The case for the use of custom orthotics in the chiropractic practice is compelling.
Orthotics is research-proven to enhance the proprioceptive response of the foot and entire lower extremity, improving biomechanics.1
They also help with excessive pronation, which can lead to a host of problems—not just in the feet but throughout the kinetic chain.
Additionally, orthotics can be used to treat a number of ailments commonly seen in the chiropractic office, such as low-back pain, hip pain, and headaches, and are also effective in preventing injury.2-4
Casting call
But what is the best way to capture an image of your patient’s feet for the custom design of the orthotic? There are two major methods: weight-bearing and non-weight-bearing. These two procedures are incompatible because each produces different results.
Both techniques are used to make custom- fitted orthotics, yet they are mutually exclusive. All orthotics companies promote the method they support and some practitioners are quite vocal about which procedure they prefer.
There are a few inherent problems in getting a useful image of the foot and each system has its advantages and disadvantages. The limitations (and benefits) of each method should be understood before choosing a method.
Non-weight-bearing
Traditionally, a plaster cast is made of each foot in its non-weight-bearing, “subtalar neutral” position. The practitioner palpates the talus, then moves the foot until it is neither pronated nor supinated. By placing pressure on the lateral metatarsal heads, the forefoot is then “locked” and plaster strips are placed over the foot in this position.
Once dry, the “slipper cast” is removed and sent to an orthotics laboratory. Recently, most practitioners have abandoned the plaster cast method in favor of using digital foot scanners with the patient seated and the knee bent at a 90-degree angle, so that the foot barely rests on the device for a non-weight-bearing position scan.
The advantage of these procedures is that they capture an image of the foot in an ideal position—neither pronated nor supinated. But finding the non-weight-bearing subtalar neutral position is not an exact science and requires considerable training and practice.
Even experienced practitioners have only low to moderate agreement in finding the subtalar neutral position when non-weight-bearing.5 (Some of this discrepancy may be due to subluxations of the talus, which can change the subtalar neutral position.) According to Donald Baxter, MD, the past president of the American Orthopedic Foot and Ankle Society, “The ‘neutral’ or ‘corrected’ subtalar position is ill-defined and not physiologically reproducible. Furthermore, the subtalar joint ranges through nearly 40 degrees of motion during running and we can’t determine which of these 40 degrees is the ‘correct’ position for each athlete.”6
Furthermore, proper instructions for accurate posting must accompany the cast or scan. The doctor must determine if a post or wedge is needed under the medial or lateral side of the forefoot or rearfoot and, if so, how many degrees are needed. And after that, the laboratory has to perform its own magic, called “cast expansion.”
Since no one can walk on an orthotic made purely from a non-weight- bearing image of their foot, certain areas must be augmented. Extensions are added to enlarge the orthotic for the widening and lengthening that occurs when each foot bears the entire weight of the body during gait.
Admittedly, this method doesn’t address the alignment of the structures above the foot that could be affecting foot alignment significantly. As there are so many areas where errors can creep in, it’s not surprising that many patients have substantial difficulties wearing this type of orthotic. Often, several follow-up visits for modification and fine-tuning are needed with this system, even when performed by an experienced doctor.
Weight-bearing
A different method is to have the patient step into a box containing compressible foam or, alternatively, stepping onto a foot scanner to capture the image. The patient places a foot in the box or scanning window in the same position as during gait. In a balanced stance, weight is borne evenly through both feet. A three-dimensional image of each foot is obtained while in this position.
This method provides an image of the foot when it is bearing weight during the stance phase of gait and supporting the pelvis and spine. The image obtained demonstrates the full amount of pronation and arch collapse, as well as the effects of biomechanical problems above. Several studies have found that measurements of foot posture in the weight-bearing position are more reliable and clinically useful.7,8
In his landmark text, Essentials of Skeletal Radiology, Terry Yochum, DC, says, “To prescribe the most effective [orthotic] support, use of a weight- bearing casting method to obtain quantifiable information on the extent of pedal imbalance is recommended. This method also results in a more accurate fit, since the true length and width of the foot during the closed- chain stance are thoroughly assessed.”9
One drawback to this approach is the tendency for patients to move while standing, which can produce a blurred image of the foot. You must be sure that the patient is standing normally.
The orthotic laboratory then makes multiple measurements of each foot image and determines a corrective prescription. If no biomechanical corrections are indicated, the orthotic is simply accommodative and will provide only palliative relief.
The procedures and quality control of the orthotic company are essential to a good outcome, which may explain variation in the experiences of doctors who have tried the weight-bearing method.
Net effects
Non-weight-bearing. Once the image of the foot in a nearly subtalar neutral position has been corrected with proper posting and the necessary enlargements have been added, an orthotic is made to keep the foot close to that ideal position. Because the weight and forces on the foot are high during walking (and even higher during running), the traditional result is a fairly rigid orthotic. This can be uncomfortable for many people and especially difficult to wear during sports.
A rigid orthotic may also interfere with the function of the large joint at the base of the first toe, causing a functional hallux limitus.10 Currently, most doctors using the non-weight- bearing system opt for flexible or semi- rigid materials and many add a special, flexible cutout at the first metatarsal joint. Unfortunately, the end result is substantially less support for the foot, and only partial correction of subtalar neutral.
Weight-bearing. Following the corrective prescription formulated from the standing image of the foot, an orthotic is fabricated containing supports for each of the three arches. This normalizes the pedal structural alignment and provides balanced support for the structures above.11
If needed, a separate pronation (varus) wedge is placed under the medial aspect of the calcaneus. As motion control comes from the pronation wedge and arch supports, the orthotic can be quite flexible and include shock-absorbing materials. A separate cutout is not needed to encourage first metatarsal mobility because the orthotic in front of the medial arch support is already flexible.
The resulting orthotics are easier for most patients to tolerate and they require fewer modifications. Studies have shown that soft materials are effective and athletes in particular appreciate more flexible orthotics.12-15 A disadvantage of orthotics made from a weight-bearing foot image is that a small percentage of patients are unable to tolerate the full amount of correction. In such cases, a decrease modification is necessary.
Weighing the results
Both systems for capturing an image of the foot have pros and cons. The orthotics that can be made from each method of foot imaging are also quite different. Understand the advantages and disadvantages of each. With either method, you’ll want to develop a good, trusting relationship with the laboratory that fabricates the orthotics.
Both systems capture a static image of the foot but the laboratories must make assumptions and determine treatment strategies. Therefore, the accuracy of the image is vitally important in both methods.
Most chiropractors appreciate the whole-body imaging that the weight- bearing procedure provides, and most patients like the more flexible and comfortable orthotics that result.
Athletes, in particular, value the shock absorption and easy tolerance of orthotics made from a weight-bearing image.
John K. Hyland, DC, DACBO, DACBR, is a 1980 graduate of Logan College of Chiropractic, and practiced for more than 20 years in Colorado. He is an expert in rehabilitation, and developed four chiropractic rehabilitation practices. Today he consults, advises, and trains chiropractors in the concepts and procedures of spinal rehabilitation. He can be contacted at 303- 819-9159 or drhyland@comcast.net.
References
1 Stude DE, et al. Effects of orthotic intervention and nine holes of simulated golf on club-head velocity in experienced golfers. J Manip Physiol Ther. 2000;23:168-174.
2 Rosner A, et al. Influence of Foot Orthotics Upon Duration of Effects of Spinal Manipulation in Chronic Back Pain Patients: A Randomized Clinical Trial. J Manip Physiol Ther. 2014;37:124-140.
3 Ferrari R. Effect of Customized Foot Orthotics in Addition to Usual Care for the Management of Chronic Low Back Pain Following Work- Related Low Back Injury. J Manip Physiol Ther. 2013;36:359-363.
4 Jensen B, Austin W, Wilder NJ, et al. Effectiveness of custom orthotics at reducing injuries in a college football team. J Chiropr Educ. 2007;21(1):109.
5 Smith-Oricchio K, Harris BA. Interrater reliability of subtalar neutral, calcaneal inversion and eversion. J Orthop Sports Phys Ther.1990;12:10-15.6 Baxter DE, et al. The ideal running orthosis: a philosophy of design. Biomechanics.1996;3(3):42.
7 Lattanza L, Gray GW, Kantner RM. Closed versus open chain measurements of subtalar joint eversion: implications for clinical practice. J Orthop Sports Phys Ther. 1988;9:310-314.
8 Picciano AM, Rowlands MS, Worrell T. Reliability of open and closed kinetic chain subtalar joint neutral positions. J Orthop Sports Phys Ther. 1993;18:553-555.
9 Yochum TR, Rowe LJ, Barry MS. (1996). Natural history of spondylolysis and spondylolisthesis. Essentials of Skeletal Radiology. (2nd ed., p. 364). Baltimore: Williams & Wilkins.
10 Dananberg HJ, Giuliani M. Chronic low-back pain and its response to custom-made foot orthoses. J Am Podiatr Med Assoc.1999;89:109-117.
11 Kuhn DR, Shibley NJ, Austin WM, Yochum TR. Radiographic evaluation of weight-bearing orthotics and their effect on flexible pes planus. J Manip Physiol Therap. 1999;22:221-226.
12 McPoil TG, Cornwall MW. Rigid versus soft foot orthoses. J Am Podiatr Med Assoc.1991;81:638-642.
13 Gross ML Davlin LB, Evanski PM. Effectiveness of orthotic shoe inserts in the long-distance runner. Am J Sports Med.1991;19:409-412.
14 Smith LS, et al. The effects of soft and semi-rigid orthoses upon rearfoot movement in running. J Am Podiatr Med Assoc. 1986;76:227-233.
15 Weik DA, Martin WJ. Use of soft heat-molded orthoses in sports. J Am Podiatr Med Assoc. 1993;83:529-533.
