Chapter 103 - Temporomandibular joint

Question 1

Answer 1

Figure 103-1. Caudocranial view of the TMJ. a, Vertical ramus of themandible with the proximally located mandibular condyle; b, articulardisc interspersed between the mandibular condyle and temporal bone;c, temporal bone; d, coronoid process of the mandible.

Question 2

What is unique about the temporomandibular joint (TMJ) surfaces in horses?

Answer 2

Covered with fibrocartilage

Question 3

What structure divides the TMJ space into two separate synovial pouches dorsal and ventral?

Answer 3

Biconcave fibrocartilaginous articular disc

Question 4

what is the volume of the dorsal synovial pouch of TM?

Answer 4

discotemporal; ~5 mL volume

Question 5

what is the volume of the ventral synovial pouch of TM?

Answer 5

discomandibular; ~3 mL

Question 6

Which muscles are considered the primary masticatory muscles in horses?

Answer 6

Temporalis and masseter

Question 7

Answer 7

Figure 103-3. Anatomic landmarks for approaching the TMJ. a, Parotidoauricular muscle; b, parotid gland; c, facial nerve dividing into different buccal branches; d, maxillary vein covered by the parotid gland; e, transverse artery and vein; f, transverse facial branch of the auriculotemporal nerve of the trigeminal nerve.

Question 8

Answer 8

Figure 103-4. Side view of the TMJ. a, Lateral ligament; b, articular disc (the discotemporal–proximal and the discomandibular distal joint compartments are not shown); c, caudal ligament.

Question 9

What anatomical location is the TMJ close to?

Answer 9

Parotid salivary gland
maxillary artery and vein
facial nerve
transverse facial branch of thea uriculotemporal nerve

Question 10

what are the structures that can be found medially in TMJ?

Answer 10

temporohyoid joint, stylohyoid bone, guttural pouch, external
acoustic meatus, and tympanic portion of the temporal bone

Question 11

Which nerve innervates the skin and oral mucosa in the TMJ area?

Answer 11

Mandibular nerve (V-3)

Question 12

What are common signs of TMJ disease in horses?

Answer 12

Dysmastication and reduced feed intake

Question 13

What diagnostic imaging is primarily used for TMJ disease in horses?

Answer 13

CT-SCAN and MRI

Question 14

What are common treatments for TMJ disease in horses?

Answer 14

Nonsteroidal anti-inflammatory drugs and intraarticular steroids

Question 15

What surgical option is mentioned for TMJ luxation?

Answer 15

Manual manipulation under general anesthesia

Question 16

How is arthroscopy of the TMJ typically performed?

Answer 16

Under general anesthesia in lateral recumbency

Question 17

What is a key consideration during arthroscopy of the TMJ?
A. Avoiding the parotid gland
B. Completely severing the articular disc
C. Maximizing fluid distension
D. Using gas distention for clearer view

Answer 17

A. Avoiding the parotid gland

Question 18

Name the two ligaments that renforce the capsule of TMJ

Answer 18

Capsular reinforcement is provided by two ligaments, which are located on the lateral and caudal aspects of the joint (Figure 103-4)

Question 19

Which muscles are involved in the movement of the muscles?

Answer 19

Several muscles temporalis, masseter, lateral and medial pterygoid

Question 20

What are common complications following mandibular condylectomy?

Answer 20

Short-term masseter atrophy and malocclusion

Question 21

what is the landmark for distension and incision for arthrosocopy of TMJ?

Answer 21

After routine aseptic preparation of the surgical site, the caudal recess of the proximally located discotemporal joint pouch, which is usually easily palpable, is distended by injecting approximately 10 mL of Ringer lactate solution through a 20-gauge needle

Question 22

Describe the incision and entrace for arthroscopy

Answer 22

A 5-mm skin incision is made with a No. 11 scalpel blade next to the needle, followed by penetration of the joint capsule in a rostromedial direction with the blunt trocar of the 4-mm, 30-degree arthroscope. Care is taken not to injure the proximal aspect of the parotid gland that may extend into this region. An instrument portal is made adjacent to the arthroscope portal to assist in exploring the joint. Having an assistant performing sideway movements of the mandible, or placing a wooden block (or similar object) between the caudal cheek teeth and closing the jaw, facilitates exploration further. Separation of the joint spaces using a blunt instrument (such as an obturator) should be avoided as it creates substantial damage to the fibrocartilage. Fluid or gas distention can be used in TMJ arthroscopy, but the use of gas prevents the synovial villi from obscuring the surgeon’s view.36 The arthroscopic portal to the rostral recess of the discomandibular joint compartment is located immediately rostral to the mandibular head and ventral to the discotemporal joint space. Because this joint compartment is smaller than the proximal compartment, exploration is more difficult, but can be facilitated by using a smaller 2-mm arthroscope.

Question 24

What is a radical treatment option for some fractures or chronic sepsis involving the TMJ?

Answer 24

Mandibular condylectomy

Question 25

Name the conditions that may require mandibular condylectomy

Answer 25

fractures
luxations
chornic sepsis
OA - salvage procedure

Question 26

Partial mandibualr condylectomy and temporal bone resection - describe surgery

Answer 26

GA - LR
3cm radius semicircular incision directly over affected joint - enter with Metzenbaym scissor
Remove mineralized disc
Debride 10 mm of mandibular condyle and articular surgace
Close the joint in 3 layers (joint capsule, subcu, skin)
Levale 12 French Foley kt through original draining tract to flush the joint twice daily

Question 27

was the partial mandibular condylectomy and temporal bone resection successfull?

Answer 27

Yes, after 5 w AB and 2w AINS - Eight weeks after surgery there were no apparent abnormalities noted during mastication and a postoperative CT performed at 8 months revealed the presence of a pseudocondyle.

Question 28

Describe the surgical procedure of complete mandibular condylectomy

Answer 28

GA - LR
A 6-cm horizontal skin incision is made, centered over the TMJ, curving somewhat ventrally caudal to the mandibular condyle. The soft tissues are reflected ventrally to expose the joint capsule. The transverse facial artery and vein, as well as the auricular temporalis nerve –> ID and avoid
The TMJ is opened by a horizontal incision of the joint capsule (Figure 103-6). The periosteum on the condyle is incised vertically 2 cm distal from the joint space, and a periosteal elevator is used to reflect it both rostrally and caudally. An** oscillating bone saw, or a sharp osteotome, is used to create a 2-cm deep cut in the mandibular condyle 2.5 cm ventral to the articular surface. A chisel is inserted into the osteotomy and the lateral portion of the condyle is pried dorsally until it fractures. It is necessary to remove the lateral portion of the condyle before continuing the cut through the rest of the mandible under the condyle to provide room to introduce scissors to sever the capsular attachments. The oscillating saw is used to continue the osteotomy through the remaining axial portion of the mandible below the condyle. The condyle is grasped with large forceps and removed following scissor transection of any remaining joint capsule attachments. The articular disc is removed after severing its attachments with scissors. The bone edges are rounded with the help of a curette. The incision is closed in three layers:** the periosteum and joint capsule, the subcutaneous tissues, and the skin.

Question 29

What is the long-term prognosis following mandibular condylectomy?

Answer 29

Good with development of a pseudocondyle

Question 30

What is the most common anomaly reported in TMJ disorders in older horses?

Answer 30

Enthesophytes of the medial aspect of the mandibular condyle

Question 31

Answer 31

Cross-sectional CT image (A) and 3-dimensional CT reconstruction (B) of a coronoid process fracture arrows

Question 32

What condition is rare in horses and is most often related to penetrating wounds?

Answer 32

TMJ sepsis

Question 33

What is a common surgical treatment for TMJ luxation?

Answer 33

Manual manipulation under general anesthesia

Question 34

Answer 34

Figure 103-6. Arthrotomy into the TMJ for the purpose of mandibular condylectomy. The articular disc is shown (arrows).

Question 35

Answer 35

Figure 103-7. Radiographic appearance of the formation of a pseudo-condyle after unilateral condylectomy (arrows).