Metatarsus adductus in the adult is a very difficult foot type to manage. A high arch coupled with metatarsus adductus makes matters even worse. Clinical conditions associated with this foot type include large bunion deformities, Jones fractures, non-traumatic osteoarthritis of the second and third tarsometatarsal joints, dorsal exostoses of the tarsometatarsal joints with peroneal nerve impingement, generalized lateral column pain, ankle instability and peroneal tendon pathologies.
Due to lateral column overload, the lateral half of the foot and ankle will be vulnerable to chronic stress. It is not uncommon for patients with this foot type to have lateral foot, ankle, knee and hip (iliotibial band) pain. In the pronated or flat foot, symptoms and conditions such as medial arch pain and posterior tibial tendon pathology tend to affect the medial structures of the foot and ankle.
I have an EMED (Novel) pedobarograph in my office and I have studied the plantar pressures in patients with metatarsus adductus. I have submitted my data to be published in a peer-reviewed medical journal, which you will be able to read soon. Just as we have all learned that metatarsus adductus feet will overload the lateral column, it has never really been illustrated with plantar pressure measurements. I have been able to demonstrate objectively that the foot with metatarsus adductus will have higher peak pressure on the lateral heel, midfoot and forefoot in comparison to a rectus foot type.
With metatarsus adductus, the common clinical condition of pain in the bases of the lateral metatarsals and cuboid region can be challenging to treat. I call this condition periostitis, which is a stress syndrome. You may call it a cuboid syndrome or synovitis of the fourth and fifth metatarsocuboid joint. These are all acceptable diagnostic terms describing the same thing. I tend to immobilize these patients in a fracture boot, implement an icing protocol and have them take a tapered dose of prednisone. If they cannot take prednisone due to diabetes or intolerance, I will use a nonsteroidal anti-inflammatory medication.
Once the patient is better and returning to a shoe, I stress the importance of wearing a stiff-soled shoe and to avoid barefoot walking, sandals, slippers and flip-flops. From a biomechanical standpoint, I encourage the use of functional foot orthoses. I typically use a hard shell without a heel post and use a cork valgus wedge on the lateral side of the device.
I have observed over the years that if you obtain an ankle magnetic resonance image (MRI) for older patients with a pes cavus and metatarsus adductus deformity, many will have peroneal tendinopathy. These conditions may be split tears or tendinosis. Many times, these pathologies are incidental findings. There is no need to implement any surgery on the peroneal tendons based on MRI findings. If indeed the patient has a clinical correlation with pain in the peroneal tendons, aggressive treatment and/or surgery may be necessary.
Bunion surgery in patients with metatarsus adductus is also very challenging. The clinical deformity will always be worse than the radiographs suggest. There are times when a slight overcorrection of the intermetatarsal angle may be necessary. Moreover, in severe deformities, you may need to perform multiple metatarsal osteotomies in order to get a reasonable correction of the bunion deformity.
Metatarsus adductus occurs in one to two per 1,000 live births. Since the adult with metatarsus adductus is a common finding in the clinical setting, perhaps there should be a better screening effort of newborns. In addition, it may be prudent to be more aggressive in the treatment of the younger population with metatarsus adductus due to the treatment challenges that face the adult with lateral column overload conditions.