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MIDFOOT

Jump to tibialis posterior dysfunction / midfoot arthritis / cavovarus foot / ganglion

 

Tibialis posterior dysfunction

Also known as adult acquired flat foot, this is a common problem in middle-aged women. The tibialis posterior tendon runs behind the medial malleolus and inserts principally into the navicular. It inverts the foot in plantarflexion and acts as a dynamic support of the arch. It may become degenerate and tear or rupture. The result is initial pain and swelling followed by collapse of the arch, hindfoot valgus, inability to stand on tip toes and, if left untreated, arthritis of the subtalar and ankle joints.

 

Symptoms

  • Initially there is pain and swelling behind medial malleolus and along border of midfoot, but the arch and ability to stand on tip-toe is maintained.
  • Later, collapse of arch and hindfoot valgus (planovalgus) occur.
  • Finally,  arthritis develops and the deformity cannot be passively corrected.

 

Signs

  • A high index of suspicion is essential.
  • Palpation along the tibialis posterior tendon is painful.
  • With the patient standing, check if the arch is maintained and assess heel alignment.
  • Ask the patient to single stance heel raise:
  • Ask the patient to stand on the bad leg and go up onto tiptoes, using the wall for support. Watch to see if the heel rotates into varus (normal) or remains in valgus (pathological).
  • Assess power of tibialis posterior.
  • Check if a planovalgus foot is correctable by moving the subtalar joint.

 

Treatment

Treatment depends on the stage of the disease:

  • If caught early, whilst the arch is still maintained, an insole may halt progression. Request a full-length arch support with medial hindfoot posting. This will take the pressure off an inflamed tendon.
  • If the arch has already collapsed, refer the patient to the clinic.

 

Investigations

  • Weightbearing AP, lateral and oblique foot x-rays will reveal the extent of the deformity and the presence of arthritis.
  • Ultrasound can be helpful in confirming the diagnosis in early disease.

 

Referral?

  • Early cases suitable for orthotic treatment can be managed in primary care.
  • If symptoms progress, or in the presence of an established planovalgus foot, please refer.
  • Early cases of tendinopathy where the tendon remains intact can be treated with tendon debridement and orthotics.
  • If deformity has developed but the foot remains flexible, a tendon transfer, soft tissue reconstruction and calcaneal osteotomy is performed. The patient will be in plaster for six weeks followed by six weeks in a boot.
  • If arthritis has developed, a triple fusion of subtalar, talonavicular and calcaneocuboid joints is performed. The same recovery protocol applies.

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Midfoot arthritis

The exact symptoms and examination findings are dependent on which of the joints in the midfoot are affected by osteoarthritis or rheumatoid arthritis.

 

Symptoms

  • Pain, worse on weightbearing.
  • Swelling.
  • Bony spurs (known as midtarsal boss) which may rub on shoes.
  • Collapse of the arch or flat foot deformity.

 

Signs

  • Joints affected by arthritis will be tender to palpation and stiff and irritable on stressing.
  • Tarsometarsal arthritis may result in stiff flat foot (planus) deformity.
  • Identifying the location of the arthritis is not always possible clinically, and arthritis often exists in several joints.

 

Treatment

  • Analgesia, weight loss and activity modification should be tried initially.
  • Stiff soled shoes or those with a rocker-bottom may be helpful.
  • Orthotics in the form of rigid arch supports can be tried.

 

Investigations

  • Weightbearing AP, lateral and oblique foot x-rays should be performed.
  • CT can be helpful in confirming which joints are affected.

 

Referral?

  • If conservative management fails, surgical options include:
  • Targeted injections, with the objective of being both diagnostic and therapeutic. Affected joints are injected under GA with radiographic guidance.
  • Fusion of affected joints eliminates pain and corrects deformity. Patients are in plaster for 6 weeks followed by 6 weeks in a boot. Recovery may be longer in diabetics.

 

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Cavovarus foot

Cavovarus deformity is a combination of a high arch (cavus) and in-turned heel (varus). Clawing of the toes, repeated ankle sprains and metatarsalgia is often also present. Causes may be idiopathic or neurological, including spina bifida or Charcot-Marie-Tooth disease.

 

Symptoms

  • Abnormal foot shape with difficulty getting shoes to fit.
  • Recurrent ankle sprains or instability.
  • Metatarsalgia.
  • Clawing of the toes.
  • Sensory changes.

 

Signs

  • Varus heel position, best observed from behind with the patient standing.
  • Increased arch height, comparing both feet.
  • Callus on the lateral border of the foot indicating abnormal weightbearing.
  • Check flexibility of subtalar and midfoot joints.
  • Examine the spine and perform a neurological examination.

 

Treatment

  • In mild cases, orthotics may help reduce pain and stabilise the ankle. Often they are bulky and require custom shoes to be made. If the ankle is unstable, a calliper or AFO may be required.

 

Investigations

  • Weightbearing AP and lateral ankle and AP, lateral and oblique foot x-rays.
  • In presence of abnormal neurology or if diagnosis unclear, nerve conduction studies and MRI lumbar spine.

 

Referral?

  • Patients should be referred if the deformity is progressing or asymmetrical, or symptoms are unmanageable with orthotics.
  • Surgical correction is complex and often comprises several staged procedures.
  • Options include calcaneal osteotomy, midfoot osteotomies, tendon transfers and soft tissue releases. In severe cases with stiff joints, extensive fusions may be required.

 

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Ganglion

A ‘bulge’ of a joint capsule in which a one-way valve effect creates a gradually enlarging swelling. In the foot they may arise from any joint but are most common in the joints of the midfoot.

 

Symptoms

  • A painless swelling which may fluctuate in size.
  • May irritate overlying skin and rub on shoes.
  • May be related to previous trauma or underlying arthritis.

 

Signs

  • Fluctuant swelling over a joint.
  • Will transilluminate, but this is difficult to demonstrate in practice.

 

Investigations

  • Generally a clinical diagnosis, but ultrasound may be helpful.

 

Treatment

  • Conservative if not symptomatic. 20% reduce in size spontaneously, 20% enlarge and 60% stay the same.
  • Aspiration may be performed in the clinic. This confirms the diagnosis and also offers a 50% chance that it will be permanently resolved (although a 50% chance of recurrence).
  • Using a green needle, aspirate directly over the swelling. The fluid is often too thick to draw into the needle, so through the same skin entry point, make several holes in the capsule of the ganglion, remove the needle and express the fluid manually. Steroid injection is not recommended because of the skin changes and depigmentation that can result.

 

Referral?

  • For recurrent cases or those where the patient does not want aspiration, surgical excision offers an 80% chance of permanent resolution but will leave a scar which may be tender.

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