The management of bunions – an overview

The term “bunion” is derived from the latin word “bunio”, meaning a “turnip” which denotes the prominent medial eminence of the first metatarsophalangeal joint.

The term “Hallux Valgus” implies a forefoot deformity comprised of lateral deviation of the great toe with medial deviation of the metatarsal head (Fig 1) and so “hallux valgus” is just one of the causes a “bunion”.

Fig 1 - metatarsal head

Fig 1 – bilateral hallux valgus

The management of Hallux Valgus has undergone significant improvements in the last 30 years as we better understand the nature of the deformity and the biomechanical consequences of the surgery we perform.

The prevalence of Hallux Valgus is unclear. It is probably around 2% in unshod populations, but is much higher in the shoe wearing population. Women comprise the majority of that subset as they tend to wear narrow shoes with or without high heels.

The aetiology is therefore partly genetic and partly due to lifestyle factors. Some of the proposed genetic factors include:

  1. the geometry of the 1st tarsometatarsal and metatarsophalangeal joints
  2. calf tightness
  3. flatfeet
  4. hypermobile joints.

The deformity usually presents with an insidious onset well after reaching skeletal maturity. Less commonly however, it occurs during growth sometimes in the context of an underlying paediatric condition or as a result of trauma.

It is a complex deformity involving weakening of the medial capsule of the 1st MTP joint and relative translation of the sesamoid bones into the 1st intermetatarsal space.

The most often used classification system to determine surgical treatment is based on both the “hallux valgus angle” (HVA) between the 1st proximal phalanx and 1st metatarsal and the “intermetatarsal angle” (IMA) between the 1st and 2nd metatarsals.

                      HVA                IMA
Normal          <150              <90
Mild               <200              <110
Moderate     <400              <160
Severe           <500              <200
Very Severe  >500              >200

Patients may present with:

  1. Pain in the 1st MTP joint
  2. Pain over the bunion itself
  3. Difficulty with footwear
  4. Concern over the appearance
  5. Concern over progression of deformity
  6. Lesser toe problems such as 2nd toe clawing and 2nd metatarsal head prominence and pain. This is a result of the “defunctioning” of the first ray due to the hallux valgus pathophysiology.

It is important to obtain weight bearing x-rays (Fig 2) to assess the functional deformity.
There are no non operative measures that can correct the deformity. Shoes with a wider toe box can accommodate the foot and bunion splints are available to hold the toe in a corrected position if the deformity is correctable.

Fig 2 - weight bearing x-ray

 

Fig 2 – weight bearing x-ray

Operative options generally involve a combination of:

  1. Corrective ostetotomies which alter the axis of the metatarsal or proximal phalanx
  2. Corrective fusions which obliterate any joint angle
  3. Soft tissue releases which alter the angle of the MTP joint.

The decision is based on the severity of the deformity and the presence of arthritis at either the MTP or TMT joint.

The scarf osteotomy (Fig 3,4,5) involves most of the shaft of the metatarsal and is based on a carpentry concept where small “back cuts” provide some intrinsic stability to the translated bone fragments.

Fig 3 - scarf osteotomy

Fig 3 – scarf osteotomy

 

Fig 4 - scarf osteotomy

Fig 4 – scarf osteotomy

 

Fig 5 - scarf osteotomy

Fig 5 – scarf osteotomy

 

The chevron osteotomy (Fig 6,7,8) is a distal osteotomy that also provides intrinsic stability. In the x-ray shown an “Akin” osteotomy of the proximal phalanx has also been performed to improve the correction.

Fig 6 - chevron osteotomy

 

Fig 6 – chevron osteotomy

 

Fig 7 - chevron osteotomy

Fig 7 – chevron osteotomy

 

Fig 8 - chevron osteotomy

Fig 8 – chevron osteotomy

Following Hallux Valgus correction patients can often weight bear in a stiff sole open toe shoe.

They may be back to driving in 4-6 weeks.

Some of the complications to inform patients about include:

  1. Pain and swelling – this often resolves over 6 weeks but can persist for up to 12 months
  2. Failure to achieve a perfect correction
  3. Recurrence of deformity
  4. Hallux Varus – overcorrection of deformity.

Daniel GoldbloomAUTHOR | Mr Daniel Goldbloom
Mr Goldbloom is a consultant orthopaedic surgeon with a subspecialty interest in all aspects of foot and ankle surgery. He also holds public consultant posts at the Alfred Hospital and Monash Health where he enjoys teaching and being involved in complex trauma cases.
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PH | 03 9099 8866  WEB | www.orthoam.com.au

 

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