Bridge of Bone Canthopexy by: Michael J. Yaremchuk, M.D.

Introduction

The youthful palpebral fissure is long and narrow with a slight lateral upward inclination.

Distortions of, or deviations from, this shape may be secondary to heredity, aging, paralysis, trauma or previous surgery^. This distortion of shape inevitably manifests as rounding of the fissure with inferomedial descent of the lateral canthus and concomitant descent of the lower lid margin. Lateral canthopexy, the surgical repositioning of the lateral canthus is fundamental to altering or restoring the shape of the palpebral fissure.

Anatomically, the lateral canthus is more correctly termed a lateral retinaculum. The retinaculum receives contributions from the lateral horn of the levator aponeurosis, the lateral extension of the preseptal and pretarsal orbicularis oculi muscle (lateral canthal tendon), the inferior suspensory ligament of the globe (Lockwood’s ligament), and the check ligament of the lateral rectus muscle . It splits into anterior and posterior leaflets. The anterior leaf is contiguous with the orbital periosteum. The posterior leaflet inserts on the lateral orbital tubercle (Whitnall’s). Change on the point of attachment or length of the retinaculum will cause significant changes on eyelid shape, tension and coutour (Ref 2,3).

Lower eyelid tarsus suspension was originally described by Lexer and Eden (Ref3) in 1911, followed by Sheehan (Ref 5). Since then, many different techniques have been designed to restore lateral canthal position and to correct lower eyelid malposition. Two requisites of lateral canthopexy make it technically challenging – symmetry and stability. Suturing of lateral canthal structures to similar points on the inner aspects both lateral orbital rims can be difficult. Stable suture fixation can also be challenging, particularly when previous eyelid surgery has scarred and distorted periorbital tissues.  First Hinderer (Ref 6)^  and then Whitaker (Ref 7) Ortiz-Monasterio and Rodriguez (Ref 8), and then Flowers (Ref 9) reported techniques utilizing drill holes made in the lateral orbital rim which  provided points of fixation which were both anatomically defined and secure.

In this article we describe our technique of lateral canthopexy, an adaptation of the one described by Whitaker (Ref 8). The lateral canthal structures are purchased with a figure of eight suture of titanium wire. Drill holes are placed in the lateral orbital rim using the zygomaticofrontal sutures as reference landmarks. This measured placement aids in achieving symmetric canthal repositioning.  The bridge of bone between the drill holes provides a stable platform over which the wire ends can be tied. Fine adjustments can be made to the canthal position by twisting or untwisting the wire ends.

Overview

Bridge of bone canthopexy requires exposure of the lateral orbit and mobilization of the lateral canthus soft tissue mechanism. Its efficacy is based on the stable suture fixation point provided by drill holes placed in the bone of the lateral orbit.

Anesthesia

This procedure can be performed under local or general anesthesia.

Incisions (Figure 2a)

Bridge of bone lateral canthopexy requires access to the lateral orbital rim from the level of Whitnall’s tubercle to the zygomaticofrontal suture. This can be accomplished through the lateral extent of an upper blepharoplasty incision. Most often, I prefer the lateral extent of both upper and lower blepharoplasty incisions. The lower blepharoplasty incision provides superior visualization of the lateral canthal tissues.  This anatomy can also be approached from the access provided by a  bicoronal incision if concomitant browlift is performed.

Figure of Eight Suture (Figure 2b)

When only 1 or 2 millimeter of superior or lateral movements of the lateral canthus and adjacent lid margin are desired, one or both limbs of the lateral canthus may be purchased with a figure of eight suture without freeing of the lateral retinacular                            structures from the lateral orbit. The amount of commissure movement will be limited by the length of the ligament, the point of suture purchase relative to the lateral commissure, and the position of the lateral orbit drill holes. This approach is most often appropriate when there is minimal commissure malposition and no local scarring from previous lid surgery.

When more significant movements of the  lateral commissure and lid margin are desired, complete subperiosteal freeing of the lateral retinacular structures is required before figure of eight suture purchase of both limbs of the ligament. Through the lateral extent of the lower blepharoplasty incision, the lateral retinaculum is identified and dissected, and both limbs of the lateral canthus are purchased with a figure-of-eight 30- or 32-gauge titanium wire suture. If middle lamellar scarring from previous lower lid surgery restricts canthal movement, the lateral third of the middle lamellae is sufficiently incised with needle tip electrocautery to allow it to be freely mobile.

Drill Holes (Figures 2c and 2d)

Through the upper access approach, the zygomatico-frontal suture is identified. This suture provides a landmark to allow symmetric placement of drill holes made in the lateral orbital rim. Using the zygomatico-frontal suture as a landmark two drill holes are placed in the lateral orbital rim. The position of the lower drill hole is key, since it determines the maximum upward movement of the canthus. The upper drill hole is necessary to create the “bridge of bone” – a stable fixation point.

The lateral canthal position and aperture shape are determined by the position of the drill holes, which should be 2-3 mm above the medial canthal plane to give the intercanthal axis a slight upward tilt. The drill holes should also be placed in the internal orbit about 3-4 mm posterior to the anterior margin of the lateral orbital rim so the lateral lid will not be drawn away from contact with the globe (Figure 3).

To determine the ideal position of the drill holes, one can grasp the lateral canthus and tuck it against the lateral orbital rim until the desired canthal and lower-lid position is obtained. The positions are marked and drill holes are made at that point. Most often, they are positioned just at, and 2mm below, the zygomaticofrontal suture. Each end of the wire is then passed from within the orbit through the drill holes to the lateral orbital rim. The wires are then twisted to one another over the bridge of bone between the two holes. Wire twisting will determine canthal movement. The location of the lower drill hole dictates the limit of movement.

The strand of twisted wire ends is left approximately 5 millimeters long. This length of twisted wire ends has two advantages. It allows intraoperative (or postoperative) adjustment of the canthal position by simply twisting or untwisting the wires. It is not necessary to repeat the suturing process. In addition, this length allows the ends to be placed into one of the drill holes or into the orbit. This maneuver avoids postoperative visibility or palpability of the wire ends.

If local incisions are used for access, an ellipse of skin and muscle is removed from the lateral aspect of the upper lid to remove the lid redundancy caused by the upward movement of the canthus. The wounds are closed in layers.

When extensive dissection is performed, post-operative chemosis is common. In addition to ophthalmic lubricants, I have found that a temporary tarsorraphy stitch left for 5 to 7 days significantly attenuates this process. The tarsorrhaphy is performed by placing a single 5-0 nylon suture through the upper and lower lid margins and adsjacent skin. Tying the suture approximates the lids.

Clinical Examples

Clinical examples of the use of the “bridge of bone canthopexy’ are demonstrated in figures 4-7.

Conclusion

 The terminology of lateral canthal surgery is confusing. A lateral canthopexy repositions the lateral canthus. It moves the displaced or attenuated lateral canthal mechanism to a desired position with or without its disinsertion. Since it does not violate the lateral commissure or lower lid margin, it maintains or has the potential to restore palpebral fissure shape, including the lateral canthal angle. Canthoplasty procedures such as the lateral tarsal strip, by design, alter the shape of the palpebral fissure, because they disrupt the lateral commissure while shortening the lower lid margin (Ref 10).  Lateral canthal/horizontal eyelid shortening procedures were first developed  to treat functional eyelid disorders. By decreasing the surface area of exposed cornea they ameliorated symptoms of ‘dry eyes’ . They were later adapted to aesthetic surgery as prophylaxis against or to correct post blepharoplasty lid malposition. These lid margin shortening procedures are appropriate treatment for senile ectropion and entropion – situations where the lid margin is redundant.  Their aesthetic implications should not be discounted. Canthoplasty procedures may be effective in elevating the lower lid, but often exaggerate the senile or post surgical distortion of palpebral fissure shape.  Figure 8.

Canthopexy procedures which simply reef or attach the lateral canthal tendon to the lateral orbit periosteum provide sufficient stability and accuracy as prophylaxis against and to correct mild postblepharoplasty lid malposition.

Bridge of bone canthopexy’ has found greatest utility when significant movements of canthal position are required.  A canthal fixation point (the inferior drill hole) created a measured distance from a fixed anatomic point (the zygomaticofrontal suture)  assures accurate and symmetric placement.  Wire suture fixation over the bridge of bone created by the two drill holes provides maximum stability to counter soft tissue deforming forces.  The senior author uses this technique alone to reposition the lateral canthus and lower lid when periorbital tissues are adequate. When post blepharoplasty tissues are inadequate,  a subperiosteal midface lift is added to recruit cheek and lid tissues (Ref 11). To provide support for lid and midface soft tissues, sagittal augmentation of the infraorbital rim is added to the lid and canthus repositioning algorithm in post blepharoplasty patients with midface skeletal deficiency (‘morphologically prone’ (Ref 12).

REFERENCES

1- Farkas LG, Hreczko TA, and Katic MJ. Appendix A: Craniofacial norms in North American Caucasians from Birth (One Year) to young adulthood.  In L.G. Farkas (Ed.), Anthropometry of the Head and Face, 2^nd, New York, Raven Press, 1994.

2-Gioia VM, Linberg JV, McCormick SA (1987) The anatomy of the lateral canthal tendon. Arch Ophthalmol; 105(4):529-532.

3-Most SP, Mobley SR, Larrabee WF Jr (2005) Anatomy of the eyelids. Facial Plast Surg Clin North Am; 13(4):487-492.

4-Lexer E, Eden R (1911) Uber Die Chirurgische Behandlung Der peripheren facialislahmung. Beitr KlinChir; 73:116.

5- Sheehan JE (1927) Plastic Surgery of the Orbit. New York: Macmillan.

6- Hinderer UT (1993) Corretion of weakness of the lower eyelid and lateral canthus. Personal techniquesc. Clin Plast Surg; 20(2):331-349.

7- Whitaker LA (1984) Selective alteration of palpebral fissure form by lateral canthopexy. Plast Reconstr Surg; 74(5):611-619.

8- Whitaker LA (1984) Selective alteration of palpebral fissure form by lateral canthopexy. Plast Reconstr Surg; 74(5):611-619.

9- Flowers RS (1987) Advanced blepharoplasty: Principles of precision. Gonzalez-Ulloa M, et al (eds), Aesthetic Plastic Surgery, vol 2. Padua: Piccin Nuova Libraria, 115.

10- McCord CD, Boswell CB, Hester TR (2003) Lateral canthal anchoring. Plast Reconstr Surg; 112(1):222-236.

11-Yaremchuk MJ (2003) Restoring palpebral fissure shape after previous lower blepharoplasty. Plast Reconstr Surg;111(1):441-450.

12- Yaremchuk MJ (2004) Improving periorbital appearance in the “morphologically prone”. Plast Reconstr Surg;114(4):980-987.

LEGENDS

Figure 1- Dimensions of the palpebral fissure measured in young Caucasian women. The mean height of the palpebral fissure measured from the upper lid (P (s)) to lower lid (P(i)) margin at the mid pupil was 10.8 =/- 1.2 mm (n = 200). The mean length of the eye fissure measured from medial commissure to lateral commissure was 30.7 =/- 1.2 mm (n = 200). The mean inclination of the eye fissure was 4.1 degrees =/- 2.2 degrees (n = 50) (Ref1).

Figure 2- Technique of lateral canthopexy. A) Through the lateral extent of the lower lid blepharoplasty incision, the lateral canthus is identified and freed from Whitnall’s tubercle by subperiosteal dissection. B) The lateral canthus is purchased by a figure-of-eight, 30-gauge titanium wire suture. C) The ends of the suture are passed along the lateral orbit from the lower lid to the upper lid (or coronal) incision.  To ensure adequate vertical mobility of the lateral canthus and lateral lid margin, it may be necessary to incise the lateral third of the scarred and contracted lid lamellae. D) Each end of the wire suture is passed from within the orbit through drill holes made in the lateral orbital rim that were placed at the zygomaticofrontal suture and 2-3 mm below it. The ends of the wire suture are twisted to one another over the bridge of bone. Passing the wire from inside to outside the orbit applies the lid to the globe.

Figure 3- The position of the lateral canthus relative to the lateral orbital rim determines the relation of the lower lid to the surface of the globe. A) The lateral canthopexy stitch is passed through the inner surface of the lateral orbital wall and tied on its outside surface. B) The lateral canthopexy stitch is attached to the periosteum of the anterior surface of the lateral orbital rim. Note the gap between the surface of the globe and the lateral aspect of the lower lid.

Figure 4-  A 35-year old woman with Treacher-Collins syndrome underwent augmentation of  her coloboma with custom-carved porous polyethylene implants and  ‘bridge of bone canthopexy’

(Above) Preoperative frontal view. (Below) Frontal view at two years postoperatively.

Figure 5- A 27 year old woman who not had previous orbital surgery desired upward movement of her lateral canthus. (above) Preoperative frontal view). Below (6 month postoperative view.

Figure 6- A 50-year old woman  underwent lower lid blepharoplasty in the past.  She underwent subperiosteal midface lift, infraorbital rim augmentation, and lateral canthoperxy. (Above) Preoperative frontal view. (Below) One year postoperative view.

Figure 7-  A 52 year old woman had undergone previous browlift, rhytidectomy and upper and lower lid blepharoplasty. Lower lid retraction was treated by multiple canthopexies, spacer grafts and full thickness skin grafts. Dry eye symptoms persisted. Infraorbital rim augmentation, midface lift,and lateral canthopexy resolved her symptoms. Her brows and hairline were repositioned. A) Preop frontal view. B) Postop frontal view at 2 years..

Figure 8  In young adults with normal skeletal morphology the palpebral fissure is long and narrow. With aging, descent of the lower lid and medial migration of the lateral canthus rounds the shape of the palpebral fissure. Standard blepharoplasty techniques which remove lower lid skin (and often muscle) tend to lower the lower lid margin further rounding the palpebral fissure. Canthoplasty procedures, by design, alter the shape of the palpebral fissure since they disassemble and reassemble the lateral canthus while shortening the lower lid margin. Lateral canthopexy, since it does not violate the lid margin, maintains, or has the potential to restore, palpebral fissure shape including the lateral canthal angle.