2017-18 HSC Section 3 Green Book

T.N. Mansour et al. / American Journal of Emergency Medicine 35 (2017) 112 – 116

T.M. Test Predictiveness of Surgery

of IMS involvement, our study did not demonstrate a high sensitivity or speci fi city and with a PPV of only 50%. The concept of CCD came to fruition as we considered the orbit as a 30-cc shot glass or cone with the globe resting on the bottom of the glass cushioned by the IRmuscle and orbital fat. Intraoperatively, we in- variably observe that the orbital fl oor is involved at the midlevel of the IR muscle regardless of size. Hence, we speculated that the exact loca- tion of the fracture may be as important if not more important that its dimension. Also observed is a greater degree of displacement of the or- bital fl oor and intraorbital contents. Technically, we know that the fl oor of this cone measures approximately 45 mm in length. The IR muscle, which is affected in isolated BOFs, is approximately 40 mm in length. The thickest part of the muscle tends to be at the level just behind the eye or somewhat midway along the fl oor of the orbit. This would be at approximately 22.5 mm from the inferior orbital rim. The location (the “ sweet spot ” ) of the orbital fl oor “ break, ” which we suggest is just beneath the thickest part of the IR muscle, in addition to the degree of inferior fl oor displacement (volume expansion) is what causes the greatest amount instability of the orbital contents and globe. This can result in enophthalmos/globe ptosis and/or restriction. Because it is not practical or likely adequate to measure the area of the irregular fl oor defect, we set out to fi nd a much more simpli fi ed and reproducible measurement. This measurement would have to be 2-dimensional and minimize interreader variability. The posterior aspect of the globe that is perpendicular to what is typically indicated as the z -axis (anterior- posterior) was found to be roughly midway along the orbital fl oor and in the area where the IR muscle is thickest. By looking at our patient's CCD data plotted on a line graph, we noted a point or measurement above which all our patients underwent surgery and under which all our patients did not have any surgery. This number was found to be 0.8 cm and was the number that we believe is a critical difference that if determined in any isolated BOF patient will help to indicate urgency of surgical intervention. There is a direct correlation of CCD with the de- gree of inferior fl oor displacement and therefore the likely amount of orbital volume expansion as well. The higher the CCD value, the greater the newly created orbital volume. Likewise, we can infer that there is some percent change in orbital volume, if located just beneath the thickest part of the IR muscle, and it will more than likely result in enophthalmos/globe ptosis and/or restriction necessitating early surgi- cal intervention. Currently, a prospective study noting the validity of this 0.8 cm CCD value is underway. In the 33 patients who met the inclusion criteria, it was found that any value greater than 0.80 cm in the CCD was a signi fi cant enough ra- diologic fi nding that warranted surgery every single time. This differen- tial, greater than 0.8 cm, was just enough to create visually signi fi cant and debilitating instability of the globe. It was also found that interreader variability was not an issue as noted by a high κ agreement between Mansour and Taheri. The high sensitivity, speci fi city, and NPV and NPV demonstrate the bene fi t of using the CCD in assessment of

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Positive Test

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Number of Subjects

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Underwent Surgery

Fig. 6. Tamer Mansour test predictiveness of surgery using calculated CCD.

that the severity of the IR muscle displacement into the maxillary sinus was the most important predictive radiologic factor in management de- cision making. Similar to the study by Schouman et al, Zhang et al [15] also looked at enophthalmos predictability by suggesting that the overall volume of herniated orbital contents correlated signi fi cantly with the amount of enophthalmos. The idea is that if a model can be developed that predicts enophthalmos severity, then one could also justify the need for more immediate or early surgical intervention even if enophthalmos is not signi fi cant early-on. Our current methods of CT scan examination to predict the likeli- hood of surgical intervention have not reached an adequate consensus. Simply looking to see if the BOF is greater than 50% is not adequate as many of the classic textbooks seem to suggest. Our study shows that many patients who have greater than 50% BOFs do not require surgery (speci fi city of 32% and 32% PPV). A recent study by Vicinanzo et al [16] suggests that considerable interreader variability in CT measurements of BOFs can make this measurement even less accurate and reliable. They conclude that clinical fi ndings are more dependable than radiographical measurements. The importance of the IMS as a possibly overlooked radiographic en- tity was entertained based on studies involving thyroid decompression. It is well known that the IMS is a thick strut of bone that provides sup- port for themedial orbit [17] . In decompression surgery, it is widely rec- ommended that the anterior portion be left intact to reduce the incidence of globe dystopia and, hence, diplopia. With this in mind and having not been studied before, the idea of a fractured and displaced IMS as a possible risk factor for ensuing diplopia after trauma was examined. All scans were examined for any displacement of the IMS along the z -axis. Despite the theoretical validity of the importance

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Fig. 7. Craniocaudal differential (CCD). The orbital fracture of these patients measures greater than 50% of the fl oor, which typically would require surgical repair. After a physical examination by an ophthalmologist, a surgical repair was deemed unnecessary. Application of the CCD, which is obtained by calculating the difference between the caudal and cranial dimension of the orbit with the fl oor fracture (3.75) (A) from the normal side (3.28) (B), measures 0.47 cm that is below a threshold needed for surgical repair (noted at 0.8 cm).

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