Current Considerations With Heel Lifts, Top Covers And Rearfoot Posting

What is the most optimal approach for using heel lifts in patients with limb length discrepancy? What are the best materials for top covers? What kind of rearfoot correction/posting should you use for extreme supinators? Expert panelists tackle these questions and much more in this discussion on heel lifts, rearfoot posting and top covers.

Q:

What strategies do you use for using heel raises and heel lifts effectively in your orthotic prescriptions?

A:

Robert Phillips, DPM, Paul Langer, DPM, and Dianne Mitchell-Pray, DPM, all note the use of heel lifts for limb length discrepancy. Prior to adding an intrinsic heel lift to custom foot orthoses, Dr. Langer typically employs an adjustable heel lift in order to determine the optimal amount of height. He will have patients use the adjustable heel lift with an OTC insole or their current custom device for two to four weeks. Once Dr. Langer determines the most comfortable level of height, he incorporates this into the new device.

“I always inform my patients that we cannot add much more than 1 cm or approximately half an inch inside of a standard shoe,” notes Dr. Langer. “If the patient’s pathology requires more than that, then we would have to add some or all of the lift to the shoe itself.”

Most of the time, Dr. Phillips finds that the shorter leg has less passive ankle joint dorsiflexion than the longer leg so he can justify putting the lift only under the heel. He notes he will often order a radiologic leg length study to confirm the exact anatomical difference.

“I will then start at about half the difference and then titrate it up or down to patient comfort level and/or symptomatic relief,” says Dr. Phillips.

Richard Blake, DPM, says clinicians should separate the heel lift from the orthotic itself until deciding exactly how much lift to use. When one first dispenses the orthotic, if the heel lift is firmly attached and there are adjustment problems, Dr. Blake says it is hard to know if these problems are from the orthotic device or the heel lift.

Noting that she sees a lot of limb length discrepancies, Dr. Mitchell-Pray says for symptomatic cases, one can achieve good outcomes by adding a heel lift to the rearfoot post of an orthotic device on the shorter limb. In regard to materials, she uses either high durometer ethylene vinyl acetate (EVA) or Korex, adding that both materials retain their shape well. Dr. Mitchell-Pray also keeps heel lifts at 6 mm or less.

“Beyond this thickness, I find shoe fit problems,” notes Dr. Mitchell-Pray. “Specifically, patients get heel slipping or they walk out of their shoe.”

In his experience, Dr. Blake has found that “heel lifts are often more unstable than full-length lifts” for limb length discrepancy. When one places a lift under the heel, Dr. Blake says more heel slippage (sagittal plane) or more medial lateral instability (frontal plane) can occur. He adds that he likes to use power lacing with any heel lift to hold the foot in the shoe better.

In regard to other conditions for which heel lifts may be helpful, Drs. Langer and Phillips point to significant or severe equinus, Dr. Blake adds Achilles strain to the list and Dr. Mitchell-Pray may prescribe a heel lift in cases that require removal of an impingement or reduction of tension. She says examples include anterior ankle impingement, as one would see with cavus feet, Achilles insertional or mid-substance tendonosis, or equinus.

“A heel lift can work nicely to reduce pain by either opening up the anterior ankle or reducing tension to the distal Achilles tendon distribution respectively,” explains Dr. Mitchell-Pray.

When using heel lifts for Achilles strain, Dr. Blake recommends bilateral lifts for balance. Dr. Phillips also occasionally utilizes bilateral lifts in cases of spastic equinus or severe ankle equinus.

Dr. Blake also cautions that heel lifts and even rearfoot posts on orthoses can cause the force of heel contact to irritate the heel, especially if heel pain already exists. If a patient has heel pain, Dr. Blake says podiatrists should be willing to remove the heel lift or heel post to see if it dramatically reduces the pain. Once the pain is resolved, Dr. Blake says one can reattach the heel lift or post.

All orthoses with rearfoot posts cause a natural shift of weight forward, making propulsion easier, according to Dr. Blake. When you add the traditional shoe with 10-12 mm heel drop, Dr. Blake says propulsion gets even easier.
“With lowered heels in many shoes, down to zero-drop shoes, when you sense that propulsion is harder, a ¼ inch (6 mm) heel lift in the shoes can really help many patients mechanically,” maintains Dr. Blake.

Q:

What are your opinions on the use of top covers/soft tissue supplements at the foot/orthosis interface?  

A:

Top covers are necessary when there is a loss of soft tissue mass and/or soft tissue biomechanical function, according to Dr. Phillips. He says diabetes is a common reason for additional soft tissue covers due to a loss of muscle mass (which provides important cushioning effects); loss of fat pads covering the heel and the metatarsus; and stiffening of the collagen fibers in the fat pads to the point where they are less pliant and concentrate force more under the bony prominences on the plantar aspect.

“If a person has normal muscle mass, normal fat pad mass and pliancy, no top cover is necessary,” says Dr. Phillips. “Unfortunately, objective clinical methods for measuring mass and biomechanical function of fat pads are not highly available or utilized.”

Dr. Mitchell-Pray notes that podiatrists may employ top covers for:

• padding of the heel and forefoot for comfort;
• coverage of a shell accommodation, such as a plantar fascia groove or navicular sweet spot; and
• creation of an attachment site for a forefoot extension, such as a reverse Morton’s extension.

Dr. Blake agrees that top covers can help protect a variety of orthotic modifications, including heel cushions, cuboid raises and Kirby skives. In general, Dr. Blake notes that top covers also provide stability when they are firmly attached to the orthosis. He emphasizes that the stability of a top cover just 1 inch past the end of the orthotic device is “especially important in a narrow orthosis.”

In regard to choosing materials for top covers, Dr. Mitchell-Pray says one has to consider the patient, his or her expectations, and what you are trying to achieve clinically. For children, she may utilize a waterproof polypropylene shell and post the device with no top cover. Athletic shoes are another factor to consider as they may range from a low volume soccer cleat to a cycling shoe that only accommodates graphite. In these cases, Dr. Mitchell-Pray says her top cover will be vinyl with either no padding or a thin, 1.5 mm layer of Poron, for example.

“Most of the time, I am pulling the sock liner out of an athletic shoe and replacing the inside of the shoe with my orthotic device so I want a full-length top cover to have a uniform material contacting the plantar foot,” notes Dr. Mitchell-Pray.

Dr. Blake adds that top covers can be full-length, sulcus length or orthotic length based on shoe fit issues and tightness concerns with the toes.

Top covers can significantly improve comfort, according to Dr. Langer. His personal preference for top cover material is neoprene.

“(Neoprene) is more durable and less prone to compression set than some other materials without being too bulky, especially for athletes,” notes Dr. Langer.

For shoes with removable insoles, Dr. Langer uses a ¼ inch thickness, full-length top cover and incorporates a 1/8 inch neoprene shell length for lower profile footwear. He likes using leather top covers for dress shoes but does not like Naugahyde because it tends to crack and fragment in a short amount of time.

For additional cushioning and accommodation, Dr. Langer says Poron is very useful, and often utilizes it as a forefoot extension for forefoot pathologies. He adds that metatarsal pads are very helpful but he always instructs the orthotics lab to leave the metatarsal pads and top cover unglued so he can place them himself. Dr. Langer says this allows him to fine-tune these additions to help ensure optimal comfort and pain relief.

In regard to soft tissue supplements at the foot to orthotic interface, Dr. Mitchell-Pray periodically uses polytetrafluoroethylene (PTFE). She says the PTFE material has a very low coefficient of friction, which helps to reduce shear stress, which subsequently reduces the risk of blister, callus and even ulcer formation. Applying it on top of the orthotic top cover at the site of irritation, Dr. Mitchell-Pray has achieved good outcomes using PTFE in both athletes and the diabetic population. Dr. Blake adds that he utilizes soft tissue supplements in all orthoses for patients over 70 years of age and in many orthoses for thinner patients earlier in life.

Q:

How do you determine the amount of rearfoot correction/posting you order in a custom foot orthosis prescription?  

A:

The purpose of a rearfoot post is to add stability to the orthotic device, according to Dr. Mitchell-Pray. She says one has to determine how much stability is necessary and consider the type of shoe that the patient will primarily use with the orthotic. Moving from the least aggressive to the most aggressive, Dr. Mitchell-Pray notes she can spot, strip, standardize or distally extend the rearfoot post further into the arch of the orthotic. The larger the rearfoot post, she says there is larger surface contact with the shoe and increased stability as a result.

Dr. Mitchell-Pray utilizes all types of rearfoot posts in her practice. For those with low profile shoes, she says a spot post or strip post offers the best fit. For a standard running or walking shoe, Dr. Mitchell-Pray prescribes a standard rearfoot post, flat with no motion and made with high durometer EVA or polypropylene. She does add that the orthotic will still have a few degrees of frontal plane motion simply due to the construction of the athletic shoe.

Dr. Langer prefers to use the Foot Posture Index to quantify static alignment along with dynamic and pathology-specific exams to determine rearfoot posting. For highly pronated feet or highly mobile feet, he uses rearfoot posting of 5 degrees or more. For pathologies such as posterior tibial tendon dysfunction, Dr. Langer tends to use high degrees of rearfoot correction as well. When it comes to patients with moderately pronated/hypermobile feet, he typically uses 0-4 degrees of posting and also utilizes the Kirby skive. For forefoot pathologies with little to no hypermobility issues, Dr. Langer does not add rearfoot posting.

Emphasizing his use of Root terminology when instructing an orthotic laboratory on rearfoot posting, Dr. Phillips says he will have the laboratory add whatever forefoot posting is necessary to bring the heel to “x” degrees inverted or everted. He notes the heel is most stable when it is vertical. Accordingly, if the patient can stand with the heel vertical and the subtalar joint is not at its end range of motion, Dr. Phillips usually asks the lab to post the orthotic to bring the heel to the vertical position.  

If the patient stands in static stance with the heel vertical but the subtalar joint is fully pronated, he asks the orthotic lab to post to make the heel 2 degrees inverted. If the patient stands with the heel inverted and the subtalar joint fully pronated, Dr. Phillips asks the lab to post the orthotic to a point that is 2 degrees more inverted than the fully pronated position in static stance. For example, if the heel is 2 degrees inverted in static stance and the subtalar joint is fully pronated, Dr. Phillips asks the lab to post the orthotic to bring the heel to a 4 degrees inverted position.

For those rare conditions in which the patient fully supinates the subtalar joint in static stance and the heel is still everted, he asks the lab to post to bring the heel to a fully supinated position.

For most supinators, if they have a good everted forefoot deformity, Dr. Blake starts with a standard vertical heel pour and proceeds to consider high lateral heel cups, lateral phalanges and/or a Denton modification.

For extreme supinators (those with partial clubfoot, post-sprain lateral ankle instability or pes cavus with ligamentous laxity), Dr. Blake pours 5 degrees everted with the lateral Kirby skive. For these patients, he says this may be a starting point as one may have to try two to three orthoses to perfect the correction for their challenging foot.

For those with normal mechanics but pronatory symptoms (plantar fasciitis, medial shin splints, medial knee pain), Dr. Blake uses the standard vertical pour. This means the positive cast is designed with the heel vertical and the forefoot deformities are all supported so they do not make the heel inverted or everted.

For mild pronators (those with 2 to 4 degrees everted from vertical or 2 to 4 degrees everted from neutral in rearfoot varus cases), Dr. Blake recommends 3 degrees inverted pour or 15 degrees with his inverted orthotic technique.¹ For moderate pronators (those with 5-7 degrees everted from vertical or 5 to 7 degrees everted from neutral in rearfoot varus cases), he opts for 5 degrees inverted pour or 25 degrees with the inverted orthotic technique. For severe pronation (those with over 8 degrees of eversion from vertical or over 8 degrees from neutral in rearfoot varus cases), Dr. Blake recommends 7 degrees inverted pour or 35 degrees with the inverted orthotic technique.

When using heel inversion in the cast (3, 5, 7 degrees or so), if you also use a medial Kirby skive, Dr. Blake says you can typically lower the inversion by 2 degrees. This is the same for the inverted technique in which 25 degrees of inversion is typically equal to 15 degrees of inversion with the medial Kirby skive.

Dr. Blake does corrections with inverted or everted cast modifications and Kirby skives only. The rearfoot post is normally a zero motion flat addition to the orthotic plate that holds the correction for the orthotic device. If you use a rear post to correct 5 degrees, he notes you have to use a 5 degree forefoot post to keep that position.

Dr. Blake is in practice at the Center for Sports Medicine affiliated with St. Francis Memorial Hospital in San Francisco. He is a past president of the American Academy of Podiatric Sports Medicine.

Dr. Langer is in private practice at Twin Cities Orthopedics in Minneapolis. He is an Adjunct Clinical Professor at the University of Minnesota Medical School and a board member of the American Academy of Podiatric Sports Medicine.

Dr. Mitchell-Pray is a Fellow of the American Academy of Podiatric Sports Medicine and is board-certified by the American Board of Podiatric Medicine. She is in private practice in Sacramento, Calif.

Dr. Phillips is affiliated with the Orlando Veterans Affairs Medical Center in Orlando, Fla. He is a Diplomate of the American Board of Foot and Ankle Surgery, and the American Board of Podiatric Medicine. Dr. Phillips is a Professor of Podiatric Medicine with the College of Medicine at the University of Central Florida. He is also a member of the American Society of Biomechanics.

Reference
1.     Blake RL. Inverted functional orthosis. J Am Podiatr Med Assoc. 1986;76(5):275-276.