Monteggia fracture dislocations

Cite this article as:
Rie Yoshida. Monteggia fracture dislocations, Don't Forget the Bubbles, 2019. Available at:
https://doi.org/10.31440/DFTB.21141

Emiko is an 8 year old girl who presents to the ED with a swollen and painful left arm. She is a keen mixed martial arts enthusiast and has suffered a direct blow to the arm whilst practising earlier today. On examination, her left proximal forearm and elbow joint are swollen and tender. She has limited movement of her elbow joint. The arm is neurovascularly intact.

Case courtesy of Radswiki, Radiopaedia.org. From the case rID: 12222

X-rays show a fracture of the proximal ulna.  As she is also tender at the elbow, you go back to carefully review her x-ray.

You note both posterior and anterior fat pads are present but much more strikingly, the radio-capitellar line (the red line) on Emiko’s x-ray does not bisect the capitellum: in addition to her proximal ulna fracture, Emiko also has a dislocated radial head.  Emiko has a Monteggia fracture-dislocation. 

Monteggia fracture-dislocations consist of a fracture of the proximal ulna with associated dislocation of the radial head. As with most forearm fractures, they most commonly occur due to a fall on an outstretched hand, with hyperextension or hyper-pronation of the elbow, or a direct blow to the forearm.

Monteggia fracture-dislocations are not to be confused with Galeazzi fracture-dislocations.  There are several mnemonics to differentiate between the two but ‘fractured MUGR’ (Monteggia: fractured Ulna; Galeazzi: fractured Radius) is a favourite of mine.

Incidence

Monteggia fracture-dislocations have a peak incidence in the 4-10-year-olds.  Although rare, accounting for just 2% of all elbow fractures in children, recognition of a Monteggia fracture-dislocation is critical requiring urgent orthopaedic assessment.  Isolated midshaft ulna fractures are very rare in children: when an ulna fracture is identified you must also get an x-ray of the wrist and elbow joints.  Monteggia fracture-dislocations are easily missed, leading to permanent disability.

 

Examination 

Examine the forearm, wrist and elbow joint.

Inspection and palpation: The child will have swelling, tenderness and possible deformity of the proximal forearm and elbow. Pain at the ulna fracture may distract from the elbow so always have a rule to examine the joint above and joint below any fracture.  If you suspect an ulna fracture you may also be able to palpate the dislocated radial head.  Check for any open wounds.

The most commonly injured nerve is the posterior interosseous branch of the radial nerve.  Always check for signs of neurovascular compromise or compartment syndrome.

 

X-ray findings

Make sure your forearm x-rays are true APs and laterals and include both the wrist and elbow with the distal humerus.

 

If you identify an ulna fracture on x-ray, always look for dislocation of the radial head by checking for radio-capitellar alignment.

 

The ulna fracture is most often at the proximal to middle third of the ulna.  It may not always be as dramatic as Emiko’s and may not even be a complete ulna fracture: Monteggia fracture-dislocations can occur with other more subtle ulna fractures such as greensticks and even plastic deformation fractures.

Always, always check the posterior border of the ulna to look for plastic deformation. A normal ulna has a straight posterior border.  But if the posterior border does not sit nicely on a horizontal line it is not straight: it’s an occult ulna plastic deformation fracture.

 

 

Classification

Monteggia fracture-dislocations are most commonly classified by the Bado Classification. Bado was a South American surgeon, founding The Society of Trauma and Orthopaedics of Uruguay and The Latin American Society of Orthopedics and Traumatology. His system classifies Monteggia fracture-dislocations into four categories according to the direction of radial head dislocation:

 

Type I These are the most common, at about 75% of paediatric Monteggia fracture-dislocations.  Proximal ulna fracture with anterior dislocation of the radial head.
Type II These are rare in children. Proximal ulna fracture with posterior dislocation of the radial head.
Type III These are the second most common type of Monteggia fractures in children. Proximal ulna fracture with lateral dislocation of the radial head.
Type IV In addition to the ulna fracture, the proximal radius is also fractured. Like type I’s, the radial head is dislocated anteriorly.

Bado classification of Monteggia injuries from Life In The Fast Lane

 

Treatment

The priority is for urgent orthopaedic assessment.  All Monteggia fracture-dislocations will require an urgent reduction of the radial head dislocation.  In the ED, give analgesia, immobilize in an above-elbow cast for comfort then call the orthopaedic surgeon on-call.

With early recognition and treatment of Monteggia fracture-dislocations, children usually achieve a good long-term result.  The radial head dislocation must be reduced by an orthopaedic surgeon as soon as possible. In most paediatric cases, a closed reduction under general anaesthesia can be done, but sometimes open reduction of the radial head dislocation and internal fixation of the ulna fracture are needed.   Ring and Waters describe a treatment strategy based on the type of ulna fracture pattern, which has been found to be effective and lead to minimal complications.

 

Ulna fracture pattern Treatment

Incomplete fracture with stable length

Plastic deformation

Greenstick

Closed reduction

Complete fracture with stable length

Transverse fracture

Short oblique fracture

Intramedullary pin fixation

Complete fracture with unstable length

Long oblique fracture

Comminuted fracture

Open reduction with plate fixation

Complications 

Complications post-treatment are rare (5% in one retrospective study of 112 patients) and include nerve injury, ulnar non-union, and compartment syndrome.  The radial nerve and posterior interosseous nerve are the most commonly injured nerves.

Most complications arise from missed or delayed diagnoses of Monteggia fracture-dislocations.  Undiagnosed radial head dislocations over 2-3 weeks can require more challenging and invasive surgical intervention and are at higher risk of complications.   Complications in these cases include recurrent radial head dislocations, persistent subluxations, and loss of normal elbow function.

 

Emiko was assessed by the orthopaedic surgeon and underwent a closed reduction of her Type I Monteggia fracture-dislocation under general anaesthetic. She made a good recovery thanks to the diagnosis being correctly identified. Emiko can now continue towards her goal of being a mixed martial arts world champion!

 

Selected references

Johnson NP, Silberman M. Monteggia Fractures. [Updated 2019 Jan 20]. In: StatPearls. Treasure Island (FL): StatPearls Publishing; 2019 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK470575/

Bell DJ, Stanislavsky A et al. Galeazzi and Monteggia fracture-dislocations (mnemonic). Radiopaedia. Available from: https://radiopaedia.org/articles/galeazzi-and-monteggia-fracture-dislocations-mnemonic?lang=gb (last accessed May 2019)

Beaty JH, Kasser JR. Rockwood & Wilkins Fractures in Children. 7th ed. Philadelphia, PA: Lippincott Williams & Wilkins; 2010

Ring D, Waters PM. Operative fixation of Monteggia fractures in children. J Bone Joint Surg Br 1996;78:734–9.

Ramski D, Hennrikus W et al.  Pediatric Monteggia Fractures: A Multicenter Examination of Treatment Strategy and Early Clinical and Radiographic Results. J Pediatr Orthop.  Vol 35(2), March 2015, p 115-120

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About Rie Yoshida

AvatarRie is a paediatric registrar in South London with an interest in emergency medicine and global health.  Other interests include wine tasting, escape rooms and a secret love of karaoke.

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Author: Rie Yoshida Rie is a paediatric registrar in South London with an interest in emergency medicine and global health.  Other interests include wine tasting, escape rooms and a secret love of karaoke.

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