How many of us have put on a low Dye strapping that successfully alleviated the patient’s symptoms only to prescribe foot orthotic devices that did not have the same outcome? I would think anyone who has been in practice long enough has done this. What happened between the low Dye strapping and the foot orthotic device that changed the outcome we anticipated?
One can use the low Dye as a treatment modality in and of itself or as a means of assessing whether or not a patient would benefit from a pair of foot orthotic devices. There are many variations of this strapping and many of us have small things we do that make the strapping more effective. The main effect of a low Dye strapping is exerting force that places a plantarflexion moment on the first ray, helping to maintain the first ray in plantarflexion and augmenting the height of the medial longitudinal arch. Many of us will also attempt to pronate the midtarsal joint maximally and place the subtalar joint in a neutral position.
All of these components individually or together will have an indirect influence over the subtalar joint and a direct influence at the midtarsal joint as the foot function. However, it is my opinion that plantarflexing the first ray with the strapping is the most important component and most influential factor in the strapping’s success.
First Ray Function: What You Should Know
In addressing first ray function, the literature has discussed the involved mechanics a great deal. The most common understanding of first ray function is that the first ray undergoes dorsiflexion and plantarflexion. With dorsiflexion, we should also see inversion and with plantarflexion, we should see eversion. These concurrent motions allow the first metatarsal head to stay even with the ground when it is plantarflexing or dorsiflexing during gait, maintaining even pressure on both sesamoids.
When it comes to gait, the common thought is that during the latter half of the midstance period, we should see the first ray begin to plantarflex relative to the osseous structures proximal to it and continue to plantarflex during the propulsive period. This continued plantarflexion of the first ray is what positions the hallux evenly across the ground in the sagittal plane and allows us to dorsiflex the hallux on the first metatarsal head for efficient propulsion.
Patients who cannot achieve sufficient plantarflexion of the first ray in the propulsive period will typically develop hallux limitus. The inability to plantarflex the first ray sufficiently during the propulsive period places the hallux in an equinus attitude relative to the first metatarsal head. This leads to jamming dorsally of the proximal phalanx of the hallux into the first metatarsal head and subsequent soft tissue adaptation at the joint, promoting hallux limitus.
Ultimately, there is osseous adaptation at the joint with dorsal exostosis formation or a “flag sign” at the first metatarsal head. There will also be potential jamming all along the medial column and osteophyte formation at the base of the first ray, the navicular medial cuneiform articulation and the talonavicular articulation. This is where the low Dye strapping is effective when one applies it properly. By placing plantarflexion force on the first ray, the low Dye strapping can mitigate abnormal first ray dorsiflexion during gait.
Key Insights On Creating An Effective Orthotic
When applying the principles of first ray function to our functional foot orthotic device, it becomes clear we must create a device that facilitates adequate plantarflexion of the first ray. How do we accomplish this? Much depends on the patient’s foot structure. The patient with a forefoot varus will most likely have an intrinsic forefoot post incorporated into his or her foot orthotic device. Intrinsic forefoot varus posts promote a plantarflexion of the medial column of the foot. In essence, these varus posts attempt to force the medial aspect of the foot to the ground.
One would attempt the same posting approach in a patient with a forefoot valgus but with the lateral column. Since the lateral column is more stable in most cases and less likely to be forced to the ground, an extrinsic forefoot valgus post is perhaps a better option.
None of these options directly addresses the first ray.
Many foot orthotic laboratories promote a modification of the negative casting technique to address the first ray directly. This modification involves dorsiflexing the hallux during the process of obtaining the negative cast. By dorsiflexing the hallux, we apply a retrograde force on the first ray that results in plantarflexion of the first ray.
The result is a negative foot impression cast with the subtalar joint in a neutral position, a maximally pronated midtarsal joint and a plantarflexed first ray. In essence, one is obtaining an impression of the foot that is ideally prepared for entry into the propulsive period of the gait cycle. When fabricated properly, the resulting foot orthotic device will promote first ray plantarflexion. Now the orthotic does what the low Dye strapping does, only better.
How do we know if this will be enough? Is this right for all patients? The answers to these questions are dependent on the exam. It is important to examine the position and motion of the first ray carefully. Recent literature reveals that the findings of the range of motion exam of the first ray are not predictive as to first ray hypermobility and are not readily reproducible. However, we can still use the results of the exam to get an idea of the position and motion of the first ray, and translate this info into the design of an orthotic.
Case Study: A Marathon Runner With A Small Area Of Dorsal Pain
A 24-year-old male marathon runner presents with a chief complaint of pain on the dorsal aspect of his left foot in an area about the size of a quarter. The patient relates that he ran his last marathon three months prior to his visit and the pain became quite intense. He was diagnosed with posterior tibialis tendonitis. The patient also relates he was recently diagnosed with a bone spur. The patient has tried NSAIDs, ice and rest with no resolution of his symptoms. He has no other contributory medical conditions.
The patient has pain with palpation to the area over the talonavicular joint. He also appears to have a cavus foot. Subtalar joint, midtarsal joint and first metatarsophalangeal joint ranges of motion are all normal. The non-weightbearing examination reveals a positionally plantarflexed first ray. The patient also has a varus of metatarsal heads two through five. Radiographs show signs of a cavus foot with a dorsal exostosis at the talonavicular joint of the symptomatic left foot. I applied a low Dye strapping and instructed the patient to attempt a run.
The patient reported that he ran with the taping and his pain was completely alleviated. Based on the radiographic evidence of medial column jamming and evidence that the patient’s first ray was the cause of this jamming (due to his response to the low Dye strapping), I decided to cast the patient for foot orthotic devices.
Capturing The Benefits Of Low Dye Strapping With Orthotics
How would one recreate the positive results the low Dye strapping provided? Based on our clinical exam, we fabricated a foot orthotic device that incorporated a rearfoot post that corresponded to the patient’s neutral calcaneal stance position.
The forefoot was a different matter. We applied an intrinsic forefoot post for metatarsal heads two through five. There was also a cutout within the shell of the foot orthotic device for the first ray. This allowed for more plantarflexion of the first ray relative to the lesser rays. After a break-in period for the foot orthotic devices, we cleared the patient to run in them. In short, using the orthotics alleviated the patient’s symptoms.
This patient required something beyond just capturing his first ray plantarflexed in a negative cast. By closely examining this runner’s foot and with the help of the low Dye strapping, we prescribed a foot orthotic device that eliminated the jamming of his medial column by allowing his first ray to plantarflex adequately.
There are other means of further promoting first ray plantarflexion in an orthotic. One may employ a cutout beneath the first ray in a forefoot extension, a kinetic wedge under the first metatarsal head, a reverse Morton’s extension or a cutout in the shell of the orthotic itself.
The important thing is to listen to what an athletic patient says about wearing a low Dye strapping. Couple that with a careful and thorough clinical exam and the odds are good of creating a foot orthotic device that will provide maximum patient benefit by promoting adequate first ray plantarflexion.
Dr. Spencer is an Associate Professor of Orthopedics/Biomechanics at the Ohio College of Podiatric Medicine. He is also a Diplomate of the American Board of Orthopedics and Primary Podiatric Medicine.
Dr. Caselli (shown in the photo) is a staff podiatrist at the VA Hudson Valley Health Care System in Montrose, N.Y. He is also an Adjunct Professor at the New York College of Podiatric Medicine and a Fellow of the American College of Sports Medicine.
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