CB Indications for lag screw. Technique?Article they requested was not on lag screws:J Craniomaxillofacial trauma form 1997, Lag screw techniuq of mandible fractures, Ellis It is a simple technique, has a wide application and achieves great stability but over the years has been foundto be very techinquesensitive.Most useful for mandibular body, angle and symphis of non-compound fractures. From the AO foundation 1 PrinciplesLagscrewfixationLag screw fixation uses stabilization by compression that relies on the bony buttressing of the fracture to help stability (load-sharing osteosynthesis). Lag screws should always be placed perpendicular to the fracture plane to prevent displacement of the fragments when the screws are tightened and the bones are compressed. BiomechanicsofthesymphysisThe mandibular symphysis undergoes torsional forces (twisting) during function. Therefore, fixation strategies must take this into account. When using anything less stable than a reconstruction plate, two points of fixation should be applied. In general, the further apart the points of fixation, the more stable the construct. For symphysis fractures, when two lag screws are applied, they should be separated as much as possible without injuring vital structures. Illustration shows Champys ideal lines of osteosynthesis for symphysis fractures. SpecialconsiderationsFollowing special considerations may need to be taken into account:MultiplefracturesplatingbeterEdentulousatrophicfracturesnotindicatedwillfractureatrophicmandibleTeethinthelineoffracturesnotindicatedunlessremovedfirstInvolvementofalveolarareaInfectedfracturewithorwithoutbonelossComplicationsClick on any subject for further detail.2 ReductionDrillingmonocorticalholesIt is necessary to predrill two monocortical holes below the apices of the teeth on either side of the fracture to help place the reduction forceps. Manipulate the mandible fragments until anatomic reduction is achieved. Apply the reduction forceps and then place the patient into occlusion and secure with MMF. Some surgeons prefer to place the patient into occlusion and apply MMF before using the reduction forceps. ClampapplicationThe clamp has to be placed perpendicular to the line of fracture to prevent fracture displacement when tightening the reduction clamp. 3 FixationLagscrewinsertionDepending on the fracture plane orientation, lag screw alignment will vary. For sagittal fractures through the anterior mandible, lag screws placed through the outer cortices from one side to the other within the substance of the mandible (buccal cortex to buccal cortex) provide extremely stable fixation. Note that the screws and the resultant compression are directed perpendicular to the bevel of the fracture. For fractures that obliquely pass through the mandible, lag screws are placed from the buccal to the lingual cortices. Note that the screws and the resultant compression are again directed perpendicular to the bevel of the fracture. NumberofscrewsIn general, a minimum of two lag screws should be used to provide stable internal fixation of mandibular symphysis fractures. Because the symphysis undergoes twisting during function, a single lag screw cannot prevent such motion from occurring. Alternative:screwsplacedfromoppositesidesOccasionally it is more convenient to place screws from opposite sides. From a biomechanical standpoint it is irrelevant. ConfirmationofreductionConfirm adequate reduction. There should be no gap at the lingual aspect that would lead to occlusal disturbance and mandibular widening. MMF should be released and the occlusion checked. Because two points of fixation have been applied (two lag screws), it is not essential that the mandibular arch bar remains in position to function as another point of fixationCompletedosteosynthesisX-ray shows the completed osteosynthesis. 8.4.11 CB What methodologies are available for the edentulous mandible? Luhr HG, Reidick T, Merten HA. Results of treatment of fractures of the atrophic edentulous mandible by compression plating: a retrospective evaluation of 84 consecutive cases. J Oral Maxillofac Surg. 1996 Mar;54(3):250-4; discussion 254-5. PMID:8600229 1 DiagnosisGeneralconsiderationsWith increasing mandibular atrophy, the physical size of the mandible decreases. In the severely atrophic mandible, even very minor trauma can cause fracture. Additionally, pathologic fracture during mastication can occur. Very often, due to the fragile nature of the jaw, these fractures occur bilaterally. Orthopantomogram (OPG), mandible series radiograph and CT scans can be used to diagnose and plan the treatment of the atrophic edentulous mandible fractures. ClinicalexaminationThe patient shows extraoral ecchymosis associated with an atrophic edentulous mandible fracture. The patient exhibits pain and mobility of the anterior mandible. Patient shows intraoral ecchymosis in the floor of the mouth associated with an atrophic edentulous mandible fracture. Typicalexampleofanatrophicedentulousmandiblefracture.Axial CT scan showing bilateral fractures. Note that although there appears to be a large bone stock, this patients mandible has only approximately 7 mm of vertical height. Panoramic radiograph of atrophic edentulous mandible fractures. Note the extreme amount of vertical atrophy. 3-D reconstruction of the same case. 2 Decision/IndicationObservationandsoftdietObservation may be indicated for patients medically unfit for general anesthesia. Atrophic edentulous mandible fracture patients are often elderly with medical problems presenting severe anesthetic risks. One major complication of observation and soft diet would be nonunion of the mandibular fracture. ClosedreductionHistorically, atrophic edentulous fractures were treated closed by wiring in the patients dentures or fabricating Gunning style splints with postoperative mandibulomaxillary fixation (MMF). Standard treatment with closed reduction often resulted in prolonged periods of MMF which was difficult for these patients. Additionally, the fractures were often poorly aligned. Postoperative malunions and nonunions were very common. Photograph shows a patient denture. Photograph shows a Gunning style splint. ORIFIndications for ORIF are any displaced atrophic mandible fracture requiring surgical intervention. Following the AO principles of anatomic reduction of fractures and immediate function, ORIF of atrophic edentulous mandible fractures with load-bearing osteosynthesis has a distinct advantage for these patients. The technique has evolved to provide the patient with an excellent chance for mandibular union while the ability to masticate is preserved. Literature has supported the efficacy of this technique. ExternalfixationIndications of external fixator might be the temporary stabilization of a fracture while the patient is treated medically, or if soft-tissue maturation around the fracture site is required. Complications,including malunion and nonunion are significant when external fixators are used as they do not provide absolute stability at the fracture site. 3 Treatment of an edentulous atrophic fracture with a reconstruction plateIn the following, the treatment of an edentulous atrophic fracture with a reconstruction plate is described step-by-step. 4 Approach ExtraoralappraochWhen treating atrophic edentulous mandible fractures, the surgeon will generally find it easier to use an extraoral surgical approach. The fracture fragments can be manipulated under direct visualization and stabilized while the reconstruction plate is being bent and applied to the mandible. IntraoralapproachAn intraoral approach is possible but technically more difficult as the surgeon will need several sets of trained hands just to retract the soft tissues of the cheeks and tongue. Additionally, stabilization and fixation of the fractures is much more difficult via an intraoral approach. One should also be aware that the inferior alveolar nerve is located on the superior surface of the atrophic mandible. Therefore one must be extremely careful making intraoral incisions to expose atrophic fractures, or the nerve can be damaged. 5 PrinciplesThe atrophic edentulous mandible fracture presents with several factors which make treatment very difficult. There is a lack of bone which is generally cortical in nature and has a lower healing potential. There are no teeth present to help reduce the fractures. Often the patients are elderly and medically compromised. Atrophic mandible fractures require transfacial open reduction, load-bearing internal fixation, and often immediate bone grafting. 6 Choice of implantGeneralconsiderationsLoad-bearing osteosynthesis is indicated in treatment of the atrophic edentulous mandible fracture. We currently recommend the locking reconstruction plate 2.4. The plate must be of sufficient length to place screws in adequate bone which is generally found in the symphysis and angle regions. The body region of the mandible is a common area of fracture and generally has bone of poorer quality unsuitable for screw placement. When dealing with bilateral fractures, the plate must span from angle to angle, covering the entire lateral surface of the mandible. At least three screws on either side of the fracture are recommended. Often more screws are necessary due to the poor quality of the bone. The locking reconstruction plate is generally left in place and not removed unless clinical symptoms require hardware removal. Pitfall:insufficientlystableimplantIt may be tempting to use small plates when treating fractures in an atrophic small jaw. However, when using small plates, plate fracture and displacement is very common secondary to the muscle pull involved in the atrophic edentulous mandible. X-ray shows fractured plate and fracture displacement. Clinical photograph shows same case. Alternativestothelockingreconstructionplate2.4There are fractures involving the edentulous jaws which are not atrophic in nature. When there is sufficient bone to buttress the fracture and provide adequate healing, the surgeon may choose to use a smaller reconstruction plate. The locking plate system 2.0 (large or extra-large profile) provides all the advantages of a locking reconstruction plate 2.4 but with a smaller profile. Many surgeons have successfully used the locking system 2.0 on edentulous fractures.

PlatedesignThe locking reconstruction plate combines all the advantages of a standard reconstruction plate with the locking principle. The thread in the plate holes provides rigid anchorage for the 2.4 mm locking screw. This construction acts as an internal fixator. 3.0 mm screws are also available. The conventional 2.4 mm nonlocking cortex screw can also be used with this plate. Wide angulation of the screw is possible which, in certain clinical situations, can be an advantage. Other advantages of the locking principle are: TheplateneedsonlylimitedadaptationItexertsnopressureontheboneTheriskofscrewslooseningisreduced.7 Plate bendingTemplatingIt is very common to use large reconstruction plates that span from angle to angle. By using a template the bending process is facilitated. BendingClinical image shows the template and the reconstruction plate bent accordingly. Pearl:reductionandtemporaryfixationIt can be very helpful to reduce and stabilize the fracture with adaptation plates to allow appropriate bending of the template and reconstruction plate. This is particularly applicable in fractures that are widely displaced, mobile, or unstable. The adaptation plates are placed on the inferior border to allow excellent reconstruction plate adaption to the lateral surface of the mandible. After the locking reconstruction plate has all planned screw holes used, the adaptation plates are removed. Pearl:perfectadaptationPerfect adaptation of the plate is not required as the locking reconstruction plate 2.4 acts as an internal external fixator. 8 FixationGeneralconsiderationsThe locking reconstruction plate 2.4 is fixed to the native mandible using either 2.4 mm or 3.0 mm screws. At least three screws must be present on either side of the fracture. In the atrophic edentulous mandible fracture, the screws are generally placed in the symphyseal region and the angular region. The bone in the symphysis is very often dense cortical bone which may require tapping of the screw hole. ApplyingtheplateApply the plate and stabilize it either with digital pressure or plate-holding forceps. One of the benefits of using a locking reconstruction plate is that perfect adaptation is not required and small discrepancies can be tolerated. PlacementoffirstscrewsPlace one screw on either side of fracture in the planned holes closest to the fracture. A threaded drill guide must be used to allow for centric placement of the drill hole for use with the locking screw. Copious irrigation must be applied to cool the bone. A depth gauge is used to determine the appropriate screw length.AdditionalscrewplacementOnce the screws are placed on either side of the fracture (on the first side) the surgeon has the option of completing all screws on that one side or placing one screw on either side of the fracture (on the opposite side) before completing all screws. Clinical image shows the plate fixed to the mandible. HarvestingofbonegraftDue to the poor healing quality of the bone, an autogenous bone graft is often used to facilitate bony union. Common sites of bone graft harvest include the iliac crest or tibia. Clinical images show ... ... the bone graft harvest site in the tibia. BonegraftapplicationAutogenous cancellous bone grafts can be added to fracture sites and can be used to augment the native mandible to facilitate healing. CompletedosteosynthesisX-ray shows the completed osteosynthesis. 9 Aftercare following treatment of an edentulous atrophic fracture with a reconstruction plate If MMF screws are used intraoperatively in conjunction with the patients prostheses, they are usually removed at the conclusion of surgery if proper anatomic fracture reduction and fixation have been achieved. Postoperative x-rays are taken within the first days after surgery. In an uneventful course, follow-up x-rays are taken after 46 weeks. The patient is examined approximately 1 week postoperatively and periodically thereafter to assess the stability of the fracture and to check for infection of the surgical wound. During each visit, the surgeon must evaluate the patients ability to perform adequate oral hygiene and wound care, and provide additional instructions if necessary.Follow-up appointments are at the discretion of the surgeon, and depend on the stability of the mandible on the first visit. Weekly appointments are recommended for the first 4 postoperative weeks. Postoperatively, patients will have to follow three basic instructions: 1. Diet Depending upon the stability of the internal fixation, the diet can vary between liquid and semi-liquid to as tolerated, at the discretion of the surgeon. 2. Oral hygiene Patients having only extraoral approaches are not compromised in their routine oral hygiene measures and should continue with their daily schedule. Patients with intraoral wounds must be instructed in appropriate oral hygiene procedures. A soft toothbrush (dipping in warm water makes it softer) should be used to clean the oral cavity. Chlorhexidine oral rinses should be prescribed and used at least three times each day to help sanitize the mouth. For larger debris, a 1:1 mixture of hydrogen peroxide/chlorhexidine can be used. The bubbling action of the hydrogen peroxide helps remove debris. 8.4.12 CB Where do the pterygoids attach? What do they do? MedialPterygoidOriginandinsertionItconsistsoftwoheads.Thebulkofthemusclearisesasadeepheadfromjustabovethemedialsurfaceofthelateralpterygoidplate.Thesmaller,superficialheadoriginatesfromthemaxillarytuberosityandthepyramidalprocessofthepalatinebone.Itsfiberspassdownward,lateral,andposterior,andareinserted,byastrongtendinouslamina,intothelowerandbackpartofthemedialsurfaceoftheramusandangleofthemandible,ashighasthemandibularforamen.Theinsertionjoinsthemassetermuscletoformacommontendinousslingwhichallowsthemedialpterygoidandmassetertobepowerfulelevatorsofthejaw.InnervationLikethelateralpterygoid,andallothermusclesofmasticationthemedialpterygoidisinnervatedbytheanteriorroot(motorroot)ofthemandibularbranchofthetrigeminalnerve(V).ActionsGiventhattheoriginisonthemedialsideofthelateralpterygoidplateandtheinsertionisfromtheinternalsurfaceoftheramusofthemandibledowntotheangleofthemandible,itsfunctionsinclude:Elevationofthemandible(closesthejaw)MinorcontributiontoprotrusionofthemandibleAssistanceinmasticationExcursionofthemandible;contralateralexcursionoccurswithunilateralcontraction.LateralPtyergoid:OriginandinsertionTheupper/superiorheadoriginatesontheinfratemporalsurfaceandinfratemporalcrestofthegreaterwingofthesphenoidbone,andthelower/inferiorheadonthelateralsurfaceofthelateralpterygoidplate.Inferiorheadinsertsontotheneckofcondyloidprocessofthemandible;upper/superiorheadinsertsontothearticulardiscandfibrouscapsuleofthetemporomandibularjoint.InnervationThemandibularbranchofthefifthcranialnerve,thetrigeminalnerve,specificallythelateralpterygoidnerve,innervatesthelateralpterygoidmuscle.FunctionTheprimaryfunctionofthelateralpterygoidmuscleistopulltheheadofthecondyleoutofthemandibularfossaalongthearticulareminencetoprotrudethemandible.Aconcertedeffortofthelateralpterygoidmusclesactsinhelpinglowerthemandibleandopenthejawwhereasunilateralactionofalateralpterygoidproducescontralateralexcursion(aformofmastication),usuallyperformedinconcertwiththemedialpterygoids.Unliketheotherthreemusclesofmastication,thelateralpterygoidistheonlymuscleofmasticationthatassistsindepressingthemandible(openingthejaw).Atthebeginningofthisactionitisassistedbythedigastric,mylohyoidandgeniohyoidmuscles8.4.13 CB What is the rate of lingual injury associated with mandible fractures? What about of alveolar nerve? DamageofInferiorAlveolarNerveinMandibleFractureCasesDainiusRazukevicius,Stomatologija,BalticDentalandMaxillofacialJournal,6:12225,2004When mandibular fracture occurs on angle zone, inferior alveolar nerve always is injured,andatitsinnervationpointemergesensationdisorders(lowerlips,chin,alveolarprocess).Patientsfeelonthisareadiscomfort,paresthesia,sometimesevenpain.Thisconditionhasnegative influence on psychoemotional status of person and reduces working capacity.LesionsofinferioralveolarnerveandvascularbundlehaveaninfluenceoncourseoflowerjawhealingLingual nerve injury seems to be more associated with condylar process fractures. Couldnot find any rates in the literature though, certainly less common than alveolar nerveinjury.