 |
|
Pediatric Enucleation
Analysis of Volume Replacement
Sara A. Kaltreider, MD;
Lilian R. Peake, MD, MPH;
Bruce T. Carter, MD
Arch Ophthalmol. 2001;119:379-384.
ABSTRACT
| |
Objectives To determine the percent volume replacement by an implant and prosthesis,
the long-term sequelae of poor volume replacement, and specific guidelines
for volume replacement in pediatric patients.
Methods A retrospective observational study of 16 pediatric patients who underwent
enucleation (group 1) and 31 adult patients enucleated in childhood (group
2) was performed. The total volume replacement and the volume replacement
by the implant were determined. The incidence of secondary surgical procedures
for superior sulcus deformity, enophthalmos, ptosis, ectropion, and socket
contraction was determined.
Results The average percent volume replaced by the implants in group 1 patients
was 68%. The average percent volume replaced by the implants in group 2 patients
was 21%. Seventy-one percent of patients in group 2 underwent secondary implant
surgery to augment volume and eliminate superior sulcus deformity and enophthalmos.
Conclusions The placement of an adequately sized implant in pediatric patients may
obviate the need for secondary augmentation of socket volume in adulthood.
The authors suggest an implant 2 mm less in diameter than the axial length
of the eye in pediatric patients.
INTRODUCTION
SPECIFIC recommendations regarding implant size for pediatric patients
undergoing enucleation do not exist. The concept that the surgeon should replace
what is removed by enucleation dates back to 1951 when the volume of the globe
was thought to be 6.5 mL.1 The concepts that
total volume replacement should be the goal of rehabilitation and that doing
so reduces superior sulcus deformity and enophthalmos have been reintroduced
in the recent literature.2-4
State-of-the-art enucleation prior to 1999 involved removal of the eye
without consideration of the volume that was removed nor the distribution
of the replacement volume between the implant and the prosthesis. Sizers and
guesswork were (and still are) used in a subjective fashion to ascertain implant
size.
DePotter et al5 found that pediatric
patients do well clinically with implants 16 to 20 mm in diameter.5 In their study, the size of the implant inserted was
based on the patient's age. The study by Fountain et al6
shows that implants 15 mm to 19 mm in diameter provide sufficient orbital
bony growth such that differences between the 2 orbits are insignificant and
difficult to detect on external examination. Neither study presents an analysis
of the volume removed and replaced. Neither study suggests individualization
of the implant size based on the size of the enucleated specimen or a preoperative
A-scan of the remaining eye.
An analysis of effective volume replacement is meaningless without knowledge
of the volume removed. The current concept of adult globe size is based on
3 recent articles that establish an average volume of 7.9 mL (range, 6.9-9.0
mL) and a range of axial lengths of 21 mm to 29 mm.2-4
The concept of individualizing the implant size based on either the size of
the removed specimen or an A-scan of the remaining eye was introduced by 2
of these articles.3-4 In pediatric
patients, the implant sizes projected to replace 70% to 80% of the volume
removed were in the range of 18.5 to 22 mm in diameter, leaving 20% to 30%
of the volume to be supplied by the prosthesis.3
Pediatric enucleation involves removing an eye that has not reached
adult size; therefore growth must be addressed in any investigation of pediatric
enucleation. An eye achieves 85% or more of its axial length by the age of
2 years, and continues to grow 1% per year until its final size is reached.7 An issue that arises in pediatric patients is the
potential need for implant exchange with secondary insertion of larger implants
into the muscle cone as growth occurs.8 This
becomes problematic if one uses porous implants in the muscle cone because
the dissection required for implant removal could damage the extraocular muscles
and their innervation, or create restrictive fibrous tissue planes that inhibit
motility. We hypothesize that larger implants may be used at the time of primary
enucleation, thus making larger secondary implants unnecessary in many instances.
Fundamental questions are (1) Is the volume removed by enucleation in
a pediatric patient being adequately replaced by the implant and prosthesis?
To answer this question, one must compare the volume removed with the total
volume used to replace the globe, including the implant and the prosthesis.
(2) What are the sequelae of implants that do not replace enough volume in
the posterior socket in pediatric patients? (3) What implant sizes (percent
volume replacements) are associated with the need for secondary procedures
to augment soft tissue volume? (4) What critical volume replacement should
be achieved to prevent asymmetry of bony orbital development? (5) Should replacement
of a larger percentage of the volume be considered in pediatric patients to
compensate for growth of the eye and orbit to adult size? (6) Can we anticipate
a certain percent change in the relative percent volume that the implant provides,
and then replace a larger percentage of volume to compensate for this growth?
(7) What are specific guidelines for determining appropriate implant size
in pediatric patients?
PATIENTS, MATERIALS, AND METHODS
PATIENTS
Forty-seven consecutive anophthalmic patients who had undergone enucleation
in childhood were studied retrospectively, including pediatric patients (group
1, n = 16; age range, 3.5-16 years), and adult patients who underwent enucleation
in childhood (group 2, n = 31; age range, 17-71 years). None of the patients
had a diagnosis of congenital microphthalmos. Only 1 patient (patient 26,
group 2) had a history of radiation treatment to the eye socket. Table 1 presents individual patient data.
Group 1 patients underwent enucleation between 1988 and 1998 by 6 different
surgeons using similar techniques. After informed consent, the patients underwent
enucleation under general anesthesia. Conjunctiva was preserved in each case.
Fifteen of 16 patients had a hydroxyapatite sphere implant and 1 patient had
a silicone implant. Sizers were used to estimate appropriate implant size
for 4 patients. One patient's operative report showed documentation of the
axial length of the globe. No specific means of determining implant size was
noted in the remaining cases. Extraocular muscles were attached to wrapping
around the spherical implant, except in 1 case in which the muscles were "imbricated."
Tenon's capsule and conjunctiva were closed in separate layers.
Patients in group 2 underwent enucleation in childhood and most of these
patients (74%) came for evaluation of eyelid or socket problems during 7 years.
Other patients (26%) returned for continuing follow-up after enucleation.
Clinical problems following enucleation were documented, including implant
exposure and infection, proptosis, enophthalmos, ptosis, superior sulcus deformity,
ectropion, implant migration, and socket contraction. Operative reports were
reviewed to obtain the diameter of the implant used (Table 1). In 6 of 8 patients (group 2) who underwent enucleation
between 1978 and 1982, operative reports were available but none documented
method(s) of implant size determination.
Pathology reports containing the axial length of the enucleation specimen
were obtained in 12 of 16 patients in group 1, and 8 of 31 patients in group
2. A-scan ultrasonography of the remaining eye was available in 5 of 16 patients
in group 1, and in 21 of 31 patients in group 2.
Prosthetic volume was determined by the volume displacement of an alginate
cast of the prosthesis in 7 patients in group 1 and 15 patients in group 2
(>10 months after enucleation). A clay cast of the patient's prosthesis was
made. Alginate was injected into the cast and allowed to set. The alginate
cast was removed from the clay mold, and the volume was determined by volume
displacement to the nearest 0.05 mL.
Plain x-ray skull films (anterior to posterior views) were available
in 5 patients (group 2) for comparison of the anophthalmic and normal orbital
entry at the level of the orbital rim. Horizontal and vertical measurements
of both sockets were obtained.
Surgical procedures performed on the eyelids or sockets on the anophthalmic
side after the date of the primary enucleation were documented. The average
length of follow-up for group 1 was 3 years, and for group 2 was 29 years.
VOLUME CALCULATIONS
All of the volume calculations were based on the primary implant and
the corresponding optimal prosthesis 10 months or more following enucleation.
The volume removed was calculated using the axial length of the enucleated
specimen (to the nearest 0.5 mm), and/or estimated by an A-scan measurement
of the contralateral eye. The formula 4/3 r3 was used to determine
the volume of the eye, with r = axial length (from the pathology report) or
r =  (A-scan measurement + 1 mm). Although the eye is not a perfect
sphere, the axial length corresponds to the A-scan, a clinically accessible
and useful parameter for estimating premorbid ocular volume.3
The volume replaced by the implant was calculated from the radius of
the implant using the formula 4/3r3, or by volume displacement
if the implant was not spherical (to the nearest 0.05 mL). The volume of the
prosthesis plus the volume of the implant was the total volume replaced. The
percent volume replaced by the implant was the volume of the implant divided
by the volume removed times 100. The percent total volume replacement was
the volume of the implant plus the volume of the prosthesis divided by the
volume removed times 100.
Calculations of volume replacement at the time of enucleation (volume
removed based on axial length of the enucleation specimen) and at a distant
follow-up examination (volume removed based on the A-scan of the remaining
eye) were available in 6 patients. These measurements allowed observation
of the change in percent volume replacement by the implant as growth occurred.
In group 2, the means of percent volume replacement in subgroups with
and without superior sulcus deformity, enophthalmos, ptosis, ectropion/laxity,
and socket contraction, were compared for statistical significance using the
2-tailed t test. Confidence intervals were stated
in terms of P values.
RESULTS
A trend toward greater volume replacement was noted in the more recent
enucleations (group 1) (Figure 1).
Two patients in group 1 required secondary implants because of implant exposure
and infection, not for volume supplementation. The exposure in these 2 patients
correlated clinically with anteriorly malpositioned implants.
|
|
|
|
The percentage of group 1 (16 pediatric patients who underwent enucleation)
and group 2 (31 adult patients undergoing enucleation in childhood) patients
requiring secondary surgery for insufficient volume, ptosis, socket contraction,
and ectropion/laxity.
|
|
|
In group 2, 77% of patients had superior sulcus deformity and 71% of
patients had secondary implant surgery to increase volume replacement because
of insufficient volume replacement by the primary intraconal implant. Two
patients with 13% and 30% volume replacement by the implant had superior sulcus
deformity but chose not to have surgery to augment the volume replacement.
Four patients in group 1 (25%) had ptosis, and only 1 of them underwent
ptosis repair. In group 2, 20 patients (64%) had ptosis, and 13 of those patients
(63%) had ptosis repair. The mean percent volume replaced by the implant in
group 2 patients with ptosis was 30%, whereas the mean percent volume replaced
by the implant in group 2 patients without ptosis was 84%. The comparison
of the means (group 2) using the 2-tailed t test
was statistically significant (P<.01).
Two patients in group 1 had mild socket contraction but did not require
mucous membrane grafting for reconstruction of the fornices. Eight of 9 patients
in group 2 who had socket contraction required mucous membrane grafting. Comparison
of the mean percent volume supplied by the implant in group 2 patients with
socket contraction (21%) to the mean percent volume supplied by the implant
in group 2 patients without socket contraction (45%) was statistically significant
(P<.05).
Eight patients in group 2 underwent horizontal shortening of the lower
eyelid. Comparison of the mean volume replaced by the implant in group 2 patients
(28%) to the mean volume replaced by the implant in group 2 patients without
ectropion or lower eyelid laxity (42%) was statistically significant (P<.01).
x-Ray films were available for 5 patients from group 2. Two patients
(aged 4 and 5 years) had no implant, 1 patient (aged 5 years) had a 15-mm
implant, 1 (aged 7 years) had a 1.8-mL nonspherical implant, and 1 (aged 5
years) had an implant of unknown size. The anophthalmic orbits were smaller
in 4 of 5 patients. Enlargement of the ethmoid air cells on the side ipsilateral
to the enucleation was evident on 1 x-ray film. The area of the orbital entry,
determined by multiplying the horizontal and vertical dimensions measured
on the anterior to posterior skull x-ray film, was 68% to 100% of the value
on the normal side.
COMMENT
Adult patients undergoing enucleation in childhood provide an opportunity
to assess the effects of volume replacement in the intraconal implant. This
study demonstrates that group 2 patients, undergoing enucleation from 1932
to 1985, with 21% volume replacement by the implant (range, 0%-44%), had grossly
inadequate posterior volume replacement. Seventy-seven percent of patients
had superior sulcus deformity, and 92% of those patients had secondary orbital
implant surgery to supplement volume replacement in the posterior compartment.
Poor volume replacement by the implant had a statistically significant association
with superior sulcus deformity, enophthalmos, ectropion/lower eyelid laxity,
and ptosis. Clearly, the insertion of an implant that replaces only 21% of
the volume removed is insufficient, and predestines the patient to the pain
and morbidity of additional orbital surgery to correct posterior volume deficiency.
This observation underscores the need for meticulous planning of volume replacement,
including a preoperative A-scan of the opposite eye, intraoperative measurement
of the axial length of the enucleated specimen, and appropriate selection
of implant size.
The mean follow-up time for patients (group 2) with superior sulcus
deformity was 37 years, and for patients without superior sulcus deformity,
19 years. A trend of placing larger implants is noted. Progressive, undefined
physiologic and anatomic changes may also occur. Fat atrophy has been generally
accepted as a cause of superior sulcus deformity but is not substantiated
by scientific evidence.9 Several studies have
shed doubt on this mechanism. Kronish et al10
found no evidence of fat atrophy following enucleation in a primate animal
model. Smit et al11 studied computed tomographic
scans of anophthalmic sockets and documented a rotation of the orbital contents
posteriorly and inferiorly, accounting for deepening of the superior sulcus.
More complete volume replacement in the anophthalmic socket has been shown
to improve superior sulcus deformity.3 A prospective
study is underway to determine if placing an implant 2 mm less in diameter
than the axial length will eliminate superior sulcus deformity in uncomplicated
enucleation.
Based on the following observations, implants larger than those traditionally
placed in pediatric eye sockets may be used in pediatric patients: (1) The
eye is more than 85% of its adult size by age 2 years.7
(2) The axial lengths and A-scans of infants and children suggest placement
of implants 18.5 to 22 mm in diameter.3 (3)
Clinical experience indicates that pediatric patients do well with implants
16 to 20 mm in diameter.5 (4) In this study,
22-mm implants were used in 2 patients, both aged 7 years, without complications.
Two instances of implant exposure occurred in group 1 patients (aged 21 months
and 24 months) who had 16- and 18-mm implants, respectively. The exposure
correlated with anterior positioning of the implant in both cases. Clinical
evidence supports that exposure is related more consistently with technique
and implant positioning than with implant size.12
Patients requiring correction of ptosis, socket contraction, and lower
eyelid laxity had statistically less volume replacement at the time of enucleation
than patients not exhibiting these clinical findings. Some secondary eyelid
procedures may be attributed to augmentation of the prosthesis to compensate
for poor volume in the implant, chronic manipulation of the eyelids to insert
and remove a large prosthesis, duration of prosthetic wear, and other factors.
Multiple complex mechanisms contribute to ptosis in the anophthalmic
socket, including levator dehiscence, scarring, and small implant with collapse
of the superior orbital structures.11, 13
Results of this study concur that the latter mechanism may be a contributing
factor, as well as the long-term use of a bulky prosthetic. In group 1, 25%
of patients had ptosis. One patient had ptosis related to mechanical tethering
of the levator in the horizontal closure site, which was confirmed intraoperatively.
In group 2, 64% of patients had ptosis and the comparison of the means of
implant volumes in patients with and without ptosis was statistically significant.
Mean follow-up of patients with (34 years) and without (31 years) ptosis was
comparable. Additional studies of anophthalmic patients with ptosis, first-hand
intraoperative observations of the levator, and perhaps sagittal magnetic
resonance imaging studies will further clarify the multiple mechanisms contributing
to ptosis in anophthalmic patients.
Although socket contraction is an anterior socket phenomenon, lack of
volume in the posterior compartment, forcing maximal replacement in the anterior
compartment, could conceivably contribute to socket contraction.14
Bulky prostheses accumulate dried mucus on the anterior surface, which causes
inflammation and discomfort. Chronic inflammation could instigate fibrous
contraction in the subconjunctival and Tenon's space. The comparison of the
means of volume replacement by the implant in group 2 patients with and without
socket contraction was statistically significant. Difference in mean follow-up
time of patients (group 2) with (41 years) and without (29 years) socket contraction
suggests that duration of prosthetic wear may be a factor in development of
contraction.
Anophthalmic ectropion, or eyelid laxity, may be a consequence of aging
tissues, chronic prosthetic wear and manipulation of the eyelids on insertion
and removal of the prosthesis, excessively bulky prostheses, cicatricial anterior
lamellar changes in the lower eyelid, and other factors. Inadequate volume
of the implant with a compensatory large ocular prosthesis has an effect on
the development of lower eyelid laxity in these patients. The comparison of
the mean percent implant volume between patients with and without ectropion
was statistically significant in group 2 patients. Mean follow-up was similar
in the 2 groups (35 years in those with laxity and 30 years in those without
laxity).
Poor bony development was observed in 3 patients with poor volume replacement.
A relationship has been established between the lack of an implant, or a small
implant, and abnormal orbital bone development in animals and humans.15 A recent study suggests that the bony orbital entry
is minimally affected in pediatric patients who have had 15- to 19-mm implants.6 Follow-up of group 1 patients was short, not extending
past puberty. We suspect that superior sulcus deformity and enophthalmos may
not develop as readily in pediatric patients because poor bone development,
a consequence of poor volume replacement by the implant, means less bony volume
to be filled by the soft tissues. The soft tissue deficit may not be evident
until the implant migrates forward or out of the muscle cone. Larger radiographic
studies of adults who received implants of various sizes as children will
establish meaningful parameters of the critical volume replacement and implant
diameter that will support normal, symmetric bony development.
The status of orbital bony development becomes a key clinical issue
when evaluating patients for secondary intraconal or subperiosteal implants
for volume augmentation. A screening anterior-posterior or Water skull x-ray
film is recommended prior to secondary orbital implants in patients who undergo
enucleation in childhood. The difference in vertical dimension should be subtracted
from the implant diameter. Computed tomographic scans or magnetic resonance
imaging are helpful in some cases to visualize the extraocular muscles, the
existing implant, and their interrelationships.
Six patients having volume determinations in childhood and adulthood
demonstrated a 6% relative negative change in the percent volume replacement
during an average of 14 years. One might consider replacing 6% more of the
volume in the implant for pediatric patients. That is, if 70% to 80% volume
replacement in the implant is desirable in adulthood, then 76% to 86% of the
volume of the globe should be replaced by the implant in pediatric patients.
For example, the eye of a 2-year-old is 85% the size of an adult's eye (average,
7.9 mL), and the volume is 6.7 mL. Replacement of 76% to 86% of 6.7 mL, 5.1
to 5.8 mL, would require a 21- to 22-mm sphere. This leaves 6.7 mL minus 5.1
to 5.8 mL for the prosthesis in childhood (0.9-1.6 mL), and 7.9 mL minus 5.1
to 5.8 mL for the prosthesis in adulthood (2.1-2.8 mL). The pediatric prosthesis
might resemble a scleral shell initially but would be gradually augmented
into adulthood. A recent study demonstrated a range of prosthetic volumes
in adults of 0.75 mL to 4.2 mL.16 A volume
of 1.8 mL produces a thickness conducive to integration and avoids complications
of larger prosthetics (3.0-4.0 mL).16
In this study, as in a previous study, none of the pediatric patients
had an A-scan that was less than 20.0 mm.3
Two patients in group 1 had too much volume replacement by the implant (100%
and 114%), leaving very little flexibility for volume replacement by the prosthesis.
Preoperative planning or an intraoperative observation of the axial length
of the specimen would have avoided overreplacement of implant volume in these
cases.
Infants (2 aged 5 months and 1 aged 8 months) undergoing enucleation
in this study had ocular volumes of 4.3 mL, 5.6 mL, and 7.2 mL, respectively.
Implant sizes of 18 mm, 20 mm, and 22 mm, respectively, could be accommodated
in these infants, leaving adequate space for the prosthesis in each case (Table 2). Measurements of the enucleated
specimen would have provided valuable information in these cases. Unless phthisis
or microphthalmos is present, the diameter of the enucleated specimen will
be greater than the diameter of the selected implant. If one is not treating
a microphthalmic patient with poor bone development, no logical argument exists
that an implant, sized correctly (axial length minus 2 mm), would not easily
fit into an infant socket.
|
|
|
|
Table 2. Pediatric Implant Size*
|
|
|
The authors suggest placing an implant 2 mm less in diameter than the
axial length of the enucleated specimen or 1 mm less than the A-scan measurement
of the other eye. Estimation of implant diameter based on the A-scan of the
opposite eye allows a preoperative decision, requires less intraoperative
calculation than other methods, establishes a guideline for patients with
phthisis and buphthalmos, and is useful for patients undergoing evisceration. Table 2 presents the distribution of the
volume replacement in the implant and the prosthesis if this algorithm is
followed. This approach, combined with deliberate placement of the implant
posteriorly, would account for additional axial growth and optimal augmentation
of the prosthesis.
As the eyes and bony sockets of group 1 patients grow, comparison of
their radiographic results with those of the patients in group 2 will determine
if the increase from 21% to greater than 68% of volume supplied by the implant
dramatically improves their outcomes as adults and eliminates the morbidity
of additional orbital surgery.
AUTHOR INFORMATION
Accepted for publication August 22, 2000.
Corresponding author and reprints: Sara A. Kaltreider, MD, Department
of Ophthalmology, University of Virginia Health System, Box 800715, Charlottesville,
VA 22908-0715 (e-mail: sak5m{at}virginia.edu).
From the Department of Ophthalmology, University of Virginia, Charlottesville.
REFERENCES
| |
1. Culler AM. Enucleation and cosmetic rehabilitation. Arch Ophthalmol. 1951;45:445-457.
FREE FULL TEXT
2. Thaller VT. Enucleation volume measurement. Ophthal Plast Reconstr Surg. 1997;13:18-20.
ISI
| PUBMED
3. Kaltreider SA, Jacobs JL, Hughes MO. Predicting the ideal implant size before enucleation. Ophthal Plast Reconstr Surg. 1999;15:37-43.
ISI
| PUBMED
4. Custer PL, Trinkaus KM. Volumetric determination of enucleation implant size. Am J Ophthalmol. 1999;128:489-494.
FULL TEXT
|
ISI
| PUBMED
5. DePotter P, Shields CL, Shields JA, Singh AD. Use of hydroxyapatite ocular implant in the pediatric population. Arch Ophthalmol. 1994;112:208-212.
FREE FULL TEXT
6. Fountain TR, Goldberger S, Murphree AL. Orbital development after enucleation in early childhood. Ophthal Plast Reconstr Surg. 1999;15:32-36.
ISI
| PUBMED
7. Weiss AH, Kousseff BG, Ross EA, Longbottom J. Simple microphthalmos. Arch Ophthalmol. 1989;107:1625-1630.
FREE FULL TEXT
8. Eppley BL, Holley S, Sadove AM. Experimental effects of intraorbital tissue expansion on orbitomaxillary
growth in anophthalmos. Ann Plast Surg. 1993;31:19-27.
ISI
| PUBMED
9. DeVoe AG. Experiences with the surgery of the anophthalmic orbit. Am J Ophthalmol. 1945;28:1346-1351.
ISI
10. Kronish JW, Gonnering RS, Dortzbach RK, et al. The pathophysiology of the anophthalmic socket, part II: analysis of
orbital fat. Ophthal Plast Reconstr Surg. 1990;6:88-95.
ISI
| PUBMED
11. Smit TJ, Koornneef L, Zonneveld FW, Groet E, Otto AJ. Computed tomography in the assessment of the postenucleation socket
syndrome. Ophthalmology. 1990;97:1347-1351.
ISI
| PUBMED
12. Vistnes LM. Mechanism of upper lid ptosis in the anophthalmic orbit. Plast Reconstr Surg. 1976;58:539-545.
ISI
| PUBMED
13. Kaltreider SA, Wallow IHL, Gonnering RS, Dortzbach RK. The anatomy and histology of the anophthalmic socket: is the myofibroblast
present? Ophthal Plast Reconstr Surg. 1987;3:207-230.
PUBMED
14. Kaltreider SA, Newman SA. Prevention and management of complications associated with the hydroxyapatite
implant. Ophthal Plast Reconstr Surg. 1996;12:18-31.
ISI
| PUBMED
15. Kennedy RE. The effect of early enucleation on the orbit in animals and humans. Trans Am Ophthalmol Soc. 1964;62:459-510.
PUBMED
16. Kaltreider SA. The ideal ocular prosthesis: analysis of prosthetic volume. Ophthal Plast Reconstr Surg. 2000;16:388-392.
FULL TEXT
|
ISI
| PUBMED
 CiteULike  Connotea  Del.icio.us  Digg  Reddit  Technorati  Twitter
What's this?
RELATED ARTICLE
Archives of Ophthalmology Reader's Choice: Continuing Medical Education
Arch Ophthalmol. 2001;119(3):464.
FULL TEXT
|
