Pretutorial
    Assessment

Tutorial
Introduction
Materials and Methods
Results
Discussion
Conclusion
References

Slides

Augmented Hummelsheim Procedure for Paralytic Strabismus

Steven E. Brooks, MD · Scott E. Olitsky, MD · Geraldo deB Ribeiro, MD

Reprinted with permission from the Journal of Pediatric Ophthalmology and Strabismus. 2000;37:189-195.

Introduction

The surgical management of paralytic strabismus often involves the transposition of extraocular muscles to provide rotational force in the field of action of the paralyzed muscle. In addition, the transposition often is combined with a weakening procedure on the ipsilateral antagonist of the paralyzed muscle. In the case of lateral rectus palsy, for example, all^1-3 or portions⁴ of the superior and inferior recti may be transposed laterally or joined⁵ to the adjacent lateral rectus. To augment the effect of the procedure and possibly improve abduction and the field of single binocular vision, the ipsilateral medial rectus also may be recessed^1,6 or injected with botulinum toxin.⁷

Many variations in these procedures have been described,⁸ and although each has been used successfully, we believe the Hummelsheim procedure^4,8 may be the most versatile and desirable. Since it involves the transposition of only one-half of each rectus muscle and does not require division of the paralyzed muscle, it is relatively tissue- and vessel-sparing compared with other procedures. The vessel-sparing nature of the surgery is particularly important in cases in which the ipsilateral antagonist muscle also is recessed,^9,10 and in patients at higher risk for anterior segment ischemia.¹¹ In addition, if an undercorrection occurs, it may be relatively easy to reoperate and transpose the remaining halves of the adjacent muscles.

This tutorial describes a modification of the Hummelsheim procedure, which serves to potentiate the effects of the transposition. Early experience with this procedure indicates it is capable of improving ocular motility and correcting large angles of strabismus, even in cases of complete paralysis, yet retains the same versatility, tissue-sparing, and vessel-sparing features of the original procedure.

Materials and Methods

A retrospective review of eight patients who underwent a modified Hummelsheim procedure was performed. In each case, there were at least 6 weeks of follow-up information available for review (range: 6 weeks to 8 months), including complete records of the preoperative examination and operative report. An attempt was made to acquire the following data from each record: age of patient at time of surgery; diagnosis and duration of palsy; prism-cover measurements in the primary position at distance, both preoperatively and at most recent postoperative examination (nonparetic eye fixing); qualitative assessment of ductions, both preoperatively and at most recent postoperative examination; prior strabismus surgery; coexisting ocular disease; details of surgical procedure and intraoperative passive forced ductions; and complications (e.g., anterior segment ischemia or induced vertical deviation).

Our modification of the Hummelsheim procedure incorporated a titratable and symmetric amount of muscle resection from the rectus muscle halves undergoing transposition. The purpose of this modification was to augment the rotational effects of the transposition to a level at least comparable to full muscle transposition. The transposition/resection portion of the procedure was performed through either limbal or f ornix incisions, at the discretion of the surgeon. If recession of the ipsilateral antagonist of the paralyzed muscle was going to be performed (often decided on the basis of a positive traction test), the initial portions of that procedure including muscle disinsertion were performed prior to the transposition.

Following the antagonist muscle disinsertion, or if no surgery on the antagonist was performed, the paralyzed muscle was identified and inspected. The poles of this muscle were identified to determine the sites for scleral fixation of the transposed muscles. The two rectus muscles adjacent to the paralyzed muscle (e.g., the superior and inferior recti in cases of lateral rectus palsy) were then isolated. Intermuscular septum and associated fascial attachments were carefully dissected away from the muscle bellies at least 15 mm. Care was taken to completely divide attachments to the lower

SLIDE 1

The muscles were bluntly divided in half in a longitudinal fashion for approximately 12 mm to 15 mm using Stevens muscle hooks (Slide 1). A double-armed vicryl suture (6-0 Polyglactin, Ethicon, Sommerville, Conn.) was used to imbricate the muscle-half adjacent to the paralyzed muscle, using locking bites at each margin. The suture was placed at a predetermined distance posterior to the muscle insertion (i.e., the

SLIDE 2

SLIDE 3

Results

Data for all eight patients included in the study are summarized in Table 1 and Table 2. Patients ranged in age from 11 to 77 years, with a duration of muscle palsy ranging from 2 weeks to 12 years. Etiologies included third nerve palsy (n = 1), sixth nerve palsy (n = 3), combined cranial nerve palsy (n = 1), and extraocular muscle damage (n = 3). Although not quantified, passive forced ductions were positive for restriction in four of eight cases. The mean primary position deviation, either horizontal or vertical, was 54 prism diopters (D) for the seven unilateral patients (range: 25 D to 85 D) and 100 D for the bilateral patient. The surgical procedure was performed unilaterally in seven patients and bilaterally in one patient. The resection amounts varied from 4 mm to 8 mm. Surgical or pharmacologic weakening of the ipsilateral antagonist was performed in six patients. Follow-up ranged from 6 weeks to 8 months.

The mean change in primary position alignment was 52 D and ranged from 25 D to 85 D for unilateral patients. The one bilateral procedure achieved a 115-D shift in alignment. Five of the eight patients were within 15 D of orthotropia. Because of the relatively small sample size and heterogeneity in surgical procedure and etiology, it was not possible to extract a meaningful dose-response relationship for the procedure from the data. Patient age and preoperative forced ductions did not appear to influence outcome.

There were no cases of anterior segment ischemia. One patient (case 8) developed a transient hypertropia of the operated eye, which may have been due to the botulinum toxin. Mild limitation of ductions in the field of action of the antagonist muscle was noted in three of eight cases. Another patient (case 3) was noted to have aberrant innervation of the left third nerve postoperatively. Although we assumed the aberrant innervation was present preoperatively, it is possible the surgical procedure potentiated the effects on ocular dysmotility.

Discussion

Paralytic strabismus comprises a wide variety of problems characterized by weakness of one or more extraocular muscles. The inherent heterogeneity of such cases virtually ensures no single procedure will be ideally suited to all patients. Muscle transposition surgery often is required in those cases in which the degree of muscle paralysis is severe and agonist action is negligible. Numerous procedures to accomplish this purpose and subsequent modifications have been described over the years.⁸ The goals of the surgical procedure are to improve the range of single binocular vision, restore ocular alignment in the primary position, and improve cosmesis, while minimizing the risk of ocular complications.

Our modification of the Hummelsheim procedure, the key element of which involves a symmetric, titratable resection of the transposed muscle halves, has several desirable characteristics. It is a relatively straightforward procedure for the experienced strabismus surgeon. It can be graded and used with adjustable sutures if desired, and its effects may be further augmented in a uniocular procedure by recession of the ipsilateral antagonist muscle.

Our results in eight patients with a variety of diagnoses demonstrate its broad applicability and ability to correct large angles of deviation. The wide range of corrections achieved for primary position deviation is comparable to that reported in other series (Table 3).^7,12-14 This may reflect heterogeneity in the preoperative motility characteristics and heterogeneity in response to surgery, as well as differences in technique. Although these data suggest that a narrowly defined dose-response relationship may not exist, they also suggest the augmented Hummelsheim procedure may not have significant limitations with regard to preoperative angle. With more experience, it may be possible to better define the dose-response curve, and the use of adjustable sutures also may help to titrate the surgical effect in individual patients. However, given the complexity, clinical variability, and relative infrequency of cases, the development of a standardized, quantitative, experimental model system may be the best way to develop an understanding of the many variables involved in the transposition procedures.

In terms of complications, there were no cases of anterior segment ischemia in our series of eight patients. This may reflect the uncommon nature of this complication^11,15 as well as specific features of our procedure that help to prevent it. We are not aware of any published cases of anterior segment ischemia following a basic Hummelsheim procedure (i.e., half-tendon transpositions only), which only requires a sacrifice of up to two noncontiguous anterior ciliary arteries. Although simultaneous recession of the ipsilateral antagonist creates further compromise of the anterior ciliary circulation, the vessels involved (except for those in the recessed antagonist muscle) are noncontiguous, a condition that may be important in avoiding clinically significant ischemia of the anterior segment.^16,17 Determining whether the specific features of our procedure help prevent the occurrence of anterior segment ischemia will require observation of a greater number of cases.

We did not measure changes in the field of single binocular vision in our patients. Rosenbaum and colleagues⁷ stress the importance of this test to document the functional success of a transposition procedure. Although we agree this test does add potentially useful information about postoperative comitance, we are not aware of any data that demonstrate a correlation between a patient’s subjective assessment of a procedure’s success, either functional or cosmetic, and a specific change in the field of single binocular vision. Most of our patients had little to no single binocular vision preoperatively, and what little they had was markedly eccentric. Although not rigorously quantitated, correction of our patients’ primary deviation helped to provide a limited and centered field of single binocular vision.

Despite the relatively small numbers of patients within each diagnostic category, our initial results are encouraging. Although additional long-term follow-up data will be necessary to determine the stability of the postoperative alignment, several authors have specifically noted the relative stability of alignment following a variety of transposition procedures.^12-14,18

Conclusion

Our preliminary experience with the modified version of the Hummelsheim procedure suggests that it is a versatile and safe option for the management of paralytic strabismus.

References

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2. Schillinger RJ. A new type of tendon transplant operation for abducens paralysis. J Intern Coll Surg. 1959;31:593-600.
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5. Jensen CDF. Rectus muscle union: a new operation for paralysis of the rectus muscles. Transactions of the Pacific Coast Otoophthalmological Society. 1964;45:359-384.
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12. Burke JP, Ruben JB, Scott WE. Vertical transposition of the horizontal recti (Knapp procedure) for the treatment of double elevator palsy: effectiveness and long-term stability. Br J Ophthalmol. 1992;76:734-737.
13. Burke JP, Keech RV. Effectiveness of inferior transposition of the horizontal rectus muscles for acquired inferior rectus paresis. J Pediatr Ophthalmol Strabismus. 1995;32:172-177.
14. Knapp P. The surgical treatment of double-elevator paralysis. Trans Am Ophthalmol Soc. 1969;67:304-323.
15. France TD, Simon JW. Anterior segment ischemia syndrome following muscle surgery: the AAPOS experience. J Pediatr Ophthalmol Strabismus. 1986;23:87-91.
16. Olver JM, Lee JP. The effects of strabismus surgery on anterior segment circulation. Eye. 1989;3:318-326.
17. Virdi PS, Hayreh SS. Anterior segment ischemia after recession of various recti. An experimental study. Ophthalmology. 1987;94:1258-1271.
18. Lee DA, Dyer JA, O’Brien PC, Taylor JZ. Surgical treatment of lateral rectus muscle paralysis. Am J Ophthalmol. 1984;97:511-518.