Tuesday, November 11, 2008
Hallux valgus deformity (bunion)
INTRODUCTION — Valgus malformation of the great toe, commonly known as a bunion, is a very common and potentially painful and debilitating condition of unclear etiology. This topic review will provide an overview of the relevant anatomy, pathophysiology, diagnosis, and management of hallux valgus. Toe and foot injuries are discussed elsewhere. (See "Toe fractures" and see "Metatarsal shaft fractures").
RELEVANT ANATOMY AND BIOMECHANICS
Basic forefoot anatomy — By convention, toes and their respective metatarsals are numbered from one (great toe) through five (little toe). The great toe has two phalanges, while the second through fifth toes typically have three (show figure 1, show figure 2 and show figure 3). Tendons and ligaments insert at the bases of each phalanx. The digital artery and nerve pass together along each side of each toe deep to the plantar surface.
Definitions Hallux valgus deformity — This deformity is defined as a lateral deviation of the hallux (great toe) on the first metatarsal (show figure 4). The deviation of the hallux occurs primarily in the transverse plane. The deformity often also involves rotation of the toe in the frontal plane causing the nail to face medially (ie, pronation). These two deviations have led to the use of different terms to describe the deformity. In orthopedic texts, it is often called "hallux valgus" (HV) whereas many podiatry texts prefer the term "hallux abductovalgus (HAV)." The public is more familiar with the expression "bunion." Hallux abductus (or hallux valgus) angle — The angle created by the bisection of the longitudinal axis of the hallux and the longitudinal axis of the first metatarsal (show figure 4) (show radiograph 1). Historically an HA angle of greater than 15 degrees was considered abnormal, but such deformities are not always symptomatic, and some cases of an HA angle greater than 15 degrees occur naturally due to the shape of the articular surfaces involved [1,2]. Contemporary research suggests an HA angle of 20 degrees or greater is abnormal . Intermetatarsal (IM) angle — The angle determined by the bisection of the longitudinal axes of the first and second metatarsals (show figure 4). An IM angle less than 9 degrees is considered normal. Ray — The forefoot consists of five longitudinal projections, called rays, which are comprised of the metatarsal and its respective phalanges, and the bones aligned with and proximal to the metatarsal, such as the cuneiforms or cuboid bones. Hallux valgus involves the first ray.
First ray anatomy — No muscles originate on the first metatarsal and insert into the phalanx to directly stabilize the first metatarsophalangeal (MTP) joint. The abductor and adductor hallucis muscles pass medially and laterally to the MTP joint respectively, but they are located nearer to the plantar surface (show figure 5). Thus, any force pushing the proximal phalanx laterally, or the metatarsal head medially, is relatively unrestrained and can create a valgus deformity.
The first metatarsal is held in alignment by a splinting action of the abductor hallucis muscle medially and by the lateral pull of the peroneus longus acting at the base of the metatarsal . Movement at the first MTP joint in the transverse plane is prevented by collateral ligaments running from the metatarsal epicondyles, distally and plantarly, to the proximal phalanx.
Pathophysiology of HV deformity — The metatarsocuneiform joint has a sinusoidal curve allowing medial-dorsal and plantar-lateral movements. Increased pressure under the head of the first metatarsal (for example, due to increased subtalar pronation or a congenital plantar-flexed first ray) will force the metatarsal to move medial-dorsally. This movement increases the HA and IM angles and places the metatarsal more medial relative to its proximal phalanx. As muscle action stabilizes the joint during gait, pressure from the proximal phalanx on the lateral aspect of the metatarsal head pushes the metatarsal more medially, further increasing the HA angle.
As the first metatarsal moves medially and the hallux moves laterally, the medial capsule and medial collateral ligament come under chronic strain and eventually rupture. The medial movement of the metatarsal forces the abductor hallucis muscle beneath the metatarsal. From this position it acts solely as a plantar-flexor of the proximal phalanx, thereby contributing to the valgus rotation seen with HV deformity. Eventually, without medial stabilizing structures, the lateral joint capsule and collateral ligaments tighten and the adductor hallucis muscle acts unopposed, exacerbating the deformity .
Since not all cases of HV deformity become severe, there may be a threshold up to which the forces deforming the joint can be opposed by other anatomic structures. When forces greater than the threshold occur, the joint becomes deformed. It is possible that such progression occurs rapidly rather than worsening steadily over several years [1,2,6].
PREVALENCE — Many studies have tried to determine the prevalence of hallux valgus (HV) deformity. Approximately 4 to 44 percent of women and 2 to 22 percent of men have HV deformity, depending upon the method of measurement and the population studied [7-14]. The prevalence is greater among shod compared with barefoot populations, although the condition is still found twice as often in women than men in non-shod populations [15-17].
ETIOLOGY — Many theories have been proposed, but the precise etiology of hallux valgus (HV) deformity is unknown . Most likely, HV deformity is multifactorial in origin and includes such factors as: abnormal foot mechanics affecting the first ray [5,19-23], abnormal first metatarsophalangeal anatomy [24-27], joint hypermobility [28,29], and genetic influences . HV is also associated with conditions such as inflammatory joint disease [30-32].
Since HV deformity occurs primarily in shod populations, affecting women in particular, poor footwear has frequently been cited as a cause. The fact that some women wear footwear that compresses their toes significantly without detrimental effects, while some men suffer from marked HV deformity despite the use of sensible footwear, leads many to think that footwear probably exacerbates underlying bony or mechanical abnormalities rather than acting as a primary factor.
DIAGNOSIS — Although hallux valgus (HV) is easily recognized by clinical examination, x-rays may be necessary to determine the presence of damage to the articular surfaces of the first metatarsophalangeal (MTP) joint. Surgeons use radiographs to assess the severity of the deformity and select the appropriate procedure.
Associated findings — HV can lead to a number of painful complications in or around the first MTP joint, including [33-35]: Inflammation of a medial bursa protecting the joint (most common) Degeneration of the crista on the plantar surface of the metatarsal head, caused by erosion as the metatarsal moves over the sesamoids Entrapment of the medial dorsal cutaneous nerve as it passes through the enlarged bunion area Hammertoe deformity of the second toe, caused by destabilizing pressure from the laterally deviated great toe Central metatarsalgia, caused by the patient's chronic shifting of weight from an unstable first ray onto the central rays Degeneration of the cartilage covering the metatarsal head Synovitis of the MTP joint
Hyperkeratosis may also occur as a result of altered weight-bearing forces and can cause marked discomfort. Assessment of HV to determine the factors causing patient discomfort is important, as it will help to determine the appropriate treatment.
TREATMENT — Hundreds of studies have been published assessing numerous conservative and surgical treatments for hallux valgus (HV) deformity. Overall, there is little evidence that conservative treatments are useful. Nevertheless, we agree with the American College of Foot and Ankle Surgeons and suggest that patients make use of conservative therapies before surgical referral is made .
Patients with severe pain or dysfunction and those whose symptoms do not improve under a conservative regimen should be referred to a foot surgeon.
Conservative management — A systematic review identified only three randomized trials conducted on conservative treatments in adults . Nevertheless, we suggest the following nonoperative treatments be considered to alleviate symptoms and possibly to help prevent progression of HV deformity : Shoe modification: wide, low-heeled shoes, or specially altered shoes with increased medial pocket for the first metatarsophalangeal (MTP) joint to minimize deforming forces Orthoses to improve support and alignment Night splinting to improve toe alignment Stretching to maintain joint mobility Medial bunion pads to prevent irritation Ice applied after activity to reduce inflammation Analgesics: acetaminophen or NSAIDs
Orthoses — In the treatment of HV deformity, orthoses are used to improve foot mechanics (eg, reducing abnormal subtalar joint pronation) and to prevent abnormal forces from acting on the first ray complex. It is hoped that orthoses might prevent deterioration of the HV angle and relieve pain by improving joint function. Orthoses need to be worn in a well-fitting, low-heeled, fastening shoe, and this type of shoe may itself influence joint position and discomfort.
In subjects with rheumatoid arthritis (RA), orthoses have been shown to prevent progression of HV deformity compared with controls with RA and placebo orthoses . The Hallux abductus (HA) angle progressed in 10 percent of the treatment group compared with 25 percent of the control group (adjusted odds ratio = 0.27) . In the same study, however, measures of pain, disability, and function of the foot showed little difference between patients wearing orthoses and those wearing placebo devices. Furthermore, the majority of patients in the trial were male, and these results may not apply to women, who comprise the majority of patients with HV deformity.
When orthoses were compared with no treatment in patients with painful, mild-to-moderate HV deformity, patients wearing orthoses reported improved pain scores after six months, but these improvements were not maintained thereafter . At one year, only the global assessment score remained better in the orthosis group (46 percent better than one year ago versus 24 percent; 11 percent worse than one year ago versus 34 percent). In the same study, surgery (chevron osteotomy) outperformed orthoses for all outcomes. The study did not evaluate HA angle progression.
Splinting — Splints can be used to place the toe in a corrected position in the hope of enabling soft tissue adaptation and delaying rupture of the medial joint capsule and collateral ligament. The most common devices used are night splints, which realign the hallux while non-weight-bearing (show picture 1). Wedges placed between the first and second toe and attached with adhesive strapping can also used.
Night splints were ineffective in reducing pain associated with HV deformity in one small randomized trial . Progression of the deformity did not occur in the treatment or the control group over the six-month trial duration. Night splints were more effective in reducing deformity and pain than a toe separator, but they were less effective than exercises, in one very small study . However, the mean decrease in HA angle was approximately 2 degrees, which was within the range of measurement error.
Other — Marigold ointment was reported to be effective in reducing pain, soft tissue swelling, and the HA angle when applied to the bunion area over an eight-week period .
Surgery — Referral for surgical repair is based primarily upon patient symptoms (eg, pain, difficulty with ambulation); neither clinical nor radiographic appearance play a significant role. Patients with severe pain or dysfunction and those whose symptoms do not improve under a conservative treatment regimen should be referred to a foot surgeon. (See "Conservative management" above).
Approximately 150 surgical procedures for the correction of HV deformity have been described. All involve one of the following basic approaches: Fusing the metatarsophalangeal (MTP) joint or the metatarsocuneiform joint in a corrected position (arthrodesis) Removing the joint or replacing the joint with an implant (arthroplasty) Cutting the first metatarsal and realigning the bone in a less adducted position (osteotomy) Removing the prominent side of the metatarsal head (bunionectomy) Mobilizing soft tissue to pull the bones into a corrected position
There are many retrospective studies but very few prospective, randomized trials evaluating these procedures. A systematic review identified 15 randomized trials concerned with surgical correction of the deformity . Although patient satisfaction with surgical correction ranges from 50 to 90 percent, the trend is toward greater satisfaction as surgical techniques have improved.
Both orthopedic and podiatric specialist foot surgeons, as well as non-specialists, perform operations to repair HV deformity. No study has compared the results of surgery based on who performed the procedure. Nevertheless, we suggest patients be referred to a foot surgery specialist with experience repairing HV deformity.
Patient satisfaction — Patient satisfaction does not appear to correlate with surgical outcome as determined by radiographic parameters (ie, HA and IM angles) . Some patients have a misapprehension that the hallux should be straight after the operation. Others may be under the mistaken impression that they will be able to fit into narrower shoes postoperatively and can be dissatisfied if this expectation is not met.
Managing patient expectations is important. Patients should understand that 10 to 25 degrees of valgus angulation is normal at the MTP joint, and that resolution of postoperative pain and swelling may require several months . Most will remain unable to fit into narrower shoes. One study found that only 2 of 52 patients could wear smaller shoes after their procedure, despite a postoperative reduction in foot width .
Arthrodesis — Fusion of the first MTP joint is rarely performed, unless there is severe degeneration of the joint and good function is unlikely to be regained were only joint position corrected. The procedure is usually reserved for older patients. Walking on a fused MTP joint alters foot mechanics during gait and can cause secondary hyperkeratoses to develop.
A study of 81 patients treated with first MTP arthrodesis reported success in relieving joint pain, improving walking distance, and improving appearance after a minimum follow-up of 24 months .
Fusion at the metatarsocuneiform joint is called the Lapidus procedure and is used when the mobility of the first ray is excessive. A study of 87 patients, found that the Lapidus procedure combined with a soft tissue correction was successful in reducing the HA and IM angles, as well as improving the American Orthopaedic Foot and Ankle Society (AOFAS) functional score . Eighty-four percent of patients considered the surgery satisfactory.
Arthroplasty — A comparison of arthrodesis with Keller's arthroplasty found that 75 percent of the arthroplasty patients were completely satisfied postoperatively, and that 88 percent experienced complete pain relief . However, 12 percent experienced worse pain after the surgery. The authors also found the response to surgery could be prolonged, with some patients needing up to 30 months before manifesting improvement. Overall, little difference in outcomes was found between the arthroplasty and arthrodesis groups.
A small study comparing distal metatarsal osteotomy with Keller's arthroplasty found larger residual HA and IM angles in the arthroplasty group, but overall satisfaction and pain relief did not differ significantly .
Osteotomy — The cut made in the bone during an osteotomy varies in shape and position, depending upon the surgical strategy. As an example, a straight cut is used in the Wilson osteotomy whereas a wedge-shaped cut is used in the chevron osteotomy. The cut may be made near the neck of the metatarsal (distal osteotomy) or near the base (proximal osteotomy). Although a greater degree of correction is possible through proximal osteotomies, these procedures require larger dissections and have higher complication rates. Generally, the surgeon tries to minimize metatarsal shortening and to maintain the metatarsal's plantar-flexed position.
The chevron osteotomy has been evaluated most often through randomized, controlled trials. A study of 209 patients comparing chevron osteotomy to treatment with orthosis and to no treatment found that osteotomy outperformed nonoperative alternatives . At 12-month follow-up, the HA and IM angles in the osteotomy group were at normal values, and 80 percent of patients were satisfied with their treatment. Nevertheless, 61.5 percent of these surgical patients still had "moderate" footwear problems, and half had experienced some pain in the previous six months. Over the 12-month follow-up period, the surgery group also had the highest costs for foot care and took the greatest number of sick days.
Although a comparison between distal metatarsal osteotomy and Keller's arthroplasty reported better radiological outcomes in the osteotomy group, patient satisfaction scores were similar . The authors commented that 60 percent of the patients were over 60 years old and that good surgical outcomes can be achieved in older patients.
Proximal osteotomy appears to be more effective at correcting both the HA and IM angles but results in a shorter metatarsal and higher complication rates . Patient satisfaction with each procedure was 97 percent.
Soft tissue procedure — No study has evaluated soft issue procedures to correct HV deformity independently. One small study compared chevron-Akin osteotomy to a distal soft tissue reconstruction-Akin osteotomy . Although the soft tissue reconstruction did not correct the HA and IM angles as well as the osteotomy alone, patient satisfaction did not differ significantly.
A larger study compared the chevron osteotomy with the chevron plus adductor tenotomy and found no significant difference in patient satisfaction and little difference in mechanical correction .
SUMMARY AND RECOMMENDATIONS — Hallux valgus (HV) deformity (ie, bunion) is a very common, potentially debilitating deformity consisting of lateral deviation of the hallux on the first metatarsal. The etiology is unknown. The deformity is more common among women and shod populations. A detailed description of the relevant anatomy, biomechanics, and pathophysiology is found above. (See "Relevant anatomy and biomechanics" above). Important aspects of diagnosis and management are summarized below. Although HV is easily recognized by clinical examination, x-rays may be necessary to determine the presence of articular damage. Neither radiographic nor clinical appearance provide the basis for surgical referral, which is determined by patient pain and disability. (See "Diagnosis" above). There is little evidence that conservative treatments are useful in the treatment of HV. Nevertheless, we suggest patients without debilitating symptoms avail themselves of conservative therapies before being referred for surgery (Grade 2C). Possible treatments include:
- Shoe modification: wide, low-heeled shoes, or specially altered shoes with increased medial pocket for first metatarsophalangeal (MTP) joint to minimize deforming forces
- Orthoses to improve support and alignment
- Night splinting to improve toe alignment
- Stretching to maintain joint mobility
- Medial bunion pads to prevent irritation
- Ice applied after activity to reduce inflammation
- Analgesics: acetaminophen or NSAIDs. (See "Conservative management" above).
We recommend patients with severe pain or dysfunction and those whose symptoms do not improve under a conservative treatment regimen be referred for surgical repair (Grade 1B). Approximately 150 surgical procedures for the correction of HV deformity have been described. Few prospective, randomized trials evaluating these procedures have been performed. Both orthopedic and podiatric specialist foot surgeons, as well as non-specialists, perform operations to repair HV deformity. Patients should be referred to a foot surgery specialist with experience repairing HV deformity. (See "Surgery" above). Managing patient expectations about surgery is important. Patients should understand that 10 to 25 degrees of valgus angulation is normal at the MTP joint, and that resolution of postoperative pain and swelling may require several months. Most patients will remain unable to fit into narrower shoes. (See "Patient satisfaction" above).
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