Tibial eminence (spine) fracture

A bony avulsion of the anterior cruciate ligament from the intercondylar eminence. In children (typically 8–14 years) the incompletely ossified eminence fails before the ligament, so this is the paediatric equivalent of an ACL tear; in adults it occurs with high-energy injuries and often with other ligament or meniscal damage. The fragment can be held up by the anterior horn of the medial meniscus or the intermeniscal ligament trapped beneath it.

Mechanism

Hyperextension or a valgus–rotation twist with the foot planted: a bicycle fall, skiing, football. In adults also a direct blow in road traffic accidents.

Clinical findings

• Painful, swollen knee with a tense haemarthrosis; the child will not bear weight or straighten the knee.
• A block to full extension suggests a displaced fragment or interposed meniscus.
• Lachman test is hard to perform acutely; check the collaterals and the posterolateral corner.

Imaging

• AP and lateral of the knee: the lateral view grades displacement (Meyers–McKeever).
• Tunnel (notch) view to see the intercondylar region.
• MRI for meniscal entrapment and associated injuries; CT for fragment size and comminution before surgery.

• AP, lateral (the key view to grade displacement) and tunnel (notch) view of the knee.
• CT shows the size and comminution of the fragment; MRI detects meniscal entrapment, associated meniscal tears, ligament injuries and chondral damage (especially before planning surgery).

Classification

Meyers–McKeever I

Undisplaced or minimally displaced (< 3 mm).

Meyers–McKeever II

Anterior third to half lifted, posterior hinge intact ("bird’s beak" on the lateral view).

Meyers–McKeever III

Completely displaced, no bony contact (IIIA only the ACL insertion; IIIB the whole eminence, or rotated).

Zaricznyj IV

Comminuted fragment.

Types shown in 3D

Meyers–McKeever I

Undisplaced or minimally displaced fragment. Aspirate, then cast or brace in near-full extension for 4–6 weeks.

Meyers–McKeever II

The anterior part of the fragment is lifted by the ACL while the posterior rim stays hinged ("bird’s beak" on the lateral view). Try closed reduction in extension; operate if it stays up.

Meyers–McKeever III

Completely displaced and often rotated; the medial meniscus anterior horn or intermeniscal ligament may be trapped underneath. Arthroscopic reduction and suture or screw fixation.

Zaricznyj IV

Comminuted eminence. Suture fixation (through tunnels or anchors) holds small fragments better than screws.

Treatment

Type I (and type II that reduces)

Aspirate the haemarthrosis, extend the knee (full extension or 10–20° of flexion) and immobilise in a long-leg cast or brace for 4–6 weeks. Repeat X-rays at 1–2 weeks to check that it stays reduced.

Type II that does not reduce, III and IV

Arthroscopic (or open) reduction after freeing any trapped meniscus or intermeniscal ligament. Fixation with sutures through bone tunnels or suture anchors (good for small or comminuted fragments) or with cannulated screws (larger fragments). In children keep tunnels and screws away from the proximal tibial physis.

Adults

Usually operative, as for type III, with attention to associated ligament and meniscal injuries.

Aftercare

Brace with early, protected range of motion after secure fixation; return to sport after 4–6 months once strength and stability are restored. Arthrofibrosis is the most common complication, so motion should start early.

Complications

• Arthrofibrosis and loss of extension
• Residual ACL laxity (the ligament is stretched before it avulses)
• Malunion with impingement in the notch
• Non-union
• Growth disturbance from fixation across the physis