Trochlea Fractures

Definition. A trochlea fracture, specifically Laugier's fracture, is an isolated coronal shear fracture of the joint surface of the trochlea. It does not involve the columns unless it is associated with a complex fracture.

Epidemiology. The injury is extremely rare, less than 1% of distal humerus fractures. It is seen in young males after high-energy injury, or in osteoporotic females.

The bone. The trochlea is the spool of the elbow, covered in cartilage through an arc of 300 degrees. Its central groove, the sulcus, articulates with the greater sigmoid (trochlear) notch of the ulna, which wraps around the spool through nearly its full flexion-extension arc and articulates with it in both flexion and extension. The medial ridge is taller and more prominent than the lateral ridge and provides valgus stability, and the axis of rotation passes through the centre of the trochlea and of the capitellum.

The medial column. The trochlea is supported by the medial column. The medial epicondyle gives origin to the flexor-pronator mass and is the landmark for the approach; the mass must be elevated or split to reach the anterior aspect of the trochlea. Triceps inserts on the olecranon, but its medial border covers the posterior aspect of the medial column.

Blood supply. The trochlea is a watershed, supplied by small vessels that enter through the medial capsule and the non-articular areas, posteriorly and through the non-articular medial margin. A shear fragment has no soft-tissue attachments: it is purely articular, and its blood supply is retrograde through the subchondral bone that the fracture has just divided. That makes osteonecrosis and non-union a real and specific concern, and posterior comminution indicates disruption of the posterior vascular supply.

Nerves. The ulnar nerve runs immediately posterior to the medial epicondyle and must be identified and protected, or transposed, in any medial approach. The medial antebrachial cutaneous nerve is at risk during the superficial dissection, and injury causes a painful neuroma.

Laugier's fracture has its own AO/OTA code, 13-B3.2: a partial articular fracture in the frontal (coronal) plane involving the trochlea alone. Dubberley's classification was written for the capitellum and takes in the trochlea only when both fracture together; its A/B modifier records posterior comminution.

The Dubberley A/B modifier, the presence or absence of posterior comminution, is the single most important prognostic variable in these coronal-shear fractures. It is worth understanding precisely what it means and how it changes the operation.

What it is. The primary fracture is an anterior coronal-plane shear of the articular surface, a wafer of cartilage and subchondral bone. Modifier B means there is, in addition, comminution of the posterior aspect of the condyle or column: the back wall behind the shear fragment is broken rather than intact.

It strips the blood supply. The trochlea's vessels enter posteriorly and through the non-articular medial margin. Posterior comminution disrupts this posterior vascular pedicle and renders the articular fragment largely avascular, hence the higher rates of AVN and non-union with modifier B; with modifier A the supply is largely preserved.

It removes the buttress for fixation. Anterior-to-posterior headless compression screws work by compressing the shear fragment against an intact posterior cortex or column that acts as the backstop. If the posterior wall is comminuted there is nothing to compress against: screws alone pull the fragment into the defect, lose purchase and fail, and the construct must be changed.

How it changes the plan. In Dubberley A the posterior buttress is intact and countersunk anterior-to-posterior headless compression screws are usually sufficient. In Dubberley B, anticipate the need to rebuild or bypass the missing back wall with a posterior or medial column buttress plate, often with bone graft, and lower the threshold for a wider exposure. Counsel the patient about the substantially higher risk of AVN, non-union and secondary surgery; where the joint is unreconstructable in a low-demand elbow, this is the pattern that tips toward total elbow arthroplasty.

History. The mechanism may be a fall on the outstretched hand, possibly with the elbow slightly flexed and in varus, or a direct blow. The patient has pain, swelling and an inability to move the elbow.

Examination. Look for medial-sided bruising and tenderness over the medial column. A block to flexion or extension implies a mechanical block from a loose fragment.

The ulnar nerve. Check it. Acute neuropraxia is common from the blow, and tardy ulnar nerve palsy is a late complication.

Associated injuries. Look for an elbow dislocation, and for a capitellum fracture, which with the trochlea creates a Type IV capitellum fracture.

The AP view. It often looks normal, because the ulna overlaps the fragment, or shows only a faint flake medially.

The lateral view. This is the diagnostic view, though its signs are subtle. Look for:

• The double arc sign: two semicircles, the trochlear arc seen separate from the capitellar arc
• Superior migration of the fragment
• A "chewed up" appearance of the joint line

CT. CT is an absolute requirement: this surgery cannot be planned without it, because it defines the articular comminution.

• Coronal images show the shearing nature and the size of the fragment
• Sagittal images show posterior comminution (Dubberley B)
• 3D reconstruction is essential for planning the screw trajectory, and decides whether the screws can go front-to-back (easier) or must go back-to-front (harder)

The decision. Three features decide treatment: the size of the fragment, whether it is displaced, and the quality of the bone. A non-displaced fracture may be treated in a cast once CT has confirmed it is non-displaced; a displaced fracture is fixed, with headless screws in good bone, while in poor elderly bone total elbow arthroplasty is the alternative.

The 20% rule. A fragment larger than 20% of the articular surface is fixed. Excising one smaller than that is the traditional teaching, but the figure is a pragmatic heuristic, not a validated or evidence-derived threshold. The trochlea is load-bearing and intrinsically stabilising, so most authors favour fixation whenever it is technically feasible, even for a small fragment.

Goals. Anatomic reduction, because articular step-off leads to arthritis. Rigid fixation, because it allows the early motion that is crucial for the elbow. Compression, with headless screws buried beneath the cartilage.

Medial approach (Hotchkiss, over-the-top). The surgical sequence uses the extended medial column approach. Its limitation is that the lateral extent of the trochlea is hard to see.

1. Incise over the medial supracondylar ridge
2. Identify the ulnar nerve and release the cubital tunnel
3. Elevate the flexor-pronator mass anteriorly, or split it

Medial epicondyle (chevron) osteotomy. This gives an excellent view of the trochlea. Pre-drill the medial epicondyle, perform the osteotomy and reflect the flexor mass distally; the epicondyle is repaired with a screw at the end.

Olecranon osteotomy. Typically used for intercondylar fractures, it can be used here for posterior access.

Reduction and fixation. Reduce under direct vision and use K-wires provisionally to stick the wafer back on. Definitive fixation is with two or three headless compression screws (Herbert or Acutrak, the Acutrak Micro or Mini), usually anterior-to-posterior and countersunk. The screws are buried beneath the articular cartilage and must not violate the joint.

Anti-glide plate. A small plate on the medial column can sometimes act as a buttress if the fracture has slight medial extension.

Non-union and AVN. The fragment is devoid of soft-tissue attachments. AVN creates a sequestrum that causes pain and locking, and the treatment is excision and total elbow arthroplasty.

Arthritis. It comes on rapidly if an articular step-off remains: the elbow tolerates incongruity poorly.

Ulnar neuropathy. It follows surgical handling or scar tissue. Anterior transposition is often done in complex cases; routine transposition is debated.

Heterotopic ossification. The medial side carries a lower risk than the lateral or posterior side, but HO is still possible.

Evidence is limited to retrospective series and one pooled meta-analysis (Fisher et al, JSES Int 2022, 45 studies, 899 patients). The figures below are the best-available pooled estimates for coronal-shear fractures of the capitellum and/or trochlea, not isolated trochlear data, which remain at case-report level.

• Function: good with anatomic reduction and rigid fixation; mean MEPI about 91 and arc about 19 to 138 degrees in the Dubberley series, and mean DASH about 24 in the Tanwar headless-screw series
• Reoperation: about 14% pooled, for contracture release, hardware removal and ulnar nerve procedures
• Post-traumatic arthritis: about 21% pooled, driven by residual articular step-off
• Heterotopic ossification: about 12% pooled
• Avascular necrosis: about 7% pooled. Quote this figure rather than calling AVN inevitable; it is higher with posterior comminution (Dubberley B), which strips the residual blood supply
• Range of motion: a flexion contracture of 10 to 20 degrees is common and usually functional

Global epidemiology

• Isolated coronal-shear fractures of the distal humerus are rare (apparent capitellum fractures are roughly 1% of all elbow fractures); the truly isolated trochlear (Laugier) variant is rarer still and reported only at case-series level worldwide.
• Bimodal: high-energy injuries in young adults (FOOSH with the elbow near extension) and low-energy fragility fractures in osteoporotic older women.
• There is no dedicated society guideline for this specific fracture; management is extrapolated from distal humerus articular-fracture principles common to AO, BOA and AAOS teaching.

Side-by-side principles (no fracture-specific national guideline exists)

Registry note

• National joint registries (NJR England/Wales, AOANJRR Australia, SHAR Sweden, NZJR) capture total elbow arthroplasty implant survival and revision, which informs the salvage/elderly arm of this fracture — but they do not track ORIF of coronal-shear fractures, so primary-fixation outcomes rely on published series and the Fisher meta-analysis.

High- vs limited-resource practice

• Well-resourced: Routine pre-op CT with 3D reconstruction, headless compression screw systems, intra-operative fluoroscopy, and TEA available as backup.
• Limited-resource: CT may be unavailable, so a meticulous true-lateral radiograph and intra-operative assessment carry more weight; standard partially-threaded/mini-fragment screws may substitute for headless implants, and arthroplasty backup may be absent — pushing decisions toward fixation or, for tiny fragments, excision.

The trochlea is the principal bony constraint of the ulnohumeral joint. That biomechanical fact drives the fix-don't-excise philosophy of these fractures.

The osseous lock. The bony interlock between spool and notch is the primary restraint to varus, valgus and axial (medial/lateral) translation of the ulna at the elbow. The medial collateral ligament resists valgus and the lateral ulnar collateral ligament resists varus and posterolateral rotatory instability, but they act on an intact bony fulcrum. The trochlea is the keystone; the ligaments are the guy-ropes.

Congruity. The articulation is highly congruent, a constrained ginglymus or hinge. Even small losses of trochlear height or width change the geometry the ulna tracks on.

When the trochlea is lost. Remove or displace the spool and the ulna has nothing to sit in. It migrates rapidly, medially or laterally, and can frankly subluxate or dislocate regardless of whether the collateral ligaments are intact, which is why a competent MCL and LUCL do not protect a trochlea-deficient elbow. The drop sign, a widened ulnohumeral interval on a true AP radiograph, is the radiographic surrogate for that lost bony containment.

What it means for treatment. Reconstruction is strongly preferred over excision, because excising the trochlea removes the joint's primary stabiliser and excising a larger fragment leaves an unstable, incongruent elbow. Excision is reserved for a small fragment that is not contributing to containment. An unreconstructable trochlea in a low-demand elbow is treated with total elbow arthroplasty, whose linked/semi-constrained implant re-creates the lost bony constraint, rather than with excision arthroplasty.

The isolated trochlear (Laugier) fracture is rare enough that almost every management decision rests on extrapolation from capitellar and coronal-shear series rather than dedicated evidence.

Surgical approach. The choice lies between anterolateral, extended-lateral and medial-column or epicondyle-osteotomy exposures. Pooled data hint at fewer complications with the anterolateral approach for Dubberley A, but the meta-analysis explicitly concludes that the evidence is insufficient to mandate one approach, and a pure isolated-trochlear fragment is medial and may still need a medial exposure.

Screw direction. Anterior-to-posterior screws are technically easier and are countersunk under cartilage. Posterior-to-anterior screws preserve the articular cartilage and are mechanically stronger, but are harder to place for an anterior shear fragment. No comparative data exist.

HO prophylaxis. Routine pharmacological prophylaxis is not supported for isolated injuries: indomethacin and radiotherapy are unproven for isolated coronal-shear injuries and carry their own risks (non-union, GI). Use is selective, reserved for high-risk cases (associated dislocation or head injury, extensive dissection).

Ulnar nerve handling. In-situ decompression versus routine anterior transposition during a medial approach remains debated, with no trochlear-specific data.

Primary TEA threshold. In the elderly, comminution that cannot be reconstructed for stable fixation favours primary TEA, and there is RCT support (McKee) for the elderly OTA-13C elbow. The age and comminution threshold for choosing TEA over a salvageable ORIF is not defined for isolated articular shear patterns.