Last week's post featured a case study of an active 39 year old male with symptoms consistent with both Morton’s Neuroma and 2nd MTPJ capsulitis (predislocation syndrome), both feet left greater than right. Additional significant findings include leg length discrepancy of 5 mm left greater than right, with compensation of increased pronation of the foot on the longer limb. Conservative treatment of both primary conditions alleviated symptoms, and now we are ready to build custom foot orthotic devices to control the underlying biomechanical etiology of the conditions, as well as prevent recurrence of the symptoms and allow the patient to return to his activities with limit possibility of progression of the deformities.
KevinRoot Medical has pathology based models for both Morton’s Neuroma (Model P-9) and Capsulitis/Metatarsalgia (Model P-8). Each of these conditions can occur independently, however in biomechanically challenged feet, multiple conditions may occur simultaneously. When these two conditions are both present the practitioner is challenged to find the most effective orthotic build, due to the dilemma of alleviating one condition that may aggravate the other. Both models will be described independently, including rationale for their respective usage and a hybrid model will be proposed for the very common case described above.
The P9 orthotic device for Morton’s Neuroma has a primary objective of taking as little space as possible within the shoe yet offering adequate biomechanical control to alleviate pressure within the third intermetatarsal space. The frame is a semi-flexible carbon which is thin and lightweight. The rearfoot post is intrinsic and the heel cup is shallow at 6mm to allow the foot to sit as far posteriorly in the shoe as possible. No frame filler is used, the forefoot is balanced to the rearfoot and a .75 mm Protex top cover is used. A neuroma pad (teardrop shape) is added to the third interspace area which should be clearly marked on the scan or cast. Arch height and frame width are at the clinicians discretion, but minimizing volume should be a prime consideration, especially in low volume shoe gear.
The P8 orthotic build for capsulitis/metatarsalgia is a more standard type device with specific features to reduce pressure of the lesser metatarsal heads. It has a polypropylene frame, EVA extrinsic rearfoot posts, 12 mm heel cup, no frame filler, balanced forefoot to rearfoot intrinsic forefoot posting, and a 1.5 mm Spenco top cover. The unique feature is the combination 3mm myolite foot cookie extension and 3 mm met bar pad. The purpose of this design is to shift pressure on the middle three metatarsals from the head onto the shaft of the respective metatarsals.
The case study includes both pathologies being present simultaneously, as well as a limb length discrepency. The ultimate orthotic build for this patient should incorporate aspects of each orthotic type, however it is incumbent on the clinician to prioritize which pathology needs to be addressed. The decision in this case has been made to create a model “8.5” for this patient. It has a polypropylene frame, an intrinsic rearfoot post, an intrinsic forefoot post balanced to the rearfoot, a metatarsal 2-4 pad located just posterior to the metatarsal heads and a sulcus length 1.5 mm Spenco top cover. A semi-rigid frame filler and miniml lowering of the medial arch is included in the prescription to maximize stability and pronation correction of the device A separate 5 mm heel lift will be placed under the right heel.
The orthotic treatment options for this situation are numerous, and it is difficult to prioitize one correction type over another. A hybrid of the P9 and P8 models was selected in an attempt to adequately control the overloading of the second ray yet maintain enough volume to allow foot expansion within the toe box of the shoe and therefore not aggravate the neuroma. Next week’s Forum post will be further discussion of this case, as well as other situations where multiple competing pathologies leads to a paradox in the custom foot orthotic decision making process.
