How To Recreate The Benefits Of Low Dye Strapping With Orthotics
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.