Taking a Good Cast

 


The Heel Bisection Technique

The reliability of heel bisections has rightfully been questioned and is likely due to improper or inconsistent technique. Unfortunately there seems to be a lack of documentation and standardization of heel bisection technique. This author proposes that the following method of constructing heel bisections be adopted as the standard technique and believes that doing so will result in improved accuracy and greater repeatability in heel bisection.

To bisect the heel:

  1.  
    Figure 1
    Figure 1
     
     
     
    Figure 2
     
     
     
    Figure 3
    Figure 3
     
     
     
    Figure 4
    Figure 4
     
     
     
    Figure 5
    Figure 5
     
     
    Position the patient prone and view the posterior aspect of the heel from directly above.
  2. Grasp the 4th and 5th metatarsal heads and apply a dorsiflexion force to the plantar, lateral aspect of the forefoot with your thumb (ie. right foot-right thumb). Fully pronate the midtarsal joint (MTJ) and move the subtalar joint (STJ) into the neutral position.
  3. To locate the neutral position of the STJ, maintain the MTJ fully pronated and then supinate and pronate the STJ through the neutral position. Pronate the STJ back to the neutral position and confirm the neutral position by observing the parallelism between the curves above and below the lateral malleolus, and by talar palpation, if desired. As you dorsiflex the forefoot and move the STJ, the forefoot is said to describe an arc in space. You should be able to feel the neutral position as the low point or flat spot within the arc of motion.
  4. Using the tips of both index fingers, simultaneously palpate the superior, medial and lateral margins of the posterior aspect of the calcaneus (see figure 1).
  5. Using a ballpoint pen or indelible pencil, begin to construct a midsagittal heel bisection by drawing a short line segment midway between the tips of both fingers (see figure 1).  Repeat this process by moving just inferior to the previous line segment until there are a series of three or four short line segments running vertically on the superior, posterior aspect of the heel (see figures 2 and 3).  Be sure to palpate and bisect only the superior half of the posterior aspect of the calcaneus (see figure 3).
  6. To ensure accuracy, place the STJ in the neutral position and re-palpate the superior half of the heel and visually confirm that each line segment was placed midway between the tips of both fingers.
  7. Complete the bisection by drawing an extension of the existing bisection down the lower half of the heel without further palpation (see figure 4).
  8. Note: The heel bisection should represent only the superior half of the posterior aspect of the calcaneus. Palpating the inferior half of the posterior aspect of the calcaneus can result in bisection errors due to the irregular and inconsistent shape of the inferior aspect of the calcaneus which results in part, from the presence of the medial tubercle and the relative absence of bone laterally.
  9. Utilize the heel bisection to observe or measure the forefoot to rearfoot relationship. The plantar plane of the forefoot and the sagittal plane bisection of the heel have a distinct angular relationship when the STJ in the neutral position and the MTJ is fully pronated. A neutral position cast of the foot should closely resemble the same forefoot to rearfoot relationship that was found on examination. If a neutral position cast of the foot does not demonstrate the same forefoot to rearfoot relationship seen on examination, a casting error should be suspected and recasting is highly recommended.

 

 

 

 

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