Hallux valgus is one of the most common disorders of the foot, and is the most prevalent disorder of the bunion. Hallux valgus is a medical term, in addition to the terms “big toe” and “big goblet crutch”. In English, bunion also refers to a bunion, specifically the protrusion on the inside of the foot when a bunion occurs. The definition of a bunion is a bunion that is diagnosed when the angle between the proximal phalanx and the first metatarsal is greater than 15°. This angle is called the Hallux valgus angle (HAV). The bunion is a morphologic diagnosis and does not properly define the pathologic course of the bunion.
The degree of bunion can be broadly understood by referring to the self-diagnostic chart: A is normal, B has a bunion angle of about 15°, and C, D, and E have bunion angles in 15° increments.
I. Etiology
The most important etiology of bunion is considered to be genetics and shoe wear, in addition to flat feet, the 1st metatarsal is too long or too short are also related factors. There is a clear genetic predisposition for bunions, usually seen in female members of the family, and the gender ratio of incidence is: male: female = 1:9-15.
In the analysis of Sim-Fook and Hodgson’s survey, 33% of the 118 people who wore shoes had bunions, compared to 2% of the 107 people who did not wear shoes. kato reported a significant increase in the incidence of bunions in the Japanese population due to an increase in the number of people wearing western-style shoes. The significant restriction of the forefoot when wearing high heels makes it easier for bunions to form.
Bunion is a condition that occurs after skeletal development has matured. There is a correlation between bunions and flat feet, but the causal relationship needs to be further investigated. The peak incidence of bunions is between the ages of 20-30 and 50-60. Younger patients are associated with genetics and wearing high heels; older women aged 50-60 are associated with genetics and postmenopausal endocrine changes.
Second, anatomy and pathophysiology
Anatomically speaking, the bunion deformity includes anatomical changes such as
1st metatarsal inversion;
Bunion valgus, posterior rotation ;
bunion, contracture of the lateral joint capsule;
Dislocation of the seed bone in relation to the 1st metatarsal head;
Loss of normal anastomosis of the 1st metatarsophalangeal joint;
Medial bunion formation of the 1st metatarsal bone, complicating bunion;
Complicated osteoarthritis of the 1st metatarsophalangeal joint;
Other foot disorders caused by bunions include.
Hammer toe of the 2nd-4th toes (Hammer toe);
Metatarsophalangeal joint subluxation (MTP joint subluxation);
Cross-toe deformity;
Transfer metatasalgia;
The first metatarsophalangeal joint consists of two long tubular bones with seed bones and surrounding ligaments, tendons and soft tissues. There are no muscles attached to the first metatarsal, while the proximal phalanges have a large number of muscles and tendons attached, mainly the bunion, thumb flexor, bunion flexor, and thumb extensor muscles. On the metatarsal surface of the 1st metatarsophalangeal joint, there is a tough metatarsal plate – consisting of the joint capsule, the bunion tendon, the bunion extensor, the metatarsal portion of the bunion extensor, and the medial and lateral collateral ligaments. On the metatarsal side, on the thumb flexor tendon, there are two seed bones that form a metatarsal seed joint with the first metatarsal. The two seed bones are separated by the bony crest of the metatarsal bone and are crossed by the long thumb flexor tendon between them.
The shape of the first metatarsal head varies from person to person, with the rounded metatarsal head having a less stable articular surface. The angle between the articular surface of the first distal metatarsal and the axis of the first metatarsal is called the articular surface inclination angle (DMAA, Distal metatarsal articular angel), which also varies among individuals.
Third, the bunion occurs as a gradual process.
First, the bunion is subjected to an outward force, causing the proximal phalanx of the bunion to form an angle with the first metatarsal;
After the angle is formed, the tendons of the long bunion extensor and bunion retractor muscles form the muscle force that aggravates the deformation of the bunion during the gait lift phase. This causes the medial joint capsule to extend and bunion and metatarsal head osteophytes to develop; at the same time, the lateral joint capsule tightens, making it difficult to recover from valgus.
As the metatarsal head is inwardly retracted, while the seed bone remains unchanged in the tendon relative to the foot, a relative dislocation of the seed bone occurs.
With the metatarsal inversion and bunion valgus, the bunion extensor muscle slides underneath the metatarsal head and rotates the bunion through its proximal bunion stop pulling action, forming a bunion rotation back.
After the onset of bunion, the forefoot becomes wider and it is difficult to wear shoes. The medial expansion of the bunion joint is mainly formed by the bony bulge on the medial side of the 1st metatarsal bone. The expanded tissue aggravates the friction after wearing shoes and forms a bunion. In some cases, the enlargement is due to a large angle of inclination of the joint surface, forming a medial bone protrusion, and the 1st metatarsal bone is tilted inward, forming a medial bunion protrusion.
There is a special category of bunion patients in which the valgus deformity is caused by ectropion of the interphalangeal joint of the bunion. In these patients, the angle between the distal and proximal phalanges of the bunion is too large, while the degree of inversion of the 1st metatarsal is not severe. Although the cosmetic manifestations are more severe, the surgical treatment is different.
IV. Clinical manifestations
The most important clinical manifestation of a bunion is pain, and the complaints usually include
Pain at the bunion;
Pain in the first metatarsophalangeal joint;
pain under the 2nd and 3rd metatarsal heads of the foot with callus;
pain under the seed bone;
Numbness of the skin;
Pain and deformity of the 2nd toe – hammertoe, straddle toe, dislocation of the 2nd metatarsophalangeal joint;
Pain and deformity of toes 2-4;
As the quality of life improves, the aesthetic impact on the foot is also one of the reasons why patients seek medical attention.
V. Physical examination
The first step of the clinical examination is to take a medical history, paying attention to the patient’s history of previous surgery and trauma. By taking the history, it is important to understand the patient’s expectations for bunion treatment. Patients who report unrealistic expectations also tend to have poor treatment outcomes. It is also important to have a history of diabetes mellitus, rheumatoid arthritis, and systemic diseases.
The patient’s entire foot should be examined during the physical examination. This includes the hindfoot, the arch, and each toe of the forefoot. Check for signs of neuropathic pain.
The patient’s bunion should first be examined for the degree of bunion and whether it can be manually repositioned. After repositioning, check the mobility of the metatarsophalangeal joint and determine the joint surface inclination and joint anastomosis. Note whether the patient’s bunion is rotated or not. The bunion is painful or not. The interphalangeal joint should be noted for pain and valgus.
Check for normal mobility of the 1st metatarsophalangeal joint. Maximum passive dorsiflexion can usually be 65°-75° and maximum passive plantarflexion is 15° or more. A maximum passive dorsiflexion of less than 65° is usually a sign of bunion stiffness. The presence of pressure pain in the joint space suggests the presence of osteoarthritis, and cartilage may be damaged to varying degrees.
The patient should be noted for seed bone pain, and x-ray examination may also reveal seed bone hyperplasia.
Check the patient’s metatarsal cuneiform joint for laxity. The patient is instructed to pay attention to the changes of the medial arch when standing. When examining the metatarsocuneiform joint, the patient is in a sitting position, pinch 2-4 metatarsals with one hand and the head of the 1st metatarsal with the other hand and move up and down, if the mobility exceeds 7°-10°, the laxity of the metatarsocuneiform joint cannot be excluded. An objective criterion for evaluating metatarsocuneiform joint laxity is lacking.
Check 2-4 toes for hammertoes, riding toes, painful calluses under the 2nd and 3rd metatarsal heads, and painful, dislocated 2nd metatarsophalangeal joints.
Check the dorsalis pedis artery pulsation and nerve sensation in the foot, and note whether the patient’s pain is neurological and not caused by the bunion.
Sixth, auxiliary examination
A weight-bearing X-ray of both feet should be taken during the bunion examination. The weight-bearing X-ray is the main test for preoperative and postoperative evaluation of bunions.
It has been reported that the 2nd metatarsal is noted as the mid-axis of the foot with a fixed relative position during X-ray measurements; however, patients with severe bunions have metatarsal inversion, a condition that is discussed in a separate article. The axis of the backbone was determined according to the measurement method reported by Coughlin M. J.: the reference point of the axis was taken from the 1st and 2nd metatarsals at 1 cm and 2 cm from the most distal articular surface and the base of the proximal metatarsal to make a vertical backbone straight line and take the midpoint; the proximal phalanx of the bunion was taken from the distal and proximal ends at 0.5 cm and 1 cm and then took the midpoint to make the axis.
The parameters that need to be obtained after measuring the orthogonal x-ray are
Bunion angle (HAV) – the angle between the axis of the 1st metatarsal and the axis of the proximal phalanx of the bunion, normal is 15° or less.
Intermetatarsal angle (IMA) – the angle between the axes of the 1st and 2nd metatarsals, normally less than 9°.
Distal metatarsal articular surface inclination angle (DMAA, PASA) – the angle between the joint surface line of the 1st metatarsal head and the 1st metatarsal axis, normal lateral inclination is less than 7.5°.
Angle of interphalangeal exostosis (HAIA) – the angle between the proximal and distal phalanges of the bunion. It is usually less than 10°.
The measurement should also pay attention to the anastomosis of the 1st metatarsophalangeal joint and the presence or absence of osteoarthritic manifestations on the joint surface. The seed bone is dislocated and there is no variation in the seed bone. If the patient has lateral submetatarsal pain, note the length of the 1st metatarsal and whether it is relatively too short. Also note the presence of arthritic changes in the 2nd and 3rd metatarsophalangeal joints.
An axial examination of the seed bone can also be performed to evaluate the seed bone dislocation, and the position of the seed bone should be considered during surgery to allow for the possibility of postoperative complications of seed bone pain if the dislocation cannot be surgically corrected.
VII. Treatment of bunion
1.Conservative treatment
Changing shoes is the most important way to influence the effect of conservative treatment. Patients wearing comfortable shoes and shoes that fit well are the main influencing factors for the success or failure of conservative treatment of bunions. If pain is dominated by redness and swelling of the medial bunion, wear shoes with a wide foreshortening to reduce extrusion and friction. If the patient has submetatarsal head or subseed bone pain, a forefoot decompression foot pad should be added to reduce pressure to alleviate the pain. If the pain comes from 2-4 toes, hammer toe pads, small toe smooth toe pads, and interdigital toe pads can be used to reduce friction and pressure according to the cause of pain.
2.Surgical treatment
Patients for whom conservative treatment is ineffective can undergo surgical treatment. The factors to be considered in the treatment are.
1, what is the cause of the patient’s pain, surgery to solve the patient’s pain problem;
2, if the bunion is one of the causes of pain, then bunion surgery should be performed;
3, bunion caused by the lateral 2-4 toe deformity, you need to correct the bunion first, and correct the small toe deformity at the same time;
4.Pre-operative X-ray measurement should be performed in weight bearing position to observe the deformity characteristics of the X-ray joint, metatarsal, seed bone and little toe before deciding on the surgical procedure;
5, before surgery to evaluate whether the patient’s foot nerve and blood flow situation can be operated, if there is nerve-induced pain, postoperative and can not relieve the patient’s pain ;
6.Surgery has certain complications. After the surgery, the athlete may not be able to return to the field due to the limited movement of the 1st metatarsophalangeal joint. In addition, there may be a recurrence of deformity after surgery, especially in adolescent patients. Pain may remain after surgery;
7. Other common complications include bunion, relative shortening of the 1st metatarsal, metatarsalgia, infection in the surgical area, dermatomal neuritis, etc;
8.Irritation of the skin by the internal fixation may also occur;
9.After the postoperative X-ray angle correction, the enlargement of the medial bunion may remain, which is a scar tissue and can be reduced with time.
VIII. Contraindications to surgery
Surgery should not be performed if the metatarsophalangeal joint is infected, if there is poor blood flow, if the patient has poor compliance, or if there are unrealistic expectations for surgery, because surgery has its own limitations. Surgery is also contraindicated when there is osteoarthritis in the first metatarsophalangeal joint. Patients with laxity of the 1st metatarsocuneiform joint should be considered for Lapidus surgery or metatarsocuneiform fusion.
It is important to talk to the patient before surgery to understand what the main cause of foot pain or discomfort is, and to confirm this with physical examination and x-ray. If the decision is based solely on physical examination and radiographs, problems may remain and cause postoperative pain to persist.