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I was invited to lecture on the biomechanics of subtalar arthroereisis procedures (which includes the Hyprocure Implant) in October 2009 at the Podiatry Institute’s Reconstructive Surgery of the Foot and Ankle Seminar in San Diego. Since the specific biomechanics of subtalar arthroereisis implants are rarely lectured on, since there is considerable misinformation about what these implants can and cannot do, and since the topic of subtalar arthroereisis implants are becoming of greater interest worldwide, I thought it might be helpful to make my PowerPoint lecture notes available for those that are interested.

 

Thanks Kevin,

Do you or any one else know of any/many people who get a similar procedure for excessive STJ Supination ? Or this a different procedure all together ?

 

Kevin

Considering the common presentation and diagnosis of sinus tarsi compression syndrome (ref here http://www.podiatry-arena.com/podiatry-forum/showthread.php?t=33 post 8) I would have thought that a rigid arthroereisis in the sinus tarsi would tend to instigate this problem. Do you think that it is possible that a person with such an implant would have an antalgic response to pronating the STJ and avoid excessive compression?

I can imagine that if a certain subject had a maximally pronated STJ that was mainly resisted by osseous compression at the sinus tarsi then adding a bush to separate the bony surfaces and therefore change / shorten the moment arm available to GRF relative to the STJ axis at the time when the interfaces compress would relatively reduce the interface compression forces. So where there is little supinating muscular activity e.g. post tib and plastic deformation of the medial ligaments then an arthroereisis would be a good alternative. Which seems to be pretty much what your saying in your lecture notes.

Cheers Dave

 

Dave:

Sinus tarsi pain and extrusion of implants from the sinus tarsi are a known complication of STJ arthroereisis. Jeff Christensen, DPM, (one of my classmates from CCPM) has done some cadaver research on arthroereisis implants and has found very high contact pressures in the sinus tarsi with some of these implants which may explain some of the sinus tarsi pain in using some of these designs. However, many children do quite well with these implants and can run and play without any symptoms. This seems especially important if the children are involved in sports where proper foot orthoses can't be worn (e.g. gymnastics, ballet). Many surgeons recommend these implants only for children, but a few do them on adults also. I have only done the procedure on cadaver specimens. However, a few of my friends who have performed very many of these procedures over the years, such as Donald Green, DPM, has reported excellent results with this procedure.

 

Kevin

Well the proof of the pudding is in the eating then.

Were most of these Arthroereisis implants the soft type?

Dave

 

Dave:

Don performs the arthroereisis implant that has a stem and, I believe, is made of silastic. In speaking with my buddy Jeff Christensen about STJ arthroereisis biomechanics last year at our first "Biomechanics of Surgery Seminar" in Oakland, he says that he has yet to find an arthroereisis implant that reduces the talo-calcaneal contact pressures in his cadaver experiments, due probably to the implants not being custom fit to the sinus tarsi space it eventually occupies. Jeff, I believe, was using Fuji Pressure Sensive Film in his studies on these implants. Hopefully, the next generation of these implants will have better fit to the sinus tarsi than the current screw-in implants (e.g. MBA, Hyprocure) that have recently become more popular.

 

Hi Kevin:

Sorry I missed your lecture in San Diego. What a great place to visit (or live)

Don't you think this procedure has been over utilized simply because it's so easy to perform and, when done alone, completely reversible? I'm not saying it's a bad procedure, what I'm saying is too many are done without proper preoperative evaluation.

For instance, I know of a "surgeon" who has performed this many many times however has recently told me that he has never done a concomitant procedure, not even an Achilles lengthening!

Steve

 

Steve:

I believe you hit the nail squarely on the head. Podiatrists probably shouldn't be doing this procedure unless they are well trained in other flatfoot correction procedures so that the most appropriate procedures may be selected for each patient.

A good example of overuse of this procedure was the local podiatrist who did the STJ arthroereisis procedure on a 38 year old female school teacher with plantar fasciitis that didn't respond to poorly made foot orthoses. The unfortunate lady developed lateral dorsal midfoot pain within a few weeks of the arthroereisis procedure due to over-correction with the arthroereisis and another podiatrist removed the plug from her sinus tarsi which eliminated her lateral midfoot pain but this next left her with chronic sinus tarsi pain. A few months later I was referred the patient for orthoses, made her a better set of foot orthoses and this which ultimately made her sinus tarsi pain vanish within 3 weeks of receiving them. This lady only needed better foot orthoses from the start, but since the original podiatrist had determined that "the patient had failed foot orthosis therapy", she got the arthroereisis procedure and 6 months of frustration, pain and disability.

Sad story, but very true.

 

In case other users don't subscribe to the podiatry today newsletter, there is an article relating to SubTalar joint implants...

http://www.podiatrytoday.com/keys-to-preventing-complications-with-subtalar-joint-implants

 

Interesting discussion on what is an exciting develpment in foot surgery. Have seen quite a few patients who have undergone subtalor arthroeresis for juvenille flat foot & aquired flat foot and without exception have enjoyed good outcomes. Would be interested to hear what protocols are generally followed post operatively regarding orthotic management. Kevin wrote,

If consideration is to be given to reducing these compressive forces, and it seems reasonable to suggest this would be desirable in the long term, surely orthotic management is vital to ensure stability of the implant and surrounding bone?

 

As discussed in the Biomechancial treatment post-op Hyprocure thread Here

 

Cheers Mike - too many threads.....not enough hours in the day......

 

Identifying Risk Factors in Subtalar Arthroereisis Explantation: A Propensity-matched Analysis.
Cook EA, Cook JJ, Basile P.
J Foot Ankle Surg. 2011 Jul-Aug;50(4):395-401.

 

I am take interest in ‘cruciate pivot point’ of Farabeuf? What is it? It's described Chambers in his article "An operation for the correction of flexible flat feet of adolescents", West J Surg Obst Gynecol, 1946;54:77–86. As I understand it's anatomical landmark on the lateral aspect of the canalis tarsi. But what is role of this point in subtalar arthroereisis?
P.S. In my country this article is not available. Anybody help me with this?

 

Effectiveness of surgically treated symptomatic plano-valgus deformity by the calcaneo stop procedure according to radiological, functional and gait parameters
Sakti Prasad Das et al
Journal of Taibah University Medical Sciences; 13 January 2017