Foot and ankle structured oral questions5: Acquired adult flatfoot

EXAMINER: I would like you to look at this clinical photograph and tell me what you see. (Figure 4.6.)

CANDIDATE: This shows a posterior view of feet in a weightbearing stance. There is marked heel valgus and too many toes are visible. The medial longitudinal arch is not visible.

EXAMINER: How do you think the medial longitudinal arch may appear?

CANDIDATE : I would expect marked flattening of the arch.

EXAMINER: What term is used to describe this situation?

CANDIDATE: Pes planus or flatfoot.

EXAMINER: Yes. In adults, what are the causes of this condition?

CANDIDATE: Presentation in adults is usually acquired. The commonest cause is tibialis posterior dysfunction. Other causes include inflammatory arthritis, Charcot arthropathy, osteoarthritis and trauma.

EXAMINER : Good. How common is adult flatfoot?

CANDIDATE: It is commoner in females and the incidence increases with age.

EXAMINER: Okay. Let’s stick with tibialis posterior dysfunction for just now. Describe a typical patient presentation.

Figure 4.6 Acquired adult flatfoot.

CANDIDATE: The classic patient would be a female aged between 45 and 65 years of age. She would describe initial pain along the course of the tibialis posterior tendon. There is likely to be later development of increasing planovalgus deformity with medial deltoid ligament pain and sometimes lateral impingement pain.

EXAMINER: What are the key examination points you would look for?

CANDIDATE: I think the most useful test is the ability to perform a single heel raise. In conjunction with assessment of hindfoot flexibility, this would allow classification and guide treatment.

EXAMINER: As you have mentioned classification of tibialis posterior dysfunction, could you tell me any more about this?

CANDIDATE: Yes. Johnson and Strom proposed a three-stage classification in 1989. Myerson and Corrigan later added a fourth stage.¹ In stage I disease, there is no deformity but pain from the tendon. A single heel raise is usually possible but painful. In stage II disease, there is a flexible planovalgus deformity and weakness of single heel raise. In stage III disease, the deformity has become fixed and in stage IV, there is additional tilting of the talus in the ankle mortise. There are recommended procedures for each stage of the disease.

EXAMINER: Good. After your examination, how would you investigate this patient?

CANDIDATE: Weightbearing AP and lateral radiographs of both the foot and ankle would help to assess structural change and exclude other causes of flatfoot. They could also show associated degenerative change. The arch index could also be measured.

EXAMINER: Would the arch index influence your management?

CANDIDATE: No. I think it is mainly used as a research tool.

EXAMINER: Coming back to your classification, you suggested that there are recommended interventions for each stage of the disease. Please tell me about these.

CANDIDATE: For stage I, I would offer debridement of the tendon followed by 6–8 weeks of casting or splintage followed by provision of a definitive arch support orthosis.² For stage II disease I would offer either a lateral column lengthening or a medializing calcaneal osteotomy in conjunction with a FDL transfer to augment or replace the tibialis posterior.³ In stage III disease, triple arthrodesis is recommended.⁴ For stage IV disease, the management depends upon the flexibility of the ankle deformity. If it is flexible, then a triple arthrodesis combined with ankle bracing or deltoid ligament reconstruction may be adequate otherwise a triple arthrodesis combined or followed by ankle arthrodesis would be indicated.

EXAMINER: You seem very clear about surgical options. What about non-operative treatment?

CANDIDATE: I should have mentioned that. It is appropriate to offer analgesia and orthotic treatment to most patients initially. An orthotic providing medial arch support with a heel cup to control heel valgus can be helpful. There are two aims of orthotic treatment. First, this may offer adequate symptom relief. Second, it may control progressive heel valgus and flattening of the medial arch.

EXAMINER: You spoke about an FDL transfer. Tell me about this procedure.

CANDIDATE: After obtaining informed consent, anaesthesia, supine positioning, thigh tourniquet and skin prep and drape, I would make an incision over the line of the posterior tibial tendon, starting posterior to the medial malleolus. I would debride or resect the tendon according to the clinical appearances. The flexor digitorum longus sheath lies directly posterior to the tibialis posterior tendon and would be opened longitudinally as far distally as possible before the FDL tendon is divided. If there is a decent distal stump of tibialis posterior, then the FDL tendon could be sutured to this but it is probably better to pass it through a hole drilled in the navicular and suture it back to itself.

EXAMINER: In what direction would you pass FDL through the navicular?

CANDIDATE: From plantar to dorsal.

EXAMINER: What is the aim of a medializing calcaneal osteotomy?

CANDIDATE: The calcaneal osteotomy directly reduces the heel valgus and brings the weightbearing axis closer to the long axis of the leg. In addition it displaces the Achilles tendon insertion medially which stops it acting as an everter of the hindfoot.

EXAMINER: When obtaining consent, what would you advise about flexion of the toes after harvesting flexor digitorum longus?

CANDIDATE: I would expect flexion of the lesser toes to be maintained by flexor hallucis longus via the knot of Henry.

EXAMINER: Can you tell me a little more about the knot of Henry?

CANDIDATE: Flexor digitorum longus crosses flexor hallucis longus on the plantar aspect. There are a number of fibrous interconnections between the two tendons that afford a degree of cooperation in movement. This means that flexion of the digits can continue after harvest of FDL or FHL.

EXAMINER: One final question. What approach would you use

for a triple arthrodesis to correct significant, fixed valgus heel deformity?

CANDIDATE: This is a potentially difficult situation. The joint preparation is most straightforward if a lateral utility approach or similar is combined with a dorsal incision over the talonavicular joint. If a significant deformity is being addressed there can be difficulty in closing the lateral incision once the deformity is corrected. There are advocates of triple arthrodesis via a single medial approach but this is difficult and not always possible.

EXAMINER: Thank you.

1. Myerson MS, Corrigan J. Treatment of posterior tibial tendon dysfunction with flexor digitorum longus tendon transfer and calcaneal osteotomy. Orthopedics 1996;19:383–388.

2. Teasdall RD, Johnson KA. Surgical treatment of stage I posterior tibial tendon dysfunction. Foot Ankle Int 1994;15(12):646–648.

3. Myerson MS, Badekas A, Schon LC. Treatment of stage II posterior tibial tendon deficiency with flexor digitorum longus tendon transfer and calcaneal osteotomy. Foot Ankle Int 2004;25(7):445–450.

4. Kelly IP, Easley ME. Treatment of stage 3 adult acquired flatfoot. Foot Ankle Clin 2001;6:153–166.