Muscular bridge between the inferior oblique and inferior rectus muscles1☆

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Abstract

Purpose

In this study, we aimed to investigate the muscular bridge between the inferior oblique (IO) and inferior rectus (IR) muscles of the eye.

Methods

The orbits of sixty intact cadavers with no history of eye muscle or orbital disorders during life were carefully dissected to expose the muscular bridge between the IO and IR muscles. Numbers of the bridges, their length and width were recorded.

Results

We observed muscular bridge between IO and IR muscles in 6.6% of 60 orbits. They originated from the lateral side of the IR muscle, and joined to posteromedial side of the IO muscle. Mean length and width were 14.2 ± 6.3 and 1.3 ± 0.2 mm, respectively.

Conclusions

Muscular bridges were found in 6.6% of orbits dissected. We conclude that muscular bridges are important due to potential cause of failed IO or IR muscles surgery. In this respect, before surgery of the extraocular muscles, the muscular bridges should be kept in mind and demonstrated by computed tomography or magnetic resonance imaging in transverse, sagittal, and coronal planes.

Section snippets

Methods

This study was undertaken in 60 intact orbits of 30 embalmed adult cadavers (17 males and 13 females). In their records there were no histories of eye muscle or orbital disorders during life. The cause of death was unrelated to the ophthalmic region and organs of head and neck, which were carefully examined to be sure that they showed no signs of trauma, deformities, tumors, or significant volume loss. To show the arteries of the orbit, red colored latex was injected into the internal carotid

Results

In the 30 cadavers who were the source of the orbit specimens, the age at the time of death ranged from 25 to 70 years. We observed muscular bridges in 6.6% of the orbits removed and dissected. The bridge emanated from the lateral side of the IR at mean 15.2 ± 6.6 mm from the common tendinous ring and extended medially to the inferior branch of the oculomotor nerve to join the posteromedial contour of the IO muscle at a mean of 14.9 ± 3.6 mm from the point from where the IO muscle originated (

Discussion

It is commonly assumed on morphologic grounds that the eye primordia and orbital muscles always develop bilaterally; the orbital muscles derive from cephalic mesoblastic somites (synonymous with “mesenchymal/mesectodermal complexes” or the “paraxial mesoderm”), which are associated with the neural ectoderm.11, 12 Any anomaly of the extrinsic orbital muscles may be due to an early disturbance in the development of the superior and inferior mesenchymal/mesectodermal complexes,13, 14, 15, 16 for

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    Additional material for this article can be found on ajo.com. doi:10.1016/S0002-9394(03)00787-6

    1

    All the cadaver orbits were provided by the Department of Anatomy of the Cerrahpasa University of Turkey. Our department contains the records and transferring permissions given from Turkish law court.

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