Lateral Condyle Fractures - Pediatric

The lateral condyle is the second most common paediatric elbow fracture after the supracondylar fracture, about 15% of them, and it carries the higher complication rate of the two. It is intra-articular and prone to nonunion, and it can lead to progressive cubitus valgus and a tardy ulnar nerve palsy years after the injury.

Who and how. Peak age is 5-7 years, with a slight male predominance, and the mechanism is usually a fall onto the outstretched hand.

Why it matters. Unlike the supracondylar fracture, this one crosses the articular surface. It needs an anatomic reduction to prevent degenerative change and angular deformity, and because it is intra-articular the fracture lies bathed in synovial fluid from the elbow joint; with the pull of the extensor origin added, the risk of nonunion is high, which is why surgery is often needed.

The fragment. The lateral condyle is the capitellum, which articulates with the radial head, a variable lateral portion of the trochlea, and the lateral epicondyle, where the common extensor origin attaches. The lateral collateral ligament attaches to the fragment as well, and the physis is involved, so the injury follows a Salter-Harris pattern.

The fracture line. It runs through the lateral metaphysis, across the physis, usually posterolaterally, and into the articular surface of the trochlea or capitellum.

Blood supply. It enters the lateral condyle posteriorly. Once the condyle has fractured the fragment has no anterior blood supply at all, so the posterior soft tissues are protected at surgery.

Deforming forces. The extensor muscles attached to the lateral epicondyle pull the fragment distally and rotate it, and that is what displaces it.

Two systems are in use. Milch describes where the fracture line exits and is the one most commonly cited; Weiss (with Jakob) grades displacement and articular congruity and is the one that guides treatment.

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Milch. The trochlear ridge is the landmark. A line that exits lateral to it leaves the elbow stable; a line that exits through it means the ulnohumeral articulation may be unstable. Type II is more common.

Know its weakness, because the examiners do. Weiss and colleagues opened their 158-patient series by stating that Milch, though the most commonly cited system, "has not been shown to be predictive of outcome or recommend treatment", which is precisely why they built a classification on displacement and articular congruity instead. Milch describes where the fracture line exits; it does not tell you whether the cartilage hinge is intact, and that is the thing that governs both stability and complications. Use Milch for anatomical description and Weiss for decisions.

What separates Type II from Type III is the cartilage, not the millimetres. Weiss's 4 mm figure is a useful radiographic surrogate: every Type II in that series measured under 4 mm and every Type III measured 4 mm or more, which is why a fracture under 4 mm can reasonably be pinned closed before committing to an arthrogram. The surrogate is not the definition. A fracture displaced 3 mm with a disrupted articular surface is a Type III and carries Type III's risk, a complication rate of 34% against 11% for Type II.

History. A fall onto the outstretched hand with a varus stress. Ask about the time since injury, any swelling or deformity, neurovascular symptoms and previous elbow injury.

Examination. Lateral elbow swelling and tenderness, with ecchymosis that may be extensive, and a range of motion likely limited by pain. Do a full neurovascular examination, and check elbow stability against the opposite side.

The differential. The painful, swollen paediatric elbow has several causes; the table gives the feature that separates each from a lateral condyle fracture and the pitfall each carries.

Radiographs. AP and lateral views alone can underestimate displacement, so add an internal oblique, and compare with the opposite elbow in a young child:

• AP elbow - fragment size and displacement; measure the gap here
• Lateral elbow - rotation of the fragment, which often rotates posteriorly
• Internal oblique - 45° of internal rotation places the fracture line in profile, for better visualisation of the fracture
• Comparison views of the opposite elbow, which help in young children

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MRI and arthrography. Consider them when an occult fracture is suspected (an effusion but no visible fracture), when the cartilaginous extent of the fracture is unclear, or to assess articular congruity. An arthrogram, contrast injected into the elbow joint, outlines the cartilaginous extent of the fragment, and is useful intraoperatively or to clarify displacement.

The threshold. Displacement greater than 2 mm, or any rotation of the fragment, is the indication for surgery. Some authors are more aggressive and operate on any fracture displaced more than 2 mm on any view. Below 2 mm the fracture can be treated in a cast, but only with close follow-up, because it can displace in the cast.

The 2 mm versus 4 mm debate. The operative threshold is contested. Many use over 2 mm on the maximally displaced view; others reserve open surgery for at least 4 mm (articular disruption) and treat 2-4 mm fractures with closed pinning after an arthrogram. Weiss's data link the 4 mm point to articular incongruity and higher complications.

Non-operative (Weiss Type I). Less than 2 mm of displacement with an intact cartilage hinge. A long arm cast at 90° of elbow flexion for 4-6 weeks until union is confirmed, with X-rays weekly for the first 3 weeks; if any displacement occurs, convert to ORIF. Close follow-up is mandatory, because up to 20% of initially undisplaced fractures may displace.

Operative (Weiss Types II and III). Displacement greater than 2 mm or any rotation of the fragment. Open reduction through a lateral (Kocher) approach, the articular surface reduced anatomically under direct vision and held with two divergent smooth K-wires, the reduction checked on fluoroscopy; a Type II fracture with intact cartilage may be pinned closed instead. Afterwards, a long arm cast for 4-6 weeks, with the pins removed at 4 weeks if union is proceeding.

Set-up and approach. Supine, with the arm on a hand table, through the lateral (Kocher) interval between anconeus and extensor carpi ulnaris. The critical step is to see the articular surface from anterior and to leave the posterior soft tissues on the fragment alone.

Reduction. Reduce the articular surface anatomically; the metaphyseal reduction usually follows.

Fixation. Two smooth K-wires, usually 1.6 mm, in a divergent configuration, crossing the fracture site but avoiding the olecranon fossa.

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Implant choice. Smooth K-wires are the traditional and standard fixation because they spare the open physis; screws should not cross the physis in a young child. Some surgeons use a cannulated screw in an older child near skeletal maturity for more stable fixation, and cannulated or headless screws are increasingly used near maturity for compression and earlier motion. Comparative data show no clear outcome superiority of one implant over the other.

Percutaneous (in situ) pinning. For the minimally displaced fracture where the reduction is adequate but the surgeon is concerned it will displace. Under fluoroscopy, two pins from the lateral epicondyle are directed proximally and medially. Its limitation is that the articular reduction cannot be seen directly, so it is best reserved for near-anatomic alignment.

The table lists the recognised complications; the three that need explaining follow it.

Cubitus valgus and tardy ulnar nerve palsy. Nonunion leads to lateral physeal arrest while medial growth continues, so the elbow drifts into progressive valgus with a lateral spur. The valgus stretches the ulnar nerve around the medial epicondyle over years, which is why the palsy is "tardy": it may present years after the original injury as an ulnar neuropathy. Treatment is ulnar nerve transposition, often anterior subcutaneous, and may require a supracondylar or distal humeral osteotomy to correct the carrying angle.

Lateral spur and overgrowth. A lateral bony prominence with mild lateral condylar overgrowth is extremely common after healing, even of well-reduced fractures, and is almost always benign and cosmetic: periosteal healing new bone over a united fracture, which usually remodels and becomes less prominent with growth. The clinical task is to reassure the family that it is not a nonunion. Surgery for the spur alone is rarely needed.

Fishtail deformity. A late V-shaped notch of the central distal humerus between the capitellum and trochlea, caused by osteonecrosis or growth arrest of the lateral trochlea after a lateral condyle (or supracondylar or T-condylar) fracture, and aggravated by posterior soft-tissue stripping at surgery. It is often an incidental radiographic finding years later, but it can cause pain, clicking, restricted motion or progressive deformity. It is the reason preservation of the posterior blood supply is critical during ORIF.

The protocol after fixation is a cast, a wound and pin-site check, a radiograph before the pins come out, and a radiograph before the cast does.

Prognosis depends on prompt diagnosis and treatment. Outcomes are good when:

• The fracture is recognised early
• Displacement greater than 2 mm is treated surgically
• An anatomic articular reduction is achieved
• Union is confirmed before discharge from follow-up

They are poor when the diagnosis is delayed, when the fracture displaces in the cast and the displacement is missed, and when a nonunion develops.

Side-by-Side Society Guidance

Early nonunion (less than 3-6 months). ORIF with bone grafting is still possible, and gives better outcomes than late reconstruction.

Established nonunion (greater than 6 months). In situ fixation with bone grafting, or a corrective osteotomy. The nonunion may be too sclerotic for direct healing without an osteotomy. Late nonunion with cubitus valgus may require a supracondylar osteotomy for angular correction plus ulnar nerve transposition.

Late presentation. The challenge is a fragment that may be fibrosed in its displaced position. Under 3 weeks it is still reasonable to attempt ORIF. Beyond 3-4 weeks, in situ fixation may be considered if there is functional limitation, but the outcomes are less predictable. Much later, it is better to accept the position and address the deformity if it develops.

Closed versus open reduction. Traditional teaching mandated open reduction for displacement over 2-4 mm to confirm articular congruity. Song's prospective series and later cohorts show that closed reduction with percutaneous pinning can succeed even in fully displaced or rotated fractures, with an intraoperative arthrogram to confirm the joint reduction. The trade-off is the inability to inspect the articular surface directly.

Buried versus exposed pins. Leaving the pins percutaneous allows removal in clinic but carries a risk of pin-site infection; burying them reduces infection but needs a second anaesthetic for removal. Practice varies. Pin-site infection is usually superficial and resolves with oral antibiotics and pin removal.