The superior rectus muscle may rarely be injured or even transected during levator resection, while injuries to the superior oblique, inferior rectus, or more commonly inferior oblique muscle were reported during fat removal in upper or lower lid blepharoplasties [3]. Injury or disinsertion of the underlying levator aponeurosis causing postoperative ptosis may occur if orbital fat is aggressively removed during upper lid blepharoplasties [4].

Most often, medial rectus (MR) [5] and rarely inferior rectus and superior and inferior oblique [6] injuries have been reported during functional endoscopic sinus surgery (FESS). Extraocular muscles may be injured during fracture repair, orbitotomies, or orbital decompression.

Four types of MR injury have been proposed from one study [5]. Type I involves a large-angle exotropia (25 prism diopters) and marked adduction deficit with relatively intact abduction and little or no entrapment (Figs. 52.1 and 52.2). These cases were typically associated with complete transection of the midportion of the MR muscle (Fig. 52.3). Early exploration with suturing of the muscle remnants [7], along with botulinum toxin injection to the ipsilateral (antagonist) lateral rectus (LR), may improve primary ocular alignment. Severe restriction in the range of horizontal ductions usually persisted. Type II cases revealed a moderate- to large-angle exotropia with combined adduction and abduction deficits suggesting partial MR transection or severe contusion with moderate MR and orbital soft-tissue entrapment. Treatment entailed early repair of the medial wall defect and release of the entrapped MR. Type III cases generally demonstrated no or only mild ocular deviation (typically small esotropia) in primary gaze but a marked abduction deficit, suggestive of a grossly intact or modestly contused muscle with marked bony entrapment. Management is by orbital exploration, release of entrapped orbital tissue, and/or repair of the orbital wall defect. Type IV cases were characterized by only mild degrees of ocular misalignment caused by muscle contusion without entrapment. Conservative management is recommended (Fig. 52.4).

In cases where there is concomitant medial and inferior rectus injury, transposition procedures may not be possible. Inactivation of the antagonist and use of an apically based orbital periosteal flap as a globe tether to center it may be an alternative [8]. Tse et al. reported the use of a suture/titanium T-plate anchoring platform system for one case of medial rectus injury with good improvement [9].