What is a flatfoot?
Pes planus or a flatfoot is characterised by a flattened arch with the foot pointed more outwards and/or pronated. Children gradually develop the arch of their feet as they grow older. A proportion of the normal adult population can continue to have flatfeet due to their genetic predisposition or a tarsal coalition (an abnormal persistent connection between bones in the foot), or be associated with an accessory navicular (an extra bone on the inner side of the foot near their arch) which are often asymptomatic. This is in contrast to an adult-acquired flatfoot which can occur as a result of tibialis posterior tendon dysfunction, arthritis, injury to the Lisfranc joint or Charcot arthropathy. A flatfoot deformity can progress over time and predispose to early hind-midfoot joint degeneration.
What are common symptoms associated with a flatfoot?
The tibialis posterior tendon is important in maintaining the arch and stabilising the foot during standing and walking. Degeneration or injury to this tendon can cause pain and swelling over the inner aspect of the hindfoot and ankle, and eventually become weak and lead to a flatfoot. In addition to flattening of the arch of their foot over time, patients may report further pain on the outside of their hindfoot and below their ankle due to subfibular impingement from their worsening flatfoot deformity. Arthritis or injury to the tarsometatarsal joints (Lisfranc joint) can result in instability of the midfoot and also cause pes planus. The usual aetiology of a Charcot foot is diabetic neuropathy which can lead to collapse of the midfoot with issues arising from progressive arthritis, deformity and pressure areas.
How can a flatfoot be managed?
The management options for a symptomatic flatfoot are guided by whether the deformity is flexible or fixed. Non-operative management strategies include wearing cushioned stiff or rocker sole shoes with medial arch support, using medial arch support orthotics, losing and maintaining a healthy weight, activity modification by avoiding activities which aggravate your symptoms and by preferencing low impact-loading activities for exercise/recreation in the long term, such as swimming, cycling and Pilates, simple over-the-counter oral analgesia and/or oral/topical anti-inflammatory medication if not contraindicated as required, and/or an ultrasound-guided corticosteroid and local anaesthetic injection to the sinus tarsi for subfibular impingement. Patients may also benefit from physical therapy or prehabilitation focusing on calf, ankle and foot range of motion and stretching exercises, and general conditioning and strengthening of their lower limbs to optimise their pre-operative baseline, including exercising in the swimming pool or doing hydrotherapy.
What are the surgical treatment options for a symptomatic flatfoot?
For patients with a corrigible deformity, a flatfoot reconstruction involving a combination of bony and soft tissue joint-preserving procedures can be considered. This typically includes cutting or performing osteotomies of the heel bone (calcaneum) and in the midfoot (usually a posterior calcaneal medial shift, Evans and Cotton osteotomy) to improve the alignment of the hindfoot and forefoot, and doing a tendon transfer of the flexor digitorum longus to augment the weakened tibialis posterior tendon. Patients who have an advanced or fixed pes planus deformity with secondary arthritis may require more invasive and definitive surgical intervention in the form of a corrective arthrodesis or fusion of the hindfoot joints. This is less preferred to the aforementioned reconstructive option, because the hindfoot is made permanently stiff with a fusion.
What is the recovery after a flatfoot reconstruction?
After your flatfoot reconstruction, you will be non-weight-bearing through your operated foot for 6 weeks, and can then gradually progress from partial to full weight-bearing over another 6 weeks. You will be immobilised in a below-knee plaster backslab/fibreglass cast for 6 weeks, and can then transition to a CAM boot with a medial arch support orthotic. You will need to wear your CAM boot when ambulating only for this subsequent 6 weeks. For most patients, it will take 2-3 weeks for your wounds to heal, 4-5 months for your corrective osteotomies to unite and tendon transfer to regain its functional strength, 6-7 months before you are reasonably comfortable walking in normal shoes with medial arch support orthotics, and at least 12 months for the swelling in your foot to subside and for full recovery to your new baseline level. The risk of recurrence of a flatfoot deformity after a reconstruction can be reduced by being diligent with supportive footwear, medial arch support orthotics and maintaining a healthy weight.