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Baumann Angle for Elbow Joint Alignment

The Baumann angle (also called Humerocapitellar angle) serves as an essential indicator of the alignment and growth of the elbow joint. It is an important aid for the accurate reduction of a supracondylar humeral fracture in children. It also provides valuable insights into the development of the distal humerus and can help identify various conditions and abnormalities.

What is Baumann angle?

The Baumann angle is formed by the longitudinal axis of the humerus and a straight line through the epiphyseal plate of the lateral condyle (capitulum) of the humerus.

How do you measure a Baumann angle?

Measuring the Baumann angle requires an X-ray of the elbow joint. Here’s a step-by-step guide on how to measure it:

  1. Obtain an X-ray: A standard X-ray of the elbow joint is required. This X-ray should include a true lateral view of the elbow, with the patient’s arm fully extended and the palm facing inward.
  2. Identify the landmarks: On the X-ray, locate the following landmarks:
    1. Humerus
    2. Capitellum
  3. Draw reference lines: Using a ruler or a straight edge, draw two reference lines on the X-ray image:
    1. Line 1: Draw a line parallel to the long axis of the humerus bone, extending from the center of the humerus.
    2. Line 2: Draw a line parallel to the long axis of the capitellum, passing through the center of the capitellum.
  4. Measure the angle formed between Line 1 and Line 2.
See Also: Elbow Examination
measure a Baumann angle
Baumann Angle:
a- Longitudinal axis of the humerus
b- Axis through the epiphyseal plate of the lateral epicondyle
α- Baumann Angle

What is the importance of Baumann angle?

Baumann angle can indicate certain conditions or developmental issues in children, such as:

  1. Cubitus varus: This condition refers to an inward angulation of the forearm in relation to the upper arm, creating a “gunstock” deformity. A decreased angle is often observed in cubitus varus.
  2. Cubitus valgus: In contrast to cubitus varus, cubitus valgus involves an outward angulation of the forearm. An increased angle may be indicative of cubitus valgus.
  3. Supracondylar fractures: These fractures are a common pediatric injury. Evaluating the Baumann angle can aid in assessing the alignment and guiding treatment decisions.
Baumann angle xray

What is the normal Baumann’s angle of the elbow?

Normal values of the Baumann angle in the paediatric population have been reported to range between 9° and 26°.

One study demonstrates that the Baumann angle of the humerus is a highly reliable measurement, with excellent inter-observer and intra-observer reliability values (r = 0.78 and r = 0.80, respectively). In most instances, measurements of the Baumann angle of the humerus (by different observers, as well as by a single observer on multiple occasions) were within 7° of each other. Therefore, a difference of up to 7° in the measurement (by a single or multiple observers) should be considered to be within the normal error of the measurement.

See also: Knee Q Angle Measurement

References

  1. Williamson DM, Coates CJ, Miller RK, Cole WG. Normal characteristics of the Baumann (humerocapitellar) angle: an aid in assessment of supracondylar fractures. J Pediatr Orthop 1992;12(5):636-639.
  2. Silva M, Pandarinath R, Farng E, Park S, Caneda C, Fong YJ, Penman A. Inter- and intra-observer reliability of the Baumann angle of the humerus in children with supracondylar humeral fractures. Int Orthop. 2010 Apr;34(4):553-7. doi: 10.1007/s00264-009-0787-0. Epub 2009 May 8. PMID: 19424695; PMCID: PMC2903132.
  3. Omid R, Choi PD, Skaggs DL. Supracondylar humeral fractures in children. J Bone Jt Surg Am. 2008;90:1121–1132. doi: 10.2106/JBJS.G.01354
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