Distal Tibial Physeal Injuries

Distal tibial physeal injuries occur in two settings. Standard Salter-Harris fractures behave much as they do at other physes and can occur at any age. The transitional fractures, the juvenile Tillaux and the triplane, are unique to adolescents because the physis closes asymmetrically, and they occur between 12 and 15 years.

Who. Transitional fractures are more common in boys, because their physes close later.

Mechanism. External rotation is the most common mechanism of the transitional fractures.

Against the distal femur. The distal tibial physis contributes 45% of tibial length. Set beside the distal femur, it differs in growth contribution, in arrest risk and in treatment priority.

The closure sequence. The distal tibial physis closes asymmetrically over 18 months. The centre closes first, at approximately 12-14 years; the medial (anteromedial) part follows; the lateral (posterolateral) part closes last, at approximately 14-16 years. Central, medial, lateral: CML.

Why the Tillaux fragment is anterolateral. The juvenile Tillaux occurs when the medial physis has closed but the lateral part is still open. The anterior inferior tibiofibular ligament (AITFL) attaches to the anterolateral epiphysis, so an external rotation force avulses that fragment through the still-open lateral physis, as a Salter-Harris III fracture.

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Standard Salter-Harris fractures. Away from the transitional patterns, the distal tibia follows the usual classification:

• Type I runs through the physis only, and may be occult
• Type II carries a metaphyseal fragment and is the most common pattern in younger children
• Types III and IV are intra-articular and require anatomical reduction

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Juvenile Tillaux. A Salter-Harris III fracture of the anterolateral epiphysis, involving the epiphysis and physis only.

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Triplane. A Salter-Harris IV pattern with fracture lines in three planes:

• Sagittal, through the epiphysis, as in the Tillaux
• Horizontal, through the physis
• Coronal, through the metaphysis, as in a Salter-Harris II

The fragments form two-, three- or four-part patterns:

• Two-part: a sagittal epiphyseal split and a horizontal physeal split, with a large posterolateral fragment
• Three-part: an additional anterolateral fragment, like a Tillaux plus a metaphyseal fragment
• Four-part: more comminuted

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The Salter-Harris III fracture of the medial malleolus is the important non-transitional distal tibial physeal injury. It behaves very differently from the Tillaux and triplane: it carries the highest arrest risk of the Salter-Harris patterns at this site.

The injury. A vertical, intra-articular split through the medial part of the distal tibial epiphysis and physis: Salter-Harris III, or IV if a metaphyseal fragment is included. It is produced by supination-adduction (inversion), the talus shearing off the medial malleolus.

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Why it arrests. The transitional fractures occur near skeletal maturity, so they rarely arrest, and an arrest matters little with so little growth left. The medial malleolar fracture typically occurs in a younger child with substantial growth remaining. It crosses the germinal medial physis and is intra-articular, and periosteum is often interposed medially. A medial bar then tethers the medial physis while the lateral keeps growing, driving progressive ankle varus and shortening.

Management. Achieve anatomical reduction, open if needed, because interposed medial periosteum can block it; a residual physeal gap over 3 mm is the warning sign (Podeszwa). Fix with an epiphyseal screw parallel to the joint, avoiding the physis. Unlike the transitional fractures, follow these children long-term for growth arrest.

History. Establish the mechanism: a twist (external rotation), an inversion or direct trauma. Age tells you whether the patient is in the transitional window.

Examination. Inspect for swelling, ecchymosis and deformity, and palpate for tenderness over the physis, anterolateral in the Tillaux. Range of motion is limited by pain. Document the neurovascular status, and check the fibula for an associated fracture.

Radiographs. AP, lateral and mortise views are standard and may show widening or the fragment. Radiographs show only two planes, and transitional fractures are three-dimensional, so plain films underestimate their displacement.

CT with 3D reconstruction is essential for transitional fractures. It measures the articular step-off against the 2mm threshold, identifies the number of fragments (two-, three- or four-part triplane), and the 3D reconstruction aids surgical planning. On the scan, look for:

• Articular step-off, measured on axial and sagittal images
• The fracture pattern, with every fragment identified
• The extent of physeal involvement
• A fibular injury, which is often associated

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Routine or selective CT. CT clearly changes classification and the operative decision in transitional fractures (Eismann, Nenopoulos), but it irradiates the immature skeleton. Practice therefore varies between CT for all suspected transitional fractures and CT reserved for those that appear displaced on radiographs.

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The adolescent with a twisted, swollen ankle after sport is the classic crossover, and distinguishing a transitional fracture from a "sprain" is the high-yield decision.

The 2mm threshold. Articular displacement greater than 2mm is the accepted trigger for reduction, because intra-articular malunion drives arthritis in a joint that must last a lifetime. Quote 2mm, but know that it is a pragmatic convention derived from articular-step extrapolation and small series; no randomised data define the exact cut-off. Some authors accept up to 2.5 mm in the very mature ankle, while others reduce any visible step in a younger adolescent, so be ready to justify a deviation by the growth remaining and where in the joint the step lies.

Non-displaced (step-off less than 2mm). A below-knee cast for 4-6 weeks, non-weight-bearing initially, with close follow-up and radiographs at 1-2 weeks.

Displaced (step-off greater than 2mm). Attempt closed reduction under fluoroscopy first, with percutaneous pinning if the reduction is acceptable, then cast immobilisation. Open reduction and internal fixation follows if closed reduction fails.

Closed or open for the displaced Tillaux. Closed reduction by internal rotation with percutaneous screw fixation can succeed, but periosteal or AITFL interposition may block it. There is no consensus on how many closed attempts are acceptable before converting to open reduction, and repeated forceful manipulation itself raises physeal-arrest risk.

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Closed reduction and percutaneous fixation (Tillaux). For a displaced Tillaux amenable to closed reduction. Under fluoroscopy, internally rotate the foot to reduce the anterolateral fragment. If the reduction is anatomical on mortise and lateral views, pass a 4.0mm cannulated screw from anterolateral to posteromedial under fluoroscopic guidance, staying within the epiphysis and parallel to the joint.

Open reduction and internal fixation (Tillaux). Indicated when closed reduction fails or a step-off greater than 2mm persists. Through an anterolateral approach, between EHL and EDL, visualise the fracture line, reduce it and hold it with a K-wire. Place cannulated screw(s) parallel to the joint, without crossing the intact physis.

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Open reduction and internal fixation (triplane). For a displaced triplane with a step-off greater than 2mm. It may need an anterolateral and/or anteromedial approach, depending on the fragment pattern. Reduce each fragment anatomically and fix with cannulated screws; the metaphyseal component may require a separate screw.

Fixation principles. Screw fixation is superior to K-wires for compression. Screws should run parallel to the joint and avoid crossing the physis.

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Predict. Leary's data overturn the intuition that the dramatic transitional fractures are the dangerous ones for growth.

Two patterns to watch. In Leary's series Salter-Harris II fractures accounted for 67% of all premature physeal closure (PPC), the largest share of any pattern. The medial malleolar SH III/IV fracture, described above, carries the highest arrest risk. Neither is a transitional fracture.

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Survey. Follow the at-risk child (younger, displaced, SH II, or with a residual gap) with Harris growth-arrest lines. The transverse sclerotic line laid down after the injury should run parallel to the physis; if it converges towards the physis on one side, a bar is forming there. Confirm and map a suspected bar with CT or MRI (the percentage and location of the physeal area involved), and track length and remaining growth with serial scanograms and bone age.

How long to watch. Because these injuries cluster near maturity, growth surveillance is less critical than at other physes, and the value of prolonged Harris-line and scanogram follow-up is debated. Where significant growth remains, monitor.

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Manage. The deformity depends on where the bar lies:

• Medial bar: the ankle tilts into varus
• Lateral bar: valgus
• Central bar: tents the physis and shortens the bone, with leg-length discrepancy as growth remains

A small bar with meaningful growth left is treated by bar resection with interposition, plus correction of any deformity. A large bar, or one near maturity, is treated by completing the epiphysiodesis, managing the leg-length discrepancy (contralateral epiphysiodesis or lengthening), and a corrective osteotomy for the angular deformity.

Immobilisation. A below-knee cast for 4-6 weeks, non-weight-bearing initially, then weight bearing as tolerated at 4-6 weeks. Review at 2 weeks (wound check), 6 weeks (cast removal) and 3 months.

Post-operative CT. Always obtain a post-operative CT: it is mandatory to confirm anatomical reduction, especially for the triplane, and is repeated if there is any concern about reduction quality. Its need and timing are nonetheless debated: it adds radiation, and some surgeons rely on intra-operative fluoroscopy and arthroscopic visualisation instead.

Rehabilitation runs in four phases:

• Phase 1, immobilisation (0-6 weeks): below-knee cast, non-weight-bearing initially, toe wiggling and calf pumps
• Phase 2, early mobilisation (6-10 weeks): cast removal, ankle dorsiflexion and plantarflexion exercises, progressive weight bearing
• Phase 3, strengthening (10-16 weeks): resistance exercises (theraband), proprioception and balance training, gait normalisation
• Phase 4, return to sport (4-6 months): sport-specific training, full range of motion and strength, clearance by the surgeon

Non-displaced fractures do excellently with casting. Displaced fractures that are anatomically reduced do well, with a low risk of arthritis; a malunion with a step greater than 2mm carries a risk of post-traumatic arthritis. Growth arrest is uncommon because these fractures occur near skeletal maturity.

Global epidemiology

• Distal tibial physeal fractures are among the most common physeal injuries, peaking in the adolescent growth spurt (girls roughly 8-14, boys roughly 10-16 years).
• Triplane fractures represent approximately 5-10% of paediatric ankle physeal injuries (6% in the original Cooperman/Spiegel series); Tillaux is rarer and seen in the narrower 12-15 year window.
• Mechanism is overwhelmingly low-energy sport/recreational external rotation; both patterns reflect the ascending (central to medial to lateral) physeal closure sequence rather than a discrete injury entity.

Where guidance converges (society and consensus positions)

There is no genuine guideline-level disagreement on the core principles: the 2 mm threshold, CT for transitional patterns, and anatomical articular reduction are universal. Differences are in access, not recommendation.

Registry note: There is no dedicated implant registry for paediatric transitional ankle fractures (these are low-volume, screw-only constructs). The evidence base is therefore case series and systematic review rather than registry survivorship - this is itself an exam point distinguishing it from arthroplasty topics.

High- vs limited-resource practice variation

• Well-resourced: routine pre-operative CT with 3D reconstruction, arthroscopic-assisted or fluoroscopic percutaneous cannulated-screw fixation, and confirmatory post-operative CT.
• Limited-resource: reliance on plain mortise/lateral radiographs and stress/internal-rotation views, with a lower threshold for open reduction when CT is unavailable to confirm the closed result. The principle (anatomical articular reduction) does not change; only the imaging confirmation does.