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Treatment of pediatric facial fractures: The case for metallic fixation
CLINICAL CONTROVERSIES IN ORAL AND MAXILLOFACIAL SURGERY: PART ONE J Oral Maxillofac Surg 63:382-384, 2005
Treatment of Pediatric Facial Fractures: The Case for Metallic Fixation Rudolf R.M. Bos, DMD, PhD* Today, metallic osteosynthesis systems are looked on as the “gold standard.”1 However, these metal systems have some important disadvantages. Metal systems may interfere with radiotherapy, computed tomography, and magnetic resonance imaging. Furthermore, complications associated with metal implants include infection, sensitization, and even mutagenic effects.2 In some cases, plate and screw removal is required.3 Bioresorbable osteosynthesis systems degrade. In the ideal situation, the patient does not have to experience another surgical intervention for the removal of plates and screws. This reduces operation time, additional surgical discomfort and risk, and cost. Finally, the use of bioresorbable osteosynthesis may prevent osteoporosis due to stress protection, because they allow a gradual transfer of functional forces to the healing bone.2,3 Bioresorbable osteosynthesis systems have not replaced metallic systems and are currently used only in limited numbers.2,4 This is probably because there is insufficient clinical scientific evidence about the short-term (mechanical properties) and long-term (bioresorbability) characteristics of the various resorbable osteosynthesis systems.5 Available information comes from the manufacturers’ brochures, which do not provide adequate advice concerning the selection and application of bioresorbable osteosynthesis systems. It is therefore difficult for the surgeon to make a well-considered choice regarding the selection and application of bioresorbable osteosynthesis systems. Selection of bioresorbable osteosynthesis systems starts with the formulation of what, in general, would be the qualities of an ideal bioresorbable fixation system. The ideal implant is made of a material that 1)
can be fabricated and designed with appropriate initial strength to meet the biomechanical demands, 2) degrades in a predictable fashion while allowing for safe progressive loading during each stage of bone healing, 3) causes no tissue responses necessitating device removal, 4) disappears completely without toxic or mutagenic reactions, and 5) is easy to use.6 I do not believe that any bioresorbable osteosynthesis system currently available meets these criteria. Three items should be considered in choosing metallic osteosynthesis versus biodegradable osteosynthesis: Mechanical properties Biocompatibility Ease of handling
Mechanical Properties The mechanical properties of bioresorbable osteosynthesis are still far below those of their metal counterparts.7,8 To make the implants strong enough to enable undisturbed bone healing, biodegradable plates and screws have to be far coarser to compensate for the limited mechanical properties of the polymeric material itself. Coarse dimensions are unfavorable in case of pediatric fracture fixation. Even metallic miniplates are often too coarse in relation to children’s anatomy, so preferably microplates are used. An absolute disadvantage of bioresorbable screws in particular is that they have limited resistance against torsional forces.9 That means that one has to be careful when inserting the screws, even after careful tapping. It also means that one can hardly reach any compression. On many occasions, for stability of fracture ends and osteosynthesis, the plate should be pressed firmly against the underlying bone surface to prevent movement between the bone segments and fixation system, ensuring an adequate fixation and stabilization of the bone segments. Metallic screws, even tiny microscrews, allow compression and thus more stability than resorbable screws.
*Professor, Department of Oral and Maxillofacial Surgery, Groningen University Hospital, Groningen, the Netherlands. Address correspondence and reprint requests to Dr Bos: Department of Oral and Maxillofacial Surgery, Groningen University Hospital, PO Box 30.001, 9700 RB Groningen, the Netherlands; e-mail: [email protected] © 2005 American Association of Oral and Maxillofacial Surgeons
0278-2391/05/6303-0014$30.00/0 doi:10.1016/j.joms.2004.11.010
382
383
RUDOLF R.M. BOS
Biocompatibility Several biodegradable materials have been tried over the past 40 years. They are all from the group of poly ␣-hydroxy acids. Polyglycolic acid (PGA) and pure poly-L-lactic acid (PLLA) cause adverse reactions during degradation, so they are no longer used.10 At the present, only co-polymers of different compositions are used to manufacture plates, screws, and tacks. These co-polymers should enhance the resorbability of these materials and so prevent adverse reactions like inflammatory or foreign body reactions. Discussions on the necessity of plate removal have become more vigorous with the introduction of titanium. Titanium is said to be fully biocompatible compared with many traditional materials such as vitallium and stainless steel. Kim et al11 showed that titanium might not be completely bioinert. They found extremely small amounts of titanium in the lymphatic system after implantation of dental implants as well as titanium plates and screws. It has been suggested that these small amounts of titanium originate from loosening of superficial particles during insertion. Furthermore, it is not clear whether these small amounts are harmful. At the present, titanium is thought to be nonallergenic, completely inert, and biocompatible. That means that a second intervention to remove titanium plates and screws should not be necessary.12 In children, plate removal is advocated not so much to prevent growth disturbances as it is for their translation by drift phenomena. In the growing patient, there is a chance that the growth can lead to inclusion of plates and screws and even to intracranial displacement. Despite the fact that this really occurs, one may wonder whether this matters as long as the material is biocompatible, as titanium is thought to be. At the same time we have to admit that, in view of the long life expectancy of young patients, knowledge fails us about the very long-term effects of nonfunctional plates and screws after bone healing. This seems to be a strong argument in favor of those who prefer resorbables for fracture fixation in children. However, a recent study documented the presence of very persistent nanoparticles and microparticles in the degradation pathway of a PLA-PGA co-polymer in use as a so-called bioresorbable implant material.2 This study indicates that poly ␣-hydroxy acid– based implants may not completely degrade within 15 to 20 years and may persist even longer. At the present, it seems prudent to assume that crystalline debris from poly ␣-hydroxy acid implants will remain in the recipients with the potential for the development of unforeseen complications. Complete resorption, ideally, has to be investigated microscopically, electron microscopically, and even on a molecular level before conclu-
sions can be drawn. Presently, proof of complete resorption fails for any so-called resorbable implant. Investigators and manufacturers should not be blamed for this, as giving proof of full resorption is not currently possible. It is more the fact that they claim that they have proved full resorption that annoys me. Although proof of full biocompatibility of titanium implants as well as so-called bioresorbable implants fails, a strong argument for titanium is that at least about 100% of the originally implanted material can be removed, which is not possible for degraded, but not completely resorbed remnants of so-called resorbable implants.
Ease of Handling Handling of bioresorbable plates can be difficult. Metallic plates can be easily shaped with pliers. Bending of bioresorbable plates, almost without exception, can be performed only after careful heating. Overheating can easily damage the mechanical properties. The patented self-reinforcement technique13 aims for better mechanical properties and allows bending at room temperature. The manufacturers of this system claim that bending at room temperature does not damage the mechanical properties of the plates, although one sees crazing or even cracks arising during bending. The disadvantage of self-reinforcement (which in fact is orientation of polymer chains by stretching the heated material) is that the material relaxes to its original unstretched shape when heated. Bioresorbable screws can be inserted only after predrilling and pretapping. Plate bending and screw insertion are very time consuming and far more complicated compared with titanium. And, as already mentioned, bioresorbable screws easily break during insertion and allow only limited compression. However, in case of screw breakage, a new hole can easily be drilled and tapped at the same site. Metallic osteosynthesis systems can be sterilized and resterilized in the autoclave. Bioresorbable osteosynthesis systems have to be sterilized carefully by irradiation or with ethylene oxide through special procedures; otherwise, the already limited mechanical properties will be reduced even further. Resterilization is not possible. Bioresorbable implants therefore need careful packaging and require a lot of storage room, preferably at low temperature and dry atmosphere. Shelf life is also limited. I still choose small titanium plates and screws for fixation of pediatric fractures. They are easy to handle and easy to sterilize. They have far better mechanical properties and small dimensions at the same time. Although it is not always easy, they can be at least removed completely if necessary, even after many years.
384
METALLIC FIXATION OF PEDIATRIC FACIAL FRACTURES
The question of real biocompatibility remains. The answer to that question is not known for titanium as well as bioresorbable implants.
7. Bozic KJ, Perez LE, Wilson DR, et al: Mechanical testing of bioresorbable implants for use in metacarpal fracture fixation. J Hand Surg [Am] 26:755, 2001 8. Gosain AK, Song L, Capel CC, et al: Biomechanical and histologic alteration of facial recipient bone after reconstruction with autogenous bone grafts and alloplastic implants: A 1-year study. Plast Reconstr Surg 101:1561, 1998 9. Shetty V, Caputo AA, Kelso I: Torsion-axial force characteristics of SR-PLLA screws. J Craniomaxillofac Surg 25:19, 1997 10. Bergsma EJ, Rozema FR, Bos RR, et al: Foreign body reactions to resorbable poly(L-lactide) bone plates and screws used for the fixation of unstable zygomatic fractures. J Oral Maxillofac Surg 51:666, 1993 11. Kim YK, Yeo HH, Lim SC: Tissue response to titanium plates: A transmitted electron microscopic study. J Oral Maxillofac Surg 55:322, 1997 12. Meningaud JP, Poupon J, Bertrand JC, et al: Dynamic study about metal release from titanium miniplates in maxillofacial surgery. Int J Oral Maxillofac Surg 30:185, 2001 13. Tormala P, Vasenius J, Vainionpaa S, et al: Ultra-highstrength absorbable self-reinforced polyglycolide (SR-PGA) composite rods for internal fixation of bone fractures: In vitro and in vivo study. J Biomed Mater Res 25:1, 1991
References 1. Kim YK, Kim SG: Treatment of mandible fractures using bioabsorbable plates. Plast Reconstr Surg 110:25, 2002 2. Cordewener FW, Schmitz JP: The future of biodegradable osteosyntheses. Tiss Eng 6:413, 2000 3. Gerlach KL: Resorbable polymers as osteosynthesis material. Mund Kiefer Gesichtschir 4:S91, 2000 4. Suuronen R, Haers PE, Lindqvist C, et al: Update on bioresorbable plates in maxillofacial surgery. Facial Plast Surg 15:61, 1999 5. Eppley BL, Prevel CD: Nonmetallic fixation in traumatic midfacial fractures. J Craniofac Surg 8:103, 1997 6. Pietrzak WS, Sarver DR, Verstynen ML: Bioabsorbable polymer science for the practicing surgeon. J Craniofac Surg 8:87, 1997
Treatment of Pediatric Facial Fractures: The Case for Metallic Fixation Rudolf R.M. Bos, DMD, PhD* Today, metallic osteosynthesis systems are looked on as the “gold standard.”1 However, these metal systems have some important disadvantages. Metal systems may interfere with radiotherapy, computed tomography, and magnetic resonance imaging. Furthermore, complications associated with metal implants include infection, sensitization, and even mutagenic effects.2 In some cases, plate and screw removal is required.3 Bioresorbable osteosynthesis systems degrade. In the ideal situation, the patient does not have to experience another surgical intervention for the removal of plates and screws. This reduces operation time, additional surgical discomfort and risk, and cost. Finally, the use of bioresorbable osteosynthesis may prevent osteoporosis due to stress protection, because they allow a gradual transfer of functional forces to the healing bone.2,3 Bioresorbable osteosynthesis systems have not replaced metallic systems and are currently used only in limited numbers.2,4 This is probably because there is insufficient clinical scientific evidence about the short-term (mechanical properties) and long-term (bioresorbability) characteristics of the various resorbable osteosynthesis systems.5 Available information comes from the manufacturers’ brochures, which do not provide adequate advice concerning the selection and application of bioresorbable osteosynthesis systems. It is therefore difficult for the surgeon to make a well-considered choice regarding the selection and application of bioresorbable osteosynthesis systems. Selection of bioresorbable osteosynthesis systems starts with the formulation of what, in general, would be the qualities of an ideal bioresorbable fixation system. The ideal implant is made of a material that 1)
can be fabricated and designed with appropriate initial strength to meet the biomechanical demands, 2) degrades in a predictable fashion while allowing for safe progressive loading during each stage of bone healing, 3) causes no tissue responses necessitating device removal, 4) disappears completely without toxic or mutagenic reactions, and 5) is easy to use.6 I do not believe that any bioresorbable osteosynthesis system currently available meets these criteria. Three items should be considered in choosing metallic osteosynthesis versus biodegradable osteosynthesis: Mechanical properties Biocompatibility Ease of handling
Mechanical Properties The mechanical properties of bioresorbable osteosynthesis are still far below those of their metal counterparts.7,8 To make the implants strong enough to enable undisturbed bone healing, biodegradable plates and screws have to be far coarser to compensate for the limited mechanical properties of the polymeric material itself. Coarse dimensions are unfavorable in case of pediatric fracture fixation. Even metallic miniplates are often too coarse in relation to children’s anatomy, so preferably microplates are used. An absolute disadvantage of bioresorbable screws in particular is that they have limited resistance against torsional forces.9 That means that one has to be careful when inserting the screws, even after careful tapping. It also means that one can hardly reach any compression. On many occasions, for stability of fracture ends and osteosynthesis, the plate should be pressed firmly against the underlying bone surface to prevent movement between the bone segments and fixation system, ensuring an adequate fixation and stabilization of the bone segments. Metallic screws, even tiny microscrews, allow compression and thus more stability than resorbable screws.
*Professor, Department of Oral and Maxillofacial Surgery, Groningen University Hospital, Groningen, the Netherlands. Address correspondence and reprint requests to Dr Bos: Department of Oral and Maxillofacial Surgery, Groningen University Hospital, PO Box 30.001, 9700 RB Groningen, the Netherlands; e-mail: [email protected] © 2005 American Association of Oral and Maxillofacial Surgeons
0278-2391/05/6303-0014$30.00/0 doi:10.1016/j.joms.2004.11.010
382
383
RUDOLF R.M. BOS
Biocompatibility Several biodegradable materials have been tried over the past 40 years. They are all from the group of poly ␣-hydroxy acids. Polyglycolic acid (PGA) and pure poly-L-lactic acid (PLLA) cause adverse reactions during degradation, so they are no longer used.10 At the present, only co-polymers of different compositions are used to manufacture plates, screws, and tacks. These co-polymers should enhance the resorbability of these materials and so prevent adverse reactions like inflammatory or foreign body reactions. Discussions on the necessity of plate removal have become more vigorous with the introduction of titanium. Titanium is said to be fully biocompatible compared with many traditional materials such as vitallium and stainless steel. Kim et al11 showed that titanium might not be completely bioinert. They found extremely small amounts of titanium in the lymphatic system after implantation of dental implants as well as titanium plates and screws. It has been suggested that these small amounts of titanium originate from loosening of superficial particles during insertion. Furthermore, it is not clear whether these small amounts are harmful. At the present, titanium is thought to be nonallergenic, completely inert, and biocompatible. That means that a second intervention to remove titanium plates and screws should not be necessary.12 In children, plate removal is advocated not so much to prevent growth disturbances as it is for their translation by drift phenomena. In the growing patient, there is a chance that the growth can lead to inclusion of plates and screws and even to intracranial displacement. Despite the fact that this really occurs, one may wonder whether this matters as long as the material is biocompatible, as titanium is thought to be. At the same time we have to admit that, in view of the long life expectancy of young patients, knowledge fails us about the very long-term effects of nonfunctional plates and screws after bone healing. This seems to be a strong argument in favor of those who prefer resorbables for fracture fixation in children. However, a recent study documented the presence of very persistent nanoparticles and microparticles in the degradation pathway of a PLA-PGA co-polymer in use as a so-called bioresorbable implant material.2 This study indicates that poly ␣-hydroxy acid– based implants may not completely degrade within 15 to 20 years and may persist even longer. At the present, it seems prudent to assume that crystalline debris from poly ␣-hydroxy acid implants will remain in the recipients with the potential for the development of unforeseen complications. Complete resorption, ideally, has to be investigated microscopically, electron microscopically, and even on a molecular level before conclu-
sions can be drawn. Presently, proof of complete resorption fails for any so-called resorbable implant. Investigators and manufacturers should not be blamed for this, as giving proof of full resorption is not currently possible. It is more the fact that they claim that they have proved full resorption that annoys me. Although proof of full biocompatibility of titanium implants as well as so-called bioresorbable implants fails, a strong argument for titanium is that at least about 100% of the originally implanted material can be removed, which is not possible for degraded, but not completely resorbed remnants of so-called resorbable implants.
Ease of Handling Handling of bioresorbable plates can be difficult. Metallic plates can be easily shaped with pliers. Bending of bioresorbable plates, almost without exception, can be performed only after careful heating. Overheating can easily damage the mechanical properties. The patented self-reinforcement technique13 aims for better mechanical properties and allows bending at room temperature. The manufacturers of this system claim that bending at room temperature does not damage the mechanical properties of the plates, although one sees crazing or even cracks arising during bending. The disadvantage of self-reinforcement (which in fact is orientation of polymer chains by stretching the heated material) is that the material relaxes to its original unstretched shape when heated. Bioresorbable screws can be inserted only after predrilling and pretapping. Plate bending and screw insertion are very time consuming and far more complicated compared with titanium. And, as already mentioned, bioresorbable screws easily break during insertion and allow only limited compression. However, in case of screw breakage, a new hole can easily be drilled and tapped at the same site. Metallic osteosynthesis systems can be sterilized and resterilized in the autoclave. Bioresorbable osteosynthesis systems have to be sterilized carefully by irradiation or with ethylene oxide through special procedures; otherwise, the already limited mechanical properties will be reduced even further. Resterilization is not possible. Bioresorbable implants therefore need careful packaging and require a lot of storage room, preferably at low temperature and dry atmosphere. Shelf life is also limited. I still choose small titanium plates and screws for fixation of pediatric fractures. They are easy to handle and easy to sterilize. They have far better mechanical properties and small dimensions at the same time. Although it is not always easy, they can be at least removed completely if necessary, even after many years.
384
METALLIC FIXATION OF PEDIATRIC FACIAL FRACTURES
The question of real biocompatibility remains. The answer to that question is not known for titanium as well as bioresorbable implants.
7. Bozic KJ, Perez LE, Wilson DR, et al: Mechanical testing of bioresorbable implants for use in metacarpal fracture fixation. J Hand Surg [Am] 26:755, 2001 8. Gosain AK, Song L, Capel CC, et al: Biomechanical and histologic alteration of facial recipient bone after reconstruction with autogenous bone grafts and alloplastic implants: A 1-year study. Plast Reconstr Surg 101:1561, 1998 9. Shetty V, Caputo AA, Kelso I: Torsion-axial force characteristics of SR-PLLA screws. J Craniomaxillofac Surg 25:19, 1997 10. Bergsma EJ, Rozema FR, Bos RR, et al: Foreign body reactions to resorbable poly(L-lactide) bone plates and screws used for the fixation of unstable zygomatic fractures. J Oral Maxillofac Surg 51:666, 1993 11. Kim YK, Yeo HH, Lim SC: Tissue response to titanium plates: A transmitted electron microscopic study. J Oral Maxillofac Surg 55:322, 1997 12. Meningaud JP, Poupon J, Bertrand JC, et al: Dynamic study about metal release from titanium miniplates in maxillofacial surgery. Int J Oral Maxillofac Surg 30:185, 2001 13. Tormala P, Vasenius J, Vainionpaa S, et al: Ultra-highstrength absorbable self-reinforced polyglycolide (SR-PGA) composite rods for internal fixation of bone fractures: In vitro and in vivo study. J Biomed Mater Res 25:1, 1991
References 1. Kim YK, Kim SG: Treatment of mandible fractures using bioabsorbable plates. Plast Reconstr Surg 110:25, 2002 2. Cordewener FW, Schmitz JP: The future of biodegradable osteosyntheses. Tiss Eng 6:413, 2000 3. Gerlach KL: Resorbable polymers as osteosynthesis material. Mund Kiefer Gesichtschir 4:S91, 2000 4. Suuronen R, Haers PE, Lindqvist C, et al: Update on bioresorbable plates in maxillofacial surgery. Facial Plast Surg 15:61, 1999 5. Eppley BL, Prevel CD: Nonmetallic fixation in traumatic midfacial fractures. J Craniofac Surg 8:103, 1997 6. Pietrzak WS, Sarver DR, Verstynen ML: Bioabsorbable polymer science for the practicing surgeon. J Craniofac Surg 8:87, 1997