Definition
Acquired Adult Flatfoot Deformity (AAFD)
- collapse of medial longitudinal arch
- secondary to ligament / tendon / joint or bony pathology
Classification
1. Congenital
Flexible / Physiological
Ligamentous Laxity (DIAL HOME)
Rigid
- Congenital Vertical Talus
- Tarsal Coalition
2. Acquired
Tibialis Posterior Dysfunction
RA Flat Foot
Neurological
- Charcot Foot
- spinal dysraphism
- CP
- polio
OA
Midfoot OA / Lis Franc injury
Subtalar joint OA (calcaneal fracture)
Ankle OA
Ligament
- isolated spring ligament rupture (rare)
- iatrogenic / traumatic plantar fascia rupture (rare)
Compensory to Rotational & Coronal plane deformities
- tibial torsion
- genu valgum
- ankle equinus 2° tight TA
Biomechanics of FlatFoot
Normal Gait / 3 phase rocker
1. Heel Strike
Tibia IR
Hindfoot Everts
- unlocks TNJ & CCJ
- forefoot pronates
Allows shock absorption by hind/mid/forefoot
2. Stance
- WB axis passes through ASIS to patella to middle of foot
3. Toe Off
T Posterior "locks" the midfoot (i.e. the transverse tarsal joints)
- T Anterior inverts the hindfoot
- T Achilles plantar flexes the calcaneum
- Tibia externally rotates
Flatfoot Gait
The above components are exaggerated
- More stress on ligament structures
WB axis shifts medially, causing
- increased femoral anteversion
- internal knee rotation
- increased Q angle
T Achilles becomes evertor
Increased pronation
- may cause Hallux Valgus
Specific Conditions
Lisfranc Joint OA
Aetiology
1. Post injury
Degenerative arthritis develops after fracture dislocation
- Acute injury often missed
- Adequate acute treatment may not prevent occurrence
2. Idiopathic
- not related to trauma
3. Charcot
X-ray
Degenerative changes invariably involve second MT/ 2nd Cuneiform joint
- may involve 1st & 3rd joints
- rarely involves 4th & 5th joints
Non-operative
Moulded arch support / UCBL initially if correctable
Lateral Single Upright caliper with Medial T strap if not
Operative
Realignment of Lisfranc joint with arthrodesis
Rheumatoid Flat Foot
50% will get flat foot
- subtalar OA
- spring ligament attenuation
- tibialis post dysfunction
- progressive valgus deformity at hindfoot
OA of Ankle Joint
Usually post traumatic
- valgus tilt of Talus leads to pronation of Talus & Calcaneus
Flatfoot def corrected when AJ realigned
Charcot Flat Foot
90% changes in hind and midfoot
- repetitive microtrauma in presence of neuropathy leads to microfracture
- 2° to Sensory & Autonomic Neuropathy
Progressive subluxation / collapse
Usually associated with Diabetes
- may be marked collapse
- develop bony prominence on medial sole
- may cause ulceration
Plantar Fascia Rupture
Traumatic or spontaneous
- pain at calcaneal origin
- palpable gap
- often 2° excess HCLA
Management
- arch support
- longitudinal arch will slightly flatten, but rupture should heal
Spring Ligament Rupture
Rare
- ? Repair
- probably in reality treat as for PTTD