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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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.

Table 1. 
Physical Properties of the Common Monomeric Polymers Currently
Used in Fabricating Bioresorbable Plates and Screws
Physical Properties of the Common Monomeric Polymers Currently Used in Fabricating Bioresorbable Plates and Screws
Table 2. 
Commercially Available Craniomaxillofacial Resorbable Plating
Systems and Their Properties
Commercially Available Craniomaxillofacial Resorbable Plating Systems and Their Properties
Table 3. 
Underlying Diagnoses in the 57 Patients Who Underwent Craniofacial
Procedures
Underlying Diagnoses in the 57 Patients Who Underwent Craniofacial Procedures
Table 4. 
Individual Procedures Performed in the Overall Group of 57
Craniofacial Surgical Interventions
Individual Procedures Performed in the Overall Group of 57 Craniofacial Surgical Interventions
Table 5. 
Number of Plates and Screws Used per Case in the Different
Categories of Surgical Procedure
Number of Plates and Screws Used per Case in the Different Categories of Surgical Procedure
Table 6. 
Studies Looking at Outcomes Using Resorbable Fixation in the
Upper and Middle Third Craniomaxillofacial Skeleton
Studies Looking at Outcomes Using Resorbable Fixation in the Upper and Middle Third Craniomaxillofacial Skeleton
1.
Goldberg  DSBartlett  SPYu  JCHunter  JVWitaker  LA Critical review of microfixation in pediatric craniofacial surgery. J Craniofac Surg. 1995;6301- 307Article
2.
Mofid  MMReid  CTPardo  CA  et al.  Biocompatability of fixation materials in the brain. Plast Reconstr Surg. 1997;10014- 20Article
3.
Yu  JCBartlett  SPGoldberg  DS An experimental study of the effects of craniofacial growth on the long-term positional stability of microfixation. J Craniofac Surg. 1996;764- 68Article
4.
Eppley  BLPlatis  JMSadove  AM Experimental effects of bone plating in infancy on craniomaxillofacial skeletal growth. Cleft Palate Craniofac J. 1993;30164- 169Article
5.
Fearon  JAMunro  IRBruce  DA Observations on the use of rigid fixation for craniofacial deformities in infants and young children. Plast Reconstr Surg. 1995;95634- 637Article
6.
Yaremchuk  MJ Experimental studies addressing rigid fixation in craniofacial surgery. Clin Plast Surg. 1994;21517- 524
7.
Paavolainen  PKaraharju  ESlatis  PAhonen  JHolstrom  T Effect of rigid plate fixation on structure and mineral content of cortical bone. Clin Orthop. 1978;136287- 293
8.
Izuka  TLindquist  C Rigid internal fixation of mandibular fractures: an analysis of 270 fractures treated using the AO/ASIF method. Int J Oral Maxillofac Surg. 1992;2165- 69Article
9.
Bos  RRBoering  GRozema  FRLeenslag  JW Resorbable poly(L-lactide) plates and screws for the fixation of zygomatic fractures. J Oral Maxillofac Surg. 1987;45751- 753Article
10.
Persing  JA Discussion: biocompatablility of fixation materials in the brain. Plast Reconstr Surg. 1997;10021- 22Article
11.
Cutright  DEHunsuck  EE The repair of orbital fractures of the orbital floor using biodegradable polylactic acid. Oral Surg Oral Med Oral Pathol. 1972;3328- 34Article
12.
Getter  LCutright  DEBhaskar  SN Augsburg JK A biodegradable intraosseous appliance in the treatment of mandibular fractures. J Oral Surg. 1972;30344- 348
13.
Bos  RRRozema  FRBoering  G  et al.  Bone plates and screws of bioabsorbable poly (L-lactide): an animal pilot study. Br J Oral Maxillofac Surg. 1989;27467- 476Article
14.
Gerlach  KL Treatment of zygomatic fractures with biodegradable poly(L-lactide) plates and screws: clinical implant materials. Heimke  GSoltesz  ULee  ACJeds.Advances in Biomaterials. Amsterdam, the Netherlands Elsevier Science Inc1990;573- 578
15.
Iizuka  TMikkonen  PPaukku  PLindquist  C Reconstruction of orbital floor with polydioxanone plate. Int J Oral Maxillofac Surg. 1991;2083- 87Article
16.
Eppley  BLSadove  AM Effects of resorbable fixation on craniofacial skeletal growth: a pilot experimental study. J Craniofac Surg. 1992;3190- 196Article
17.
Thaller  SRHuang  VTesluk  H Use of biodegradable plates and screws in a rabbit model. J Craniofac Surg. 1992;2168- 173Article
18.
Suuronen  R Biodegradable fracture-fixation devices in maxillofacial surgery. Int J Oral Maxillofac Surg. 1993;2250- 57Article
19.
Kellman  RMHuckins  SCKing  JHumphrey  DMarentette  LOsborn  DC Bioresorbable screws for facial bone reconstruction: a pilot study in rabbits. Laryngoscope. 1994;104556- 561Article
20.
Pietrzak  WSSarver  DRVerstynen  ML Bioabsorbable polymer science for the practicing surgeon. J Craniofac Surg. 1997;887- 91Article
21.
Pietrzak  WSVerstynen  MLSarver  DR Bioabsorbable fixation devices: status for the craniomaxillofacial surgeon. J Craniofac Surg. 1997;892- 96Article
22.
Eppley  BLReilly  M Degradation characteristics of PLLA-PGA bone fixation devices. J Craniofac Surg. 1997;8116- 120Article
23.
Eppley  BLSadove  MAHavlik  RJ Reosorbable plate fixation in pediatric craniofacial surgery. Plast Reconstr Surg. 1997;1001- 7Article
24.
Habal  MB Absorbable, invisible, and flexible plating system for the craniofacial skeleton. J Craniofac Surg. 1997;8121- 126Article
25.
Pensler  JM Role of resorbable plates and screws in craniofacial surgery. J Craniofac Surg. 1997;8129- 134Article
26.
Tharanon  WSinn  DPHobar  CPSklar  FHSalomon  J Surgical outcomes using bioabsorbable plating systems in pediatric craniofacial surgery. J Craniofac Surg. 1998;9441- 444Article
27.
Habal  MBPietrzak  WS Key points in the fixation of the craniofacial skeleton with absorbable biomaterial. J Craniofac Surg. 1999;10491- 499Article
28.
Eppley  BLSadove  AM A comparison of resorbable and metallic fixation in healing of calvarial bone grafts. Plast Reconstr Surg. 1995;96316- 322Article
29.
Eppley  BLPrevel  CDSadove  AMSarver  DR Resorbable bone fixation: its potential role in craniomaxillofacial trauma. J Craniomaxillofac Trauma. 1996;256- 62
30.
Eppley  BLPrevel  CD Nonmetallic fixation in traumatic midfacial fractures. J Craniofac Surg. 1997;8103- 109Article
31.
Edwards  RCKiely  KD Resorbable fixation of Le Fort I osteotomies. J Craniofac Surg. 1998;9210- 214Article
32.
Westermark  A LactoSorb resorbable osteosynthesis after sagittal split osteotomy of the mandible: a 2-year follow-up. J Craniofac Surg. 1999;10519- 522Article
33.
Partio  EKBostman  OHirvensalo  E  et al.  The indication for the fixation of fractures with totally absorbable SR-PGA screws. Acta Orthop Scand. 1990;61suppl43- 47Article
34.
Bostman  OM Osteolytic changes accompanying degradation of absorbable fracture fixation implants. J Bone Joint Surg Br. 1991;73679- 682
35.
Bergsma  JEde Bruijn  WCRozema  FRBos  RRBoering  G Late degradation tissue response to poly(L-lactide) bone plates and screws. Biomaterials. 1995;1625- 31Article
36.
Manson  PDiscussion.J Craniofac Surg. 1999;10400- 403Article
37.
Gosain  AKSong  LCorrao  MAPintar  FA Biomechanical evaluation of titanium biodegradable plate and screw, and cyanoacrylate glue fixation systems in craniofacial surgery. Plast Reconstr Surg. 1998;101582- 591Article
38.
Krsarai  LHearn  TGur  EForrest  CRManson  P A biomechanical analysis of the orbital zygomatic complex in human cadavers: examination of load sharing and failure patterns after fixation with titanium and bioresorbable systems. J Craniofac Surg. 1999;10273- 243Article
39.
Wittenberg  JMWittenberg  RHHipp  JA Biomechanical properties of resorbable poly-L-lactide plates and screws: a comparison with traditional systems. J Oral Maxillofac Surg. 1991;49512- 516Article
Citations 0
Original Article
April 2001

Resorbable Plate Fixation in Pediatric Craniofacial SurgeryLong-term Outcome

Author Affiliations

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.

 

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.

Arch Facial Plast Surg. 2001;3(2):79-90. doi:
Abstract

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.

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.

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.

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).

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).

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.

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.

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.

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).

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.

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.

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Article 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@qwest.net).

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