Reconstruction of orbita floor with polydioxanone plate
To lizuka ~, P. Mikkonen ~, P. Paukku 2, C. Lindqvist 1 1Departments of Oral & Maxillofacial Surgery and 2Radiology, Helsinki University Central Hospital, Finland
T. Iizuka, P Mikkonen, P Paukku, C. Lindqvist: Reconstruction of orbital floor with polydioxanone plate. Int. J. Oral Maxillofae. Surg. 1991; 20: 83-87. Abstract. The use of a polydioxanone (PDS) plate for orbital reconstruction was evaluated in 20 patients with various traumatic defects of the orbital floor. The follow-up time was 9 to 45 months (mean 20.4 months). A CT scan was obtained in 13 patients. Radiographic analysis showed that in 12 of the 13 patients there was new bone in the orbital floor. Clinically, most patients had transitory postoperative diplopia (lasting for a mean of 29 days) because of overcorrection. Only 2 patients, however, suffered from persistent diplopia. In one patient, abducens nerve paresis was the cause. It is concluded that PDS is suitable for orbital floor reconstruction, at least in cases in which defects do not exceed 1-2 cm in diameter. Overcorrection seems necessary. The material is well tolerated, is totally absorbed and appears to be replaced by bone in nearly all cases.
Fractures of the orbital floor can present in various forms. It can be a direct extension of an orbital rim fracture, part of a fracture of the zygomatic complex, or a component of the Le Fort II or III variety of middle third fracture. It can also be isolated, in the absence of fracture of the orbital rim (blow-out fracture) 18. It varies from a simple fissural fracture to comminution and complete dehiscence of the floor. Indications for orbital floor repair are diplopia which fails to resolve, substantial herniation of orbital contents into the antrum, incarceration of tissue in the fracture, and enophthalmos exceeding 3 mm 1°. Kmsm,~R & ROWE18 have expressed the view that a defect > 1 cm in diameter, as measured by polytomography, is an indication for surgical repair. A defect measuring < 1 cm in diameter but > 5
mm necessitates surgery only if there are positive clinical signs of prolapse, as shown by a positive forced duction test. According to PRENDERGAST & WILDES 17, however, the presence or absence of clinical orbital findings, apart from enophthalmus or diplopia is an unreliable indicator of the degree of orbital floor injury. Persistent diptopia from zygomatic fractures correlates significantly with a floor defect > 10 mm in diameter and with the existence of comminution or herniation, or with the simultaneous occurrence of both 13 (Fig. 1). Concern regarding late development of diplopia and enophthalmos is unjustified if there is no marked impairment of vertical eye movements within 14 days of the accident s. It is obvious that in a large number of cases of orbital floor fractures explo-
Key words: orbital fractures; orbital defects; bio-absorbable plates; polydioxanone plate Accepted for publication 26 September 1990
Fig. 2. Bowl-shaped PDS plate, dimensions 28 x28x 1 mm. ration of the orbital floor is essential but that reconstruction poses a number of problems. The defect must be repaired so that orbital herniation and entrapment of extraocular muscles are prevented. At the same time, unaesthe-
Fig. 1. Example of typical untreated "blowout" fracture. A woman of 40 sustained a facial injury in a traffic accident 6 months earlier. The fracture was not initially diagnosed and operated on. The patient has zygomatic asymmetry and severe enophthalmos (A). CT scan shows a Now-out fracture in the coronal plane and prolapse of the orbital content into the maxillary sinus (13).Asymmetry of the eye globes is clearly evident in the horizontal plane (C).
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Fig. 3. Intraoperative view: defect of the orbital floor (A). The defect is covered with a PDS plate, which is fixed with a suture of PDS to the orbital rim (B).
absorbable polyester which has been used for several years as a suturing material. It has recently also been marketed as a plate for orbital floor reconstruction (PDS-Schale fiir Orbitaboden, Ethicon, Hamburg-Norderstedt, Germany). The use of PDS has not previously been evaluated in any follow-up study concerning patients with fractures of the orbital floor. F r o m the beginning of 1986 to the end of 1988 we used this material instead of a bone graft in 20 cases when the use o f lyophilised dura was considered inadequate for bridging an orbital floor defect. The aim of this study was to evaluate the material clinically and radiographically, with special emphasis on its reported complete absorption within 10-12 weeks 12.
Material and methods
Fig. 4. CT scan on follow-up of patient No. 3, 19 months after fracture of Le Fort type. Normal bone formation in the reconstructed right orbital floor (arrow) and symmetry of the orbital plane.
tic enophthalmos must be avoided. Previously, orbital floor fractures were stabilized by packing the maxillary sinus with gauze or a balloon. Those techniques have, however, proved inadequate in some cases. Open reduction and reconstruction have gained in popularity. Although autogenous bone has been the material of choice, unpredictable resorption and donor-site problems have been encountered 6,19. A number of alloplastic materials have, there-
fore, been used as replacements for bone. Criteria for ideal reconstruction material include 1) biocompatibility, making removal unnecessary, 2) lack of carcinogenity, 3) strength and rigidity, 4) capacity for being sculpted during the operation, 5) ease of anchoring in position, 6) capacity for sterilization and 7) capacity for use for single stage reconstruction of extensive defects1,12,13,lS. Polydioxanone (PDS) is a completely
A PDS plate was used for orbital floor reconstruction in 20 patients in the Department of Oral and Maxillofacial Surgery, Helsinki University Central Hospital, Finland, between 1986 and 1988. The indication for surgical intervention was the presence of an orbital floor defect greater than 10 mm in diameter with perforation to the maxillary sinus and an otherwise reconstructable or intact orbital rim. Larger defects with extensive comminution were reconstructed using bone grafts from the iliac crest. Seventeen of the 20 patients were available for clinical examination and 13 patients for a radiological examination on average 20 months (range 9 to 45 months) after operation. In 8 cases fractures of the Le Fort type and in 10 cases zygomatic fractures were associated with the comminuted orbital floor fracture. Two patients had an isolated fracture of the orbital floor only (blow-out fracture). The mean age of 17 male and 3 female patients was 31 years (range 19 to 76 years). On follow-up, clinical signs and symptoms such as diplopia, ocular symmetry, enophthahnos and limitation of upward gaze
Fig. 5. A. CT scan on follow-up of patient No. I 0, 45 months after fracture of Le Fort type. Hypertrophic bone formation (arrow) is observable in the anterior part of the right orbital floor. B. CT scan on follow-up of the same patient. A small defect and prolapse of soft tissue (arrow) is observable in the posterior area of the right orbital floor. The plate should have been positioned more posteriorly.
Reconstruction of orbital floor with polydioxanone plate
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were recorded. Diplopia was investigated by a linear light using gaze direction test by questioning the patient about the separation of the two images in the cardinal positions of gaze 9. If enophthalmos was observed, the exact difference between the antero-posterior globe positions was measured in mm from the horizontal CT scans. The scar was examined and the satisfaction of the patients with the surgery assessed. Radiographic examinations were done immediately postoperatively and on follow-up. Plain film radiography was performed using Waters' projection and a Lysholm's skull stative (Sch6nander, Stockholm, Sweden). Panoramic films of the facial skeleton were obtained using Zonarc (Palomex, Instrumentarium, Finland). In the program for radiography o f the maxillofacial skeleton with one rotational axis, the distance from the rotational axis to the focused layer is 85 mm. The thickness of the cylindrical section is 28 mm, with a magnification factor of 1.18. Three sections at different depths were obtained, covering the entire depth of the orbit. Computerized tomography (CT) scanning was carried out in connection with follow-up examination in 13 patients. For CT, a Siemens Somatom CR was used. Axial tomograms were made using a 4 mm layer thickness at 4 mm shifts, except in the area o f the floor of the orbit, where the values were 2 mm in each case. For evaluation of the floor of the orbit, coronal reconstruction films were prepared at intervals of 10 pixels. In some cases, 3-dimensional reconstruction films were prepared, particularly of the area of the orbital floor, using projections looking from the top, the bottom and about 30 degrees above the horizontal (frontal) view. Films were analysed pre-operatively, postoperatively and on follow-up. All radiographs were evaluated by the same radiologist. PDS is an aliphatic polyester polymer which is decomposed through hydrolysis in 10-12 weeks. The PDS plate is bowl-shaped and stained with D + C violet 2(1-hydroxy-4p-toluidino-anthracinone). The dimensions o f a PDS bowl are 28 x 28 x 1 mm (Fig. 2). It is easy to cut to a suitable size from prefashioned material and to place over the defect. For surgery, a subciliary approach was used. The orbicularis oculi muscle was separated. Care was taken not to sever the orbital septum. The periorbital periost was incised and elevated from the orbital floor. The entire defect was exposed. After repositioning of the orbital contents and bony fragments, the PDS-plate was cut to fit the size of the defect and placed on the orbital floor in a subperiosteal fashion. It would be supported by the intact part of the orbital floor, completely covering the defect. The plate was fixed to the orbital rim with one or two 0.35 mm steel wires or sutures (Fig. 3). The mean period of hospitalization was 6.8 days (range 3 to 23 days).
Results N o c o m p l i c a t i o n s s u c h as e x t r u s i o n , haemorrhage, infection or displacement
86
l i z u k a et al.
Fig. 6. A. CT scan on follow-up of patient No. 12, 13 months after left blow-out fracture. There was on!y soft tissue bridging (arrow) on the reconstructed left orbital floor, with no new bone development. B. Three-dimensional CT reconstruction in the same patient. Defect seems also to exist in the uninjured right orbit. However, this is the result of three-dimensional CT with 2 mm layer thickness being unable to measure the density of extremely thin bone.
of the implant were seen postoperatively. Of the 20 patients, 9 had an inferiorly positioned (mean 3 mm) eyeglobe pre-operatively (Table 1). Diplopia was recorded in 8 of these patients. Postoperatively, diplopia was observed in 11 cases in all. Overcorrection of eyeglobe position was evident in 10 cases. Nine of these overcorrected patients exhibited transitory diplopia. The duration of the transitory diplopia related largely to the degree of overcorrection. It resolved in all but 2 cases after 4 to 65 days (mean 29 days). One patient had suffered severe brain injury and also had paresis of the abducens nerve. On follow up, his degree of enophthalmos was found to be 4 mm. The pre-operat -~ ive globe position could not be assessed in this patient because of unconsciousness and massive facial oedema. One
other patient had slight enophthalmos. Five had an inferiorly positioned (1-2 ram) eye-globe. Changes in globe positions in the horizontal plane at various stages are recorded in Table 1. Generally, there was a decline in globe position on the operated side with time. The radiographs were evaluated to determine the position of the lower orbital rim and orbital floor. On the plain films, the level of the lower orbital rim was readily observable but the posterior parts could not be evaluated. On the panoramic films, both the lower rim of the orbit and the posterior parts of the orbital floor were evaluable. Even defects in the bony structures were visible. On CT examination, the coronal reconstruction films clearly showed the extents of the bony structures and defects. The soft tissue status was also visible.
Table 2. Radiographic characteristics of patients on follow-up
Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Bone formation normal hypertrophic normal normal normal normal hypertrophic normal hypertrophic normal no (soft tissue) normal normal
Defect no no no no no no no not examined yes yes no no not examined no no
Symmetry of orbital plane symmetrical lower symmetrical symmetrical symmetrical symmetrical lower symmetrical symmetrical lower symmetrical symmetrical lower
Three-dimensional reconstruction films seemed to be of no value for detecting defects of the bony floor of the orbit, apparently because parts of the bony orbital floor are markedly thinner than the 2 mm CT slice used. CT, when used to produce 3-dimensional pictures, was unable to measure the density of extremly thin bone. Instead, such areas were calculated as soft tissue and showed up as bony defects on 3-dimensional pictures. From the radiographic analyses, 12 of the 13 patients examined exhibited bone formation on the reconstructed orbital floor. In 9 patients this bone was classified as normal (Fig. 4). In 3 patients it was classified as hypertrophic at the orbital base (Fig. 5A). In 2 patients there was a small defect in the reconstructed area bridged by soft tissue (Fig. 5B). In these cases, some soft tissue prolapse into the maxillary sinus was also observed. Both patients had normal pupil positions, however, and no diplopia. Only one patient had soft tissue bridging of the orbital floor, without new bone development (Fig. 6). Orbital asymmetry was present in 4 cases. In these patients the orbital base was always lower on the reconstructed than on the unoperated side. In all of these cases a lower globe position (range 1-2 ram) was observed (Table 2).
Discussion Several methods have been described for surgical reconstruction of orbital floor defects. Apart from autogenous bone 1 and cartilage2°, many materials
Reconstruction of orbital floor with polydioxanone plate have been used, including lyophilised dura 2~, D a c r o n mesh 3'4, silicone plate ~4, Teflon 11'16, lyophilised dermis 22, polyglactin 91012, poly (L-lactide) 2,7 and tricalcium phosphate calcium 5. Autogenous grafts are considered superior to foreign material implants because they are usually well accepted by the surrounding tissues. Additional surgery is, however, needed to obtain the graft. Lyophilised dura is not rigid enough to cover large defects. PDS plates were therefore chosen when the defect to be repaired was I - 2 cm in diameter, with otherwise intact or reconstructable surrounding bone structures. We found the PDS to be well tolerated by the body. It did not give rise to clinically detectable inflammatory reactions. A PDS plate is easily cut from prefashioned material, and is simple to place over the defect. The osteosynthesis material from the orbital rims o f 2 patients was removed about 1 year after the primary surgery and it was found that the PDS plate had been completely absorbed. The orbital base appeared as a dense flbrotic sheet, free from any defect. It would seem from our results that the material maintains its structural integrity long enough to form a sufficiently rigid scar, preventing delayed herniation o f the orbital content. The globe position on the operated side became lower during the process of absorption of the plate. It is, therefore, recommended to overcorrect, which resuits in transitory postoperative diplopia. In all cases in which asymmetry of the orbital plane was observed radiographically, the globe position on the operated side was also lower as observed clinically. This asymmetry was probably caused by incomplete repositioning of the surrounding zygomatic bone. In addition to repair of the orbital floor, good, stable reconstruction of the comminuted zygomaticomaxillary complex is, therefore, a conditio sine qua non, if asymmetry and enophthalmos are to be avoided. For stable reconstruction, we prefer miniplates to wires.
The use of an alloplastic biodegradable material obviates the need for a second operative procedure and thus eliminates the associated risk of morbidity. We are not aware of any study relating to injured patients in which similar repair has been described and long-term results analysed. It is concluded that the m e t h o d described is useful for the reconstruction of orbital floor defects in appropriately selected patients.
References 1. BAGATIN M. Reconstruction of orbital defect with autogenous bone from mandibular symphysis. J Craniomaxfac Surg 1987: 15: 103-5. 2. Bos RRM, BOERING G, ROZEMA FR, LEESLAGJW. Resorbable poly (L-lactide) plates and screws for the fixation of zygomatic fractures. J Oral Maxillofac Surg 1987: 45. 751-3. 3. BROWNINGCW. Dacron mesh-based implants for orbital floor reconstruction. Am J Ophthalmol 1969: 68: 914-19. 4. BURP,ES SA, COl-IN AM, MATHOG RH. Repair of orbital blow-out fractures with Marlex mesh and gelfitm. Laryngoscope 1981: 91: 1881-6. 5. CHUANGEL, BENSINGERRE. Resorbable implant for orbital defects. Am J Ophthalmol 1982: 94: 547-9. 6. CONVERSE JM, SMITH B, OBEAR MF, WOODSMITHD. Orbital blowout fractures: A 10-year survey. Plast Reconstr Surg 1957: 39: 20-36. 7. CUTRIGHTDE, HUNSUCKEE. The repair of fractures of the orbital floor using biodegradable polylactic acid. J Oral Surg 1972: 33: 28-34. 8. DE MAN K. Fractures of the orbital floor: Indications for exploration and for the use of a floor implant. J Maxillofac Surg 1984: 12: 73-7. 9. DUGUID IM. Ophthalmic injuries. In: ROWE NL, WILLIAMS JL, ed. Maxillofacial injuries. New York: Churchill Livingstone, 1985: 721. 10. DULLEY R, FELLS R Orbital blow-out fractures. Br Orthop J 1974: 31: 4754. 11. FREEMANBS. Direct approach to acute fractures of the zygomaticomaxillary
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complex and immediate prosthetic replacement of the orbital floor. Plast Reconstr Surg 1962: 29: 587-95. 12. HOELTJE W. Wiederherstellung von Orbitabodendefekten mit Polyglactin. In: Fortschr Kiefer Gesichtschir 28. New York: Thieme Verlag, 1983: 65-7. 13. KIRKEGAARDJ. Orbital floor fractures: early repair and results. Clin Otolaryngol 1986: 11: 69-73. 14. LIPSHUTZ H, ARDIZONE R. The use of silicone rubber in the immediate reconstruction of fractures of the floor of the orbit. J Trauma 1963: 3: 563-8. 15. MANDEL MA. Orbital floor "blow-out" fractures: Reconstruction using autogenous maxillary wall bone grafts. Am J Surg 1975: 130: 591-5. 16. POLLEYJW, RINGLERSL. The use of Teflon in orbital floor reconstruction following blunt facial trauma: a 20-year experience. Plast Reconstr Surg 1987: 79: 39-43. 17. PRENDERGASTML, WILDES TO. Evaluation of the orbital floor in zygoma fractures. Arch Otolaryngol Head Neck Surg 1988: 114: 446-50. 18. ROWE NL. Fractures of the zygomatic complex and orbit. In: ROWE NL, WILHAMS JL, eds. Maxillofacial injuries. New York: Churchill Livingstone, 1985: 500-25. 19. SMITHB, CONVERSEJM. Early treatment of orbital floor fractures. Trans Am Acad Ophthalmol Otolaryngol 1957: 61: 602-8. 20. STARK RB, FRILECK SR Conchal cartilage grafts in augmentation rhinoplasty and orbital floor fracture. Plast Reconstr Surg 1969: 43: 591-6. 21. WAITE PD, CLANTON JT. Orbital floor reconstruction with lyophilized dura. J Oral Maxillofac Surg 1988: 46: 72730. 22. WEBSTERK. Orbital floor repair with lyophilized porcine dermis. Oral Surg 1988: 65: 161-4,
Address: Tateyuki Iizuka M.D., D.D.S. Department of Oral & Maxillofacial Surgery Helsinki University Central Hospital Kasarmikatu 11-13 00130 Helsinki 13 Finland
To lizuka ~, P. Mikkonen ~, P. Paukku 2, C. Lindqvist 1 1Departments of Oral & Maxillofacial Surgery and 2Radiology, Helsinki University Central Hospital, Finland
T. Iizuka, P Mikkonen, P Paukku, C. Lindqvist: Reconstruction of orbital floor with polydioxanone plate. Int. J. Oral Maxillofae. Surg. 1991; 20: 83-87. Abstract. The use of a polydioxanone (PDS) plate for orbital reconstruction was evaluated in 20 patients with various traumatic defects of the orbital floor. The follow-up time was 9 to 45 months (mean 20.4 months). A CT scan was obtained in 13 patients. Radiographic analysis showed that in 12 of the 13 patients there was new bone in the orbital floor. Clinically, most patients had transitory postoperative diplopia (lasting for a mean of 29 days) because of overcorrection. Only 2 patients, however, suffered from persistent diplopia. In one patient, abducens nerve paresis was the cause. It is concluded that PDS is suitable for orbital floor reconstruction, at least in cases in which defects do not exceed 1-2 cm in diameter. Overcorrection seems necessary. The material is well tolerated, is totally absorbed and appears to be replaced by bone in nearly all cases.
Fractures of the orbital floor can present in various forms. It can be a direct extension of an orbital rim fracture, part of a fracture of the zygomatic complex, or a component of the Le Fort II or III variety of middle third fracture. It can also be isolated, in the absence of fracture of the orbital rim (blow-out fracture) 18. It varies from a simple fissural fracture to comminution and complete dehiscence of the floor. Indications for orbital floor repair are diplopia which fails to resolve, substantial herniation of orbital contents into the antrum, incarceration of tissue in the fracture, and enophthalmos exceeding 3 mm 1°. Kmsm,~R & ROWE18 have expressed the view that a defect > 1 cm in diameter, as measured by polytomography, is an indication for surgical repair. A defect measuring < 1 cm in diameter but > 5
mm necessitates surgery only if there are positive clinical signs of prolapse, as shown by a positive forced duction test. According to PRENDERGAST & WILDES 17, however, the presence or absence of clinical orbital findings, apart from enophthalmus or diplopia is an unreliable indicator of the degree of orbital floor injury. Persistent diptopia from zygomatic fractures correlates significantly with a floor defect > 10 mm in diameter and with the existence of comminution or herniation, or with the simultaneous occurrence of both 13 (Fig. 1). Concern regarding late development of diplopia and enophthalmos is unjustified if there is no marked impairment of vertical eye movements within 14 days of the accident s. It is obvious that in a large number of cases of orbital floor fractures explo-
Key words: orbital fractures; orbital defects; bio-absorbable plates; polydioxanone plate Accepted for publication 26 September 1990
Fig. 2. Bowl-shaped PDS plate, dimensions 28 x28x 1 mm. ration of the orbital floor is essential but that reconstruction poses a number of problems. The defect must be repaired so that orbital herniation and entrapment of extraocular muscles are prevented. At the same time, unaesthe-
Fig. 1. Example of typical untreated "blowout" fracture. A woman of 40 sustained a facial injury in a traffic accident 6 months earlier. The fracture was not initially diagnosed and operated on. The patient has zygomatic asymmetry and severe enophthalmos (A). CT scan shows a Now-out fracture in the coronal plane and prolapse of the orbital content into the maxillary sinus (13).Asymmetry of the eye globes is clearly evident in the horizontal plane (C).
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Iizuka et al.
Fig. 3. Intraoperative view: defect of the orbital floor (A). The defect is covered with a PDS plate, which is fixed with a suture of PDS to the orbital rim (B).
absorbable polyester which has been used for several years as a suturing material. It has recently also been marketed as a plate for orbital floor reconstruction (PDS-Schale fiir Orbitaboden, Ethicon, Hamburg-Norderstedt, Germany). The use of PDS has not previously been evaluated in any follow-up study concerning patients with fractures of the orbital floor. F r o m the beginning of 1986 to the end of 1988 we used this material instead of a bone graft in 20 cases when the use o f lyophilised dura was considered inadequate for bridging an orbital floor defect. The aim of this study was to evaluate the material clinically and radiographically, with special emphasis on its reported complete absorption within 10-12 weeks 12.
Material and methods
Fig. 4. CT scan on follow-up of patient No. 3, 19 months after fracture of Le Fort type. Normal bone formation in the reconstructed right orbital floor (arrow) and symmetry of the orbital plane.
tic enophthalmos must be avoided. Previously, orbital floor fractures were stabilized by packing the maxillary sinus with gauze or a balloon. Those techniques have, however, proved inadequate in some cases. Open reduction and reconstruction have gained in popularity. Although autogenous bone has been the material of choice, unpredictable resorption and donor-site problems have been encountered 6,19. A number of alloplastic materials have, there-
fore, been used as replacements for bone. Criteria for ideal reconstruction material include 1) biocompatibility, making removal unnecessary, 2) lack of carcinogenity, 3) strength and rigidity, 4) capacity for being sculpted during the operation, 5) ease of anchoring in position, 6) capacity for sterilization and 7) capacity for use for single stage reconstruction of extensive defects1,12,13,lS. Polydioxanone (PDS) is a completely
A PDS plate was used for orbital floor reconstruction in 20 patients in the Department of Oral and Maxillofacial Surgery, Helsinki University Central Hospital, Finland, between 1986 and 1988. The indication for surgical intervention was the presence of an orbital floor defect greater than 10 mm in diameter with perforation to the maxillary sinus and an otherwise reconstructable or intact orbital rim. Larger defects with extensive comminution were reconstructed using bone grafts from the iliac crest. Seventeen of the 20 patients were available for clinical examination and 13 patients for a radiological examination on average 20 months (range 9 to 45 months) after operation. In 8 cases fractures of the Le Fort type and in 10 cases zygomatic fractures were associated with the comminuted orbital floor fracture. Two patients had an isolated fracture of the orbital floor only (blow-out fracture). The mean age of 17 male and 3 female patients was 31 years (range 19 to 76 years). On follow-up, clinical signs and symptoms such as diplopia, ocular symmetry, enophthahnos and limitation of upward gaze
Fig. 5. A. CT scan on follow-up of patient No. I 0, 45 months after fracture of Le Fort type. Hypertrophic bone formation (arrow) is observable in the anterior part of the right orbital floor. B. CT scan on follow-up of the same patient. A small defect and prolapse of soft tissue (arrow) is observable in the posterior area of the right orbital floor. The plate should have been positioned more posteriorly.
Reconstruction of orbital floor with polydioxanone plate
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were recorded. Diplopia was investigated by a linear light using gaze direction test by questioning the patient about the separation of the two images in the cardinal positions of gaze 9. If enophthalmos was observed, the exact difference between the antero-posterior globe positions was measured in mm from the horizontal CT scans. The scar was examined and the satisfaction of the patients with the surgery assessed. Radiographic examinations were done immediately postoperatively and on follow-up. Plain film radiography was performed using Waters' projection and a Lysholm's skull stative (Sch6nander, Stockholm, Sweden). Panoramic films of the facial skeleton were obtained using Zonarc (Palomex, Instrumentarium, Finland). In the program for radiography o f the maxillofacial skeleton with one rotational axis, the distance from the rotational axis to the focused layer is 85 mm. The thickness of the cylindrical section is 28 mm, with a magnification factor of 1.18. Three sections at different depths were obtained, covering the entire depth of the orbit. Computerized tomography (CT) scanning was carried out in connection with follow-up examination in 13 patients. For CT, a Siemens Somatom CR was used. Axial tomograms were made using a 4 mm layer thickness at 4 mm shifts, except in the area o f the floor of the orbit, where the values were 2 mm in each case. For evaluation of the floor of the orbit, coronal reconstruction films were prepared at intervals of 10 pixels. In some cases, 3-dimensional reconstruction films were prepared, particularly of the area of the orbital floor, using projections looking from the top, the bottom and about 30 degrees above the horizontal (frontal) view. Films were analysed pre-operatively, postoperatively and on follow-up. All radiographs were evaluated by the same radiologist. PDS is an aliphatic polyester polymer which is decomposed through hydrolysis in 10-12 weeks. The PDS plate is bowl-shaped and stained with D + C violet 2(1-hydroxy-4p-toluidino-anthracinone). The dimensions o f a PDS bowl are 28 x 28 x 1 mm (Fig. 2). It is easy to cut to a suitable size from prefashioned material and to place over the defect. For surgery, a subciliary approach was used. The orbicularis oculi muscle was separated. Care was taken not to sever the orbital septum. The periorbital periost was incised and elevated from the orbital floor. The entire defect was exposed. After repositioning of the orbital contents and bony fragments, the PDS-plate was cut to fit the size of the defect and placed on the orbital floor in a subperiosteal fashion. It would be supported by the intact part of the orbital floor, completely covering the defect. The plate was fixed to the orbital rim with one or two 0.35 mm steel wires or sutures (Fig. 3). The mean period of hospitalization was 6.8 days (range 3 to 23 days).
Results N o c o m p l i c a t i o n s s u c h as e x t r u s i o n , haemorrhage, infection or displacement
86
l i z u k a et al.
Fig. 6. A. CT scan on follow-up of patient No. 12, 13 months after left blow-out fracture. There was on!y soft tissue bridging (arrow) on the reconstructed left orbital floor, with no new bone development. B. Three-dimensional CT reconstruction in the same patient. Defect seems also to exist in the uninjured right orbit. However, this is the result of three-dimensional CT with 2 mm layer thickness being unable to measure the density of extremely thin bone.
of the implant were seen postoperatively. Of the 20 patients, 9 had an inferiorly positioned (mean 3 mm) eyeglobe pre-operatively (Table 1). Diplopia was recorded in 8 of these patients. Postoperatively, diplopia was observed in 11 cases in all. Overcorrection of eyeglobe position was evident in 10 cases. Nine of these overcorrected patients exhibited transitory diplopia. The duration of the transitory diplopia related largely to the degree of overcorrection. It resolved in all but 2 cases after 4 to 65 days (mean 29 days). One patient had suffered severe brain injury and also had paresis of the abducens nerve. On follow up, his degree of enophthalmos was found to be 4 mm. The pre-operat -~ ive globe position could not be assessed in this patient because of unconsciousness and massive facial oedema. One
other patient had slight enophthalmos. Five had an inferiorly positioned (1-2 ram) eye-globe. Changes in globe positions in the horizontal plane at various stages are recorded in Table 1. Generally, there was a decline in globe position on the operated side with time. The radiographs were evaluated to determine the position of the lower orbital rim and orbital floor. On the plain films, the level of the lower orbital rim was readily observable but the posterior parts could not be evaluated. On the panoramic films, both the lower rim of the orbit and the posterior parts of the orbital floor were evaluable. Even defects in the bony structures were visible. On CT examination, the coronal reconstruction films clearly showed the extents of the bony structures and defects. The soft tissue status was also visible.
Table 2. Radiographic characteristics of patients on follow-up
Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Bone formation normal hypertrophic normal normal normal normal hypertrophic normal hypertrophic normal no (soft tissue) normal normal
Defect no no no no no no no not examined yes yes no no not examined no no
Symmetry of orbital plane symmetrical lower symmetrical symmetrical symmetrical symmetrical lower symmetrical symmetrical lower symmetrical symmetrical lower
Three-dimensional reconstruction films seemed to be of no value for detecting defects of the bony floor of the orbit, apparently because parts of the bony orbital floor are markedly thinner than the 2 mm CT slice used. CT, when used to produce 3-dimensional pictures, was unable to measure the density of extremly thin bone. Instead, such areas were calculated as soft tissue and showed up as bony defects on 3-dimensional pictures. From the radiographic analyses, 12 of the 13 patients examined exhibited bone formation on the reconstructed orbital floor. In 9 patients this bone was classified as normal (Fig. 4). In 3 patients it was classified as hypertrophic at the orbital base (Fig. 5A). In 2 patients there was a small defect in the reconstructed area bridged by soft tissue (Fig. 5B). In these cases, some soft tissue prolapse into the maxillary sinus was also observed. Both patients had normal pupil positions, however, and no diplopia. Only one patient had soft tissue bridging of the orbital floor, without new bone development (Fig. 6). Orbital asymmetry was present in 4 cases. In these patients the orbital base was always lower on the reconstructed than on the unoperated side. In all of these cases a lower globe position (range 1-2 ram) was observed (Table 2).
Discussion Several methods have been described for surgical reconstruction of orbital floor defects. Apart from autogenous bone 1 and cartilage2°, many materials
Reconstruction of orbital floor with polydioxanone plate have been used, including lyophilised dura 2~, D a c r o n mesh 3'4, silicone plate ~4, Teflon 11'16, lyophilised dermis 22, polyglactin 91012, poly (L-lactide) 2,7 and tricalcium phosphate calcium 5. Autogenous grafts are considered superior to foreign material implants because they are usually well accepted by the surrounding tissues. Additional surgery is, however, needed to obtain the graft. Lyophilised dura is not rigid enough to cover large defects. PDS plates were therefore chosen when the defect to be repaired was I - 2 cm in diameter, with otherwise intact or reconstructable surrounding bone structures. We found the PDS to be well tolerated by the body. It did not give rise to clinically detectable inflammatory reactions. A PDS plate is easily cut from prefashioned material, and is simple to place over the defect. The osteosynthesis material from the orbital rims o f 2 patients was removed about 1 year after the primary surgery and it was found that the PDS plate had been completely absorbed. The orbital base appeared as a dense flbrotic sheet, free from any defect. It would seem from our results that the material maintains its structural integrity long enough to form a sufficiently rigid scar, preventing delayed herniation o f the orbital content. The globe position on the operated side became lower during the process of absorption of the plate. It is, therefore, recommended to overcorrect, which resuits in transitory postoperative diplopia. In all cases in which asymmetry of the orbital plane was observed radiographically, the globe position on the operated side was also lower as observed clinically. This asymmetry was probably caused by incomplete repositioning of the surrounding zygomatic bone. In addition to repair of the orbital floor, good, stable reconstruction of the comminuted zygomaticomaxillary complex is, therefore, a conditio sine qua non, if asymmetry and enophthalmos are to be avoided. For stable reconstruction, we prefer miniplates to wires.
The use of an alloplastic biodegradable material obviates the need for a second operative procedure and thus eliminates the associated risk of morbidity. We are not aware of any study relating to injured patients in which similar repair has been described and long-term results analysed. It is concluded that the m e t h o d described is useful for the reconstruction of orbital floor defects in appropriately selected patients.
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Address: Tateyuki Iizuka M.D., D.D.S. Department of Oral & Maxillofacial Surgery Helsinki University Central Hospital Kasarmikatu 11-13 00130 Helsinki 13 Finland
