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Show Journal of Nemo- Ophthalmology 20( 2): 119- 122, 2000. © 2000 Lippincou Williams & Wilkins, Inc., Philadelphia Posterior Fixation Suture Augmentation of Full- tendon Vertical Rectus Muscle Transposition for Abducens Palsy- Brad D. Simons, MD, PhD, R. Michael Siatkowski, MD, and Ann G. Neff, MD Objective: To evaluate the effect of augmenting full- tendon vertical rectus transpositions with posterior fixation sutures in patients with complete or near- complete lateral rectus palsy. Methods: Transposition of the vertical recti to the lateral rectus muscle was performed in seven patients with unilateral lateral rectus palsy ( the mean angle of preoperative horizontal deviation in primary gaze was 36.7 prism diopters ( A); range, 25- 62A of esotropia). A posterior fixation suture of 5.0 Mersilene ( Ethicon, Somerville, NJ) was placed in sclera ( 14- 16 mm posterior to the limbus) adjacent to the lateral rectus and incorporated 1/ 3 belly width of each transposed vertical rectus muscle. Results: The mean angle of postoperative horizontal deviation in primary gaze was 7.1A ( range, 0- 20A). The mean change in primary- position horizontal deviation postoperatively was 41.2A ( range, 37- 72A). Four patients were able to fuse without prism in primary gaze; three patients were orthophoric and one patient had a consecutive intermittent exotropia. The remaining three patients required prism correction to neutralize the postoperative gaze deviation. All patients had improvement in abduction. Mild limitation of adduction was noted in three patients ( range, - 0.5 to - 2.0). Conclusions: Augmenting full vertical rectus muscle transpositions with posterior fixation sutures improves the abducting effect of surgery without significant limitation of adduction. Key Words: Abducens palsy- Augmentation- Lateral rectus- Muscle transposition- Posterior fixation suture- Vertical rectus. Surgical intervention for acquired abducens palsy may be considered when ocular motility has been stable for a minimum of 6 months. Suitable surgical candidates are those patients who are intolerant of strong prisms or who have a significant anomalous head posture to promote fusion. The method of surgical treatment used ultimately depends upon the degree of weakness demonstrated by paresis of the affected lateral rectus. Incomplete pareses are best managed by horizontal rectus muscle surgery on one or both eyes. If there is Manuscript received July 29, 1999; accepted March 6, 2000. From the Bascom Palmer Eye Institute ( BDS, AGN), University of Miami, Miami, Florida; and the Dean A. McGee Eye Institute ( RMS), University of Oklahoma, Oklahoma City, Oklahoma. Address correspondence and reprint requests to Brad D. Simons, MD, PhD, Bascom Palmer Eye Institute of the Palm Beaches, 7108 Fairway Drive, Suite 340, Palm Beach Gardens, FL 33418. secondary contracture of the ipsilateral medial rectus, sufficient recession of this muscle is indicated to relieve any restriction to abduction. Alternatively, if secondary contracture has occurred more recently, the medial rectus can be injected intraoperatively with Botulinum A toxin ( Botox.; Allergan, Inc., Irvine, CA) at the time of the recess- resect procedure. When no active force can be generated by the paretic lateral rectus, a muscle transposition procedure is indicated. If mechanical restriction is present, as indicated by forced duction testing, recession of the contractured antagonist is necessary. To improve abducting ability by a transposition procedure, it is necessary to transpose the vertical muscles so that they act as abductors, or to strengthen the tertiary function of the oblique muscles to become more effective abductors. Jackson ( 1) and Hum-melsheim ( 2) may be considered the originators of muscle transposition procedures. Numerous modifications of these techniques have been described ( 3- 12). We examined the effect of augmenting full- tendon vertical rectus muscle transpositions with posterior fixation sutures in patients with complete or near- complete lateral rectus palsy. METHODS After receiving University of Miami Institutional Review Board approval, we retrospectively reviewed the charts of seven patients with complete or near- complete unilateral sixth nerve palsy who had no recovery after 6 to 12 months. No patient had positive forced ductions or medial rectus contracture. All patients underwent the same surgical procedure as described below. Information taken from the preoperative and subsequent postoperative examinations included etiology of paresis, presence or absence of anomalous head posture, angle of deviation in primary position, and visual acuity. The ocular motility examination consisted of a subjectively graded estimation ( 0- 4) of underaction (-) or overaction (+) of the extraocular muscles of each eye in the cardinal positions of gaze. Measurements of the deviation in primary position were obtained in all patients using hand- held prism bars with a standard alternate cover test at 6 m. All seven patients underwent ipsilateral full- tendon transposition of the vertical rectus muscles to the paretic 119 120 B. D. SIMONS ET Ah. lateral rectus muscle. A posterior fixation suture of 5.0 Mersilene ( Ethicon, Somerville, NJ) was placed in sclera 14 to 16 mm posterior to the limbus adjacent to the lateral rectus, incorporating 1/ 3 belly width of each transposed vertical rectus muscle ( Fig. 1). RESULTS Six out of seven patients had at least 3 months of postoperative follow- up ( range, 1- 9). The mean angle of preoperative horizontal deviation in primary gaze was 36.7 prism diopters ( A) ( standard deviation [ SD], 12.7; range, 25- 62A). The mean angle of postoperative horizontal deviation in primary gaze was 7.1 A ( SD, 7.6; range, 0- 20A). The mean difference between the preoperative and postoperative horizontal deviation ( i. e., the effect of surgery) was 41.2A ( SD, 13.8; range, 37- 72A). Four patients were able to fuse without prism in primary gaze; three patients were orthophoric and one patient had a consecutive intermittent exotropia ( patient 1). The remaining three patients required prism correction to neutralize the postoperative primary gaze deviation. All patients had improvement in abduction. Mild limitation of adduction was noted in three out of seven patients ( range, - 0.5 to - 2.0) ( Table 1). DISCUSSION Achieving acceptable postoperative alignment is often difficult in patients with a complete abducens palsy. Even a maximal recess- resect procedure will not afford good long- term results because of continued unopposed action of the ipsilateral medial rectus, eventually resulting in a recurrent esotropia. When performing three-muscle surgery on the paretic eye ( i. e., medial rectus recession and full- tendon transposition of both vertical recti), there is an increased risk of anterior segment ischemia. The Jensen procedure ( 3) is a split- tendon transfer with the adjacent muscle tied together, but not disin-serted. This procedure has the theoretical advantage of leaving some of the anterior circulation to the globe intact, although cases of anterior segment ischemia have been reported with this procedure ( 13). Additionally, with the Jensen procedure, there may be considerable scarring as a result of invasion of the muscle sheaths, FIG. 1. Full- tendon vertical rectus muscle transposition with posterior fixation suture augmentation. sometimes near the equator, thus weakening abduction and making future surgical intervention, if necessary, difficult. Sparing of the anterior ciliary vessels during a recession or resection through the use of an operating microscope and vitrectomy microinstruments is a technique that may be indicated in high- risk cases as well ( 14); however, this technique is considerably more cumbersome and time consuming than conventional surgery. Although the use of Botox to the medial rectus combined with transposition of the vertical recti can avoid an increased risk of anterior segment ischemia, postoperative vertical deviations may be induced, and the effect of Botox is only temporary. Traditionally, posterior fixation or fadenoperation has been used as an adjunct to selectively weaken the action of a rectus muscle, either alone or in combination with a recession of the same muscle ( 15,16). The posterior fixation suture creates a new functional insertion by anchoring the muscle to the sclera behind the equator at a point greater than 12 to 14 mm posterior to the original insertion site. This serves to weaken the muscle in its field of action by decreasing its arc of contact without altering the position of the globe in primary position. Several studies have demonstrated the benefit of this surgical technique in managing complicated incomitant vertical strabismus ( 17,18). Reported complications of posterior fixation sutures include scleral perforation, choroidal detachment, vitreous hemorrhage, macular edema, transient ptosis, persistent mydriasis, and granuloma formation ( 16,19- 23). Although this technique does add some additional risks, in the hands of experienced strabismus surgeons, the aforementioned complications are rare. None of these complications occurred in our series of patients. Vertical rectus muscle transposition may function in part by changing the force vectors of the extraocular muscles and increasing both passive and elastic tonic abduction forces. Moving each vertical rectus muscle to a position more parallel to the paretic lateral rectus helps the abducting vector force. A tension stretch of each vertical muscle is produced, and it increases the passive elastic forces by lengthening the muscle path abducting force. The addition of equatorial posterior fixation sutures narrows the distance between the transposed muscle and the paretic lateral rectus and thus augments the tonic and elastic abducting forces. This tonic abducting force is present in all fields of gaze. Therefore, the need for an ipsilateral medial rectus recession, with its concomitant risks of anterior segment ischemia and decreased adduction, is eliminated. Note that we achieved 37A to 72A of surgical effect without any weakening procedure of the medial rectus. The gain in vector force from this augmented transposition overcomes the traditional weakening effect that posterior fixation sutures produce by reduction in overall arc of contact. Demer et al. ( 24) have shown via high- resolution magnetic resonance imaging that dense connective tissue structures within posterior Tenon fascia near the equator of the globe adjacent to the rectus muscles act as pulleys. These pulleys are fibroelastic extraocular muscle sleeves J Neuro- Ophthalmol, Vol. 20, No. 2, 2000 AUGMENTATION OF VERTICAL RECTUS TRANSPOSITION 121 TABLE 1. Patient 1 2 3 4 5 6 7 Patients with unilateral abducens palsy Age ( y) Etiology 52 Carotid- cavernous fistula 81 Idiopathic 57 Traumatic 40 HIV/ CNS toxoplasmosis 22 Traumatic 54 Traumatic 73 Traumatic undergoing full-fixation suture ' endon vertical augmentation Abduction pre - 4.5 - 3.0 - 4.0 - 3.5 - 4.0 - 4.0 - 4.0 post - 3.0 - 2.5 - 1.0 - 2.0 - 3.5 - 3.0 - 3.5 rectus muscle Alignment ( prism pre 62 ET 25 ET 40 ET 40 ET 45 ET 45 ET 60 ET diopters) post 10 X( T) 12 XT 20 X( T) Ortho Ortho 8ET Ortho transposition Adduction post - 0.5 0.0 - 2.0 - 1.0 0.0 0.0 0.0 with posterior Follow- up ( mo) 4 1 6 9 5 17 9 Alignment, primary gaze at distance viewing; Pre, preoperative; Post, postoperative; ET, esotropia; XT, exotropia; X( T), intermittent exotropia; Ortho, orthotropia; CNS, central nervous system. consisting of dense bands of collagen and elastin suspended from the orbit and adjacent extraocular muscle sleeves by bands of similar composition. These mus-colofibroelastic tissues in and just posterior to Tenon fascia serve as compliant pulleys and determine the pulling directions of rectus muscles, serving as their functional origins. Through the use of contiguous cross-sectional magnetic resonance imaging images, additional studies have shown that posterior to the equator, there is minimal lateralization of the transposed vertical rectus muscles in those cases where a posterior fixation suture is not used. In addition, augmentation of transpositions by posterior suturing displaces the extraocular muscle pulleys substantially more than nonaugmented transpositions ( 25,26). Foster ( 11) showed that posterior to the equator, the temporal shift of the vertical rectus muscle continues when augmentation is performed. The gap between the transposed vertical recti and the lateral rectus muscle is closed anterior to the equator once the lateral fixation sutures are added, effectively increasing the tonic abducting force. The addition of posterior fixation sutures to full vertical rectus muscle transpositions has been previously evaluated in 21 patients with either unilateral or bilateral lateral rectus palsy, or with type I Duane syndrome ( 11). Four patients with unilateral abducens palsies received this augmented transposition procedure only. Three additional patients underwent this procedure combined with contralateral medial rectus recession surgery. All seven patients showed improved abduction and no loss of adduction. Foster ( 11) also compared the results of full- tendon transposition with and without augmentation. He found that nonaugmented transposition resulted in 50% reduction of the original deviation, whereas the augmented procedure produced a 94% improvement. When the undercorrected group received a postoperative Botox injection to the ipsilateral medial rectus muscle, alignment improved; however, adduction was compromised. Augmentation of full- tendon vertical rectus transposition with posterior fixation sutures improves the primary position alignment and abduction ability in patients with complete or near- complete abducens palsy. Concomitant medial rectus recession is not necessary, and it may result in decreased adduction and consecutive overcorrection, and/ or anterior segment ischemia. We recommend this procedure, as described by Foster ( 11), as the first-line surgical approach for patients with complete abducens palsy. REFERENCES 1. Jackson E. Transfer of function of ocular muscles. Am J Ophthalmol 1923; 6: 113- 23. 2. Hummelsheim E. Weitere Erfahrungen mit partieller Sehenu ( um-lau) ber- Pflanzung an den Augenmuskeln. Arch Augenheilkd 1908; 62: 71^ 4. 3. Jensen CDF. Rectus muscle union: a new operation for paralysis of the rectus muscles. Trans Pacif Coast Oto- Ophthalmol Soc 1964; 45: 359- 87. 4. Hildreth HR. The tendon- transplanting operation. Am J Ophthalmol 1953; 36: 1267- 70. 5. 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