|
|
 |
|
Volume 1 - The Slipped Muscle
|
Lecture 12 of 24 NEXT»
|
A very unwelcome result in strabismus surgery is the overcorrection or undercorrection. An even less welcome result is the huge overcorrection or undercorrection with limited movement in the field of action of an operated muscle. For example:
In this case, if a bimedial rectus recession had been done the cause of the overcorrection with limited adduction OS is a slipped left medial rectus. Passive ductions in the left eye should be unrestricted and generated force should be weak. LR contracture with restricted passive adduction may be found if the XT is left untreated for an extended period of time.
|
 |
In the case of a slipped medial rectus, the palpebral fissure may be vertically enlarged and the plica and caruncle displaced medially. |
 If a recession of the left medial rectus and resection of the left lateral rectus had been done the findings would be similar to slipped medial rectus if the XT were due to tight lateral rectus except passive adduction OS would be restricted and generated force in adduction would be normal.
Is the muscle slipped or lost? Actually, no muscle is ever lost. The muscle remains in the orbit!! If the term "lost" has any value, it is to describe a muscle which has "lost" attachment to the globe in contrast to a muscle whose attachment to the globe has "slipped" or moved farther from the origin or closer to the insertion thereby weakening the muscle's pull on the globe.
Early vs. Late Slipped Muscles
An immediate, large over or undercorrection with limited duction in the field of action of the presumed slipped muscle is cause for prompt reoperation.
In example #1, the left medial rectus may have slipped. In example #2, the left lateral rectus resection may have slipped. In example #3, the right lateral rectus recession may have slipped. In case of early recognition of a slipped muscle prompt reoperation, doing the intended surgery is the treatment of choice.
"Late" Slipped Muscles
 In cases of bimedial rectus recession, an overcorrection can occur over months or years. Adduction is reduced, the palpebral fissure is widened, and the caruncle and plica are recessed. These cases must be treated by resection and advancement of the medial recti.
The Operative Picture in a Late Slipped Medial Rectus (Plager/Parks)
|
Muscle |
|
Intended New Insertion |  |
In this case the empty capsule acts as an elongated tendon weakening the action of the muscle. This empty capsule has been called a "stretched scar". The cause of a slipped muscle is failure to attach vascularized muscle to the scleral surface.
|
Original Insertion |
|
 |
|
"Empty Capsule" |
|
|
Functional New Insertion | |
Treatment of a slipped medial rectus as shown above is resection and advancement -
|
1. The suture should be placed a few millimeters into the substance of the muscle.
|
2. The muscle is then advanced usually to a point anterior to the originally intended recession but short of the original insertion. Because the slipped recessed muscle "stiffens" it cannot be brought up to the original insertion.
Advance Resected |
Avoiding a Slipped Muscle
The suture in a recession should be placed at least 1mm from the insertion. This can be accomplished if the suture is placed just behind a thin 8mm-10mm or 12mm muscle hook. See Vol. 1, No. 6.
|
The medial rectus muscle can be recessed in its capsule
|
The scleral bite should be at least 1.5mm long and at least .2mm deep using 6-vicryl suture or equivalent*.
* The numbers were established in invitro studies by Coats and Paysse. |
In the clinical setting, late slipping of the medial rectus is the most commonly encountered slipped muscle. (Ludwig has called this stretched scar.) Acute slippage (loss) from suture failure is rarely encountered since the advent of synthetic absorbable suture (vicryl-dexon). A slipped muscle occurs not infrequently after inferior rectus recession especially in thyroid disease. It occurs rarely after superior rectus recession or lateral rectus recession.
Remember! Slipped muscles can be avoided by exercising good technique as follows:
#1 take a sufficient bite in muscle
 Some surgeons add a knot in the center of the muscle and lock the suture at the borders.
#2 take an adequate bite in sclera
|
At least .2mm deep   At least 1.5mm long |
Some surgeons prefer the hang loose for all recessions, most use "hang loose" in selected cases such as those with thin sclera, etc.
|
The Strabismus Minute, Vol.1, No. 18 Copyright (C) 1999 Eugene M. Helveston All Rights Reserved
Editor-in-Chief: Eugene M. Helveston, M.D.
Associate Editor: Faruk H. Orge, M.D.
Editorial Board: Bradley C. Black, M.D.
Edward O'Malley, M.D.
David A. Plager, M.D.
Derek T. Sprunger, M.D.
Daniel E. Neely, M.D.
Naval Sondhi, M.D.
Senior Editorial Consultant: Gunter K. von Noorden, M.D.
Graphics: Michelle L. Harmon
Technical Support: George J. Sheplock, M.D.
|
|
|
|
Print this Page