Most competitive runners do not like being restricted in their regimens. As we all know, these patients are very anxious to resume their running activity. However, they do look to foot and ankle specialists for help in reducing the inflammation, preventing and/or recuperating from lower extremity injuries. In order to write effective orthotic prescriptions for these patients, be sure to pay attention to cast correction, materials and additional bells and whistles.
The ability of the orthosis to control abnormal or excessive motion of the foot is more dependent on the size of the device and the cast correction techniques. Cast correction can be broken down into heel cup depth, orthotic width, positive cast arch fill, medial skive, lateral skive, inversion and plantar fascial groove, all of which are important components to orthotic prescription writing for the athletic runner.
The heel cup depth should be at least 14 mm in depth. The orthotic device width is recommended to be at least extra wide in depth. A deeper heel cup and a wider device provide more surface area for the orthotic to control the foot. The deeper you make the heel cup and the wider you make the device, it allows you to utilize the skive technique as well as the inverted technique to give a maximum benefit to the runner. If the athlete is wearing a sprinter’s shoe, which is cut narrower and shallower to the runner’s foot, you would have to modify the prescription.
The amount of arch fill in the positive cast work allows for better contour to the athlete’s foot and control of the biomechanical pathologies. While a minimal arch fill will allow the orthotics to closely hug the medial plantar arch of the foot and enable you to provide maximum control of the hyperpronated foot type, be aware that it will also push the foot higher onto the vamp of the shoe and increase the rigidity of the orthotic material.
It is recommended that you use a standard to maximum arch fill, depending on the pathology and runner’s foot type. The runner with an everted rearfoot and a pes planovalgus foot type in stance will benefit from an orthotic with standard arch fill, whereas an athlete with an inverted rearfoot and a pes cavus foot type will benefit from an orthotic with maximum arch fill.
What You Should Know About Intrinsic Cast Correction Techniques
Using the medial skive technique allows you to incorporate a varus wedge affect into the medial aspect of the orthotic’s heel cup. The increments of control with the medial skive range from 2 mm to 6 mm. An increase in the increments of the skive causes the heel cup tend to narrow. Therefore, when you’re treating an adult athlete, using a 6 mm skive is rarely recommended. The medial skive technique is recommended for the runner with a hyperpronated foot type.
If the runner presents with a calcaneal stance position of 2 to 4 degrees of eversion, I recommend using a 2 mm skive. If the runner presents with a calcaneal stance position of 4 to 6 degrees of eversion, use a 4 mm skive. If the calcaneal stance position is higher than 6 degrees everted, you should use an inverted and skive technique in combination.
Conversely, when you employ the lateral skive intrinsic cast correction technique, you’re able to incorporate a valgus wedge effect into the lateral aspect of the orthotic’s heel cup. The same increments are used for the lateral as the medial skive technique. The indications for using the lateral skive are for athletes with lateral ankle instability and peroneal tendonitis, as well as any pathology which increases lateral column loading.
Inversion is another intrinsic correction technique which incorporates a varus wedge along the medial column of the foot. The number of degrees recommended with the inversion technique varies. Reviewing the literature, it was initially recommended to invert the cast from 10 to 45 degrees, depending on the runner’s severity of calcaneal eversion.
Multiple formulas in the literature can help you determine the amount of inversion to prescribe for the hyperpronated foot type. The competitive runner who needs subtalar joint control benefits with minimal inversion (anywhere from 5 to 10 degrees) and combination of a medial skive for maximum control. Remember that the higher the inversion, the higher the curve is in the medial arch and the more rigid that orthotic material becomes. The increased height of the orthotic also raises the foot, which has the tendency to rub against the vamp of the shoe.
The plantar fascial groove is an intrinsic accommodation you can make in the orthotic shell to off-weightbear a prominent plantar fascial band. Be aware that this accommodation will increase the rigidity of the orthotic device. For the runner who truly has a tight plantar fascial band, it is recommended to downgrade to a more flexible device.
Expert Advice On Selecting Materials
When it comes to orthotic materials, you can choose from functional, accommodative and combination materials. This is the least important aspect of prescription writing. Your negative cast, the prescription and the positive castwork, performed by the lab, all have a greater effect on clinical outcome than your choice of material.
However, when you’re treating competitive or amateur runners, it is necessary to keep in mind the weight of the device. A heavy functional foot orthoses in their shoes can slow them down, decrease their miles or add seconds to their miles. Keeping the orthotic material as lightweight and flexible as possible while providing control at the same time seems to be the key in correct prescription writing.
Many foot and ankle specialists agree polypropylene and graphite are the two favorite functional materials to use with athletes. Polypropylene is available in varying thickness. The most common notation for the thickness is 1/8, 5/32, 3/16 and 1/4 of an inch. One of the great advantages to using the polypropylene material is its ability to conform to curves of the foot very tightly. Another advantage to this material is the ability to incorporate intrinsic accommodation in the orthotic shell itself.
The thickness of the polypropylene is directly related to the runner’s weight. For example, you would usually prescribe a 3/16 of a polypropylene device (a semi-rigid device) for a male patient who weights 175 lbs. However, when prescribing a polypropylene device for a runner, it is recommended to downgrade to a more flexible thickness. When prescribing for a 175-lb. man who is a competitive athlete, you should opt for a 5/32 polypropylene device, which will be a flexible orthotic. The orthotic device is not only a bit more flexible now but it is also lighter.
The advantage of graphite is its light weight. Graphite’s rigidity is influenced by the patient’s weight. Therefore, for the runner, you sacrifice on the arch fill or degree of control to prevent an increase in rigidity of the graphite. A disadvantage of the graphite is its inability to incorporate intrinsic accommodation in the form of plantar fascial grooves or sweet spots in the shell. Graphite is also more prone to break than is polypropylene.
Two of the favorite accommodative materials for runners in recent years have been EVA and Plastazote. Both materials are available in varying degrees of firmness. A medium or firm durameter of EVA is usually recommended for the runner. Again, the durameter of the material is related to the patient’s weight. Plastazote is also available in varying firmness. The black Plastazote is recommended for the shell of the device. The disadvantage for both forms of accommodative materials is poor longevity, anywhere from six to 12 months, depending on the athlete’s miles per week and weight. The advantages appear to be in the reduced weight of the materials.
Most orthotic labs have the “sport” orthotic. This is usually a combination material orthotic in the form of a thin shell of polypropylene reinforced in the medial arch with EVA or a similar foam. This type of orthosis allows for increased shock absorption and is beneficial for the athlete who mostly runs on concrete. A disadvantage of this orthotic is it has a tendency to be prescribed too rigidly. Remember, if you prescribe a sports device, consider downgrading the thickness of the polypropylene shell to 1/8 inch and using a medium density of EVA arch fill.
What About Rearfoot Posts, Topcovers and Extensions?
There are extra bells and whistles you can add to make the orthotic more effective in controlling the runner’s symptoms and pathology. The most pertinent additions are rearfoot posts, topcovers and extensions.
Most foot and ankle specialists recognize the need and efficacy of the rearfoot post. Rearfoot posts stabilize the orthotic in the shoe. Runners require a 4/4 rearfoot post on their orthotics. The exceptions are runners with subtalar joint or ankle joint arthritis or coalition. These runners benefit from a 0/0 rearfoot post.
The most important aspect of prescription writing, with respect to the rearfoot post, is the material you use. EVA and birko cork are the materials of choice as they both allow for shock absorption to occur during heel strike. You should avoid the polypropylene or acrylic posts due to their lack of shock absorbing properties.
Another great benefit to the rearfoot post is the ability to unbevel either the medial or lateral aspect of the post. The unbeveled medial aspect of the rearfoot post adds more supinatory control over the pes planovalglus foot type. The unbeveled lateral aspect of the rearfoot post provides lateral stability for the pes cavus foot type. Both of these modifications are very subtle in the orthotic and in the runner’s shoe, but they do increase the runner’s compliance in using the prescribed orthotic.
You should consider using a topcover material with the most shock absorbing property, cushioning and longevity. EVA comes in 1/8 or 1/16 in thickness as well as firm or soft durameter. EVA is often recommended for its shock absorption properties whereas Spenco 1/8 or 1/16 is usually recommended for its cushioning properties.
Keep in mind that any extra additions will take up room in the toe box of the shoe. The extensions and additions will also have a tendency to increase the weight of the orthotic device itself. Therefore, you should try to incorporate most of the accommodations and control intrinsically.
Sports medicine is an integral part of most podiatric practices. Both competitive athletes as well as amateur runners can provide treatment challenges. It’s important not only to correctly diagnose the injury, but be mindful of the patient’s activity, lifestyle and goals. Doing so will enable you to incorporate appropriate conservative treatment modalities into your patient’s running routine.
Dr. Kashanian is a Diplomate of the American Board of Primary Medicine and Podiatric Orthopedics, and is a consultant for ProLab Educational Institute. She is in private practice in Northridge, Calif.