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Figure 1.
Biplanar (top) and monoplanar
(bottom) plate application.

Biplanar (top) and monoplanar (bottom) plate application.

Figure 2.
The test fixture.

The test fixture.

Figure 3.
Measurement of mobility using
a dial gauge.

Measurement of mobility using a dial gauge.

Results With the Single- and Double-Plate Techniques
Results With the Single- and Double-Plate Techniques
1.
Adams  W Internal wiring fixation of facial fractures. Surgery. 1942;12523- 540
2.
Fedok  FGVan Kooten  DWDeJoseph  LM  et al.  Plating techniques and plate orientation in repair of mandibular angle fractures: an in vitro study. Laryngoscope. 1998;108 (pt 1) 1218- 1224Article
3.
Luhr  HG On the stable osteosynthesis in mandibular fractures [in German] [abstract] Dtsch Zahnarztl Z. 1968;23754
4.
Allgower  MEhrsam  RGanz  RMatter  PPerrin  SM Clinical experience with a new compression plate "DCP". Acta Orthop Scand Suppl. 1969;12545- 61
5.
Spiessl  B Early treatment of complicated mandibular fractures by means of rigid internal fixation according to AO principles. Maxillofacial Trauma: An International Perspective. New York, NY Praeger1983;177- 186
6.
Benoit  PMichelet  FBenoit  JPFestal  FDessus  BMoll  A Treatment of mandibular fractures without blocking by means of a juxta-alveolar screwed plate inserted through the mouth: 60 cases [in French]. Rev Stomatol Chir Maxillofac. 1971;72313- 315
7.
Michelet  ADeymes  J Osteosynthesis with screwed plates in maxillofacial surgery: experience with 500 satellite plates. Int Surg. 1973;58249- 253
8.
Champy  MLodde  JPSchmitt  RJaeger  JHMuster  D Mandibular osteosynthesis by miniature screwed plates via a buccal approach. J Maxillofac Surg. 1978;614- 21Article
9.
Schmoker  RSpiessl  B Excentric-dynamic compression plate: experimental study as contribution to a functionally stable osteosynthesis in mandibular fractures [in German]. SSO Schweiz Monatsschr Zahnheilkd. 1973;831496- 1509
10.
Schmoker  RSpiessl  BTschopp  HMPrein  JJaques  WA Functionally stable osteosynthesis of the mandible by means of an eccentric-dynamic compression plate: results of a follow-up of 25 cases [in German]. SSO Schweiz Monatsschr Zahnheilkd. 1976;86167- 185
11.
Hoffman  WBarton  RPrice  MMathes  S Rigid internal fixation vs traditional techniques for the treatment of mandible fractures. J Trauma. 1990;301032- 1035Article
12.
Terris  DJLalakea  MLTuffo  KMShinn  JB Mandible fracture repair: specific indications for newer techniques. Otolaryngol Head Neck Surg. 1994;111751- 757Article
13.
Leach  JTruelson  J Traditional methods vs rigid internal fixation of mandible fractures. Arch Otolaryngol Head Neck Surg. 1995;121750- 753Article
14.
Valentino  JLevy  FEMarentette  LJ Intraoral monocortical miniplating of mandible fractures. Arch Otolaryngol Head Neck Surg. 1994;120605- 612Article
15.
Marentette  L Miniplate osteosynthesis of mandible fractures. Operative Tech Otolaryngol Head Neck Surg. June1995;6
16.
Ardary  W Prospective clinical evaluation of the use of compression plates and screws in the management of mandible fractures. J Oral Maxillofac Surg. 1989;471150- 1153Article
17.
Haug  RHBarber  JEReifeis  R A comparison of mandibular angle fracture plating techniques. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1996;82257- 263Article
Citations 0
Original Article
January 2002

Biplanar Plating of Mandibular FracturesA New Concept With In Vitro Testing and Comparison With the Traditional Plate-and-Screw Technique

Author Affiliations

From the Department of Otolaryngology–Head and Neck Surgery, Jefferson Medical College, Philadelphia, Pa.

 

From the Department of Otolaryngology–Head and Neck Surgery, Jefferson Medical College, Philadelphia, Pa.

Arch Facial Plast Surg. 2002;4(1):47-51. doi:
Abstract

Objectives  To introduce the concept of biplanar plating of mandibular fractures and to present an in vitro comparison of this method with traditional use of a single mandibular plate.

Design  A device for the delivery of repetitive simulated masticatory stress to mandibular models was developed. Using the device, we compared biplanar with single-plate fixation of vertical mandibular body fractures by determining cycles to failure.

Setting  Tertiary care academic medical center.

Intervention  A simulated masticatory force was delivered vertically to the anterior end of polymer hemimandibles as used for in vitro teaching of plating methods. Mobility at the fracture site was tested at intervals corresponding to 6000 chewing cycles each.

Results  Of 5 specimens plated with a mandibular fixation plate, 4 developed greater than 0.010 cm of vertical mobility at the fracture site after 12 000 cycles. Only 1 of the 5 specimens fixed with biplanar plating developed this degree of mobility.

Conclusions  Single-plate fixation of mandibular fractures is greatly enhanced by a miniplate spanning the fracture along the inferior border. We used this technique on 15 patients with unfavorable fractures and found it simple, secure, and reliable. We had no complications. An inferior marginal plate serves the same function as a tension band, and can be placed on mandibles through the same incision as the main fixation plate without additional dissection. We prefer this to a traditional tension band when the percutaneous route of access to a mandibular fracture site is used.

IN THE 60 YEARS since Adams1 described open reduction and internal fixation of facial fractures with interosseous stainless steel wiring, mandibular fracture repair has evolved through a series of materials and methods. We have progressed far beyond simple wire loops placed through burr holes in bone, and have plating systems of great sophistication (and, in some cases, complexity). There are systems with screws having threaded heads and shanks, systems with hollow screws for osseointegration, and even systems with absorbable plates and screws. But the gold standard for primary plate fixation of mandibular fractures remains the single plate on the buccal cortex.

There are few studies in the literature on in vitro testing of mandibular fracture fixation. Those studies that are found use synthetic or cadaver mandibles in a common cantilever beam device. A recent article by Fedok et al2 introduced the idea of a tension band placed in a different plane from the fixation plate (but still on the buccal cortex), which Fedok et al termed biplanar plating. Because we had been using this term for several years in reference to the placement of a 1.7-mm miniplate along the inferior mandibular border in addition to a standard 2.4-mm plate on the buccal cortex, we were stimulated by the in vitro study by Fedok et al to test our technique against monocortical plating with a neutral (ie, noncompression) 2.4-mm mandibular reconstruction plate. We wanted to establish whether and to what degree the addition of a small inferior cortex plate increases stability of fixation of mandibular body fractures.

MATERIALS AND METHODS

As with other in vitro studies, polystyrene mandibles, with a rigid outer cortex and a trabecular medullary space, were used to simulate physiologic properties. These uniform sample mandibles are preferred because they eliminate the variability associated with cadaveric mandibles, and do not undergo changes in physical properties with drying. A band saw with a fine blade was used to create linear fractures in the body of each test mandible just distal to the second molar, in a standardized fashion and with neither favorable nor unfavorable angulation. Following manual reduction of the fractures, 5 of the hemimandibles were stabilized using a standard, neutral, 2.4-mm mandibular plate on the buccal cortex, with 2 screws on either side of the fracture. A 1.7-mm miniplate was placed along the inferior border of 5 specimens in a plane perpendicular to the main fixation plate, also with 2 screws on either side of the fracture. The other 5 specimens were stabilized with neutral mandibular plates identical to those on the buccal cortices of the first group, but without the addition of a miniplate on the inferior cortical surface (Figure 1).

The test mandibles were secured by a 0.794-cm stainless steel rod with 0.008 cm of clearance in precision-drilled holes through the condyles. The fracture lines and plates were coated with a thin application of silicone caulking to simulate the viscoelastic properties and vibration-dampening effect of the native soft tissue adherent to in vivo fractures. Testing was conducted in a jig that stabilized the proximal mandibular fragment on a firm elastic polymer to simulate the muscular sling of the medial pterygoid and masseter. Vertical forces were then applied to the central incisors by rotating a motor-driven camshaft against the specimens to deliver forces similar in magnitude and direction to those of natural chewing (Figure 2).

The test device delivered about 12 000 "bites" per hour to 5 specimens simultaneously, with an applied force of approximately 36 kg/cm2 at the incisal edge. For reference, the range of force per unit area on the biting surfaces of natural teeth during biting and chewing varies from a few grams per square centimeter to more than 150 kg/cm2. Vertical mobility at the fracture site was determined every 30 minutes, using a dial gauge to measure excursion of the point to which force was applied (Figure 3). The same steel flat-head screw to which force was applied was used as the reference point for measuring mobility. Measurement was made in hundredths of a centimeter per kilogram of distractive force (keeping in mind that this measurement refers to movement at the measuring point, not the fracture). The 10 model mandibles were tested for longer than 90 minutes, during which a total of 18 000 simulated bites were delivered. Each group of 5 was tested simultaneously. After 18 000 chewing cycles, the plates and screws were examined to determine the mode(s) of failure (defined by obvious loss of fixation and corresponding to fracture site mobility in excess of 0.005 cm/kg of distractive force). The distance from the point of application of force (where mobility was measured) to the intersection of the plate with the fracture line was 5.715 cm on all specimens. Simple geometric calculations were used to determine the actual mobility at the fracture site, using an estimated hypotenuse of 0.254 cm to approximate mobility within the fracture line. This produces a value somewhat in excess of the actual mobility at the bony interface.

RESULTS

The biplanar technique held 4 of 5 fractures secure through 18 000 cycles. The single-plate technique failed in 4 of 5 specimens after 12 000 cycles or less (Table 1). Because of the small numbers in the test group, the difference just achieved significance at P = .05 using the χ2 test. However, the Fisher exact test offered a "left-hand P" of> .99 to support the apparent significance of this difference in so small a pilot study. None of the plates broke, and all failures were attributable to loss of integrity of the threads in the bone with loosening of the screws. Interestingly, not all of the screws loosened equally on any plate. It was the outer 2 that were loosest on all but one of the failed plates.

COMMENT

Adams1 described open reduction and internal fixation of facial fractures using interosseous stainless steel wiring in 1942. He found this method to be "far simpler and more satisfactory than the use of extra-oral appliances attached to plaster headcaps,"1(p523) and spawned the modern era of facial fracture management. The reduction and immobilization of mandibular fractures with internal fixation subsequently evolved from loops of stainless steel wire threaded through holes drilled in bone to the use of plates made of stainless steel or more technologically advanced biomaterials like chrome-cobalt alloy (Vitallium) and titanium. Despite the wide variety of sizes, shapes, and characteristics of available plating systems, all share the principle of direct fixation to the fracture fragments with screws passed through holes in the plate. Furthermore, all have used a single plate for fixation, occasionally aided by a smaller plate in the same plane, known as a tension band, to minimize separation of the superior limit of the fracture.

Into the 1970s, research on mandibular fracture fixation with plates and screws was far advanced in Europe compared with the United States, resulting in the development of an assortment of plates and techniques from overseas. Luhr,3 in 1968, published his technique using biocompatible chrome-cobalt alloy plates with eccentric holes, combined with screw heads having a conical shoulder beneath the head. This produced axial compression of the fragments across the fracture line. The dynamic compression plate was introduced by Allgower et al4 in 1969 for use on extremity fractures. Allgower's colleague, Spiessl,5 then applied these plates to the mandible. Spiessl's presentation in 1982 of a series of 700 complicated mandibular fractures reduced and stabilized with various plates and techniques really focused attention on more sophisticated methods than the simple interosseous wiring most often used in the United States at the time. Spiessl's infection rate of 4% in 186 patients, with long-term follow-up, further impressed the North American facial plastic surgery community. These statistics, from patients treated with the Arbeitsgemeinschaft Osteosynthesefragen Association for the Study of Internal Fixation system, along with the new availability of versatile plating systems from other manufacturers, brought plate-and-screw fixation to the forefront of mandibular fracture management by the mid-1980s.

The miniplate system was introduced by Benoit et al,6 tested by Michelet and Deymes,7 and refined by Champy et al.8 Placing smaller plates required less soft tissue dissection, minimizing surgical trauma yet achieving extremely stable fracture fixation. Champy et al did some of the first in vitro studies to determine the multiple forces at work in mastication. They also used a compression plate and a tension band in the same plane to fix fractures in the mandible.

Schmoker9-10 and colleagues also performed several in vitro studies comparing and testing eccentric compression plates and tension bands, using a cantilever beam model and synthetic mandibles. They, too, noted that a 2-plate system provided more resistance to vertical deformation.

Rigid internal fixation with plates and screws has been compared extensively with intermaxillary fixation, alone and in combination with interosseous wiring. No clear consensus or preference exists in the literature. There are several advantages to the plate-and-screw method. Absolute immobilization of fracture lines allows for early function of the mandible, minimizing disuse muscular atrophy and temporomandibular joint dysfunction. Lack of time or shortened time in an immobilization mandibular fracture provides for improved oral hygiene, adequate nutritional intake, communication, and airway management. Plate-and-screw repair is associated with lower infection rates and improved overall outcome compared with interosseous wires.11 However, Terris et al12 report in their series that wires are more cost-effective and have a lower incidence of major complications. Leach and Truelson13 also advocate an immobilization mandibular fracture and interosseous wiring. They found that their patients treated with newer techniques had a greater incidence of infection, nerve injury, and unavailability for follow-up. Valentino et al,14 in their series of 287 patients during a 5-year period, showed that monocortical miniplate fixation is a reliable method for achieving rigid immobilization. They compared their results with those of others using compression plating and found monocortical miniplate fixation to be comparable.

The key to fracture healing is rigid fixation of bone-to-bone contact. Any mobility at the fracture site can lead to infection, poor healing, malunion, or even nonunion and osteomyelitis. There are several forces operating on the mandible during function. When loaded by mastication, there is a distracting force along the alveolar ridge and a compressing force along the inferior border. The complexity of the forces delivered to the mandible must be understood for proper fixation of fracture sites. Distractive and compressive forces can act along the same fracture line at different times during mastication. Spiessl5 and Champy et al8 understood and considered this in their approaches to rigid fixation. Spiessl applied an arch bar as a tension band to resist the distractive force along the alveolar ridge. He advocated a compression plate at the basal border to provide compression across the fracture. This combination provides adequate compression along the entire length of the fracture and resists distraction in the superior part of the fracture. As described by Marentette,15 Champy et al tested various plating schemes on cadaver mandibles subjected to various forces, and studied the biting forces applied to different areas of the mandible in human subjects. Armed with this knowledge, they determined the optimal areas for plating, deemed "Champy's Ideal Line of Osteosynthesis." The principles of Champy et al involved the use of a tension band with monocortical screws at the superior border of the mandible and a noncompression miniplate at the inferior border—but both plates were in the same vertical plane. This combined the concept of stabilization with neutralizing tension using 2 plates in the same plane.

The goal of rigid internal fixation is the achievement of rapid primary bone healing, with solid union of the fracture fragments, without compromising oral health and jaw function. Plate-and-screw techniques, using compression or noncompression plating, decrease the incidences of infection, malunion, and nonunion in patients while avoiding or decreasing time in maxillomandibular fixation. Without time in maxillomandibular fixation, patients load the mandible early in the bone-healing process. This requires fixation that is secure despite the forces of mastication. Plate failure was observed by Ardary,16 who presumed the mechanism of failure to be faulty screw placement, although he attributed loose screws to dietary noncompliance causing premature loading of the mandible. Haug et al,17 in their studies, reported that 100% of plate failures were due to loosening of monocortical screws securing tensions bands at the superior border of the mandible. Suboptimal bone health was also thought to contribute to loosening of screws under loading forces.

In the 1998 study cited earlier, Fedok et al2 did not account for the soft tissue that suspends the native mandible, nor did they consider the viscoelastic nature of in vivo mandibular suspension. We attempted to simulate this by using a viscoelastic polymer to coat the fracture and plates, and by supporting the angle of each test hemimandible on a 2.540-cm thick roll of dense silicone polymer. We also believed that the vector forces applied to the mandible were not accurately simulated by the rigid fixation of the test mandibles at the condyle. By suspending the test mandibles on a well-fitted round shaft through the condyles, rotation of the proximal fragment is permitted, similar to that of the mandible during chewing. We recognize that the translational component of physiologic condylar motion is missing, but do not believe that this is important because identical forces are being delivered to all test specimens. Furthermore, a minimal translational component would affect all specimens slightly, if at all, and in the exact same way.

Our device, therefore, more precisely portrays the masticatory forces at work during function than others previously described. Because our fractures were within the body, as opposed to through the angle, we cannot directly compare our findings with those of Fedok et al.2 However, we conclude that biplanar plating is superior to monoplanar plating, as did Fedok et al.

We have also used our technique on 15 mandibular fractures during the past decade, without operative or healing complications. Because the small plates on the inferior mandibular border are not readily demonstrable on postreduction films, we are unable to demonstrate this radiographically.

CONCLUSIONS

Placement of a small (1.7-mm) linear plate along the inferior mandibular border across mandibular body fractures greatly increases the stability of traditional buccal cortex plating when exposed to the forces of mastication. This technique is especially useful when access to extended lengths of intact mandible is difficult and only 2 screws can be used to secure a buccal cortex plate on either side of a fracture. The tiny plates and screws are not radiographically demonstrable on plain postreduction films, because of their small size and because they are placed in the horizontal plane of the inferior mandibular cortex, presenting a small profile to the x-ray beam.

Use of a miniplate on the inferior mandibular border in addition to a buccal cortex plate may add significant security to the repair of mandibular body fractures and obviates the need for a tension band. Placement is quick and easy through percutaneous access, and minimizes the extent of dissection compared with placement of a tension band when the percutaneous route of access is chosen.

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Article Information

Accepted for publication January 23, 2001.

This study was presented at the meeting of the American Academy of Facial Plastic and Reconstructive Surgery, Orlando, Fla, May 13, 2000.

Corresponding author: David Reiter, MD, DMD, Department of Otolaryngology–Head and Neck Surgery, Jefferson Medical College, 925 Chestnut St, Sixth Floor, Philadelphia, PA 19107 (e-mail: david.reiter@mail.tju.edu).

References
1.
Adams  W Internal wiring fixation of facial fractures. Surgery. 1942;12523- 540
2.
Fedok  FGVan Kooten  DWDeJoseph  LM  et al.  Plating techniques and plate orientation in repair of mandibular angle fractures: an in vitro study. Laryngoscope. 1998;108 (pt 1) 1218- 1224Article
3.
Luhr  HG On the stable osteosynthesis in mandibular fractures [in German] [abstract] Dtsch Zahnarztl Z. 1968;23754
4.
Allgower  MEhrsam  RGanz  RMatter  PPerrin  SM Clinical experience with a new compression plate "DCP". Acta Orthop Scand Suppl. 1969;12545- 61
5.
Spiessl  B Early treatment of complicated mandibular fractures by means of rigid internal fixation according to AO principles. Maxillofacial Trauma: An International Perspective. New York, NY Praeger1983;177- 186
6.
Benoit  PMichelet  FBenoit  JPFestal  FDessus  BMoll  A Treatment of mandibular fractures without blocking by means of a juxta-alveolar screwed plate inserted through the mouth: 60 cases [in French]. Rev Stomatol Chir Maxillofac. 1971;72313- 315
7.
Michelet  ADeymes  J Osteosynthesis with screwed plates in maxillofacial surgery: experience with 500 satellite plates. Int Surg. 1973;58249- 253
8.
Champy  MLodde  JPSchmitt  RJaeger  JHMuster  D Mandibular osteosynthesis by miniature screwed plates via a buccal approach. J Maxillofac Surg. 1978;614- 21Article
9.
Schmoker  RSpiessl  B Excentric-dynamic compression plate: experimental study as contribution to a functionally stable osteosynthesis in mandibular fractures [in German]. SSO Schweiz Monatsschr Zahnheilkd. 1973;831496- 1509
10.
Schmoker  RSpiessl  BTschopp  HMPrein  JJaques  WA Functionally stable osteosynthesis of the mandible by means of an eccentric-dynamic compression plate: results of a follow-up of 25 cases [in German]. SSO Schweiz Monatsschr Zahnheilkd. 1976;86167- 185
11.
Hoffman  WBarton  RPrice  MMathes  S Rigid internal fixation vs traditional techniques for the treatment of mandible fractures. J Trauma. 1990;301032- 1035Article
12.
Terris  DJLalakea  MLTuffo  KMShinn  JB Mandible fracture repair: specific indications for newer techniques. Otolaryngol Head Neck Surg. 1994;111751- 757Article
13.
Leach  JTruelson  J Traditional methods vs rigid internal fixation of mandible fractures. Arch Otolaryngol Head Neck Surg. 1995;121750- 753Article
14.
Valentino  JLevy  FEMarentette  LJ Intraoral monocortical miniplating of mandible fractures. Arch Otolaryngol Head Neck Surg. 1994;120605- 612Article
15.
Marentette  L Miniplate osteosynthesis of mandible fractures. Operative Tech Otolaryngol Head Neck Surg. June1995;6
16.
Ardary  W Prospective clinical evaluation of the use of compression plates and screws in the management of mandible fractures. J Oral Maxillofac Surg. 1989;471150- 1153Article
17.
Haug  RHBarber  JEReifeis  R A comparison of mandibular angle fracture plating techniques. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1996;82257- 263Article
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