Exploring the lacrimal sac fossa: anatomical insights for optimizing external dacryocystorhinostomy

External dacryocystorhinostomy is considered the gold standard for treating epiphora resulting from nasolacrimal duct obstruction. Despite the success of the procedure, a visible facial skin scar often undermines the surgical outcome. The aim of this study is to prevent visible facial scarring following oculoplastic interventions by improving the insight into the anatomical details of the lacrimal sac fossa (LSF), lacrimo-maxillary suture (LMS), periosteum, and lacrimal diaphragm.

The study examined the medial canthal region of eighty adult male sspecimens to investigate the landmarks associated with the LSF. The periorbital area was dissected to reveal the skin, subcutaneous tissues, orbicularis oculi muscles, and the lacrimal drainage system, all of which were detached from their bony attachments. The lengths of the lacrimal crests, midline length, midline width, dorsolateral angle, composition of the LMS, and area of the LSF were evaluated using the ImageJ program. The LSF was categorized into six distinct shapes: ellipsoid, oval, inverted pear, straight pear, oblique hammer, and quadrangular.

The measurements of the anterior lacrimal crest averaged 2.2 ± 0.4 cm, the posterior edge 2.0 ± 0.4 cm, and the midline 1.9 ± 0.3 cm. The area of the LSF was found to be 1.4 ± 0.5 cm². The analysis reveals that about half of the LSF consists of equal parts maxillary and lacrimal bones. The dorsolateral angle values where the maxilla and os lacrimale equally contributed to the structure of the LSF were higher than those completely formed by the maxilla. The shapes of the LSF were classified as ellipsoid (35%), oblique hammer (21.3%), oval (13.7%), inverted pear (15%), with the ellipsoid type being the most frequent. The anterior lacrimal crest length of the oval-shaped LSF was shorter than that of the oblique hammer-shaped LSF. Similarly, the posterior lacrimal crest of the oval-shaped LSF was shorter than that of the oblique hammer-shaped LSF. The midline length of ellipsoid, oval, and inverted pear-shaped LSFs was shorter than that of oblique hammer-shaped LSFs.

The length of anterior lacrimal crest and LMS are suggested as the most reliable navigational references for locating the type of LSF. Mastery of the transversal and vertical orientation of the LSF is essential for surgeons performing oculoplastic surgeries tailored to individual anatomical variations. This study is clinically valuable as it underscores the necessity for oculoplastic surgeons to adapt surgical techniques in response to anatomical differences encountered during surgery.