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Resorbable Plate Fixation in Pediatric Craniofacial Surgery
Long-term Outcome
Mario J. Imola, MD, DDS, FRCSC;
David D. Hamlar, MD, DDS;
Weiru Shao, MD;
Khalid Chowdhury, MD, FRCSC;
Sherard Tatum, MD
Arch Facial Plast Surg. 2001;3:79-90.
ABSTRACT
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Objective To determine the long-term efficacy of resorbable plate fixation in
pediatric patients undergoing craniofacial surgery for congenital anomalies,
traumatic deformities, or skull base tumors.
Design Retrospective case review.
Materials and Methods Medical records of 57 consecutive cases using resorbable plates and
screws for craniofacial fixation in patients younger than 18 years were analyzed.
Main Outcome Measures The status of bone healing postoperatively (anatomical union, malunion,
delayed union, or nonunion) and any complications or adverse effects (hardware
visibility or palpability, plate extrusion, or infection) were noted.
Results In midfacial and upper face procedures (54 patients) anatomical union
and uncomplicated bone healing occurred in 52 (96%) of the patients. In this
same group, complications (plate extrusion) occurred in 2 patients (3.7%)
and were resolved using conservative treatment without untoward sequelae.
These outcomes are comparable to results using metal osteosynthesis in similar
situations. Costs of resorbable hardware are similar to existing metal fixation
systems.
Conclusions Our data support the use of bioresorbable plate fixation in pediatric
craniofacial surgery as a means of avoiding the potential and well-documented
problems with rigid metal fixation. Indications include fractures and segmental
repositioning in low-stress non–load-bearing areas of the middle and
upper craniofacial skeleton. Although there is an initial learning curve in
using this technology, we believe the benefits are well worth the effort and
represent a major advance in pediatric craniofacial surgery.
INTRODUCTION
A HOST OF techniques and materials for fixation of the facial skeleton
have emerged in the field of craniofacial surgery over the past several decades.
During the last 20 years or more metal plates and screws have been widely
favored as the method of choice to achieve stable internal fixation. While
metal fixation has distinct advantages, several concerns have been raised
when it is used in growing patients. Intracranial translocation of plates
and screws can occur in up to 50% of pediatric cases using metal plates.1 Risk factors for internalization include long plates,
placement over the temporal region, younger patient age, and syndromic craniofacial
dysostosis. The intracranial presence of titanium plates has been shown to
incite inflammatory responses in the adjacent dura and brain tissue, although
no association with specific neurologic dysfunction has been noted.2-3 Several experimental studies have demonstrated
that rigid plate fixation may interfere with craniofacial growth in the pediatric
skull, although this issue remains controversial.4-6
Stress shielding leading to bone atrophy has been debated, and problems with
visibility, palpability, tenderness, and thermal sensitivity have been described.7-9 Additionally, metal
hardware interferes with diagnostic imaging techniques. For these reasons,
some investigators have suggested routine removal of metal fixation once stable
osteosynthesis has been achieved.8-10
As an alternative to metal plate fixation in children, clinicians have
recently taken a greater interest in biodegradable fixation techniques. Resorbable
sutures have long been used to secure bone fragments; however, they have the
same mechanical disadvantages as interosseous wires and cannot provide the
necessary rigidity required in many situations. Early animal experiments in
the development of resorbable fixation of the facial skeleton date back to
the 1970s.11-12 In the past decade,
several researchers have further expanded the feasability of resorbable fixation
in a variety of different animal models eventually leading to clinical application
of these techniques.13-19
The features of an ideal bioresorbable fixation system include the following:
(1) it facilitates internal fixation with the sufficient initial strength
to stabilize bone segments and allow uneventful bone healing, (2) it degrades
predictably and completely after osteosynthesis has restored adequate intrinsic
bone strength, (3) it is biocompatible so as not to induce a significant inflammatory
foreign body response or immunologic reaction, (4) it is technically easy
to use, and (5) it is cost-effective.
Thus far, development of resorbable plates and screws has focused on
polymers that are macromolecular chains composed of repeating subunits.18, 20-21 Two poly-alpha-hydroxy
acids, polyglycolic acid (PGA) and polylactic acid (PLA), are polymers that
have been used in the manufacturing of resorbable suture for several years
and have been the most widely used in manufacturing resorbable plates and
screws. Other polymers include polyglyconate and polydioxanone. Polyglycolic
acid is a hard crystalline polymer that resorbs rapidly and looses virtually
all of its strength within 1 month. Polylactic acid is a semicrystalline structure
with softer amorphous regions of random and loosely packed polymer chains
interspersed between the orderly and more densely packed strong crystalline
regions. Polylactic acid can exist in 2 different isomeric configurations:
poly L-lactic acid (PLLA) or poly-DL-lactic acid (PDLLA). Polyglycolic acid
and PLA are biomolecules that occur naturally in the human body. The physical
properties of the polymers discussed earlier are outlined in Table 1. Polyglycolic acid has the greatest flexural strength but
undergoes the most rapid degradation with the majority of its strength lost
by 6 weeks and complete volume loss by approximately 9 months. Poly-L-lactic
acid is characterized by greater strength and much longer degradation times
(up to 5-6 years) than PLLA. Alternatively, PDLLA is an amorphous polymer
with a lower strength and more rapid degradation (approximately 1 year). Combining
2 or more of PGA, PLLA, or PDLLA homopolymer yields a copolymer with varying
initial strength, rate of strength loss, biodegradation properties, and tissue
tolerance depending on the ratios of the individual polymers used. The glass
transition temperature represents the point above which the material is soft
and flexible allowing manipulation into the desired shape and below which
it transitions into a firm, rigid structure suitable to impart adequate strength
and fixation. This point needs to be sufficiently greater than body temperature
but cannot be so hot as to preclude practical use within a surgical setting.
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Table 1. Physical Properties of the Common Monomeric Polymers Currently
Used in Fabricating Bioresorbable Plates and Screws
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Biodegradation of PGA and PLA occurs in 2 phases.20-21
During phase 1 (hydrolysis phase), water molecules are inserted into the long
macromolecule cleaving it into shorter polymeric chains. As a result, the
plate substrate looses structural integrity and fragments into microparticles.
Subsequently, during phase 2 (metabolic phase), macrophages phagocytize the
small polymer fragments eventually yielding the breakdown products of glycolic
and lactic acid that are eventually metabolized by the liver into carbon dioxide
and water. Over time, the space previously occupied by the resorbable screws
is obliterated by bony ingrowth. In vivo studies have demonstrated that substantial
strength loss occurs early in the resorption process (phase 1) coincident
with the decrease in molecular weight of the polymeric chains. This happens
well before gross evidence of significant mass and volume loss during phase
2 as seen in Figure 1. At present
there are 5 commercially available resorbable plating systems with different
properties based on their individual polymer chemistry as outlined in Table 2.
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Figure 1. Graphic representation of the
bioresorption process for a generic resorbable plating system. Rates of loss
for molecular weight, strength, and mass are shown as relative value changes
over arbritary time units. Note that the plates are rendered biomechanically
ineffective well ahead of visible changes in plate mass and volume.
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Table 2. Commercially Available Craniomaxillofacial Resorbable Plating
Systems and Their Properties
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Several preliminary studies have demonstrated the efficacy of bioresorbable
plating systems in a variety of applications. The most extensive experience
has been for interfragmentary fixation during cranial vault remodeling and
fronto-orbital advancement in infants and young children with congenital craniofacial
anomalies.22-24
More recently the indications have expanded to include bone graft fixation,
upper and midfacial fractures, as well as maxillary and mandibular orthognathic
repositioning.25-30
This study was undertaken to determine the long-term efficacy of resorbable
plate fixation in pediatric patients undergoing surgery for congenital anomalies,
traumatic deformities, or skull base tumors.
MATERIALS AND METHODS
We have been using resorbable plate fixation since April 1997 for a
variety of craniomaxillofacial indications, and our cumulative experience
provided the clinical material for this retrospective review. All pediatric
patients in whom resorbable fixation of the craniomaxillofacial skeleton was
used between April 1, 1997, and March 30, 2000, were identified. Pediatric
patients were defined as those younger than 18 years. The underlying diagnosis
was noted in each case as well as the nature of the surgical procedure performed.
The location, type, and size of plates used as well as the size and number
of screws were noted. During the better part of the study, only one resorbable
plating system (LactoSorb [PLA-PGA copolymer]; W. Lorenz Surgical Inc, Jacksonville,
Fla) was available; hence, most of the surgical procedures were performed
using this resorbable plating system.
Information concerning patient demographics, diagnoses, and surgical
plan were obtained from preoperative clinical assessments, radiographic imaging
studies, and photographs. Intraoperative data detailing the exact procedure
performed and the plates and screws used were obtained from operative notes
and intraoperative photographs. Observations regarding any intraoperative
technical difficulties were recorded. Follow-up data included postoperative
clinic notes, radiographic images, and photographs for all patients.
The critical outcome parameter assessed was the nature of the bony union
achieved. Anatomical union was defined as union of the osseous segments in
the desired position vs malunion where fragments shifted and healed in undesirable
relationships postoperatively. Delayed union was defined as clinical and radiologic
evidence of inadequate osseous healing at 6 weeks and, if the same was present
at 3 months, this constituted nonunion. All early complications were noted
with specific attention to extrusion and wound infection. If plates and screws
were visible or palpable through the skin, this finding was noted as well
as the eventual outcome of the palpable hardware. Data were collated and analyzed
to determine the efficacy and indications for using resorbable plating systems
in different surgical settings as well as to define any precautions or special
considerations.
RESULTS
A total of 55 patients were identified in whom 57 surgical interventions
were performed where resorbable fixation of the craniomaxillofacial skeleton
was used. The group consisted of 27 male and 28 female patients ranging in
age from 5 months to 17 years. Congenital craniofacial anomalies were identified
as the underlying diagnoses in 40 cases while acquired disorders accounted
for the remaining 17 cases (Table 3).
Of the 40 surgical cases with congenital craniofacial anomalies, 32 were primary
interventions and the remaining 8 were revisions. In the primary surgery group
the median age was 11 months (age range, 5-78 months; mean age, 17 months).
In the patients undergoing revision surgery, procedures were performed to
improve deformities in previously operated on sites; the median age for this
group was 10.5 years (age range, 3-14 years; mean age, 9.3 years). The group
of 17 patients with acquired disorders consisted of 11 facial trauma repairs
and 6 skull base tumors; the median age for this group was 13 years (age range,
1.5-17 years; mean age, 1 year).
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Table 3. Underlying Diagnoses in the 57 Patients Who Underwent Craniofacial
Procedures
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In the 40 patients with congenital craniofacial anomalies, surgery consisted
of either a single procedure or multiple procedures performed concurrently,
so that a total of 75 separate procedures were performed overall as outlined
in Table 4. The number of procedures
per surgical intervention was as follows: 12 patients, 1 procedure; 23 patients,
2 procedures; 3 patients, 3 procedures; and 2 patients, 4 procedures. In the
group of patients with acquired disorders a total of 18 craniofacial procedures
were performed and consisted of either open reduction internal fixation of
facial fractures or skull base approaches to tumors of the cranial base (Table 4).
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Table 4. Individual Procedures Performed in the Overall Group of 57
Craniofacial Surgical Interventions
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A total of 408 plates and 1785 screws were used in this series, and
most of these were from the LactoSorb system (390 plates). Smaller 1.5-mm
hardware (393 plates) was used much more commonly than the 2.0-mm system.
An average of 7.2 plates and 31.3 screws per case was used overall. However,
in the cases of congenital craniofacial anomalies and skull base tumor nearly
4 times as much hardware was used than in the trauma patients as given in Table 5.
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Table 5. Number of Plates and Screws Used per Case in the Different
Categories of Surgical Procedure
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Resorbable plates were used as the sole type of bone fixation in the
cases of trauma and skull base tumor (Figure
2). In the patients with congenital craniofacial anomaly, however,
the resorbable plates were usually combined with suture fixation in 22 of
the 40 cases and/or metal plate fixation in 15 of the 40 cases. Suture fixation
was most commonly used for cranial vault remodeling in patients who were between
the ages of 12 and 14 months (Figure 3
and Figure 4). During cranial vault
reshaping and fronto-orbital advancement, bone segments are often recontoured
out of the surgical field or are otherwise very accessible, thereby facilitating
technical ease in the application of resorbable plates. Metal plates were
added to resorbable plates for older patients, particularly in revision procedures,
and at anatomical sites believed to be subjected to the greatest forces of
relapse (Figure 5 and Figure 6). As our confidence with the mechanical stability using
resorbable plates increased over time, the addition of metal plates became
less frequent later in the study. Bone grafting was used at key locations
in 35 of the 40 congenital craniofacial anomaly procedures; but, in none of
the cases of trauma and skull base tumor. Outcome was such that anatomical
union was achieved in 52 (96%) of 54 cases involving the upper and middle
craniofacial skeleton. Malunion occurred in 2 patients undergoing correction
of craniofacial deformities. Analysis of the cases with malunion revealed
that both were revision procedures, bone grafting was not used in either of
them, and they underwent complex procedures with repositioning of 2 or more
bony segments. Deterioration in the postoperative form occurred gradually
over the postoperative course and there were no acute shifts in bony segment
repositioning. The malunion was graded as mild in one case and moderate in
the other.
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Figure 2. A 22-month-old boy. A, Preoperative
magnetic resonance image of a craniopharyngioma with a large suprasellar component.
B, A frontotemporal-orbitozygomatic approach with 2 bone segments was used.
C, Wide open access to the tumor was afforded. D, Following tumor removal
the bone segments were repositioned using only resorbable plate fixation,
and healing proceeded uneventfully.
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Figure 3. A 9-month-old girl. A, View of
nonsyndromic synostosis of the sagittal, metopic, and proximal coronal sutures
leading to significant cranial deformity and elevated intracranial pressure.
Lateral (B) and vertex (C) intraoperative views demonstrate frontal bossing,
bitemporal bossing, and scaphocephaly. Total cranial vault remodeling was
undertaken in addition to fronto-orbital advancement. Lateral (D) and vertex
(E) views showing fixation with resorbable plates and sutures plus the use
of interpositional bone grafts in selected locations. F, The immediate result
demonstrates significant improvement in cranial form that has remained stable
at 2 years of follow-up.
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Figure 4. A, Intraoperative vertex view
of a 3-year-old boy who presented with sagittal synostosis. B, View after
anteroposterior cranial vault remodeling was performed using several resorbable
mesh panels for fixation in addition to sutures. C, Preoperative computed
tomographic scan of an 18-month-old boy with bicoronal synostosis who underwent
fronto-orbital advancement and anterior vault remodeling. D, Resorbable plates
and mesh were used to contour the bandeau and stabilize the advancement as
well as interpositional bone grafts.
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Figure 5. An 18-month-old girl. Preoperative
photograph (A) and 3-dimensional computed tomographic scan (B) of metopic
synostosis and severe trigonocephaly. C, Intraoperative vertex view of the
deformity shown intraoperatively. D, Surgical correction involved anterior
cranial vault remodeling and fronto-orbital advancement using both resorbable
and metal plate fixation. Vertex views before (E) and 32 months (F) after
surgery demonstrating a stable correction with significant improvement in
contour.
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Figure 6. A 14-month-old boy with Crouzon
syndrome. A, Preoperative computed tomographic scan demonstrating syndromic
craniosynostosis with fusion of the proximal coronal sutures bilaterally,
metopic suture, and anterior portion of the sagittal suture. B, Intraoperative
lateral view showing fronto-orbital advancement and anterior cranial vault
remodeling (cvr). A large (25-mm) advancement was performed as seen by the
gap (arrow) at the temporal tenon of the supraorbital bandeau. The bandeau
was recontoured on the side-table, stabilized with resorbable plates bilaterally
(r), then repositioned using a locking Z-plasty technique (z) at the temporal
region and fixated with metal plating at this location. Interpositional bone
grafts (g) were placed to maintain the anterior vault recontouring and advancement
that was stabilized with resorbable plates and sutures. Preoperative views
of the patient (C and D). Postoperative views of the same patient (E and F)
18 months following surgery demonstrate correction of brachyturricephaly and
a significant improvement in overall contour with increased fronto-orbital
projection, increased anteroposterior skull length, and decreased height.
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Delayed union was encountered in 2 of 3 patients with mandibular fractures
treated with open reduction internal fixation using resorbable plates. These
patients were treated with the full understanding that current usage of resorbable
plates in mandible fractures is investigational, and therefore they were to
remain in an extended period of maxillomandibular fixation with gradual resumption
of oral function after 3 to 4 weeks. Unfortunately, noncompliance was an issue
in both youngsters and they removed their interdental fixation within the
first postoperative week. One of these patients experienced plate extrusion
and wound infection that required a second open reduction internal fixation
using metal plate fixation. The other patient experienced mobility at the
fracture site but went on to heal with prolonged maxillomandibular fixation.
Palpable and/or protuberant hardware was the most common adverse effect
after surgery and occurred following 14 procedures (Figure 7A). Note that this group of patients includes patients with
hardware that was palpable and not visible as well as those with visible hardware.
All but 2 of these cases involved fronto-orbital advancement or cranial vault
expansion in patients with congenital anomalies. In all cases the plates gradually
decreased in prominence and became nonpalpable within 6 to 12 months. Direct
evidence of plate resorption was evident in the 2 cases where planned secondary
procedures were undertaken 6 months after the initial craniofacial surgery
during which resorbable hardware was used (Figure 7B). Plate extrusion at the frontozygomatic region occurred
in 2 (3.7%) of the 54 patients with upper and midfacial anomalies. Both patients
were infants who underwent large fronto-orbital advancements and both extrusions
resolved using conservative management without untoward effects. Infection
occurred in 2 patients—1 patient with frontozygomatic extrusion and
1 patient with a mandibular fracture that developed plate extrusion and resulted
in delayed union.
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Figure 7. A, View of a 16-month-old girl
shown 3 months following anterior cranial vault remodeling and fronto-orbital
advancement for syndromic multiple suture synostosis. Extensive fixation with
resorbable plates was used. Extrusion of a screw head over the right lateral
supraorbital bandeau occurred 2 weeks postoperatively and resolved with conservative
management and no adverse effects. Note the multiple visible and palpable
hardware elements scattered elsewhere across the frontal vault. These disappeared
over a 1-year period. B, Intraoperative view in another patient demonstrating
visible plate degradation (arrow) 6 months following placement to stabilize
a recontoured supraorbital bandeau during a preceding surgical procedure.
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Several intraoperative observations were made as our experience evolved
and are noteworthy. There was consensus among the principal investigators
that usage of the resorbable plating systems was both labor intensive and
technique sensitive. Specifically, a traditional drill, tap, and screw process
needs to be performed with each screw placement making sure that the holes
are not overdrilled and that the tap and screw paths coincide with the drill
path. If the holes are not precisely drilled and tapped or the pathways are
not coincident, then difficulties with thread damage or premature binding
are inevitable during screw insertion. The process of plate adaptation can
be time consuming in that it requires a warming device to heat the plates
to a temperature where they become malleable enough to bend. The plates are
then contoured to the desired shape by placing them in situ while still soft;
however, the working time is short and more than one attempt is often necessary
to achieve an acceptable adaptation. In situations with limited access, malleable
metal templates are supplied as intermediaries to facilitate the process.
As experience with the resorbable plates progressed, the amount of time and
duplication of effort decreased so that eventually there was only a minor
difference when compared with metal plating systems. Indeed, the mesh panels
available in all of the resorbable systems proved to be very useful and in
some ways preferable to metal plates. Once rendered malleable by heating above
the glass transition temperature, the mesh panels are readily cut with heavy
scissors into customized shapes and adapted to precisely conform over complex
surfaces. Resorbable mesh also expedited the orientation and fixation of bone
grafts (Figure 8).
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Figure 8. A 7-year-old girl with Pfeiffer
syndrome. Preoperative view (A) and computed tomographic scan (B) demonstrating
hypertelorism, exotropia, exophthalmos, and upper midfacial deficiency. The
patient underwent a 2-stage anterior vault remodeling, fronto-orbital advancement,
and 4-wall orbital repositioning for hypertelorism repair. C, Intraoperative
view demonstrating use of resorbable mesh to stabilize bone grafts placed
into gaps along the lateral orbital wall following orbital repositioning.
D, Postoperative view of the same patient 2 years after surgery illustrating
stable correction of hypertelorism and exophthalmos.
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COMMENT
Our data support the use of resorbable plate fixation in pediatric craniomaxillofacial
surgery of the upper and middle facial skeleton. Bony healing, rates of anatomical
union, and incidence of complications are comparable to results with the current
standard metal plate fixation. Additionally, resorbable plates provide the
added benefit of avoiding the potential problems with metal implants. Our
long-term follow-up demonstrated excellent segmental stability and anatomical
union in 52 (96%) of the 54 patients. Postoperative malunion occurred in 2
patients in which postoperative shift was contributed to by several other
factors including prior surgery, soft tissue scarring, complex multiple part
segmental repositioning, and failure to use interpositional bone grafts.
Other studies have also demonstrated favorable results with resorbable
fixation in the craniofacial skeleton for both adult and pediatric applications
(Table 6). Thranon et al26 reviewed 33 consecutive pediatric patients who underwent
craniofacial surgery for congenital anomalies and tumor removal. LactoSorb
fixation was used in all patients and follow-up ranged from 1 to 12 months.
Early results demonstrated no cases of postoperative bony segment shift or
loss of fixation. Notably, none of the cases involved secondary surgical intervention.
In a larger study, Habal and Pietrzak27 reviewed
their results using LactoSorb fixation in 163 patients (both pediatric and
adult) with a variety of underlying diagnoses (96 congenital anomaly, 34 traumatic
deformity, and 33 tumor removal). Follow-up ranged from 1 month to 3 years
and no major complications with bone healing were noted in the case series.
Patients undergoing reconstruction of congenital deformity or following tumor
resection required 2 to 3 times more hardware elements than those undergoing
traumatic repairs to achieve fixation, a finding noted in our study as well.
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Table 6. Studies Looking at Outcomes Using Resorbable Fixation in the
Upper and Middle Third Craniomaxillofacial Skeleton
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The lack of a significant inflammatory response or infection associated
with resorbable plates in our study and in others is an important finding.26-27,31-32 To
date the long-term studies have used exclusively LactoSorb that contains a
higher concentration of PGA and resorbs faster (approximately 1 year) than
some of the more recently released systems that have a higher PLA content.
Polyglycolic acid degradation results in rapid increases in local glycolic
acid concentration within a few weeks following implantation.20
This can be associated with transient short-term inflammatory responses and,
on occasion, sterile sinus formation or bone osteolysis.33-35
The same phenomenon may explain the transient peri-implant edema noted by
some craniofacial surgeons when using LactoSorb copolymer.27
Fibrous encapsulation and intermittent long-term inflammatory responses have
been reported with monomeric polymers of PLA, which may be due to their protracted
half-life and a low-grade foreign body reaction.20
Systems using copolymers of PLLA and PDLLA have recently become available
for craniofacial application (Table 2)
and it will be interesting to see what rate of foreign body reactions is associated
with these plates over the long-term.
The most common adverse effect with resorbable plates relates to the
higher rate of visible or palpable hardware postoperatively. This results
from the higher profile of resorbable plates necessary to offset the lower
intrinsic strength of polymers and achieve mechanical properties comparable
with titanium hardware. The thickness of polymeric plates averages 2 to 3
times the thickness of titanium hardware with comparable flexural strengths.
The problem is further aggravated during large advancement and cranial expansion
procedures that stretch the overlying soft tissue envelope and in extreme
cases can contribute to plate extrusion. Other investigators26-27
have reported similar findings with hardware palpability and visibility, but
because the problem resolves as the polymers resorb, this is not considered
a true complication of bioresorbable fixation.
Some authors36-37 have resisted
using resorbable fixation on the basis of uncertainty in their ability to
provide adequate biomechanical strength of fixation. Existing studies20, 38-39 have shown that the
available resorbable plating systems (1.5- and 2.0-mm screw diameters) provide
flexural and tensile strength comparable to the microplate titanium systems
(1.0- to 1.3-mm-diameter screws). Interestingly, the polymeric plates have
been shown to provide greater resistance to failure than micro and midface
metallic plates when placed across interfragmentary gaps under compressive
loads.38 This application is common to segmental
advancements and cranial vault expansions for congenital anomaly correction.
Other investigators have reported screw pull-out strengths comparable to titanium
screws of equal diameter in the early period following insertion.19 Thus, resorbable plates and screws are considered
to provide adequate rigidity and immobilization for routine osteosynthesis
within the upper and middle facial skeleton. One must consider, however, that
internal fixation in craniofacial surgery encompasses a wide range of applications
where deformational forces can vary from low-stress passive applications to
high-stress load-bearing areas. Factors that influence the amount of biomechanical
strength necessary to achieve adequate stability include the forces of masticatory
musculature, the degree of comminution or segmentation, the magnitude of segmental
advancement or cranial vault expansion, and the amount of elastic recoil from
the overlying soft tissue envelope. Therefore, it is prudent to consider each
situation individually when determining the type, location, and amount of
fixation necessary. For example, when dealing with zygomatic fractures, it
would seem reasonable to assume that resorbable fixation at 2 or 3 points
would be sufficient in an isolated, noncomminuted, minimally displaced, malar
body fracture. Alternatively, a severely comminuted fracture involving the
zygomatic arch and body, coexisting adjacent midfacial fractures, and disruption
of multiple reference points presents an entirely different scenario. In this
setting there is very little intrinsic structural strength remaining within
the bony architecture, and the deformational forces acting on the fixation
devices will be substantially greater than in the simple zygomatic fracture.
Therefore, the internal fixation applied during reconstruction must provide
a much more rigid and stable framework. Use of existing resorbable fixation
technology in such a case may not be advisable.
Mandiblular fractures present another situation in which available resorbable
plates do not provide the necessary stability to resist masticatory forces.
Our limited findings in which both patients resuming oral function within
days of repair went on to delayed union would seem to support this belief.
We are awaiting development of resorbable plates with greater flexural, torsional,
and compressive strength suitable for open reduction internal fixation of
lower jaw fractures.
In summary, bioresorbable fixation systems represent a major advance
in craniomaxillofacial surgery and have significant benefits in pediatric
applications. The major advantages over existing metal plate fixation include
avoidance of potential risks associated with intracranial migration, dural
irritation, and growth restriction. Indications for available resorbable technology
include a wide variety of procedures such as major reconstruction for congenital
deformities, trauma, and skull base tumors involving non–load-bearing
regions of the upper and middle third craniofacial skeleton. Cases should
be carefully selected, and points of fixation carrying a high risk for postoperative
shift and relapse should be reinforced with interpositional bone grafts and
perhaps fixated using more rigid metallic systems. Resorbable plates have
not been approved for nor are they indicated for repair of lower jaw fractures
with early return to oral function. Resorbable plate fixation of tooth-bearing
bony segments can be problematic secondary to the increased risk of injury
to tooth roots and dental buds when using the larger resorbable plates. This
disadvantage may preclude their use in patients with mixed dentitions. The
surgeon should be aware that resorbable plates are technically more challenging
to work with, particularly early in the learning curve, and this needs to
be weighed against their potential benefits. In terms of cost, the pricing
of resorbable plates and screws is such that they are comparable to metallic
fixation in most situations. The use of large mesh panels helps to contain
costs with resorbable systems because several smaller customized pieces can
be cost-effectively fashioned from a single large panel. The argument for
resorbable plate fixation in adult craniofacial surgery is less compelling,
primarily because the metal plate fixation it would be considered in lieu
of, is easier to work with and presents a much smaller potential downside.
Research is moving forward quickly in polymer chemistry, and future developments
may well lead to the introduction of degradable systems that are easy to use,
carry all the biomechanical advantages of metallic plates, are devoid of any
adverse tissue reactions, and resolve soon after bone healing is complete.
Until then, their use needs to be thoughtfully considered on an individual
basis.
AUTHOR INFORMATION
Accepted for publication December 14, 2000.
Presented at the fall meeting of the American Academy of Facial Plastic
and Reconstructive Surgery, Washington, DC, September 21, 2000.
Corresponding author and reprints: Mario J. Imola, MD, DDS, FRCSC,
Center for Craniofacial–Skull Base Surgery, 1601 E 19th Ave, Suite 3100,
Denver, CO 80218 (e-mail: mjimola{at}qwest.net).
From the Center for Craniofacial–Skull Base Surgery, Denver,
Colo (Drs Imola and Chowdhury); Department of Otolaryngology–Head and
Neck Surgery, University of Minnesota, Minneapolis (Drs Imola, Hamlar, and
Shao); and Department of Otolaryngology and Pediatric Medicine, State University
of New York, Syracuse (Dr Tatum). The authors have no commercial, proprietary,
or financial interest in the products or companies described in this article.
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