Uncompensated rearfoot varus is one of the many conditions that need to be evaluated when defining the surgical plan for a high arch foot (cavus foot) or in cases of lateral ankle instability. Rearfoot varus is evaluated with the patient facing away from you while standing. In cases of rearfoot varus, the heels will appear to roll in as follows; \ /. Uncompensated rearfoot varus describes rearfoot varus that cannot be manually reduced to a vertical position; l l . The degree of rearfoot varus is often evaluated with x-ray view called a ski jump or Isherwood view.Â
If uncompensated rearfoot varus is found to be a contributing factor to the cavus deformity or lateral ankle instability, surgical treatment choices include either a Dwyer osteotomy of transpositional osteotomy of the calcaneus. Let’s take a look at both of these and see how they compare.
The Dwyer osteotomy is performed with the patient in a lateral position. The incision is placed parallel to the peroneal tendons. Dissection is carried down to bone and periosteum is reflected. A saw is then used to perform a wedge in the calcaneus. The wedge is wide on the lateral side of the heel. Typical size of the wedge is 1-2 cm. Upon removal of the wedge, the foot can be dorsiflexed against the resistance of the Achilles to close the wedge. With an intact medial hinge, the wedge will close. The wedge is then feathered with a saw and fixated. Alternatives for fixation include a table staple, fixation plate or screws.
A transpositional osteotomy, or what is often referred to as a calcaneal slide follows the same surgical approach and dissection. The transpositional osteotomy requires minimal dissection of periosteum and can therefore use a smaller incision. The osteotomy is intentionally through and through meaning that there is no need to try to maintain a medial hinge. The amount of transposition can be easily seen by the surgeon prior to fixation. Fixation is achieved by use of staples, screws of specially designed plates that can be fixated in pre-determined amount of step down.
Which osteotomy is better? I think the answer will vary on a surgeon by surgeon basis, but you’ll tend to see that more doctors are using the calcaneal slide procedure and less the Dwyer. The Dwyer will tend to have several disadvantages. First, the Dwyer requires more dissection. Second, resection of the wedge in the Dwyer will shorten the heel. Shortening of the heel will no be measurable on x-ray or when the patient returns to shoes, but it will none-the-less affect stability and gait. The Dwyer is also a more difficult osteotomy to perform. And lastly, the rotational motion created by removal of the wedge in the Dwyer will result in a change in the weight bearing surface of the heel. I’ve not see complications due to a change in the weight bearing surface of the heel post Dwyer, but I think this change would be subtle. Symptoms may include changes in the gait pattern or the sensation of pain in the way that load is applied to the plantar fat pad of the heel once a patient returns to weight bearing.
There’s really no right or wrong in the choice of Dwyer v.s. transpositional osteotomy of the calcaneus, but from the standpoint of ease of the procedure and getting folks back on their feet sooner, I think you’ll see the calcaneal slide being used by most surgeons these days.
Jeffrey A. Oster, DPM
Chief Medical Officer
Myfootshop.com
Dr. Oster follows the Myfootshop.com on-line communication policy and cannot answer clinical questions or provide medical care through this blog.