Hallux Valgus

definition
Bunion

·      medial prominence of head of 1st metatarsal

Hallux valgus

·      excessive lateral deviation of the great toe at the metatarso-phalangeal joint

·      20o is upper limit of normal

Hallux valgus syndrome

·      complex deformity of the forefoot

·      lateral deviation of the great toe is the most obvious feature

·      may include

·      pronation of the hallux

·      prominent medial eminence

·      overriding of the second toe

·      metatarsalgia

·      hammer and claw deformities of the lesser toes

epidemiology

·      two ages of presentation

·      adolescent form (present in teens)

·      adult form (peak presentation in 50s)

·      strongly familial

·      positive family history in 2/3

·      more common in females

·      F:M = 9:1 in those requiring surgery

·      true incidence in adolescence may be equal

·      usually bilateral but worse on one side

aetiology

·      likely multifactorial

Shoe wearing

·      considered by Mann to be primary factor

·      evidence is that

·      more women are affected and women's shoes are more tight-toed

·      low incidence in unshod races (2% cf 33%)

·      incidence linearly related to length of time shoes have been worn

·      in unshod feet, toes separate on weight-bearing, and each phalanx is in line with its metatarsal

·      in shod feet, toes crowded and hallux abducted

·      incidence of hallux valgus has recently increased in Japan

·      corresponds to decrease in use of Japanese clog with interdigital thong, and rise in use of European shoes over same period

Heredity

·      usually strong family history

·      positive in 63%, cf. 1% in controls

·      those with family history usually present earlier

·      thought by some to be autosomal dominant with incomplete penetrance

·      fact that females come to surgery much more often but incidence in adolescence is equal suggests that other factors may be involved (esp. shoes)

Metatarsus primus varus

·      hallux valgus associated with metatarsus primus varus

·      strong association with adolescent variety (80%)

Other foot abnormalities

·      number of contributing structural abnormalities

Flatfoot

·      places increased amount of stress along medial border of foot

·      exerts increased force along medial side of metatarso-phalangeal joint and proximal phalanx at toe-off

Short Achilles tendon

·      limits dorsiflexion

·      results in patient walking on foot externally rotated

Neurological conditions (eg. cerebral palsy)

·      lead to pronated flatfoot and contracture of Achilles tendon

Rheumatoid arthritis

·      leads to loss of capsular support

Generalised ligamentous laxity

·      leads to

·      splaying of forefoot

·      excessive mobility of first metatarso-cuneiform joint

·      laxity of medial capsule of metatarsophalangeal joint

Joint configurations

·      predisposed by

·      round metatarso-phalangeal joint

·      oblique metatarso-cuneiform joint

Amputation of second toe

·      loss of lateral support for great toe

pathogenesis
Origin

·      starts with lateral pressure on the phalanx of the great toe

·      result is the proximal phalanx moves laterally on metatarsal head

·      leads to stretching of medial capsular complex

·      allows the metatarsal head to slide medially off sesamoid platform

Medial eminence

·      metatarsal head changes occur

·      medial part of distal and plantar articular cartilage becomes atrophied in the sesamoid groove

·      called the fossa nudata

·      medial eminence appears more prominent

·      osteophytes may develop on medial eminence

·      not real exostosis

Bunion

·      medial skin compressed between footwear and bone

·      swelling called bunion forms

·      consists of

·      callosity of skin

·      mucous bursa on medial collateral ligament, which communicates with joint

·      increased medial eminence

Progression

·      as condition progresses, metatarsal head moves further medially

·      head slides off sesamoids

·      gives appearance of lateral migration of sesamoids

·      sesamoids maintain constant distance from 2nd metatarsal

·      metatarsal ridge between sesamoids eroded

·      medial sesamoid lies under this erosion, and lateral sesamoid lies beside metatarsal head in intermetarsal space

·      1st metatarsal undergoes varus deviation

·      abductor hallucis comes to lie under metatarsal head

·      leads to medial rotation (pronation) of the great toe

·      medial extensor hood stretched and tendon of EHL comes to lie lateral to metatarso-phalangeal joint

·      tendon bowstrings

·      becomes adductor rather than extensor and exaggerates deformity

·      similarly, FHL becomes an adductor

·      eventually, the lateral capsular structures become contracted and the deformity becomes fixed

Lateral toes

·      hallux may underride or occasionally override second toe

·      sometimes second toe may be pushed into valgus and may override third toe

·      lateral toes become crowded

·      often develop claw or hammer deformities

·      increased weight-bearing through middle metatarsal heads may lead to metatarsalgia

·      enhanced by clawing of lesser toes

biomechanics

·      great toe provides stability to the medial aspect of the foot

·      through windlass mechanism of plantar aponeurosis

·      plantar aponeurosis arises from tubercle of calcaneum and medial slip inserts into base of proximal phalanx via sesamoids

·      as body passes over foot, proximal phalanx forced into dorsiflexion and slides over metatarsal head

·      plantar aponeurosis winds around metatarsal head and plantarflexes the first metatarsal

·      weight transferred from metatarsal head to hallux in 2nd half of stance phase

·      when hallux valgus occurs, this stabilisation mechanism diminished

·      due to lateral subluxation of metatarsophalangeal joint

·      windlass mechanism becomes less effective

·      results in transfer of weight to lateral aspect of foot

·      esp. 2nd metatarsal head

clinical features
History

Symptoms

Pain

·      over medial eminence from shoe pressure (usually main complaint)

·      over inflamed bursa

·      on plantar aspect from degeneration of sesamoid articulation

·      on dorsal aspect from pressure on dorsal osteophytes

·      metatarsalgia under lesser toes (esp. 2nd)

Shoe problems

·      excessive foot width with difficulty fitting shoes

Secondary deformities of lesser toes

·      esp. a hammer deformity of the second toe with rubbing of the PIP joint on the top of the shoe

Cosmetic appearance

·      often an issue in aging women

Examination

·      hallux valgus

·      assess degree of deformity

·      status of  MTP joint

·      correct valgus deformity before assessing

·      ROM and crepitus

·      osteophyte formation

·      interphalangeal joint

·      ROM

·      angle (rarely hallux valgus interphlangeus may be present)

·      toe rotation

·      degree of pronation

·      medial soft tissues

·      skin for redness, thickening, ulceration

·      bursitis

·      first tarso-metatarsal joint

·      assess mobility of ray

·      remainder of foot

·      deformities of lesser toes

·      tenderness or callosities under lesser MT heads

·      dorsal dislocation of lesser MTP joints

·      ingrown toenail

·      bunionette

·      neurovascular status

·      shoes

·      suitability

·      wear

Radiography
Views

·      weight-bearing AP and lateral

·      oblique view

·      may do sesamoid skyline view

Assessment

Hallux valgus angle

·      angle between long axes of the proximal phalanx and the metatarsal

·      ranges from 0o to 36o

·      usually considered pathological if greater than 20o

Intermetatarsal angle

·      angle between long axes of the1st and 2nd metatarsals

·      is usually less than 10o

State of 1st MTP joint

·      degree of degenerative change

Size of the medial eminence

·      judged by the amount of metatarsal head medial to the line along the medial border of the metatarsal

Degree of metatarsus primus varus

·      angle between the 1st metatarsal and the long axis of medial cuneiform

Distal metatarsal articular angle

·      relationship between the metatarsal head and the long axis of the metatarsal

·      angle between the line connecting the proximal edges of the articular surface and the long axis of the metatarsal

Degree of metatarso-sesamoid incongruity

·      sesamoids usually symmetrically related to the metatarsal head

Degree of hallux interphalangeus

·      angle between the long axes of the proximal and distal phalanges

Congruence of 1st MTP joint

·      judged by placing dots on the medial and lateral edges of the articular surfaces of the metatarsal head and base of the proximal phalanx

Treatment
Non-operative

·      initial treatment

·      standard but extra wide and large shoes, or custom-made shoes

·      insoles

·      longitudinal arch support

·      metatarsal bar for metatarsalgia

·      podiatry to attend to callosities

Operative

Indications

·      failed nonoperative treatment or nonacceptance of shoe modifications

·      surgery indicated for

·      pain

·      excessive width of foot and difficulty fitting shoes

·      secondary deformities of lesser toes

·      bursitis

·      questionable whether indicated for cosmetic appearance

Contraindications

·      poor peripheral arterial circulation

·      current sepsis

·      uncontrolled diabetes

·      peripheral neuropathy (relative)

Procedures

Young adult

·      mild deformity                 modified McBride procedure

·      moderate deformity       plus proximal metatarsal osteotomy

Middle age

·      mild deformity                 chevron distal osteotomy

·      moderate deformity       Mitchell distal osteotomy

·      severe deformity            arthrodesis

·      OA of MTP joint              arthrodesis

·      severe MTalgia              arthrodesis

Elderly

·      mild deformity                 bunionectomy

·      moderate deformity       Keller's resection arthroplasty

Rheumatoid

·      mild-mod deformity        silastic arthroplasty

·      severe deformity            arthrodesis

·      failed osteotomy arthrodesis

·      failed implant                  Keller's excision