Orbital Floor Blowout Fracture Reconstruction Using Moldable Polymethyl Methacrylate: A Report of Two Cases and Their Imaging Findings

Figures & data

Figure 1 Preoperative coronal (A) and sagittal (B) computed tomography of the head with the bone algorithm showing a comminuted blowout fracture involving the right orbital floor that approximately measures 0.86 cm × 1.5 cm × 1 cm in maximum orthogonal dimensions, which was associated with fat herniation, inferior rectus muscle entrapment, soft tissue swelling, and intra-orbital gas locules The optic nerve appears unaffected.

Table 1 Proposed Criteria for Surgical Treatment of Orbital Floor Fractures

Significant internal orbital defects confirmed via imaging

Disturbances of eye mobility as a result of the existing incarceration of ocular muscles

Enophthalmos

Exophthalmos secondary to blow-in fractures

Hypophthalmos

Figure 2 Steps for intraoperative custom preparation of polymethyl methacrylate implants. (A) Mixing the PMMA acrylic resin powder with the liquid component (from the set) in a sterile ampoule in a well-ventilated atmosphere. (B) Open the peelable pouch and start emptying the whole contents. (C) Enclose into the sterile foil pouch, ie, plastic sleeves. (D) transfer the plastic sleeves to the sterile surgical area, and when the dough-like material does not adhere to the surgical gloves of the surgeon, the PMMA resin is ready for manipulation. Apply the resin to the osseous defect and remove any excess resin.

Figure 3 Postoperative follow-up magnetic resonance imaging of the globes. Multi-sequential coronal planar images of the orbit, including plain T1 weighted imaging (A, B); T1-weighted imaging with contrast and fat saturation (C); and T2-weighted imaging (D). These images demonstrate the status after right orbital floor oculoplasty and inferior orbital wall PMMA implant placement (*) with interval complete sealing of the prior fracture. The placed implant measures 1.69 cm × 1.9 cm (A and B) and can be seen covering nearly the entire inferior orbital wall [2.8 cm] (A). The implant is seen subjacent to the inferior rectus muscle with satisfactory attachment to the right inferior orbital wall and adequate fat spacing from extraocular muscles. No significant asymmetry is observed in orbital muscles bilaterally, nor are there signs of an inflammatory process.

Figure 4 Postoperative photographs in the primary gaze (A) and supraduction (B) positions showing significant correction of the inferior sulcus after the BOF and resolving enophthalmos. The patient was followed up for one year and showed no complications.

Figure 5 Preoperative sagittal (A) and coronal (B) computed tomography of the head with the bone algorithm show a displaced fracture of the left lamina papyracea, medial orbit, and displaced BOF of the left inferior orbital wall, which approximately measures 1.4 cm × 2 cm × 1 cm in its maximum orthogonal dimensions. The BOF is associated with a small, displaced bone fragment, abnormal superior orientation of the globe, orbital fat herniation, tethered inferior rectus muscle (*), and proptosis of the eye.

Abbreviation: BOF, blowout fracture.

Table 2 A Summary of Commonly Used Synthetic Materials in Oculoplastic Reconstruction^2,3

Type of Implant	Advantages	Disadvantages
Bone (rib, ilium, mandible, maxilla, and calvarium)	- Rigidity, molding capacity, vascularity, and biocompatibility - Minimal inflammatory reaction - Less infection, extrusion, capsule formation, and ocular tethering	- Donor site-related complications - Increased operative time - Difficulty in contouring the desired morphology and size - Cannot be used alone in large defects with multiple fractures - Unpredictable and variable degree of graft resorption
Cartilage (auricular, concha, and nasal septum)	- Ease of access, malleability - Excellent support without evidence of resorption, long-lasting up to 3 years - Can survive with minimal oxygen requirement, improve graft viability reduce resorption rate (ie, relative avascularity) - Less infection, extrusion, and chronic inflammatory reaction - Minimal site-related morbidity	- For small defects only (up to 2 cm × 2 cm) due to donor tissue availability - Increased operative time
Allogenic (lyophilized dura mater, demineralized human bone, fascia lata, banked bone)	- Lack of donor site complications - Decreased operative time - Biocompatible	- Higher resorption rate than that of autografts - Disease transmission from the donor (eg HIV, HCV, prion disease) - Higher rate of enophthalmos compared to autologous grafts
Polymers (polylactic acid, polyglycolic acid)	- Biodegradable and predictable absorption kinetics - Easy shaping to desired morphology and size - Spares operative time and allows for primary reconstruction since it is resorbable - No donor site complications - Adequate biomechanical resistance - Prevent post-operative proptosis due to low profile construction - Not requirement for rigid fixation - Radiolucency	- Inflammatory reaction to foreign implant causing ocular muscle adhesion and diplopia - Increased rate of late enophthalmos after degradation - Not suitable for large defects
Porous polyethylene	- Variable size and thickness - Allows vascularization and ingrowth of soft tissue and bone - Rigid fixation is not required - Easy molding and adaptability - Long-term stability and tensile strength - No significant change in orbital volume - Adequate structural support - More suitable for a large defect	- High infection rate
Titanium	- Used for large orbital defects >2 cm and correction of orbital shape - Prevents development of traumatic enophthalmos - Availability, biocompatibility, ease of intraoperative contouring	- Difficult positioning - Require rigid fixation - Requires open reduction and internal fixation for unstable, displaced, or comminuted fracture - Fibrogenic, adherent syndrome - Persistence of diplopia and enophthalmos - Difficulty in removal due to scar perforating the pores - Toxicity due to metal ion release
Bioactive glasses	- Osteoconductive (new bone formation) - Rigid fixation is not required - No implant-related infection, migration, or extrusion reported - Foreign body reaction can occur	- Difficulty in shaping and molding.
Others: silicone,	- Low cost, flexibility, ease of handling - Adequate structural support - Used in large orbital fracture	- A higher fibrous capsule formation rate is a significant risk for fistula, sinus tract, cyst, and infection

Abbreviations: y, year; HIV, human immunodeficiency virus; HCV, hepatitis C virus.

Figure 6 Postoperative follow-up images of the globes, as multi-sequential MR coronal planar images of the orbit including T1 weighted images without (A and B) and T1 weighted images with contrast and fat saturation (C), and T2 weighted images (D) Coronal CT with the bone algorithm (E) showing the status after left orbital floor cranioplasty and inferior orbital wall implant placement for a previous inferior orbital wall displaced fracture, none of which were visualized on follow-up images. The implant measured 2.2 cm × 1.4 cm and covered nearly the entire inferior orbital wall (2.8 cm). The implant is seen subjacent to the inferior rectus muscle with satisfactory attachment to the left inferior orbital wall and adequate fat spacing from extraocular muscles. No significant asymmetry was observed in the orbital muscles bilaterally, nor are there signs of an inflammatory process or implant sliding.

Abbreviations: CT, computed tomography; MR, magnetic resonance.

Figure 7 Postoperative photographs in the primary gaze (A) and supraduction (B) positions showing significant correction of the inferior sulcus after the BOF and resolving enophthalmos The patient was followed up for one year and showed no complications.