Munchkin Radiography Study

Lead contact: Leslie A. Lyons, PhD (lyonsla@missouri.edu)

The Feline Genetics Laboratory at the University of Missouri is studying the clinical presentation and the genetics of dwarf cats, most commonly known as Munchkins.  One complication of dwarfism is extreme bowing of the limbs, thus, we are examining radiographs of normal, standard leg length cats and comparing to the presentation of dwarf cats.  An overall goal is to provide guidance for the limb standards of dwarf cats to prevent the breeding and production of cats with functional disabilities.

The genetic study of the dwarf cats is well underway and we are looking for a causal mutation for the chondrodysplastic presentation.  Buccal swabs and pedigrees are always welcome to support this aspect of the study.

In addition, we are performing a radiographical (X-rays) study of the forelimbs (front legs) of the dwarf cats.  We can accept images from anywhere in the world, provided the images are of good quality and are taken at the suggested angles below.  The sedation of the cat is very important.  We can further discuss the techniques below with your participating veterinarian.

Please contact us if you are interested in participating!

Criteria

• Adult (over 8 months of age), breed-certified Munchkin cats
  • Completely closed physes of the forelimb bones
  • No history of bone or joint disease
  • No history of disease that would cause sedation risk
  • Thorough history of any bone or joint abnormality signs (ambulation, posture, vertical jumping ability, etc.) strongly recommended
• Digital images required. Film images may be scanned and sent via digital media to be analyzed.
  • All images must be in .png or .tif file format for optimal visualization

 

Radiography Technique

• Adherence to the following guidelines is strongly recommended; however, orientation of chondrodysplastic limbs may limit the ability to orient them into proper positioning. Technique must be followed as closely as possible without causing undo pain or stress on the forelimbs.

• Sedation is required for all cats to ensure appropriate radiographic position
  • Recommendation: Dexmedetomidine @ 40 mcg/kg IM
    • Atipamazole highly recommended as a reversal agent
  • Sedation should be to a plane in which cats are still conscious of their surroundings but can be manipulated to take appropriate images. This is to ensure that the forelimb remains in a normal orientation for imaging.
• Both forelimbs must be imaged, inclusive of the shoulder joint and metacarpals
• Frontal plane and sagittal (lateral) plane images required for both limbs
• Standards for proper orientation of the limb during imaging are as follows:

Humerus & Radius

Proper positioning requires an ‘elbow straight’ view:

 

Frontal Plane Positioning

• Lack of appearance of the medial or lateral surfaces of the anconeal process
  • Eliminates limb rotation
• Elbow Rotational Position
  • B = transcondylar distance
  • A = medial epicondyle to medial cortex of olecranon distance
  • Ratio A/B = ~ 40-45%

 

Sagittal Plane Positioning

• Scribed circles over the medial and lateral aspect of the humeral condyles
  must be CONCENTRIC and not intersect