Case Report: Isolated Trochlear Fracture Of The Humerus

The fracture of the distal part of the humerus usually involves the capitellum and variable part of the trochlea. The deep position of the trochlea within the elbow joint makes it a rare occurrence and protects it from direct damage. A 23-year-old local man named Mumtaz presented with an intra-articular half-moon-shaped fragment that had traveled and forward, leading us to assume a capitellar fracture. That was fixed through the medial approach of distal humerus. Postoperatively, patient a had good pain-free range of motion.


INTRODUCTION
The first description of an isolated trochlear fracture of the humerus was in 1853 by Laugier.Thus, the trochlea fracture is also sometimes acknowledged as Laugier's fracture.The fracture of the distal part of humerus usually involves capitellum and variable part of the trochlea.The deep position of the trochlea within the elbow joint makes it a rare occurrence and protects it from direct damage.These fractures are known to result in elbow post-traumatic arthritis and instability.Therefore, management of these types of fractures requires a systematic approach, obtaining an articular anatomic reduction and providing a painless, stable and mobile elbow joint 3 .The Laugier's fracture, also known as an isolated fracture of the trochlea, is uncommon and frequently accompanied by elbow dislocation, ligamentous injuries, capitellar fractures, radial head fractures, and/or olecranon fractures 2,9 .Regarding its management, there is no agreement, which is based on trans articular distal humeral fractures.Posterior splint immobilization for 3 weeks is recommended if the fracture is undisplaced 5 .If there are small unamenable osteochondral fragments, excision followed by early elbow movement is the treatment of choice 2,10 .Displaced fractures should be anatomically reduced to restore articular congruency, using headless Herbert screws or bioabsorbable screws 2,11,12 .

CASE REPORT
A 23-year old local man named Mumtaz presented with trauma to the right elbow sustained due a to fall from a height.Radiographs revealed an isolated trochlear fracture of the humerus.A lateral radiograph revealed an intra-articular half-moon-shaped fragment that had traveled forward, leading us to assume a capitellar fracture.Anteroposterior radiographs merely revealed an abnormality of his medial joint area (Fig- 1).A computed tomography (CT) scan confirmed an isolated front-line fracture of his trochlea, without the participation of the capitellum (Fig- 2).Open reduction and internal fixation were planned for our patient.The joint was opened through a medial approach, passing between the triceps brachii in the back and brachialis in the front.His ulnar nerve was dissected and protected.Accessing the joint capsule required de-insertion of the humeral part of his pronator teres, without interrupting the medial collateral ligament, which was intact.His trochlea was fractured across the front line, with the persistence of the posterior wall.The fragment had moved up and forward without any compaction or loss of cartilage substance 5 .This case report describes an isolated fracture of the humeral trochlea treated with open reduction internal fixation.Radiographic union was present at 13 weeks, and at 20 weeks post-op, the patient had regained full elbow range of motion minus 5 degrees of terminal flexion.Open reduction and internal fixation can be performed with success if the trochlear fragment is large enough 4 .

DISCUSSION
The trochlea is an articular surface of the elbow joint and acts as a pulley on which hinged motion of the ulno-humeral joint occurs.Non-operative treatment or excision of coronal shear fractures leads to stiffness or instability of the elbow joint.
Fracture of the trochlea is usually associated with elbow dislocation and capitellar or medial condylar fracture 6 .Isolated fracture of the humeral trochlea is very rare.This is explained by its position deep within the trochlear notch cavity and the absence of any muscular or ligamentous attachments at this level, which protects it against direct and indirect trauma 7 .Isolated trochlear fractures occur as a result of axial loading when the elbow is in extension, such as a fall on an outstretched hand, and the force transmits through the palm and along the ulna. 13A role of varus stress with axial loading in isolated trochlear fractures is also suggested 12 .Furthermore, the ulno-humeral joint is subjected to very light compressive and shear forces compared to those experienced by the radio-humeral joint, which explains the high frequency of capitellar fractures compared to trochlear fractures 8 .Evaluation of radiographs in the anteroposterior view may show an irregularity at the ulno-humeral joint 3 , but the image can be interpreted 'normal' 5 .In a lateral view, the appearance of an articular half-moon-shaped fragment moved up and forward could suggest a capitellar fracture.For this reason, diagnosis is based on the results of a CT scan 3,4 .It is unclear what caused the trochlear rather than the entire articular capitello-trochlearblock to fracture.As the anterior part of the trochlea is subjected to the force from the coronoid process of the ulna in a flexed-elbow position, it selectively causes the coronal shear fracture of the trochlea 14 .The medial approach enables good visualization of the anteromedial aspect of the distal humerus for fixation of trochlear and/or medial epicondylar fractures 15 .It avoids the need for the more extensive posterior approach combined with olecranon osteotomy.The lateral approach has limited exposure and cannot fix fractures extending into the capitellum.Therefore, preoperative computed tomography is essential.In the reported cases, the cancellous screws were passed from the non-articular area.Their direction was oblique, from front to back and from medial to lateral, fixing the trochlea to the capitulum.Alternatively, Herbert screws were inserted into the articular surface buried beneath the cartilage; their direction was perpendicular to the fracture line, securing the fragment of the trochlea to the posterior wall with maximum compression.We opted for this type of osteosynthesis because it is more stable from a biomechanical point of view but the prognosis of coronal trochlear fractures is poor when there is articular cartilage damage (particularly small coronal osteochondral fractures) 11 .The trochlear fractures can be fixed using the olecranon osteotomy, which many surgeons may be familiar with.The medial approach enables direct access to the trochlear fracture (particularly anterior coronal fractures), preserves the blood supply, and avoids additional surgical morbidity and complications from olecranon osteotomy.The vascular supply to the trochlea is through its posterior surface.Thus, the posterior approach may disrupt these vessels and increase the risk of avascular necrosis.In a cadaveric study, trochlear excision leads to considerable instability of the elbow joint 12 .Both the capitellum and trochlea have an important role in stability; excision of the trochlea results in multiplanar instability of the ulno-humeral and radio-capitellar joints.The choice of fixation depends on the size of fragment and the comminution 17 .In this case we managed the displaced trochlear fracture using single headless Herbert screw.Herbert and Fischer in 1984 introduced the double-threaded design of screws that allows them to sink below the articular cartilage level and provide necessary compression for early mobilization 18,19 .Using the Kirschner wires and compression screws with the combination early range of motion exercise, have also borne successful result.

CONCLUSION
Isolated trochlear fractures are uncommon and only appear infrequently in the literature.We advocate open reduction and internal fixation for displaced fractures where prior studies have indicated that patients had a positive outcome after ORIF.Successful outcomes have been recorded in our case report of solitary trochlear fractures with good ROM and DASH(Disability of arm, shoulder, hand) scores.