Extra-ocular muscle rupture is
uncommon, usually
seen after penetrating trauma or surgery.The inferior rectus is the
muscle most frequently involved in sever anterior
trauma of the orbit. This may be due to the fact
that the protective Bell phenomenon places the
inferior rectus in harms way as the eye rotates
upward.
In this patient the
significant lower lid ptosis suggests that the
muscle is there but was not properly attached to the
globe .The
presence of lower lid ptosis and the fact that some
depression of the left eye remains suggests that the
inferior rectus continues to act and that if it is
reattached, the lid will come up and the eye will go
down .
Surgery for this patient would
consist of:
1) Exploration of the left inferior rectus
2) Advancement of the inferior rectus to the
original insertion.
3) Since trauma is very long ago
( 15 years ) , one couldn't swear this plan will
work excellent , paresis or even palsy of the IR is
expected and inverse Knapp procedure arises as an
alternative choice if the first plan fails .
In inverse Knapp procedure the MR & LR are
disinserted and attached to the adjacent borders of
the site of the insertion of the IR .
The inverse
Knapp operation is the generally accepted primary
procedure of choice for acquired isolated inferior
rectus weakness of a marked to severe degree without
mechanical restriction. The procedure reduces
symptomatic primary position and downgaze vertical
deviations and minimises lid malposition.
There is no evidence in the
literature to suggest that this desirable effect
deteriorates over time. Additional surgery may still
be required to lessen residual symptomatic vertical
deviation, since the procedure cannot be expected to
normalize downgaze versions in this patient
.
Inverse Knapp procedure is an Uncommon strabismus
operation but an extremely useful one in selected
cases. I recommend it for the treatment of marked
inferior rectus weakness, congenital or acquired,
for post-traumatic inferior rectus underaction with
or without orbital blow-out fracture and for
residual large hypertropia in patients with poor
binocular functions. The extent of inferior rectus
underaction should be assessed very carefully to
avoid overcorrecting. Others have reported good results with a recess/resect
procedure in the treatment of inferior rectus
weakness.
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