Pretutorial
    Assessment

Tutorial
Introduction
Etiology of Peg        Complications
Treatment
Tips on How to        Succeed with        Prosthetic Pegs
References

Slides

Managing Complications Associated with Pegging and Tips for Successful Peg Placement

David R. Jordan, MD

Introduction

Porous orbital implants (e.g., hydroxyapatite, porous polyethylene, aluminum oxide) are commonly used during enucleation, evisceration, and secondary orbital implant surgery.¹ The extensive pore systems permit fibrovascular ingrowth, which helps the implant resist migration, which is a problem not uncommonly seen with previous non-porous implants. By attaching the extraocular muscles and coupling the prosthesis to the orbital implant using a peg system, an improved range of motion, as well as fine darting eye movements that occur in synchrony with the contralateral eye (imparting a more life-like appearance to the prosthesis), can be obtained.² A recent infrared oculography study demonstrated significant objective improvement in horizontal gaze after motility peg placement.³ Despite the improved motility and life-like appearance created, many surgeons elect to avoid peg placement due to the possibility of post-pegging complications.^2,4-6

Generally, peg systems are designed for peg placement once fibrovascularization of the implant has been completed as drilling into an avascular area of an implant may predispose the implant to infection.⁷ Gadolinium-enhanced magnetic resonance imaging is currently the recommended method of assessing the extent of implant vascularization.⁸ Fibrovascular ingrowth may occur at varying rates in different patients. The author defers implant drilling and peg placement until 6 months following porous implant insertion.

SLIDE 1A

The original peg system was designed for a coralline hydroxyapatite implant (Bio-Eye, Integrated Orbital Implants, Inc., San Diego, CA) and was attached directly to the posterior surface of the prosthesis.⁹ Problems with this peg included difficulty inserting and removing it, as well as patient discomfort.^5,9 This led to the development of the ball-in-socket motility peg, in which the ball-headed portion of the peg remained protruding above the conjunctiva.^9,10 The back of the prosthesis had a corresponding cuplike indentation, creating a ball-in-socket joint.⁹ Once an implant was drilled, a flat-headed peg was initially inserted. In 4 to 5 weeks, the flat-headed peg was replaced with a round-headed peg. A corresponding indentation was made in the posterior surface of the prosthesis at that point to allow coupling of the orbital implant with the prosthesis. To obtain a more secure fit of the orbital implant and peg to the prosthesis, a modification of the ball-in-socket design resulted in a peg-and-sleeve system (Slide 1A), which remains the most popular design. Following drilling of the porous implant, a polycarbonate sleeve is screwed into the implant. A flat-headed polycarbonate peg with a thinner shaft than the original peg is inserted into the sleeve. Several weeks later, the ocularist exchanges the flat-headed peg with a round-headed polycarbonate peg and makes a corresponding indentation in the prosthesis.

Two types of round-headed pegs are available: one with a small head (2 mm) and one with a larger head (4.5 mm). With the 2-mm-head peg, a smaller, deeper indentation can be formed on the posterior surface of the prosthetic eye, creating a tighter coupling of the ball-in-socket type fit. This decreases the chance of the peg coming out of the couple on ductions and usually leads to improved motility of the prosthetic eye.

SLIDE 1B

SLIDE 1C

Several titanium peg systems (ball-in-socket peg and sleeve systems) are available for use with porous orbital implants and have replaced the polycarbonate systems (Slide 1B). Titanium is more biocompatible and better tolerated by human soft tissue than the original peg systems made of polycarbonate.¹¹ Complications associated with peg placement have also been reduced with the introduction of the titanium pegs.¹¹ The FCI peg system (FCI Ophthalmics, Marshfield Hills, MA) has a hydroxyapatite-coated titanium sleeve (Slide 1C), whereas the PK motility system supplied for the Bio-Eye uses a pure titanium peg and sleeve system (Slide 1D).⁷ The hydroxyapatite coating potentially allows stronger interface bonding with the orbital fibroblasts than the uncoated PK system supplied for use with the Bio-Eye. The Medpor motility coupling post (MCP) (Porex Surgical, Newnan, GA) is a titanium screw that can be screwed directly into porous polyethylene implants.^12,13 Some investigators have advocated primary placement of the MCP at the time of implant insertion.^13-15 This practice, however, remains controversial and most North American oculoplastic surgeons defer implant pegging for more than 6 months after implant placement. The Porex Company (Porex Surgical, Inc., Newnan, GA) is currently introducing a magnetic pegging system with a buried stainless steel flat-headed peg and a small but powerful rare earth magnet within the posterior prosthetic eye surface. Although magnetic implants were unsuccessful when used in the 1950s, the newer technology may provide more promising results.

SLIDE 1D

Several potential complications may occur following pegging of a porous orbital implant. Although generally minor, complications often require additional patient visits that would not otherwise have been required if the peg were not in place. In a previous report by the author,⁴ problems developed following peg placement in hydroxyapatite implants in 62 of 165 (37.5%) patients (Table). More than 95% of the pegs used were either the standard polycarbonate peg (53.9%) or the polycarbonate peg and sleeve system (41.8%).⁴ In a subsequent article looking at the hydroxyapatite-coated sleeve and titanium peg-and-sleeve system, many of the complications were similar but occurred less frequently.¹¹

Table 1. Complications associated with peg systems⁴

Slide 2A	Slide 2B
Slide 3A	Slide 3B
Slide 3C

Etiology of Peg Complications

The causes of the various peg complications are multifactorial.⁴ Complications may be related to peg design (e.g., pyogenic granulomas arising from the base of the peg hole or having the peg spontaneously falling out) and were more common when a simple peg (no sleeve) was used. When a sleeve system was introduced, the pegs rarely fell out spontaneously. Pyogenic granulomas occurring at the base of the peg hole were virtually eliminated by the introduction of a sleeve system. However, pyogenic granuloma continued to occur at the interface of the sleeve shaft and conjunctiva (Slide 2A, Slide 2B).⁴ Poor transfer of movement in some instances was due to a round-headed peg and a poor couple to the overlying prosthesis. When a smaller peg (creating a tighter couple) was used, better transfer of movement could be achieved. Other peg complications were due to a disruption in tissue barriers (e.g., exposure of the implant around the sleeve or implant infection), whereas others were secondary to a poor peg implantation technique (e.g., peg drilled on an angle, peg shaft visible or a peg drilled off center) (Slide 3A, Slide 3B, Slide 3C). The most common complaint associated with pegging was discharge, which could not be readily explained by the peg design, a break in tissue barrier, or surgical technique.⁴ Discharge was found to decrease when a titanium peg-and-sleeve system was used in place of polycarbonate; however, it did not completely disappear.⁷ The author proposes that the discharge is attributed to the increased movement of the pegged artificial eye on the conjunctival surface causing a low-grade conjunctival irritation (that may not be clinically evident) with resultant mucous production. Giant papillary conjunctivitis (GPC) is also a known cause for socket discharge in an anophthalmic socket patient and has characteristic papules on the tarsal surface of the upper eyelid. Infection, another cause for discharge, is usually obvious when present and readily treated with antibiotic eye drops.

Treatment

Discharge

Discharge is the most common problem associated with peg systems.⁴ In a study, the author found discharge to occur in 24% of patients with a polycarbonate peg system and 7.4% of patients with a titanium peg system.^4,11

When faced with a patient with discharge, it is important to rule out conjunctival infection on clinical examination and laboratory testing (culture). The symptoms and signs are usually obvious (conjunctival inflammation and discharge). If infection is suspected, then a broad-spectrum topical antibiotic is suggested four times daily for 2 weeks. The socket should also be examined for pyogenic granuloma; recurrent discharge is associated with pyogenic granuloma.

More commonly, a patient presents with discharge, no pyogenic granuloma, and a normal or only mildly inflamed conjunctiva. If the patient's implant has not been polished for 6 months, the first step in management of the discharge is to see an ocularist for cleaning and polishing as a rough prosthetic surface or a prosthesis with protein build up can lead to unnecessary socket discharge. A search for GPC is also important, as it too may be a cause for recurring discharge. If no signs of GPC, infection, or pyogenic granulomas are present, then a mild antibiotic-steroid drop such as Tobradex (tobramycin/dexamethasone, Alcon) once or twice daily often helps the discharge. For persistent discharge, once or twice weekly cleaning of the prosthetic eye with soft contact lens daily cleaner is helpful in conjunction with an antibiotic steroid drop. If GPC is present, then a trial of corticosteroid eye drops three to four times daily in conjunction with an allergy drop such as Zaditor (ketotifen fumarate, CIBA) or Patanol (olopatadine hydrochloride, Alcon) may be helpful. Often, a patient must try several combinations of these drops to determine any benefit. In some patients with GPC, a trial of cyclosporine eye drops may be helpful. In other individuals, cryotherapy or carbon dioxide laser application may be of benefit.¹⁶

Pyogenic Granuloma

A pyogenic granuloma, or small tuft of excess healing tissue, was found to be the second most frequent problem associated with pegging in an earlier report.⁴ Although the occurrence of pyogenic granuloma decreased with a switch to titanium pegs, pyogenic granulomas continued to develop.¹¹ A pyogenic granuloma often causes discharge and occasionally recurrent bleeding.⁴ It may encircle the peg or be more frond-like and attach to the conjunctiva by a slender stalk. The initial treatment is simple excision with gentle cautery to the base. If a pyogenic granuloma recurs, the same treatment can be performed again or mitomycin C can be applied.¹⁷ Once the pyogenic granuloma has recurred for a third time, the author prefers to place a scleral patch graft or temporalis patch graft subconjunctivally around the peg site and reclose the conjunctiva.¹⁸ This minor surgery restarts the healing process and may eliminate the source of irritation stimulating the formation of the pyogenic granuloma.¹⁹ Further pyogenic granuloma recurrences should raise the suspicion of implant infection.²⁰

Peg Falling Out

A peg falling out spontaneously was a problem with the early simple peg (no sleeve) systems and rarely occurs with a peg and sleeve system. If the peg comes out with removal of the artificial eye, it is simply replaced into the sleeve. If conjunctiva grows over the sleeve opening, the clinician can create a small conjunctival cut over the sleeve opening and replace the peg.

Poor Transfer of Movement

Poor transfer of movement from the peg to the prosthesis is generally due to poor coupling of the prosthesis to the peg. Using a small-headed peg usually corrects this complication. Occasionally, poor transfer of movement is seen in patients with shortened conjunctival fornices or in patients with poor socket motility from previous surgery. Little can be done for these patients.

Clicking

An ocularist can alleviate clicking with prosthetic eye movement by adjusting the prosthesis.

Technique-Related Complications

Technique-related complications include pegs on an angle, a peg shaft above the implant surface, and off-center pegs. It is important to place the drill hole centrally and pointing straight ahead to avoid these complications.^11,21 It is strongly recommended to perform the drilling procedure with the patient under a light local anesthesia. The sleeve should be flush with the implant and tight. Improper peg placement and a peg on an angle may create coupling problems, discomfort, recurrent discharge, and poor transfer of movement.

Implant Exposure

Implant exposure around the peg or sleeve shaft is a complication that rarely spontaneously resolves. Exposure of the implant is unhealthy as it allows a potential entry site for hair shafts that can become lodged in the implant and contribute to recurrent discharge. The exposure may also allow microorganisms entry into the implant and potential implant infection. For these reasons, the author does not watch and wait when this situation arises. A scleral patch graft or temporalis patch graft is placed subconjunctivally over the peg sleeve and area of implant exposure.¹⁸

Loose Sleeve

A loose sleeve may be due to a faulty sleeve insertion. A sleeve must be screwed in until it is exactly flush with the implant surface (not countersunk, not protruding). The drill hole must therefore be exactly the right depth (10 mm) to hold the sleeve. The sleeve must also be screwed in place until tight. The loose sleeve may also be due to a wear and tear process occurring in an implant that has structural weakness. When a loose sleeve occurs, the clinician can insert a larger sleeve shaft in the same drill hole; however, the sleeve hole may be too big for the largest sleeve. In this instance, the clinician should remove the peg and sleeve and fill the hole.^22-25

Implant Infection

Infection is the most serious complication associated with pegging as it often leads to implant removal.²⁰ The hallmarks of implant infection are discharge, recurrent pyogenic granulomas, and implant exposure despite antibiotic drops and implant adjustment. At times, implant infection may be subtle and it is only with a continued development of signs and symptoms that an implant infection is suspected. Once an implant infection occurs, implant removal is inevitable.^20,26,27

Tips on How to Succeed with Prosthetic Pegs

Oculoplastic surgeons have gradually moved away from pegging porous orbital implants primarily due to the satisfactory movement obtained with using a porous orbital implant and the risk of potential complications occurring with pegs. However, when one compares a successfully pegged prosthetic eye with a non-pegged one, the range of motion and lifelike appearance is better in the pegged implant. A pegged prosthetic eye moves in synchrony with the real eye and has the fine, darting eye movements that can be seen when engaged in close conversational speech. However, pegging is not for every patient with a porous implant and also not for every physician using porous implants.

Tips to a successful pegging procedure include:

• Choosing a healthy, responsible patient. The ideal patient to peg is between 20 and 65 years of age and healthy. Patients with systemic disease such as diabetes, collagen vascular disease, sarcoidosis, or any disease requiring corticosteroids or medications such as methotrexate or anticancer medication should not be considered.²⁷ In this author's view, a past history of socket radiation is also an absolute contraindication to pegging as the socket vascularity is reduced.
  
  
• Surgical technique. Switching from a polycarbonate (plastic) peg system to a titanium peg and sleeve, as well as a meticulous surgical technique under local anesthesia with intravenous sedation, will help decrease several of the common peg problems (e.g., discharge, pyogenic granuloma, off-center peg, peg on an angle, and visible shaft).¹¹ A clear plastic conformer with the ideal peg site drilled out is placed into the socket and the conjunctiva is marked with a gentian violet marker. A preliminary drill hole is made in the implant with a 25-gauge needle.^11,21 The patient is sat up to see if the 25-gauge needle is centered or at an angle. If the needle is not straight, it can be removed and realigned. The patient is again placed into a supine position and the initial drill hole is enlarged with an 18-gauge needle. The patient is again sat up and the centration is rechecked. If the peg hole is still centered well, the surgeon then creates a hole precisely 10-mm deep with the hand-held drill bit. The sleeve is screwed in until it is tight and flush with the implant, not countersunk or protruding. A flat-headed peg is put into position within the sleeve. A double layer closure (Tenon's tissue then conjunctiva) is then carried out. A round-headed peg replaces the flat-headed peg in approximately 3 months. This time allows the implant tissue to develop a secure attachment to the hydroxyapatite sleeve shaft.
  
  
• Follow-up and prosthetic care. Patients with pegs must be followed by the ophthalmologist and ocularist and encouraged to take care of their prosthetic eye. Early recognition of peg problems may prevent more serious ones from occurring. Proper maintenance of the prosthesis may also prevent problems from developing. Generally, a patient with a peg should be seen 1 to 2 weeks following the peg procedure, just before the ocularist couples the peg to the prosthesis at 8 to 10 weeks, and then in 3 months, 6 months, and annually. If the patient lives a long distance away and is not willing to return periodically, pegging should be reconsidered. The author does not recommend pegging in pre-teens or teens as they are generally not mature enough to appreciate that regular follow-up visits, as well as proper prosthetic eye maintenance, are important.
  
  

Loss of an eye to tumor, trauma, or end-stage ocular disease is devastating to patients of any age. A patient experiences a loss of binocular vision with reduced peripheral visual field and loss of depth perception with various job restrictions, as well as a sense of facial disfigurement. One's self-image, self-esteem, and self-confidence may be affected. In the past decade, anophthalmic socket surgery has advanced significantly in terms of implant wrapping, implant-prosthesis coupling, and socket volume considerations. It is now possible to provide an anophthalmic patient with an artificial eye that looks and moves almost as naturally as a real eye. Peg placement is an important component of this restoration but is not for every patient or for every surgeon implanting porous orbital implants. Selecting the right patient and following a meticulous technique, as well as continued follow-up, are key to successful peg placement.

References

1. Jordan DR, Klapper SR. Anophthalmic orbital implants: Current concepts and controversies. Comprehensive Ophthalm Update. 2005;6:287-295.
   
   
2. Su GW, Yen MT. Current trends in managing the anophthalmic socket after primary enucleation and evisceration. Ophthal Plast Reconstr Surg. 2004;20(4):274-280.
   
   
3. Guillinta P, Vasani SN, Granet DB, Kikkawa DO. Prosthetic motility in pegged versus unpegged integrated porous orbital implants. Ophthal Plast Reconstr Surg. 2000;19:119-122.
   
   
4. Jordan DR, Chan S, Mawn L, Gilberg SM, Brownstein S, Hill V. Complications associated with pegging hydroxyapatite orbital implants. Ophthalmology. 1999;106:505-512.
   
   
5. Edelstein C, Shields CL, DePotter P, Shields JA. Complications of motility peg placement for the hydroxyapatite orbital implant. Ophthalmology. 1997;104:1616-1621.
   
   
6. Lin CJ, Liao SL, Kao SCS, et al. Complications of motility peg placement for porous hydroxyapatite orbital implants. Br J Ophthalmol. 2002;86:384-396.
   
   
7. Klapper SR, Jordan DR, Ells A, Grahovac SZ. Hydroxyapatite orbital implant vascularization assessed by magnetic resonance imaging. Ophthal Plast Reconstr Surg. 2003;19:46-45.
   
   
8. Ainbinder DJ, Haik BG, Tellado M. Hydroxyapatite orbital implant abscess: Histopathologic correlation of an infected implant following evisceration. Ophthal Plast Reconstr Surg. 1994;10:267-270.
   
   
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15. Tawfik HA, Dutton JJ. Primary peg placement in evisceration with the spherical porous polyethylene orbital implant. Ophthalmology. 2004;111:1401-1406.
    
    
16. Belfair N, Monos T, Levy J, Mnitentag H, Lifshitz T. Removal of giant vernal papillae by CO2 laser. Can J Ophthalmol. 2005;40(4):472-475.
    
    
17. Popp JC. The use of mitomycin C for the treatment of pyogenic socket granulation tissue associated with motility pegs. J Ophthalmic Prosthetics. 1996;1:25-27.
    
    
18. Pelletier C, Gilberg S, Jordan DR. Use of temporalis fascia for management of exposed hydroxyapatite implants. Ophthal Plast Reconstr Surg. 1998;14(3):198-203.
    
    
19. Jordan DR, Brownstein S, Lee-Wing M, Ashenhurst M. Pyogenic granulomas following oculoplastic procedures: An imbalance in angiogenesis regulation. Can J Ophthalmol. 2001;36(5):260-268.
    
    
20. Jordan DR, Brownstein S, Dorey MW. Clinical-pathologic analysis of 15 explanted hydroxyapatite implants. Ophthal Plast Reconstr Surg. 2004;20(4):285-290.
    
    
21. Jordan DR, Klapper S. Drilling the synthetic hydroxyapatite implant. Can J Ophthalmol. 1999;34(1):30-32.
    
    
22. Jordan DR. Spontaneous loosening of hydroxyapatite peg sleeves: A new problem to contend with. Ophthalmology. 2001;108:2041-2044.
    
    
23. Jordan DR. Repairing the hole in hydroxyapatite orbital implants following peg removal. Ophthalmic Surg Lasers. 2000;31(5):438-440.
    
    
24. Jordan DR. Spontaneous loosening of peg sleeves (letter). Ophthalmology. 2002;109(8):1413-1415.
    
    
25. Heringer DM, Ng JD. A novel approach to re-pegging hydroxyapatite implants using bioactive glass. Ophthal Plast Reconstr Surg. 2005;22(1):45-47.
    
    
26. Jordan DR, Brownstein S, Dorey M. One patient with infection at different times of 2 hydroxyapatite implants, each requiring explantation. Can J Ophthalmol. 2003;38:406-409.
    
    
27. Jordan DR, Klapper S, Mawn L, Brownstein S, Punja K. Abscess formation within a synthetic hydroxyapatite implant: report of a case. Can J Ophthalmol. 1998;33(6):329-332.