Periosteal Fixation Procedures in the Management of Incomitant Strabismus.

Managing a case of incomitant strabismus from nerve palsy or extraocular muscle loss is a major challenge. Among possible management options are globe or extraocular muscle fixation to the orbital wall coupled with weakening or strengthening of the relevant antagonist. Extraocular muscle fixation to the orbital wall can also be used in cases of abnormal synkinesis to eliminate the abnormal eye movements of a misfiring extraocular muscle, which thereby allows the use of standard paralytic strabismus surgery techniques. This review article summarizes indications and techniques of periosteal fixation procedures for incomitant strabismus.

INTRODUCTION

Management of a case of incomitant strabismus from a paralyzed or missing extraocular muscle is a major surgical challenge. Transposition of functioning muscles into the vector of the deficiency is a standard procedure but is not always an option, such as when those muscles are also abnormal or when anterior segment ischemia is a concern. In such cases alignment in primary position is possible by completely eliminating the function of the antagonist muscle by (1) Fixating it to the orbital wall or by (2) tethering the globe itself to the periosteum of the orbit on the side of the paralyzed/missing muscle. The aim of this article was to provide an overview of indications and techniques for these two procedures. We reviewed the literature in PubMed and Google Scholar using the following keywords: Globe anchor, periosteal anchor, muscle fixation, fixation procedures of the globe. The two most common indications for these two procedures are oculomotor nerve palsy and co-contraction-retraction syndrome. Other indications include congenital fibrosis of the extraocular muscle and other paralytic and restrictive strabismus.

GLOBE FIXATION PROCEDURES

Oculomotor nerve palsy

The surgical correction of strabismus in cases of complete oculomotor nerve palsy is a formidable challenge since all the muscles are paralyzed except the lateral rectus and superior oblique. Transposition procedures of either the lateral rectus muscle or the superior oblique muscle to the medial rectus muscle have been advocated by some surgeons but the results can be unpredictable, and complications and inadequate correction are not infrequent.12345 In addition, lateral rectus transposition may not be possible in cases where the lateral rectus muscle has developed contracture due to longstanding deviation. In such cases, globe fixation to the medial orbital wall periosteum is a viable surgical option. A variety of techniques and use of various materials have been described for this operation.

The concept of fixation of the globe to the orbital margin was initially developed with the idea of improving ocular motility where a silicone band was used as an eye muscle prosthesis.67 Scott et al., first used this technique for improving the rotation of the globe in cases of the lateral rectus and superior oblique muscle palsy.6 They used the silicone band to fix the globe to the adjacent periosteum.6 Bicas used silicone tubes on the antagonist muscle and fixed it to superior and inferior orbital margin on either side of the midline based on the side of the paretic muscle.7 The silicone tube acted as a sling to maintain alignment in the primary position.7 The band (or tube) would stretch on the contraction of the antagonist muscle, and on the relaxation of antagonist, the band would move the eye back to its resting position allowing some ocular rotation.7 Among the five cases described by Bicas,7 two had third nerve palsy, and three had sixth nerve palsy. Although fair postoperative alignment was achieved, the ocular rotation was limited in cases of the third nerve palsy.7 The major concern in such cases is regulation of the strength and tension of the silicone band which is a complicated mathematical exercise. While the fundamental concept remains, this technique has undergone various changes over time. Currently, oculomotor nerve palsy is the major indication for anchoring of the globe where the aim is to tether the globe and maintain it fixed in primary position rather than improve ocular motility. Various autogenous and allogenous materials have been tried, using either skin, retro-caruncular or precaruncular incisions for accessing the medial orbital wall periosteum for fixation.89101112131415161718 A summary of various techniques for the fixation of the globe is presented in Table 1.

Table 1

Various techniques for the fixation of the globe for oculomotor palsy

Salazar-León et al., first described the current technique of anchoring the globe to the nasal periosteum in 1994.8 They sutured one end of fascia lata to the medial aspect of the globe and other to the nasal periosteum.8 They used a skin incision to approach the nasal periosteum at the site of the insertion of the medial canthal tendon, where one end of the fascia lata was sutured with 5–0 silk sutures; the other end was then passed subconjuctivally and sutured to the insertion of the medial rectus muscle.8 They combined this procedure with the large lateral rectus muscle recession.8 The advantages of fascia lata are that it is well-tolerated and is inexpensive. However, the surgery is time-consuming and leaves a scar over the second site, which can cause complications. Additionally, it cannot be used in children <2-year-old.

To overcome these drawback Villaseñor Solares et al., had described the use of the superior oblique tendon as a tethering material for globe fixation.9 They procured approximately 12–14 mm of the superior oblique tendon which was fixed with mersilene suture on either side.9 The tendon length adjusted to fixate the globe in primary position in the first few cases.9 However they realized the problem of exodrift and modified their technique to leave the tethered eye in the adducted position.9 They also combined the procedure with the maximal recession of the lateral rectus and resection of the medial rectus.9 An alternative is to use the superior oblique muscle as a tethering material since it can correct the co-existing hypotropia in cases of isolated third nerve palsy and the procedure does not require a second surgical site as in cases of fascia lata. However, the technically challenging part of this approach is procuring a large superior oblique tendon and need for extensive surgery.

Goldberg et al., presenting an interesting concept of creating a periosteal flap and using it as tethering material.10 Although the previous two methods require the use of permanent sutures to fixate the material on both sides, the use of periosteal flap requires a suture on the scleral side only. The procedure involves making a conjunctival incision in the fornix overlying the paretic muscle. To create a lateral periosteal flap, the dissection is performed through the orbital fat to the lateral rim. To create an inferior periosteal flap, the dissection follows the plane of the lower eyelid retractors to the floor and orbital rim. To create a medial flap, the incision is located at the lateral edge of the caruncle. For superior flap, the orbital rim is approached through an eyelid crease incision. Once the orbital rim is reached, a wide based periosteal flap is created with dissection carried out up to the midway to the orbit. The flap is then secured with a double-armed suture through the tip. The muscle insertion is then exposed and the periosteal flap is then passed through subconjunctival space with the help of a suture and is then attached to the muscle's insertion. The major limitation of this surgery is the extensive dissection that is required to harvest the periosteal flap. In addition, the flap is friable tissue that may be damaged during the procedure.

The other autogenous materials that have been used for tethering are the temporalis fascia11 and the tendon of the medial rectus muscle itself.12 The autogenous materials have their advantages in terms of fewer chances of inflammation and extrusion. However, all the procedures described above require either extensive multiplanar orbital dissection or two-site surgery. This increases the duration of the surgery and increases postoperative inflammation.1012 Additionally, there may be a flattening of the medial canthal area and swelling on the nasal conjunctiva that may require conjunctival excision.1012 Allogenous materials that have been used for fixation of the globe, other then what we describe above, include a screw system,13 5–0 polyester suture141516 and titanium T-plate.17

Bone anchors and screws have been developed to fixate soft tissue to the bone. Advantages include precise placement for vector force determination as fixation is done directly to the bone, and the fact that bone fixation has greater strength compared to periosteum fixation.13 The disadvantages of bone anchors and screws include risk of extrusion, inflammation, infection and progressive loosening.13

Some authors have described the successful use of a nonabsorbable suture such as 5–0 polyester for anchoring the globe directly to periosteum.141516 The orbital dissection required in this procedure is less extensive (surgical technique presented below) and easier than procuring an apical periosteal flap or superior oblique tendon; also, it avoids complications seen with silicone band or screw systems.16

Recently, Tse et al., described the use of the titanium T-plate anchoring system.17 The concept is based on the principle of providing more physiological pull vector with the help of coupling suture that simulates the rectus muscle. The T-plate is implanted in the subperiosteal space with its long end pointing toward the orbital apex while the cross bar is fixed to the nasal bone with screws. The T-plate provides the anchoring base. A suture is then tied from the insertion of the muscle to the long end of the T-plate, which serves as a coupling to generate pull in the direction of the physiological vector. Saxena et al., described the use of a similar concept in 2009, for correcting hypertropia using a silicone band and a titanium plate.18 The technique does not offer any added advantage over the other methods in terms of improvement in ocular movements; however, it does has a potential to serve as a base model for development of a system that can be used as an eye muscle prosthesis. There are differing approaches to the medial orbital wall. In the past anchoring procedures have used a skin approach since it gives good exposure of the structures at the medial canthal area.19 However, the incisions placed between the medial canthus and the nasal dorsum are prone to scarring and web formation.19 To avoid the cosmetic disadvantage the other approach to reach the medial orbital wall is the transcaruncular approach in which the incision is made lateral to caruncle between plica and caruncle. Both the approaches allow the attachment of sutures anteriorly at the anterior lacrimal crest, causing delayed healing, chemosis and fullness of the medial canthal region persisting postoperatively for months.20 In the transcaruncular approach, there is edema, erythema, and irritation in the caruncle.21 Approach to the medial wall through incision in the medial Tenon's capsule has also been described in a case report.22

In designing a surgical approach to the medial orbit, the goal should be to encounter the posterior lacrimal crest with minimum dissection. Approaching the bone anterior to this structure exposes the posterior limb of the medial canthal tendon and the lacrimal sac to the risk of injury.21 The precaruncular approach initially described by Moe provides an avascular path along with a direct approach to the posterior lacrimal crest without injuring angular vessels and the medial canthal tendon. The authors have used both approaches and found that the precaruncular approach is associated with rapid healing, minimal postoperative medial canthal fullness and has obvious cosmetic advantages.

Other indications for globe fixation

While oculomotor nerve palsy remains the major indication for the fixation of the globe, the procedure has been used for other forms of strabismus including sixth nerve palsy71017 and congenital fibrosis of extraocular muscle.10

Saxena et al., have described anchoring of the globe inferiorly in a case of posttraumatic inferior rectus disinsertion.18 In this case, the globe was fixed to the floor of the orbit with a silicone band and titanium orbital plate [Figures 1 and 2]. A titanium plate was bent at 90° at one end and the other end of the plate and a silicone band was secured through one of the holes with a 4–0 prolene suture. The bent end of the plate was then fixed at the outer aspect of the orbital rim using titanium screws so that the longer part of the plate with the attached silicone band would be parallel to the orbital floor. Two single arm 4–0 prolene sutures were passed through the free end of the band and were anchored to the globe at the site of insertion of the inferior rectus. Before tying the final knot, the position of the globe was aligned at the primary position. This directed the vector of the force generated by the pull of silicone band inferiorly and posteriorly similar to the physiological force generated by the inferior rectus muscle. Postoperatively there was a marked improvement in ocular alignment with some residual exotropia. However, similar to any other anchoring procedure elevation and depression of the eye were limited.

Figure 1

Schematic diagram of periosteal fixation of the globe inferiorly with the help of titanium plate and silicone band

Figure 2

(a) Preoperative photograph of the patient with posttraumatic inferior rectus laceration, before undergoing inferior globe fixation, (b) postoperative picture of the same patient

All the above-mentioned globe fixation procedures provide similar results in terms of ocular alignment. They vary only in terms of ease and duration of surgery, and the complications related to the tethering material used. The authors have been using a precaruncular approach to reach the medial periosteum and use a nonabsorbable suture as a tethering agent. The procedure is explained below.

Surgical technique used by the authors for globe anchoring oculomotor nerve palsy

Under anesthesia, forced duction test is repeated to confirm the tight lateral rectus muscle. Using the limbal conjunctival incision 12–16 mm of the lateral rectus muscle recession is performed. The amount of recession is adjusted to ensure a free forced duction test for adduction intraoperatively.

The caruncular area is exposed using stay sutures through the skin near the medial canthus. After identifying and dilating the two puncta using Nettleship's punctum dilator, Bowman's lacrimal probes are placed to secure the canaliculi. The probes act as landmarks to identify the canaliculi so that they are not inadvertently damaged during surgery. To decrease intraoperative bleed and postoperative pain, 0.2–0.5 ml of 1:1000 adrenaline with 2% xylocaine is injected in the caruncular area. Subsequently a curved superficial incision (approximately 7–8 mm) is created at the junction of conjunctiva and canthal skin [Figure 3a]. After anatomical localization of the lacrimal system with the help of lacrimal probes, blunt dissection is performed posteriorly and nasally to reach the periosteum posterior to the posterior lacrimal crest [Figure 3b]. Through the exposed periosteum, two double-armed 5–0 nonabsorbable-coated braided polyester sutures are passed [Figure 3c], and a gentle pull is applied to the sutures to test the strength of the tissue bite. The lacrimal probes are then removed. Using a limbal conjunctival incision, the medial rectus muscle is hooked and dissected [Figure 3d]. Through this incision, straight tenotomy scissors are passed towards the medial canthus to create a tunnel [Figure 3e]. Blunt tipped serrated forceps are passed through this incision, and the needles of ethibond sutures are pulled out laterally adjacent to the medial rectus muscle [Figure 3f]. These sutures are then anchored to the sclera on either end of the medial rectus muscle. The sutures are tightened to leave esotropia of about 10–15° intraoperatively. The conjunctival incisions are sutured separately using 8–0 polyglactin. At the conclusion of surgery, syringing is performed to confirm the patency of the lacrimal system. Figure 4a and b show the preoperative and the postoperative photograph of a patient of complete occulomotor nerve palsy.

Figure 3

Schematic diagram showing medial periosteal fixation of the globe. (a) Incision at precaruncular area, (b) exposure of posterior lacrimal crest, (c) Passing of nonabsorbable sutures through posterior lacrimal crest, (d) exposure of medial rectus muscle through limbal conjunctival incision, (e) creating a subtenon tunnel with the tenotomy scissors, (f) the nonabsorbable suture are passed medially with blunt forceps

Figure 4

(a) Preoperative photograph of the patient of complete third nerve palsy, (b) postoperative photograph of the same patient

The vertical strabismus can be corrected simultaneously either by adjusting the insertion of the nonabsorbable suture below or above the insertion of the medial rectus muscle or by operating on the vertical muscles.

Globe fixation procedure typically requires weakening procedures of the antagonist muscle (i.e., the muscle working opposite to the paralyzed/damaged muscle). This antagonist muscle typically has undergone secondary fibrotic changes, and any surgical attempt to regain ocular alignment requires its weakening. The same is true for restrictive strabismus such congenital extraocular muscle fibrosis, where profound weakening of the muscle which is an antagonist to the nonfunctioning muscle is required (typically the lateral rectus). However, it is not uncommon that the even supramaximal recession is not sufficient and leads to recurrence. The most common cause of unsatisfactory results in cases of oculomotor nerve palsy and exotropic Duane retraction syndrome (DRS) is the tight lateral rectus muscle.232425 Although myotomies or myectomies may completely detach the muscle from the globe, the results are unpredictable due to the muscle's tendency to reattach to the globe.26

A complete inactivation of lateral rectus muscle force by orbital wall fixation rather than conventional strabismus surgery eliminates all residual lateral rectus function and prevents reattachment to the globe. As the muscle is still retrievable, the procedure is reversible if required. Another indication for the procedure is the deactivation of an inappropriately-innervated muscle and thus conversion of a complicated abnormal co-contraction case into a more straightforward paralytic strabismus (e.g., in some cases of Duane syndrome). Table 2 summarizes the various indications and results of orbital fixation of extraocular muscle.

Table 2

Extraocular muscle fixation to the orbital wall

Surgical technique

Using a limbal conjunctival incision, the lateral rectus muscle is exposed and isolated on a muscle hook. A nonabsorbable suture is woven, and the muscle is disinserted. The globe is then retracted medially, and a blunt dissection is performed outside the muscle cone to expose the adjacent periosteum approximately 5 mm posterior to the lateral orbital rim. The muscle is then attached to the adjacent orbital periosteum. The Tenon capsule is then closed over the muscle with 8–0 polyglactin, to avoid any reattachment [Figure 5].

Figure 5

Schematic diagram of the periosteal anchoring of the lateral rectus muscle to the lateral periosteum

Velez et al., retrospectively evaluated the results of lateral rectus orbital fixation in three cases of oculomotor nerve palsy and two cases of DRS.27 For oculomotor nerve palsy they combined the procedure with large medial rectus muscle resection.27 For Duane syndrome, they combined the procedure with a partial vertical rectus muscle transposition (VRT).27 In oculomotor nerve palsy cases, the mean preoperative and postoperative deviation was not significantly different, nor was there any significant change in head posture. Both the cases of Duane syndrome showed improvement in the amount of deviation as well as head posture.

Sukhija et al., suggested a modification of periosteal anchoring of the lateral rectus muscle by fixating it to the lateral canthal tendon for exotropic Duane syndrome.31 They retrospectively compared the results of this procedure with Y split recession and found that both are equally effective.31

Sharma et al., prospectively evaluated the effect of periosteal fixation of the lateral rectus in exotropic Duane syndrome.30 They compared periosteal fixation of the lateral rectus muscle alone with periosteal fixation combined with partial VRT where the temporal halves of vertical rectus muscles were used to reduce the risk of anterior segment ischemia. There was a significant improvement in ocular movements, globe retraction, and upshots and down shoots in both groups. There was a greater improvement in abduction in the group that underwent partial VRT. The complete deactivation of the lateral rectus muscle appears to be an effective procedure to eliminate the paradoxical innervation of the lateral rectus during adduction. This improves the exodeviation in the primary position and hence, anomalous head posture, as well as the range of adduction. The abduction can be improved by performing partial VRT after periosteal fixation of the lateral rectus.

In cases of the third nerve palsy, it needs to be combined with either a supramaximal resection of the medial rectus muscle or the medial anchoring of the globe. Velez et al., in their study showed that in cases of third nerve palsy there was no improvement of adduction while there was residual abduction despite inactivation of the lateral rectus muscle and supramaximal resection of the medial rectus muscle, which suggest that the connective tissue also undergo secondary contracture in cases of longstanding deviation in general, and specifically, oculomotor nerve palsy.27 There was no difference in the preoperative and postoperative deviation with the above-mentioned procedure. Morad et al.'s, retrospective case series reported better results for their cases of oculomotor nerve palsy.28 In a recently published case series, fixation of both the rectus muscles to the periosteum was done to achieve satisfactory alignment.32 However it should be noted that medial anchoring of the globe along with the lateral rectus muscle weakening in the form of supramaximal recession is an effective procedure.

The principle of profound weakening by periosteal fixation has been applied to other muscles as well. Ela-Dalman et al. reported the results of the fixation of the inferior oblique muscle in cases of superior oblique palsy (SOP), primary inferior oblique overaction with exotropia and dissociated vertical deviations (DVD). There was marked improvement in the V pattern and inferior oblique over action.29 The cases with primary inferior oblique overaction and DVD showed marked improvement in hypertropia in the primary position.29 However the cases with SOP did not show much change in hypertropia, neither there was significant change in torsion.29 Postoperative complication included Y pattern exotropia in two patients.29

CONCLUSION

Globe fixation to the medial periosteum along with supramaximal recession of the lateral rectus muscle is a preferred procedure in the treatment of complete oculomotor nerve palsy. The procedure should be reserved for cases where there has not been any recovery. In these latter cases attempts should be made to preserve the ocular movements with other surgical options. Of the various procedures described for anchoring of the globe, no single procedure is better than the other in terms of ocular alignment. They differ in their ease, duration of surgery and the tethering material used. The fixation with the nonabsorbable suture through precaruncular approach is the author's procedure of choice because of its ease and shorter duration.

The orbital fixation of the lateral rectus muscle is emerging as a preferred surgical procedure for exotropic DRS because it completely abolishes the action of the misinnervated lateral rectus and corrects exotropia simultaneously. However, in the absence of definitive results from a randomized control trial comparing it to Y split and recession of the lateral rectus either option can be used.