Bony components of the orbital floor 

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... The orbit represents the bony cavity for the eye among other contents. The floor of the orbit is made up of orbital surface of maxilla, the orbital surface of zygomatic bone and the minute orbital process of palatine bone ( Figure 1 ). A fracture of this bony structure not involving the orbital margins is called a “pure” blow -out fracture. A blow-out fracture arises when a blunt object larger than the eye hits the orbit. 1,2 This situation often leads to incarceration of orbital tissues, especially the inferior rectus muscle and rarely the inferior oblique muscle. 3,4,5,6 There can be associated ocular injuries which may involve the anterior or posterior segments of the eye. 7,8,9,10 Two theories have been propounded to explain the mechanism of blow – out fractures. There is the hydraulic mechanism which involves the compression of orbital contents with an associated increase in the intra-orbital pressure, and the buckling mechanism theory which involves stress transmission to the orbital floor from the rim. 1,11,12,13,14,15 Orbital blow – out fracture with associated clinical features can present significant morbidity to patients which can impact on their quality of life. The management of orbital fracture is largely surgical, though some surgeons have reported good outcomes without surgery in some cases. 16,17 The outcome of interventions are influenced by a number of factors. One very important factor is the duration between injury and surgery. 18,19,20 There are a number of reports on blow-out fractures from the developed world. However, there is paucity of data on such from the developing countries, hence, the purpose of this study which is to evaluate the cases seen from two centres in our locality and the challenges encountered in managing them. METHODOLOGY This is a retrospective study involving two centres: Oculoplastic Unit, Department of Ophthalmology, University of Ilorin, Nigeria and Chaha Eye Hospital, Kaduna, Nigeria. The case notes of the patients seen at these two centres between July 2009 and March 2010, with a diagnosis of orbital blow-out fracture were reviewed. Information was also obtained from theatre records and admission notes. Five cases with a diagnosis of orbital floor blow-out fracture were seen within the study period and therefore included in the study. Information retrieved included demographic data, nature and time of injury, time lapse between injury and presentation, as well as the presence or absence of diplopia. Data on clinical examination included: visual acuity (VA) in both eyes, pupillary examination, ocular motility, Hertel exophthalmometry measurements, slit – lamp biomicroscopy, applanation tonometry, funduscopy and skin sensitivity test over the distribution of the infra-orbital nerve. Findings on computerised tomography (CT) scan were also retrieved. Informed consent was obtained from patients for the use of clinical photographs. All patients had operative interventions. The operative procedure in 3 patients involved using a 2mm thick and pliable silicone implant ( Dow Corning Ltd, USA ) following a transcutaneous, sub-ciliary incision on the lower eyelid. The dissection was carried down to the periosteum at the level of the orbital rim. A 5mm horizontal incision was made on the periosteum below the orbital rim. A vertical relaxing incision was made on either side of the periosteum and the later was reflected over a periosteal elevator, as far posterior as possible until the fracture is visualized. A gentle traction was applied on the identifiable entrapped orbital content, restoring to the orbit as much of the entrapped tissues as possible. The extent of the fracture site was determined and a silicone implant of that size was cut and placed over the defect. The implant was not sutured to the orbit, neither was any glue applied. The periosteal cut ends were sutured with 6-0 vicryl sutures, while the skin incision was closed with 6-0 silk sutures. The other 2 patients had a transconjunctival lower lid incision with lateral cantholysis and inferior canthotomy. Bone grafts for implant were harvested from the contralateral maxillary bone and the right iliac crest, respectively. The patients were followed up post- operatively until one month. Post-operative examinations included: visual acuity (VA) in botheyes, pupillary examination, ocular motility, Hertel exophthalmometry, slit – lamp biomicroscopy, applanation tonometry, funduscopy and skin sensitivity test over the distribution of the infra-orbital nerve. RESULTS There were 5 patients; 3 (60%) males and 2 (40%) females. Laterality was right eye (RE) in 2 (40%) and left eye (LE) in 3 (60%) patients. Age range was 21-26 years, with an average of 24 years. The fractures occurred during a fight in 1 (20%) patient, road traffic accident in 3 (60%) patients and occupational injury in 1 (20%). All the patients presented with poor visual acuity in the involved eye. The interval between injury and diagnosis ranged 9-120 days, average of 56days. There was limitation of up gaze and enophthalmos in all the 5 (100%) patients; diplopia was seen in 3 (60%) patients in primary position of gaze and hypoesthesia in the distribution of the infraorbital nerve in 3 (60%) patients. Associated ocular injury included macular scar, healed lid lacerations, and optic atrophy. The average time interval between injury and surgery was 48 days, and 3 (60%) of the patients had late repairs (>14 days after injury). Postoperatively, limitation of vertical eye movements, diplopia, and hypoesthesia were still observed as occurred pre- operatively; four patients had a partially reduced enophthalmos. Complications such as infection, tissue reaction to implant and extrusion were not observed. Table 1 shows the summary of findings in the patients, while Figures 2 and 3 show the photographs of one of the patients pre- and post- operatively, respectively. *LE – Left Eye, RE – Right Eye, LP – Light Perception, NLP – No Light Perception, HM – Hand Motion, LL – Lower Lid, RTI – Road Traffic Injury, VA – visual acuity DISCUSSION The orbit is a conical structure made up of the frontal, zygomatic, lacrimal, ethmoid, palatine, sphenoid and maxillary bones. The floor of the orbit is formed by the zygomatic, maxillary and palatine bones. Orbital wall fractures usually involve the inferior, medial, roof and lateral walls in that order, 21 the orbital floor being the commonest site for a fracture. 1, 21 There is a male preponderance in our series, similar to other studies. 22,23,24 This may be related to the fact that males are usually more active and may be involved in potentially physically challenging situations that may predispose them to injury. It is also remarkable that the ages of our patients were all below 30years (range 21 – 26 years), and this represents a period of active lifestyle for young adults. This is similar to findings by Chi, et al who found an age range of 20-29 years. 23 Road traffic injury (RTI) was the most common cause of the orbital fracture in our patients, responsible for two third of the cases. This is a very important cause of injuries in general and of orbital floor blowout fracture as seen in other studies. 23,24,25 Those involved in RTI may also present with associated ocular and non-ocular injuries which further contributes to the significant morbidity experienced by these patients. 4,7,9 Other causes include assault, (usually the human fist which was seen in one of our patients), sport related injuries (especially in developed countries) and falls. 23,26,27 A rare cause is nose blowing. 28 Orbital contents at risk in inferior orbital blow-out fractures include: muscles (inferior rectus muscle especially), nerves (infraorbital nerve), vessels, orbital fat and the eyeball itself. 29 Clinical presentation includes: peri- orbital ecchymosis, inability to elevate the globe, vertical diplopia especially in up gaze, hypo- or hyper-anaesthesia in the distribution of the infraorbital nerve, and enophthalmos. 30 Incarceration of the inferior rectus muscle with consequent restriction of upgaze is a frequent presentation of inferior orbital blowout fracture, and was seen in all the patients in this study. 3,25 This restrictive ...