Treating FHL: Why It's Essential For Orthotic Success
When it comes to understanding the effect of functional hallux limitus (Fhl) on foot function, Howard Dananberg, DPM, has published over 30 articles on the subject. “Early on, it was quite challenging to convince other DPMs of the relationship of the metatarsophalangeal joint’s mobility during walking to late midstance pronation,” notes Dr. Dananberg. “Since that time, many have gravitated to the significance Fhl has on the foot and postural alignment.”
With this in mind, our expert panelists offer their opinions on the significance of Fhl and how it has impacted their biomechanical practices.
Q: How has recognizing Fhl changed the way you prescribe orthotics?
A: Graham Curryer, BSc (Hons) DPodM, says initially, he prescribed orthoses based on pure “Rootian” principles, employing mainly rearfoot varus-type posts with various forefoot posts, usually varus and rarely valgus. At first, he based his prescriptions on measurements but as he became more experienced, he mainly based his work on clinical observation and “feel.”
Now he utilizes sagittal plane facilitation (SPF) principles almost exclusively. Curryer still takes an STJ-congruous cast as he feels practitioners need a “personal baseline reference point” from which to work. STJ molding possibly has occurred over time, requiring some rearfoot positioning.
However, Curryer says he no longer uses any “conventional” rearfoot posts, but instead opts for full-length orthoses, either Amfit devices or X-T Sprint devices (PARIS Orthotics, Vancouver, Canada). He usually prescribes two degrees forefoot valgus post with Fhl accommodation and he prefers using an extrinsic post, which is easier to modify. For clients with obvious MTJ instability and collapse, he will incorporate a 4-mm Kirby (medial) heel skive.
“If patients with Fhl have a tendency towards an unstable MTJ, they will automatically compensate here and collapse,” explains Curryer. In these cases, he notes patients’ forefeet remain on the ground and they seem to collapse their MTJs as their bodies pass over their feet.
“Over time, this process further weakens the MTJ and if they have significant lateral COP move into toe off, this places an extreme lever advantage perpendicular to the MTJ axis (making the situation even worse),” adds Curryer.
When First Ray Cutouts Can Help
In order to recognize Fhl, it is important to determine how much reducible forefoot supinatus exists in patients’ feet, according to Bruce Williams, DPM.
“I find that most of my patients have enough reducible supinatus in the first ray segment of their feet to allow the first metatarsal to, at a minimum, be in the same plane with the metatarsals two to five and usually be plantarflexed, or below the plane of the metatarsals two to five,” explains Dr. Williams. “This allowed me to recognize FHL and truly appreciate its significance.”
Dr. Williams previously tried to “cast out” the supinatus in his orthotics, but found a problem since many labs are reluctant to valgus post the forefoot beyond four degrees. He says this causes a real limitation in the first ray and puts too much pressure under the first ray, which prolongs the Fhl.
However, when Dr. Williams started using first ray cutouts, he found the first ray could plantarflex as much as necessary without the orthotic getting in the way. This allows the first MPJ and the hallux to dorsiflex. When this occurs, Dr. Williams says the windlass can operate as it needs to, which corrects most overpronation problems in the foot. Since employing first ray cutouts enables him to correct most biomechanical problems, Dr. Williams rarely uses rearfoot posting any more.