Saddle syndrome

[Linh]

Hi Steve,
Any ideas to scan for ? saddle syndrome for an index finger. Pt is a percussionist. I cant find much literature on the subject.
Thanks you!
Linh

[Stephen Bird]

Nup,

I have never heard of it !

Certainly never been asked to scan it or look for it.

I found a journal article published in the journal of hand surgery before you were born in 1986 with review of over 80 cases.

Here is the URL:

https://www.sciencedirect.com/science/article/abs/pii/S0363502386800533

It states:

Trauma to the hand can result in adhesions between the interosseous and lumbrical muscles with subsequent painful impingement on the deep transverse metacarpal ligament during intrinsic contraction. If these adhesions also develop between the intrinsic muscles and the deep transverse metacarpal ligaments or metacarpophalangeal capsule, discomfort may be produced by stretching of the intrinsic tendons. Release of these adhesions, partial resection of the ligament, and early mobilization can produce relief of the symptoms.

So we can certainly see the interosseous muscles easily and also the lubmricals.
The direction of movement of these muscles is about 90 degrees to each other in my mind.
So can we look at the lumbricals during flexion and extension of the MCP joints watching if the slide easily over the interosseous muscles they are sitting on or if they get stuck due to adhesions.

I think if you scan in the palm of the hand in the long axis of the lumbricals this is worth a try.

The impingement on the deep transverse metacarpal ligament sounds above my pay grade !

Have a crack and see how it goes.

I am home now, but tomorrow I will have a play myself and see how much actual glide there is of these muscles over each other. I am thinking it is going to be minimal even in a normal volunteer.

Steve

[Linh]

Hahaha, thanks Steve, you’re so quick. While you are on research mode, any ideas to scan for Linberg – Comestock anastomosis? My radiologist even found it hard on MR, let alone seeing the abnormal vonnection on US. It’s very obvious clinically but proving it on imaging is tricky.

yes, I’m 27, not 37 yet, still learning from you haha

[Linh]

MR key images:

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[Stephen Bird]

I didn’t mean you were born in 1986,

That was the year the article was published and I was taking a punt you were probably not born yet !

Steve.

[Stephen Bird]

I can almost believe the connection on the axial MRI, but the sagittal is an eye of faith for me.

When asked to tackle these I simply go through the volar forearm anatomy looking for any variations.

It is surprising how many variations you observe in the general population and the variation you have bought up for discussion is not that rare, but usually not symptomatic.

I agree the clinical test is easy. If you hold the fingers in extension and the patient can not fully flex the thumb they have it.

I think it is cool that it is all anterior interosseous nerve territory. That nerve only has 3 jobs and 2 of them pertain to the muscles that get connected (FPL and FDP index), the other muscle it supplies id pronator quadratis.

We all know how easy it is to follow FLB from the thenar eminence where any idiot can see it, through the carpal tunnel where it is always the most radially placed tendon, into the forearm where it becomes muscular and the muscle is always immediately anterior to the radius so easy to identify and follow.

FDP index is easy to pick up in the carpal tunnel by flexing the DIP jt of index only and you will see it move.

Follow it proximally watching its relationship with FPL and look for any collagen bridge between them or muscle variation. They sit next to each other anatomically.

You can also repeat the clinical test as I described and look for movement of FPD index as PFL tries to tug on it at the anastomosis site.

This is where we have a real advantage over MRI.

The connections are usually in the distal forearm / proximal carpal tunnel area as distal to this they diverge. If the connection is more proximal it is usually a whole extra muscle slip or extra tendon where the anatomy has a wholesale variation rather than just a small collagen bridge.

I owe my botulinum toxin work with spasticity management for my love of solar forearm and hand muscle anatomy.

Steve

[Linh]

Haha no worries, I was just joking around!

Thank Steve. Good tip, I did try and look for the connection but with a close approximation of echogenic tendons and echogenic fascial planes, it’s really hard not to MSU anpther thin echogenic band. US is better at the dynamic aspect and spatial res, but not good at contrast resolution. Maybe I’ll start looking at volar forearm muscles more to get my eyes trained.

Just like the more I do PRP work on Hamstring tears as a follow up from MR, the more comfortable I get in scanning them. Practice, practice, practice.

You let me know how you go with the IO-lumbricals impingement work!

[Author]

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