First Intraoperative Trochlea Reconstruction

Traumatic detachment of the superior oblique muscle from the trochlea is very rare. The authors present a case of cyclovertical diplopia in downgaze due to traumatic trochlear damage where they performed surgery more than 40 years later. For the first time ever, they describe the reconstruction of the trochlea using a silicone tube, thereby regaining superior oblique muscle function.


DISCUSSION
The present case shows successful use of NACT in a case of large palpebral conjunctival squamous cell carcinoma making it amenable to resection and preservation of posterior lamella.In 2005, Murthy et al. reported a case of lower eyelid SGC with orbital extension which was treated with NACT (carboplatin and 5 fluorouracil). 6They noticed a significant reduction in tumor size and an eyelid-sparing orbital exenteration could be performed.A similar observation was noted in the study by Priyadarshini et al. 5 in one of their cases of recurrent SGC.Kaliki et al. reported a mean reduction of 74% in the tumor diameter post-NACT in a series of 10 cases of eyelid SGC. 9 Seven of these cases underwent surgery (5 resection with reconstruction and 2 orbital exenteration).Recently, Verma et al. too noted good response to NACT in their series of cases of eyelid SGC. 10 The report of NACT in ocular surface squamous neoplasia (OSSN) is quite limited and a thorough literature search revealed only 2 such articles (6 cases).Nair et al. first reported the use of NACT (cisplatin and 5-FU) in a case of OSSN with orbital extension. 7The tumor shrunk in size and the patient who would have otherwise required an eyelid-sacrificing orbital exenteration underwent an eyelid-sparing orbital exenteration.Meel et al. used NACT in 5 cases of invasive OSSN and reported that there was complete tumor regression in one case while the rest required additional surgical intervention. 8he treatment of OSSN depends upon tumor size and extension.Although the standard treatment for smaller noninvasive tumors is complete surgical resection, larger tumors can be treated with perilesional chemotherapy (mitomycin-C, 5 fluorouracil, interferon alpha) combined with surgery.Tumors with intraocular invasion require enucleation while the ones with orbital extension need orbital exenteration.In the present case, the tumor involved whole of the upper palpebral conjunctiva extending up to the fornix and the histopathology suggested stromal invasion.Perilesional chemotherapy to decrease the tumor size would have been quite difficult and complete surgical resection would have meant a complete removal of the posterior lamella which would have been quite debilitating for the patient.Hence after a discussion with the oncologist it was decided to try a course of NACT; to which the tumor responded.The present case demonstrates that NACT can be tried in large and invasive OSSN with good success.

CONCLUSION
NACT can be used in nonresectable OSSN and OSSN with orbital extension to downgrade the tumor.It may lead to significant reduction in the size of the tumor and in rare cases, it may even lead to complete tumor regression.More case studies are required for more robust evidence and clinicians should consider collaboration across the institutes.

CASE
As a third opinion, a 60-year-old male patient was referred for long-standing diplopia.His complaints started more than 40 years ago after a traumatic incident when a fishing hook damaged the superomedial part of his left orbit.Detailed old records could not be recovered but he had strabismus surgery 4 years after trauma.Ten years after the trauma, a 2 mm recession of the right inferior rectus was performed, followed by a recession of the left inferior oblique 1 year later.
Fourty years after the trauma, he was referred to our clinic for reading problems due to diplopia in downgaze.He had good visual acuity (1.5/1.5 Snellen) and normal findings on slit-lamp examination and fundoscopy.Orthoptic evaluation showed a compensating head tilt to the right with severe chin depression and intact stereoscopic vision.In primary position, without torticollis, he had 1° exo-, 1° left-hyperphoria, and 3° excyclophoria of the left eye.In downgaze, without torticollis, there was 5° hypertropia (left over right) and 7° excyclotropia of the left eye.The left over right increased in right and downgaze and the Parks-Bielchowsky 3 step test showed an increase of the left hypertropia on left head tilt.A 2− to 3− underaction of the left superior oblique muscle and 4+ overaction of the right inferior rectus muscle was found (Fig. 1).With the working diagnosis of a traumatic paresis of the left fourth cranial nerve, the patient was scheduled for a right inferior rectus muscle loop-recession and a tuck of the left superior oblique muscle.We expected this procedure to result in less torticollis and less diplopia in downgaze.
During the surgery, the superior oblique muscle was easily identified and was found not to follow its trajectory along the medial wall of the orbit but instead was running alongside the superior rectus muscle.Because the muscle was completely intact, we decided to try to reposition it to run along the medial part of the orbital roof by creating an artificial trochlea.A silicone tube, regularly used in lacrimal surgery (FCI BIKA, silicon, 0.94 mm diameter, Fig. 2A), was tied around the end of a forceps with a square knot to create a small silicone loop (Fig. 2B).A double-armed braided F2 polyester 4-0 suture (Mersilene) was tied around the knot (Fig. 2C) to secure the 3-4 mm silicone loop (Fig. 3A) and the silicone ends were cut (Fig. 3B).The contralateral (right) orbit was palpated to determine the position of the trochlea.When palpating the medial part of the anterior orbital roof of the affected (left) orbit, a very small bump indicated the position of the original trochlea.After gentle dissection, the silicone loop (Fig. 3C) was attached a few millimeters posteriorly from it using both ends of the doublearmed suture (Fig. 3D).The superior F3 oblique muscle was then disinserted from its attachment to the globe, pulled through the silicone loop, and then re-attached to its original insertion with a 10 mm elongating Vicryl 6-0 loop suture.
One week after the surgery, the patient reported a tremendous improvement.After 4 months, he was able to read without diplopia and on examination there was only a slight residual head tilt toward the right shoulder, no changes in primary gaze and upper field, a minimal left-hyperphoria in downgaze,  right inferior rectus muscle (Fig. 1).After 4 years of follow-up, the patient still experiences no diplopia in his daily activities.

DISCUSSION
This case is unique as it is the first description of a trochlea reconstruction using a silicon tube.Case reports isolated damage of the superior oblique muscle are rare and reports on surgical treatment even more.Although eye surgeons will seldom encounter a partial or total detachment of the trochlea from the orbital wall, they should be aware that trochlea repair is possible.Of equal importance, this case stresses that creativity is an important quality in a surgeon.
In this case, we initially presumed the eye movement disorder to be the result of fourth cranial nerve palsy.Although this is not uncommonly caused by trauma, usually it is only seen in severe (closed) head trauma. 1,2The most common cause of trochlear damage is trochlea detachment following orbital roof fracture.Also, when repair of the orbital roof is necessary, the trochlea needs to be detached in order to allow for orbital roof repair.When the trochlea is still attached to the periosteum, reapproximation will suffice. 3The incidence of trochlear damage by surgical or accidental trauma is unknown but it has been reported to cause acquired Brown syndrome, whereas entrapment of the superior oblique muscle is rare. 4,5ome authors have described rupture of the superior oblique muscle, and superior oblique tendon damage can even result from eyelid surgery according to Kushner et al, who described 7 cases. 6,7In case of muscle or tendon rupture, reattachment of the muscle tendon or reapproximation of the tendon can have favorable results. 7,8If restoration of the superior oblique muscle is not possible, an ipsilateral inferior oblique recession can be combined with contralateral inferior rectus recession. 9In 1971, Dow described a case where muscle fibers were exposed through the conjunctiva and surgical repair of the tendon was performed by anchoring the tendon sheet to the medial orbital wall at the trochlea. 10Another case of exposed muscle fibers was described by Harish et al.In this case, no surgery was required, suggesting that the superior oblique muscle supposedly only needs a few fibers being properly attached and running correctly to eventually restore its functionality. 11e were unable to find any literature on an intact superior oblique muscle not running through the trochlea.Also, no literature reports are available that describe the reconstruction of a trochlea or the construction of a trochlea-like structure.In case of shortening of the muscle, a loop-recession from the original muscle insertion can be used for elongation to prevent a postoperative Brown syndrome.We are the first to show that in case of trochlear damage, or in case of rupture of the superior oblique muscle/tendon where the surgeon is unable to redirect the course of the muscle through the original trochlea, a simple silicone tube can be used to regain superior oblique muscle function.

FIG. 1 .
FIG. 1. Hess screen charts preoperative (A and B) and postoperative (C and D).

FIG. 2 .
FIG. 2.Used materials: simple forceps and a silicone tube, regularly used in lacrimal surgery, FCI BIKA 0.94 mm diameter (A); tube tied around the end of forceps with a square knot to create a small 3-4 mm silicone loop (B); a double-armed braided polyester 4-0 suture (Mersilene) was inserted through the loop (C).