A recent review estimated the global prevalence of hallux valgus up to 23% in 18- to 65-year-old population and 35% in above the age of 65.
The pathogenesis of hallux valgus is complex. It is generally believed that an imbalance of the extrinsic and intrinsic muscles and the ligaments is involved. Even in a physiologically normal foot, the extensor and flexor tendons are slightly off-centre to lateral.
This is compensated by other muscles and ligaments in the foot; however, the overall forces remain balanced. This equilibrium is sensitive to internal and external influences (familial predisposition, the wearing of narrow, flexible/flatfeet, high-heeled, and pointed shoes). There is also some correlation between hypermobility of the first ray and hallux valgus.
The role of pes planus is complex. It is unlikely that it is an important initiating factor in hallux valgus but in the presence of pes planus the progression of hallux valgus is more rapid, particularly in patients with rheumatoid arthritis, collagen deficiency or a neuromuscular disorder. The presence of pes planus does not reduce the rate of success of hallux valgus surgery, however can predispose to the risk of recurrence.
Mann, Rudicel and Graves have shown that the patients present with restriction in wearing their shoes in 80%, pain over the medial eminence in 70%, cosmetic concerns in 60% and pain underneath the second metatarsal head in 40%.
Pain may also be felt in the distribution of the dorsal cutaneous nerve, due to pressure. As the deformity progresses patients may develop transfer metatarsalgia, and lesser toe deformities. There may also be an associated degenerative change in the 1st MTP joint.
Clinical symptoms include localised pain, progressively worsening deformity, lesser toe symptoms, and skin irritation due to external pressure. Symptoms do not always correspond to the extent of clinical deformity.
Always the first line of treatment. Usual modalities include accommodative footwear, soft leather shoes with extra width and depth of the toe box, which can alleviate the symptoms in many patients. A trial of orthoses is often discussed but there is little evidence to substantiate their use.
A support for the medial longitudinal arch has been shown to relieve symptoms for approximately in the short term (six months or so). Pain in the lesser toes can be alleviated with pads and toe sleeves in flexible deformities.
Surgery for hallux valgus correction is indicated in cases of failure of conservative treatment with progressive deformity, worsening pain, impaired function and development of secondary deformities in lesser toes. If transfer lesions are present, it may be necessary to wear cushioned shoes or even insoles following surgery as well.
The principal contraindication to surgery is arterial occlusive disease.
Over 150 different operations have been described for the treatment of hallux valgus. The actual choice of procedure depends on the surgeon's expertise and experience.
There have been a few randomised trials performed comparing different surgical procedures; however no robust recommendations could be concluded from these studies due to generally poor methodology and smaller number of patients. In actual fact these various techniques can hardly be randomised without taking account of the exact deformity in individual patients.
Analysis of the large number of retrospective studies with follow-up for up to 5 years shows that overall, 85% of patients are satisfied and have a good clinical result. Ten percent are less satisfied and show a less beneficial outcome, and in 5% the results of surgery are poor.
Among the complications the foremost is recurrence, which can be a result of inadequate surgical correction. The quality of wound healing cannot be precisely predicted, and the rate of wound problems is generally reported as 2% to 4%.
Soft Tissue Release
Adductor hallucis and lateral joint capsule are released allowing the sesamoids to be reduced underneath the first metatarsal head. The lateral collateral ligament is usually left intact as its release predisposes to hallux varus.
A distal soft-tissue procedure is an important part of the armamentarium of the correction of hallux valgus, but it is not the complete answer. Simple bunionectomy and capsular plication is ineffective with some studies reporting up to 41% dissatisfaction rate.
Mann and Coughlin found that a distal soft-tissue procedure in isolation reduced the HVA by 14.8° and the IMA by 5.2°, but there was an incidence of hallux varus of 11%.
A distal soft-tissue procedure showed significantly worse results in the presence of a pre-operative IMA > 15°.
Johnson et al. showed that a Chevron osteotomy resulted in a significantly greater radiological correction than an isolated distal soft-tissue procedure in patients with a mild to moderate deformity.
An Ideal Osteotomy
Important considerations for first MT osteotomy include:
1. Technically easy to undertake and reproducible.
2. The osteotomy should be stable and should not displace.
3. The length of the first metatarsal should be maintained to prevent the development of transfer metatarsalgia.
4. Dorsiflexion of the metatarsal head should be avoided.
5. The technique should be versatile so that the HVA, the IMA and the DMAA can be corrected.
6. Blood supply should be preserved in order to avoid avascular necrosis of the metatarsal head.
7. The long-term outcome should have a low recurrence
Scarf and Akin Osteotomies
Scarf osteotomy, popularised by Barouk, is a versatile diaphyseal osteotomy of the first metatarsal and is frequently used for correction of moderate to severe hallux.
The shape and length of the osteotomy offers good stability and requires fixation with two screws. It allows lateralisation of the head shaft fragment to reduce the IMA, maintains joint congruence and motion of the first MTP joint, and permits elevation or plantarisation of the metatarsal head, lengthening or shortening, and transverse plane rotation for correcting an increased DMAA.
Akin osteotomy is commonly performed, usually as an adjunct to other procedures. Multiple fixation techniques including suture, wire, screw and staple fixation have been reported. Most authors favour staple fixation, which is reported as safe and effective with a low risk for complications.
Complications of scarf osteotomies have been reported in 1.1% to 31% cases in different studies and include over-correction (5%), recurrence (10% over 10 to 15 years), non-union/delayed union (very rare), superficial and deep wound infections, metatarsalgia, plantar keratosis, post-operative first MTP joint arthritis, metatarsal fracture, metatarsal head osteonecrosis, symptomatic hardware and CRPS.
Minimal Invasive Surgery
MIS is gaining popularity with improvements in surgical equipment. The perceived benefits include smaller wound size, less soft tissue stripping, lesser stiffness, reduction in recovery time and overall morbidity, yet achieving good correction for larger deformities.
However, despite the advancements in kit design, local soft tissue complications remain a concern along with surgeon's own learning curve and limited and low level of evidence at present.
Scarf osteotomy combined with Akin osteotomy, lateral soft tissue release and medial capsular tightening has become a preferred option for hallux valgus correction.
It is a technically-demanding procedure with a learning curve, but provides an excellent primary stability and permits good reliable correction of the deformity with predictable results
Studies have shown that the clinical outcomes of the scarf osteotomy compare favourably with those of basal osteotomies (over 85% satisfaction and clinical improvement).
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