When Midfoot Collapse Creates Flatfoot

Noting the pain and potential complications with midfoot collapse, this author details the treatment of a 68-year-old woman who developed flatfoot due to a collapse of the midfoot.

Midfoot collapse can often clinically mimic posterior tibial tendon dysfunction, Stage 2 and higher, as described by Johnson and Strom.¹ However, radiographs and a closer look at the level of collapse can reveal that midfoot degeneration and subsequent collapse is the presenting condition. The collapse can present strictly in the sagittal plane or be a more complex multiplane collapse. Often the rearfoot is well positioned yet the midfoot has collapsed with significant abduction.

One should attempt conservative care for midfoot collapse, including support with orthotics and bracing in combination with activity modifications. Patients often struggle to find shoegear that fits in addition to having pain with ambulation. Some patients present with exuberant bone proliferation in combination with the deformity and this variant can lead to plantar or medial ulceration formation, similar to a rocker-bottom Charcot midfoot collapse.

When conservative efforts do not alleviate pain, consider surgical intervention. Weightbearing images of the foot are typically sufficient to understand the level of deformity, affected joints and bone proliferation. If there is doubt about the affected joints, one can utilize other advanced imaging including computed tomography (CT) scans and magnetic resonance imaging (MRI). If the deformity is unilateral, clinical examination and X-rays of the contralateral limb can help the surgeon establish a “model” of correction specific to that patient. The ability to correct the deformity is powerful across the midfoot and can avoid over- or undercorrection.

A Closer Look At The Patient Presentation

A 68-year-old woman presented for pain and deformity to the left foot. She was having difficulty ambulating due to pain. Her gait lacked propulsive strength as the foot was severely abducted and the medial column had collapsed. There was no motion across the midfoot. A callus had formed at the plantarmedial first tarsometatarsal joint due to the apex of the deformity creating a high point. The calcaneus was neutral in the frontal plane. The ankle joint range of motion had been preserved. She had failed multidensity custom orthotics and refused to wear a custom ankle-foot orthotic prior to being referred to my office.

X-rays show significant degeneration at the first, second and third tarsometatarsal joints. The deformity is present primarily in both the sagittal and the transverse plane. The calcaneus and talus are in normal alignment. The patient was not what I call a “bone former” as there was no bone proliferation surrounding the joint degeneration. No other imaging was necessary and I scheduled the patient for a midfoot fusion with bone grafting and possible tendo-Achilles lengthening. The plan included fusing the first, second and third tarsometatarsal joints to allow the correction around the pivot point in the transverse plane.

Key Insights On The Surgical Correction

In regard to the procedure, one should ensure supine positioning of the patient with the feet at the end of the bed with an ipsilateral hip bump to position the foot vertically. This aids in the midfoot procedure as well as the lateral calcaneal graft harvest. Utilize a thigh tourniquet and prep and drape the leg to the knee.

The surgeon should use a dual incision approach to access the three tarsometatarsal joints. I made an effort to access the first tarsometatarsal joint with a more medial incision to increase the size of the skin bridge between incisions. The second incision is at the midway point between the second and third tarsometatarsal joints longitudinally. This incision is sufficiently long to prepare and fixate both second and third joints. I prefer to open and dissect both incisions prior to making saw cuts. Plan the cuts with the understanding of the desired corrective directions of plantarflexing in the sagittal plane and adducting in the transverse plane.

Make flat cuts with a sagittal saw and remove the degenerative joint in total at all three joints. Manually reducing the joints allows a simulated fusion position prior to moving on. I like to observe the position clinically and under fluoroscopy at this point. Once one is satisfied with the correction, complete the joint preparation via medullary drilling with a solid core drill bit.

Create a 3 cm incision at the lateral calcaneal wall for graft harvest. In this case, I utilized a trephine harvester and morselized and added the graft as necessary at the fusion site.

Add preliminary fixation at the first and second tarsometatarsal joints, and place cannulated screws in standard fashion. If the correction is ideal, complete the fixation with plating. Due to the caliper of the third tarsometatarsal joint, I often will fuse without an interfragmentary screw as the bone real estate is limited. After fixing the midfoot, I will assess the ankle for equinus. A gastrocsoleus release versus Achilles lengthening may be necessary with the corrected position of the new, relatively plantarflexed position of the foot. The procedure is complete after copious flushing and closure in layers avoiding the local neurovascular structures.

The patient uses a posterior splint for two weeks. This is followed by a cast for four weeks with subsequent use of a protected weightbearing boot for a month. One can allow the patient to increase activities as X-rays and the clinical exam dictate.

In Summary

Midfoot collapse creating a flatfoot can lead to pain, difficulty with shoegear and, at times, ulceration. Surgical intervention is often required. The surgery is rewarding and can achieve dramatic improvement. Preoperative planning and intra-operative attention to the desired foot position are critical to avoid under- or overcorrection.

Dr. Bussewitz is a fellowship-trained foot and ankle surgeon who is in private practice at Steindler Orthopedic Clinic in Iowa City, Iowa.

Reference

1. Johnson KA, Strom DE. Tibialis posterior tendon dysfunction. Clin Orthop. 1989;239:196-206.