TMJ Surgery

Question 1

The TMJ is known as a ginglymo diarthrodial joint. What does this mean?

Answer 1

There are 2 joint spaces which is why it is diarthrodial (a lower and an upper joint space).

The disc is held in place with fibres that come towards the front and attach to the lateral pterygoid muscle. And at the back, they attach around the external acoustic meatus, the back of the glenoid fossa and the back of the condyle.

(See diagram)

Question 2

What nerve supplies sensation to the TMJ?

Answer 2

Auriculotemporal nerve

Masseteric nerve

Both nerves are branches of the trigeminal nerves which is why TMJ symptoms, just like toothache, can be quite difficult to localise

Question 3

Describe dislocation

Answer 3

Dislocation occurs when the condyle slides down the articular eminence, moving past it, on opening. It then gets stuck anteriorly, in front of the glenoid fossa and the articular eminence (slightly rotated)

The masseter, temporalis and lateral pterygoid muscles generally pull the mandible up. The problem with this is that these muscles will go into spasm if the joint becomes dislocated. This means the upwards pull from these muscles is going to act to keep the condyle where it is (it’s going to stop the condyle from being reduced back into the joint).

As a result, the patient won’t be able to close their mouth (instead the mouth is left wide open)

Question 4

Describe the procedure for relocating a dislocated joint

Answer 4

The big powerful masseter, medial pterygoid and temporalis muscles are pulling upwards on the mandible as the joint has been dislocated and so these muscles have begun to spasm. So we need to do the opposite and push down on the mandible.

The dentist will need to stand in front of the patient, placing their thumbs onto the patient’s back teeth or the retromolar pads. The patient should be positioned below the dentist (as we want the dentist’s body weight on top of the patient). The dentist’s fingers should be placed on the patient’s chin.

We now have a situation where the patient is positioned upright but quite low down, the dentist is positioned upright and towering above the patient with their thumbs in the posterior regions of the lower arches and fingers positioned underneath the patient’s chin at the front.

In this position, the dentist will need to push the mandible down at the back (with the thumbs) and up at the front (with the fingers). In essence, the dentist will be rotating the mandible backwards (with the fingers) and down (with the thumbs) in order to try and reduce the TMJ.

The dentist will need something (a wall) or someone behind the patient as the patient will likely want to move backwards

Will be painful for the patient but the longer it is left, the more difficult it will become as the muscle spasm will become greater.

If the dislocation is bilateral, one TMJ should be relocated first, followed by the other.

If the dentist is not comfortable or 1-2 tries do not work, the patient should be referred to A&E to undergo the procedure under GA/sedation.

Question 5

Why do some individuals experience recurrent jaw dislocations? How can this condition be managed?

Answer 5

Due to the soft tissues around the joints being so loose that there is nothing to stop the joint from opening too wide and subsequently dislocating.

No stiffness in the joint or tendons, will lead patients to recurrently dislocate.

If an individual has a flexible jaw joint, they will be able to open it quite a lot, so occasionally these patients can also dislocate their jaw joints.

One of the ways to manage this is to stop the jaw joint from being used as much. This can be done by wiring the patient’s teeth together with upper and lower arch bars and elastic bands in between them to hold the teeth together.

This appliance is used for a week or so, allowing the jaw joint to get used to not being opened as much.

The muscles don’t get used as much and so they might contract down a little bit or get a little bit weaker. This means the joints and the muscles will get used to not opening, which will reduce the risk of recurrent dislocation

Question 6

Describe management technique for patients who experience recurrent jaw dislocation

Answer 6

One of the ways to manage this is to stop the jaw joint from being used as much. This can be done by wiring the patient’s teeth together with upper and lower arch bars and elastic bands in between them to hold the teeth together.

This appliance is used for a week or so, allowing the jaw joint to get used to not being opened as much.

The muscles don’t get used as much and so they might contract down a little bit or get a little bit weaker. This means the joints and the muscles will get used to not opening, which will reduce the risk of recurrent dislocation

Question 7

List the different TMJ symptoms a patient may experience

Answer 7

Pain

Clicking

Crepitus

Limited opening

Closed Lock

Open Lock

Dislocation

Question 8

What does clicking denote?

Answer 8

An intra-articular joint disorder

The cartilage disc (articular disc) is anteriorly displaced when the mouth is closed.

Once the patient opens the mouth, the condyle moves forward and the articular disc shoots backwards.

It is the movement of this cartilaginous disc back and forth that causes clicking

Question 9

What is crepitus?

Answer 9

Feeling of crunching within the joint. Sound resembles 2 bits of sand paper being rubbed against each other.

Continuous crunching, grinding due to rough surfaces being dragged over each other as the patient opens their mouth

Question 10

What does crepitus denote?

Answer 10

Degenerative joint disease (OA/RA)

Question 11

What can cause limited mouth opening?

Answer 11

Joint pathology

Muscle problems outside of the joint

Question 12

What is a closed lock?

Answer 12

Where the mouth is shut or the patient cannot open the mouth far enough, with a lot of resistance being felt as an attempt to open is made.

Feels like the mouth just won’t open.

Essentially, the jaw is closed and won’t open despite attempts

Question 13

What is an open lock?

Answer 13

Where the mouth is open or the patient cannot close the mouth far enough, with a lot of resistance being felt as an attempt to close is made.

Feels like the mouth just won’t close.

Essentially, the jaw is open and won’t close all the way down despite attempts

Question 14

What is dislocation?

Answer 14

Occurs where someone yawns or has been hit in the face, causing the jaw joint to actually be dislocated

The patient is left with the mouth as wide open as possible, with an inability to close.

Essentially, the jaw is left open and won’t close

Usually happens due to trauma in those with fit and healthy jaw joints or those who are elderly

Question 15

What is the relationship between TMJ symptoms and radiological abnormalities/pathologies of the TMJ?

Answer 15

The number of patients who have TMJ symptoms is very big. And the number of patients who have radiological TMJ abnormalities is also quite big, although not as big.

BUT the group of patients who have both (radiological abnormality and symptoms) is very small.

Not necessary that a patient presenting with TMJ symptoms will have a radiological TMJ abnormality and vice versa

This reinforces that just because a pt. has TMJ symptoms does not mean they will also have a radiological abnormality. And just because a pt. has a radiological abnormality does not mean they will also have symptoms.

Question 16

Where is the articular disc located?

Answer 16

Between the condyle and the glenoid fossa

Question 17

Briefly describe the anatomy of the TMJ

Answer 17

Condyle articulates with the glenoid fossa of the skull.

The articular disc is located in between the condyle and the glenoid fossa

Between the articular disc and the condyle, there is a lower disc space

Between the articular disc and the glenoid fossa, there is an upper disc space

The disc is held in place with fibres that come towards the front and attach to the lateral pterygoid muscle. And at the back, they attach around the external acoustic meatus, the back of the glenoid fossa and the back of the condyle.

The articular eminence is a bony slope/projection adjacent to the glenoid fossa

Question 18

Why do patients often report pain the ear when they have TMJ symptoms?

Answer 18

The external acoustic meatus is in very close proximity to the TMJ. This is why patients with jaw joint problems very often present with earache and vice versa.

Both the ear and the TMJ have the same nerve supply (auriculotemporal)

Question 19

What occurs to the TMJ during dislocation?

Answer 19

In order to dislocate the joint, the condyle has to slide down the slope of the articular eminence between the glenoid fossa and the articular eminence and get stuck anteriorly, on the other side of the articular eminence

Essentially the condyle is positioned forward of the articular eminence and slightly rotated

Question 20

Which muscles are responsible for closing the jaw?

Answer 20

Medial pterygoid

Masseter

Temporalis

Question 21

Which muscles are responsible for opening the jaw?

Answer 21

Lateral pterygoid

Mylohyoid

Suprahyoid (neck muscle)

Question 22

Why would a muscle spasm of the muscles that close the joint pose problems?

Answer 22

Pain in the joint will cause the MoM to spasm. This will stop the joint from moving. A muscle spasm of these MoM can therefore cause a closed lock

The MoM that close the jaw/joint are very big and strong muscles

And if we have big powerful muscles that are stopping a joint from moving, then it will be much more difficult to overcome that, because the muscles that open the jaw/joint are very small and fragile (not much strength in them).

So even if a patient tries as hard as they can, they will not be able to open the mouth if there is muscle spasm of the muscles that close the joint (close the mouth).

Question 23

Why can a muscle spasm of the medial pterygoid lead to a closed lock?

Answer 23

The medial pterygoid is 1/3 muscles responsible for closing the jaw/joint

These muscles are strong and powerful however a muscle spasm will impair their function, stopping the jaw joint from moving, causing a closed lock.

As we have big powerful muscles that are stopping a joint from moving, it will be much more difficult to overcome the closure, because the muscles that open the jaw/joint are very small and fragile (not much strength in them).

So even if a patient tries as hard as they can, they will not be able to open the mouth if there is muscle spasm of the muscles that close the joint (close the mouth).

Question 24

What is the function of the suprahyoid muscle?

Answer 24

1/3 muscles responsible for jaw opening

Located below the mandible

Attaches the mandible to the hyoid muscle (which is attached to the neck through other strap muscles)

When the suprahyoid and hyoid muscles pull, they pull the mandible down causing the jaw to open

Question 25

What is the function of the mylohyoid muscle?

Answer 25

1/3 muscles responsible for jaw opening

Question 26

What is the function of the masseter muscle?

Answer 26

1/3 muscles responsible for jaw closure

Question 27

What is the function of the lateral pterygoid muscle?

Answer 27

1/3 muscles responsible for jaw opening

Question 28

What is the function of the temporalis muscle?

Answer 28

1/3 muscles responsible for jaw closure

Question 29

Which cranial nerve supplies the TMJ?

Answer 29

Cranial nerve 5 (trigeminal nerve)

Question 30

Describe subluxation

Answer 30

Subluxation refers to a situation where the condyle goes over the articular eminence but doesn’t get stuck anterior to it. Instead, it is able to reduce back into the joint unlike in dislocation.

Does not usually pose any issues for the majority of patients

Question 31

Describe one situation where we may get subluxation of the TMJ

Answer 31

During the XLA of a lower molar tooth, in a young and fit patient.

The apical force applied to the tooth with forceps in order to extract it, is very often enough to subluxate the joint, but not dislocate it.

Can often feel it happening.

Question 32

What special investigations are required to diagnose a dislocation?

Answer 32

None.

Clinical diagnosis alone is sufficient.

Very obvious when the patient presents to the clinic-
Will see a great degree of mouth opening, difficulty speaking
Patient will report a history of them yawning prior to issue or an injury to the jaw.

Imaging is not justified therefore.

Question 33

What is the general management protocol for a patient who presents with a dislocation of the jaw?

Answer 33

History-taking-
Closed questions to ascertain the C/O, MH etc. or may need to rely on the escort the patient has brought with them.

Patient will report a history of them yawning or an injury to the jaw prior to dislocation

C/O pain, inability to close mouth or move jaw

E/O exam-
Will reveal a great degree of mouth opening
Inability to speak or close their mouth

I/O exam-
Check for any injuries within the mouth

No special investigations required, clinical diagnosis sufficient (no X-ray/CT scan)

Management-
The dentist will need to stand in front of the patient, placing their thumbs onto the patient’s back teeth or the retromolar pads. The patient should be positioned below the dentist (as we want the dentist’s body weight on top of the patient). The dentist’s fingers should be placed on the patient’s chin.

We now have a situation where the patient is positioned upright but quite low down, the dentist is positioned upright and towering above the patient with their thumbs in the posterior regions of the lower arches and fingers positioned underneath the patient’s chin at the front.

In this position, the dentist will need to push the mandible down at the back (with the thumbs) and up at the front (with the fingers). In essence, the dentist will be rotating the mandible backwards (with the fingers) and down (with the thumbs) in order to try and reduce the TMJ.

The dentist will need something (a wall) or someone behind the patient as the patient will likely want to move backwards

Will be painful for the patient but the longer it is left, the more difficult it will become as the muscle spasm will become greater.

If the dislocation is bilateral, one TMJ should be relocated first, followed by the other.

If the dentist is not comfortable or 1-2 tries do not work, the patient should be referred to A&E to undergo the procedure under GA/sedation.

Question 34

How can a patient with recurrent dislocation be managed?

Answer 34

Surgical intervention following a determination of the cause of recurrent dislocation-

2 approaches (make the glenoid bigger/steeper or make the glenoid smaller/shallower) which will depend on the cause of recurrent dislocation

If the issue leading to recurrent dislocation is that the condyle gets past the glenoid fossa and articular eminence too easily, we can make the articular eminence bigger. This will mean the TMJ becomes much more difficult to dislocate.

One of the ways we can do this is by making a little wedge cut in the articular eminence and then placing a little bone graft into that (bone may be taken from anywhere e.g., the hip, rib). This bone graft allows the articular eminence to become steeper, longer and bigger so that it is more difficult to dislocate

OR

We could make the glenoid shorter (reducing the height of the articular eminence), if the problem is that the condyle gets past the articular eminence but cannot move back due to its size.
This makes it easier for the dislocated condyle to be reduced back into the joint.

Question 35

Define internal derangement

Answer 35

A disruption the within the internal aspects of the TMJ (articular disc and surfaces) in which there is a displacement of the disc from its normal functional relationship with the mandibular condyle and the articular portion of the temporal bone.

Displacement of the disc can occur in the forwards or the backwards direction.

Essentially, an intra-articular joint disorder

Question 36

What is used to classify the severity of internal derangement?

Answer 36

Wilkes Classification (5 parts)

Question 37

Briefly summarise the 5 types of internal derangement outlined in the Wilkes Classification

Answer 37

I -
Painless clicking.

MRI will display a normal joint with a slightly anteriorly displaced articular disc

II -
Clicking with occasional pain, intermittent locking, headaches

MRI will show some minor changes to the articular disc including slight anterior displacement, beginning deformity and thickening of its posterior edge

III -
Frequent pain, joint tenderness on palpation, headaches and restricted motion (inability to open mouth fully).

MRI will show an anteriorly displaced disc with significant joint or disc deformity

IV -
Chronic pain, headaches and restricted motion (inability to open mouth fully, more severe than III).

MRI will show degenerative changes within the joint e.g., flattening of the articular eminence, a deformed condyle etc.

V -
Pain, crepitus, painful function. Pain is variable with some patients reporting pain and others reporting no pain (as the joint cannot move at all).

MRI will display gross anatomical deformities of the joint/disc, folding of the disc, perforation of the disc, presence of osteophytes etc.

Question 38

What is Wilkes Classification I?

Answer 38

An intra-articular joint disorder where there is clicking but no pain.

MRI will display a normal joint with a slightly anteriorly displaced articular disc

Question 39

What would an MRI display for a patient with a Wilkes I classification?

Answer 39

MRI will display a normal joint with a slightly anteriorly displaced articular disc

Question 40

What is Wilkes Classification II?

Answer 40

An intra-articular joint disorder where there is clicking with occasional pain, intermittent locking and headaches

MRI will show some minor changes to the articular disc including anterior displacement, beginning of deformity and thickening of its posterior edge

Question 41

What would an MRI display for a patient with a Wilkes II classification?

Answer 41

MRI will show some minor changes to the articular disc including anterior displacement, beginning of deformity and thickening of its posterior edge

Question 42

What is Wilkes Classification III?

Answer 42

An intra-articular joint disorder where there is frequent pain, joint tenderness on palpation, headaches and restricted motion (inability to open mouth fully).

MRI will show an anteriorly displaced disc with significant joint or disc deformity

Question 43

What would an MRI display for a patient with a Wilkes III classification?

Answer 43

MRI will show an anteriorly displaced disc with significant joint or disc deformity

Question 44

What is Wilkes Class IV?

Answer 44

An intra-articular joint disorder, where there is chronic pain, headaches and restricted motion (inability to open mouth fully, more severe than III).

MRI will show degenerative changes within the joint e.g., flattening of the articular eminence, a deformed condyle etc.

Question 45

What would an MRI display for a patient with a Wilkes IV classification?

Answer 45

MRI will show degenerative changes within the joint e.g., flattening of the articular eminence, a deformed condyle etc.

Question 46

What is Wilkes Classification V?

Answer 46

An intra-articular joint disorder, where there is pain, crepitus, painful function. Pain is variable with some patients reporting pain and others reporting no pain (as the joint cannot move at all).

MRI will display gross anatomical deformities of the joint/disc, folding of the disc, perforation of the disc, presence of osteophytes etc.

Question 47

What would an MRI display for a patient with a Wilkes V classification?

Answer 47

MRI will display gross anatomical deformities of the joint/disc, folding of the disc, perforation of the disc, presence of osteophytes etc.

Question 48

Describe the shared features of patients categorised as Wilkes I/II

Answer 48

These patients suffer from an intra-articular joint disorder caused by the slight anterior displacement of the disc in a closed mouth position.

But as the patient opens, the disc shoots to the back, where the joint is which results in a clicking sound.

Essentially, an anterior disc displacement with reduction

Question 49

Describe the shared features of patients categorised as Wilkes III/IV

Answer 49

These patients suffer from an intra-articular joint disorder caused by the anterior displacement of the disc in a closed mouth position.

As the patient opens, the disc does not move, remaining in its anteriorly displaced position. As the disc doesn’t move, it doesn’t reduce back into the joint either so there is no reduction.

And as the clicking only occurs when the disc moves backwards or forwards, there will be no clicking sound for these patients as the disc will not be moving backwards or forwards

Essentially, an anterior disc displacement without reduction

Question 50

What Wilkes Classification does a patient with a click typically fall under?

Answer 50

I or II

Question 51

What advice should patients categorised as Wilkes I-II be given?

Answer 51

Reassurance and education

Progression to Wilkes 5 (gross degeneration of the joint) is not inevitable

70% of patients who report TMJ symptoms or are classified as Wilkes I-II will get better with or without management (spontaneous resolution).

Only some progress to a higher classification with <10% of those in Wilkes I category progressing to Wilkes 5 within 10 years. This means 90% of patients will not get gross degeneration of the joint

Question 52

List the surgical options that may be undertaken to treat internal derangement

Answer 52

Can be categorised into-

Minimally Invasive procedures-

Joint injection

Muscle injection

Arthrocentesis

Arthroscopy

Open joint procedures-

Disc repair/positioning (meniscopexy)

Disc removal (meniscectomy)

Articular eminence/zygomatic arch procedures

Joint reconstruction procedures

Question 53

Describe the procedure of a joint injection

Answer 53

Essentially a joint wash out with steroids. Here, the idea is that we wash the joint out with steroids or inject steroids into the joint in order to reduce inflammation

Patient is asked to open and close their mouth a few times. The dentist checks for the joint space as the patient does this, marking it and placing steroid with saline in it via an injection into the marked area.

Question 54

What are the indications for a joint injection?

Answer 54

Very useful if a patient has internal derangement that is not resolving with conservative measures such as-
Spontaneous recovery
Rest
Exercise
NSAIDs medication
Provision of a mouth guard
Changing the way the patient eats

Pain

An MRI that gives some evidence of degenerative joint disease (arthritis)

Question 55

Describe the procedure of arthrocentesis

Answer 55

Essentially a joint wash out with saline.

This washes out the inflammatory products which are trapped in the joint space. And as we are flooding the joint space, what this may also be able to do is free up the disc and allow the disc to move back into a better position.

2 needles are placed into the joint space, both of which are in inserted in the upper joint space. One of them will then be attached to a syringe or a drip and then be flooded through with saline.

When the area is flushed through with saline etc. under pressure, we are able to-
Wash out debris
Clear the joint of inflammatory mediators
Divide adhesions
Remove restrictions on the disc by getting the disc moving under pressure.

Know that it is working when there is fluid being pushed in via 1 syringe, and clear fluid coming through the other syringe. This tells us that the syringes are in the right place.

After this, a little bit of steroid could be added into the joints in order to further reduce inflammation.

Question 56

What does arthrocentesis achieve?

Answer 56

Washes out debris

Clears joint of inflammatory mediators

Divides adhesions

Removes restrictions on the disc by getting it moving under high pressure (may become better positioned due to movement under pressure)

Question 57

What are in the indications for arthrocentesis (joint wash out)

Answer 57

Failed conservative management

Pain

Closed lock (where the patient cannot open their mouth as wide as they want to open it)

Patients with clinical or radiographic evidence of anterior disc displacement without reduction

Question 58

Describe the procedure of arthroscopy

Answer 58

Arthroscopy involves putting a small arthroscope into the joint.

This is done as a diagnostic technique in order to look at the joint space and the disc and the condition of the disc.

But we can also get an arthroscopic surgery such as an eminectomy in order to manage recurrent dislocation.

Another arthroscopic procedure is a meniscopexy which is used to pick up the disc and move it into a new position. The disc is sutured into this new position.

Involves the placement of 3 needles rather than 2.

Question 59

What is a meniscopexy?

Answer 59

An arthroscopic procedure which is used to pick up the disc and move it into a new position. The disc will be sutured into this new position.

Question 60

What is an eminectomy?

Answer 60

An arthroscopic procedure which is used to treat recurrent dislocations.

The articular eminence is made steeper/bigger using a wedge shaped bone graft or shallower/smaller using bone removal to prevent recurrent dislocations

Question 61

List the indications for an arthroscopy

Answer 61

Failed conservative management

Pain

Closed lock

Recurrent dislocation

Question 62

List the complications of arthroscopy

Answer 62

Swelling

Bruising

Bleeding

Pain

No improvement

Facial nerve palsy/weakness/damage (as we will be working close to the facial nerve, therefore can damage it)

Damage to structures of the ear (as we will be working close to the external auditory canal which is attached to the articular disc, we can perforate the middle ear, ear drum, external auditory canal which can lead to reduction or loss of hearing)

Question 63

List some open joint procedures

Answer 63

These procedures are more invasive and destructive forms of management, involve making an incision to access the joint

Meniscectomy (removal of the articular disc)

Meniscopexy (moving the articular disc back into the joint space)

Smoothening of join surfaces (removal of osteophytes)

Articular eminence/zygomatic arch procedures

Gap arthroplasty (to treat ankylosis, where the bones of one surface of a joint grow onto another surface of other bones so that there is no joint movement in the area)

TMJ replacement (joint reconstruction)

Question 64

List some complications of TMJ replacement procedures

Answer 64

Bleeding

Bruising

Swelling

Pain

Facial nerve damage

Damage to ear canal

Hearing loss (caused by damage to the ear canal)

Infection (if the replacement joint becomes infected, it will need to be removed)

CSF leak (caused by damage to the ear canal)

Implant failure (even if the replaced joint has been placed in with a good technique, after a couple of years of use, it will fail at some point as it is mechanical and therefore doesn’t have the capacity to take repeated loads as bone does. It will eventually get microcracks in the metal or the plastic cup will start to erode and it will begin to fail, needing eventual removal and replacement. Repeating these invasive surgeries risks more scarring, effusions etc.

Question 65

List the indications for TMJ replacement

Answer 65

Joint that is so grossly diseased that it is causing a malocclusion

Joint with extremely symptomatic arthritis in it

Question 66

List some non-surgical measures that patients with TMJ symptoms can take

Answer 66

Physiotherapy (exercise)

Therabite device (jaw rehabilitation device for trauma/cancer patients or those who may suffer from trismus, pushes the teeth apart by spreading the load all over teeth, allowing patients to improve their mouth opening)

Exercise

Low intensity CBT to manage stress, anxiety, thoughts about the pain

NSAIDs

Interim mouth guard

Question 67

What is a Therabite device?

Answer 67

Jaw rehabilitation device for patients

Often used for trauma/cancer patients or patients who may suffer from trismus

Has an upper and lower arch that goes into the mouth

Works to push the teeth apart by spreading the load all over the teeth, allowing patients to improve their mouth opening

Question 68

How are tongue depressors used to improve mouth opening and treat TMJ symptoms? What are the limitations to this method?

Answer 68

Essentially putting tongue depressors in between the teeth in a staged manner

A few are put in, and the patient is asked to hold the biting position for a few minutes. Then some more are put in, a few more minutes are allowed to pass and this continues.

However, this method is quite old fashioned and places all the pressure on the anterior teeth. If a patient has veneers, crowns or loose teeth, then this method may risk damaging these teeth or making them loose.