Procedures developed in recent years using knowledge of the orbital pulleys, as well as directly correcting pulley abnormalities, include pulley posterior fixation and equatorial myopexy, developed by Clark, lateral to superior rectus myopexy from Morad, and pulley sleeve fusion and direct repair of ruptured pulleys by Ludwig. These repairs are detailed, with video demonstrations.
30 Pulley Surgeries
The procedures in this chapter are some of the newest in strabismus, and are still evolving. The first procedure developed specifically with knowledge of the muscle pulley anatomy was pulley posterior fixation, which was designed by Robert Clark. 1 , 2 , 3 This procedure was designed to duplicate the motility-restricting effect of scleral posterior fixation (faden operation) without the need for scleral sutures, and it has proven itself to be indispensable in the correction of esotropia with high accommodative convergence to accommodation (AC/A) ratio as well as deteriorated accommodative esotropia. Many children are able to control alignment with their glasses removed, enhancing their self-esteem during activities such as swimming. The next procedure, also developed by Clark, is the equatorial myopexy, which has proven effective for any displaced rectus muscle. 4 , 5
Morad has developed another technique to correct divergence insufficiency as well as heavy eye syndrome, the lateral rectus (LR) to superior rectus (SR) myopexy. 6 A slightly different, but related, technique, “pulley sleeve fusion,” has recently been developed by Ludwig, which uses the pulley sleeves of the rectus muscles rather than muscle tissue itself to secure the muscles to each other. This is essentially an attempt to reconstruct a deficient intermuscular band, such as the LR–SR band, without restricting motility. Lastly, pulley disruption following blunt trauma has long been recognized and repaired in conjunction with flap tear repair. More recently it has become clear that the pulley disruption alone (without flap tear) may occur and restrict motility, 3 , 5 , 7 , 8 , 9 and may be repaired directly.
30.1.1 Pulley Posterior Fixation (IL)
Dr. Clark designed the pulley posterior fixation procedure to take advantage of findings from a study showing that standard scleral posterior fixation did not achieve its effect as originally proposed, due to loss of the arc of contact of the muscle. It was actually caused by a mechanical restriction from the suture blocking the telescoping of the muscle through its pulley sleeve. 10 Creating a similar restriction between the muscle belly and the pulley itself allows the same restriction to be created without the need for scleral sutures. It is most effective for the medial rectus (MR), which has the most dense pulley sleeve. It can be used on the inferior and superior rectus muscles, but should not have much effect on the lateral rectus, which has weak pulley sleeve tissue. 10
The MR is isolated on a Green muscle hook in standard fashion (Video 30.1). Only dissect enough to expose the muscle and allow suture placement at its upper and lower edges, but do not disturb its connections to the pulleys. If recession is planned, perform that first. The muscle pulley is then isolated on a small (Stevens tenotomy) hook by passing the hook posteriorly along the muscle surface with the hook flat against the globe until it reaches the pulley sleeve, about 10 mm from the original insertion. The hook is rotated externally, and outward lifting force is applied to hook the pulley sleeve (Fig. 30‑1) and lift it into the field (Fig. 30‑2). A nonabsorbable monofilament suture on a large curved needle is placed through the pulley sleeve (Fig. 30‑3) and grasped with the needle holders (Fig. 30‑4) before releasing the tension from the small hook. The posterior muscle belly is then exposed with a Desmarres retractor, the other end of the suture is passed through about one-third of the muscle belly near its connections to the pulley sleeve (Fig. 30‑5), and the suture is tied (Fig. 30‑6). The procedure is repeated on the other pole of the muscle. Forced duction is performed to confirm a moderate resistance to adduction. If restriction is not felt, the suture may not have been passed deeply enough into the pulley sleeve, or posteriorly enough on the muscle belly, and should be replaced. Care should be taken when hooking the pulley sleeve to stay centered over the muscle and hook only into dense connective tissue. Hooking aggressively may perforate posterior Tenon’s capsule and cause herniation of orbital fat and adhesive syndrome. If the orbital fat pad is inadvertently entered, reposition the fat and repair the rent before proceeding.
30.1.2 Equatorial Myopexy to a Single Rectus Muscle (IL)
Equatorial myopexy is effective on any displaced rectus muscle, but the largest body of experience has been with the LR (Video 30.2, Video 30.3, Video 30.4, Video 30.5). The muscle is isolated in standard fashion on a Green muscle hook. The tension on the muscle is kept light, and the muscle belly is inspected posteriorly with a Desmarres retractor (Fig. 30‑7). The displacement may be accurately identified in this manner, provided that the tension on the hook is minimal at the time of inspection. Only minimal dissection of the muscle is performed—just enough to allow placement of the myopexy sutures. Locking 0.5-mm forceps are placed at each pole of the muscle insertion, to prevent distortion of the muscle’s length. The muscle is positioned into its normal anatomical postion with forceps. Using the insertion as a guide and aiming for slightly more than a 90-degree angle with the insertion, the myopexy sutures of 6–0 braided poyester are placed at the equator, usually 8 mm posterior to the insertion for the LR, and 6 to 7 mm back for the other rectus muscles. The suture incorporates a small bite of sclera adjacent to the desired muscle position, and the muscle bite incorporates anterior muscle fibers with a bite width of about 3 mm (Fig. 30‑8). A full thickness muscle bite is not recommended due to the rare complication of posterior muscle adhesions to sclera creating a pseudorecession effect and reducing muscle action. Clark recommends a single myopexy suture to the superior pole of the muscle in the case of the LR, but combined superior and inferior pole sutures are also proving successful, and may add stability.
When planning resection or angled resection with myopexy, do the resection first in standard fashion (Chapter 23, Chapter 34) before myopexy.