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Bunions: their origin and treatment.

Introduction

A bunion is where the big toe tilts over towards the smaller toes and a bony lump appears on the inside of the foot (BOFFS 2007). Sometimes a soft fluid swelling develops over the bony lump. The bony lump is the end of the 'knuckle bone' of the big toe which becomes exposed as the toe tilts out of place. A bunion may be extremely painful or unsightly. Bunions tend to run in families (BOFFS 2007), however, the connection may be that bunions are more common in people with unusually flexible joints and it is this fact that is thought to be hereditary (Table 1).

Bunions explained

The function of the toes, especially the big toe, is to help us balance and to propel us forward during walking or running. The 14 bones of the toes are among the smallest in the body and, not surprisingly, they can and often do go wrong (Society of Chiropodists and Podiatrists 2006). Figure 1 shows the normal anatomy of the foot. What most people call a bunion is actually known as 'hallux valgus' and is illustrated in Figure 2. Hallux valgus refers to a condition where the big (great) toe is angled excessively towards the second toe. A bunion is a symptom of that deformity. The word 'bunion' actually refers to the bony prominence on the side of the big toe. This can form a large sac of fluid and can become inflamed and sore. While some people have massive bunions with little pain but difficulty with footwear, others have small bunions which can be extremely painful. However, once the big toe leans towards the second toe, the tendons no longer pull the toe into a straight line and problems may become progressively worse.

[FIGURE 1 OMITTED]

The term hallux valgus (sometimes known as hallux abducto valgus) refers therefore to 'an enlargement of bone or tissue around the metatarsal phalangeal joint at the base of the big toe' (Society of Chiropodists and Podiatrists 2006). Hallux = great toe; Abducto = abnormal drifting or inward leaning of the great toe towards the second toe; Valgus = abnormal rotation.

Aetiology

No single cause has been shown to produce bunions. However, what is known is that shoes can exacerbate the problem--although bunions do occur in societies that don't wear them. Certain theories surround bunions. One of which is that bunions are caused through a type of repetitive strain injury (RSI). Although this theory is unproven, one argument is that because the foot wasn't designed to constantly walk on a level surface, the ball of the toe is slightly lower than the rest of the foot (Society of Chiropodists and Podiatrists 2006). This means that when the foot meets the ground the ball of the big toe is pushed up and, as the big toe joint can't bend as well as it was designed to, the foot rolls slightly over to the side. Another argument is that if a person's mid tarsal joint tends to move from side to side more than it does up and down, the arch in the foot collapses as the foot rolls in leading to a tendency to develop bunions (Society of Chiropodists and Podiatrists 2006). The most frequent causes of bunions are shown in Table 2.

[FIGURE 2 OMITTED]

The condition may then require surgery to either correct the deformity and/or alleviate pain. A systematic review of interventions for bunions has shown little evidence that the use of othoses or nocturnal splints result in an improvement in outcomes when compared to surgical interventions such as osteotomies (Ferrari et al 2004). Surgery may be classed under the umbrella heading of 'bunionectomy'. However, there are actually around 130 different procedures which fall in this category. The type of surgical procedure performed will depend on the severity of the bunion.

Anatomy

The normal foot is a mobile framework of individual bones of correct conformation that are aligned for maximal structural stability and functional efficiency. The forefoot is probably the part of the body that is exposed to the heaviest mechanical stresses. Normal configuration of the foot is one in which the long axis of the phalanges closely parallel the long axis of their respective metatarsals as shown in Figure 1. In the normal foot the angulation of the first metatarsal against the second metatarsal is usually 8-12[degrees] (Trewben 2007).

The first metatarsal is the most medial of the five miniature long bones of the metatarsus of the foot. It articulates with the medial cuneiform and the second metatarsal base proximally and with the base of the proximal phalanx of the hallux distally. It is the shortest and stoutest of the metatarsals. It is composed of a base proximally, a head distally with intervening shaft.

Surgical options fall into several broad categories ranging from distal soft-tissue reconstruction, to phalangeal/metatarsal osteotomies (Figures 3 and 4), to arthrodesis and resection.

Surgical treatment of bunions (hallux valgus)

Distal soft tissue reconstruction A mild deformity may be correctable by distal soft tissue reconstruction. This involves the release of the deforming structures to balance the toe on the lateral side through a small longitudinal incision in the first webspace. This procedure is intended to realign the toe providing the anatomy is accepting. It is a procedure that is seldom used alone, usually being combined with a bony procedure (Society of Chiropodists and Podiatrists 2006).

[FIGURE 3 OMITTED]

[FIGURE 4 OMITTED]

Akin osteotomy

The Akin osteotomy is a procedure reserved for the correction of a deformity in the proximal phalanx in cases of mild hallux valgus (Laughlin 2007). In many deformities there is a need to straighten the big toe as well as the position of the first metatarsal, and involves the removal of a small wedge of bone from the base of the big toe. Kirschner wires or sutures are used to fix the osteotomy, taking care to check for correct rotation. This procedure may be carried out alone or combined with a first metatarsal osteotomy to gain correct alignment.

In hallux valgus deformity the first metatarsal head shifts medially allowing lateral drift of the sesamoid complex into the interspace. This is a progressive degeneration.

Mitchell and Chevron's osteotomies

The neck is a common site for distal metatarsal osteotomies such as Mitchell and Chevron's osteotomies (Society of Chiropodists and Podiatrists 2006). These procedures allow for correction of moderate hallux valgus deformities only. The shaft of the first metatarsal is the site of more severe hallux valgus deformities and requires procedures such as a Scarf osteotomy for repair.

Mitchell's Osteotomy is a distal osteotomy of the first metatarsal for individuals with mild deformities. This involves making a double cut through the metatarsal neck leaving a step to hitch onto the metatarsal head to be held in place using a suture through drill holes (Society of Chiropodists and Podiatrists 2006). Mitchell's osteotomy has been shown to result in less shortening of the first metatarsal and an improved overall status long term (20 years after surgery) when compared to a Wilson osteotomy (Madjaveric et al 2006).

Chevron osteotomy

A Chevron osteotomy is a commonly used distal osteotomy which involves cutting the bone towards the end of the first metatarsal before fixing it back into a straighter position. In this case the osteotomy is a 'V' shape, the angle of which may vary. The use of locking plates may improve alignment and improve stability of the proximal metatarsal after chevron osteotomy (Gallentine et al 2007).

Scarf osteotomy

The Scarf osteotomy is similar to a chevron but more bone is cut allowing for slightly more correction of a deformity. The distal articular surface of the first metatarsal is a common site of osteoarthritis, causing hallux rigidus. The blood supply to the head of the toe must be respected when performing distal metatarsal osteotomy for hallux valgus as avascular necrosis may occur (Society of Chiropodists and Podiatrists 2006).

Keller's arthroplasty

Keller's arthroplasty involves removing the bone at the base of the big toe and essentially removing half of the big toe joint. This procedure can leave the toe a little bit unstable and is mainly used for older people suffering from arthritis. This procedure accomplishes only mild correction whilst decompressing the metatarsal phlangeal joint and allowing for quick healing (Society of Chiropodists and Podiatrists 2006).

There is no evidence to suggest that any single form of osteotomy is better than any other (Ferrari et al 2004).

Due to the deviation of the hallux the soft tissues of the great toe undergo progressive accommodative shortening and lengthening of the lateral and medial sides. While the muscular attachments do not change, they have their momentary forces changed due to the changed position of the bones against each other. This leads to a significant overload of the muscles on the lateral side, which in turn obtain mechanical advantage and so further contribute to the deformity if left untreated (Society of Chiropodists and Podiatrists 2006).

Postoperative management

It can be seen now that what may traditionally have been seen as a rather simple procedure is actually very technical and individually tailored to meet the patient's needs. Bunion surgery is very specialised and intricate and requires a great deal of care and understanding from all members of the healthcare team. Frequently patients will undergo multiple foot procedures simultaneously and these need to be detailed on the operative list. The scrub nurse must be able to interpret the theatre list accurately in order to provide the correct instrumentation for the procedure to be carried out and allow for the smooth flow of the theatre session, and the surgeon and anaesthetist must communicate effectively to ensure the patient receives the most appropriate anaesthetic (Russon & Thomas 2007).

There is no standard format for the postoperative management of this patient group, just as there is no standard format for the operative management. In some cases podiatrists are able to perform simple procedures using local anaesthetics, while in other cases podiatric orthopaedic surgeons will need to admit their patients into hospital. Most surgery is performed in the day case setting. However, some surgeons prefer to have their patients undergo an overnight stay to allow for administration of both pain relief and intravenous antibiotics. Patients may experience moderate to severe pain after surgery and should be advised to continue analgesia as directed and for as long as required (Townsend & Cox 2007).

Postoperatively no weight bearing is allowed for four to six weeks and a foot wedge should be used. The patient may also be advised to wear a special shoe, cast or splint to keep the area stable. Swelling may be managed by elevating the foot during regular rest periods.

Conclusion

The evidence for surgical interventions in the treatment for hallux valgus is stonger than that for orthoses or night splints. No single form of osteotomy has been shown to produce superior results to any other. There is no such procedure as a simple bunionectomy. The degree of angulation of the first metatarsal against the second metatarsal will influence the surgeon's choice of over 130 corrective procedures. Wires, screws and plates may be implanted to maintain the bony correction. The perioperative management of patients undergoing bunion surgery varies greatly, but the procedure is usually performed in the day case setting with discharge on the same day.

REFERENCES

Ferrari J, Higgins JT, Prior TD 2000 Interventions for treating hallux valgus (abductovalgus) and bunions The Cochrane Database of Systematic Reviews Art. No.: CD000964. DOI: 10.1002/14651858.CD000964.pub2

Gallentine JW, Deorio JK, Deorio MJ 2007 Bunion surgery using locking-plate fixation of proximal metatarsal chevron osteotomies Foot and Ankle International 28 (3) 361-368

Laughlin RT 2007 BunionAvailable from: http://www.emedicine.com/orthoped/topic467.htm [Accessed 17 May 2007]

Madjarevic M, Kolundzic R, Matek D et al 2006 Mitchell and Wilson metatarsal osteotomies for the treatment of hallux valgus: comparison of outsomes two decades after the surgery Foot and Ankle International 27 (11) 877-882

Russon K, Thomas A 2007 Anaesthesia for day surgery Journal of Perioperative Practice 17 (7) 302-307

Society of Chiropodists and Podiatrists 2006 Bunion/Bunions/Toe DeformitiesAvailable from: http://www.feetforlife.org/cgi-bin/item.cgi?id=68&d=96&h=24&f=46 [Accessed 17 May 2007]

Townsend R, Cox F 2007 Standardised analgesia packs after day case orthopaedic surgery Journal of Perioperative Practice 17 (7) 340-346

Trewben B 2007 Normal versus pathoogic anatomy of Hallux Abducto ValgusAvailable from: http://www.podiatry.curtin.edu.au/encyclopedia/ hallux_abducto_valgus/hallux_abducto_valgus.html [Accessed 17 May 2007]

Members can search all issues of the BJPN/JPP published since 1998 and download articles free of charge at www.afpp.org.uk. Access is also available to non-members who pay a small fee for each article download.

Kathryn Kitson

BSc(Hons)

Team Leader for Orthopaedics and Trauma, Bradford Royal Infirmary
Table 1 Some facts about bunions

* Bunions are more common in women
than in men with a ratio of 4:1
(Trewben 2007).

* Bunions do occur in cultures where shoes
are not worn, but they are far less
common.

* The wearing of high heels or shoes where
the big toe is squeezed into the end of the
shoe can be a contributory factor.

* The big toe may then displace the second
toe or cause pain under the ball of the
foot as the other toes move to
accommodate the extra width of the foot
in shoes.

Table 2 Frequent causes of bunions

* Repetitive strain injury.

* III-fitting footwear (this may the most
important causative factor).

* Family history of bunions.

* Abnormal foot function, excessive
pronation (rolling of the foot and ankle
joint when walking).

* Rheumatoid or osteoporosis.

* Genetic and neuromuscular disease.

* One leg being shorter than the other
(the longer leg is more inclined to
develop a bunion).

* Weak foot ligaments.

* Trauma or injury to the feet.
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Title Annotation:DAY SURGERY: COMMON PROCEDURES
Author:Kitson, Kathryn
Publication:Journal of Perioperative Practice
Article Type:Clinical report
Geographic Code:4EUUK
Date:Jul 1, 2007
Words:2298
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