Capitellum

Capitellar fractures are uncommon – 3-4% of all distal humerus fractures (McKee).

They are sometimes referred to as partial articular fractures or unicondylar/single column fractures.

Beware fractures that appear to only involve the capitellum are often much more complex. They are often more complex than a simple "coronal shear" type fracture.

Look for:

extension into the lateral aspect of the trochlea (see imaging)

posterior comminution

involvement of the lateral epicondyle

Ruchelsman suggested the majority of so called unicondylar fractures are actually fractures of both the capitellum and trochlea.
Capitellar fractures occur more frequently in females – one explanation for this observation is the greater carrying angle of the elbow in females.
Capitellar fractures are rare in the immature skeleton, if diagnosing a capitellar fracture in the immature skeleton consider the possibility of it being a lateral condyle fracture.

20% of capitellum fractures have an associated radial head fracture.

Mechanism of injury

Capitellar fractures usually occur in the coronal plane, caused by a shear force following a fall on an outstretched hand or directly on the elbow.

The capitellar centre of rotation is 1 -1.5 cm anterior to the humeral shaft, rendering it vulnerable to fractures from a shear force.

Classification

No universally accepted classification system exists

Type I - Hahn-Steinthal first described capitellar fractures in 1853. This type involves a large segment of bone that makes up the whole of the capitellum.
Type II - Kocher-Lorenz 1896, described a similar pattern which only involves a shell of articular cartilage.
Type III - Grantham 1981 - comminuted fracture.

Bryan and Morrey (1985)

I Complete osteochondral fracture of the capitellum.
II Superficial osteochondral fracture fragment.
III Comminuted fracture fragment
IV Coronal shear fracture involving the capitellum and a section of the trochlea. – described by McKee.

Ring Jupiter (2003)

Jupiter and Ring placed capitellum fractures into the concept of articular fractures bearing in mind the simple coronal shearing fracture of the capitellum is rare, the fracture is often more complex.

They described five patterns of injury

Type 1 - single articular fragment that includes the capitellum and the lateral portion of the trochlea (coronal shear fracture)

Type 2 - Type-1 (occasionally comminuted) with an associated fracture of the lateral epicondyle

Type 3 - Type-2 with impaction of the metaphyseal bone behind the capitellum in the distal and posterior aspect of the lateral column

Type 4 - Type-3 with a fracture of the posterior aspect of the trochlea

Type 5 - Type-4 with fracture of the medial epicondyle

REPLACE IMAGE

Dubberley (2006)

Type 1 - Primarily the capitellum with or without the lateraltrochlear ridge

Type 2 - Capitellum and the trochlea as one piece

Type 3 - fractures of both the capitellum and the trochlea as separatefragments

These fractures were further subdivided into (A) or (B) depending on posterior condylar comminution

No isolated trochlear fractureswere identified in this series.

Investigations

Plain radiographs – Standard AP and lateral views.
Look for the double arc sign described by McKee. This is the overlap of the subchondral bone of the displaced capitellum and the lateral trochlea ridge.
Consider imaging the ipsilateral shoulder and wrist if clinical suspicion.
In type II fractures consider a radial head-capitellar view.
Look closely for more complex nature of injury, involvement of whole trochlea, comminution of fragments, comminution of posterior capitellum, involvement of lateral epicondyle.

CT Elbow
Elbow CT with 3D reconstruction can be very helpful to define the nature of the injury.

If the capitellum is comminuted posteriorly as in Dubberley type B fractures. This has important treatment implications for fixation, nothing to place headless screws into?

Look for medial extent of the fracture, articular impaction, and metaphyseal and condylar comminution.

Imaging the paediatric patient

Very very unusual injury in the paediatric patient.
Pradhan described how the diagnosis of a capitellar fracture in a six year old boy was aided by an oblique radiograph.
Remember the value of a contralateral elbow radiograph.
Arthrogram of the elbow.

Management

Operative

Closed reduction - described by Ochner (1996).
Elbow is fully extended.
Longitudinal traction is applied.
Elbow is gently flexed to lock fragment in place.

Multiple attempts at closed reduction should not be attempted as there is a risk of further articular damage.

Move onto open reduction if closed reduction fails.

Approach.

It is possible to see the majority of the capitellum from the lateral side using the proximal extension of the Kocher incision.

Alternatively consider an olecranon osteotomy for more comminuted fractures or the Jupiter ring 5 that extends right across to the medial epicondyle.

Consider the boyd interval and triceps split next to the olecranon if the fracture does not extend too far medially.

Options after reduction of the fracture has been achieved include:

Headless screw fixation
Countersink minifragment compression screws
K wires, threaded k wires

Excision of the fragment is an option if it is irreducible or deemed non viable.

Post operative regime

Depends on treatment if undertaking open reduction and internal fixation.

Aim to achieve enough primary stability to allow immediate Range of motion exercises.

Complications

Non union and avascular necrosis are surprisingly uncommon considering the size of the fragments.
Excision of the fragment is an option if avascular necrosis occurs.
Postoperative stiffness can be tackled by an anterior capsular release, open or arthroscopic. (Column procedure).

Prognosis

Results differ in the literature.
Grantham suggested unsatisfactory results at 5 year follow up - stiffness and instability were the problems.
McKee reports a 125º range of motion in his series of open reduction and internal fixation plus early motion.
Ruchelsman 2009 reported good to excellent results following open reduction and internal fixation of 16 capitellar fractures.

Key points

1. Look for other injuries –fracture extending to trochlea, radial head fracture.
2. Bryan/Morrey is the modern classification system.
3. CT is imaging modality of choice – 3D reconstruction with radius/ulna subtracted.
4. Good results in literature with ORIF and early motion.
5. AVN and non union uncommon

References

Thierry G. Guitton, Job N. Doornberg, Ernst L.F.B. Raaymakers, David Ring, and Peter Kloen; Fractures of the Capitellum and Trochlea; J. Bone Joint Surg. Am., Feb 2009; 91: 390 - 397

Ochner RS, Bloom H, Palumbo RC, et al. Closed reduction of coronal fractures of the capitellum. J Trauma. Feb 1996;40(2):199-203

Bryan RS, Morrey BF. Fractures of the distal humerus. In: Morrey BF, ed. The Elbow and Its Disorders. Philadelphia, Pa: WB Saunders; 1985:302-39.

McKee MD, Jupiter JB, Bamberger HB. Coronal shear fractures of the distal end of the humerus. J Bone Joint Surg Am. Jan 1996

Grantham SA, Norris TR, Bush DC. Isolated fracture of the humeral capitellum. Clin Orthop Relat Res. Nov-Dec 1981;(161):262-9

Ruchelsman DE, Nirmal C. Tejwani, MD1, Young W. Kwon, MD, PhD1 and Kenneth A. Egol, MD1Open Reduction and Internal Fixation of Capitellar Fractures with Headless Screws JBJS Am:90:1321-1329

Capitellar fracture in a child:the value of an oblique radiograph. A case report. Pradhan BB, BhasinB, Krom W. JBJS (Am). 2005;87:635-638.

Ring D, Jupiter JB, Gulotta L. Articular fractures of the distal part of the humerus. J Bone Joint Surg Am. 2003;85:232-8

Dubberley JH, Faber KJ, Macdermid JC, Patterson SD, King GJ. Outcome after open reduction and internal fixation of capitellar and trochlear fractures. J Bone Joint Surg Am. 2006;88:46-54

David E. Ruchelsman, Nirmal C. Tejwani, Young W. Kwon, and Kenneth A. Egol; Coronal Plane Partial Articular Fractures of the Distal Humerus: Current Concepts in Management; J. Am. Acad. Ortho. Surg., December 2008; 16: 716 - 728.