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