Ridge at the medial rectus muscle insertion: A new anatomical landmark

Abstract

Background and aim: Rectus muscle insertions are usually linear or slight curved with the anterior convexity. While operating squint surgeries, we found a presence of ridge-like structure at the medial rectus insertion. None of the other rectus muscle insertions had such structure.

Materials and methods: Patients undergoing squint surgery were included in the study. All the patients had negative forced duction test for all the gazes and had comitant strabismus. The patients underwent surgery through the fornix route. All the squint surgeries were primary. None of the patients undergoing resurgery were included in the study. The ridge seen is actually an elevated curved structure and shows discontinuation of the actual medial rectus insertion. The measurements were taken from the superior and inferior end of the medial rectus muscle insertion.

Results: In a total of 76 medial rectus surgery (for recession or resection), we found the ridge was present in 68 (89.5%) of cases. The ridge was located at an average distance of 6.33 ± 1.5 mm inferior and 3.82 ± 0.9 mm superior to the superior and inferior point of medial rectus insertion, respectively.

Conclusion: We describe the presence, morphology, and measurements of a ridge as an anatomical landmark at medial rectus insertion.

Figure 1

(a) The medial rectus ridge shown in one of the patients. The ridge is seen as a discontinuation on the linear medial rectus insertion. (b) Another patient showing the similar ridge shaped discontinuity at the medial rectus insertion. The area shown by thin black line in the upper photograph is the ridge like structure on medial rectus insertion

Figure 2

(a) The superior and inferior mesenchymal complex showing the lateral rectus and medial rectus originating from the both complexes. (b) Proposed insertions of the lateral rectus and medial rectus in relation to the superior and inferior mesenchymal complex