TIBIAL SPINE FRACTURES
Pediatric ACL Equivalent | Meyers-McKeever Classification | Arthroscopic Fixation
MEYERS-MCKE EVER CLASSIFICATION
Critical Must-Knows
- Pediatric ACL equivalent - tibial spine fracture in children = ACL injury in adults
- Meyers-McKeever classification guides treatment: Type I-II non-operative, Type III-IV surgical
- Intermeniscal ligament may block reduction in Type II and III - requires arthroscopic debridement
- Arthroscopic suture fixation is gold standard for Type III-IV (avoids hardware removal)
- Excellent outcomes with proper treatment: 85-95% good results, low complication rate
Examiner's Pearls
- "Tibial spine fracture = pediatric ACL injury - mechanism is hyperextension with valgus
- "Type II may be reducible with extension - if blocked by intermeniscal ligament, needs surgery
- "Arthroscopic suture fixation avoids hardware removal and allows early ROM
- "Complications: arthrofibrosis (5-10%), residual laxity (10-15%), growth disturbance (rare)
Clinical Imaging
Imaging Gallery
Critical Tibial Spine Exam Points
Pediatric ACL Equivalent
Tibial spine fracture in children = ACL injury in adults. Same mechanism (hyperextension with valgus), same instability pattern (anterior translation, pivot shift). Peak age 8-14 years. Meyers-McKeever classification guides treatment based on displacement.
Classification Determines Treatment
Type I-II: Non-operative (extension cast). Type III-IV: Surgical (arthroscopic or open fixation). Type II may be reducible with extension - if blocked by intermeniscal ligament, needs arthroscopic debridement and fixation.
Arthroscopic Suture Fixation
Gold standard for Type III-IV: Arthroscopic reduction and suture fixation through transosseous tunnels. Avoids hardware removal, allows early ROM, excellent outcomes (85-95% good results). Screw fixation alternative but requires removal.
Complications to Watch
Arthrofibrosis (5-10%): Most common - prevent with early ROM. Residual laxity (10-15%): May require revision. Growth disturbance (rare): Avoid crossing physis with fixation. Nonunion (rare): Usually with inadequate fixation.
Tibial Spine Fractures - Quick Decision Guide
| Type | Displacement | Reducible? | Treatment |
|---|---|---|---|
| Type I | Less than 3mm | N/A - minimal | Extension cast 4-6 weeks |
| Type II | Anterior elevation | May be reducible | Attempt closed reduction, cast if reducible |
| Type III | Complete displacement | No - blocked | Surgical fixation (arthroscopic preferred) |
| Type IV | Comminuted | No | Surgical fixation (arthroscopic preferred) |
MACSTibial Spine Fracture Classification
Memory Hook:Meyers-McKeever classification for ACL equivalent - Cast or Surgery based on displacement, Suture fixation is gold standard!
SURGSurgical Indications
Memory Hook:Surgery for Severe displacement, Unreducible fractures, Residual laxity, with Growth concern avoidance!
ALANComplications
Memory Hook:Complications: Arthrofibrosis (most common), Laxity (residual), Arthritis (long-term), Nonunion (rare)!
Overview and Epidemiology
Tibial spine fractures (also called tibial eminence fractures) are avulsion fractures of the anterior tibial spine where the ACL inserts. These fractures represent the pediatric equivalent of ACL injuries in adults, occurring in skeletally immature patients before the ACL is strong enough to tear midsubstance.
Mechanism of Injury
Hyperextension with valgus force is the classic mechanism:
- Non-contact: Jumping/landing with knee hyperextension
- Contact: Direct blow to flexed knee causing hyperextension
- Bicycle accidents: Common in children (knee strikes handlebar)
- Sports: Soccer, basketball, gymnastics (landing with hyperextension)
The ACL inserts on the anterior tibial spine. In children, the bone is weaker than the ligament, so the ACL avulses the tibial spine rather than tearing midsubstance (as in adults).
Why Children Get Tibial Spine Fractures
In children, bone is weaker than ligament. The ACL insertion site (tibial spine) is cartilaginous and weak. Hyperextension force causes the ACL to avulse the tibial spine rather than tear midsubstance. This is why ACL injuries in children under 14 are almost always tibial spine fractures, not ligament tears.
Epidemiology
- Age: Peak 8-14 years (skeletally immature)
- Gender: Male predominance (2:1 ratio)
- Incidence: 3-5% of pediatric knee injuries
- Laterality: Usually unilateral, bilateral rare
- Associated injuries: Meniscal tears (10-20%), MCL injuries (5-10%)
Anatomy and Pathophysiology
Tibial Spine Anatomy
The anterior tibial spine (tibial eminence) is the bony prominence in the intercondylar notch where the ACL inserts:
- Location: Anterior intercondylar area of tibia
- Structure: Cartilaginous in children, ossifies with age
- ACL insertion: Anteromedial and posterolateral bundles attach here
- Blood supply: Middle genicular artery (same as ACL)
- Growth plate: Proximal tibial physis is 2-3cm distal - avoid crossing with fixation
Pathophysiology
In children, bone is weaker than ligament:
- ACL is relatively strong (mature collagen)
- Tibial spine is cartilaginous and weak (immature bone)
- Hyperextension force → ACL avulses tibial spine (not ligament tear)
- Displacement depends on force magnitude and direction
As children age:
- Tibial spine ossifies and strengthens
- ACL becomes relatively weaker
- Mechanism shifts from avulsion fracture to ligament tear
- Transition age: 14-16 years (skeletal maturity)
Growth Plate Considerations
The proximal tibial physis is 2-3cm distal to the tibial spine. Fixation must avoid crossing the physis to prevent growth disturbance. Use transosseous tunnels that stay proximal to the physis, or use suture anchors in the tibial spine itself.
Classification System
Meyers-McKeever Classification (1959, modified by Zaricznyj 1977):
| Type | Description | Displacement | Radiographic Finding |
|---|---|---|---|
| Type I | Minimal displacement | Less than 3mm elevation | Minimal anterior elevation on lateral X-ray |
| Type II | Anterior hinge intact | Anterior 1/3-1/2 elevated | Anterior elevation with posterior hinge visible |
| Type III | Complete displacement | No contact with bed | Fragment completely separated, rotated |
| Type IV | Comminuted | Multiple fragments | Comminuted fragment, may be rotated |
Key point: Type II may be reducible with knee extension (anterior hinge intact). If blocked by intermeniscal ligament, requires arthroscopic debridement and fixation.
Classification Systems
Meyers-McKeever Classification (Standard)
Type I: Minimal displacement (less than 3mm)
- Anterior edge slightly elevated
- Posterior hinge intact
- Treatment: Extension cast 4-6 weeks
Type II: Anterior hinge intact
- Anterior 1/3 to 1/2 elevated
- Posterior hinge maintains contact
- Treatment: Attempt closed reduction with extension, cast if reducible
Type III: Complete displacement
- Fragment completely separated
- No contact with tibial bed
- May be rotated
- Treatment: Surgical fixation (arthroscopic or open)
Type IV: Comminuted
- Multiple fragments
- May be rotated or displaced
- Treatment: Surgical fixation (arthroscopic or open)
This classification guides treatment decisions based on displacement and reducibility.
Clinical Assessment
History
Mechanism: Hyperextension with valgus force
- Jumping/landing with knee hyperextension
- Direct blow to flexed knee
- Bicycle accident (knee strikes handlebar)
- Sports: Soccer, basketball, gymnastics
Symptoms:
- Immediate pain and swelling
- Inability to bear weight
- Knee "giving way" (instability)
- Locking (if fragment blocks extension)
Physical Examination
Inspection:
- Knee effusion (hemarthrosis)
- Antalgic gait
- Knee held in slight flexion
Palpation:
- Tenderness over anterior tibial spine
- Joint line tenderness (if meniscal injury)
- MCL tenderness (if associated MCL injury)
Range of Motion:
- Limited flexion (pain, effusion)
- Limited extension (if fragment blocks)
- Extensor lag (if extensor mechanism affected)
Ligament Testing:
- Lachman test: Positive (anterior translation)
- Anterior drawer: Positive (anterior translation)
- Pivot shift: May be positive (rotational instability)
- Valgus stress: May be positive (if MCL injured)
Clinical Examination Key Point
Lachman test is positive in tibial spine fractures (same as ACL injury). The avulsed tibial spine allows anterior tibial translation. This is why tibial spine fractures are the pediatric ACL equivalent - same instability pattern, different injury mechanism.
Associated Injuries
- Meniscal tears: 10-20% (lateral meniscus more common)
- MCL injuries: 5-10%
- Bone bruises: Posterolateral tibia, lateral femoral condyle (kissing contusion)
- Extensor mechanism: Rare (patellar tendon avulsion)
Investigations
Standard X-ray Protocol
Views: AP and lateral knee. Oblique views if needed.
Key findings:
- Lateral view: Best for diagnosis and classification
- Anterior elevation: Fragment elevated from tibial bed
- Fragment size: Assess size and comminution
- Displacement: Measure displacement (Type I less than 3mm, Type III complete)
- Rotation: Assess fragment rotation
Lateral view is critical - shows displacement and classification.
AP view: May show fragment in intercondylar notch, but lateral is diagnostic.
Management Algorithm
Management Pathway
Tibial Spine Fracture Management
Determine Meyers-McKeever type. Assess reducibility for Type II. Check for associated injuries (meniscus, MCL).
Extension cast for 4-6 weeks. Non-weight bearing initially. Progressive weight bearing and ROM after cast removal.
Try closed reduction with knee extension. If reducible and stable, cast. If blocked by intermeniscal ligament, surgical.
Arthroscopic reduction and fixation (suture or screw). Open reduction if arthroscopic fails. Early ROM postoperatively.
Surgical Technique
Gold Standard Technique
Advantages:
- No hardware removal needed
- Allows early ROM
- Excellent visualization
- Low complication rate
Patient Positioning:
- Supine on standard table
- Tourniquet on thigh
- Leg holder or lateral post
- Standard arthroscopy setup
Portals:
- Anterolateral: Viewing portal
- Anteromedial: Working portal
- Superomedial: Optional outflow
Steps:
- Diagnostic arthroscopy (assess fragment, meniscus, cartilage)
- Debride intermeniscal ligament if blocking reduction
- Reduce fragment with probe or shaver
- Prepare fragment bed (debride to bleeding bone)
- Pass sutures through fragment (2-3 sutures)
- Create transosseous tunnels (2-3 tunnels, avoid physis)
- Pass sutures through tunnels
- Tie sutures over bone bridge (knee in extension)
- Confirm reduction and stability
Suture technique: Use No. 2 non-absorbable suture (Ethibond or Fiberwire). Pass through ACL insertion on fragment, then through transosseous tunnels.
Tunnel placement: Stay proximal to physis (2-3cm distal to joint line). Use 2-3 tunnels for stability.
Growth Plate Protection
Avoid crossing the proximal tibial physis with fixation. The physis is 2-3cm distal to the joint line. Use transosseous tunnels that stay proximal to the physis, or use suture anchors in the tibial spine itself. Crossing the physis can cause growth disturbance (rare but devastating).
Complications
| Complication | Incidence | Risk Factors | Prevention/Management |
|---|---|---|---|
| Arthrofibrosis | 5-10% | Delayed ROM, prolonged immobilization | Early ROM (2-4 weeks), aggressive PT |
| Residual laxity | 10-15% | Malreduction, inadequate fixation | Anatomic reduction, secure fixation |
| Nonunion | Less than 5% | Inadequate fixation, poor reduction | Secure fixation, bone bed preparation |
| Growth disturbance | Less than 1% | Crossing physis with fixation | Avoid physis, use proximal tunnels |
| Hardware issues | 5-10% (screw) | Prominent hardware, need for removal | Use suture fixation to avoid removal |
| Arthritis | Long-term risk | Malreduction, persistent instability | Anatomic reduction, restore stability |
Arthrofibrosis
Most common complication (5-10%):
- Cause: Prolonged immobilization, delayed ROM
- Prevention: Early ROM (2-4 weeks), aggressive PT
- Management: Manipulation under anesthesia, arthroscopic lysis of adhesions
Residual Laxity
10-15% incidence:
- Cause: Malreduction, inadequate fixation, fragment resorption
- Prevention: Anatomic reduction, secure fixation
- Management: Revision fixation if symptomatic, ACL reconstruction if needed
Nonunion
Less than 5% incidence:
- Cause: Inadequate fixation, poor reduction, fragment devascularization
- Prevention: Secure fixation, bone bed preparation
- Management: Revision fixation with bone graft if needed
Postoperative Care
Immediate Postoperative
- Immobilization: Hinged knee brace locked in extension (2-4 weeks)
- Weight bearing: Non-weight bearing initially (2-3 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 ROM (0-90 degrees)
- Progressive weight bearing (partial to full)
- Stationary bike (when ROM allows)
- Continue quadriceps strengthening
Weeks 4-6:
- Full ROM
- Full weight bearing
- Progressive strengthening
- Balance and proprioception
Weeks 6-12:
- Sport-specific training
- Return to sport (when strength and ROM normal)
- Continue PT for 3-6 months
Return to Sport
Criteria:
- Full ROM (equal to contralateral)
- Quadriceps strength greater than 90% of contralateral
- No instability (negative Lachman, pivot shift)
- Functional testing passed (hop test, agility)
Timeline: Usually 3-6 months postoperatively.
Outcomes and Prognosis
Overall Outcomes
Excellent outcomes with proper treatment:
- Type I-II (non-operative): 90-95% good/excellent results
- Type III-IV (surgical): 85-95% good/excellent results
- Long-term (5-10 years): 85-90% maintain good results
Functional Outcomes
Return to sport:
- Timeline: 3-6 months postoperatively
- Rate: 80-90% return to pre-injury level
- Factors: Age, sport level, rehabilitation compliance
Long-Term Prognosis
Residual laxity:
- 10-15% have some residual anterior 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
Growth disturbance:
- Rare (less than 1%) with proper technique
- Avoid crossing physis with fixation
- Monitor until skeletal maturity if concern
Prevention and Return to Sport
Prevention
Primary prevention:
- Proper landing technique (knee flexion, not hyperextension)
- Strength training (quadriceps, hamstrings)
- Balance and proprioception training
- Sport-specific conditioning
Secondary prevention (after injury):
- Complete rehabilitation before return to sport
- Bracing (controversial - may not prevent reinjury)
- Continued strength and conditioning
Return to Sport Criteria
Clinical:
- Full ROM (equal to contralateral)
- Quadriceps strength greater than 90% of contralateral
- No effusion
- No instability (negative Lachman, pivot shift)
Functional:
- Single-leg hop test (greater than 90% of contralateral)
- Agility testing passed
- Sport-specific drills completed
Timeline: Usually 3-6 months postoperatively, depending on sport and level.
Evidence Base
Meyers-McKeever Classification
- Original classification system (Type I-III)
- Type I-II non-operative outcomes excellent
- Type III surgical outcomes good with proper fixation
Arthroscopic Suture Fixation Outcomes
- 85-95% good/excellent outcomes with arthroscopic suture fixation
- Low complication rate (5-10% arthrofibrosis)
- No hardware removal needed with suture technique
Screw vs Suture Fixation
- Suture fixation and screw fixation have similar outcomes
- Suture fixation avoids hardware removal
- Both techniques achieve 85-95% good results
Long-Term Outcomes
- Long-term outcomes (5-10 years): 85-90% good/excellent results
- Residual laxity in 10-15% but usually asymptomatic
- Low arthritis risk with proper treatment
Growth Disturbance Risk
- Growth disturbance is rare (less than 1%)
- Risk increased with screw fixation crossing physis
- Suture fixation has lower risk
Exam Viva Scenarios
Practice these scenarios to excel in your viva examination
Scenario 1: Non-Displaced Fracture
"A 10-year-old boy presents after falling off a bicycle. Knee is swollen. X-ray shows Meyers-McKeever Type I tibial spine fracture."
Scenario 2: Displaced Fracture (Type III)
"A 12-year-old female gymnast lands awkwardly. X-ray shows a Type III tibial spine fracture (completely displaced)."
Scenario 3: Complication (Arthrofibrosis)
"A patient returns 3 months after fixation of a tibial spine fracture with a 15-degree extension deficit."
MCQ Practice Points
Most Common Complication
Q: What is the most common complication following tibial spine fracture fixation? A: Arthrofibrosis (5-10%) - Stiffness is more common than instability or nonunion. Prevention requires early ROM.
Pathomechanics
Q: Why do children sustain tibial spine fractures instead of ACL tears? A: Bone is weaker than ligament - The cartilaginous tibial spine avulses before the collagen of the ACL fails midsubstance.
Surgical Indication
Q: What is the absolute indication for surgery in Meyers-McKeever classification? A: Type III (Complete displacement) - Also Type II if reducible but blocked by meniscus (intermeniscal ligament).
ACL Function Post-Fixation
Q: How does ACL function compare between anatomically healed tibial spine fractures and native ACL? A: Normal function expected - Studies show 95% of patients achieve normal Lachman and KT-1000 testing when healed in anatomic position.
Intermeniscal Ligament
Q: What structure may block reduction of a displaced tibial spine fracture? A: Intermeniscal ligament (transverse ligament) - It can become interposed between the fragment and its bed, preventing closed reduction.
Australian Context
AOA Guidelines:
- Tibial spine fractures should be managed in consultation with a Paediatric Orthopaedic Surgeon.
- High index of suspicion for associated meniscal pathology (MRI recommended if mechanical symptoms).
- Early mobilisation (within 2-4 weeks) is encouraged to prevent stiffness, consistent with modern ACL rehabilitation protocols.
AOANJRR:
- Not applicable for primary fixation, but relevant if failure requires late ACL reconstruction or arthroplasty (rare).
TIBIAL SPINE FRACTURES
High-Yield Exam Summary
Key Concepts
- •Pediatric ACL Equivalent
- •Meyers-McKeever Classification
- •Hyperextension + Valgus mechanism
- •Lachman positive (anterior laxity)
Classification (Meyers-McKeever)
- •Type I: Non-displaced → Extension Cast
- •Type II: Hinge intact → Reduce/Cast or Surgery
- •Type III: Complete → Surgery
- •Type IV: Comminuted → Surgery
Surgical Goals
- •Anatomic reduction
- •Stable fixation (Suture > Screw)
- •Avoid Physis (Growth plate protection)
- •Early ROM (Prevent arthrofibrosis)
Complications
- •Arthrofibrosis (Most common)
- •Residual Laxity (Usually asymptomatic)
- •Growth Disturbance (Rare)
- •Nonunion (Rare)
Pearl
- •Intermeniscal ligament often blocks reduction
- •Lateral meniscus tear is most common associated injury
- •Lateral X-ray is diagnostic view
- •Arthroscopic suture fixation is gold standard