 Today we shall be discussing condylar fractures under the headings, anatomy of TMJ, mechanism of condylar injuries and classification of condylar fractures. Let us have a quick look at the anatomy of Temporomandublar joint. TMJ basically has two components, a passive component and active component. Passive components are the glenoid fossa which is a part of the temporal bone, condyle which is part of the mandible and articular eminence, capsules and ligaments and articular disc. These five are the passive components of TMJ of which the glenoid fossa, condyle and articular eminences are made up of bones or heart tissue and the capsules and ligaments and the disc are made up of soft tissue. The active components of Temporomandublar joint are the muscles of mastication, all the muscles of mastication, the temporal, temporalis muscle, medial and lateral tergoid and mesater, all these fall under the active components of TMJ. TMJ is formed by the mandibular condyle fitting into the mandibular fossa and the two bones are separated by articular disc. The different capsular and ligament attachments are the fibrous capsule. Fibrous capsule or the joint capsule covers the entire joint. Temporomandublar or lateral ligament. It extends from the zygomatic process to the lateral aspect of condylar head. Spenomandublar ligament is an accessory ligament that extends from the spinal spinae to the tip of lingula on the medial aspect of the ramus. Stylomandibular ligament is the fourth ligament which extends from the styloid process to the posterior border of ramus at the angle region. So these four structures have attachments to and around the TMJ and their main function is to control the excessive movement or to guide the direction of the condylar head and articular disc during the movement or functioning of TMJ. In the lecture on basics of management of mandibular fractures, we had seen how elevators and depressors act on a fracture to displace it. Latval tergoid has direct attachment to the anterior part of the neck of the condyle at the tergoid fovea and it can displace the fractured condylar head anteriorly and medially. The condylar head is a semi-cylindroid process which is 15-20 mm in length and 8-10 mm in thickness. The long axis of the condyle is related to the position of the ramus of mandible and not to the skeleton. It is not related to the skeletal axis but it is related to the ramus of the mandible. The angle formed by the two condylar axes varies between 145 degree to 160 degree. This is an axial section of the CT showing cross-sections of condyles on both the sides. So it is told that it is found out that the two condyles meet at the ferraman magnum at an angle of 145 to 160 degrees. The vascular supply to the TMJ arises anteriorly from the mesotvic artery and posteriorly from the branches of superficial temporal and maxillary arteries. All these are the branches of external carotid artery. The nerve supply to the joint is from the auricular temporal nerve with some additional innervation from mesotvic nerve and deep temporal nerves. These diagrams depict the anatomical and histological differences between the condylar heads of a child and an adult. As you can observe the cortical bone thickness at the condylar head in a child is very less when compared to that in an adult. The periosteum of the condyle facing the joint is in its active osteogenic state in a child whereas it has moved to the latent osteogenic state in an adult. Condylar neck in a child is broader with thin articular surface. Therefore, an impact at the condyle will confine the fracture within the capsule or it is called intracapsular fracture with hematrosis meaning bleeding and swelling within the joint. This carries a high risk of progressing into TMJ ankylosis. On the other hand in an adult the condylar neck is relatively narrow and the articular surface is thicker. Hence an impact to the condyle will result in extracapsular fracture with normal vascularity. Injury to the condyle may be caused by a variety of mechanisms. Lindal divided traumatic forces causing condylar injury into three categories. The first is energy imparted on a static individual by a moving object. For example a blow to the face by a fist or a bat or any other object. The second type of force is that of a moving individual striking a static object such as a child falling and hitting the chin against the pavement. This mechanism is also seen in padded ground fracture wherein a standing soldier collapses hits the chin onto the ground and fractures his condyle or mandible. The third classification is energy developed by a combination of the first two mechanisms. This type of force is typical of that generated during an automobile accident in which the individual is moving forward and the object is moving in the opposite direction. For example where a person is moving in a car and hitting his chin across the dashboard. There have been many studies into the resistance of mandible. This diagram shows the deformation of bone by an applied force. When a force causes compressive strain at one side it gets converted into tensile strain at another. It was found that bones fracture at sides of tensile strain because their resistance to compressive force is greater. Studies by Huell-Cann-Hodson showed that isolated mandible is liable to particular pattern of distribution of tensile strain when forces are applied to it. Other forces applied to the symphysis mentai, the mental famine or mandibular body gets converted into strain at condylar necks and the lingual plates on the contralateral side. The areas in red denote the force applied and the areas in blue denote the resultant tensile strain. The subcondylar fracture as you can see in this diagram is usually a result of indirect violence to the mental prominence or the contralateral body of mandible. As you already know the mesater has insertion at the lateral aspect of ramus. The medial teregoid has insertion at the medial aspect of ramus and lateral teregoid is inserted at the anterior neck of condyle. So usually a subcondylar fracture is evident just superior to the insertion of mesater therefore a coordinated action of the mesater and the teregoids will displace the condylar head in supido anterior and medial direction. Moving on to classification of condylar injuries. There are basically three types of injuries seen in temporal mandibular joint. They are contusion, dislocation and fracture. Contusion involves soft tissue injuries like that to ligaments, muscles, synovium and may cause formation of inflammatory exudates or hemarthrosis. A tear in meniscus can also result in osteoarthritis changes. Dislocation is a displacement of the condylar head completely out of the glenoid fossa which usually cannot be reduced by the patient. There is one more term associated with it it is called subluxation. In subluxation patient can reduce the displaced condylar head himself. And fracture can either be intra-capsular that means within the capsule like seen in majority of condylar fractures in children and also extra-capsular or subcondylar fractures as seen in adults. Different classification systems have been given by various authors. Here we shall be discussing two such systems in detail. The first system was given by Lindal in the year 1977. He proposed a system that classified condylar fractures based on several factors like based on anatomic location of the fracture, based on the relationship of the condylar segment to the mandibular fragment and based on the relationship between the condylar head and glenoid fossa. Let's see each of them in detail. Based on anatomic location of the fracture, he classified condylar fractures into fractures of the condylar head, condylar neck and subcondylar fractures. The condylar head is usually defined as the portion of the condyle superior to the narrow constriction of the condylar neck. Fractures of the condylar neck are intra-capsular means it is within the confinement of the fibrous capsule. The next classification is that of condylar neck. The neck is the thin constructed area located immediately below the condylar head. Therefore, it is extra-capsular. Any fracture at or below the condylar neck is considered extra-capsular fracture. Subcondylar fracture. So subcondyle is the region located below the condylar neck and extends from the deepest point of the sigmoid notch anteriorly to the deepest point along the concave posterior aspect of the ramus. So depending on the location, these fractures are described as high or low subcondylar fractures. Now based on the relationship of condylar segment to the mandibular fragment, fractures are classified as undisplaced or non-displaced. That means even if there is a fracture, the condylar head does not displace itself. So this is undisplaced fracture. Deviated. This involves only an angulation of the condylar fragment in relation to the mandibular segment. As you can see in the diagram, there is only a little bit of angulation of the condylar fragment. The fractured ends remain in contact with no separation or overlap. This is deviated fracture. Displacement with medial or lateral overlap. Here the fractured ends of the condylar segment lies either medially or laterally to the displaced of the distal mandibular segment. Medially displaced condylar fragment is more commonly seen. Displacement with anterior or posterior overlap. As you can see in the diagram here, the condylar head is displaced anterior to the mandibular segment. Or it can be displaced posteriorly also but it is very rare. And the sixth type is no contact. Here there is no contact at all between the condylar fragment and the mandibular distal fragment. So this is the classification of condylar fractures under the category based on the relationship of condylar segment to the mandibular fragment. Based on the relationship between the condylar head and the glenoid fossa, it can be classified as non-displaced, displaced and dislocated fractures. In non-displaced fracture, the condylar head is in normal relation to the glenoid fossa. As you can see here, the relationship between the condylar head and the glenoid fossa remains the same. In displaced fractures, the condylar head remains within the confinement of the fossa but there is alteration in the joint space. The normal anatomy is not being seen here. There is displacement or there is change in the relationship between the condylar head and the glenoid fossa. There is change in the joint space. And in dislocated fractures, the condylar head lies completely outside the fossa. The usual location of dislocation is antedomedial due to the pull of the lateral tear guard. So this is how lindhyl has classified condylar fractures. Based on the anatomic location of fracture, based on relationship of the condylar segment to maribula fragment and based on the relationship between the condylar head and the glenoid fossa. Another classification of condylar fractures was given by Matt Lenin in the year 1952. The system consists of four divisions, type I fracture or non-displaced fracture. As you can see in the diagram here, the fracture is non-displaced. Type II fracture or fracture deviation. This type consists of simple angulation of the fracture segment without overlap or separation. This type includes the green stick fracture which is common in children. Type III fracture or fracture displacement. Here the fracture is characterized by overlap of the proximal and distal fracture segments. The overlap can be anterior, posterior, lateral or medial. But medial displacements are more common. Type IV fracture is fracture dislocation. Here the condylar head is completely outside the glenoid fossa. Therefore it is complete extra-capsular fractures. Again the dislocation may be medial or lateral, anterior or posterior. So this is all about classification of condylar fractures. So we have seen in today's lecture the anatomy of TMJ, the mechanism and classification of condylar fractures. In the next lecture, we shall be discussing in detail about the management of condylar fractures. Thank you.