■The superior oblique (SO) tendon is attached to the undersurface of the superior rectus muscle by an areolar frenulum.

■The frenulum, if left intact, causes the SO tendon to move posteriorly with the superior rectus muscle when it is recessed. This can prevent the SO from becoming scarred into the superior rectus insertion when the latter is recessed. It can, however, prevent the superior rectus muscle from taking up slack when recessed with a suspension technique.

■An intact frenulum can result in the SO tendon scarring into the superior rectus insertion when the latter is resected.

■The posterior SO tenectomy procedure is e ective in collapsing small A patterns but often does not eliminate overdepression in adduction. This apparent contradiction can be explained by the change in SO vector force that results from cutting the frenulum, which is unavoidable with this surgical procedure.

14.1Introduction

The superior oblique (SO) muscle is adherent to the undersurface of the superior rectus muscle by an areolar connective tissue. Jampolsky was the first to describe the surgical significance of this local adherence, which he referred to as a frenulum [1]. The term frenulum can be defined as a membranous fold of skin that supports or restricts the movement of an organ, such as the small band of tissue connecting the tongue to the floor of the mouth. Jampolsky stated that when the frenulum is left intact, the SO tendon moves with the superior rectus muscle. Hence, when the superior rectus muscle is recessed, the SO tendon will not only retract with it but may also constrain the posterior movement of the muscle if the superior rectus is recessed, using an adjustable suture or suspension (A.K.A. hang-back) technique. He found that if the frenulum is left intact, the SO tendon via the frenulum will prevent the superior rectus muscle from achieving a recession of greater than 10 mm. Therefore, Jampolsky recommended severing the frenulum if a recession of greater than 10 mm of the superior rectus is desired to obtain the desired amount of recession. He also recommended cutting the frenulum during superior rectus resections, so as to avoid pulling the SO tendon forward with the resection, resulting in the

potential complication of the SO tendon becoming scarred into the insertion of the superior rectus muscle. Recently, studies have suggested that scarring of the SO muscle in this way can produce a complication referred to as the SO tendon incarceration syndrome [2]. This syndrome is a restrictive strabismus characterized by a hypertropia with incyclotropia of the a ected eye that is associated with scarring of the SO tendon to the nasal corner of the insertion of the superior rectus muscle. It is a very di cult surgical problem to correct and hence should be avoided if possible.

The frenulum may also be an important structure to consider during SO surgery as well. Prieto Diaz advocated cutting the frenulum to obtain maximal weakening of the SO muscle by the temporal approach [3, 4]. On the other hand, excessive stripping of the frenulum may also be an additional cause of SO tendon incarceration syndrome when weakening procedures are performed on the SO tendon [2, 5].

Several authors, cited above, have alluded to the importance of the proper handling of the frenulum for both superior rectus surgery and SO surgery. Their statements appear logical, but it is only recently that the e ect of severing the frenulum on the position of both the SO tendon and superior rectus muscle at surgery has been quantified [2]. In addition, it has been observed that the