Midshaft radius and ulna fractures

Cite this article as:
Rie Yoshida. Midshaft radius and ulna fractures, Don't Forget the Bubbles, 2021. Available at:
https://doi.org/10.31440/DFTB.21902

Alvaro is a 12-year-old boy who presents to the ED with a painful and swollen right arm. He was trying out his new skateboard and fell whilst trying to master the kickflip. (He tells you it’s not cool to say he’s been skateboarding: “It’s skating, but not the on-ice kind, that’s not cool either.”)

On examination, he is tender in the middle third of his right forearm with swelling and some mild deformity.  There are no open wounds. There is pain on forearm rotation with limited pronation and supination but a good range of movement at the wrist and elbow.  There are no signs of neurovascular compromise or compartment syndrome. 

You top him up with some intranasal fentanyl and send him for an x-ray. His AP film shows a greenstick in the middle third of the ulna. 

Case courtesy of Dr. Jeremy Jones, Radiopaedia.org. From the case rID: 66836

But when you look at his lateral you do a double-take. There’s pretty significant angulation with radial bowing. You always make sure you look at both x-ray views but this really shows why that’s so important.

Case courtesy of Dr. Jeremy Jones, Radiopaedia.org. From the case rID: 66836

You know that ulna fractures can be associated with radial head dislocations as part of the Monteggia fracture-dislocation pattern so send Alvaro back for an elbow x-ray.  Radio-capitellar alignment is maintained so you’re happy this isn’t a Monteggia injury but given the significant ulna angulation, you give your orthopaedic on-call colleague a ring.

 

Epidemiology

Forearm fractures are the most common fractures in children, representing 40% of all childhood fractures. Although the majority of these occur at the distal end of the forearm, 20% are located at the midshaft and often involve both bones.  Peak incidence occurs between ages 10-14.

 

Anatomy

The radius and ulna are connected by an interosseous membrane and meet at the distal and proximal radioulnar joints at the wrist and elbow.  Due to these connections, a break in one bone is often accompanied by a break in the other.  It is also important to look at the proximal and distal radioulnar joints to identify Monteggia and Galeazzi fracture-dislocations.

Mechanism

Midshaft radius and ulna fractures usually occur due to a fall from a height onto the forearm or an outstretched hand or direct blow to the forearm.

 

Examination findings

Examine the forearm, wrist and elbow joint.  You may find swelling and possible deformity with tenderness of the forearm. Check for any open wounds and check the tetanus status of the child.

The range of movement will be reduced, particularly with forearm pronation and supination. Check for signs of neurovascular compromise or compartment syndrome.

 

Investigations

For all midshaft forearm injuries, order true AP and lateral x-rays of the forearm including the wrist and elbow (including distal humerus). Note: 5% of forearm fractures are associated with supracondylar fractures.

In a true AP x-ray, the distal radius (R) and ulna (U) should be visualized with minimal overlap. The trochlea (T) and capitellum (C) should be seen in profile, as long as the child is old enough for them to have both to have ossified.

In a true lateral, the distal radius (R) and ulna (U) will be superimposed at the wrist.  If there is no plastic deformity the posterior border of the ulna is straight, sitting on an imaginary horizontal line, and the radius is bowed. The trochlea and capitellum will be superimposed at the elbow (denoted by *).

True AP: Case courtesy of Dr. Aditya Shetty, Radiopedia.org, rID:31106 True lateral: Case courtesy of Dr. James Hayes and Dr. Aditya Shetty, Radiopedia.org, rID:31107

 

Classification

The Rule of Fours can be used to describe the fracture and identify the correct fracture pattern.

There are 4 types of fracture patterns:

  • Plastic deformation: there is bowing of the bone with no cortex disruption. It’s most commonly seen in the ulna and is easily missed on x-ray. A top tip for spotting on x-ray: on the lateral view, a normal ulna has a straight posterior border.  But if the posterior border does not sit nicely on a horizontal line there is plastic deformation.

  • Greenstick fractures: there is a break on one side of one bone that does not extend all the way through the bone.
  • Complete fractures: there is a fracture through both cortices of the radius and/or ulna, often with displacement.
  • Comminuted fractures: these are fractures with multiple bony fragments. They are uncommon in midshaft fractures in children.

 

Treatment

The vast majority of paediatric forearm fractures can be managed non-operatively, with closed reduction and casting.

Firstly, check whether the fracture needs to be referred to the orthopaedic team. Any fracture with complications, either a plastic, comminuted or open fracture or one with neurovascular compromise, compartment syndrome or associated Monteggia or Galeazzi dislocation, must be referred to the on-call orthopaedic clinician.

Next, assess the degree of angulation. If the child is under 5 years of age, up to 20 degrees angulation is acceptable; aged 5 – 9 up to 15 degrees is allowable; and in children 10 years and older fractures with angulation of up to 10 degrees will remodel without manipulation. Fractures that are more angulated than this will need to be reduced.

Closed reduction should be performed by an experienced ED practitioner or clinician or by the orthopaedic team.  It may be done either under procedural sedation in the ED or in theatre with image intensification if this fails (or if the fracture is complicated).  Always, always, reassess neurovascular status and repeat an x-ray after manipulation to reassess the degree of angulation and ensure no further complication has arisen. And finally, an above-elbow (long arm) cast should be applied with follow-up in fracture clinic within a week.

 

Indications for orthopaedic referral

  • Open fracture
  • Neurovascular compromise
  • Compartment syndrome
  • Comminuted fracture
  • Monteggia or Galeazzi fracture
  • Failed reduction or unable to perform in the ED

 

Top tips

  • Always check both lateral and AP films. Alignment can look deceptively good in one plain and very angulated in another.
  • If a break in one forearm bone is identified, remember to look at the other bone and the radioulnar joints. Don’t forget forearm fractures are associated with supracondylar fractures and can be complicated by Monteggia or Galeazzi fracture-dislocations.

 

Alvaro’s ulna greenstick fracture had over 10 degrees of angulation and you and your orthopaedic colleague agree a closed reduction in ED is called for.  You manage Alvaro’s procedural sedation while the orthopaedic doctor re-moulds the fracture and places Alvaro in an above elbow backslab.  Post-reduction films show good alignment.  A few months later you’re walking past the local skate park and you smile to yourself as you see Alvaro with his skateboard (correction, on his board). He gives you a grin as he spins into a kickflip.

 

Selected References

Vopat, Matthew L et al. “Treatment of diaphyseal forearm fractures in children.” Orthopedic reviews vol. 6,2 5325. 24 Jun. 2014, doi:10.4081/or.2014.5325

Orthobullets Both Bone Forearm Fracture – Pediatric https://www.orthobullets.com/pediatrics/4126/both-bone-forearm-fracture–pediatric

Schweich P. Midshaft forearm fractures in children. Post TW (Ed). UpToDate, Waltham, MA. 2019.

Price CT. Acceptable alignment of forearm fractures in children: Open reduction indications. J Pediat Ortho 2010; 30: S82-4.