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Hallux Distraction Test

Discussion in 'Foot Surgery' started by Lab Guy, Jul 22, 2014.

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  1. Lab Guy

    Lab Guy Well-Known Member


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    We have static tests such as the Supination Resistance Test and Jack's test and I just wanted to share a test that I used. I am sure this is not a new test but I always called it the Hallux Distraction Test (HDT) since the 1980s. The HDT determines the degree of passive reducibility due to the degree of flexibility/stiffness in the transverse plane between the first and second metatarsal heads.

    The test is performed by loading the MTJ, distracting the hallux to eliminate the retrograde pressure of the base of the proximal phalanx against the first metatarsal head (reverse buckling). You then apply a laterally directed force against the medial aspect of the head of the first metatarsal to passively reduce the IM angle.

    The HDT helps provide information regarding the level of stiffness in the Transverse plane between the first and second metatarsals to determine laxity of the first metatarsal cuneiform joint and if the sesmoids can be relocated plantar to the first metatarsal head. A positive HDT would mean first metatarsal abduction stiffness would be low and the first IM angle would be passively reduced with minimal force.

    The HDT test is also performed intra-op after the appropriate lateral release is performed to see if abduction stiffness of the first metatarsal is reduced.

    For me, I always found the HDT test useful for surgical planning and to select the procedures with the least amount of risks and complications and still receive the most optimum and long term results.

    Steven
     
  2. Ryan McCallum

    Ryan McCallum Active Member

    Steven,
    Could you give an example or two of how your procedure of choice would vary depending on whether or not you get a positive result to your test or not?

    I am pretty sure I get what you are saying but cannot think of a situation where my procedure choice would change. I base my procedure choice primarily on the size of the deformity but also take into consideration amongst other things; patient age, 1st metatarsal length, presence of lesser MTPJ pain and the quality of the 1st MTPJ (presence of adaptive or degenerative changes to the articular surfaces of the joint). I can't say I perform any particular clinical tests that spring to mind that determine the choice of procedure.

    Thanks in advance,
    Ryan
     
  3. Lab Guy

    Lab Guy Well-Known Member


    Ryan, it’s a good question and let me first say that it goes without saying that you need not perform the Hallux distraction test to choose the best HAV procedure for your patient. Many of us already do this test, I just put a name on it.

    Let me give you an example that you requested. A patient has a fairly severe HAV deformity and the IM angle is @ 18 degrees with a normal width metatarsal shaft. His HDT test is postive pre-op and I note that minimal force is required to reduce the IM angle (I also palpate the dorsal IM space as I push the first met laterally with hallux distracted).

    This information tells me that I should be able to mobilize and return the sesmoids back to their rightful place under the first met head to redirect the force vectors. The line of action of the FHL will also no longer be pulling the hallux in a lateral direction.

    My end goal is to avoid a base wedge osteotomy or Lapidus but do a procedure that in my hands provides the best result with the least amount of risks and complications. I would plan on doing an adductor tendon transfer to the tibial sesmoid ligament/medial capsule to bring the sesmoids back under the first met head. I would also perform a distal metaphyseal osteotomy such as an Austin or one of my favorite procedures, a Reverdin Green Laird (RGL) osteotomy. Along with soft tissue rebalancing, I will relign the laterally adapted cartilage of the first met head so that the force from the base of the proximal phalanx is directed more co-axially with the first metatarsal to again create reverse buckling of the first MPJ.

    I find that correcting the lateral adaptation of the cartilage (proximal articular set angle) along with soft tissue rebalancing significantly reduces the IM angle and without resorting to a more aggressive procedure at the base with the higher risk of metatarsus primus elevatus to the longer lever arm the GRF has.

    Now, if it have the same patient but the HDT is negative with a fairly severe HAV deformity, then I know that I will probaly fail in relocating the sesmoids and will most likely have to excise the fibular sesmoid to bring the tibial sesmoid back under and redirect the line of action of the FHL. After I remove the fibular sesmoid, I will perform the HDT intraop and if it is positive, I will not do a base wedge osteotomy. I will peform an Austin or a RGL if I need to correct the PASA.

    To obtain maximum correction and to avoid a hallux varus, I remove the minimal amount of bone from the medial head of the first metatarsal and angulate the blade to remove the least amount from the plantar aspect of the first met head to help maintain proper positoning of the tibial sesmoid within its groove. Also, the less bone I remove, the more I can transpose the capital fragment laterally.

    Patients with square shaped heads, and high dorsiflextion stiffness of their forefoot will usually have stiff metatarsal cuneiform joints and will require quite a bit of force to reduce the IM angle and therefore have a negative HDT. The HDT test is commonly negative intra-op even if the fibular sesmoid is removed due to the high stiffness. I will do a closing wedge base osteomy on these patients (or if they have a narrow first metatarsal).

    Bunions are not life threatening but surgical correction of bunions carry a significant amount of risks and complications. I care less about creating a perfect foot and more about eliminating the pain while creating a pain free, mobile joint with good hallux purchase. Much more often than not, I can utilize soft tissue rebalancing combined with the appropriate the distal metaphyseal osteotmy that has rarely given my patients any complications or new complaints such as sub 2 pain. I loath performing a surgery due to a complication from the first surgery as I failed my patient.

    Lastly, I call myself Lab Guy as I no longer practice but own an orthotic lab. I also want to say that I am also very impressed with the modified Scarf procedure as GRF causes compression of the osteomy site and there seems to be minimal complications. We all tend to do those procedures that we were trained to do and that we feel works best in our hands.

    Steven
     
  4. Ryan McCallum

    Ryan McCallum Active Member

    Thanks Steven.
    Interesting how practices vary so greatly yet one way is not necessarily the correct method.

    I certainly release the sesamoid complex and lateral joint capsule in the majority of my cases but this is always in conjunction with either a first metatarsal osteotomy (a scarf) or a lapidus. I see the soft tissue work as more of a joint 'balancing' element to the hallux vagus correction where as the bony work constitutes the 'corrective' element.

    As you mentioned, much of this comes down to what works best in one's hands and also how we are trained. Generally if you do a lot of something you tend to get good at it. We do loads of scarf and lapidus procedures and our outcomes are generally predictable.

    I suspect as time goes on, I will focus more on PASA correction. I would say that adaptive and degenerative changes to the 1st MTPJ are probably the most common and important factors that will affect the prognosis of hallux vagus correction. I see very little recurrence, 2nd MTPJ pain and non union (2% following lapidus).

    Thanks again for the explanation.

    Regards,
    Ryan
     
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