Fibularis lungus, historia brevis

Dr Frederic PELLASa, Dr Corinne GAGNARDa

a CHU Caremeau

Fibularis lungus (FL) action and participation in gait disorders is often underestimated, although first description of the impact on gait of a FL "spasm" dates from 1872 (*).

Case history : 30 years aged men, with multiple sclerosis spastic tetraparesis, cerebellar hypotonia and ataxia. Functional exam: completely independent in everyday life activities, with difficulties to put on shoes, needing one croutch outside. Physical exam : paresthesia, thermoalgesic and proprioceptive hypoesthesia in both lower legs (LL), proximal weakness prevailing on the left, dystonia of extensor hallucis longus (Hallucis erectus) and clonus of soleus and gastrocnemius of both legs.

Gait analysis : FL is responsible for a left-hand side pattern prevailing on the left-hand side, associating “footdrop” and sole’s eversion during swinging phase, valgus-valgus instability of the heel during stance and heel medial-lateral oscillations when standing tiptoe;[pre injection video].

Treatement’s history : first, all three calf muscles of both legs have been injected (total of 300 UI Botox) but patient developed a botulism-like syndrome with; he had no profit of second injection with 25 units in both gastrocnemius and TP of each leg, rather it caused drastic weakening of propulsion. Treatment aims: improve control of inversion-eversion couple during terminal stance, without weakening propulsion strength or heel’s medio-lateral stability during tiptoe stance.

Treatment: injection of only left leg trigger muscles (FL and it’s antagonists : TP, Extensor Hallucis Longus) with 50 UI each (total =150)

Post injection exam : bilateral decrease of medial-lateral heel & leg-body oscillationsduring tiptoe stance, better leg shortenig during swing & no personal sensation of propulsion.

Conclusion : muscles actions must always be considered taking into account both proximal or distal fixed points. In case of proximal fixed point, LPL plantar flexes foot and everses sole ; when fixed point is distal, FL steadies leg (and body) upon the foot in frontal plane and draws leg’s lateral side outwards.

[post injectionVIDEO]

Guillaume-Benjamin Duchenne (de Boulogne) : “Impotence fonctionnelle et spasme fonctionnel du long péronier latéral » ; Archives générales de médecine 1872, série 6, n° 20. - Paris : P. Asselin (Ed)