Metatarsalgia

　　Metatarsalgia is a pain in the sole caused by the compression of the toe nerve by the metatarsal head. Metatarsalgia is a disease caused by muscle, ligament, joint, nerve, blood circulation disorders, systemic diseases, or infection. Metatarsalgia is a common foot disease.

　　(I) Changes in the biomechanics of the forefoot

　　Changes in the biomechanics of the forefoot caused by various reasons, causing the middle metatarsal to bear greater stress.

　　1. Various lesions of the big toe reduce the load-bearing capacity of the big toe, causing the load to transfer to the lateral toes. Such as hallux valgus, rigid big toe, arthritis of the first metatarsophalangeal joint, etc.

　　2. The middle three metatarsals have less mobility and are more stable. If the lateral and medial columns of the foot are excessively active, the middle metatarsals will bear greater stress.

　　3. Deformities such as hammertoes caused by various reasons, which cause the proximal phalanx of the toe to dorsiflex and compress the metatarsal head plantarly, causing the metatarsal to bear greater stress.

　　4. Contracture of the Achilles tendon or gastrocnemius tendon, which makes the foot unable to dorsiflex sufficiently during gait, and the forefoot will bear greater stress.

　　(II) Variations or changes in anatomical structures

　　1. Congenital over-shortening of the first metatarsal. Also known as Morton foot. The big toe has a lower load-bearing capacity, and the stress is transferred to the lateral toes.

　　2. Congenital overlength of the second metatarsal. In the propulsion phase of gait, the overlong second metatarsal becomes a 'lever', bearing greater stress.

　　3. High-arched feet. The rigid structure of the foot does not allow it to absorb and buffer stress well; the metatarsal head often becomes a focal point of stress.

　　4. Previous trauma and surgery, over-shortening or elevating the first metatarsal.

　　5. Decreased height of the middle metatarsal. Such as the hyperplasia of fractures or metatarsal head lesions.

　　(III) Inflammation of the metatarsophalangeal joint

　　1. Rheumatoid arthritis. The synovial lesions can damage the ligaments and tendons around the joint, and in the late stage, the metatarsophalangeal joint often appears with dorsal dislocation, the metatarsal head protrudes towards the plantar side, causing pain.

　　2. Synovitis caused by other reasons.

　　3. Osteoarthritis of the metatarsophalangeal joint.

　　(IV) Injury

　　1. Cartilage injury of the metatarsal head.

　　2. Ischemic necrosis of the metatarsal head.

　　3. Instability of the metatarsophalangeal joint.

　　(V) Other causes

　　1. Intermetatarsal neuroma. The common peroneal nerve is compressed, causing pain around the metatarsal heads.

　　2. Fatigue fracture of the metatarsal bone.

　　3. Hyperkeratosis of the skin.

　　Metatarsalgia can be accompanied by hammertoes, where the toes are claw-like. This toe deformity affects three joints of the toe, causing excessive extension of the metatarsophalangeal joint, and bending and deformation of the proximal and distal interphalangeal joints due to muscle or nerve tension that is too tight and unbalanced. This results in a fixed deformity due to the dorsiflexion of the metatarsophalangeal joint and the plantar flexion of the proximal and distal interphalangeal joints. Therefore, the toes are prone to produce thick calluses due to friction.

　　Metatarsalgia manifests as a burning pain under the metatarsal head, the pain is lightning-like and radiates to the toes or lower leg, sometimes there is a feeling of the metatarsal head slipping out, which can be relieved after rest or changing shoes.

　　First, loose metatarsalgia

　　1. There is a persistent pain on the transverse ligament on the plantar surface of the metatarsal head of the forefoot, which is immediately alleviated or disappears when not bearing weight. Sometimes, the patient is afraid to put the sole of the affected foot on the ground when walking or standing, and sometimes the pain can be alleviated by changing the force point.

　　2. Lateral compression of the metatarsal head can alleviate pain, and a gap can be felt between the first and second metatarsal heads.

　　There are calluses on the second, third, and fourth metatarsal heads on the sole, and the toes of the patients with atrophy of the interosseous muscles are claw-shaped.

　　Second, compressive metatarsalgia

　　1. There is a lightning-like pain or paroxysmal radiating pain under the metatarsal head of the forefoot.

　　2. Compression of the metatarsal head can exacerbate or induce pain.

　　3. There is a phenomenon of compression on the forefoot, and the affected toe is long and slender.

　　Metatarsalgia is caused by a congenital short first metatarsal bone, and there is currently no effective preventive measure. To avoid pain, patients should wear loose, soft shoes, avoid wearing high heels and shoes with hard soles, avoid prolonged standing and walking, and can also self-massage the bottom of the forefoot, or place the affected foot on some smooth convex object, roll and rub the front foot, such as health products such as moon cars and foot massagers.

　　During the physical examination of metatarsalgia, attention should be paid to whether there is a hammer toe, excessive pronation of the forefoot, instability of the medial and lateral columns, condition of the arch, calcaneal and gastrocnemius tendons, and tenosynovitis. Swelling of the metatarsophalangeal joint, the degree of movement and stability of the joint. The location of tenderness, most patients have tenderness on the plantar side of the metatarsal head. Tendons and metatarsal plates may be damaged, and tenderness may be located far from the metatarsophalangeal joint. Tenderness over the metatarsal head should be suspected of fatigue fracture. Patients with rheumatoid arthritis generally have hallux valgus on the forefoot, and other toes are claw-shaped. For patients with unstable metatarsophalangeal joints, the Lachman test of the metatarsophalangeal joint shows a positive result.

　　X-ray is of great significance for diagnosis. It can understand the length of the metatarsal and whether there are lesions and injuries in the metatarsophalangeal joint. For some patients who cannot clearly identify the site of the lesion, a mark can be placed on the painful site, and then X-ray is taken to help determine the cause. For metatarsal fatigue fractures, there is often no manifestation on the X-ray in the first two weeks after the onset of symptoms, and a re-examination is needed.

　　It is also necessary to perform blood tests such as erythrocyte sedimentation rate, rheumatoid factor, C-reactive protein, and blood uric acid.

　　Metatarsalgia is caused by a congenital short first metatarsal bone, which cannot effectively bear weight and needs the second or third metatarsal bone to substitute, thus causing the disease. It is unrelated to diet, and normal diet is sufficient. The patient's diet should be light and easy to digest, with an emphasis on eating more vegetables and fruits, and a reasonable diet should be balanced. In addition, patients need to avoid spicy, greasy, and cold foods.

　　Patients with metatarsalgia feel pain on the plantar side of the forefoot, which worsens with walking and usually subsides after non-weight-bearing activities. They cannot wear thin, hard-soled shoes or high heels. Sometimes, there may be swelling of the metatarsophalangeal joint. There is often a painful callus on the plantar side of the metatarsal head. So, how should it be treated?

　　1. Non-surgical Treatment

　　(1) Reduce activity. Avoid walking on hard roads for a long time in shoes with thin soles.

　　(2) For simple painful calluses, you can go to a bathhouse or use a special trimming knife to cut or grind off the thickened calluses yourself, which can alleviate pain. However, it cannot cure metatarsalgia, only alleviate symptoms, and trim once every 2-3 months.

　　(3) Foot pads. For most metatarsalgia, it is due to increased local stress on the sole. Using soft foot pads can cushion local stress. Another type of foot pad is to support the proximal end of the metatarsal head, thereby reducing the stress on the metatarsal head.

　　(4) Wear hard, arched-bottom shoes, and use soft insoles inside the shoes. When walking, this can reduce the stress on the forefoot and alleviate symptoms.

　　(5) For hammertoe deformity, orthopedic devices can be used to correct the flexion of the interphalangeal joints and the extension of the metatarsophalangeal joints, so as to reduce the pressure on the metatarsal head by the proximal phalanx.

　　(6) Inflammation and synovitis of the joint caused by tendons, joint capsules, and ligament injuries can be treated with physical therapy and closed treatment.

　　(7) Use non-steroidal anti-inflammatory analgesics.

　　(8) Hormone injections can also be used around the common digital nerve between the two metatarsal heads for intermetatarsal nerve tumors.

　　(9) Wear forefoot unloaded shoes for 2 months during fatigue fractures.

　　2. Surgical Treatment

　　If non-surgical treatment is ineffective, and the symptoms are severe, affecting life and work, surgical treatment can be considered.

　　(1) The most commonly used surgery for metatarsalgia caused by increased local stress is to osteotomize the corresponding metatarsal, so that the metatarsal head is raised or the metatarsal is shortened. Such as Weil osteotomy at the neck of the metatarsal head.

　　(2) For hammertoes, it is necessary to release the surrounding soft tissue of the metatarsophalangeal joint, such as extending the extensor tendons, collateral ligaments, and metatarsal plate release. The flexural deformity of the interphalangeal joints requires osteotomy, or joint fusion and artificial joint replacement.

　　(3) Synovitis of the joint caused by cartilage injury of the metatarsal head can be treated by cleaning the synovium and fragmented cartilage. Severe deformation of the metatarsal head requires excision of the metatarsal head and artificial joint replacement.

　　(4) The intermetatarsal nerve tumor can be treated by releasing or excising the common digital nerve.

　　(5) In the forefoot of patients with severe rheumatoid arthritis, there is often a marked metatarsalgia, which often requires forefoot reconstruction surgery. Fusion or joint replacement of the first metatarsophalangeal joint, excision of the second to fifth metatarsal heads.