I. Etiology and epidemiology
Plantar fasciitis is the most common cause of subacromial pain. Most patients are between the ages of 40 and 60 years. Plantar fasciitis is usually caused by traction and microtrauma to the metatarsal tendon membrane of the medial tuberosity of the heel. Other structures involved are the medial heel nerve, or the abductor digitorum profundus nerve. Current studies have found no clear relationship between heel spurs and subacromial pain. The spur is located at the beginning of the flexor tendon of the lesser toe, not at the beginning of the metatarsal tendon membrane. In children, achondroplasia (sever disease) is a common cause of heel pain. In addition, 20% of subacromial pain is caused by entrapment of the 1st branch of the lateral plantar nerve.
Anatomy
The metatarsal tendon membrane begins at the heel bone and consists of three parts. The clinical term for the metatarsal tendon membrane usually refers to the middle part of the metatarsal tendon membrane. It begins at the medial tuberosity of the heel bone, crosses the proximal phalanx and longitudinal metatarsal plate, reaches the seed bone and ends at the proximal phalanx of the bunion. Dorsal extension of the metatarsophalangeal joint tenses the metatarsal tendon membrane, thereby increasing the height of the longitudinal arch of the foot and inversion of the hindfoot. This mechanism is known as the “chain mechanism”.
The medial heel nerve originates from the posterior tibial nerve just below the medial ankle and divides into one or two superficial branches that cross the subcutaneous tissue between the metatarsal tendon membrane and the skin, innervating the skin of the heel. The lateral metatarsal nerve emanates from the lesser toe adductor nerve, which penetrates deep into the bunion muscle and lies beneath the bony tuberosity, innervating the lesser toe adductor muscle and the adjacent periosteum. Nerve entrapment of the lesser trochanter can occur at the medial head of the bunion and metatarsophalangeal muscles. Sensory fibers receive sensation from the periosteum, and motor fibers innervate the flexor digitorum teres and the adductor digiti minimi. The medial and lateral metatarsal nerves cross the fascial foramen of the adductor muscle. In the presence of posterior tibial nerve entrapment, these nerves may be entrapped under the flexor support band below the medial ankle, or they may be entrapped at the point where the medial and lateral metatarsal nerves pass through the adductor fascia.
Pathology
Both high arched feet and flat feet can affect the stress on the metatarsal tendon membrane. A flat foot can cause increased stress at the beginning of the metatarsal tendon membrane and an increased need for the strand mechanism to maintain the arch during the gait cycle. A foot brace, or bandage to assist in keeping the forefoot pronated and the heel turned in, can reduce the stretching forces at the beginning of the metatarsal tendon membrane during the propulsion phase. If there is a high arch foot, the heel bone cannot effectively absorb shock due to the lack of an external rotation mechanism, and the stress on the heel increases.
Many patients with metatarsophalangeal tendinitis have concomitant contractures of the Achilles tendon. The contracture of the biceps calf causes the foot to rotate forward, thus increasing the stress on the metatarsal tendon membrane, which also causes excessive stress on the foot under stopping activity. When the contracture of the metatarsal tendon membrane occurs, the patient’s foot may be positioned like a clubfoot during nighttime sleep. Upon rising, the foot and ankle come to a neutral position and the contracted metatarsal tendon is stretched, resulting in morning “starting pain”. There is no consensus explanation for the pathogenesis of the metatarsal tendons. However, limited mobility and foot morphology have some influence.
History, clinical presentation and physical examination
Metatarsal tenosynovitis is commonly seen in middle-aged patients. Patients usually have a gradual onset without a history of trauma. The pain is gradually concentrated on the medial aspect of the metatarsal surface of the heel bone without radiating pain or sensory abnormalities. The pain is most severe in the morning after waking up and decreases when walking and stretching of the metatarsal tendon membrane begins. The pain worsens if the activity level increases during the day. Severe patients may develop a painful gait, with pain occurring with each step. Acute rupture of the metatarsal tendon membrane is seen after trauma with multiple closures. Patients present with acute pain, swelling, tenderness, and localized bruising may be present.
Patients with flatfoot syndrome may have excessive rotation forward, which increases the pressure on the strand mechanism, and on the metatarsal tendon membrane. When a patient has a stiff high arched foot, the stiffness of the foot causes instability of the foot during distraction loading. Analysis of this different foot deformity is very effective in developing a treatment plan. Special examination of the foot Acute pain is located in the internal calcaneal tuberosity. The pain may originate in the middle of the metatarsal tendon membrane or deep in the toe abductor nerve.
Palpation of the metatarsal tendon membrane can determine whether the pain originates from a stop or the entire tendon membrane. In extension and flexion of the toe, the metatarsal tendons are in both a relaxed and tense state. The metatarsal tendon membrane should be palpated for nodules, which, if present, may be plantar fibromas.
In the case of metatarsal tendinitis, a distinct pressure point can be palpated on the medial aspect of the heel, at the medial heel node. Sometimes patients consider the location of the pain to be variable, and wandering cannot point to a definite pain point. However, such patients have the most pronounced pressure pain at the medial heel node. The pain may worsen with dorsiflexion of the metatarsophalangeal joint. There may be localized swelling. If the pain is deeper in location, there may be a nerve entrapment of the lesser toe adductor muscle.
Ankle dorsiflexion should be performed with the knee joint in flexion and extension. To identify gastrocnemius contracture or hallux valgus contracture. It is important to ensure that the hindfoot is in a neutral position during the examination to eliminate the artifact caused by inversion of the foot.
Atrophy of the heel fat pad causes pain when it is located just below the heel bone. Fat pad inflammation can be detected by palpation. Chronic pain with severe pain due to decompression of the medial and lateral aspects of the heel bone indicates osteochondritis or a fracture of the heel bone.
Percussion of the ankle canal area is performed to check for pain, inflammation, or Tinal sign of the medial and lateral posterior tibiotalar nerves and medial heel nerve. The sensation of the foot is examined. If the patient has proximal or distal radiating pain, a straight leg raise test is performed to rule out spinal nerve disease. The 1st branch of the lateral metatarsal nerve may form a pinch distal to the beginning of the bunion. This should be differentiated from pain in the medial heel node.
The following points are used to differentiate pain under the heel.
1. metatarsal tenosynovitis, the most common.
2. radiating symptoms due to lumbar spinal stenosis.
3, chronic heel fat pad atrophy.
4, fibromatosis, which usually occurs in the arch portion of the foot and can be treated by pressure reduction with a 50% recurrence rate with surgical excision
5, high arched foot or flat foot deformity.
6, contracture of the Achilles tendon.
7, stress fractures of the heel bone.
8, arthrosis due to tendon stop disease.
9, rupture of the metatarsal tendon membrane.
10.Nerve entrapment.
Imaging performance
On x-ray of the heel in the standing weight-bearing position, the subacromial tuberosity is sometimes visible, but this is usually not the cause of pain. Treatment does not cause a change in imaging performance. Isotope examination may reveal fractures and osteochondritis. Bone scans and MRI are not definitive.
Seronegative arthropathy occurs in young male patients with bilateral onset, unilateral asymmetric arthropathy, back pain, hip pain, Achilles tendinitis, and toe inflammation.
Laboratory tests are usually unremarkable. In cases of persistent, bilateral, severe pain, examination for systemic disease should be considered. For example, serologically negative arthropathies. If the patient has chronic, recurrent, severe heel pain, consideration should also be given to examining for ankylosing spondylitis, Achilles tendinitis, and toe infection.
Neurogenic heel pain should also be differentiated. Nerve entrapment of the adductor pollicis brevis, the tibial nerve heel branch, and the medial metatarsal nerve can all cause pain under the heel of the athlete. Local injections of long-acting anesthetic medications can be used to identify the exact location of the lesion.
Ankle Tunnel Syndrome can cause pain in the heel and pain in the sole of the foot. The diagnosis is made if there is a Tinal sign at the ankle canal. Lumbar spinal neuropathy can also cause heel pain, and in rare cases diabetic or alcoholic neuropathy is also seen.
IV. Treatment
(I) Conservative treatment
Treatment of subacromial pain can begin with conservative treatment for 6 months to 1 year, including the following.
1.Stretching exercises for Achilles tendon and metatarsal tendon membrane: 2 to 3 times a day, by the time before running.
2.Reduction of activity: cross exercise to reduce the load.
3.Non-steroidal anti-inflammatory drugs.
4.Night splinting: keep the ankle joint dorsiflexion 5 degrees
5.Physiotherapy: stretching and strength exercise, ultrasound penetration therapy.
6.Braking: line cream or boot braking for 4 weeks.
7.Closure therapy: It can reduce the pain very well, but there is a risk of rupture of the metatarsal tendon membrane.
95% of patients with metatarsal tenosynovitis are effectively treated conservatively. Therefore, non-surgical treatment can completely relieve the symptoms after one year of treatment. Children diagnosed with heel hypertrophy can be treated with a soft Plastazote brace or a heel cup pad combined with appropriate sports shoes.
8.Extracorporeal ultrasound shockwave therapy: Extracorporeal ultrasound shockwave therapy is an effective and safe treatment modality. However, it is not yet widely used in China. Usually the treatment is carried out once a week, and about 80% of the patients’ pain disappears after 3 consecutive treatments.
(B) Surgery
Surgical treatment of refractory or chronic metatarsal tenosynovitis is controversial. Surgical treatment is not used in athletes. It is usually used when other treatments are not available, when the patient receives physical therapy, cast immobilization, night splinting, and when there is no improvement in symptoms in the absence of arthrosis, stress fractures, lumbar spine disease, or nerve entrapment.
Surgical treatment includes metatarsal tenotomy, nerve release, heel bone resection, arthroscopic metatarsal tenotomy, or a combination of these procedures.
The effectiveness of metatarsal tenotomy ranges from 75% to 100%. There is a significant change in symptoms 6 to 8 months after surgery. Some studies have shown that 88% to 100% of athletes who have had a metatarsophalangeal release can start running after 6 weeks to 4 or 5 months. However, some doctors also suggest caution, and in long-term follow-up, only 53% of patients had no limitation of movement, 47% had pain relief, and 49% were completely satisfied. Postoperative plastering is forbidden for 3 weeks and weight-bearing is forbidden for 2 to 4 weeks for short-leg plaster fixation, and activity can be increased after 12 weeks, and postoperative patients may not reach their preoperative activity level
(iii) Complications
Complications of arthroscopic plantar tenotomy include stress fracture, aneurysm, neuroma and pain recurrence. Complications of the dissection procedure include heel fracture, pathological arch instability, heel numbness, neuroma formation, wound healing problems, and wound infection. There is a high incidence of pain in the lateral foot, so when performing a release, it is recommended that only the medial 1/3 of the foot be released. Tendon release can affect the stability of the arch, and metatarsal tendon release is not indicated if the patient has flat feet.