Functional Hallux Limitus

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What pathomechanical factors contribute to joint stiffness in hallux limitus? Have a 16 y/o lad presenting with FHL L>R, no dorsal exostosis. Leaving aside the foot mechanics, what actually makes the MTPJ lose its ROM? He has approx 35 degrees of movement in both joints yet recent x-rays show no degenerative changes whatsoever. Any ideas?

 

Hi Mark:
The most common causes of decreased ROM of the 1st MTPJ in an otherwise "normal" joint is a dorsally mobile first ray and / or a long 1st metatarsal. Both create the same problem, a situation where the base of the Prox phalanx cannot glide dorsally onto the metatarsal's articular surface when the foot is loaded (i.e. functional hallux limitus)
IF your patient DOES NOT have "normal" ROM in an open kinetic chain OR when the foot is loaded then I would look elsewhere.
If the joint space appears normal on Xray then perhaps an accult OCD, sesamoidal pathology, some soft tissue contraction, a hereditary flattening of the articular surface, etc....
good luck
DrSArbes

 

Thanks Steve. Might be worth doing an MRI to look at some of the other factors you mention, but we frequently see decreased ROM in patients with otherwise "normal" joints and classify it as hallux limitus. Often, mobilisation improves movement - pulling the hallux away from the metatarsal and maintaining position for 40-50 seconds - but the effects are usually transitory. With this particular lad, he sustained a fracture of the tibia 2 years ago which was treated with closed reduction and plaster immobilisation and developed compression syndromme, which may contribute to contracture of the flexor and extensor muscles, however he also displays decreased ROM in his "good" foot too. Is there any evidence that capsulitis contributes to decreased ROM?

 

Tension in the structures that limit first MTPJ dorsiflexion.

 

I can accept that where there are contributory biomechanical factors, Simon, but what gives rise to tension in these structures when the condition is primarily idiopathic?

 

Internal and external forces.

 

You're being unusually locaquious, Simon! Can you elaborate?

 

Have they read this article??

http://www.podiatrytoday.com/article/7486

What do they think??

Regards

 

Mark:

There are many factors that contribute to a true functional hallux limitus (where there is normal first metatarso-phalangeal joint (MPJ) dorsiflexion range of motion in non-weightbearing exam but inadequate first MPJ dorsiflexion in weightbearing exam/gait). Both Eric Fuller and I discussed the biomechanical etiological factors extensively in both didactic and workshop format this last weekend at the Biomechanics Summer School in the UK.

[Contrary to popular belief of many on this list, the term "functional hallux limitus" was first coined in 1972 by Pat Laird, DPM (Laird PO: Functional hallux limitus. The Illinois Podiatrist. 9:4, 1972).]

Here is a synopsis of the factors causing functional hallux limitus:

1. Medially deviated STJ axis causes first MPJ to be farther lateral to STJ axis than normal, increasing the magnitude of pronation moment from ground reaction force (GRF) acting plantar to first MPJ and plantar hallux.

2. Flatter than normal medial longitudinal arch height increases the relative magnitudes of tensile forces within the medial band of the central component of the plantar aponeurosis which, in turn, increases the magnitude of first MPJ plantarflexion moment, especially at late midstance. (This lower arch-increased tension effect was first described by John Hicks in his classic papers on the plantar fascia and windlass effect.) The tensile force within the plantar aponeurosis and other plantar intrinsics and flexor hallucis longus are the primary forces which prevent normal hallux dorsiflexion in functional hallux limitus.

3. Increased radius of curvature of distal first metatarsal head surface will increase the distance the base of the proximal phalanx of hallux will need to move in order to cause dorsal angular rotation of proximal phalanx about the medial-lateral first MPJ axis.

4. Elongated first metatarsal will cause a localized increase in tensile force within medial band of plantar aponeurosis and increased first MPJ plantarflexion moment during weigthbearing activities.

By the way, excessive STJ pronation moments cause functional hallux limitus. Functional hallux limitus does not necessarily cause pronation as is believed by sagittal plane facilitation theorists.

 

Thanks Kevin. My patient does not have a medially deviated STJ axis nor does he display a flatter than normal MLA, so I guess I'll have to look again at the x-rays to determine whether the head of the metatarsal is indeed curved as you suggest. I should add that he also has decreased non-weightbearing ROM - around 50 degrees - so perhaps I should not classify this as a true FHL....

 

Sorry, Mark. Go back now and look at #4 that I just added. Look for a long first metatarsal also.

 

Will do, thanks. Will try and upload the plates and photographs next week.

All the best.

 

HAHAHA!!!!
I Like the "internal or external forces"..................as opposed to what?
What other forces are there?
Perhaps quasiethereal?

DrSArbes

 

50 degrees of dorsiflexion of the hallux relative to the plantar aspect of the foot (plantar first MPJ to plantar calcaneus) suggests some contribution of a structural hallux limitus also. 70 degrees of hallux dorsiflexion during non-weightbearing examination is considered normal.

 

Kevin;

Thanks for the reference on Dr. Laird.

I would also note that, to my knowledge, Howard Dananberg, D.P.M.never claimed to coin the term functional hallux limitus.

He is most certainly the primary figure for popularizing the term over the past 2 decades.

cheers,

Bruce Williams, D.P.M.

 

I know that Howard has never made this claim, but others have. Howard really is the one that put functional hallux limitus "on the map", however.

 

Hi Mark,

See Fuller, E.A. The Windlass Mechanism Of The Foot: A Mechanical Model To Explain Pathology J Am Podiatr Med Assoc 2000 Jan; 90(1) p 35-46

High pronation moments on the foot will cause high tension in the plantar structures of the 1st MPJ. High pronation moments can be from the center of pressure being far lateral to the STJ axis. Or, in some feet, there is a high pronation moment from muscles. At BSS 2007 there was a subject in the audience who volunteered for my prescription writing for orthoses demonstration. She had a laterally deviated STJ axis and in static stance her peroneal muscles were visibly active. She also complained of 1st MPJ pain and hyperextension of her IPJ and if I recall correctly normal 1st mpj ROM non weight bearing. This person is what I would call a muscular pronatoer. the pronation moment comes from the muscle and not the ground. The highly active peroneal muscles will also tend to evert the foot far enough to cause a high load sub 1st MPJ. This will also increase tension in the structures plantar to the MPJ. It should also be remembered that the there is a force couple involved. When there is tension in the structrues plantar to the metatasal head that attach to the proximal phalanx there is also an equal in magnitude force from the first metatarsal head acting on the phalanx. (The net ant-post force must =0 because there is no acceleration of the phalanx.) This force couple is what prevents dorsiflexion of the MPJ. See the diagrams in paper referenced above.

Regards,

Eric Fuller

 

You appear to have missed the point of my rather fatitious reply. Mark asked:

The point being that Functional Hallux Limitus is not idiopathic, but rather a condition whose aetiology is biomechanical in origin. Hence my accurate, if rather brief, response.

 

That's what I thought too, however I couldn't find any mechanical pathology when I examined this patient, hence my enquiry here. It may well be structural HL if the curvature of the met head is as Kevin suggests, but I was simply wondering what makes the MTPJ so stiff when there are no obvious mechanical/structural impediments. I'll do an MRI and re-examine the x-rays and let you know.

 

Thanks Eric, that's really helpful. Don't suppose you have an electronic copy of the paper? My email address is russell.mark@btinternet.com

Many thanks

 

I think it is important to note that the tensile force within the plantar aponeurosis and other plantar intrinsics and flexor hallucis longus may be high even in a relatively high arched foot.

Also of significance here may be the work of Shereff (Shereff M.J et al. Kinematics of the first metatarsophalangeal joint. J Bone Joint Surg Am. 1986;68:392-398) who demonstrated that the instantaneous centre of rotation in 1st MTPJ's of subject's with hallux limitus lay outside the metatarsal head. Problems with cause and effect differentiation, but never the less in this situation movement of the joint about such axes will have a tendancy to "pull" the joint apart. Interesting then, the use of mobilization as a therapy... As an after thought I've just added this bit: the positions of axes shown by Shereff effectively increase the radius of the arc subtended by the hallux relative to the metatarsal- not too different from an increased radius of curvature of the met head in the sagittal plane.

To me, a far more interesting question is why do some people develop hallux limitus and some hallux valgus?

 

An even better question just came to me:

Why are you subjecting this 16 year old to all these rads when you have a diagnosis???????????????????????????????????????????????????????????? :How wil it change your management? mad:

 

Clearly I don't posess your superior diagnostic skills, Simon, and the oblique lateral plates I have don't tell me whether or not the met head curvature is a contributory factor with his condition.

 

Even though the tensile force within a high-arched foot may be "high" (whatever that means?), given the same amount of arch flattening moment in a low-arched and high-arched foot, the high-arched foot will always have lower magnitudes of plantar fascial tensile force than the low-arched foot, all other factors being equal.

In addition, plantar fascial tension in a low-arched foot and high-arched foot will produce very different mechanical effects related to the dorsiflexion stiffness of the first metatarsophalangeal joint (MPJ). The higher-arched foot will have decreased first MPJ dorsiflexion stiffness during the Hubscher maneuver since it has a greater moment arm for its plantar fascial tensile force to cause a first ray plantarflexion moment. The lower-arched foot will have increased first MPJ dorsiflexion stiffness during the Hubscher maneuver since it has a shorter moment arm for its plantar fascial tensile force to cause a first ray plantarflexion moment (all other factors being equal). Therefore, higher-arched feet rarely develop functional hallux limitus whereas lower-arched feet commonly develop functional hallux limitus.

In fact, very high-arched feet will, over time, develop a hallux hammertoe deformity as a result of the decrease in tensile force within the plantar fascia that results from their high-arched structure. The lack of adequate 1st MPJ plantarflexion moment from decreased plantar fascial tensile force in the very high-arched foot allows the flexor hallucis longus tendon tensile force to cause enough 1st MPJ dorsiflexion moment (via hallux IPJ plantarflexion) to allow gradual development of hallux hammertoe deformity.

 

Mark, that's an excellent question. I am assuming you are asking about non weightbearing ROM, as it seems that the thread has been answering the question of weightbearing ROM. I have been looking at this problem for a while, and this is what I have come up with.
First of all when you look at the x-ray, look for subchondral sclerosis of the base of the proximal phalanx. This is the first radiologic change I see. This is followed by asymmetrical joint space narrowing. These early changes are a result of the abnormal forces at the first MPJ indicative of FnHL.
The mechanism that causes the decreased off weight bearing ROM is when there is FnHL, there is a weight bearing restriction of movement of the first MPJ, the dorsiflexion force is still there and is now taken up by the sesmoidal ligaments (especially the proximal tibial sesmoidal ligament). Normally the ligaments act to guide the motion, but with the restriction of the joint, there is a distraction plantarly of the joint, and the ligament(s) stretch(es) with subsequent inflammation, scarring, and resultant contraction. This results in the decreased motion you see.
I have found by doing some soft tissue work on these ligaments, I can increase the motion by about 10-15 degrees in the first visit. It doesn't seem like much, but it is significant as far as pain is concerned.
The rubbing is distally over the tibial and fibular sesmoidal ligaments and overlying fascia, and medially over the plantar capsule and overlying fascia (or is it the inter-sesmoidal ligament and overlying fascia?). About 20 strokes is sufficient. Once in a while you have to rub in the opposite direction.
Remember that you have to use an orthosis that allows the first metatarsal to drop or the restriction will reoccur rather quickly. By this I mean the material has to be under the 2-5 metatarsal heads, not behind them.

Give it a try and let me know what you find.

Regards,

Stanley

 

How will knowing the curvature of the met head change your management of this case?

 

Agreed, but all other factors aren't always equal and just because someone doesn't have a marked pes planus, doesn't mean they can't develop functional hallux limitus. Ultimately it is the tensile force in the plantar fascial structures which creates the functional hallux limitus, not the arch height per se- this was my point.

 

Thanks Stanley, that was exactly what I was trying to find at the outset. He is having dorsoplantar and oblique medial views done next week, which should determine if the changes you suggest are established. Will let you know.

Simon, I wasn't sure whether this was FnHL or structural HL as the patient did not present with any of the aetiological factors I normally associate with either condition. His condition deteriorated immediately after the removal of his walking plaster following the tibial fracture 18 months ago and his referring general practitioner suspected some joint damage or flexor contracture and ordered an x-ray to determine if the former was a factor. Unfortunately the oblique lateral view was not particularly helpful and I have asked for the aforementioned views to be done to see if this is still a factor. Are you suggesting this is bad management? The prescription of the orthosis will probably differ depending on whether the HL is functional or structural. As I wasn't sure whether there were any other factors that might contribute to FnHL other than a medially deviated STJ axis and/or a mobile pes planus I thought some advice would be as helpful to determine an accurate Dx in the same way as clearer radiographs would assist in determining whether or not there was localised joint damage. Thanks for your advice and concerns.

 

Simon:

I agree with the above with the exception that 1) longitudinal arch height does seem to very strongly correlate to functional hallux limitus in most individuals, and 2) the plantar fascia is only one of the following plantar soft tissue structures that directly contributes to the posteriorly directed plantar first MPJ tensile forces which create functional hallux limitus:

A. Medial slip of central component of plantar aponeurosis
B. Abductor hallucis muscle
C. Flexor hallucis brevis muscle
D. Adductor hallucis muscle
E. Flexor hallucis longus muscle

I think a more accurate way of saying this is that plantar soft tissue tensile forces cause functional hallux limitus and that these are directly affected by many factors including medial longitudinal arch height. Would you agree, Simon?

 

Below are photographs of this patient which were taken during the initial consultation. Although they are non-weightbearing and do not demonstrate the MTPJ ROM, they do show the differing loads which the respective IPJs are subjected to, by way of callous formation. I shall upload the x-rays and additional photographs after I have him back for review. I should add the patient is a pole-vaulter (2-3 times/week) and his launch foot is his left.

 

May I suggest the following views? I like to use a Dorsal Plantar, Lateral, and a Lateral with the patient standing in a maximum push off position (maxiaml dorsiflexion of the 1st MPJ). The Dorsal Plantar shows subchondral sclerosis the best, as you can have a comparison to the lesser MPJ's; the lateral shows the position of the bones that make up the medial arch, and the maximal push off position lateral shows the full range available at the 1st MPJ. Remember this is not what is happening during gait, but rather the potential of the 1st MPJ.

Regards,

Stanley

 

From the photos my guess is he also has limited ankle dorsiflexion as well with limited internal rotation of the hips.

BTW: do you photograph all your patients?
Just wondering.

DrSArbes

 

Hello Steve:

No, ankle dorsiflexion is 15 degrees and internal hip rotation is fine. Nor does he display a positive Trendelenberg sign. Yes I keep a photographic record of all patients.

 

Mark:

Seeing the photos now of your 16 y/o patient's foot, along with the other clinical information you provided, makes me think he has a restriction of 1st MPJ dorsiflexion due to increased ligamentous tensile stiffness around the 1st MPJ. This would be considered to be a case of structural hallux limitus, not functional hallux limitus.

 

Hi Mark
I may have missed this, but what is your primary concern? Is it the fact there is a FHL, or is the concern the fact the left is worse than the right?
If it is the assymetry, then perhaps there is a slight contracture of FHL due to the previous fracture. This may be just enough to increase the tension around the MTPJ. Perhaps some soft tissue release massage?? Perhaps a trigger point??
As for the FHL on both... perhaps this person simply has a relatively short plantar fascia, or other structure as mentioned previously. I say relative as whether there is a high or low arch is not as important as the length, or tension in the structures aroound the joint. You would then be aiming to simply decrease this tension by whatever means you feel are appropriate for this person.
Cheers

 

Mark what you are saying is that you believe an x-ray is necessary to differentiate between functional and structural hallux limitus and you are still not sure so now you going to do an MRI?

Anybody else find this weird or is just me?

Strange you started this thread saying:

now those very same X-ray films are "not particularly helpful"?

Previously you'd said:

Which made me think you were going to perform an MRI scan on this patient in order to differentiate between a structural and functional hallux limitus when recent x-rays (note the plural) "show no degenerative changes whatsoever".

Then you said:

Kevin cited an increased met head curvature as a possible cause of functional hallux limitus. So I'm guessing you're still trying to work out if this is structural or functional? And now you'r going to shoot lateral x-ray films so you can measure the radius of the met head.

I'm suggesting that if someone needs needs multiple x-ray films and an MRI scan, or thinks that this technology is necessary to differentially diagnose functional hallux limitus from structural hallux limitus, then they should probably consider focusing their CPD on basic clinical assessment and diagnostic skills before attempting to manage patients with these conditions.

Here's a nice quote from Craig Paynes Lecture notes:
"The key ethical principle in deciding to order a x-ray is to only request an x-ray if the outcome of that x-ray has the potential to alter the treatment that the patient is to receive
If the management of the patient is expected to be unaffected by the outcome of the x-ray, then the need for the exposure to ionising radiation must be questioned"

Go on then Mark, tell me how all of this is going to change your orthoses prescription? And tell me why it's not possible to differentially diagnose functional hallux limitus from structural hallux limitus without multiple dosses of radiation?

 

Quite agree Simon. When I looked at the first X-rays there was no report of degenerative changes nor were any obvious, but as they were oblique lateral non-weightbearing views I wasn't really that happy that I was getting a clear picture. As there was no obvious biomechanical pathology my feeling was there had to be localised factors present and , as I wasn't aware of anything other than degereative changes within the joint or on the periarticular surfaces that might limit movement, I thought it prudent to take another view which might give a clearer indication what was happening within the 1st MTPJ.

To be honest, Simon, I asked this question on Arena as I wasn't sure if I had missed something in contributing mechanical or structural pathology. I had an idea what kind of orthoses I would try on this lad, but I really wanted to be clear in my mind what was causing the pathology in the first place, and of course, to seek advice on the prescription too. To be frank, not all of us are so adept in the field of foot and lower limb biomechanics as you obviously are, Simon, and although most practitioners on Arena are reasonably up-to-date with current thinking - thanks in no small part to people like yourself , Craig and Kevin and others - occasionally something comes along that challenges. On these occasions I think it reasonable to conduct whatever investigations I can and to seek advice from my peers.

With respect to the latter, Arena has become an invaluable source for many clinicians over the last few years and certainly I commend it to many colleagues at every opportunity. However, as you are aware there are many colleagues who do not contribute and one of the reasons I suspect that they don't is that they are unsure of their knowledge base and perhaps they fear ridicule or embarrasment. For the most part I enjoy reading your posts, Simon and very much appreciate the contributions you make, however there are times when your replies are rather fatuous and occasionaly disparaging. Although most of us will simply shrug our shoulders and think you're being a bit of a 2@ , it would be a real pity if such an approach inhibited others, perhaps a bit less experienced or confident, from contributing.

If I have rattled your cage with my enquiry then I do apologise, but perhaps you might care to bear in mind the impact your responses may have on the wider podiatry community in future?

Have a nice day.

 

Thanks Kevin. Much appreciated.

 

Thinking the same happy thoughts for you Mark.