In lower eyelid fat transposition, is subperiosteal placement of the fat permissible, what is the safe inferior dissection limit, and how can injury to the infraorbital nerve be prevented?

Lower Eyelid Fat Transposition: Subperiosteal Placement and Surgical Technique

Subperiosteal Fat Placement is Permissible but Not Preferred

Yes, fat can be placed in the subperiosteal plane, but supraperiosteal and supramuscular planes are safer alternatives with lower complication rates and easier surgical dissection. 1, 2

Available Dissection Planes

Multiple anatomical planes exist for fat transposition in lower eyelid blepharoplasty:

• Subperiosteal plane: Historically described but associated with a steep learning curve due to anatomic complexity 1, 2
• Supraperiosteal plane: Utilizes natural midcheek spaces (premaxillary and prezygomatic spaces) with clearer anatomical landmarks 1
• Submuscular plane: Fat positioned beneath the orbicularis oculi muscle 2
• Supramuscular plane: Fat pedicle transposition above the orbicularis muscle, demonstrating long-term efficacy with minimal complications 2

The supramuscular and supraperiosteal approaches have largely superseded subperiosteal techniques because they avoid the anatomic complexity and steep learning curve while maintaining excellent aesthetic outcomes 1, 2.

Safe Inferior Dissection Limits

Dissection should extend just below the lower orbital rim to the level of the palpebromalar and nasojugal sulci, traversing the malar septum after freeing the arcus marginalis. 3

Specific Anatomical Boundaries

• Superior limit: Incision made 3 mm above the fornix through conjunctiva, inferior tarsal muscle, and capsulopalpebral fascia 3
• Inferior limit: Dissection passes below the palpebromalar and nasojugal sulci after traversing the malar septum 3
• Depth: Preseptal-suborbicularis dissection plane, freeing the arcus marginalis at the orbital rim 3

The dissection should remain controlled and not extend excessively into deeper orbital tissues, as adhesions and entrapment may extend well into the deeper orbit beyond surgical reach 4.

Infraorbital Nerve Protection Strategies

The infraorbital nerve exits approximately 1 cm below the infraorbital rim in the mid-pupillary line; avoid aggressive dissection in this region and maintain dissection superficial to the periosteum when working near the nerve exit point.

Critical Prevention Measures

• Anatomical awareness: The infraorbital nerve emerges from the infraorbital foramen approximately 1 cm below the orbital rim, typically in line with the mid-pupillary axis
• Plane selection: Using the premaxillary and prezygomatic spaces (natural midcheek spaces) provides clear anatomical landmarks that avoid the nerve 1
• Gentle technique: Blunt dissection of fat bags rather than sharp dissection minimizes nerve trauma 3
• Visualization: Use of specialized transconjunctival retractors and lower-lid retractors improves surgical field exposure 3

Documented Complication Rates

In a series of 184 consecutive patients undergoing transconjunctival fat transposition using midcheek spaces, no cases of binocular diplopia, eye misalignment, or significant numbness involving the lower eyelid, cheek, and upper lip were reported over 22 months average follow-up 1. This demonstrates that proper technique with appropriate plane selection effectively avoids infraorbital nerve injury.

Critical Pitfalls to Avoid

Orbital fat entrapment can lead to restrictive strabismus, a serious complication requiring meticulous fat handling techniques. 5

Major Complications

• Restrictive strabismus: Inadvertent entrapment or adhesion of orbital fat can cause fibrotic and adhesion syndromes not readily relieved with dissection 4, 5
• Fat entrapment: Can prove nearly as challenging as extraocular muscle entrapment, with adhesions extending deep into the orbit beyond surgical reach 4
• Nerve injury: Numbness of the lower eyelid, cheek, and upper lip can occur with improper dissection technique 1

Technical Safeguards

• Fat fixation: Secure the fat flap with transcutaneous stitches tied over small pieces of silicone to prevent migration 3
• Transcutaneous-transconjunctival suture: Promotes scarring of the transected planes and reduces postoperative complications 3
• Avoid excessive tension: Fat should rest naturally without tension to prevent restrictive complications 1
• Surgeon experience: These procedures should only be performed by surgeons experienced in transconjunctival techniques 3

The mean operating time for experienced surgeons using the midcheek space technique is approximately 47 minutes, with patient satisfaction scores of 98.91% and no major complications 1.