Isolated fractures of the humeral trochlea are extremely rare injuries and were first described by Laugier in 1853. Despite advances in the understanding and treatment of distal humeral fractures, the exact mechanism responsible for isolated trochlear fractures remains unclear. The Orthopaedic Trauma Association classifies these injuries as type 13-B3, although this classification is infrequently used in clinical practice. The rarity of isolated trochlear fractures is attributed to the trochlea’s deep intra-articular position, its protection by the olecranon and coronoid processes, and the absence of direct muscular or ligamentous attachments. Most trochlear fractures occur in association with capitellar fractures, condylar injuries, elbow dislocations, or ligamentous disruptions. Treatment options include fragment excision or open reduction and internal fixation (ORIF). We present a rare case of an isolated displaced trochlear fracture managed successfully through a medial approach using Herbert screw fixation, resulting in excellent functional recovery.

A 35-year-old male sustained a physical assault to the left elbow while it was in extension and supination. Clinical evaluation revealed pain and swelling localised to the medial aspect of the elbow, with restricted flexion and extension, while pronation and supination were preserved ^[1]. Anteroposterior radiographs showed irregularity of the medial joint space, while the lateral view demonstrated an intra-articular, half-moon–shaped fragment displaced anterosuperiorly, initially suggestive of a capitellar fracture (Fig. 1).

Figure 1: Anteroposterior and lateral radiographs of the left elbow demonstrating an intra-articular coronal shear fracture of the trochlea with anterior displacement of the fragment.

Computed tomography (CT) confirmed an isolated coronal shear fracture of the trochlea without capitellar involvement (Fig. 2).

Figure 2: Three-dimensional computed tomography reconstruction showing an isolated fracture of the humeral trochlea without associated capitellar involvement.

The patient underwent ORIF through a medial approach, between the triceps posteriorly and brachialis anteriorly (Fig. 3).

Figure 3: Intraoperative image showing exposure through the medial approach between the brachialis anteriorly and triceps posteriorly.

The ulnar nerve was carefully identified and protected. Exposure of the joint capsule required partial disinsertion of the humeral origin of the pronator teres, preserving the intact medial collateral ligament ^[2]. Intraoperatively, the trochlear fragment was displaced upward and forward, with an intact posterior wall. The articular cartilage appeared macroscopically intact without visible chondral defects; however, no quantitative cartilage assessment system was utilised. Reduction was facilitated by elbow flexion, allowing adequate retraction of the brachialis muscle ^[3]. Fixation was achieved using one 3.5-mm Herbert screw and one partially threaded 4.5-mm cancellous screw inserted from the non-articular surface ^[4]. Both screws were directed obliquely from posterior to anterior and medial to lateral, securing the trochlea to the capitellum (Figs. 4 and 5).

Figure 4: Intraoperative anteroposterior and lateral radiographs demonstrating fixation with Herbert screw and cancellous screw.

Figure 5: Post-operative lateral and anteroposterior radiographs demonstrating fixation with Herbert screw and cancellous screw.

The ulnar nerve was reassessed to rule out compression, and the elbow demonstrated satisfactory motion in both flexion-extension and pronation-supination planes. The wound was closed in layers, and a posterior plaster slab was applied with the elbow maintained at 90° flexion.

Outcome and follow-up: 

At 3 months postoperatively, the patient exhibited pain-free motion from 0° to 135° of flexion, with no evidence of instability (Fig. 6).

Figure 6: Clinical photograph at 3 months follow-up showing restored elbow flexion and extension.

Follow-up radiographs confirmed maintained reduction and complete fracture union without any signs of avascular necrosis or degenerative changes (Fig. 7).

Figure 7: Radiographic outcome at one year follow-up

At 12 months, the patient achieved full functional recovery, attained a Mayo Elbow Performance Index score of 100, and successfully resumed all pre-injury activities.

The humeral trochlea is an essential component of the elbow joint, facilitating smooth ulnohumeral articulation. Its disruption can lead to instability and stiffness if inadequately treated. Isolated trochlear fractures are uncommon due to the trochlea’s deep intra-articular position and absence of direct soft-tissue attachments. The exact biomechanical mechanism responsible for isolated trochlear fractures remains uncertain. Proposed mechanisms include axial loading transmitted through the ulna during elbow extension or varus stress resulting in coronal shear forces across the trochlea. In the present case, the mechanism is inferred from the injury history but was not experimentally investigated. Consistent with our findings, Rehman et al. (2025) reported a successful case of open reduction and Herbert screw fixation via a medial approach, emphasising the importance of precise anatomical reduction for optimal functional recovery ^[5]. Similarly, Gonçalves and Ring (2016) demonstrated that the medial approach preserves vascularity and minimises the risk of avascular necrosis, supporting our chosen surgical exposure ^[6]. Studies by Yu et al. highlighted the efficacy of Herbert screw fixation in coronal shear fractures of the capitellum, achieving excellent articular congruity and motion restoration—outcomes comparable to ours ^[7,8]. The mechanism of injury in our patient, involving axial loading through an outstretched hand, aligns with their proposed biomechanical explanations ^[9]. Our result of complete motion recovery further supports the consensus that stable fixation and anatomical reduction are key to preventing post-traumatic arthritis ^[10,11]. CT remains the diagnostic gold standard, as also recommended by these authors. Hence, our case reinforces the growing evidence supporting ORIF via a medial approach using Herbert screws as an effective strategy for achieving optimal functional outcomes. Although conservative treatment has been described for minimally displaced trochlear fractures, displaced intra-articular fractures generally require anatomical reduction and stable fixation to restore joint congruity and permit early mobilisation. Our case involved a displaced coronal shear fracture and was therefore managed surgically. The present case adds to the limited literature on isolated humeral trochlear fractures and highlights the importance of maintaining a high index of suspicion in patients presenting with medial elbow pain following trauma. Unlike most previously reported cases, our patient had no associated capitellar fracture, elbow dislocation, or ligamentous instability. Furthermore, successful management through a medial approach using combined Herbert screw and cancellous screw fixation resulted in excellent functional recovery without complications. This case reinforces the role of early CT-based diagnosis and stable anatomical fixation in achieving favourable clinical outcomes. No evidence of hardware prominence, screw penetration, heterotopic ossification, ulnar nerve symptoms, infection, loss of fixation, or avascular necrosis was observed during the 12-month follow-up period [Table 1].

Table 1: Evidence summary of previously reported isolated trochlear fractures.

Limitations: 

This report describes a single patient, and therefore, the findings cannot be generalised to all isolated trochlear fractures. The rarity of this injury limits the availability of larger comparative studies and standardised treatment protocols. Magnetic resonance imaging (MRI) was not performed because there were no clinical signs of ligamentous instability, and CT adequately characterised the fracture pattern for surgical planning. Functional assessment was primarily based on the Mayo Elbow Performance Index, and additional patient-reported outcome measures, such as Disabilities of the Arm, Shoulder, and Hand or Oxford Elbow Score, were not available. Long-term follow-up beyond twelve months would be valuable to assess post-traumatic arthritis, avascular necrosis, and late stiffness. Post-operative CT or MRI was not obtained because radiographs demonstrated satisfactory union and restoration of elbow function.

Isolated trochlear fractures are rare injuries that demand a high index of suspicion for diagnosis. Detailed CT is essential for accurate fracture characterisation and surgical planning. Open reduction and stable internal fixation through a medial approach can achieve excellent functional recovery, restore elbow stability, and minimise the risk of post-traumatic stiffness or degenerative arthritis.

Isolated humeral trochlea fractures are rare; CT aids diagnosis, and stable ORIF provides excellent functional outcomes.