Transactions 29th European Strabismological Association Meeting – de Faber (ed) © 2005 European Strabismological Association, ISBN 04 1537 211 9

Non-absorbable suture should be used for adjustable inferior rectus muscle recessions

C.F. Parsa, M. Soltan-Sanjari & D.L. Guyton

Johns Hopkins University School of Medicine, Wilmer Ophthalmological Institute, Baltimore, Maryland

ABSTRACT:

Purpose: To compare the incidence of delayed overcorrection after adjustable inferior rectus muscle recession when using polyglactin versus polyester sutures.

Methods: Inferior rectus muscle recessions performed over 23 years were reviewed. Patients were separated into two categories: recession using polyester suture versus polyglactin suture. Surgical results were evaluated by student t-test and Fisher exact test.

Results: One hundred and twenty patients underwent inferior rectus muscle recession: 64 patients using polyester suture and 56 using polyglactin suture. By the two-month post-operative exam, 5 overcorrections (hyperdeviation 3 PD) had developed in the polyglactin group, but none in the polyester group (p 0.02). At the final follow-up exam, in addition to the five already present in the polyglactin group, only one small overcorrection had occurred in the polyester group, (p 0.096). Conclusion: The use of non-absorbable suture substantially decreases the possibility of delayed overcorrection in adjustable inferior rectus muscle recession surgery.

1INTRODUCTION

Adjustable suture surgery on the extraocular muscles is increasingly common for horizontal and vertical strabismus. This technique is especially useful for vertical strabismus since the demand for surgical accuracy is greater than with horizontal strabismus.

One of the complications of extraocular muscle recession is delayed overcorrection. This seems to occur more commonly with the inferior rectus and medial rectus muscles (Kushner 1990). Recent reports have described delayed overcorrection four to six weeks after inferior rectus recession (Wright 1996), particularly in those with thyroid eye disease, and in those with adjustable suture surgery (Helveston 1987, Kushner 1990, Hudson & Feldon 1992, Sprunger & Helveston 1993, Ruttum 1995, Vazquez & Muñoz 1999). While most delayed overcorrections develop four to six weeks after surgery, after absorbable sutures lose their strength, some authors (Hudson & Feldon 1992, Wright 1996), have attributed this phenomenon to factors unrelated to suture type or surgical technique.

After experiencing several progressive overcorrections following inferior rectus muscle recessions using absorbable sutures, the senior author (DLG) initiated the use of non-absorbable suture material in 1983 in a proportion of cases, notably those where larger recessions were needed. The purpose of this study was to determine whether the rate of overcorrection after inferior rectus muscle recession decreased with the use of non-absorbable sutures.

2MATERIAL AND METHODS

This study was a retrospective review. The records of all patients who underwent inferior rectus muscle recession by the senior author (DLG) at the Wilmer Ophthalmological Institute between

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1978 and 2001 were reviewed. All patients with follow-up of less than 6 weeks, or simultaneous surgery on another cyclovertical muscle in the same or fellow eye were excluded.

Pre-operative data collected included age, sex, pre-operative diagnosis, and pre-operative deviation, which was measured with prism and alternate cover test in primary position at distance. The initial amount of recession performed was based on the size of the hypodeviation, with approximately one millimeter of recession performed per 3 PD of hypodeviation. The surgical technique was described previously for hang-back recession on an adjustable suture with the variable substitution of polyester for polyglactin sutures (Guyton 1999). In cases where the inferior rectus muscle was recessed 4 mm or more, a separate adjustable 6-0 polyglactin suture was placed into the capsulopalpebral fascia, which had been dissected from the orbital face of the muscle, and was attached to the original muscle insertion site, just temporal to the site of muscle suture re-attachment, as previously described (Pacheco et al. 1992). Moreover, since 1991, four to six millimeters of Tenon’s tissue have also been excised between the muscle and the sclera to aid in the apposition and fusion of the recessed tendon to the sclera. Since 1999, radial, rather than circumferential conjunctival incisions have been preferred. To minimize irritation from cut polyester suture ends abutting the conjunctiva, approximately four millimeters of suture material is left beyond the knot, allowing the suture “tail” to flex and be positioned facing posteriorly, away from firmly adherent limbal conjunctiva. Moreover, as of 2001, the suture insertion site has been recessed two millimeters posterior from the original insertion site to further minimize suture material abutting limbal conjunctiva.

Sutures were adjusted 6 to 8 hours following surgery, with the endpoint of adjustment being “no shift,” or an estimated 2–3 PD of undercorrection by alternate cover test. Lid sutures, if present, were adjusted at the same time. The first post-adjustment visit was usually 6 weeks after the surgery, and deviations were measured with the prism and alternate cover test.

Surgical outcomes were analyzed for all patients, and separately for the two groups with polyglactin and polyester sutures respectively. Results were assessed using a consecutive hyperdeviation equal to 3 PD or more in the primary position as indication of overcorrection (failure). Failure rates for each type of surgery were analyzed statistically.

3RESULTS

One hundred and twenty patients were identified who underwent adjustable inferior rectus muscle recession. Fifty-three (43.7%) were male and 67 (56.3%) were female. The mean age was 52.3 years.

Fifty-six patients were operated on using polyglactin sutures, and 64 using polyester sutures. The mean pre-operative hypodeviation in the polyester suture group was significantly greater

than in the polyglactin group. In addition, the polyester suture group had a mean undercorrection significantly greater than the polyglactin suture group, assessed by the student’s t-test. The overall failure rates (overcorrection) in the polyester and polyglactin suture groups were analyzed by Fisher’s exact test. There was no overcorrection six weeks after surgery in the polyester suture group, but overcorrection was present in 5 cases (8.9%) in the polyglactin suture group. This difference was statistically significant (p 0.020). By the time of the last follow-up exam, however, one overcorrection did develop in the polyester group. With this one late overcorrection in the polyester group, the difference between the two groups at the time of the last follow-up exam did not achieve statistical significance at the traditional p 0.05 level, but p 0.096 instead.

Table 1 depicts the data of the patients with overcorrection. The amounts of overcorrection were greater in the patients with polyglactin rather than polyester suture. In 105 of the 120 patients, Tenon’s tissue between the muscle and sclera had been excised. Overcorrection at the sixth week after surgery developed in three of these 105 cases (2.9%), and by the last follow-up exam in a total of four cases (3.8%), with the final addition in the polyester group.

Overcorrection had developed in two of the cases operated on without excision of Tenon’s tissue (13.3%) six weeks after surgery; this number did not change by the time of the last follow-up exam. The difference between the groups with and without Tenon’s excision at the six-week and at the final follow-up exam did not achieve statistical significance (p 0.117 and p 0.163 respectively).

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Table 1. Overcorrected cases.

Minus hypotropia in operated eye; Plus hypertropia in operated eye.

4DISCUSSION

Overand undercorrections are poorly tolerated in vertical strabismus due to limited motor and sensorial fusional amplitudes. Hang-back adjustable suture surgery enables the surgeon to improve the immediate result of strabismus surgery, but does not guarantee long-term alignment.

Some authors have attributed delayed overcorrection following inferior rectus recession to the anatomic relationship of the inferior rectus muscle with the inferior oblique muscle and linking connective tissue (Jampolsky 1978, Kushner 1990, Sprunger & Helveston 1993, Chatzistefanou et al. 2000) although alternative hypotheses have also been put forward (Hudson & Feldon 1992, Wright 1996). The supposition has been that continuing movement of this tissue complex during the healing phase may interfere with the anticipated fusion and reattachment of the inferior rectus muscle to the sclera.

A recent multipositional MRI study of the extraocular muscles in different positions of gaze also confirms that of all the extraocular muscles, the inferior rectus muscle has the shortest arc of contact with the globe (Chatzistefanou et al. 2000). Thus, when the inferior rectus is suspended backward on a hang-back suture, the tendon may not be sufficiently apposed to the sclera for proper reattachment, especially when the eye is in downgaze and the desired new insertion may then be posterior to the point of tangency between muscle and globe. Poor adhesion of the recessed inferior rectus muscle to the globe may explain the higher prevalence of delayed post-operative slippage or “underaction” of this muscle after recession. Most delayed overcorrections develop four to six weeks after surgery, the same time period when absorbable sutures lose their strength. By 1983, we had begun using polyester suture in most cases of inferior rectus muscle recession, especially those with larger vertical deviations. For similar reasons, in 1990 Kushner also had suggested the use of non-absorbable sutures (Kushner 1990).

In our study, overcorrection equal to or greater than three PD developed in six of 120 patients (5%) undergoing unilateral inferior rectus recession as the only cyclovertical surgery. Four of these six patients had restrictive strabismus pre-operatively (Table 1). Six weeks post-operatively, overcorrection developed in 5 of the 56 (8.9%) operated using polyglactin suture. In contrast, at the six-week post-op visit, no patient in the polyester suture group was overcorrected. This difference is statistically significant (p 0.02).

The mean duration of follow-up in both groups was over seven months, with a median duration of 3.5 months. By the last follow-up exam, overcorrection developed in a single patient (1.5%) in the polyester suture group, with a small 4 PD of vertical deviation. This contrasts with five patients (8.9%) in the polyglactin suture group with a mean overcorrection of 9 PD. Although the difference between the two groups at the last follow-up exam no longer achieved statistical significance (p 0.09), we shall continue to use polyester sutures. We believe the explanation for this single case of delayed overcorrection, despite the use of non-absorbable suture, lies in the fact that the adjustable noose used to determine the amount of recession is still made of absorbable polyglactin

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suture. While the polyester suture is tied in apposition to this polyglactin noose following the postoperative adjustments, the noose itself occupies a certain “volume” that, once fully dissolved, could account a further recession of up to one millimeter. Perhaps more importantly, should the permanent polyester suture knot not be carefully tied flush against the polyglactin noose due to intervening fascial and connective tissue at the moment of adjustment, even greater recession could occur once the noose material dissolves. We believe either or both of these mechanisms to be accountable for our single, mild (4 PD), delayed overcorrection with polyester suture.

Even with our liberal criterion for overcorrection of any deviation equal to or greater than 3 PD, the overcorrection rate for the absorbable polyglactin suture group was only 8.9%. This rate is lower than some other studies using adjustable suture techniques with traditional absorbable sutures (Sprunger & Helveston 1993, Vazquez & Muñoz 1999). This may possibly be explained by our supplementary excision of Tenon’s tissue between muscle and sclera, which we believe increases the likelihood of tendon fusion to sclera. Although the difference in the overcorrection rates between Tenon excision versus non-excision cases in the polyglactin group did not reach traditional statistical significance, the number of non-excision cases was perhaps too small for a meaningful comparison.

We believe this study demonstrates shows the most important factor for the prevention of delayed overcorrection after adjustable inferior rectus muscle recession is the use of nonabsorbable suture. We recommend the use of such sutures for all inferior rectus muscle recessions.

REFERENCES

Chatzistefanou, K.I., Kushner, B.J., Gentry, L.R. 2000. Magnetic resonance imaging of the arc of contact of extraocular muscles: implications regarding the incidence of slipped muscles. J AAPOS 2:84–93.

Guyton, D.L. 1999. Strabismus surgery. In: Gottsch, J.D., Stark, W.J., Goldberg, M.F. (eds). Ophthalmic Surgery, 5th edition:85–91. New York: Oxford Press Inc.

Helveston, E.M.1987. Slipped inferior rectus after adjustable suture: Orthoptic horizons. In: Lenk-Schaffer, M (ed.) Transactions of VI International Orthoptic Congress: 421–425. Harrogate: Great Britain.

Hudson, H.L. & Feldon, S.E. 1992. Late overcorrection of hypotropia in Graves ophthalmopathy. Predictive factors. Ophthalmology 99:356–60.

Jampolsky, A. 1978. Surgical leashes and reverse leashes in strabismus surgical management. Trans New Orleans Acad Ophthalmol. St. Louis: Mosby, p. 251.

Kushner, B.J. 1990. Pearls and pointers in adjustable sutures for strabismus surgery. In: Haik, B. (ed)

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Pacheco, E.M., Guyton, D.L., Repka, M.X. 1992. Changes in eyelid position accompanying vertical rectus muscle surgery and prevention of lower lid retraction with adjustable surgery. J Pediatr Ophthalmol Strabismus 29:265–72.

Ruttum, M.S. 1995. Adjustable versus nonadjustable sutures in recession of the inferior rectus muscle for thyroid ophthalmopathy. Binocular Vis Eye Muscle Surgery Q 10:105–112.

Sprunger, D.T. & Helveston, E.M. 1993. Progressive overcorrection after inferior rectus recession. J Pediatr Ophthalmol Strabismus 30:145–148.

Vazquez, C.W. & Muñoz, M. 1999. Overcorrection after adjustable suture suspension-recession of the inferior rectus muscle in non-thyroid eye disease. Binocular Vis & Strabismus Q 14:103–106.

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