What are the guidelines for sizing and indications of orbital floor reconstruction implants in cases of enophthalmos (displacement of the eye globe into the orbit) and orbital floor fractures?

Data-Driven Pearls for Orbital Floor Reconstruction

Orbital floor reconstruction should be performed for enophthalmos of 2 mm or greater, large floor fractures causing facial asymmetry, or when there is muscle/tissue entrapment causing oculocardiac reflex. 1

Indications for Orbital Floor Reconstruction

Immediate Repair (within 24-48 hours)

• Entrapped muscle or periorbital tissue with nonresolving oculocardiac reflex (symptoms include bradycardia, heart block, dizziness, nausea, vomiting, or loss of consciousness) 1, 2
• White-eyed blow-out fracture with muscle entrapment and oculocardiac reflex (primarily seen in children) 1, 2
• Globe subluxation into the maxillary sinus 1

Early Repair (within 1-2 weeks)

• Symptomatic diplopia with positive forced ductions or entrapment on CT with minimal improvement 1
• Large floor fractures (>2.5 cm²) causing orbital volume expansion 1, 3
• Hypoglobus (downward displacement of the globe) causing facial asymmetry 1
• Progressive infraorbital hypoesthesia 1
• Early enophthalmos (>2 mm) causing facial asymmetry 1, 4

Delayed Repair (after 2 weeks)

• Restrictive strabismus that doesn't resolve 1
• Unresolved enophthalmos (>2 mm) 1, 5

Observation (no surgery needed)

• Minimal diplopia (not in primary or downgaze) 1
• Good ocular motility without significant enophthalmos or hypoglobus 1
• Small defects without massive orbital fat herniation 3

Implant Sizing Considerations

• For small to moderate defects (up to 2.5 cm²), resorbable materials like polydioxanone sheet can be used 3
• For larger defects (>2.5 cm²), non-resorbable materials are preferred to prevent post-resorption enophthalmos 3, 4
• Implant should be sized to:
  • Extend beyond the fracture margins to rest on stable bone 4, 5
  • Be thick enough to compensate for the increased orbital volume 4
  • Follow the natural slope of the orbital floor 5

Enophthalmos Assessment

• Enophthalmos of 2 mm or greater is considered clinically significant and warrants surgical correction 4, 5
• Exophthalmometry should be performed to quantify the degree of enophthalmos 1, 5
• Slight overcorrection (1-2 mm of exophthalmos) at the end of surgery is recommended to account for postoperative regression 5
• Average improvement after surgical correction is approximately 1.4 mm for enophthalmos and 0.6 mm for hypophthalmos 6

Surgical Pearls

• Preoperative CT imaging is essential to assess fracture size and location 1
• Dissection to the posterior margin of the fracture is critical to prevent residual enophthalmos 5
• Proper reconstruction of the orbital floor slope is crucial for optimal outcomes 5
• Endoscopic approaches can minimize complications and improve visualization, especially for posterior fractures 7, 5
• Forced duction testing before, during, and after repair helps confirm adequate release of entrapped tissues 1

Potential Complications and Pitfalls

• Even with proper repair, diplopia can persist (37% of patients postoperatively) 1
• Fat entrapment can be as challenging as muscle entrapment, resulting in fibrotic adhesions 1
• Adhesions to porous implants can occur and cause motility restrictions 1
• Resorbable implants may not provide adequate long-term support for large defects 3
• Waiting 4-6 months after trauma is advised for non-urgent cases to ensure stability of misalignment 1

Follow-up Recommendations

• Minimum follow-up of 3-6 months is recommended to assess long-term outcomes 6, 5
• Monitor for residual enophthalmos, which may develop over time, especially with resorbable implants 3, 7
• Assess for diplopia in primary position and downgaze, which are the most functionally important fields of vision 1