What is the Mnemonic for the Elbow Ossification Centers?

Patient Presentation
A 12-year-old male came to clinic with a 5 day history where he had been playing around with his brother and fell on his arm. He is unclear of the exact position, but says that it was away from his body and slightly behind. He did not hear or feel a “popping” sensation, but had pain right away. There was mild pain and swelling of the elbow, but in the past day the swelling has increased along with bruising of the area. The past medical history is non-contributory.

The pertinent physical exam shows a healthy male with normal growth parameters and is Tanner II. His left elbow has marked generalized swelling and bruising especially posterior and distal to the elbow. He can extend the elbow to approximately 110 degrees. Forearm supination and pronation do not appear to be specifically affected. Distal pulses, wrist and hand movements are intact. The radiologic evaluation of a plain AP and lateral radiolograph showed an anterior fat pad sign due to hemarthosis without a specific fracture identified. All ossification centers were ossified. Contralateral views were ordered and again no specific fractures when compared were seen. The diagnosis of an elbow injury with hemarthosis was made. The patient was seen by the orthopaedic service and placed into a sling for one week of immobilization. At that time he had decreased swelling and the repeat films showed no fracture but with decreased range of motion because of pain. He was referred to physical therapy for range of motion exercises and was to followup in 3 weeks.

Case Image

Figure 94 – AP and lateral radiographs of the left elbow show elevation of the anterior fat pad, indicating the presence of a hemarthrosis. No definite fracture is identified.

Injuries to the pediatric elbow are difficult to diagnose because of the anatomy and normal growth and ossification of the elbow.
Swelling, tenderness, ecchymosis, with or without deformity are common signs of fracture. Physical examination should include a careful neurovascular examination for distal pulses and capillary refill, paresthesias, increased pain with movement distal to the elbow or paralysis of the hand muscles as any of these may indicate compartment syndrome.

Common radiographs obtained are AP and lateral plain radiographs. Oblique films and comparison films of the contralateral elbow are also often needed to distinguish between a fracture and normal growth plate. The alignment of the anterior humerus line and the fat pads should be reviewed as misalignment may indicate occult fracture. Subtle fractures such as torus and nondisplaced fractures can be very difficult to determine. An effusion may or may not indicate a fracture.

Treatment for many fractures includes immobilization and casting for minimally displaced fractures. All non-minimally displaced fractures require urgent orthopaedic referral, and may require open reduction and/or fixation. Close orthopaedic follow-up is recommended for almost all elbow fractures.

Supracondylar fractures are 50% of elbow fractures and are usually caused by a fall on an outstretched arm. Posterior displacement of the distal fracture piece or posterior angulation usually occur but can be subtle. Complications can include range of motion and neurovascular problems.

Lateral condylar fractures are caused by a fall on an extended and abducted arm. They are Salter-Harris IV fractures because they involve an articulating surface, and therefore may have poorer outcomes. Treatment includes immobilization and casting, but may require surgical pinning with increased displacement of the fracture.

Medial epicondylar fractures usually occur with falls on an outstretchened arm or an extended and abducted elbow.

Distal humerus physeal fractures usually occur in young children and may be caused by child maltreatment. Posterior displacement of the radius and ulna relative to the humerus is a common finding.

Olecranon fractures that are isolated are uncommon. They usually occur with other elbow injuries especially dislocation or fracture of the radial head. Difficulties with elbow extension and hemarthosis is common, but visualization of the fracture may be difficult with only fat pad abnormalities seen.

Radial head and neck fractures occur with a fall on a supinated outstretch arm. These are usually Salter-Harris I and II or pure metaphyseal fractures. Like olecranon fractures they are often associated with other fractures.

Elbow dislocations are uncommon but are the most common joint dislocated in children and adolescents. It occurs by a fall on a supinated forearm with an extended or partially flexed arm (i.e. backward fall). The radius and ulna are usually laterally and posteriorly displaced. Neurovascular problems can be associated and need prompt treatment and close followup.

Radial head subluxation or nursemaid’s elbow is the most common problem involving the elbow. It usually occurs when a pronated and extended arm has axial traction applied. Early reduction can decrease the pain and anxiety of the patient and family. For more information please review What Methods Can Be Used to Reduce Radial Head Subluxation?.

Learning Point
CRMTOL is a commonly used mnemonic used to describe the usual order of appearance of the elbow ossification centers. The average age when they are seen is also given below.

  • Capitellum – 3 months
  • Radial head – 4.5 years
  • Medial epicondyle – 5 years
  • Trochlea – 8 years
  • Olecranon – 9 years
  • Lateral epicondyle – 10 years

Questions for Further Discussion
1. What is the technique for replacing a dislocated elbow?
2. How common are shoulder dislocations in children?

Related Cases

To Learn More
To view pediatric review articles on this topic from the past year check PubMed.

Evidence-based medicine information on this topic can be found at SearchingPediatrics.com, the National Guideline Clearinghouse and the Cochrane Database of Systematic Reviews.

Information prescriptions for patients can be found at MedlinePlus for these topics: Elbow Injuries and Disorders and Arm Injuries and Disorders.

To view current news articles on this topic check Google News.

To view images related to this topic check Google Images.

Fleisher GR, Ludwig S. Synopsis of Pediatric Emergency Medicine. Williams and Wilkins. Baltimore, MD. 1996:676-679.

Pritchett JW, Porembski MA. Olecrenon Fractures. http://emedicine.medscape.com/article/1231557-overview(rev. 6/7/11, cited 11/16/11).

Shore RM, Grayhack J. Imaging in Pediatric Elbow Trauma. http://emedicine.medscape.com/article/415822-overview(rev. 4/11/11, cited 11/16/11).

Keany JE, McKeever D. Elbow Dislocation in Emergency Medicine Clinical Presentation. http://emedicine.medscape.com/article/823277-clinical(rev. 7/20/2011, cited 11/16/11).

ACGME Competencies Highlighted by Case

  • Patient Care
    1. When interacting with patients and their families, the health care professional communicates effectively and demonstrates caring and respectful behaviors.
    2. Essential and accurate information about the patients’ is gathered.
    3. Informed decisions about diagnostic and therapeutic interventions based on patient information and preferences, up-to-date scientific evidence, and clinical judgment is made.
    4. Patient management plans are developed and carried out.
    5. Patients and their families are counseled and educated.
    7. All medical and invasive procedures considered essential for the area of practice are competently performed.
    8. Health care services aimed at preventing health problems or maintaining health are provided.
    9. Patient-focused care is provided by working with health care professionals, including those from other disciplines.

  • Medical Knowledge
    10. An investigatory and analytic thinking approach to the clinical situation is demonstrated.
    11. Basic and clinically supportive sciences appropriate to their discipline are known and applied.

  • Interpersonal and Communication Skills
    19. The health professional works effectively with others as a member or leader of a health care team or other professional group.

  • Systems Based Practice
    24. Cost-effective health care and resource allocation that does not compromise quality of care is practiced.
    25. Quality patient care and assisting patients in dealing with system complexities is advocated.


    Donna M. D’Alessandro, MD
    Professor of Pediatrics, University of Iowa Children’s Hospital