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Interosseous ligament cutting in arthroereisis- instability?

Discussion in 'Biomechanics, Sports and Foot orthoses' started by alicemo, Dec 21, 2010.

  1. alicemo

    alicemo Member

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    I am a podiatry student and often read these boards to gain information. I have been studying the arthroereisis procedure and have read the various threads on its biomechanics, etc.

    I do have a question though. It seems that in some of these procedures you have to cut/release the interosseoous ligament. Does this mean that it is totally severed or only partly released? Also, does this not predispose the joint to more instability?

    What about a case in which the implant has to be removed due to complications? Once the implant is removed, does more instability result from the prior cutting of this ligament, and/or the tearing of fibers from implant removal?

    Any insight appreciated.
  2. efuller

    efuller MVP

    You have to think about what happens after surgery and with what the talocalcaneal ligament does. The ligament prevents separation of the talus and calcaneus. In weight bearing, ground reaction force and body weight act to compress the talus and calcaneus together. It would be interesting to do some cadaver work to see how much more motion you got after cutting the ligaments that you would need to cut to get an arthroresis plug into the sinus tarsi. My guess is that it would not be very much because the colateral ligaments will also help keep the joint moving pretty much the same way as it did before the interosseous ligament was cut.

    After surgery, there is healing of the wound. Hematoma becomes collegen that is irregularly organized. The scar tissue could become one big massive interosseous ligament. Early range of motion will help organize the collegen into a better ligament. Lots of distraction, post surgery would make a scar/ligament that would not be good at holding the two bones together.

    Your question also points to the definition of instability. In the knee the colateral ligaments are critical for guiding the motion of the tibia relative to the femur. If a knee collateral ligament healed in a slightly longer configuration you could get a lot more abduction/adduction of the tibia relative to the femur in the frontal plane. That, I would call a good example of instability. However, in the talocalcaneal joint, the joint surfaces, especially when compressed together, guide the motion of the joint a lot more than the joint surface of the knee guide the motion. Cutting a ligament does not equal instability.

    Also, what the arthroresis does is decrease the "normal" range of motoin of the STJ. Essentially the arthroesis is a door stop. The door used to hit the wall and now it hits the stop before it gets to the wall. Often instability is equated with an increase in range of motion. So, when you talk about instabiilty you should ask instability in what direction.

  3. That's a very good simple description.
  4. alicemo

    alicemo Member

    Thank you so much for your detailed reply.

    Let me see if I understand what you are saying. After the ligament heals, you would basically not get much more motion because scar tissue reforms the ligament, other ligaments also play a large role in stability, and the joint surfaces also guide the motion. Not to mention the implant that has been placed in the joint... obviously that will stop the motion.

    So, what about if an implant device is removed (with no other procedures performed). Does this not again damage the ligament? And if so, does scar tissue form much like the first time to hold things together? With the implant no longer in place, would the ligament heal in a more stretched manner and cause even more eversion? Or again, would the other ligaments and joint surfaces play more of a role in holding things together?

    This brings me to another question.... which may sound totally ridiculous to educated professions. But I am just learning and it crossed my mind. Instead of an arthroereisis with an implant to reduce eversion, why not cut the interossesous ligament/other ligaments and somehow repair them to heal in a shortened state. Wouldn't that restrict the excesive motion in a more natural way than putting a "doorstop" in the joint? I mean, I'm sure if this was effective then people would be doing it. But why then, doesn't this work fundamentally?
  5. Lee

    Lee Active Member


    These are all good questions and I guess the honest answer is that unless you have done a lot of arthroeresis procedures and removed a lot, you probably can't say for sure. I have performed a few arthroeresis procedures (hardly ever in isolation) and have not had to remove one yet (although I have seen them removed). The most common reason for wanting to remove the implant would be if it came loose/ migrated or irritated. If you did remove it, then it's likely that further scarring would occur (as you have said in your post). I guess this result of the second surgery would depend on the reason for performing it (did the arthroeresis come loose and was it ineffective?) and on the post-op regime to an extent - if the foot was kept relatively immobile after surgery, I suspect you would get reduced ROM as a result and maybe the idea about cutting the ligament would be more likely to work in that case.

    I don't know anyone who is cutting the ligament as an isolated procedure (especially in an attempt to cover the same indications as those for an arthroeresis). I guess you could argue that the arthroeresis 'doorstop' effect provides a local method of immobilising the area too.

    I found the following abstracts which may be of help, but I thought there was a study out there (possibly by Jim Woodburn or Neil Sharkey) that showed the effect of sectioning the ligament on rear foot motion in a dynamic gait replicator (machine that attempts to replicate normal motion of the foot in a cadaver specimen). These all suffer the obvious drawbacks being cadaver studies and all that but check the methodology (in the full papers) regarding how the authors attempted to cut the ligament especially if done in isolation (or attempted isolation) as there are obvious problems with access to cutting the ligament without disturbing any of the surrounding supporting anatomy:

    1. Tochigi Y, Amendola A, Rudert MJ, Baer TE, Brown TD, Hillis SL, Saltzman CL. The role of the interosseous talocalcaneal ligament in subtalar joint stability. Foot Ankle Int. 2004 Aug;25(8):588-96.

    BACKGROUND: Injury of the interosseous talocalcaneal ligament (ITCL) has been recognized as a cause of subtalar instability, though lack of an accepted clinical test has limited the ability of clinicians to reliably make the diagnosis. Clinical effects of ITCL failure remain unclear because of insufficient understanding of the role of the ligament.
    METHODS: Load-displacement characteristics of the subtalar joint were studied in six cadaver specimens using an axial distraction test and a transverse multi-direction drawer test. In all tests, cyclic loading (+/-60 N) was applied, and load-displacement responses were collected before and after sectioning of the ITCL. Two parameters were used to analyze the data: neutral-zone laxity as a measure of joint play, and flexibility as a measure of resistance to applied force.
    RESULTS: In the axial distraction test, sectioning increased both neutral zone laxity and flexibility (p =.01 and.02, respectively). In the transverse test, sectioning caused increase of both neutral-zone laxity and flexibility (p <.001, for each). Neutral-zone laxity increased most greatly along an axis defined roughly by the posterior aspect of the fibula and the central region of the medial malleolus. Flexibility increased most in the medial direction (p <.05, for each).
    CONCLUSIONS: Results confirmed the role of the ITCL in maintaining apposition of the subtalar joint, as well as suggested its role in stabilizing the subtalar joint against drawer forces applied to the calcaneus from lateral to medial. The dominant direction of increased neutral-zone laxity described above suggests the optimal direction for detecting subtalar instability involved with ITCL injury.
    CLINICAL RELEVANCE: ITCL failure may result in subtalar instability and should be examined with a drawer force along the preferential axis roughly from the posterior aspect of the fibula to the central region of the medial malleolus. Further clinical evaluation is required to determine whether ITCL failure is reliably detectable.

    2. Tochigi Y, Takahashi K, Yamagata M, Tamaki T. Influence of the interosseous talocalcaneal ligament injury on stability of the ankle-subtalar joint complex--a cadaveric experimental study.
    Foot Ankle Int. 2000 Jun;21(6):486-91.

    The present study aims to clarify the influence of the interosseous talocalcaneal ligament (ITCL) injury associated with injury to the lateral ankle ligaments on the ankle-subtalar joint complex motion under conditions of physiologic loading.
    We conducted mechanical tests using five fresh cadaveric lower extremities. Each specimen was mounted in the loading device and an axial cyclic load from 9.8 to 686 N was applied. Three-dimensional rotations of the ankle and the subtalar joint were measured simultaneously by a linkage electric goniometer. Mechanical tests were repeated after sectioning of the anterior talofibular ligament (ATFL), and again after additional sectioning of the ITCL. In the intact condition, the ankle and the subtalar joints rotated consistently with increase of the load. The predominant rotations were plantar flexion and adduction at the ankle joint, with some eversion demonstrated at the subtalar joint. Although ATFL sectioning did not significantly change the motion of the two joints, additional sectioning of the ITCL significantly increased adduction and total rotation of the ankle joint.
    The present study demonstrated that a combined injury of the ATFL and the ITCL can induce anterolateral rotatory instability of the ankle joint under conditions of axial loading.

    Merry Christmas :santa:
  6. efuller

    efuller MVP

    What the scar tissue does is not certain. A scar will form, but what the scar looks like and does will be dependent on the used range of motion after surgery. If the motion breaks the bonds of the forming scar tissue then you could get a relatively normal ligament, if you distracted the joint with motion you would probably get an ineffective ligament Wound healing is a very interesting topic.

    The scar will be disrupted with removal of the implant. The scar will probably hold things together. So will ground reaction force and body weight. The interosseus ligament allows pronation and supination while prventing the bones from separating and is not responsible for limiting pronation. Pronation is stopped when the lateral process of the talus hits the floor of the sinus tarsi of the calcaneus. The implant "brings the floor of the sinus tarsi of the calcaneus up to a higher location so motion is stopped sooner.

    As said above, the ligament does not limit eversion. I was fortuneate enough to have access to cadaver feet when I was teaching. It is very helpful to look at the surfaces of the joint when motion is occuring to understand what is really happening.

  7. alicemo

    alicemo Member

    Thank you again for your thorough answers.

    I guess I was understanding the role of the ligament wrong. I thought it helped to limit the amount of pronation present.

    So let me ask another question. You said that pronation is stopped when the talus comes into contact with the calcaneous. But this surely cannot be the only factor in determining the amount of pronation present in a foot, right? If it were, wouldn't the amount of pronation pretty much be "set" and not influenced by things like ligament laxity and pttd?

    I wish I could actually see the inside of a joint as it moves to understand this better. Do you know of any videos or simulations?
  8. Lee

    Lee Active Member


    I don't think your understanding of the role of the ligament was necessarily wrong. Any ligament or section of a joint capsule should limit excessive motion at the joint it surrounds. The following article provides a description of the relative motion of the talus and calcaneus during gait as measured using bone mounted markers:

    Lundgren P, Nester C, Liu A, Arndt A, Jones R, Stacoff A, Wolf P, Lundberg A. Invasive in vivo measurement of rear-, mid- and forefoot motion during walking. Gait Posture. 2008 Jul;28(1):93-100. Epub 2007 Dec 21.

    The aim of this work was to use bone anchored external markers to describe the kinematics of the tibia, fibula, talus, calcaneus, navicular, cuboid, medial cuneiform, first and fifth metatarsals during gait. Data were collected from six subjects. There was motion at all the joints studied. Movement between the talus and the tibia showed the expected predominance of sagittal plane motion, but the talocalcaneal joint displayed greater variability than expected in its motion. Movement at the talonavicular joint was greater than at the talocalcaneal joint and motion between the medial cuneiform and navicular was far greater than expected. Motion between the first metatarsal and the medial cuneiform was less than motion between the fifth metatarsal and cuboid. Overall the data demonstrated the complexity of the foot and the importance of the joints distal to the rearfoot in its overall dynamic function.

    Along with many of its limitations, what the article does not do is provide a reasonable answer as to what directly influences this motion. There's lots of discussion on this forum regarding relevant biomechanics, but all soft tissue crossing the joint and the surrounding bony architecture will have an effect on the function.

    Peter Wolf's paper on MR scan based reconstructions may provide some visual representations of the relative positions of the talus and calcaneus in inversion and eversion, but remember that these were based on static scans of the foot held in a defined position and therefore are unlikely to represent true motion of the joint (but might be helpful to help you visualise motion of the bones):

    Wolf P, Luechinger R, Boesiger P, Stuessi E, Stacoff A. A MR imaging procedure to measure tarsal bone rotations. J Biomech Eng. 2007 Dec;129(6):931-36.

    Magnetic resonance imaging offers unique insights into three-dimensional foot bone motion. Thereby, adequate devices enabling defined loading and positioning of the foot are needed to profit from this noninvasive procedure. Tarsal bone positions of three healthy subjects were repeatedly measured in a pronated and a supinated foot excursion under bodyweight with a newly developed MR imaging procedure. The quantification of the transferred motion from the loading and positioning device to the calcaneus and an estimation of the required degrees to distinguish between tarsal joint rotations were used to evaluate the applicability of the procedure to investigate tarsal joint motion. It was found that 45-70% (75-95%) of the externally applied 15 deg foot pronation (supination) were transferred to the calcaneus. Furthermore, the talonavicular joint showed the largest amount of rotation up to 20 deg eversion-inversion and abadduction, followed by the subtalar joint showing nearly half of that motion. Considerably less motion was found between the cuboid and calcaneus (about 2-6 deg) and the cuboid nearly did not rotate relative to the navicular (on average 1 deg). The estimated necessary differences between tarsal joint movements to identify individual kinematic behavior were in the order of 2 deg (4 deg related to the talonavicular joint). Since the results were in agreement with the literature, it is concluded that the applicability of the presented procedure to investigate tarsal bone mechanics is warranted. The possibility to evaluate 3D tarsal joint motion in combination with bone morphology (e.g., joint curvature) may provide new insights in the still uncertain relationship between foot function and foot morphology.
  9. efuller

    efuller MVP

    I have to disagree. Yes, ligaments limit motion, but they limit motion in a particular direction. The medial collateral ligament of the knee does not limit flexion or extension of the knee, nor does it limit adduction of the tibia relative to the femur (the lateral collateral does.) So, I stand by my assertion that the interosseous ligament of the talo calcaneal joint does not limit eversion and the articles cited don't prove the contrary.

  10. Lee

    Lee Active Member

    No Eric, you don't HAVE to disagree - you choose to disagree LOL! Maybe I was rather broad in my statement, but I guarantee that if you cut all ligaments that provide initial limitation of motion into pronation at the talocalcaneal joint, the remaining ligaments will still provide some resistance to excessive motion. I did not cite the articles to back up this particular point (more for further reading for the original poster), and I was deliberately vague in my statement as I recognise that all soft tissue comprising a joint capsule needs to be sectioned to completely mobilise a joint (as in surgical disarticulation). I choose to disagree that you are disagreeing with me, it's more that we are stating similar points in slightly different ways (LOL again). Your point was more specific to 'normal' motion in a particular direction, mine was very broad for completeness.
    Have a very Merry Christmas,
  11. Alice:

    I am writing an article on the biomechanics of subtalar joint arthroereisis procedures in a few months and this is one of my current lectures I give at seminars. I often make the point in my lectures that these implants "reset the maximally pronated position of the subtalar joint to a new, less pronated subtalar joint rotational position".

    Eric is correct that these ligaments don't by themselves limit pronation. However, these ligaments that lie deep between the talus and calcaneus are very useful at preventing translation of the talus on the calcaneus in any direction that is not the normal tri-plane rotations of the talus on the calcaneus that is, what we call, subtalar joint motion. Without these ligaments, the subtalar joint would be an extremely unstable structure. But, with these ligaments intact, the subtalar joint is probably most tightly constrained joint axis of the whole lower extremity since these ligaments so tightly bind the talus to the calcaneus, that the talus and calcaneus must move in a very set pattern, even though externally applied forces to the foot may be come from many different directions and with greatly varying magnitudes of force.

    In inserting subtalar joint arthroereisis implants, a few of the ligaments are only partially transected and none of the ligaments are transected that don't need to be transected. Depending on the procedure, only those ligaments that "get in the way" of locating the implant properly within the sinus tarsi will be transected.

    I have attached two illustrations that I made for my lecture and that may help you better understand the mechanics of these interesting implants.

    Hope this helps.

    Attached Files:

  12. alicemo

    alicemo Member

    Thank you for the pictures and explanation!

    So, basically, the bone is now hitting bolt instead of bone, right? Does this cause any damage to the bone over time, especially with the titanium implants that are harder than bone?

    What if someone came down on their ankle with an extreme amount of force into an everted position. Could this possibly cause a fracture when the bone hits the harder bolt?

    Sorry for all the questions... it just seems like each answer only leads me to think about more things!
  13. alice do a search for hyprocure on the PA site, we have discussed quite a lot re biomechanics post hypocure - stj arthroeresis.

    But the implant will reduce bone on bone compression forces and replace them with bone -implant then implant-bone compression force.

    Pressure = force/area so if the surface area goes down we will greater pressure. Which may mean problems to the bone later in life.

    But Im not sure of a study on the long term bone remodelling around the stent. Think wolfs law, this new pressure on the bone may lead to stronger bone - which may mean no long term issues.

    Hope that helps
    Ps sent from my phone so maybe many typos
  14. No change there, then. ;):D
  15. Correct. Maybe my typos may mean better spelling :santa:
  16. Alice:

    These are very good questions. Jeff Christensen, DPM, presented some research information on pressure differences on different shaped subtalar arthroereisis implants in a seminar we lectured at together earlier this year and made it clear that the many of these implants, due to their shape being designed more for ease of implantation, rather than to match the bone surfaces better, may greatly increase the bone pressure on the talus and calcaneus within the sinus tarsi.

    To understand how interosseous compression force and pressure within the sinus tarsi changes with variances in subtalar joint axis spatial location, I have attached a paper I wrote 22 years ago on the subject that contains mechanical concepts that are very important in this discussion (Kirby KA: Rotational equilibrium across the subtalar joint axis. JAPMA, 79: 1-14, 1989).

    Attached Files:

  17. efuller

    efuller MVP

    There is talk about removal of implants because of irritation. I haven't removed one so I don't know what is irritated. One possible cause of irritation is that the implant prevents enough STJ pronation that the medial forefoot does not reach the ground with the leg in a "normal" position. Essentially a partially compensated rearfoot varus is created. In that case, there will be a high pronation moment from the ground that has to be resisted by the supination moment created by the implant.

    When there is a large amount of force, either the tissue is able to resist that force or something breaks. Alice the next thing you should read up on is joint compression fractures of the calcaneus. I recall reading a very interesting article by someone who took cadavers and broke some calcanei and examined the fracture patterns. That article, sorry don't remember title etc, is probably 15-20 years old. I don't know if these fractures would be more likely or not with an implant.

  18. alicemo

    alicemo Member

    Do you remember which implant shapes created more pressure than others? Also, do you think it is possible in the future to make implants custom molded to the bone shapes of an individual, kind of like orthotics? I'm not sure how this would be done... since obviously we canot take a mold of the inside of the body. But doesn't that make more sense than a "few sizes fits all" kind of implant?
  19. Alice:

    The cylindrical implants are designed for ease of insertion since they can be effectively "screwed" into place making it a more easily performed procedure. However, these cylindrical implants tend to also have the least congruous fit with the leading edge of the lateral process of the talus and the floor of the sinus tarsi of the calcaneus so that pressures are probably higher with these implants. Some of the most congrous subtalar implants (and which would have the least pressure between the talus and calcaneus) require drilling into the floor of the sinus tarsi which requires more surgical expertise. The very first subtalar arthroereisis implants were basically hand carved pieces of inert silicone elastomer that were sewn into the sinus tarsi and probably had very good congruity but didn't allow easy sizing of the implant (Subotnick SI: The subtalar joint lateral extra-articular arthroereisis: a preliminary report. JAPA, 64:701, 1974).

    Here's my lecture:

  20. Frederick George

    Frederick George Active Member

    I don't think the Grammedica STJae really blocks the lateral process of the talus, like the other plastic "buttons" do.

    It seems to prevent excessive anterior motion of the talus in the saggital plane, limiting excessive pronation. It doesn't have that sudden "door stop" feel of the buttons, but a smoother end of ROM.

    The actual sizing, and prevention of excessive motion is in the canalis, rather than the sinus tarsi.

    Children do much better postoperatively than adults, usually pain free the next day.

    "Conservative treatment" always has a nice ring to it. It doesn't sound a bit like neglect.


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