High-arch feet

　　The etiology of high-arch feet is very complex, with about 80% of cases being neuromuscular diseases. These diseases lead to weakened dynamic factors such as the anterior tibial muscle or the gastrocnemius muscle in the lower leg, as well as the contraction of intrinsic muscles on the sole of the foot, resulting in an increased longitudinal arch of the foot. These neuromuscular diseases can occur at different levels, such as the brain's pyramidal system, the corticospinal tract, anterior horn cells of the spinal cord, peripheral nerves, and muscles. Common diseases include corticospinal myelitis, cerebral palsy, myelomeningoceles, and spina bifida. Some diseases are less common, such as myelomeningocele, tethered cord syndrome, and Charcot-Marie-Tooth disease, etc.

　　It is believed that due to the loss of function of the intrinsic muscles of the foot (interosseous muscles and lumbricals), the extensor and flexor muscles appear contracture, leading to hammertoe deformity. It is most common in patients with poliomyelitis, where both the intrinsic and extrinsic muscles of the foot are paralyzed at first, and then the extrinsic muscle strength gradually recovers, while the intrinsic muscles atrophy and fibrotize. Although the function of the nerve支配 is restored, the intrinsic muscles lose function due to contraction, leading to the formation of high-arch feet.

　　However, Bentzon believes that the cause is weakness of the anterior tibial muscle, while the strength of the fibular muscle pulls the first metatarsal bone to make the foot pronate. To compensate for the function of the anterior tibial muscle, the extensor muscles contract to extend the metatarsophalangeal joint, and the secondary contraction of the flexor muscles causes the interphalangeal joints to flex. Some scholars believe that the imbalance between the strong fibular muscle and the weak anterior tibial muscle leads to the appearance of high-arch feet, but most patients with high-arch feet in clinical practice do not have the phenomenon of flaccidity of the anterior tibial muscle.

　　In some cases, there is a clear family history, and there is no evidence of nervous muscle lesions, which may be congenital lesions, or called idiopathic high-arch feet.

　　Regardless of the primary disease causing it, the formation of high-arch foot deformity is primarily due to atrophy of the intrinsic muscle group of the foot. The metatarsal heads sink due to the loss of the power of the extensor muscles, which lowers the anterior limb of the longitudinal arch. Subsequently, the plantar fascia gradually contracts, forming a rigid bowstring, and the top of the bow gradually increases, further increasing the degree of high arch. The composition of the anterior limb of the longitudinal arch of the foot mainly relies on the first metatarsal bone, so the degree of change of the first metatarsal bone can determine the degree of high arch.
　　After the metatarsal heads sink, the extensor tendons attached to the base of the distal phalanx of the toe compensate for increased tension. Over time, this causes excessive dorsiflexion of the metatarsophalangeal joint, even subluxation. Therefore, all high-arch feet are accompanied by hammertoes. After the toes are extended, they cannot contact the ground when standing and walking. In the early stage of walking, the explosive propulsion force between the foot and the ground is lost, so the first metatarsal head exerts force to rotate forward to compensate for this effect, and over time, it gradually forms a rotational displacement.

　　According to the degree of increase in the arch of the foot and whether other foot deformities are associated, high-arch feet are usually divided into four types, and the symptoms of each type are also different:

　　1. Simple high-arch foot

　　The main feature is fixed plantar flexion deformity in the forefoot, with the first and fifth metatarsals bearing weight evenly. The longitudinal arches on both sides of the foot are consistently increased, and the heel still maintains a neutral position, or there is a slight outward deviation.

　　2. Inverted type high-arch foot

　　This type only has plantar flexion deformity in the medial column of the forefoot, namely the first and second metatarsal bones, which increases the height of the medial longitudinal arch of the foot. The lateral longitudinal arch remains normal. When not bearing weight, the fifth metatarsal bone can easily be elevated to a neutral position, while the first metatarsal bone, due to fixed plantar flexion, cannot be passively extended to a neutral position and has a 20-30° internal rotation deformity. The hindfoot is mostly normal in the early stage. When standing and walking, the pressure on the first metatarsal head increases significantly. To reduce the pressure on the first metatarsal head, patients often take an inverted foot posture to bear weight, and fixed inward deformity of the hindfoot appears in the late stage. Patients often have hammertoes, the first metatarsal head protrudes to the sole, the soft tissue in the sole loading area thickens, calluses form, and pain occurs.

　　3. Calcaneal type high arched foot

　　Commonly seen in poliomyelitis, myelomeningocele. It is mainly caused by paralysis of the triceps surae of the lower leg, characterized by the calcaneus being in a plantar flexed position and the forefoot fixed in a plantar flexed position.

　　4. Plantar flexion type high arched foot

　　It often occurs after the surgical treatment of congenital equinovarus foot. This type, in addition to the fixed plantar flexion deformity of the forefoot, also has obvious plantar flexion deformities in the hindfoot and ankle joints. The clinical manifestations of various types of high arched feet are not consistent, but all have fixed plantar flexion deformities in the forefoot. The toes are usually normal in the early stage, but as the course of the disease progresses, the toes gradually retract, the interphalangeal joints are plantar flexed, the metatarsophalangeal joints are excessively dorsiflexed, forming claw toe deformities. In severe cases, the toes cannot touch the ground. Due to the dorsiflexion deformity of the metatarsophalangeal joint, it causes the metatarsophalangeal joint to subluxate, with the base of the proximal phalanx pressed on the dorsal side of the metatarsal head, which will aggravate the plantar flexion deformity of the metatarsal, leading to thickening of the skin at the load area, the formation of callosities, and even ulcers.

　　The etiology of this disease is complex, so it is extremely difficult to prevent it. Therefore, the diagnosis of this disease should pay attention to identifying the cause, distinguishing whether it is secondary or primary, so that appropriate treatment can be taken. After some neuromuscular diseases occur in children, active examination should be carried out to prevent the occurrence of this disease. Parents should pay attention to the appearance and walking posture of the child's feet in daily life and seek medical attention in a timely manner if any abnormalities are found.

　　The main method of laboratory examination for this disease is X-ray examination, and it is necessary to take anteroposterior and lateral X-ray films of the foot under load conditions. Normally, the distal and proximal articular surfaces of the first cuneiform bone are parallel, but in patients with high arched feet, due to the plantar flexion deformity of the forefoot, it often occurs at the first cuneometatarsal joint, causing the parallel line of the distal and proximal articular surfaces to converge on the plantar side. The M'eary angle measures the angle between the longitudinal axis of the talus and the longitudinal axis of the first metatarsal bone. When the arch of the foot is normal, the two lines are continuous. If an angle can be measured, it indicates that the arch of the foot is increased.

　　Measure the angle formed by the longitudinal axis of the calcaneus and the longitudinal axis of the first metatarsal bone. The normal value is 150° to 175°. However, in the case of high arched feet, this angle is reduced. In addition, the anteroposterior view measures the talocalcaneal angle, if

　　Based on the abnormal gait, increased longitudinal arch of the foot with claw toe deformity, and X-ray examination showing an increased M'eary angle, a decreased Hibbs angle, a diagnosis of high arched feet can be made. However, high arched feet are often caused by neuromuscular diseases and should be further examined to find the primary disease or potential risk factors, such as electromyography, cranial or spinal CT or MRI scans.

　　Patients with high arched feet do not have much effect on diet either, and eating legumes or their products and dairy products can be beneficial. This is because legumes contain a large amount of high-quality protein, unsaturated fatty acids, calcium, and vitamins B1, B2, niacin, and others.

　　The conventional treatment for high arched feet in Western medicine generally includes non-surgical treatment and surgical treatment:

　　First, non-surgical treatment

　　Early mild high-arched feet can take passive traction of the plantar fascia that contracts the sole of the foot and the shortened intrinsic muscles of the sole. To relieve the pressure on the metatarsal heads, make the body weight evenly distributed, add a thick 1 cm felt pad at the equivalent position of the metatarsal heads in the shoe, and add 0.3 to 0.5 cm thick on the back and outer side of the sole to reduce the tendency of the hindfoot to invert while walking. However, these measures can only alleviate symptoms and cannot correct the high-arched foot deformity or prevent the aggravation of the deformity.

　　When the high-arched foot has interfered with weight-bearing walking, shoe wearing, or progressive aggravation, surgical treatment should be considered. The surgical methods can be divided into soft tissue release and bony surgery. Generally, based on factors such as the patient's age, type and severity of deformity, the condition of the primary disease, and other factors, the surgical method is selected. In principle, soft tissue surgery is performed first, such as the release of the plantar soft tissue of the foot, the transfer of the anterior and posterior tibial tendons, and the posterior transfer of the extensor digitorum longus. If the soft tissue surgery still cannot correct the deformity, or if older children have fixed high-arched foot deformities, bony corrective surgery can be chosen.

　　Second, surgical treatment

　　The release of soft tissue on the plantar side of the foot is a traditional method, which exposes the plantar soft tissue through a longitudinal incision on the posterior side of the inner edge of the foot, first cuts the plantar fascia, the plantar long ligament, and then

　　Osteotomic correction surgery includes open osteotomy of the first cuneiform, dorsal wedge osteotomy of the talus, V-shaped osteotomy, and posterior calcaneal osteotomy. The V-shaped osteotomy of the dorsal talus has many advantages, as it does not damage the talus epiphysis, so it is suitable for children over 6 years old. It does not shorten the foot and can correct the deformity of the forefoot adduction and internal rotation. The key points of the operation are

　　1. Make a transverse incision or longitudinal incision on the top of the foot, exposing the talus bone outside the periosteum.

　　Design a V-shaped osteotomy line at the apex of the arch, usually located in the central part of the navicular bone, the medial branch extends diagonally from the navicular bone to the medial cortex of the first cuneiform.

　　After completing the osteotomy, the surgeon pulls the forefoot distally and raises it while pressing down on the distal segment of the osteotomy. If there is internal rotation and adduction deformity, the forefoot can be externally rotated and abducted to correct it. Then, a Kirschner wire is inserted from the medial side of the first metatarsal, passing through the osteotomy line to stop at the lateral part of the calcaneus. After the operation, the lower leg cast is fixed for six weeks. After the cast is removed, the Kirschner wire is removed, and an X-ray is taken to observe the healing of the osteotomy. If it has healed, it can gradually start to bear weight and walk.