Adjustable Sutures for Strabismus Surgery
Adjustable suture technique for strabismus is a method in which the surgical dosage may be altered postoperatively, typically the same day or up to a week later, with the intent to improve both short and long term stability by decreasing unintentional post-operative undercorrections or overcorrections. It remains a controversial technique, with some surgeons using nearly exclusively adjustable sutures, and with other surgeons not using the adjustable suture technique at all.
Perhaps the earliest account of an adjustable suture was by Bielschowsky in 1907 when he described creating a surgical loop, exposed through conjunctiva, which could be manipulated up to two days post operatively. The excess suture was then removed on the third postoperative day. In 1975, Jampolsky published his technique for adjustable sutures which utilized a bow-tie knot, allowing for manipulation of the muscle post-operatively, if necessary. Indications were felt to include primarily scenarios in which the desired amount of strabismus surgery was unclear, such as in patients with thyroid eye disease or previous strabismus surgery. Several years later, Jampolsky suggested that an adjustable suture technique should be considered “for almost all adult strabismus surgical corrections.” Since this time, the adjustable suture technique has become more popular, with some surgeons recommending use of the technique in most or all adults. Additionally, the technique is utilized by some surgeons during pediatric strabismus surgery.
Multiple techniques have been described since the origin of the adjustable suture. The original “bow-tie” technique remains in use today. Following disinsertion, the muscle is secured to the sclera at the insertion, and a knot is made allowing the muscle to hang-back the desired amount. A second knot is placed over top of the first, but instead of fully tying this down, a bow-tie is formed, allowing the second knot to be easily removed and the surgical dosage to be adjusted, if desired.
Perhaps more commonly performed, however, is a technique involving a sliding noose. In this technique, the muscle is secured to the sclera through the insertion as above, but the muscle suture itself is not tied down immediately. Instead, a surgical tie, typically consisting of the same material used for the muscle suture, is passed around the muscle suture and tied squarely down. Despite the surgical tie being tied securely around the muscle suture, it is able to slide freely along the length of muscle suture with effort. The muscle is then allowed to hang-back the desired surgical dosage, held in position by the sliding noose. During adjustment, if less hang-back is desired, the noose is advanced toward the muscle. If the amount of hang-back is deemed too small, the noose can be pulled away from the muscle, with careful counter traction beneath the noose, as to not pull against the sclera. Once the desired amount of surgery is confirmed, the muscle suture is tied securely on top of the noose, and both tails are cut short.
The “short-tag noose” is a variation of the basic sliding noose. This technique involves tying a sliding noose as above, but the noose is cut quite short. Furthermore, the muscle suture is also cut short, though enough length is left to allow for additional recession during the suture adjustment, if necessary. The primary advantage of this technique is that with the sutures left short, the conjunctiva is able to fully cover the surgical site. Thus, in the event that an adjustment is not needed, no further suture manipulation is necessary. Furthermore, it allows for the possibility of delayed adjustment without suture exposure in the interim. Unlike the traditional sliding noose, however, the muscle suture is never tied down at the insertion.
A third technique involves a removable noose as described by Guyton. With this technique, the muscle sutures are passed through sclera as above, but instead of simply wrapping a noose around the muscle suture, a clove hitch with three slip knots is constructed that allows not only for the noose to be adjusted to the surgical dosage, but also to be completely removed once the muscle is in proper position and has been tied down. A video demonstrating this technique is available on the online version of the paper.9 The advantage of this technique is that suture material for the noose, typically remaining beneath the conjunctiva after adjustment, can be completely removed from the eye once the adjustment has been performed.
Additional methods have also been described for adjustable sutures, including semi-adjustable and small incision technique. Furthermore, adjustable sutures have been utilized for less common procedures such as rectus muscle transpositions, Harada-Ito procedures, superior oblique tendon procedures, and others.
Despite frequent use by many surgeons, there are no large, prospective, randomized studies showing improved outcomes when using adjustable sutures in strabismus surgery compared with non-adjustable strabismus surgery. A Cochrane review was performed in 2013, searching for randomized controlled trials (RCTs) involving adjustable sutures for strabismus surgery. The review failed to identify any RCTs, instead finding mostly retrospective studies.
One example of a retrospective study was published by Tripathi and colleagues. In this study, adjustable sutures were offered to all patients. Of the 141 patients who underwent adjustable suture technique, 8.51% ultimately underwent a reoperation. Of the 302 patients who declined adjustable suture technique, 27.15% later needed a reoperation.
More recently, a large retrospective study analyzing patients age 18-89 showed a reoperation rate within one year after horizontal muscle surgery to be 5.8% with adjustable sutures, compared with 7.8% with non-adjustable sutures (P= 0.02). Interestingly, this study noted a trend for more reoperations in the adjustable suture group for vertical strabismus surgery compared with non-adjustable, though the difference was not statistically significant.
Further support for adjustable sutures was published in 2015 in a study analyzing patients with at least 4 months of follow up found that patients who achieved their target angle postoperatively were less likely to need a reoperation (84% vs 64%, p<0.0001). While this finding held true regardless of the use of adjustable or non-adjustable suture technique, patients undergoing adjustable suture technique were more likely to achieve their target angle post operatively (76% vs 54%, p<0.0001).
Unlike the use of adjustable sutures in adults, who are typically able to remain cooperative prior to and during the postoperative adjustment, the use of adjustable sutures in children often requires an additional anesthesia exposure. Logistically this may pose a problem at some hospitals, and given concern of anesthesia exposure in children, the adjustable suture technique is not as widely used in children as adults.
Despite this, adjustable suture technique in children is an option, and is used by some surgeons exclusively. Techniques employed are similar to those used in adults, though the use of the “short-tag noose” obviates the need for a second exposure to anesthesia in the event that an adjustment is not necessary.
Similarly to adjustable sutures in adults, there is no large prospective study analyzing the outcomes of adjustable sutures in children. One large retrospective study showed an improvement in surgical success from 64.5% to 79% when switching from non-adjustable to adjustable sutures in the pediatric population. A separate retrospective study showed a success rate of 88% after a minimum of 6 weeks using an adjustable technique in children.
Due to the lack of RCT’s, the use of adjustable sutures for strabismus surgery remains controversial and numerous drawbacks are frequently cited by critics of the technique. Adjustable suture technique does require more time both in the operating room and afterward, though the majority of the additional time required is during the adjustment while the patient is awake. Additionally, it is typically more expensive per individual case, though this may be offset if reoperation is avoided in the future. Other considerations include patient discomfort during adjustment or surgeon anxiety regarding the adjustment and “adjusting out of a good result.” Fortunately, most patients report minimal problems with the adjustment process.
Despite these concerns, adjustable suture technique for strabismus surgery remains a popular, though admittedly controversial, technique. While no RCT has been conducted comparing the technique to non-adjustable strabismus surgery, it remains an important option to consider, particularly in complex cases.
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