Last Updated on February 11, 2025
Capitellum Fractures are intraarticular elbow injuries involving the distal humerus at the capitellum. Capitellum fractures are rare and account for 1% of elbow fractures. They form about 6 percent of distal humerus fractures.
Injuries to the capitellum are usually a result of axial loading of the capitellum by forces transmitted through the radial head, the lateral trochlear ridge, and the lateral half of the trochlea.
Capitellum fractures are frequently missed on the first examination. The fracture is not obvious on anteroposterior radiographs due to the shadow background of the distal humerus. Concurrent radial head and collateral ligament injuries are common
Relevant Anatomy
The elbow joint is made up of three bones, the humerus, ulna, and radius. The elbow joint comprises the distal end of the humerus and the proximal ends of the radius and the ulna.
The humeral condyle, located at the distal end of the humerus, consists of the capitellum laterally and the trochlea medially. It is covered by articular cartilage and articulates with the trochlear notch of the ulna and the concave superior aspect of the head of the radius.
The axis of the trochlea is externally rotated by 3 -8 degrees and compared with the longitudinal axis is in 4- 8° of valgus. The articular surface of the trochlea and capitellum is projected anteriorly at an angle of 40° to the axis of the humerus. The trochlea, the distal medial articulating end of the humerus acts as a pulley for the ulnar trochlear notch to rotate around as the elbow is flexed.
The capitellum is a rounded ball of bone that adjoins the trochlea laterally. It is the distal lateral articulating end of the humerus. It articulates with the radial head to form a radiocapitellar joint
Radiocapitellar articulation provides longitudinal and valgus stability of the elbow. It has an integral relationship with the posterolateral ligamentous complex of the elbow.
The radial collateral ligament is the lateral thickening and extends from the lateral humeral epicondyle and distally blends into the annular ligament of the radius.
The annular ligament of the radius wraps around the head of the radius and attaches to the ulna anteriorly and posteriorly. It allows the head of the radius to rotate inward during supination and pronation while maintaining the stability of the radial ulnar joint.
The elbow joint is supplied by the musculocutaneous, radial, and ulnar nerves.
Nervewise, the inferior lateral cutaneous nerve of the arm and the posterior cutaneous nerve of the forearm supply the lateral elbow. The medial cutaneous nerve of the forearm supplies sensation to the medial aspect of the elbow. The cubital fossa is supplied by the musculocutaneous nerve (the lateral cutaneous nerve of the forearm).
The blood supply to the elbow joint is by the branches from the periarticular arterial anastomoses of the elbow.
[Read complete elbow anatomy]
Mechanism of Injury
Capitellum fractures are typically low-energy injuries and occur often due to falls on outstretched hands. Direct, axial compression with the elbow in a semi-flexed position creates shear forces that lead to capitellum fracture
The radiocapitellar joint is an important static stabilizer of the elbow and these fractures can block the motion and lead to instability due to loss of the radiocapitellar articulation.
Classification of Capitellum Fractures
Bryan and Morrey Classification (with McKee modification)
- Type I
- Large piece of the capitellum involved
- Can involve trochlea
- Type II
- Also called Kocher-Lorenz fracture
- Shear fracture of articular cartilage
- Articular cartilage separation occurs with very little subchondral bone attached
- Type III
- Also called Broberg-Morrey fracture
- Severely comminuted multi fragmentary fracture
- Type IV
- McKee modification
- Coronal shear fracture that includes the capitellum and trochlea
Clinical Presentatation of Capitellum Fractures
The patient presents with pain and swelling in the elbow after a fall on the outstretched arm [FOOSH]. The elbow is typically kept in a semi-flexed position.
The examination reveals diffuse tenderness, Swelling, and signs of soft tissue injury like ecchymosis. There may be a mechanical block to flexion movement.
A thorough examination of the limb should be done including neurovascular examination
Imaging
X-ray
AP and lateral views of the elbow should be done. The injury is better seen on lateral view. subchondral bone of the capitellum and lateral part of the trochlea may show a double arc sign. Other concurrent injuries of the affected elbow should be looked for.
An ipsilateral wrist x-ray should be done especially when there is wrist pain.
CT
CT identifies the fracture anatomy better and helps in classification.
MRI
Not routinely needed.
Treatment of Capitellum Fractures
Nonoperative Treatment
Nonoperative treatment of capitellum fractures consists of nondisplaced type I and II fractures. These fractures have less than 2 mm of displacement.
For these fractures, a posterior splint immobilization for 3-4 weeks followed by gradual mobilization is done.
The nonoperative treatment of capitellum fractures should be considered in patients with low demand such as in old age and those with medical conditions that make them unfit for surgery.
Operative Treatment
Because the capitellum fractures are intra-articular injuries, the displaced fractures require restoration of the anatomy open reduction and internal fixation followed by early mobilization. Some fractures can be treated with arthroscopically assisted surgery where a very small proportion needs arthroplasty. Some fracture types [II and IV] when displaced [>2mm] would require excision of the fragment.
Open reduction and internal fixation
Open reduction and internal fixation of capitellum fractures help in early mobilization. This minimizes stiffness and degenerative arthritis due to anatomical reduction.
This is indicated in displaced type I fractures (>2mm) and type IV fractures.
Lateral and posterior approaches are most commonly used to fix the fracture fragment.
- Lateral column approach– The incision centered over the lateral epicondyle extending to 2cm distal to the radial head. This avoids the blood supply on the posterolateral aspect of the elbow. Lateral ulnar collateral ligament integrity should be maintained. The implants can be used to fix the capitellum fragment- headless screw, mini-fragment screw, capitellar plates for fractures with proximal extension
- Posterior approach with or without olecranon osteotomy– is used in capitellar fractures with associated fractures of the humerus/olecranon. It allows greater dissection and extensive work. Allows concomitant fixation of medial-sided injuries and/or distal humeral fractures. The ulnar collateral ligament can be carried. Implants used can be – headless compression/cannulated screws for capitellar components and additional supplemental fixation for concomitant pathology
Fragment Excision
Fragment excision is indicated in type II and III capitellum fractures with displacement >2 mm.
Arthroscopic-assisted Fixation
It can be considered in isolated type I fractures with good bone stock. Anteromedial, anterolateral and posterolateral are the standard portals.
Total Elbow Arthroplasty
Capitellum fractures in elderly patients with associated medial column instability can be considered for total elbow replacement.
Complications
- Nonunion
- Heterotrophic ossification
- Avascular necrosis of capitellum
- Elbow instability
- Elbow contracture/stiffness (most common)
- Ulnar nerve injury
- Post-traumatic arthritis
- Cubital valgus
- Tardy ulnar nerve palsy
- Infection
References
• Cheung EV. Fractures of the capitellum. Hand Clin. 2007;23(4):481-486. [Link]
• Yamaguchi K, Sweet FA, Bindra R, Morrey BF, Gelberman RH. The extraosseous and intraosseous arterial anatomy of the adult elbow. J Bone Joint Surg Am. 1997;79(11):1653-1662.
• Fornalski S, Gupta R, Lee TQ. Anatomy and biomechanics of the elbow joint. Tech Hand Up Extrem Surg. 2003;7(4):168-178.
• Tanriverdi B, Kural C, Altun S. Capitellum fractures: Treatment with headless screws and outcomes. Jt Dis Relat Surg. 2020;31(2):291-297. 1
