Evaluation of biomatrix hydroxyapatite ocular implants with technetium-99m-MDP.
ABSTRACT Hydroxyapatite ocular implants appear to offer excellent cosmetic reconstruction with lower rates of infection and extrusion compared to other integrated implants. However, vascularization of the implant needs to be established before the artificial eye is attached to the implant. Technetium-99m-methylene diphosphonate (MDP) scintigraphy can be utilized as a noninvasive method for determining the vascularity of the hydroxyapatite ocular implants. A case is presented in which 99mTc-MDP uptake in the implant was deemed sufficient for further surgical intervention.
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ABSTRACT: This study evaluated the morphogenetic properties of osteogenic composites of bone matrix and porous coralline hydroxyapatite (HA) replicas after intramuscular implantation in adult baboons (Papio ursinus). Composite implants were prepared by inserting rods of nonresorbable HA replicas, 20 mm in length, and 5 or 7 mm in diameter, into the medullary canals of 90 diaphyseal baboon bone cylinders, 20 mm in height, sequentially extracted and chemosterilized to obtain autolysed antigen-extracted allogeneic (AAA) bone matrix, preserving the bone morphogenetic protein (BMP) activity. Composites were implanted in the rectus abdominis and in the dorsal musculature of 24 adult male baboons. Before implantation, 45 composites were coated with an allogeneic fibrin-fibronectin protein concentrate (AFFP) prepared from fresh-frozen baboon plasma. Histologic analysis of undecalcified and decalcified specimens procured at 3, 6, and 9 months showed bone differentiation by induction along the endosteal surfaces of the chemosterilized matrix and within the porous spaces of the HA substratum. Bone formation was often extensive, culminating in complete penetration of the porous spaces. Histomorphometry showed that bone in the HA substratum increased at each time period. The biochemical treatment of the composite implants with AFFP did increase significantly the amount of induced bone, although only in the HA substratum. Bone differentiation was confirmed by fluorescence microscopy of the mineralization fronts after intravital double tetracycline labeling. The differentiation of bone in composites of bone matrix and porous HA replicas in extraskeletal sites of adult baboons may help to design appropriate delivery systems for the controlled therapeutic initiation of bone formation for craniofacial and orthopedic applications in man.Journal of Oral and Maxillofacial Surgery 09/1991; 49(8):817-30. · 1.33 Impact Factor
after placement of the implant (2).
explain this need for a delay of 6 mo before imaging, as
well as its avidity for bone imaging agents.
tivity refers to the ability of the material to promote the
growth of bone without being in contact with an osseous
bed. Experimental work has shown that new bone for
mationmay occurin extraskeletally
droxyapatitewithin 3 mo, but that
MDP scintigraphy is a noninvasive method of evaluating
the successfulintegration into the normal orbital tissues
and thereforethe optimal time for coupling with the arti
ficial eye to afford motility.
the recommendedtime for evaluationis 6 mo
it is most
A 47-yr-old male underwent enucleation of left eye for a
predominantlyspindle cell ocular
droxyapatiteocular implant placement
suturing of extraocular muscles to the implant. The patient
returned on September10, 1991 for evaluation
and possible preparation for motility coupling. Technetium
99m-MDP scintigraphy (Figs. 1 and 2) on September 10, 1991
demonstrates 4+ uptake (activity in the implant greater than
activityin the midfacialbones)
indicating ingrowth of fibrovascular tissue. SPEC!' imaging
(Fig. 2) was also performed on this patient,
intense uptake, but did not add further information
viability of the implant. Following the scan, the hole was drilled
and the artificial eye was attached. Viability was confirmed
clinically. The implant has functioned
on August 3, 1990 with
of the implant
of radiotracerin the implant
normally without compli
Perry (2) has defined a grading system for characteriz
ing the uptake of radiotracer
uptakein the implant greater
bones,3+ is equal to the midfacial bone, 2+ is midway
betweenthe midfacial bones and the normal orbit, while
1+ is greaterthan the normalorbit but not quite 2+.
Uptake of 2+ or better in the implant demonstrates the
successful ingrowth of fibrovascular
plant (2). This integrationis necessary
the implant for coupling to the artificial eye. The coupling
than that in the midfacial
Uptake of 4+ is
tissue into the im
Hydroxyapatite ocular implants appear to offer excellent cos
metic reconstruction with lower rates of infection and extru
sion compared to other integrated implants. However, vas
culanzation ofthe implant needs to be established before the
artificial eye is attached to the implant. Technetium-99m-
methylene diphosphonate (MDP) scintigraphy can be utilized
as a noninvasivemethodfor determiningthe vascularityof
the hydroxyapatite ocular implants. A case is presented in
which@â€˜Tc-MDPuptake in the implant was deemed suffi
cient for further surgical intervention.
scintigraphyis used in the evaluation
as a bone replacementagent (1). A new application
use as a noninvasive method
larity of hydroxyapatite ocular implants. Ocular implants
are used to replace the volume of the orbit following
enucleation as well as to allow the artificial eye to move
in conjunction with the normal eye when the artificial eye
is coupled to the implant. Hence, these implants are also
referred to as direct motility implants
Hydroxyapatiteocularimplantsare madeof calcium
phosphate,a normal constituent
connectingnetwork of channels
bone (3). This porousconfiguration
of fibrovascular tissue and integration of the implant into
the normal orbital tissues.It is this integration
fords this particular implant its many advantages (1,3,4).
First, it does not react like a foreign substance in the
tion. Third, the implant appears
to infection.Last,it can be utilized as a direct motility
implant after integration into the normal orbital tissues.
Pathologic studies in humans and animals (5,6) indicate
fibrovascular ingrowth in a period as little as four weeks.
for determiningthe vascu
of bone, with an inter
allows the ingrowth
to be relatively
Received Jul. 16, 1992; revIsion accepted Oct. 14, 1992.
For correspondenceor reprints contact: Andrew Taylor, Jr., MD, Depart
ment of Radiology, Emory University, 1364 ClIfton Road, N.E., Atlanta, GA
Evaluation of Ocular Implants â€¢ Baumgarten et al.
Evaluation of Biomatrix Hydroxyapatite
Ocular Implants with Technetium-99m-MDP
Deborah Baumgarten,Ted Wojno and AndrewTaylor,Jr.
DepartmentsofRadiologyand Ophthalmology,EmoiyUniversity SchoolofMedicine,Atlanta, Georgia
FIGURE3. Motility implant showing vascular ingrowth and
ball and socket coupling to the artificial eye (Reprinted with
permissionfrom Arthur C. Perry).
assured with a positive
tion is incomplete,
can result in failure of the coupling procedure
sion of the implant (2).
should be delayed until vascularization
@Tc-MDPscan. If the integra
exposure of the implant during drilling
The authors thank Nettie Sutton for her assistance
FIGURE 1. Anterior (A)andleftlateral (B)images ofthehead
prominentuptakein the hydroxyapatiteocular implant.
of @â€œTc-MDP show
into a hole drilled into the implant and then coupled to the
artificial eye by a ball-andsocket
uptake in the implant is not at least 2+, motility
by means of a motility peg which is placed
type joint (Fig. 3). If
The Journal of Nuclear Medicine â€¢Vol. 34 â€¢ No. 3 â€¢ March 1993
1. Patka P, Dean Hollander
bone replacement. I Nuci Med 1985;26:263â€”271.
3. Perry AC. Advancesin enucleation.
4. Dutton JJ. Corallinehydroxyapatite
5. ShieldsCL, ShieldsJA, Eagle RC, DePotter P. Histopathologic evidence
of fibrovascular ingrowth four weeks after placement of the hydroxyap
atite orbital implant. Am I Ophthahnol
6. Perry AC. Integratedorbital implants.
and reconstructivesurgery. Surgery 1990;8:75â€”81.
7. Ripamonti U. The induction of bone in osteogenic composites of bone
matrix and porous hydroxyapatitereplicas: an experimental study on the
baboon (papio ursinus). I Oral Maxillofac Sw@ 1991;49:817â€”830.
8. RipamontiU. The morphogenesis
droxyapatiteobtained from conversion of calcium carbonate exoskele
tomis of coral. I Bone Joint Su,@ 1991;73A:692-703.
W, Den Otter 0, Heindendal
studies to evaluatestability of ceramics
GAK, Dc Root K.
Ophthalmol Clin NorthAm 1991;4:
as an ocular implant.Ophthalmology
of bone in replicasof poroushy