Foot Muscle Forces & Deformities - Foot & Ankle

Introduction

Simple Deformities
Deformity	Strong Muscle	Weak Muscle
equinus	gastrocnemius-soleus complex	dorsiflexors
cavus	plantar fascia, intrinsics	dorsiflexors
varus	posterior tibialis and anterior tibialis	peroneal brevis
supination	anterior tibialis	peroneus longus
flatfoot	peroneus brevis	posterior tibialis
Complex Deformities
equinovarus + supination	gastroc-soleus complex, posterior tibialis, anterior tibialis	peroneus brevis & longus
equinovalgus	gastroc-soleus complex, peroneals	posterior tibialis, anterior tibialis
calcaneovalgus	foot dorsiflexors/evertors (L4 and L5)	plantar flexors /inverters (S1 and S2)

Introduction

Equinovarus foot
- most common deformity following stroke
  - use AFO and physical therapy for at least 6 months to await for possible neuro recovery
  - overactivity of the tibialis anterior, with contributions from the FHL, FDL, and tibialis posterior
- treatment
  - nonoperative
    - AFO fitting
    - physical therapy
    - Phenol or botox injections
  - surgical
    - split anterior tibial tendon transfer (SPLATT)
    - flexor hallucis longus tendon transfer to the dorsum of the foot and release of the flexor digitorum longus and brevis tendons at the base of each toe
    - gastrocnemius or achilles lengthening
Foot drop
- Inability to dorsiflex at the ankle and/or toes
- Commonly result from peroneal nerve palsy
  - Multiple etiologies
    - central nervous system (brain, spinal cord, nerve roots)
    - peripheral nervous system (sciatic nerve, peroneal nerve)
    - traumatic (knee dislocation, laceration, blunt trauma)
    - compressive (compressive mass, deformity correction)
    - systemic (diabetic polyneuropathy, mononeuropathy)
    - Iatrogenic (laceration, casting, positioning, surgical injury)
    - Mechanical (muscle debridement, tumor excision, etc.)
- Presentation - variable depending on location of nerve injury
  - Motor
    - Loss of ankle/toe dorsiflexion (DPN)
    - Loss of ankle eversion (SPN)
  - Sensory
    - Loss of first dorsal webspace sensation (DPN)
    - Loss of lateral leg/dorsal foot sensation (SPN)
- Treatment
  - Nonoperative
    - Observation
    - AFO bracing
    - Therapy - stretching and supple joints
  - Operative
    - Acute injury
      - Laceration - repair, grafting, or nerve transfer
    - Chronic injury
      - Tendon transfer
        
        Posterior tibial tendon transfer to lateral cuneiform +/- gastroc or Achilles tendon lengthening

Physical Exam

Silfverskiöld test
- improved ankle dorsiflexion with knee flexed = gastrocnemius tightness
- equivalent ankle dorsiflexion with knee flexion and extension= achilles tightness