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Chapter 11: Faden operation (posterior fixation suture) -  

Posterior fixation suture (retroequatorial myopexy, faden operation)

Lecture 1 of 6  NEXT»


The modern posterior fixation suture (PFS) was described by Cüppers in Germany. It was done initially in the United States in 1975 after being introduced by Mühlendyck. The procedure has been popularly called the ‘faden operation.’ Faden in German means suture or string. However, more descriptive names, posterior fixation suture or retroequatorial myopexy more appropriately describe the procedure.

The aim of the posterior fixation suture is to shift the effective insertion of a rectus muscle posteriorly employing a principle that was described first by Peters more than forty years before. This posterior shift of the muscle’s insertion theoretically reduces the effect of the muscle only in its field of action. The posterior fixation itself is designed to have little if any effect in the primary position. However, if the muscle posterior to the suture is on a stretch while the suture is placed, redundant muscle between the origin and the fixation suture may effect the muscle’s action in primary position. This may be the reason for reports saying that PFS done on the medial recti are effective in reducing an esodeviation (Figure 1).

 

fig. 1

Figure 1
A The eye is shown from above the medial rectus on top.
B With the eye in abduction, the medial rectus is stretched.
C The posterior fixation suture is placed with the medial rectus on the stretch.
D As the eye moves back to the primary position, the medial rectus behind the suture is loose or redundant. This would theoretically weaken the effect of the medial rectus in the primary and thereby reduce the esodeviation.

 

The PFS has no effect on the initiation of eye movement or on the behavior of eye movement in the field opposite the muscle having the PFS. The principal effects of the PFS are to somewhat limit the movement of the eye in the field of action of the muscle treated and to cause increased innervation to this muscle and its yoke by Hering’s law as the eye attempts to move in the field of muscle with the PFS.

At the outset, the indication for the PFS was to treat the nystagmus blockage syndrome. This condition has been said to be characterized by: (1) manifest nystagmus damped by convergence, (2) variable angle esotropia, (3) pseudoparalysis of both lateral rectus muscles with nystagmus on attempted abduction, and (4) preference for fixation in adduction while the head turns in the opposite direction, with or without occlusion of the opposite eye, or for fixation with asymmetric convergence while the head remains straight. Most of these characteristics are shared by the Ciancia syndrome patients as a manifestation of congenital esotropia.

The posterior fixation suture has also been used on the superior rectus muscles to treat dissociated vertical deviation done with or without recession of the superior rectus. However, this procedure did not seem to have sufficient ‘power’ and has been replaced by large recession of the superior recti, and in selected cases anterior transposition of the inferior obliques and, in persistent cases, inferior rectus resection.

Another indication for the PFS, and in my opinion the very best and most useful, is to weaken the sound yoke of an underacting muscle in order to create a secondary deviation which both boosts the action of the weak muscle and slightly limits the action of the sound muscle. This is what I call a laudable secondary deviation. Here is an example: A patient has a weak left lateral rectus muscle with limited abduction of the left eye and diplopia in levoversion beginning just a few degrees beyond the midline. With a posterior fixation suture placed on the right medial rectus two things happen. First, the right medial rectus works harder to move toward levoversion and therefore sends more innervation to the left lateral rectus by Herring’s law (a secondary deviation). Second, the right eye cannot go as far in levoversion because of the PFS and therefore is less likely to exceed the excursion of the left eye in usual visual activity thereby reducing the likelihood of diplopia (Figure 2).

 

fig. 2

Figure 2
A
The muscle is secured to underlying sclera at or just behind the equator.
B The extent of rotation of the eyeball is restricted by the suture compared to movement without the suture in place.
C The new effective insertion creates a reduced lever arm for the muscle. This reduced lever arm results in the need for increased innervation for the muscle to achieve its full (though reduced) rotation.

 

Although not treating yoke muscles, a PFS may be placed on the normally acting inferior rectus in case of weakness of the other inferior rectus. In this example, there is no secondary deviation effect, only the pure limitation of movement or ‘pseudoparalysis’ of the sound muscle treated with the PFS. This would result in the two eyes being more nearly matched in down gaze thereby avoiding or at least reducing diplopia. Because far up gaze is less important than down gaze including the reading position (except in certain exceptions) this procedure is less likely to be indicated for the superior rectus (Figure 3).

 

fig. 3

Figure 3
A
The eyes are aligned in the primary position.
B The right eye has deficient depression from a right inferior rectus paresis.
C In far down gaze, the left eye moves normally, resulting in an increasing right hypertropia and diplopia in the reading position.
D With a posterior fixation suture placed on the normal left inferior rectus, the movement downward in this eye is somewhat limited making it more nearly match the right eye. The yoke of the left inferior rectus, the right superior oblique, a depressor of the right eye, would also receive more innervation to down gaze.

 

I have used a posterior fixation on the four horizontal rectus muscles as a means of treating nystagmus. The few cases that I treated were not successful. Recession of the four horizontal rectus muscles has been effective for treatment of nystagmus, and Hertle has reported success with simple disinsertion and reinsertion of the muscles.

 

 


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