30/09/2024
Practical Clinical Use of the Medial Heel Skive Orthosis Technique
The origins, biomechanics and the scientific research on the Medial Heel Skive (MHS) orthosis technique has been reviewed previously. I developed the MHS technique in 1990, and first had my article on the MHS published within the medical literature in 1992 (Kirby KA: The medial heel skive technique: improving pronation control in foot orthoses. JAPMA, 82: 177-188, 1992). Since using the MHS technique now for over three decades in the treatment of my patients, I have learned a great deal as to when the MHS works very well for patients, and sometimes doesn’t work so well for patients. The remainder of this newsletter will focus on how best to clinically use and avoid problems with the MHS technique in custom foot orthoses (CFOs).
When determining the preferred depth of MHS (i.e. 2 mm, 3mm, 4mm, 5 mm, or 6 mm) with CFOs in my patients, a number subjective and objective criteria are used. First of all, after making a diagnosis of the patient’s pathology, the severity of the symptoms is graded. For example, does the patient have such significant symptoms that they can’t walk even a few steps without moderate to severe pain with each step, or is the pain so mild that they can walk 1-2 miles before slight pain occurs due to their pronation-related pathologies. With more severe pronation symptoms, more MHS is used, with a 2 mm MHS being used for milder symptoms and up to 6 mm MHS being used for more severe subjective symptoms.
Second, one of the most important objective criteria to determine the optimum amount of MHS in CFOs is to measure the amount of medial deviation of the subtalar joint (STJ) axis of the foot. To determine the magnitude of medial STJ axis deviation, the STJ axis palpation technique, which I first described in 1987 (Kirby KA: Methods for determination of positional variations in the subtalar joint axis. JAPMA, 77: 228-234, 1987), or the Standing STJ Axis Location Technique, first described in 2017, may be used (Kirby KA: Foot and Lower Extremity Biomechanics V: Precision Intricast Newsletters, 2014-2018. Precision Intricast, Inc., Payson, AZ, 2018, pp. 87-88). Increased medial deviation of the STJ axis will increase the abnormal magnitudes of STJ pronation moments during gait and will increase the need for greater depths of MHS to be included in the CFOs of patients with pronation-related pathologies.
Third, another important factor for determining optimum MHS depth is the amount of abnormal STJ pronation during gait and/or antalgic gait due to the pronation-related pathology of the patient. If the patient is maximally pronated at the STJ from early contact phase and throughout the midstance phase of gait, this means that there are overwhelming STJ pronation moments that will require increased MHS depth to treat their abnormal foot pronation. Also, if the patient demonstrates an antalgic gait pattern due to more painful pronation-related symptoms on one limb than the other, then increased MHS depth should be ordered for the limb that demonstrates more gait pathology.
I have also had my share of problems with the MHS, especially early on after creating the MHS. These clinical learning experiences made me reevaluate when and how I use the technique in my patients’ orthoses over the years. In my original paper on the MHS, I warned that there may a possibility of medial-plantar heel pain from the increased varus heel cup shape created by the MHS. To date, I have seen medial-plantar heel pain only a handful of times with less than 1% of my patients experiencing any increase in medial-plantar calcaneal pain from my MHS orthoses.
To reduce the incidence of plantar-medial calcaneal pain from MHS orthoses, the thickness and integrity of the plantar calcaneal fat pad should be evaluated in every patient to determine how much MHS depth may be ordered. If the plantar calcaneal fat pad is found to be very thin, or if the fat pad is found to possess little ability to cushion the plantar calcaneus, a reduced the amount of MHS depth by 2 mm is ordered (i.e. a 4 mm MHS is reduced to 2 mm MHS). In cases of fat pad atrophy, an extra thick PPT or neoprene topcovers may be added to the dorsal orthosis shell to reduce the risk of plantar calcaneal pain from the MHS orthosis.
Early on in using the MHS in children’s orthoses in the 1990s, I also discovered that too much MHS can cause problems. As an example, in one symptomatic flatfooted 7-year-old boy, an 8 mm MHS was initially ordered in his orthoses to attempt better “correction” of his abnormal STJ pronation. However, three weeks after orthosis dispensing, the mother complained that the medial-posterior heels of her son’s shoes were wearing out abnormally and that he was excessively in-toed during gait, causing a clumsy gait pattern. The boy’s orthoses were then immediately remade with a 4 mm MHS which produced not only an improvement in gait but also normalized the boy’s shoe heel-wear pattern.
As a result of this experience from over a quarter-century ago, I now no longer use an 8 mm MHS depth in CFOs, with a 6 mm MHS depth being the maximum amount ordered in any CFO for any patient. This experience also provided me with an early, valuable lesson on how mechanically-powerful the MHS can be in supinating the feet of some patients.
Too little MHS depth can also create problems for patients. If too little MHS depth is ordered into orthoses, the ability of the orthosis to improve gait and reduce foot and/or lower extremity pronation-related symptoms may be reduced. For example, if MHS orthoses are dispensed to a patient and their pronation-related symptoms are not improved, a strip of 3-mm adhesive felt may be adhered to the medial orthosis heel cup to simulate how an additional amount of MHS depth will affect their gait and their symptoms (see my illustration below). If their symptoms and gait improve with the addition of this additional amount of varus heel cup shape in their orthoses, then a 2-3 mm layer of korex is glued and ground into the medial heel cup area of the orthosis. Alternatively, the orthosis lab may be requested to make a new orthosis for the patient with more MHS depth.
All in all, the MHS orthosis technique can be a very valuable clinical tool for increasing the therapeutic success of CFOs for patients with pronation-related pathologies of the feet and lower extremities. By carefully evaluating and analyzing the subjective complaints and the objective findings of their patients, the clinician will be able to increase the comfort and effectiveness of CFOs for their patients. Mastering when and how to use the MHS orthosis technique in patients with pronation-related pathology will help the podiatrist develop a more successful specialty custom foot orthosis clinical practice.
[Reprinted with permission from: Kirby KA: Precision Intricast Newsletter, Precision Intricast, Inc., Payson, AZ, November 2021.]
