Biplanar Plating of Mandibular Fractures a New Concept with in Vitro Testing and Comparison with the Traditional Plate-And-Screw Technique

ORIGINAL ARTICLE Biplanar Plating of Mandibular Fractures A New Concept With In Vitro Testing and Comparison With the Traditional Plate-and-Screw Technique Sara Pieri, MD; K. Holly Gallivan, MD, MPH; David Reiter, MD, DMD Objectives: To introduce the concept of biplanar plat- Results: Of 5 specimens plated with a mandibular fixa- ing of mandibular fractures and to present an in vitro com- tion plate, 4 developed greater than 0.010 cm of vertical parison of this method with traditional use of a single mobility at the fracture site after 12000 cycles. Only 1 mandibular plate. of the 5 specimens fixed with biplanar plating developed this degree of mobility. Design: A device for the delivery of repetitive simulated masticatory stress to mandibular models was de- Conclusions: Single-plate fixation of mandibular fractures veloped. Using the device, we compared biplanar with is greatly enhanced by a miniplate spanning the fracture single-plate fixation of vertical mandibular body frac- along the inferior border. We used this technique on 15 tures by determining cycles to failure. patients with unfavorable fractures and found it simple, secure, and reliable. We had no complications. An inferior Setting: Tertiary care academic medical center. marginal plate serves the same function as a tension band, and can be placed on mandibles through the same incision Intervention: A simulated masticatory force was de- as the main fixation plate without additional dissection. We livered vertically to the anterior end of polymer hemi- prefer this to a traditional tension band when the percuta- mandibles as used for in vitro teaching of plating meth- neous route of access to a mandibular fracture site is used. ods. Mobility at the fracture site was tested at intervals corresponding to 6000 chewing cycles each. Arch Facial Plast Surg. 2002;4:47-51 N THE 60 YEARS since Adams1 ent plane from the fixation plate (but still described open reduction and in- on the buccal cortex), which Fedok et al ternal fixation of facial fractures termed biplanar plating. Because we had with interosseous stainless steel been using this term for several years in wiring, mandibular fracture re- reference to the placement of a 1.7-mm Ipair has evolved through a series of ma- miniplate along the inferior mandibular terials and methods. We have progressed border in addition to a standard 2.4-mm far beyond simple wire loops placed plate on the buccal cortex, we were stimu- through burr holes in bone, and have plat- lated by the in vitro study by Fedok et al ing systems of great sophistication (and, to test our technique against monocorti- in some cases, complexity). There are sys- cal plating with a neutral (ie, noncom- tems with screws having threaded heads pression) 2.4-mm mandibular recon- and shanks, systems with hollow screws struction plate. We wanted to establish for osseointegration, and even systems with whether and to what degree the addition absorbable plates and screws. But the gold of a small inferior cortex plate increases standard for primary plate fixation of man- stability of fixation of mandibular body dibular fractures remains the single plate fractures. on the buccal cortex. There are few studies in the litera- RESULTS ture on in vitro testing of mandibular fracture fixation. Those studies that are found The biplanar technique held 4 of 5 frac- From the Department of use synthetic or cadaver mandibles in a tures secure through 18000 cycles. The Otolaryngology–Head and common cantilever beam device. A re- single-plate technique failed in 4 of 5 speci- Neck Surgery, Jefferson Medical cent article by Fedok et al2 introduced the mens after 12000 cycles or less (Table). College, Philadelphia, Pa. idea of a tension band placed in a differ- Because of the small numbers in the test (REPRINTED) ARCH FACIAL PLAST SURG/ VOL 4, JAN-MAR 2002 WWW.ARCHFACIAL.COM 47 ©2002 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/28/2021 MATERIALS AND METHODS incisors by rotating a motor-driven camshaft against the specimens to deliver forces similar in magnitude and di- rection to those of natural chewing (Figure 2). As with other in vitro studies, polystyrene mandibles, with The test device delivered about 12000 “bites” per a rigid outer cortex and a trabecular medullary space, were hour to 5 specimens simultaneously, with an applied used to simulate physiologic properties. These uniform force of approximately 36 kg/cm2 at the incisal edge. For sample mandibles are preferred because they eliminate the reference, the range of force per unit area on the biting variability associated with cadaveric mandibles, and do not surfaces of natural teeth during biting and chewing varies undergo changes in physical properties with drying. A band from a few grams per square centimeter to more than 150 saw with a fine blade was used to create linear fractures in kg/cm2. Vertical mobility at the fracture site was de- the body of each test mandible just distal to the second mo- termined every 30 minutes, using a dial gauge to mea- lar, in a standardized fashion and with neither favorable sure excursion of the point to which force was applied nor unfavorable angulation. Following manual reduction (Figure 3). The same steel flat-head screw to which of the fractures, 5 of the hemimandibles were stabilized us- force was applied was used as the reference point for mea- ing a standard, neutral, 2.4-mm mandibular plate on the suring mobility. Measurement was made in hundredths of buccal cortex, with 2 screws on either side of the fracture. a centimeter per kilogram of distractive force (keeping in A 1.7-mm miniplate was placed along the inferior border mind that this measurement refers to movement at the of 5 specimens in a plane perpendicular to the main fixa- measuring point, not the fracture). The 10 model man- tion plate, also with 2 screws on either side of the fracture. dibles were tested for longer than 90 minutes, during The other 5 specimens were stabilized with neutral man- which a total of 18000 simulated bites were delivered. dibular plates identical to those on the buccal cortices of Each group of 5 was tested simultaneously. After 18000 the first group, but without the addition of a miniplate on chewing cycles, the plates and screws were examined to the inferior cortical surface (Figure 1). determine the mode(s) of failure (defined by obvious loss The test mandibles were secured by a 0.794-cm stain- of fixation and corresponding to fracture site mobility in less steel rod with 0.008 cm of clearance in precision- excess of 0.005 cm/kg of distractive force). The distance drilled holes through the condyles. The fracture lines and from the point of application of force (where mobility was plates were coated with a thin application of silicone caulk- measured) to the intersection of the plate with the frac- ing to simulate the viscoelastic properties and vibration- ture line was 5.715 cm on all specimens. Simple geomet- dampening effect of the native soft tissue adherent to in vivo ric calculations were used to determine the actual mobil- fractures. Testing was conducted in a jig that stabilized the ity at the fracture site, using an estimated hypotenuse of proximal mandibular fragment on a firm elastic polymer 0.254 cm to approximate mobility within the fracture to simulate the muscular sling of the medial pterygoid and line. This produces a value somewhat in excess of the masseter. Vertical forces were then applied to the central actual mobility at the bony interface. Figure 1. Biplanar (top) and monoplanar (bottom) plate application. Figure 2. The test fixture. group, the difference just achieved significance at P=.05 COMMENT using the ␹2 test. However, the Fisher exact test offered a “left-hand P”ofϾ.99 to support the apparent signifi- Adams1 described open reduction and internal fixation cance of this difference in so small a pilot study. None of facial fractures using interosseous stainless steel wir- of the plates broke, and all failures were attributable to ing in 1942. He found this method to be “far simpler and loss of integrity of the threads in the bone with loosen- more satisfactory than the use of extra-oral appliances ing of the screws. Interestingly, not all of the screws loos- attached to plaster headcaps,”1(p523) and spawned the mod- ened equally on any plate. It was the outer 2 that were ern era of facial fracture management. The reduction and loosest on all but one of the failed plates. immobilization of mandibular fractures with internal fixa- (REPRINTED) ARCH FACIAL PLAST SURG/ VOL 4, JAN-MAR 2002 WWW.ARCHFACIAL.COM 48 ©2002 American Medical Association. All rights reserved. Downloaded From: https://jamanetwork.com/ on 09/28/2021 tion subsequently evolved from loops of stainless steel known as a tension band, to minimize separation of the wire threaded through holes drilled in bone to the use superior limit of the fracture. of plates made of stainless steel or more technologically Into the 1970s, research on mandibular fracture fixa- advanced biomaterials like chrome-cobalt alloy (Vital- tion with plates and screws was far advanced in Europe lium) and titanium. Despite the wide variety of sizes, compared with the United States, resulting in the devel- shapes, and characteristics of available plating systems, opment of an assortment of plates and techniques from all share the principle of direct fixation to the fracture overseas. Luhr,3 in 1968, published his technique using fragments with screws passed through holes in the plate. biocompatible chrome-cobalt alloy plates with eccen- Furthermore, all have used a single plate for fixation, oc- tric holes, combined with screw heads having a conical casionally aided by a smaller plate in the same plane, shoulder beneath the head.

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