Blowout fractures - clinic, imaging and applied anatomy of the orbit

Abstract

Isolated fractures of the orbital floor or medial wall are often referred to as blowout fractures (BOFs). Debilitating double vision and aesthetic deformity may affect the patients' quality of life and daily living skills, for instance, working or driving a car. The management of blowout fractures is, however, challenging, since not all fractures demand surgery. Some patients may have symptoms which subside, or may never develop symptoms. Due to a lack of evidence, there are still considerable differences in opinion on the criteria for surgery. The selection of patients for surgery is therefore crucial for optimal patient outcomes. The aims of this PhD project were to elucidate and investigate various clinical aspects of blowout fractures and to examine the anatomy of the orbital cavity, which included studying the symmetry of the two orbits, the location of orbital arteries, and the pathophysiology of blowout fractures. Several clinical specialties and basic research fields study the orbital cavity. The studies in this PhD project are based on collaboration between the Departments of Otorhinolaryngology, Ophthalmology and Radiology at the Copenhagen University Hospital Rigshospitalet and the Departments of Odontology and Anatomy (Cellular and Molecular Medicine) at the University of Copenhagen. We assessed the current treatment of blowout fractures at the Ear Nose and Throat (ENT) Department at our tertiary hospital in a retrospective study, and found that a third of the patients had persistent double vision 3 months post-trauma, irrespective of whether they had been managed surgically or conservatively (Paper I). We found that the left and right orbit are symmetrical with regards to various morphometrics of both the bony orbit and the intraorbital contents, e.g. volume, surface area and volume of fat and extraocular muscles, and distance to the ethmoidal arteries (Papers II, III and IV). This knowledge may be used in blowout fracture studies on surgical decision-making and orbital reconstruction and also in presurgical planning to avoid iatrogenic damage to the ethmoidal arteries in orbital surgery. In the first longitudinal MRI study of blowout fractures, dynamic post-traumatic changes in the intraorbital soft tissue were detected, i.e. to the best of our knowledge, for the first time indicative of an edema. We conclude that an edema subsides in the days following a blowout fracture and recommend a watchful waiting period before deciding on whether or not to operate (Paper III). The 24-12-6 mm rule of thumb determines orbital distances from the anterior lacrimal crest to the ethmoidal arteries and the optic canal. We questioned the applicability of this rule to all patients and investigated whether or not it is feasible to measure the distances on CT images. We found large inter-individual differences in the distances to the ethmoidal arteries and found that preoperative measurements on CT images are feasible and produce results with a low intra- and inter-observer variability.