Tibial Spine Fractures

Tibial spine fractures, also called tibial eminence fractures, are avulsion fractures of the anterior tibial spine where the ACL inserts. They are the paediatric equivalent of the adult ACL injury, occurring in skeletally immature patients before the ACL is strong enough to tear midsubstance.

Mechanism. The classic mechanism is hyperextension with a valgus force, which arises in several ways:

• Non-contact: jumping or landing with the knee hyperextended, as in soccer, basketball and gymnastics
• Contact: a direct blow to the flexed knee that drives it into hyperextension
• Bicycle accidents, common in children, when the knee strikes the handlebar

Who gets it. The peak age is 8-14 years, in the skeletally immature, with a male predominance of about 2:1. The injury accounts for 3-5% of paediatric knee injuries and is usually unilateral; bilateral fractures are rare.

The tibial spine. The anterior tibial spine, or tibial eminence, is the bony prominence in the anterior intercondylar area of the tibia, lying in the intercondylar notch. Both the anteromedial and posterolateral bundles of the ACL insert here, and the spine shares the ACL's blood supply from the middle genicular artery. It is cartilaginous in children and ossifies with age.

The physis. The proximal tibial physis lies 2-3 cm distal to the tibial spine, and fixation must avoid crossing it (see Growth Plate Protection under Surgical Technique).

Why the bone fails first. In a child the ACL is relatively strong, its collagen already mature, while the tibial spine is cartilaginous, immature and weak. A hyperextension force therefore makes the ACL avulse the tibial spine rather than tear the ligament. How far the fragment displaces depends on the magnitude and direction of that force.

The shift to ligament tears. As the child grows, the tibial spine ossifies and strengthens while the ACL becomes relatively weaker, and the injury pattern moves from avulsion fracture to ligament tear. The transition comes at 14-16 years, with skeletal maturity.

The Meyers-McKeever classification (1959, modified by Zaricznyj in 1977) grades the fracture by displacement on the lateral radiograph, and the grade, together with whether a Type II will reduce, sets the treatment.

Type II is where the decision lies. Because its posterior hinge is intact, a Type II may reduce with knee extension. If the intermeniscal ligament blocks the reduction, the fracture needs arthroscopic debridement and fixation instead.

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History. The child reports the hyperextension injury described above, followed by immediate pain and swelling and an inability to bear weight. The knee may give way, and it locks if the fragment blocks extension.

Look and feel. There is an effusion, which is a haemarthrosis, with an antalgic gait and the knee held in slight flexion. The anterior tibial spine is tender; joint line tenderness suggests a meniscal injury, and MCL tenderness an associated MCL injury.

Movement. Flexion is limited by pain and effusion. Extension is limited if the fragment blocks it, and an extensor lag appears if the extensor mechanism is affected.

Ligament testing. The avulsed tibial spine allows anterior tibial translation, so the tests are those of an ACL injury:

• Lachman test: positive (anterior translation)
• Anterior drawer: positive (anterior translation)
• Pivot shift: may be positive (rotational instability)
• Valgus stress: may be positive if the MCL is injured

Associated injuries. These are the injuries to look for alongside the fracture:

• Meniscal tears in 10-20%, the lateral meniscus more commonly
• MCL injuries in 5-10%
• Bone bruises of the posterolateral tibia and lateral femoral condyle, the kissing contusion
• Extensor mechanism injury (patellar tendon avulsion), which is rare

Radiographs. AP and lateral views of the knee, with oblique views if needed. The lateral view is the one that diagnoses and classifies: it shows the anterior elevation of the fragment from its bed, the displacement (under 3mm in Type I, complete in Type III), the fragment's size and comminution, and its rotation.

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The AP view may show the fragment in the intercondylar notch and screens for an associated plateau injury, but the lateral is diagnostic. When displacement or soft-tissue entrapment remains uncertain, obtain a true lateral and an MRI.

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CT. CT is not routine but is helpful in complex cases and for surgical planning, defining fragment size and comminution, articular involvement and any associated fracture, and so the fixation strategy. It is most useful when plain films underestimate rotation or when the choice of fixation depends on fragment size and comminution. Three-dimensional reconstruction helps with complex comminution (Type IV), with fragment rotation and with preoperative planning.

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MRI. MRI is not routine but is indicated when associated injuries are suspected: meniscal tears, MCL injuries, bone bruises in the kissing contusion pattern and cartilage injuries. It also shows the ACL fibres, which are usually intact, and their relationship to the fragment, and it defines intermeniscal-ligament entrapment that can block reduction.

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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 elevated anterior fragment 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.

Before choosing, classify the fracture, assess a Type II for reducibility and check for associated meniscal and MCL injuries.

Non-operative treatment. Type I fractures, and Type II fractures that reduce with extension and are stable, are treated in an extension cast for 4-6 weeks. The child is non-weight-bearing initially, for 2-3 weeks, then progressively weight-bearing (3-4 weeks), and range of motion starts when the cast comes off. Outcomes are excellent for Type I and good for a reducible Type II. The exact immobilisation angle is debated; the section on Loss of Reduction During Non-Operative Treatment sets out the argument.

Follow-up in the cast. A radiograph at 2 weeks checks the position and one at 4-6 weeks checks healing. The cast is removed when the fracture has healed, at 4-6 weeks.

Surgical indications. Surgery is indicated as follows.

Absolute

• Type III (complete displacement)
• Type IV (comminuted)
• Type II that will not reduce, blocked by the intermeniscal ligament

Relative

• Type II with persistent instability after reduction
• An associated meniscal tear requiring repair
• The high-demand athlete

Timing. Operate within 1-2 weeks. That allows the swelling to resolve, but comes before the fragment becomes fixed.

The operation. Type III and IV fractures are reduced and fixed arthroscopically, with suture or screw, and opened if arthroscopic reduction fails. Range of motion starts early after surgery.

Arthroscopic reduction with suture fixation through transosseous tunnels is the gold standard for Type III-IV fractures. Screw fixation is acceptable but suture fixation is preferred, and open reduction is reserved for complex cases.

Arthroscopic Suture FixationScrew FixationOpen Reduction

Why it is preferred. Suture fixation needs no hardware removal and allows early range of motion; the arthroscope gives excellent visualisation, and the complication rate is low.

Set-up. The patient lies supine on a standard table with a thigh tourniquet and a leg holder or lateral post, in a standard arthroscopy set-up. The anterolateral portal is for viewing, the anteromedial portal for working, and a superomedial portal is an optional outflow.

Steps.

1. Diagnostic arthroscopy: assess the fragment, meniscus and cartilage
2. Debride the intermeniscal ligament if it blocks reduction
3. Reduce the fragment with a probe or shaver
4. Prepare the fragment bed, debriding to bleeding bone
5. Pass 2-3 sutures through the fragment
6. Create 2-3 transosseous tunnels, avoiding the physis
7. Pass the sutures through the tunnels
8. Tie the sutures over the bone bridge with the knee in extension
9. Confirm reduction and stability

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Look before you reduce. Probe the fragment's integrity and mobility, then inspect both menisci and the intermeniscal ligament before choosing screw or suture fixation. The posterior horn of a meniscus can be torn or trapped beneath the avulsed fragment, and forcing the fragment down may incarcerate or damage it, so remove interposed tissue before accepting the reduction.

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The bed. Haematoma and fibrous tissue are cleared to expose bleeding cancellous bone, preserving the fragment and its ACL attachment. Reduction cannot be anatomic while the bed, the anterior horn or the intermeniscal ligament remains interposed.

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Sutures and tunnels. Use No. 2 non-absorbable suture (Ethibond or Fiberwire), passed through the ACL insertion on the fragment and then through the transosseous tunnels. The tunnels stay proximal to the physis (see Growth Plate Protection), and 2-3 of them give stability. Before the fixation is final, cycle the knee and inspect for anterior notch impingement or loss of terminal extension.

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Anchors instead of tunnels. Sutures passed around the ACL and fragment can instead be tensioned into a metaphyseal knotless anchor, which avoids transphyseal tunnels. Confirm compression through flexion and extension, and make sure the anchor does not violate the physis. Suture-bridge constructs combine anchors, crossing sutures and cortical fixation to compress the fragment broadly.

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When to use it. A screw suits a large single fragment (Type III), a fracture where arthroscopic suture fixation is not feasible, or surgeon preference.

Technique.

1. Reduce arthroscopically or open
2. Place a guide wire in the centre of the fragment
3. Insert a cannulated, partially threaded 3.5-4.5mm screw, countersunk if needed
4. Confirm reduction and stability

The trade-off. A screw gives strong fixation with compression across the fracture, by a familiar technique. Against that, the hardware has to be removed at 6-12 months, the screw risks comminuting the fragment, and a prominent screw may limit range of motion.

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When to open. Open reduction is for a failed arthroscopic reduction, complex comminution (Type IV), or associated injuries that need an open approach.

Approach. Through an anterior midline or parapatellar incision, the patella is retracted laterally and the intercondylar notch exposed. The fragment is reduced under direct vision and fixed with screws or sutures.

The trade-off. Direct vision handles complex patterns and associated injuries, at the price of a more invasive operation, a slower recovery and a higher complication risk. For arthrofibrosis specifically, the Farinelli meta-analysis found no significant difference between arthroscopic and open fixation (see Complications).

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Arthrofibrosis. Stiffness is the most common complication. The Farinelli meta-analysis (49 studies, 2,017 patients) pooled an incidence of 7.4% after ARIF and 10.3% after ORIF, with no significant difference between them. Other reviews report 16-21%, so treat it as roughly one knee in ten, not a precise figure.

Treating the stiff knee. Established arthrofibrosis is managed with manipulation under anaesthesia and arthroscopic lysis of adhesions. The two go together: Vander Have's series in the Evidence Base is the reason manipulation is not performed alone.

Residual laxity. Farinelli recorded translation over 3mm in roughly 3-4% of pooled cases, though instrumented testing finds mild laxity far more often, and that figure counts the laxity a surgeon chose to report. Mild laxity is usually asymptomatic and does not affect function; symptomatic instability is rarer still. If it is symptomatic, the options are revision fixation or, if needed, ACL reconstruction.

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Nonunion. When it occurs, it is treated by revision fixation, with bone graft if needed.

Growth disturbance. Where there is concern, monitor the child until skeletal maturity.

The first weeks. A hinged knee brace is locked in extension for 2-4 weeks and the child is non-weight-bearing for the first 2-3 weeks. Quadriceps sets and straight leg raises start immediately, and the brace is unlocked for passive range of motion at 2-4 weeks.

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Return to sport. Return comes when strength and range of motion are normal and the criteria below are met, usually at 3-6 months after surgery depending on the sport and level. 80-90% return to their pre-injury level, the outcome depending on age, sport level and compliance with rehabilitation.

• Full range of motion, equal to the contralateral side
• Quadriceps strength greater than 90% of the contralateral side
• No effusion
• No instability: negative Lachman and pivot shift
• Single-leg hop test greater than 90% of the contralateral side
• Agility testing passed and sport-specific drills completed

Prevention. Primary prevention rests on proper landing technique, with the knee flexed rather than hyperextended, together with quadriceps and hamstring strength training, balance and proprioception training, and sport-specific conditioning. After an injury, complete rehabilitation before returning to sport and continue strength and conditioning work; bracing is controversial and may not prevent reinjury.

Outcomes are excellent with proper treatment. Non-operatively treated Type I-II fractures give 90-95% good or excellent results, and surgically treated Type III-IV fractures 85-95%. At 5-10 years, 85-90% maintain good results.

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.

Related pages: Paediatric ACL Injury is the sibling diagnosis and the one this fracture is the childhood equivalent of — the same mechanism, the same haemarthrosis, and the decision between them is made on the radiograph before the MRI; ACL Injuries for the adult mid-substance tear and for the reconstruction that a small minority of these knees eventually need — and note the distinction this page turns on, that here the ligament is in continuity but plastically elongated, so anatomic bony reduction cannot shorten it; Knee Arthrofibrosis is the dominant complication and carries the staged management in full, including why manipulation must be combined with lysis of adhesions rather than performed alone; Meniscus Tears and Discoid Meniscus matter here for a specific reason — entrapment of the anterior horn or the intermeniscal ligament under the fragment is the commonest block to closed reduction, and the Najdi series found it in half of its patients; MCL Injuries for the concomitant ligamentous injury that turns mild residual laxity into symptomatic instability; Physeal Injuries: Salter-Harris and Proximal Tibial Physeal Injuries for the growth plate that constrains every implant choice, and Distal Femoral Physeal Injuries because the iatrogenic distal femoral fracture caused by manipulation is a physeal injury with the highest arrest risk in the body; Tibial Plateau Fractures is the adult intra-articular differential in the same region; Osteochondral Defects of the Knee for the other cause of a paediatric haemarthrosis with a fragment on the film; and Return to Sport Criteria for the functional testing that should govern clearance rather than time alone.

• 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 and clusters with malreduction, fragment resorption, inadequate fixation, or a missed concomitant ligamentous injury rather than with the plastic-elongation mechanism alone. Pooled series record translation over 3 mm as a reported complication in only about 3-4 percent, which almost certainly understates objective laxity because it counts what surgeons chose to report rather than what arthrometry would find in everyone.
• 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.