27 Stretched Scar Repair and Management of Other Weak Collagen Abnormalities



Irene Ludwig


Summary


Genetic or acquired collagen and healing disorders cause several difficulties during strabismus surgery. Sutures may not hold well in tissue and pull through. Tissues may tear during surgery and require delicate technique. Muscle paths may be displaced due to weak pulley support, causing complex strabismus patterns.


Weak wound healing after previous strabismus surgery may lead to stretched and/or migrated scars, with recurrent or consecutive strabismus. Repair techniques are presented in this chapter. Pulled-in-two syndrome with tear of the muscle at the musculotendinous junction is also discussed.




27 Stretched Scar Repair and Management of Other Weak Collagen Abnormalities



27.1 Introduction


Weak collagen can cause difficulty during strabismus surgery. Conjunctiva can tear easily in the elderly as well as younger patients with underlying collagen abnormalities. When weak connective tissue is encountered during routine strabismus surgery, it may be wise to use nonabsorbable sutures for tendon reattachment to prevent healing difficulties such as stretched scar and scar migration. Weak primary collagen and weak wound healing 1 ,​ 2 may be seen in combination, or as isolated phenomena. Patients with weak collagen may be prone to pulley displacements, which should be identified and corrected (Chapter 19, Chapter 30).



27.2 Stretched Scar Repair


Stretched scar patients have always had previous strabismus surgery, by definition. 2 ,​ 3 Prior surgical records are helpful, and will allow targeted exploration of only the previously operated muscles. If records are unavailable, then all four rectus muscles on each eye may be inspected with two small fornix incisions, such as an inferomedial incision to inspect the inferior and medial recti, and a superotemporal incision to inspect the superior and lateral rectus muscles. If the history is clear and the strabismus pattern straightforward, then complete inspection of all the muscles is not necessary. The first clue to the possibility of a stretched or lengthened scar is usually the ease of dissection and isolation of the muscle. 2 As the problem is one of weak scar tissue, conjunctival scarring is usually mild. The muscle is isolated on the Stevens tenotomy hook in normal fashion, and then placed on the larger Green hook. Retraction of the conjunctiva over the hook is usually surprisingly easy for a reoperation case due to the weak scar formation. Two other clues to the presence of stretched scar are the rolling of the muscle over the hook when the hook is pulled anteriorly (Fig. 27‑1), and the ease of lifting of the hook away from the sclera (Fig. 27‑2) due to the weak scar between tendon and sclera (Video 27.1, Video 27.2).

Fig. 27.1 Stretched scar of medial rectus, showing rolling of the insertion over the hook as the hook is pulled anteriorly.
Fig. 27.2 Stretched scar of medial rectus, showing lifting away from sclera as the muscle hook is lifted off the globe.



27.2.1 Recognizing the Stretched Scar Margins


With experience, the surgeon is usually able to identify the edge of the healthy tendon (Fig. 27‑3). If the margin is not clear, then a helpful trick is to place a 6–0 polyglactin suture through scar tissue at the insertion site on the sclera and disinsert the muscle (Fig. 27‑4). Flip the muscle over and view the undersurface (Fig. 27‑5). The demarcation between tendon and scar is usually clearer from underneath (Video 27.3). When the original muscle surgery was a resection, the scar tissue is seen to emanate directly from muscle tissue rather than tendon (Fig. 27‑6)

Fig. 27.3 Stretched scar of medial rectus. Black arrows and line indicate insertion of scar tissue on sclera; white arrows and line indicate demarcation between scar tissue and healthy tendon.
Fig. 27.4 Medial rectus prior to disinsertion. Demarcation between scar and tendon is unclear.
Fig. 27.5 Same muscle as in Fig. 27‑4, turned over and viewed from underneath. Demarcation is now easily visible (white arrows and line). Black arrows indicate suture.
Fig. 27.6 Stretched scar after medial rectus muscle was previously resected. Scar tissue emanates from muscle fibers rather than tendon (white arrows and line). Black arrows indicate attachment point of scar segment to sclera.



27.2.2 Measuring and Calculating Muscle Reattachment Position


Two measurements are taken: (1) the distance between the original insertion and the found position of attachment to sclera and (2) the length of the stretched/lengthened scar segment between the sclera and tendon. The standard surgical tables are usually effective in predicting the amount of tendon advancement needed, by adding the millimeters of excised scar tissue to the advancement of insertion toward the original insertion (Fig. 27‑7). The formula for this is T = (A + S) – X. For example, in a patient with consecutive exotropia due to previous bilateral medial rectus recessions, the standard surgical table (Table 27.1, Table 27‑2) might recommend bilateral medial rectus resections of 6 mm (X in formula). If the left medial rectus is found 7 mm from the original insertion (A), with a 4-mm segment of amorphous scar tissue between the true tendon and sclera (S), then it should be advanced 2 mm from the found position (F) to position T to obtain the effect of a 6-mm resection. If measuring from the original insertion, that distance would be AT, which is 5 mm in this example. If the right medial rectus is found 6 mm from the original insertion (A) with a 3-mm segment of stretched scar (S), it will be reattached at the 3-mm position to obtain a 6-mm effect.

Fig. 27.7 Calculating target position of the tendon during stretched scar repair. O = original insertion; F = found attachment position; S = length of stretched scar segment; A = distance from original insertion to found position; T = target position. Formula to find advancement toward original insertion from found position is T = (A + S) – X where X = recommended resection amount from surgical table (Table 27‑2). To measure from original insertion, new distance is AT.












































Table 27.1 Standard surgical dosages for horizontal rectus muscle recessions and resections for esotropia

Angle of esodeviation (prism diopters)


Recess medial rectus each eye (mm)


Resect lateral rectus each eye (mm)


15


3


4


20


4


5


25


4.5


6


30


5


7


35


5.5


8


40–50


6


8


50+


7


8


Source: Adapted from Marshall Parks’ lectures, Lancaster Course, Colby College, Maine, July 1985.




















































Table 27.2 Standard surgical dosages for horizontal rectus muscle recessions and resections for exotropia

Angle of exodeviation (prism diopters)


Recess lateral rectus each eye (mm)


Resect medial rectus each eye (mm)


15


4


3


20


5


4


25


6


5


30


7


6


40


8


6


50


9


7


60


10


8


70


10


9


80


10


10


Source: Adapted from Marshall Parks’ lectures, Lancaster Course, Colby College, Maine, July 1985.




Editor’s Comment


These tables were developed empirically by Dr. Parks over years of clinical experience. The numbers here were those in actual use at the height of his career and are slightly higher than those he published. They have served well in this author’s practice for many years, with occasional adjustments. This author prefers smaller resections to create less bulk over the insertions and will sometimes reduce the resection by 1 or 2 mm and increase the recession by the same amount. For recess/resect procedures on one eye, read across the table on each line for the numbers.

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Feb 21, 2021 | Posted by in OPHTHALMOLOGY | Comments Off on 27 Stretched Scar Repair and Management of Other Weak Collagen Abnormalities

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