Injuries to the extraocular muscles are frequent and may be associated with penetrating orbital trauma or complex orbital fractures.1–3 Muscle injuries can be in the form of a complete avulsion, flap tear, or capsular rupture, depending on the severity of injury.1–3
The management of extraocular muscle injuries is often difficult and needs to be individualized to achieve satisfactory results. We describe the clinical findings, role of imaging, surgical techniques, and results in three patients who presented with flap tears of the inferior or medial rectus muscles.
A 74-year-old man presented to the outpatient clinic with hypertropia and advanced cataract in the right eye. He had suffered trauma from a cow's horn in the right eye 10 years ago, resulting in hypertropia greater than 30° with exotropia of 30° in the injured eye (Figure 1A). Visual acuity was 20/200 in the right eye and 20/32 in the left eye. Computed tomography of the orbit (Figure 1B) showed a narrowed anterior portion of the inferior rectus muscle attached at the insertion site with the bulk of the muscle shifted posteriorly, thereby revealing the site of the torn and recessed flap of the traumatized muscle. A forced duction test revealed a tight superior rectus muscle and the eye could not be brought to primary position. The management strategy was to correct the strabismus and perform the cataract surgery in the same sitting. An 8-mm recession of the superior rectus muscle was done to ensure a free forced duction test. This was followed by exploration of the inferior rectus muscle, which revealed a thin sheath of tissue and some muscle fibers attached to the muscle insertion site while the bulk of the muscle was located far posteriorly in continuation with the muscle sheath (Figure 1C). Advancement and repositioning of the recessed inferior rectus muscle flap was then done. This was followed by phacoemulsification and foldable intraocular lens implantation. Postoperatively, the patient had a visual acuity of 20/20 and was aligned in primary gaze at 1 year of follow-up (Figure 1D).
(A) Preoperative photograph of a patient (case 1) with hypertropia greater than 30° and exotropia of 10° in the right eye. (B) Orbital non-contrast computed tomography scan showing flap tear of the inferior rectus muscle with demarcation line (arrow). (C) Intraoperative photograph of the inferior rectus muscle showing a thin sheath attached at the insertion site and the bulk of the muscle posteriorly. (D) Satisfactory alignment with residual hypertropia of 8 prism diopters postoperatively.
A 35-year-old man presented with diplopia and upward deviation of the right eye after a road traffic accident. The visual acuity in both eyes was 20/20 with a hypertropia of greater than 30° and exotropia of approximately 35° on the Hirschberg test (Figure 2A). Computed tomography of the orbit revealed an inferior rectus muscle injury with a clear demarcation line separating the posteriorly torn muscle flap from the anteriorly attached intact global fibers. A forced duction test revealed a tight superior rectus muscle. A 9-mm recession of the superior rectus muscle was done to ensure a free forced duction test. The inferior rectus muscle was explored and found to be attached to the insertion site through a thin muscle sheath with the bulk of the muscle hanging posteriorly. Although the computed tomography scan was suggestive of a flap tear, the diagnosis was established after exploring the muscle intraoperatively. The inferior rectus muscle flap was then advanced and repositioned at the insertion site. There was no vertical deviation after 6 months, but an exodeviation of 30 prism diopters prompted the patient to undergo surgery on the fellow eye (Figure 2B).
(A) Preoperative photograph of case 2 showing exotropia and hypertropia. (B) Postoperative photograph showing good alignment in primary gaze after surgery in both eyes.
A 30-year-old man presented to the strabismus clinic with exodeviation and diplopia for 1 year (Figure 3A). The symptoms started after an endoscopic surgical procedure for ethmoidal sinus mucocele. On examination, he had a visual acuity of 20/20 in both eyes with a right exotropia of 30° on the Hirschberg test and inability to adduct the eye to the midline. The rest of the ocular examination was unremarkable. Computed tomography of the orbit (Figure 3B) revealed a flap tear of the medial rectus muscle and medial wall fracture. Posteriorly, the medial rectus muscle could not be separately identified from the adjacent tissue. Results of a forced duction test for adduction were negative and the eye could be passively adducted. The recommended management option would be exploration and advancement of the medial rectus muscle flap with adjustable lateral rectus recession.3 However, in view of the bony defect in the medial wall and the intraoperative finding of extensive adhesions around the muscle, the plan was changed to a medial Nishida's procedure with adjustable lateral rectus recession.4 Nishida's procedure involved transposing the belly of the superior and inferior rectus muscles medially using non-absorbable sutures without disinserting the muscle. Good alignment was obtained during a postoperative period of 6 months (Figure 3C).
(A) Preoperative clinical photographs of a patient (case 3) with exotropia of the right eye. (B) Orbital non-contrast computed tomography scan showing thinning of medial rectus muscle with bony defect in the right orbit (arrow). (C) Orthotropia in primary gaze and improvement in adduction postoperatively.
The most common extraocular muscles suffering traumatic damage are the medial and inferior rectus muscles, possibly because the Bell's reflex places them more anteriorly, where they are more susceptible to injury.5 Causes may include orbital fractures, penetrating injuries, and blunt trauma with an intact orbital bony structure and iatrogenic injuries.1,5–9
The patients in our series presented with flap tears involving the inferior or medial rectus muscles. Ludwig and Brown's3 clinical findings helped to identify flap tears resulting in incomitant strabismus. All of our patients presented with an anteriorly thin narrow muscle still attached to the globe on imaging. Intraoperatively, we observed thinned out portions of muscle anterior to the musculotendinous junctions with the recessed flap extending posteriorly.
The split is considered to occur at the junction of the orbital and global fibers.1 Generally, there are better chances of retrieving a muscle transected during trauma compared to iatrogenic surgical injuries, in which the intermuscular septum and other adhesions have also been surgically dissected.9
Imaging helped to identify the position of the recessed flap, which was advanced in two of the patients, to restore muscle structure and function. Advancement was not attempted in the third patient in view of his severe adhesion and medial wall defect, and a medial Nishida's procedure was done to transpose force medially without compromising the vascular supply.4
There are several surgical techniques similar to anterior orbitotomy (eg, in-sheath repair, flap excision, tendon reinsertion, and tendon transpositions)5,6,8–10 described for repair of traumatized muscles. However, if a flap tear can be identified on imaging, then the first surgical aim is to restore anatomical position to achieve better functional outcomes. This may differ in certain situations where the flap tear acts as a reverse leash and causes restriction in addition to weakening of muscle function. In such cases, a flap excision may be warranted.11 Regular eye exercises involving attempted duction in the direction of the traumatized muscle were advised in our three cases postoperatively to prevent adhesion or contracture formation.
These cases elucidate that flap tears may cause not only a restriction3,11 but also a weakening of ocular movements. Preoperative imaging can aid in identification of a flap tear preoperatively and help establish a surgical plan. Management of such cases should include an attempt to reposition the flap. If this is not possible, alternative techniques should be considered. Good surgical success can be achieved in cases of flap tears, even years after trauma.
- Ludwig IH, Brown MS. Flap tear of rectus muscles: an underlying cause of strabismus after orbital trauma. Ophthal Plast Reconstr Surg. 2002;18:443–449. doi:10.1097/00002341-200211000-00011 [CrossRef]
- Ameerally PJ, Ormiston IW, Avery C. Partial avulsion of the inferior rectus: an unusual cause of diplopia after blunt orbital trauma. Br J Oral Maxillofac Surg. 2007;45:240–241. doi:10.1016/j.bjoms.2005.08.018 [CrossRef]
- Ludwig IH, Brown MS. Strabismus due to flap tear of a rectus muscle. Trans Am Ophthalmol Soc. 2001;99:53–62.
- Muraki S, Nishida Y, Ohji M. Surgical results of a muscle transposition procedure for abducens palsy without tenotomy and muscle splitting. Am J Ophthalmol. 2013;156:819–824. doi:10.1016/j.ajo.2013.05.020 [CrossRef]
- Helveston EM, Grossman RD. Extraocular muscle lacerations. Am J Ophthalmol. 1976;81:754–760. doi:10.1016/0002-9394(76)90358-5 [CrossRef]
- Bloom PA, Harrad A. Medial rectus rupture: a rare condition with unusual presentation. J R Soc Med. 1993;86:112–113.
- Partik G, Harrer S, Rossmann M, Brandstetter M, Ettl A. Avulsion of the inferior rectus muscle due to a dog-bite and reconstruction of its function. Klin Monbl Augenheilkd. 2001;218:810–813. doi:10.1055/s-2001-19693 [CrossRef]
- Plager DA, Parks MM. Recognition and repair of the “lost” rectus muscle. Ophthalmology. 1990;97:131–136. doi:10.1016/S0161-6420(90)32636-2 [CrossRef]
- MacEwen CJ, Lee JP, Fells P. Aetiology and management of the ‘detached’ rectus muscle. Br J Ophthalmol. 1992;76:131–136. doi:10.1136/bjo.76.3.131 [CrossRef]
- Ludwig IH, Clark RA, Stager DR Sr, . New strabismus surgical techniques. J AAPOS. 2013;17:79–88. doi:10.1016/j.jaapos.2012.09.019 [CrossRef]
- Raab EL, Ackert JM, Ostrovsky A. Rectus muscle flap tear as an independent cause of restricted motility. J AAPOS. 2012;16:386–388. doi:10.1016/j.jaapos.2012.03.005 [CrossRef]