Peroneal weakness & Lunge test

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Hi,

Another case of peculiar clinical signs which I can't knit together. Help & advice much appreciated.

Young boy in my clinic today. Age 13. Pain Dorsal/lateral (and very occasionally lateral plantar) Left foot. Several months duration. He plays no regular sport (he played school soccer until last year but nothing else since). He is quite skinny with little leg muscle bulk. He wears skate shoes in & out of school, which are wide, loosely laced & no sole stiffness whatsoever.

Tenderness palpable base 5th metatarsal & along a line about 1 1/2 inches dorsal to this point. No swelling or erythema. No tenderness in Sinus Tarsi. Muscle testing indicates weakness of Peroneus Tertius. Passive ankle dorsiflexion (seated, knee flexed) shows more dorsiflexion range on the left ankle than right. No discomfort felt in dorsiflexion, but becomes sore when taken to plantiflexion end of range. Subtalar & Midtarsal joints quite mobile bilaterally.

RCSP low arch height, prominent navicular bulge bilaterally. I got him to doo a toe raise & he found this sore (lateral/dorsum) on his left foot. During gait the right foot abducts, but the left foot stays pretty straight throughout. He started to limp a little after a couple of minutes of walking up & down. Slight adductory twist of both rearfoot on heel lift. He pronates early & stays that way throughout.

Now. I did a lunge test before he started walking for me. I was expecting the results to mirror the passive range (i.e. more ankle dorsiflexion on the left side than right). However he achieved 40 degrees on his right side & only 29 degrees on his left (however hard I got him to push).

There was no significant forefoot equinus, so where did the dorsiflexion range go?

I've sent him for an U/S & issued him with a lateral 3/4 wedge. Seeing him next week.

Confused Julian. :wacko:

 

Julian a quick response

When you did the dorsiflexion stiffness testing at the ankle what position was the STJ in compared to weightbeaing ?

why did he start limping - pain ? where was the pain ? (lateral/dorsum) on his left foot is another spot ? can you be a bit more specific with location?

Also did lateral wedge help or make the pain worse ?maybe a follow up call a day or so later to answer ???

I´ve an idea just need some more information

 

Hi Mike.

I love looking back at some of my posts & doing a Doh! for the bits I've missed.

I should point out that eccentric & concentic muscle testing of peroneus tertius (and I'm pretty certain that's what I was testing) caused pain in the lateral/dorsal area. It was weak (compared to the right foot) & it hurt when used. His pain was always in the same region, Base 5th met/cuboid area. Sorry for muddying the position by switching between dorsal/lateral as opposed to lateral/dorsum.

Dorsiflexion at ankle in an approximation of STJ neutral when sitting, I do that out of habit more than anything else.

Slight limping left foot. Lateral/dorsal aspect of left foot became sore. Same area that felt sore all the way through. I could not elicit any lateral plantar soreness throughout, but he played that down after mentioning it at the outset.

No history of lateral inversion sprains. No feeling of lateral ankle weakness. Tinels sign negative to sural nerve. No tenderness in Sinus Tarsi.

I considered ligament injury, but in the absence of an injurous event it seemed unlikely. I guess the U/S will throw up anything if I've just missed it.

I'm not calling him over the weekend. Work/life balance switch engaged. I could follow-up next week if it seemed essential. He walked around with the wedge for a few minutes in his sloppy shoes & it didn't make any difference either way. I'd be hoping we get an effect in some snugger fitting, firmer-soled footwear.

Intrigued to know what your idea is though...

 

Julian

Just more questions or 1 more - what anatomical structure is the pain over ?

 

Well, the Peroneus Tertius tendon. Distal to where it pops out from under the extensor retinaculum along to the insertion on the 5th met.

At least that's what I considered it to be. What are you thinking? And how is this linked to the reduced dorsiflexion?

 

Right where were we,

if we have a pronated foot type or medial deviated axis the Peroneus Tertius is a pronator of the Subtalar joint.

At all times forces acting across the Subtalar joint need to be equal and opposite but where the forces coming from are of various make up.

So if we have a Peroneus Tertius muscle is spasm much of the internal pronation moment will be ( maybe really but for the discussion) coming from this muscle, but the forces acting as STJ supinator will be changing their make-up if these become osseous or GRF then is unlikely the Peroneus Tertius will have any effect but to strain itself if in spasm or over working.

When you did the dorsiflexion ROM testing of the Talocural joint it was in `neutral´when you did the lung testing the foot was in a more pronated position - we have a kinematic change at the subtalar joint, ie the talus has moved relative to the calcaneous, the talus has of course moved relative to the Tibia. If the change is enough the talus will come in contact with the distal aspect of the tibia during dorsiflexion of the ankle.

Does that make sense or even help ?

 

I like what you did there. That was quite excellent! Makes perfect sense.

So, chances are then that my lateral wedge will likely increase rather than decrease pain since I'm now further increasing the pronation moment.

Might need to make a phone call on Monday!

Cheers.

 

Maybe maybe not be good to hear what the result is - remember I´m just giving ideas via the Internet

 

I'm going to pick a few nits.

The most common attachment of peroneus tertius is the 5th metatarsal. (The muscle is sometimes absent) Its origin is the lateral leg, its attachment is the lateral foot, so it will be on the lateral side of the STJ axis even in laterally positioned STJ axes.

You left out, "when there is no acceleration." Net force = mass x acceleration. Net moment = moment of inertia x angular acceleration. So, when the acceleration is zero the net moment at a joint is zero. When the joint accelerates the net moment is not zero. Newton's 2nd law

Newton's third law. On the other hand when you apply a force couple to an object, there will be an equal and opposite force couple applied to you. A good example is the ankle joint. At the foot there is an upward force from the Achilles tendon applied to the calcaneus and there is a downward force applied by the tibia to talus. This creates a plantar flexion moment to the foot. The equal and opposite reactions to those forces, an upward force from the talus on the bottom of the tibia, and a downward pull on the Achilles tendon from the calcaneus will cause a force couple that will tend to rotate the top of the tibia backwards.

Eric

 

Thanks Eric always learning :drinks