident. He was the driver and his knee struck the dashboard. He has a swollen, painful knee and cannot bear weight. Examination shows positive posterior drawer test and posterior sag sign. X-ray shows a PCL avulsion fracture with a 1.5cm fragment displaced posteriorly."
Scenario 2: Comminuted PCL Avulsion
"A 35-year-old athlete presents 2 weeks after a high-energy knee injury. He has persistent instability and cannot return to sport. Examination shows positive posterior drawer and posterior sag. CT scan shows a comminuted PCL avulsion fracture with multiple small fragments (largest 8mm)."
MCQ Practice Points
Better Prognosis
Q: Why do PCL avulsion fractures have better prognosis than midsubstance PCL tears? A: Bony healing is faster and more reliable - PCL avulsion fractures achieve 85-95% good results with proper fixation vs 60-80% for midsubstance tears. Bony healing is more predictable than ligament reconstruction.
Optimal Timing
Q: What is the optimal timing for PCL avulsion fracture fixation? A: Within 3 weeks - Earlier fixation achieves 85-95% good results. Delayed fixation (over 6 weeks) has lower success rate (60-80%) and may require reconstruction instead of fixation.
Surgical Approach
Q: What is the surgical approach for PCL avulsion fracture fixation? A: Posterior approach with patient prone - Popliteal artery and tibial nerve at risk. Must identify and protect neurovascular bundle before any dissection. Use vessel loops to retract.
Fixation Method
Q: What fixation method is used for large PCL avulsion fragments (over 1cm)? A: Screw fixation - Provides compression across fracture. For small fragments (under 1cm) or comminuted, use suture anchors. Both achieve excellent outcomes (85-95% good results).
Neurovascular Risk
Q: What structure is at risk during posterior approach for PCL avulsion fracture? A: Popliteal artery - Lies directly posterior to the tibia, separated by only the popliteus muscle. Must identify and protect before any dissection. Injury risk is less than 5% with proper technique.
Outcomes
Q: What are the outcomes of PCL avulsion fracture fixation? A: 85-95% good results with proper technique and timing (within 3 weeks). Better than midsubstance PCL tears (60-80%). Bony healing is faster and more reliable than ligament reconstruction.
Australian Context
Clinical Practice
- PCL avulsion fractures common in trauma
- Posterior approach standard technique
- Screw or suture anchor fixation
- Early ROM and aggressive PT emphasized
Healthcare System
- Public hospitals handle most cases
- Private insurance covers procedures
- Physiotherapy accessible through public/private
Orthopaedic Exam Relevance
PCL avulsion fractures are a common viva topic. Know that avulsion fractures have better prognosis than midsubstance tears (85-95% vs 60-80%), optimal timing is within 3 weeks, posterior approach with patient prone, popliteal artery at risk, and fixation options (screw for large fragments, suture anchors for small). Be prepared to discuss surgical technique and complications.
PCL AVULSION FRACTURES
High-Yield Exam Summary
Key Anatomy
- •PCL insertion: Posterior tibia, 1-1.5cm below joint line
- •Popliteal artery: Directly posterior to tibia, separated by popliteus muscle
- •PCL function: Primary restraint to posterior tibial translation (95% at 90° flexion)
- •Two bundles: Anterolateral (AL) and posteromedial (PM)
Classification
- •By fragment size: Large (over 1cm) = screw, Small (under 1cm) = suture anchors
- •By displacement: Minimal (under 2mm), Moderate (2-5mm), Severe (over 5mm)
- •By timing: Acute (under 3 weeks), Subacute (3-6 weeks), Chronic (over 6 weeks)
- •Comminuted: Multiple fragments - use suture anchors (2-3), not screw fixation
Treatment Algorithm
- •Acute (under 3 weeks): Surgical fixation (screw or suture anchors) - 85-95% good results
- •Subacute (3-6 weeks): Attempt fixation if mobile - 75-85% good results
- •Chronic (over 6 weeks): May need reconstruction - 60-80% good results
- •Timing is critical - earlier fixation has better outcomes
Surgical Pearls
- •Posterior approach with patient prone
- •Identify popliteal artery and tibial nerve first (critical for safety)
- •Screw fixation for large fragments (compression), suture anchors for small
- •Optimal timing within 3 weeks for best outcomes
Complications
- •Neurovascular injury: Less than 5% (prevent by identifying vessels first)
- •Nonunion: 5-10% (prevent with secure fixation, good apposition)
- •Residual laxity: 10-15% (prevent with anatomic reduction)
- •Stiffness: 5-10% (prevent with early ROM at 2-4 weeks)