Tibial Spine Fractures

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).

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%)

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

Classification System

Meyers-McKeever Classification (1959, modified by Zaricznyj 1977):

Key point: Type II may be reducible with knee extension (anterior hinge intact). If blocked by intermeniscal ligament, requires arthroscopic debridement and fixation.

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)

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)

The acutely swollen, haemarthrosis knee in a child has a focused differential. The tibial spine fracture is distinguished by the avulsed eminence on the lateral radiograph.

Non-operative care of a Type I or a reduced Type II fracture is an active, monitored process, not "cast and forget" — this answers the viva follow-up "What if it displaces to Type II in the cast?"

• Interval radiographs are mandatory. Films at roughly one to two weeks confirm the fragment has held its position; a marginally reduced Type II can re-elevate within the cast as swelling settles.
• Immobilisation angle is debated and matters. Near-full extension helps seat the anterior hinge of a Type II (the femoral notch presses the fragment down), but frank hyperextension can tension the ACL and lift the fragment, so a position of near-extension (commonly about 10 to 20 degrees of flexion) is often chosen to balance these effects.
• Loss of reduction changes the plan. If interval imaging shows progression to a displaced Type II or III, or a fragment now blocked by the interposed intermeniscal (transverse) ligament, abandon closed treatment and convert to arthroscopic reduction and fixation. Accepting a malunited, elevated fragment risks a mechanical extension block (the prominent fragment impinges in the intercondylar notch), residual laxity, and secondary arthrofibrosis.

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

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.

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

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.

Global Epidemiology

• Incidence: ~3 per 100,000 per year; peak age 8-14 years; male predominance (~2:1).
• Represents roughly 2-5% of paediatric knee injuries with haemarthrosis; rising with youth sport participation.
• Bony ACL avulsion equivalent in the skeletally immature knee; adults more often tear the ACL mid-substance.

Society Guidance (Side by Side)

There is no formal single-society guideline dedicated to tibial spine fractures; the table summarises principles endorsed across major bodies and the Tibial Spine Research Interest Group consensus.

Registries and Practice Variation

• Joint registries (NJR, AJRR, AOANJRR, SHAR) do not track tibial spine fixation; they are relevant only for the rare late ACL reconstruction or arthroplasty after malreduction and post-traumatic arthritis.
• High-resource settings: arthroscopic reduction with suture fixation is the prevailing standard, enabling early motion.
• Limited-resource settings: open reduction and internal fixation (screw or suture over bone bridge) remains common and effective where arthroscopy or implants are unavailable; outcomes are good when reduction is anatomic and rehabilitation is supervised.

The topic repeatedly notes that mild anterior laxity is common even when the fragment heals perfectly, but the reason deserves explanation because it is a favourite examiner probe. The anterior cruciate ligament does not fail cleanly at the instant the eminence avulses: it is first plastically (interstitially) elongated — the ligament stretches beyond its elastic limit as the bony attachment peels off. Restoring the bony fragment to its bed therefore restores the footprint but cannot shorten an already-lengthened ligament, so a degree of anterior translation may persist.

• Instrumented testing detects it more than patients do: side-to-side differences on Lachman and KT-1000 arthrometry are found more often than the child reports any symptom. Most such laxity is mild, functionally silent, and does not require later ACL reconstruction — consistent with the excellent Lysholm scores and absence of clinical laxity reported in the operative series in the Evidence Base.
• Clinically important laxity is the minority (the roughly 10-15% figure used throughout this topic) and clusters with malreduction, fragment resorption, inadequate fixation, or a missed concomitant ligamentous injury rather than with the plastic-elongation mechanism alone.
• Do not conflate with a mid-substance ACL tear — the primary treatment of a torn ACL and its reconstruction are covered on the dedicated ACL topics; here the ligament is in continuity but lengthened.