Vertical Muscle Transposition Augmented With Lateral Fixation
R. Scot t Fos ter , M D
Introduction: Full vertical rectus muscle transpositions have been shown to be an effective treatment for lateral rectus palsies and type I Duane syndrome. This operation is usually accompanied by mechanical or botulinum toxin treatment of one or both medial rectus muscles. This series evaluates the effect of augmenting the transposed muscles with lateral fixation sutures. Methods:Transposition of the vertical rectus muscles to the lateral rectus muscle was performed in 23 eyes of 21 patients; transposition to the medial rectus muscle was performed in one eye of one of these 21 patients. A lateral fixation suture of 5-0 Dacron polyester filament was placed in the sclera 16 mm posterior to the limbus and adjacentto the lateral rectus muscle, incorporating one fourth of the transposed vertical rectus muscle. Of the 21 patients, five had type I Duane syndrome with a face turn and esotropia in the primary position, seven had a unilateral lateral rectus palsy, two had bilateral lateral rectus palsy, four had an ipsilateral lateral rectus palsy combined with a contralateral lateral rectus paresis (a recess resect procedure was performed on the paretic eye along with the augmented transposition on the paralyzed eye), two had gaze palsies, and one had a unilateral lateral rectus palsywith recurrent esotropia after a transposition procedure performed 16 years previously. Lateral fixation sutures alone were used in the last case listed. Postoperative diplopia-free fields were measured when possible (10 cases). Results: In most cases (19/23 eyes), alignment was achieved in the primary position with the use of the augmented transposition procedure alone. On average, 20 degrees of binocular fusion into the abducted field was obtained. No postoperative limitation of adduction in the transposed eye was noted. Among the patients with Duane syndrome, 80% had elimination of the face turn; one patient had 5 degrees of residual face turn.The one patient with previous transposition surgery alone had an 80% (16 PD) reduction ofthe recurrent esotropia after placement of lateral fixation sutures. After augmented transpositions, induced vertical deviations in the primary position were uncommon (4/20 patients) and not greater than 2 PD. Significant lid fissure changes were not seen. Conclusions: The addition of lateral fixation sutures to full vertical rectus muscle transpositions improves the tonic abducting force of the procedure for patients with lateral rectus palsy and type I Duane syndrome without compromising adduction. (J AAPOS 1997;20-30)
A lmost one century has elapsed since Hummelsheim ~ first described a muscle transposition procedure for the treatment of lateral rectus muscle palsies
(paralysis). Since then, a variety of transposition procedures have been promoted. 2
Currently several authors advocate full vertical muscle transpositions over other forms of treatment for true lateral rectus muscle 3-6 palsies, as well as type I Duane syndrome with esotropia and a face turn in the primary position. 7-9 This procedure, which is usually combined with a medial rectus muscle weakening, has been shown to provide a satisfactory diplopia-free field in the abducted position and an improved
total diplopia-free field. 3, s, 6, 8 The full adduction field,. however, is usually compromised (<50 degrees).
Full vertical muscle transpositions to the lateral rectus muscle produce an abducting tonic force by changing the force vectors of the transposed vertical muscles. In addition, the passive elastic forces are increased somewhat by lengthening the path of these muscles.I° The direction of the transposed vertical rectus muscles is not parallel to the lateral rectus muscle but rather approaches at an angle of 45 degrees.i° Recent magnetic resonance imaging of transposed muscles has demonstrated verylittle lateral movement of the vertical rectus muscles posterior to the equatorY Theoretically, the tonic abducting forces of the transposed vertical rectus muscles could be improved if the distance between these muscles and the lateral rectus muscle were reduced or closed. This study evaluated the effect of "closing the gap" between the transposed vertical rectus muscles and the lateral rectus muscle by transfixing the transposed muscles to the sclera adjacent to the lateralrectus muscle at the equator.
Journal o f A A P O S
Journal of AAPOS Volume 1 Number 1 March 1997 Foster 21
TABLE 1. Augmented transposition (21 patients)
No. of patients Diagnosis
Type I Duane syndrome (head turn >25 degrees) Bilateral lateral rectus muscle palsy Lateral rectus muscle palsy with lateral rectus
contralateral medial rectus muscle palsy or paresis (gaze palsy)
Transposition with delayed lateral fixation sutures
S U B J E C T S A N D M E T H O D S
Patients in this study (Table 1) included those with type I Duane syndrome with esotropia >25 PD in the pri- mary position, a head turn >25 degrees, full or minimally limited adduction, and no significant upshoots or downshoots in the adducted position. The patients with lateral rectus muscle palsy all demonstrated no abducting force on forced generation testing and "floating" abducting saccades when rotations would allow this observation. Measurements were obtained with theprism and cross-cover test in the diagnostic gaze positions. Voluntary ductions and forced ductions were tested on all patients. Binocular diplopia-free visual fields were assessed after the operation in 10 patients. The technique, with use of the Goldman perimeter, has been described by Feibel and Roper-Hall. 12
The surgical technique (Figure 1) is initiated by a 270- degree limbal conjunctival peritomy made from the superior nasal quadrant to the inferior nasal quadrant. The fascia surrounding the inferior rectus muscle, superior rectus muscle, and lateral rectus muscle was dissected free. Care was taken to free the inferior rectus muscle from the capsulopalpebral fascia and to free the superior rectus muscle from attachments to the superior oblique tendon. A single double-armed 6-0 polyglactin suture (ViclT1; Ethicon, Inc. Somerville, NJ.) was then passed through the insertion of the superior rectus muscle and another was passed through the inferior rectus muscle insertion. These muscles were then detached from the globe. A single-armed 5-0 Dacron polyester fiber nonabsorbable suture was then placed through the sclera adjacent to the inferior border of the lateral rectus muscle, 16 mm posterior to the limbus. Another Dacron polyester fiber suture was then passed similarly through the sclera adjacent to the superior border of the lateral rectus muscle.
The distances between the limbus and the middle portions of the original insertion site of both the superior and inferior rectus muscles are then measured and the vertical rectus muscles are transposed to the lateral rectus muscle, following the spiral of Tillaux. The temporal inferior rectus muscle suture is placed through the inferior edge of the lateral rectus muscle insertion, and the medial inferior
S ~ Transposed left ~ i superior rectus / X
~ muscle
~-- 8ram -4 Left lateral rectus L muscle
, ~ A ~ Lateral fixation I ~ ~ suture
x~'~ " ""'x Transposed left inferior rectus muscle
FIG. 1. Augmented transposition./, Distance in millimeters measured from the limbus to the mid inferior rectus muscle insertion; S, distance in millimeters measured from the limbus to the mid superior rectus muscle insertion; arrowheads, scleral site of 5-0 Dacron suture.
rectus muscle suture is placed through the sclera one tendon width inferomedial to the temporal suture. The distance from the limbus to the medial border of the inferior rectus muscle is equivalent to the original inferior rectus muscle insertion distance. The two sutures are then tied.
In a similar fashion, the superior rectus muscle is transposed to the lateral rectus muscle. After this has been done, the 5-0 Dacron polyester fiber lateral fixation suture is placed through the lateral border of the transposed vertical rectus muscle, incorporating 25 % of the muscle tissue. When this suture is pulled tight and tied in position, the gap between the lateral rectus muscle and the transposed vertical rectus muscle is closed (Figure 2). The conjunctiva is then closed with 8-0 polyglactin (Vicryl) suture. Forced ductions are assessed before and after the transposition in all cases. In no case was limited forced adduction observed.
Magnetic resonance imaging was performed on the orbits of one patient after placement of lateral fixation sutures on previously transposed vertical rectus muscle. This technique 'of thin-slice serial sections perpendicular to the long axis of the optic nerve has previously been described. H
R E S U L T S
Observation at the time of operation demonstrated that the distance between the lateral rectus muscle and the transposed vertical rectus muscles, before placement of lateral fixation sutures, was between 6 and 7 mm at the fixation suture site (45 degrees). Once the lateral fixation sutures are secured anterior to the equator, this "gap" is closed (Figure 2).
Magnetic resonance imaging was performed on the orbits of patient 15 after placement of lateral fixation sutures to the previously transposed left vertical rectus muscles. The muscles in the left orbit were compared with the muscles in the "normal" right orbit by reversing the right film (Figure 3). A lateral shift of the left superior and inferior rectus muscles near the equator and posterior to the globe is seen.
Journal of AAPOS 22 Foster Volume 1 Number I March 1997
FIG. 2. Leftside, Vertical rectus muscle transposition to the lateral rectus muscle. Rightside, Addition of scleral fixation sutures 16 mm posterior to the limbus. Arrows, Force vectors; arrowheads, scleral site of 5-0 Dacron suture.
TABLE 2. Duane syndrome type I with face turn _>25 degrees
Patient Face turn Esotrepia Forced No. Age (yr) (degrees) (PD) Abduction Adduction abduction Follow-up
1 2 L 25 L 25 -4 0 -1/2 3 yr 2 17 L 25 L 25 -4 0 -2 1 yr 3 15 L 30 L 30 -4 0 -1 3 yr 4 18 L 25 L 30 -4 0 -2 1 mo 5 8 L 30 L 30 -4 0 0 8 mo
L, Left.
TABLE 3. Patients with Duane syndrome after augmented trans 3ositions
Patient Deviation Face turn No. (PD) (degrees) Abduction Adduction
Diplopia-free visual field (deqrees) ABD ADD Total
1 0 0 -3.5 0 2 2 RHT 0 -3 0 Suppress 3 8 EP 0 -3.5 0 15 50 4 8 EP 2 LHP 0 -3.5 0 5 2 EP L 5 -3.5 0
65
ABD, Abduction; ADD, Adduction; RHT, right hypertropia; EP, esophoria; LHP, left hypertropia; L, left.
Duane syndrome
Five patients with type I Duane syndrome, a face turn ___25 degrees, and esotropia _>25 PD were studied (Table 2). The average age was 12 years (range 2 to 18 years) with an average follow-up period of 1.5 years (range 1 month to 3 years). The results, seen in Table 3 and Figures 4 and 5, demonstrate that the face turn was eliminated in nearly all cases (4 of 5). Small vertical and/or horizontal
deviations were seen in most patients (4 of 5). There was no decrease in adduction in any patient; this is represented by the full 50 degrees of diplopia-free visual field in the adducted direction in patient 3 (Figure 6).
Lateral rectus muscle palsies
Sixteen patients with lateral rectus muscle palsy were studied (Table 4). Included were patients with bilateral
Journal of M P O S Volume 1 Number I March 1997 Foster 23
lateral rectus muscle palsies, unilateral lateral rectus muscle palsies, lateral rectus muscle palsies combined with lateral rectus paresis, and gaze palsies. The average age was 50 years (range 19 to 88 years), and the average follow-up period was 2 years (range 1 month to 16 years).
Bilateral lateral rectus muscle palsies
Table 5 demonstrates the results of bilateral lateral rectus palsies treated with augmented transpositions only; medial rectus surgery was not performed. These two patients had on average 23 degrees of diplopia-free field into abduction and a total horizontal diplopia-free field of 46 degrees. Neither patient had a residual face turn. In patient 7, forced ductions were performed 3 months after the transposition procedure. The forced ductions improved significantly, indicating a decrease in the medial rectus stiffness. Figure 7 illustrates the results for patient 7.
Unilateral lateral rectus muscle palsies
Table 6 shows the results of four patients with unilateral lateral rectus palsies who were treated with an augmented transposition only. In patient 8, the forced ductions were tested 1 year after the operative forced ductions were performed. As in patient 7, this patient demonstrated a decrease in the stiffness of the medial rectus muscle. The two diplopia-ffeevisual fields show satisfactory abduction with no limitation of adduction. None of the patients had a residual face turn (Figures 8 and 9 illustrate the results for patient 8).
Table 7 lists the results of three patients with unilateral lateral rectus palsy who underwent augmented transposi- tions and also had medial rectus surgery. Patient 12 had a significant residual deviation after the posterior fixation sutures were placed 13 mm posterior to the limbus rather than the usual 16 mm. Six weeks later, 5 units ofbotulinum toxin was injected into the ipsilateral medial rectus muscle.
Patients 13 and 14 had an adjustable recession of the contralateral medial rectus muscle at the time of the augmented transposition surgical procedure. These two patients were operated on at a time when I was maldng the transition from transpositions to the augmented transposition.
Again, the diplopia-free field demonstrates satisfactory abduction with no loss of adduction. No residual face turn was seen in any patient.
Lateral rectus muscle palsies with lateral rectus m u s d e paresis
Table 8 shows the results of an evaluation of lateral rectus muscle palsy associated with a lateral rectus muscle paresis in four patients. Augmented transpositions were carried out on all of the palsied (paralyzed) lateral rectus muscles. With the paretic lateral rectus muscle, contralateral medial rectus muscle recessions on an adjustable suture were carried out for two patients. One patient underwent a recess/resect procedure and one patient had no procedure. These patients did well after the operation, with elimination of the deviation in the primary position in two cases and only a
Pre-Op Post-Op - - . - ' - -
LPS i~
- - - , RIGHT FIG. 3. Magnetic resonance imaging data on transposed vertical rectus muscles. The left images are near the junction of the globe and the optic nerve; the right images are near the equator. Upper images, Patient with full vertical muscle transposition only. Lower images, Case 15 with vertical muscle transposition and lateral fixation sutures from the current study. GL, Globe; IR, Inferior rectus muscle; L, left eye; LPS, levator muscle; LR, lateral rectus muscle; MR, medial rectus muscle; OW, orbital wall; R, right eye; SO, superior oblique muscle; SR, superior rectus muscle. (Upper images from Miller JM, Demer JL, Rosenbaum AR. Effect of transposition surgery on rectus muscle paths by magnetic resonance imaging. Opthalmology 1993;100:475-87. Used with permission.)
small residual deviation in the other two cases. In the two patients in whom diplopia-free visual fields were measured, no diplopia was seen in the field of the paretic eye. An average of 16 degrees of diplopia-free vision was noted in the field of the paralyzed lateral rectus. (Figure 10 illustrates the results for patient 18).
Gaze palsies
Table 9 shows the results of an evaluation of two patients with gaze palsies after they had strokes. In both patients the lateral rectus muscle was totally paralyzed; however, in patient 20 the contralateral medial rectus muscle was paretic, whereas it was totally paralyzed in patient 21. In patient 20 a significant postoperative deviation was present after the augmented transposition; the patient had a residual 30 degree left face turn. One year after the transposition, the ipsilateral medial rectus muscle was recessed 5 mm on an adjustable suture. This eliminated the
Journal of AAPOS 24 Foster Volume 1 Number 1 March 1997
FIG. 4. Patient 1 with Duane syndrome before operation.
FIG. 5. Patient 1 with Duane syndrome 3 years after undergoing a left augmented transposition.
residual deviation and face turn. In patient 21, augmented transpositions were performed on the lateral rectus muscle of the right eye and on the medial rectus muscle of the left eye. The patient's preoperative deviation and face turn was eliminated.
Delayed lateral fixation su ture placement
Table 10 shows the results of an evaluation of patient 15. A transposition without lateral fixation sutures was performed 16 years previously. This patient had subsequent medial rectus muscle surgery and the initial result was good, with the patient demonstrating 15 degrees ofdiplopia-free vision into the field of the paralyzed eye some 2 years after his initial transposition.
Over the years a recurrence of the esotropia gradually dev- eloped. Sixteen years after his initial transposition he had a 30 degree left face turn with 20 PD of residual esotropia. The patient underwent a procedure that placed lateral fixation sutures only to the transposed superior and inferior rectus muscles; as a result the deviation was reduced 80% (to 4 PD), and the head turn was reduced to 5 degrees.
Induced vertical deviations
The occurrence of vertical deviations after augmented transpositions were performed was uncommon (4 of 21 patients). All such vertical deviations were two PD or less,
Journal of AAPOS Volume I Number I March 1997 Foster
TABLE 4. Lateral rectus muscle palsy
Patient Deviation No. Age (yr) Cause Palsy Paresis (PD) Follow-up
25"
6 27 Trauma RLR LLR 65 ET 10 yr 7 57 Trauma RLR LLR 100 ET 3 me 8 59 Trauma RLR 80 ET 1 yr 9 20 Trauma RLR 35 ET 1 mo 10 19 Trauma RLR 30 ET 1 me 11 88 OVA LLR 45 ET 4.5 yr 12 55 Trauma BLR 100 ET 9 me 13 28 Trauma RLR 40 ET 1 mo 14 78 CVA LLB 35 ET 1 yr 15 19 Chordoma LLR 50 ET 16 yr 16 46 Trauma LLR RLR 45 ET 1 yr 17 43 Trauma RLR LLR 45 ET 4 yr 18 42 Trauma RLR LLR 105 ET 7 me 19 39 Trauma RLR LLR 50 ET 1 mo 20 88 CVA LLR RMR 50 ET 1 yr 21 79 CVA RLR LMR 25 ET 1 me
flLR, Right lateral rectus muscle; LLR, left medial rectus muscle; ET,, esotropia; CVA, cerebrovascular accident; RMR, right medial rectus muscle; LMR, left medial muscle.
TABLE 5. Patients with bilateral lateral rectus muscle palsy treated with augmented transposition only
rectus
Diplopia-free visual Patient Esotropia (PD) Abduction Forced abduction Adduction field (degrees) No. Before After Eye Before After Before After after ABD Total
6 65 5X R R -5 -3.5 -2 0 30 55 2H L L-4 -3 0 0 25
7 100 8 R R -5 -3 -3.5 -2* 0 18 36 L L -6 -3 -3.5 -2* 0 18
ABD, Abduction. *Three mo after surgery.
TABLE 6. Patients with unilateral lateral rectus muscle palsy treated with augmented transposition only
Esotropia Forced Diplopia-free visual Patient Lateral (PD) Abduction abduction Adduction field (degrees) No. rectus palsy Before After Before After Before After after ABD ADD Total
8 R 80 0 -6 -3 -3£ -2* 0 28 50 78 9 R 35 0 -6 -3 -2.5 0 15 50 65 10 R 30 0 -4 -3 -1 Blind OD 11 L 45 0 -4 -3 -3 No face turn
ADD, Abduction; ADD, adduction; L, left; R, right. *One year after operation.
TABLE 7. Patients with unilateral lateral rectus muscle palsy treated with augmented transposition with medial rectus muscle surgery
Lateral Medial Esotropia Patient rectus rectus (PD) Abduction Forced Adduction No. surgery surgery Before After Before After abduction after
Diplopia-free visual field (degrees)
ABD ADD Total
12 R* 100 18 -6 -3.5 -3.5 0 R Botoxt 18 0 -3.5 -3
13 R L 5 mm-ADJ 40 l x -5 -3.5 -1.5 0 14 L R 5 mm-ADJ 35 0 -4 -3 -1 0
25 50 75 28 50 78
No face turn
"13 mm lateral fixation sutures. tFive units botulinum toxin 6 weeks after augmented transposition. ABD, Abduction; ADD, adductien; R, right; ADJ, adjustable suture recession; L, left.
Journal of AAPOS 26 Foster Volume I Number 1 March 1997
! ?
FI6.8. Patient 3 with Duane syndrome 3 years after undergoing a left augmented transposition.
1:16.7. Patient 7 with bilateral lateral rectus muscle palsy. Top, Before operation. Bottom, After bilateral augmented transpositions.
FI6.8. Patient 8 with unilateral lateral rectus muscle palsy. Top, Before operation. Bottom, After right augmented transposition.
Lid fissures nar rowing
Significant lid fissure changes were not observed (Figures 4, 5, 7, 8, and 10).
D I S C U S S I O N
The use of diplopia-free visual field testing has helped demonstrate the advantages of full vertical muscle transposi-
dons over other types of transposition procedures and horizontal muscle surgery in the treatment of patients with true lateral rectus muscle palsies (paralysis) 3' s, 6 and type I Duane syndrome with a face turn. 8 Full vertical rectus muscle transpositions, usually combined with medial rectus muscle weakening, produce a larger total diplopia-ffee field and significant fusion into the abduction field. 3, ;, 6. 8 All of these
Journal of AAPOS Volume I Number I March 1997 Foster 27
"~ "i .......
L
FIG. 9. Patient 8 with unilateral lateral rectus muscle palsy 1 year after undergoing right augmented transposition.
FIG. 10. Right lateral rectus muscle palsy with left lateral rectus muscle paresis. Top, Before operation. Bottom, After right augmented transposition with left medial rectus muscle recession and left lateral rectus muscle resection.
TABLE 8. Patients with lateral rectus muscle palsy who had lateral rectus muscle paresis augmented transposition
Diplopia-free Lateral Esotropia Forced Abduction visual field
Patient rectus (PD) Abduction abduction after (degrees) no. Palsy Paresis Procedure Before After Before After Before After operation ABD ADD Total
16 R R MR 5 mm 45 0 R -2 0 -1 0 0 No face turn recess-ADJ
L L trans w/LFS L -5 -3.5 -3 0 17 R R trans w/LFS 45 0 R -5 -3 0 0 0 17 50 67
L LMR6mm recess-ADJ L -2 0 0 0 0
18 R R trans w/LFS 105 2 R -6 -3.5 -3 0 15 50 65 L L LR 4 mm L-3 0 0 0
resect LMR5mm recess ADJ
19 R R trans w/LFS 50 4 R -5 -3.5 -1 0 L L -3 -3 0 0
procedures, however, produce some loss of fusion into the adducted field (<50 degrees).
The present study demonstrates that the addition of lateral fixation sutures to the fully transposed vertical rectus muscles significantly increases the tonic abducting forces of the transposition without decreasing adduction. Clinically the importance of the tonic abducting tone was evident when decreased stiffness of the tight medial rectus muscles was observed over time in patients 7 and 8 after the augmented transposition procedure.
The effect of angmentation is seen in patient 15, who had a lateral rectus muscle palsy. This patient had an 80%
reduction in a recurrent esotropia in which lateral fixation sutures alone were added to previously transposed vertical rectus muscles.
In Table 11 the unilateral lateral rectus palsies treated in the current study are compared with a previous report 9 in which full transpositions alone were followed by ipsilateral medial rectus weakening with bomlinum toxin. The nonaugmented transposition resulted in a 50% reduction of the original deviation, whereas the augmented transposition produced a 94% reduction of the deviation. After the ipsilateral medial rectus muscle was treated with botulinum toxin in the patients who underwent nonaugmented transposition, the alignment results in the primary position of the two series became comparable.
Table 12 compares the current group of patients with type I Duane syndrome with a previous series of similar patients treated with a full vertical muscle transposition followed by a delayed ipsilateral medial rectus muscle recession. 8 The full transposition alone reduced the initial esotropic deviation and the face turn by approximately 50%. With the patients who underwent augmented transposition the esotropic deviation was reduced on the average by 85% and the face turn was eliminated in 80% of the patients (one patient had a
,Journal of AAPOS Volume I Number I March 1997 Foster 29
TABLE 12. Type [ Duane syndrome
Face turn Deviation (degrees) (PD)
Before After Before After Adduction Surgery (average) (average) (average) (average) loss >-1
Trans 8" (29) (15) 100% (30) ET (14) ET 83% 33% Trans 8. w/MR recess (15) 16% (20 ET/XT) 33% 50% Augmented trans (27) (5) 20% (27) ET (4 ET) 60% 0%
*Group II. Trans, Vertical rectus muscle transposition; ET, esotropia; MR, medial rectus muscle; XT, exotropia; Augmented trans, vertical rectus muscle transposition with lateral fixation sutures.
5 degree residual face turn). After the medial rectus muscle recession was added to the nonangmented transposition group, the results of the two studies were closer. Importantly, however, adduction loss was seen in 50% of the patients in the transposition/medial rectus muscle recession group, whereas there was no loss of adducfion in the current series. Table 13 compares the diplopia-free field of the current series of patients who had lateral rectus muscle palsy with previous transposition reports in which theJensen procedure with medial rectus muscle recession, 13 full vertical rectus muscle transposition with medial rectus muscle recession, 3 and full vertical rectus muscle transposition with medial rectus muscle bomlinum toxin was used. s With the exception of the Jensen procedure the results of the diplopia-free abduction fields were comparable. The patients in the augmented transposition group, however, with no loss of adduction, clearly had a larger total horizontal diplopia-free field by 20 to 30 degrees.
The preceding study comparison (Tables 11, 12, 13) indicates that the results of alignment in the primary position and the abduction diplopia-free fields are comparable for augmented transpositions and nonaugmented transpositions combined with medial rectus muscle weakening. However, adduction is compro- mised in the latter group, resulting in a restricted adduction diplopia-free field.
As mentioned in the introduction, vertical rectus muscle transpositions to the lateral rectus muscle produce tonic abduction forces by changing the force vectors of the transposed muscles and increasing their passive elastic forces with the lengthening of their muscle pathS 1° (Figure 2). By closing the distance between the transposed muscles and the lateral rectus muscle, the lateral fixation suture augments
both the tonic and elastic abducting forces. This produces, clinically, a net increase in abduction tone (Figure 2).
As noted in the results section, at the time of surgery the 45 degree gap between the transposed vertical rectus muscles and the lateral rectus muscle is closed anterior to the equator once the lateral fixation sutures are added (Figure 2). Posterior to the equator, this temporal shift of the vertical rectus muscles continues as seen on the magnetic resonance imaging study performed on patient 15 (Figure 3). In a previous report, xl magnetic resonance imaging demonstrated minimal lateralization of transposed vertical rectus muscles in which a posterior fixation suture was not used (Figure 3).
With use of Orbit 1.6,14 a computerized biomechanical model, Dr.Joel Miller analyzed tonic forces in lateral rectus muscle palsy (Miller J, April 1996; personal communica- tion). With a full vertical rectus muscle transposition alone, a residual esotropic deviation of 12 PD (7 degrees) is assumed. At this position the tonic abducting force produced by the transposed vertical rectus muscles is predicted to be 7.8 gm. If a lateral fixation suture is now added to the transposed muscles, the tonic abducting forces increase to 11.6 gm and the eye shifts to the primary position. This is almost a 50% increase in the tonic abducting force.
Unlike an active lateral rectus muscle that shuts off in adduction, the tonic abducting forces of the transposition and the augmented transposition remain in all fields of gaze. In 30 degrees adduction, tonic abducting forces of 8 gm for transposition and 13.5 gm for augmented transposition are estimated by simulation.
The biomechanical model predicts that an ipsilateral medial rectus muscle recession of 5 to 6 mm is needed to
Journal of AAPOS 30 Foster Volume 1 Number 1 March 1997
align the nonaugmented transposition eye to the primary position. At the same time the model predicts that with the ipsilateral medial rectus muscle recession a significant limitation of adduction will be produced because of the tonic abducting forces of the transposition.
Importantly, the model also predicts a significant limitation of adduction in the patient who has undergone augmented transposition with even a small medial rectus recession of 3 mm. This biomechanical model appears to correlate very well with the observed clinical results demonstrated in the current report. Whereas the model cannot be used to direct surgical decisions, it can provide information that is useful to a surgeon. Clearly an ipsilateral medial rectus recession is to be avoided in a patient who has undergone an augmented transposition.
It appears that the addition of equatorial lateral fixation sutures to full vertical muscle transpositions significantly augments the tonic abducting forces of the transposition without compromising adduction. This is an effective procedure even with positive forced ductions, regardless of the preoperative deviation. As long as the forced ductions are less than -4, the augmented transposition procedure usually aligns the eye to the primary position. I believe that an ipsilateral medial rectus muscle recession, even at a later date, should be avoided because of the risk of reduced adduction and possible late overcorrection. If, after the augmented transposition, significant residual deviation exists, botulinum toxin delivered to the ipsilateral medial rectus muscle or a contralateral medial rectus muscle recession would appear to be the appropriate form of treatment.
I thank David Robins, MD, forproviding the data on Patient 12 and Mark E. Jacobson, MD, for providing the data on Patient 21.
R E F E R E N C E S
1. Hummelsheim E. Weitere Ertahunger mit partietlar Sehnenuberpflanzung an der Augenmusldn. [abstract]. Arch Augenheilkd 1908-1909;62:71.
3. Rosenbaum AL, Foster RS, Ballard E, Rosales T, Gruenberg P, Choy A. Complete superior and inferior rectus transposition with adjustable medial rectus recession for abducens palsy. Strabismus 1984;2:599-605.
4. Fitzsimons R, Lee JP, Elston J. Treatment of sixth nerve palsy in adults with combined botulinum toxin chemodenervation and surgery. Ophthalmology 1988;95:1535-42.
5. Rosenbaum AL, Kushner BJ, Kirschen D. Vertical rectus muscle transposition and botulinum toxin (Oculinum) to medial rectus for abducens palsy. Arch Ophthalmol 1989;107:820-3.
6. Mc ManawayJW, Bucldey EG, Brodsky MC. Vertical rectus muscle transposition with intraoperative botaflinum injection for treatment of chronic sixth nerve palsy. Graefe's Arch Ophthalmo11990;228:401-6.
10. Scott AB. Action force tests in lateral rectus palsy. Arch Ophthalmol 1971;85:397-404.
11. Miller JM, Demer JL, Rosenbaum AR. Effect of transposition surgery on rectus muscle paths by magnetic resonance imaging. Ophthalmology 1993;100:475-87.
12. Feibel RM, Roper-Hall G. Evaluati0n ofthe field of binocular single vision in incomitant strabismus. AmJ Ophthalmol 1974;78:800-5.
13. Cline RA, Scott WE. Long-term follow-up of Jensen procedure. J Pediatr Ophthalmol Strabismus 1988;25:264-9.
14. MillerJM, Pavlovski DS. Orbit 1.5 gaze mechanics simulation. San Francisco: Eidactics, 1995.
