Mitek Anchor Surgery
Many patients who present for orthodontic corrections have some form of temporomandibular joint dysfunction (TMJD). These problems can extend from rather simple to extremely complex. The most difficult category includes those patients with internal joint derangement. Patients with dislocated non-recapturable temporomandibular joint (TMJ) are provided a new method of treatment. Mitek Anchor Surgery: Orthodontic patients are evaluated to determine whether they posses signs and symptoms of TMJD, or do they have normal joints. A joint is normal when the following characteristics exist: Painless, noiseless, full range of motion, and without deviation or deflection. A normal patient is generally free of headaches, neckaches, earaches, facial or joint pain.
The condyle should contact the central avascular portion of the disc which should function against the anterior slope of the eminence. There should be a consistent contact of these structures in all movements without any displacement or dislocation of the disk. The joint structure should be supported by normal muscle function with a Class I mutually protected occlusion.
The force applied by the condyle should resemble the black arrow in the diagram (left). This would maintain the disc position between the condyle and fossa. The condyle should not exert a straight upward vertical force against the disc as this would cause a distortion of the back (posterior laminar zone) of the disc. The enlarged posterior lamina helps maintain the disc position between the ball(condyle) and the socket or front wall (eminence). Posterior forces by the condyle would exert pressure against the posterior connective tissue, arteries, venules and nerves. There is no joint within the body where the forces are directed in this manner, leading Ide and Nakazawa to consider the up and back (posterior/superior) vector as a pathologic force.
Normal joints exist when the condyle exerts a force against the avascular central region of the disc (A). The condylar force exerted backwards (posterior and superior) distorts the back (posterior aspect) of the disc, decreasing the mechanical lock mechanics of the enlarged structures. Further compression continues the distortion of these back (posterior) structures, facilitates a thinning of the attachment, until the mechanical locking advantage is lost. When this occurs, the disc can become displaced. The posterior ligaments are stretched and the disc is pushed forward by the ball (condyle) until it becomes displaced or dislocated (left).
Normal joints should be painless, noiseless, with a full range of motion without deviation or deflection. In the beginning a patient presenting with this condition may not exhibit all the classic symptoms associated with a dislocated joint. Dislocated joints are not always painful, they do not always produce noise, but there would probably be a decreased range of motion and a probable deflection upon opening to the side of the dislocation. Joint noise should be a red flag to investigate the conditions of the joint to determine the cause of the noise.
When it is determined that a patient may have a displaced or dislocated joint, further diagnosis is warranted. Often this involves extensive radiographic evaluations, or other tests. An orthotic is a clinical means to evaluate the conditions within a joint. The response received provides information regarding the health, recovery potentials, and magnitude of dysfunction which may exist.
The usage of intraoral orthotics is essential to adequately diagnose joint conditions. There are many derivations of the basic splint design. It is essential to know what each appliance can do and be able to use the proper orthotic at the proper time. Usage of the wrong appliance provides inadequate information leading to an inaccurate diagnosis, or it may further the degeneration of the structures.When a patient does not respond to conventional diagnostic orthotics, further evaluations are necessary to determine the conditions within the joint. Often a magnetic resonance image (MRI) is used to examine the joint structures to determine the position and possible integrity of the disc. The following MRI demonstrates dislocated joint which does not reduce upon opening. The disc tissue (yellow arrow) is positioned in front of the ball of the joint, but retains a decent shape. This type of patient may be a candidate for Mitek anchor therapy.
The arrow points to the dislocated disc with the mouth closed. The condyle is positioned posterior/superior to the disc.
Upon opening, the disc remains in front of the condyle which is restricted in joint extension. Conservative therapy is unable to reposition the condyle to allow adequate room for the disc to “slip” back into the proper position (recapture). A decision must be rendered concerning the future health of the joint. Should the disc be allowed to remain dislocated, or should the disc be surgically repositioned?One method to evaluate the health of the joint involves the use of a quantitative radionuclide bone scan. Reference articles are provided if additional information is required concerning these tests. Assuming the bone scan is positive (indicating inflammation and an elevated osteogenic activity), it is not prudent to allow the positive on-going degenerative conditions to persist. Therefore, further intervention is warranted and the Mitek anchor treatment may be considered.
A Mitek anchor is a titanium condylar implant which is surgically placed in the posterior (back) aspect of the ball or condyle. Access to this region is made through a small incision in the ear canal (the external auditory meatus). A small incision is made in the front wall of the ear canal (external auditory meatus) exposing the back (posterior) aspect of the temporomandibular joint structures.
The incision avoids the structures of the facial nerve and many of the larger arterioles and venules found on the side of the face. Numbness (parasthesia) is extremely rare when avoiding the side of the face, but can occur. The incision is continued until the posterior aspect of the condyle is exposed.The Mitek anchor is composed of a titanium body with Nitinol wings with a small opening in the posterior aspect of the anchor body through which single or double thread O-Ethibond sutures can be passed.
The disc tissue is found and prepared for placement with a proper relationship to the condyle. A surgical bur makes a precise opening in the back of the ball so the anchor can be placed. Once the anchor is driven to place, tension will be applied to the sutures to engage the anchor wings.
The Mitek Anchor with the sutures is secured in a holding/delivery device which is used to carry the anchor attachment to the condyle.
The point of the anchor is inserted into the opening which was drilled into the posterior aspect of the condyle. The mandible is supported and the anchor is tapped home.
Once the anchor is securely tapped to place, tension is applied to engage the wings. This posterior tension serves to engage the anchors as they become anchored into the bone. The anchor is then properly secured so the non-resorbable threads can be used to help position the disc into the desired position.
Here we can observe tension applied to the non-resorbable threads to “seat” the anchor in the bone. Now the disc can be position and secured in place with the non-resorbable sutures.
This diagram illustrates the Mitek Anchor in place with the Nitinol wings imbedded into the condylar bone. The sutures serve to maintain the disc in the proper position. If the ligaments can be salvaged, they are allowed to remain in place and recover some function over time.
Viewed from the posterior, this diagram demonstrates suturing the disc is maintained by the Mitek Anchor. This attachment helps maintain the disc in the desired position. The remnants of the posterior tissue can be reattached. The wound is then closed with sutures.
There is one additional advantage to this surgical technique. The beginning etiology of dysfunction was a posterior movement of the condyle which compressed the disc tissue and began to alter the posterior lamina and posterior connective tissue. The procedure into the posterior aspect of the joint space causes a slight swelling which serves to force the condyle forward against the disc and front wall of the socket (eminence).It is necessary to maintain the forward posture of the mandible to ensure the condyle does not return to a posterior pathologic position. This may involve post-surgical orthotics and/or other corrections to ensure the proper mandibular – maxillary relationship is maintained.
This technique can be used to reposition a disc that has not been too destroyed and retains its structural integrity into a more physiologic relationship. The Mitek Anchor provides a method for securing the disc to the condyle, but the health of the disc, the loss of lateral or medial ligament attachment and the loss of the posterior connective tissue vary from patient to patient.This procedure corrects the effects of the inter-joint injury. The post-surgical swelling serves to reposition the mandible slightly anterior, but this may not be a permanent alteration when the swelling subsides. Additional treatments may be necessary to help maintain a physiologic position of the mandible.
A normal position of the condyle exerts an anterior-superior force against the avascular central portion of the disc. This force coincides with the physiological force vectors applied by the muscles of mastication. A condyle positioned superior or posterior superior exerts forces on the disc structures which cannot be physiologic. The disc structures compensate and undergo compensations to the condylar pressure. The disc may become displaced or dislocated as the condyle moves more posterior.
A dislocated non-recapturable disc may need to be repositioned to allow a more normal function of the mandible. The Mitek Anchor offers a moderately invasive surgical procedure to reattach a dislocated disc. The minimal swelling which occurs immediately after surgery helps maintain an anterior force on the condyle – disc assembly.
The surgery treats the effects of the injury. Post surgical corrections may be necessary to treat the cause of the dysfunction to maintain the proper forces upon the joint structures. This may involve post-surgical orthotics, prosthesis to maintain a functional relationship, or TMJ-orthodontics which approximates the dentition to maintain the functional mandibular – maxilla association.