PCL Avulsion Fractures

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.

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%)

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

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)

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)

Differential Diagnosis

The posterior tibial fragment is the diagnostic lesion, but two secondary avulsion signs on plain films flag the concomitant injuries that change the operation. Both are easily confused with the classic (lateral, ACL-associated) Segond fracture listed in the differential above, so they are worth learning as a set.

Reverse Segond Fracture

• What it is: a small cortical avulsion off the medial tibial plateau margin, at the attachment of the deep medial collateral ligament / medial capsule — the mirror image of the classic lateral Segond fleck.
• Why it matters: the reverse Segond is strongly associated with PCL injury and a medial meniscus tear, whereas the classic lateral Segond signals ACL injury. Spotting a medial-margin fleck on the AP film should trigger a deliberate search for the posterior tibial PCL avulsion and MRI assessment of the medial meniscus.
• Mechanism: valgus with external rotation, distinct from the posterior-drawer dashboard mechanism of the isolated PCL fragment, but often part of the same high-energy event.

Arcuate (Fibular Styloid) Sign

• An avulsion fleck off the fibular styloid at the arcuate-complex insertion signals a posterolateral corner (PLC) injury, which co-exists with PCL injury in a meaningful minority of cases.
• Full PLC evaluation and reconstruction is owned by the dedicated posterolateral-corner-injuries topic; here the teaching point is that a tiny fibular-head fleck alongside a posterior tibial fragment means "not an isolated PCL avulsion — look for combined instability."

The guidelines table above names the "Burks / Trickey" open posterior approach, but the operative point examiners are really testing is how the popliteal neurovascular bundle is kept out of harm's way — that is a matter of which interval you choose, not just where the skin incision runs.

The Approaches by Name

• Trickey posterior (midline) approach: a lazy-S popliteal incision giving direct access to the posterior capsule. Because it crosses the popliteal fossa, it requires formal identification and mobilisation of the popliteal vessels and tibial nerve, so it is generally reserved for combined injuries needing wide exposure.
• Burks–Schaffer posteromedial approach: a more medial incision that uses the interval between the medial head of gastrocnemius and semimembranosus, avoiding the midline popliteal dissection.
• Lobenhoffer / posteromedial inverted-L approach: a widely used modern variant giving the same posteromedial window onto the PCL facet of the posterior tibia.

The Safe Interval (the high-yield principle)

The posteromedial approaches share one protective manoeuvre: develop the plane medial to the medial head of gastrocnemius, then retract that muscle belly laterally. The retracted medial gastrocnemius then sits as a muscular shield between the operative field and the popliteal artery, vein and tibial nerve, so the posterior tibial fragment can be reduced and fixed without dissecting directly onto the vessels. This is precisely why a posteromedial route is generally preferred over a direct midline popliteal dissection for the isolated tibial avulsion.

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

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.

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

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.

Global Epidemiology

• PCL injuries account for roughly 3-20% of acute knee ligament injuries; isolated bony tibial avulsions are a small subset.
• In pooled series, motor vehicle and motorcycle trauma cause the majority of tibial-sided avulsions (around 68% in the largest systematic review, with motorcycle crashes dominant in many Asian cohorts).
• High-energy mechanisms drive a male predominance and a 20-40 year peak. In limited-resource and high-motorcycle-density regions the absolute burden is higher.

Side-by-Side Guidance

There is no high-level guideline mandating a single technique. Consensus across societies is: displaced fragments should be reduced and stably fixed, repair is preferred over reconstruction when a fixable fragment exists, and concomitant ligament/meniscal injury must be addressed.

Registry & Resource Notes

• No dedicated arthroplasty-style registry tracks PCL avulsion fixation; evidence is limited to Level II RCTs and Level IV series/systematic reviews.
• High-resource settings: increasing use of arthroscopic suture-button/suture-bridge fixation to avoid open popliteal dissection, despite longer operative time and higher cost (Sundararajan RCT).
• Limited-resource settings: open posterior screw or staple fixation remains the workhorse - faster, cheaper, and not dependent on advanced arthroscopic instrumentation.