Etiology, clinical examination and non-surgical treatment
The theory of bunion pathogenesis and proper treatment has been very much discussed in the orthopedic literature. The wealth of information related to the surgical treatment of bunions has been modeled into what we often call treatment procedures and principles. These procedures and principles are intended to ensure a uniform approach to the treatment of symptomatic bunions, but the variety of approaches to treating bunions has made them a formality. This article presents a review of contemporary treatment perspectives, considering the pathogenesis, examination, and treatment of bunions. The review is divided into two parts because of the large amount of content. Part 1 includes background, etiology, pathogenesis, representative clinical examinations, and non-surgical treatments. Part 2 focuses on surgical treatment and possible complications.
The reader is reminded here that bunion is a complex deformity and our understanding of it may be incomplete. Surgical treatment of bunions can be difficult. The notion that the surgical treatment of bunions is evolving is a false argument, and today we can only say with certainty that the surgical approach remains variable. There is consensus on the established treatment process, but this article suggests that the surgical capital should be individualized for the particular patient when treating bunions.
Historical review and etiology
Bunion, a word derived from the Latin Bunion, meaning bighead, is a term that does not clearly define the disease. To our knowledge, the first person to publish Hallux Valgus was Carl Hueter in 1870. bunion (Hallux valgus) is a progressive disease that develops due to poorly fitting shoes. There is support for this idea, but there is insufficient evidence that ill-fitting shoes are a causative factor for bunions. On the contrary, the observation that many people do not develop bunions despite wearing ill-fitting shoes for many years suggests an inadequate definition of bunion predisposing factors. Other studies have reported the onset of bunions in individuals who do not wear shoes, suggesting that congenital factors are a predisposing factor. Adolescent and male feet are not compressed by pointed shoes but develop bunions, suggesting the presence of congenital factors. The association of bunions with female gender has also been proposed as a common predisposing factor for bunions. The exact etiology of bunions remains unclear and may be a function of multiple factors. However, there is a tendency for bunions to worsen over time, which seems to be associated with repetitive stress on the 1st metatarsophalangeal joint.
Pathogenesis
Anatomical factors
In individuals without bunions, the alignment of the bunions and metatarsophalangeal joints is: 1) symmetrical alignment of the proximal articular surface of the 1st phalanx with the articular surface of the 1st metatarsal head under repeated joint stress during the gait cycle; 2) normal physiologic position of the distal articular surface of the 1st metatarsophalangeal joint in relation to the axis of the 1st metatarsal stem; 3) stable, balanced soft tissue around the 1st metatarsophalangeal joint; and 4) a stable 1st metatarsocuneiform joint. There are no muscles or tendon junctions on the 1st metatarsal head, so changes in these physiologic factors can cause a bunion to occur.
The bunion is repeatedly pushed into a valgus position by forces, especially during weight bearing and walking, which ultimately causes the 1st metatarsophalangeal joint to valgus. The aggregation of ground reaction forces and the force of muscle activity cause the medial joint capsule to become weak, the lateral joint capsule and bunion tendon to contract, and the subsequent medial displacement of the 1st metatarsal head (creating a bunion).
Ground reaction forces may play a role in the gradual formation of the bunion. The forefoot is subjected to ground reaction forces greater than its weight with each step it takes. As these forces are transmitted across the metatarsal weakness of the bunion, the 1st metatarsal toe moves through physiological mobility. If the forces are transmitted to the medial metatarsal aspect of the bunion, these structures restrict the medial aspect of the 1st metatarsophalangeal joint and subsequently become weak. In this one model, any factor that acts on the medial aspect of the bunion and causes weight-bearing asymmetry can trigger a bunion. Narrow shoes and laxity of the 1st metatarsophalangeal joint can produce this type of situation.
Muscle forces that change through the 1st metatarsophalangeal joint also play a role in the development of bunion deformity. If the pulling forces of the medially active structures, especially the bunion tendon, are directed towards the metatarsal plane, then the forces against the bunion retractors are lost. The extensor hallucis longus (EHL) and flexor hallucis longus (FHL) will gradually become a group of forces acting on the lateral aspect of the joint. The metatarsal tendon membrane (strand mechanism) also shifts laterally, as does the short thumb flexor tendon. These contraction forces cause the ridge under the head of the 1st metatarsal to fail to maintain the correct trajectory of the seed bone. The force of the muscle across the metatarsophalangeal joint becomes the force that deforms the bunion.
Several other factors are also involved in bunion formation, including 1) flat feet, 2) laxity of the 1st metatarsocuneiform joint, 3) the relationship between the morphology of the 1st metatarsal head and the proximal phalanx, and 4) lesions of the medial joint capsule.
Flatfoot and bunion
Flat feet can cause bunions due to forefoot abduction, which causes an increase in nonphysiological stress on the medial side of the metatarsal aspect of the bunion when lifting the heel. The correlation between flat feet and bunions is controversial. Some authors have suggested that patients with flat feet are more likely to develop bunions than those with normal arches. But other people’s studies do not support this idea. This series of controversies are Level III to V evidence criteria, i.e., Level I evidence, is not sufficient to decide right from wrong on the issue of flat feet versus bunions.
1st metatarsocuneiform joint laxity
Mobility of the 1st metatarsocuneiform joint (TMT) can be observed in the sagittal or cross-sectional plane. The prevalence of medial column hypermobility in bunion patients remains controversial. Theoretically, laxity can cause bunions to occur in two ways. First, dorsal subluxation of the 1st metatarsal beyond the physiological range can cause a flatfoot-like morphology, increasing forefoot abduction and causing nonphysiological weight bearing on the medial side of the bunion during heel lift. Second, a more than physiologic range of medial subluxation of the 1st metatarsal increases the angle between the 1st and 2nd metatarsals and promotes the appearance of metatarsal inversion. The foot and ankle surgeon still holds a view, popularized by Morton, that 1st metatarsal cuneiform joint laxity or poor stability of the medial column of the foot is responsible for the appearance of bunions and causes pain, and Lapidus himself supports this view and proposes surgical treatment with 1st metatarsal cuneiform joint fusion. However, this theory is convincing, but there is no evidence to support such a correlation, and in fact, other researchers have found that 1st metatarsal cuneiform joint laxity is not directly associated with bunions. There is insufficient evidence (Level Ⅲ to V) and no positive or negative studies to determine the relationship between 1st metatarsophalangeal joint laxity and bunion (Level I).
Characteristics of the 1st metatarsal head
Morphology
A “square” or flat 1st metatarsophalangeal joint resists the forces of valgus and limits the development of bunions; in contrast, a rounded or concentric metatarsophalangeal joint is prone to bunions when valgus stresses continue to be applied to the bunion. To the best of our knowledge, it remains to be seen whether the shape of the metatarsal head contributes to the bunion, and there is no evidence to support a correlation between metatarsal head shape and bunion.
Distal metatarsal articular surface angle (DMAA)
There may be a situation in which the 1st metatarsal and proximal phalangeal bunion joints are aligned and symmetrical, indicating a congenital predisposition to bunion in patients. richardson et al. documented that the DMAA in bunion patients ranged from 6.3 degrees to 18 degrees; an increase in this angle was associated with an increased propensity to bunion. coughlin added that the DMAA was greater in bunions in adolescents younger than 10 years of age and greater than in adolescent looking patients over the age of 10. Although Richardson suggested that DMAA can be accurately measured on x-ray, other researchers have found variable interobserver results for the measurements.
Integrity of the medial joint capsule
Recently, Uchiyama et al. demonstrated in a cadaveric model that bunion feet have a different collagen fibrous tissue structure compared to normal feet. This finding may be related to repeated abnormal stresses in this part of the joint capsule, such that patients with rheumatoid arthritis may have an increased chance of developing bunions.
Clinical presentation
Medical history
Not all patients with bunions are symptomatic. In addition to the obvious cosmetic deformity, patients will have pain caused by shoe wear, especially when wearing pointed shoes. Common complaints include pain at the medial prominence and pain with movement of the 1st metatarsophalangeal joint. There may also be pain in the 2nd metatarsophalangeal joint, which may be located under the 2nd metatarsal head, and sometimes the 2nd toe is impinged by the bunion. To determine the pain associated with the bunion, the physician should be aware of the shoe restrictions and the limitation of motion caused by the deformity.
Physical examination
The severity of the bunion deformity, as well as the degree of flatfoot, is examined under weight. The shoe fit is observed, and the physician should note the contour of the patient’s foot in comparison to the contour of the shoe. In the patient’s sitting position, check for medial pain, 1st metatarsophalangeal joint movement, and 1st metatarsocuneiform joint laxity. Restricted movement of the 1st metatarsophalangeal joint, possibly with friction sounds, should alert the patient to possible degeneration of the 1st metatarsophalangeal joint.
There is no clear definition of normal 1st metatarsocuneiform joint mobility, and although there are many ways to examine 1st metatarsocuneiform joint mobility, hypermobility of the 1st metatarsal row is a controversial finding and difficult to diagnose. the Klaue meter can be used to measure 1st metatarsal row mobility, but it is not particularly useful in the outpatient setting. The clinical examination, which cannot be adequately performed for TMT, may only examine the mobility of the medial metatarsal row. The physician examines the 2nd metatarsophalangeal joint for synovitis, excessive metatarsal weight bearing, or 2nd toe deformity, which are also often associated with bunions.
Imaging
Proper examination of bunions requires weight-bearing frontal and lateral full foot x-rays. The angles are measured on these films, and these angular relationships determine the degree of bone and joint deformity in the bunion. Other conditions such as instability, arthrosis or poor alignment of joints in other parts of the foot, or signs of vascular, neurological or systemic disease should also be noted. The oblique position of the foot can assist in examining these, but it is not used to measure parameters such as angulation and therefore is not routinely taken. A weight-bearing seed bone image can be helpful in preoperative planning. The seed bone can appear to be displaced laterally in the weight-bearing orthostatic position, whereas the normal foot seed bone is located within the corresponding articular surface.
Imaging measurements in bunion patients
The parameters of the bunion deformity in the orthotropic position can help to have a basic determination of the deformity. The bunion angle (HVA), defined as the angle between the axis of the 1st metatarsal stem and the axis of the proximal phalanx, is used to indicate the degree of deformity of the 1st metatarsophalangeal joint. Some authors consider the maximum limit of the normal bunion angle to be 15 degrees. The intermetatarsal interval angle (IMA), refers to the angle formed by the axis of the 1st and 2nd metatarsal trunks. This angle represents the degree of inversion of the metatarsals. The upper limit of normal is 9 degrees. Interphalangeal joint angle, the angle formed between the distal and proximal phalangeal axes of the bunion. The angle represents the degree of interphalangeal valgus (HVI) of the bunion. The upper limit of normal is 10 degrees. Distal articular surface angle (DMAA) evaluates the angular relationship between the articular surface of the metatarsal head and the 1st metatarsal trunk. The upper limit of normal is 10 degrees. It is noted in the literature that the reliability of preoperative observer multiple measurements versus interobserver measurements of the HVA and IMA angles is very good (less than 5 degrees, within the 95% confidence interval), whereas the DMAA angle is more difficult to determine and less reliable.
Suggesting the presence of the so-called laxity of the radiographic measurements
Hyperplasia of the 2nd metatarsal trunk, medial orientation of the 1st metatarsal cuneiform joint, and tilting of the 1st metatarsal cuneiform joint are all considered to be indirectly indicative of hypermobility of the 1st metatarsal row. Hyperplasia of the 2nd metatarsal tuberosity, especially in the medial cortex, is a sign of laxity of the 1st metatarsal row. There are no studies to demonstrate that imaging changes in the 2nd metatarsal are associated with hyperactivity, however, one study found a marginal correlation between IMA and TMT joint dorsal mobility in patients with bunions. The medial orientation of the 1st metatarsocuneiform joint was also considered to be an indication of overactivity, but Brage et al. demonstrated that changing the direction of ray projection relative to the ground at the time of filming can cause changes in the measurement of the degree of tilt of the 1st metatarsocuneiform joint. Based on this finding, Brage et al. concluded that 1st metatarsal cuneiform joint tilt is not a reliable indicator for the decision to use 1st metatarsal cuneiform joint fusion for bunions. Another recent report found that patients with moderate to severe bunions can present with significant dorsal displacement and dorsiflexion of the 1st metatarsal cuneiform joint. However, the presence of a defective area on the metatarsal side of the metatarsocuneiform joint is related to the angle of projection to and cannot be considered a sign of hyperactivity. Today, there are no studies that indicate the presence of clinical manifestations of TMT laxity due to imaging abnormalities.
Imaging-related physical findings
Thordarson et al. examined 285 women with a mean age of 49 years who were about to undergo bunion surgery. The AAOS foot data summary questionnaire was used. Preoperative imaging data (HVA and IMA) were used to perform patient grouping. Comparisons by age grouping were collected using the SF-36 scale and compared to normal individuals. Overall foot and ankle scores and shoe comfort scores were compared with the normal population. Preoperative severity was correlated with the underlying scores. Body pain scores were significantly higher in bunion patients than in the normal population, and foot and ankle scores were significantly lower than normal with respect to shoe comfort scores. This study also found that the body pain scores from the SF-36 scale were sensitive to the pain and injury suffered by the patients undergoing bunion surgery. However, preoperative deformity severity did not correlate with the scores.
Severity
Imaging measures of HVA and IMA can define the degree of bunion deformity. These results are often used by surgeons to select a different surgical procedure. In the literature, bunions are defined as mild, moderate, and severe. The HVA in the grading is relatively consistent (mild, less than 30 degrees; moderate, 30 to 40 degrees; and severe, greater than 40 degrees), whereas there is variation in the IMA grading (mild, less than 10 or 15 degrees; moderate, 10 to 15 degrees; and severe, greater than 15 or 20 degrees). We believe that these measures are rather arbitrary in terms of grading, and recently, there is no evidence to support that absolute imaging measures can be used to make definitions of bunion severity.
Non-surgical treatment
Non-surgical treatment of bunions can provide symptomatic relief and avoid causing complications to arise with surgical treatment. To ensure that non-surgical treatment of bunions is targeted, patients need to determine what the patient’s unique complaints are. Pain is usually not the primary symptom, but rather aesthetic problems or difficulty wearing shoes are often the primary complaints. Because of the time required to recover from bunion surgery and the potential for complications, surgical treatment is not always necessary.
Pain can be relieved by changing shoes or changing the way you move. Wearing a pair of shoes with a wide foreshortening can be effective in reducing pain, and thick padding on the medial bony prominence or modifying the width of the medial side of the shoe can also be effective. However, non-surgical treatment cannot change the bunion deformity; only successful surgery can improve functional problems. A randomized controlled trial studied 209 patients with symptomatic bunions treated in four different Finnish community hospitals. Follow-up was a minimum of 12 months and found that braces provided short-term relief and that surgical treatment of bunions resulted in better postoperative foot function and higher patient satisfaction than with braces. Better functionality and higher patient satisfaction after surgical correction suggest that the natural course of symptomatic bunions is not a natural remission process (level I standard evidence). Although this prospective, randomized study demonstrates the benefits of surgical versus nonsurgical treatment, this single trial is not sufficient to support the statement that corrective surgical treatment is definitely recommendable over nonsurgical treatment modalities (level I confidence level).
Analysis and interpretation of follow-up results
The focus of attention on outcomes of most orthopedic bunion surgery has been dominated by operator perceptions rather than by patient perceptions. thordarson et al. noted that patient opinions of treatment outcomes were usually satisfactory, qualified satisfactory, and unsatisfactory. the goal of the AOFAS score is standardization of outcome data, but it remains a physician-driven scale. Its validity for hindfoot scoring has been called into question, and the shortcomings of forefoot scoring have also emerged. This shortcoming is not only specific to the AOFAS system. A recent meta-analysis of foot and ankle surgical outcomes by Button and Pinney concluded that none of the 49 grading systems that rate a patient’s foot and ankle status are reliable, valid, and sensitive to the true picture.The outcome scoring system that AOFAS members have worked so hard to create is a clinical scoring system that lacks an adequate component for quality of life assessment. SooHoo et al. demonstrated that the sensitivity of the foot and ankle scoring system was higher than that of the SF-36. However, for postoperative foot and ankle surgery, it was close to the results of the AOFAS and the Foot Function Rating Scale in terms of sensitivity levels for the evaluation of the two subscales of physical pain and local body evaluation. This points to the urgency of establishing a validated outcome scale that includes patient evaluation after bunion surgery.
The first study focusing on patient experience after bunion surgery was conducted by Thordarson et al. using the AAOS Lower Extremity Follow-up Data Collection Questionnaire and the Foot and Ankle Follow-up Data Collection Questionnaire. 311 patients, following bunion surgery by members of the AOFAS, were scored on the validated Lower Extremity Scale SF-36, which showed excellent improvements in satisfaction, pain, and function. Further to more accurately determine the outcome of bunion surgery, the AOFAS bunion-metatarsophalangeal-interphalangeal joint score should be prospectively performed preoperatively. Postoperative data collection can cause misjudgment of preoperative outcomes and overestimate treatment outcomes.
Recently, Thordarson et al. surveyed 285 women, mean age 49 years, who were about to undergo bunion surgery. This time, they again used the validated AAOS foot-specific outcome data collection questionnaire. HVA and IMA in preoperative images were grouped by angular size. Age grouping was performed based on SF-36 data and compared to SF-36 in the normal population. The overall foot and ankle scores, shoe comfort scores, were also compared with the normal population. The degree of preoperative deformity was standardized. Physical pain scores were worse than the normal population in all bunion patients, and overall foot and ankle scores and shoe comfort scores were significantly lower than the normal population. This study found that when testing patients requiring surgical treatment for bunions, the SF-36 body pain scores were sensitive to the pain experienced by the patient preoperatively. Preoperative radiographic measurements to grade the severity of the deformity did not correlate with any scoring system.
Thordarson et al. went on to report the outcome scores of these patients and the AOFAS bunion score used to conduct a study comparing the outcomes of three different bunion surgeries, the three procedures being the modified McBride, the distal Chevron osteotomy, and the Lapidus procedure. The AAOS lower extremity scores were also significantly higher for overall foot and ankle scores, shoe comfort, physical fitness, pain, patient satisfaction, and symptom scores. The degree of preoperative deformity, the degree of postoperative deformity, and the amount of corrected deformity did not correlate with any of the scores, and surgical technique had no effect on postoperative outcomes.
Analysis and interpretation of bunion x-ray measurements
The reliability of interobserver versus multiple observer measurements was reliable for HVA and IMA (<5 degrees, 95% confidence interval), but imaging measurements of the distal metatarsophalangeal articular angle (DMAA) were less reliable and became diagnostically difficult. in the cadaveric study conducted by Vittetoe et al, the observer's own measurements of the DMAA angle had small errors, whereas when interobserver measurements were made, the reliability was Thordarson et al. reported that after bunion surgery, the osteotomy changed the marker points of the anatomy where measurements were made preoperatively, and the imaging presentation was inconsistent with the patient's functional performance. resch et al. also reported that the results of a complete bunion should be based on clinical examination rather than radiographic measurements. When interpreting the literature, the reader should be aware that the higher preoperative measurement reliability of HVA and IMA is often compromised and therefore not used for the interpretation of postoperative imaging findings.
Some authors have also found that different methods of drawing lines and measuring angles in imaging measurements also contribute to differences in results, especially when x-ray measurements are performed after the 1st metatarsal osteotomy.Schneider et al. compared 5 measurement methods and concluded that the method documented by Miller (centered on the head of the 1st metatarsal to the center of the base of the 1st metatarsal) had the most significant reduction in interobserver variability and observer error.