March 06, 2021
The temporomandibular joint (TMJ) is the joint that connects the lower jaw with the skull. This joint is unique as it allows the lower jaw to move in all planes. The free movement of the joint is due to the presence of synovial fluid, which allows the articular disc to move whenever any movement is done through the joint. The articular disc is nothing but a cushion between the part of the lower jaw bone that attaches to the skull (condyle) and the glenoid fossa (depression in the skull wherein the condyle moves).
Any deformity of the TMJ can be diagnosed by routine palpations and observing the extent of movements that a person makes in different directions. Sounds like clicking, popping, grating or crepitus can be heard, which give an idea about the extent of deformity. A dislocation of the articular disc due to improper bite, improper posture, abnormal habits, traumatic injury, etc can cause pain and inflammation in the TMJ. The area around the TMJ is dense with various blood vessels, nerves, salivary glands, lymph nodes, etc. This is why a surgical approach can be very tricky in this area. Hence, to resolve a TMJ disorder in a non-surgical and conservative way, various techniques have been developed. One of them is arthrocentesis.
Arthro refers to anything pertaining to joints and centesis is derived from a Greek word meaning puncture. This is a technique that is extremely minimal to perform. Its main goal is to remove all the inflammatory fluid that causes TMJ disorders from the upper half of the joint. This technique allows the disc to reposition itself once all the inflammatory fluid is removed. The result of this approach is such that it improves the mobility of the joint.
Arthrocentesis is performed with two needles that are placed strategically from the outside without incising any skin near the region of the TMJ. The first technique is a two-needle technique. Here, one needle is inserted in the joint space and other is placed either below or in front of it at a particular landmark which is also a part of the joint space. The basic idea is to inject a fluid with high pressure in one needle so that the flushing effect removes all the inflammatory fluid from another needle. This conservative treatment has been very efficient in eliminating pain and repositioning the disc.
The two-needle technique has its disadvantages though. Despite being a conventional approach, the second needle insertion may not be that easy, whereas the first needle is likely to cause pain. The second needle is positioned such that there is no damage done to the facial nerve that passes closely near the TMJ. Hence, a single-needle technique has also been developed. In this tecnique, the irrigating fluid is pushed inside the joint with less pressure and the goal is to completely fill the joint space. This breaks the bond between the disc and the factors that restricts the movement of the lower jaw. However, this technique too has its disadvantages as the inflammatory fluid cannot be completely removed. Instead, this fluid might further seep inside and cause swelling in that region. Even though it is minimally invasive, success rates of both two-needle and single-needle techniques are relatively same.
Modifications of the two conventional needle systems were made when two needles were inserted in a single cannula. This technique does not require another needle to be inserted as the same device can flush out the inflammatory fluid from another needle. This modified technique cannot be used in cases where the degenerative bony changes are severe which makes needle placement difficult.
The flushing fluid injected in the TMJ is called an irrigant. Normal saline, Ringer's Lactate, Sodium Hyaluronate are some of the commonly used irrigants. The total amount of irrigants used in arthrocentesis can vary from 50 mL to 500 mL. Once the lavage (flushing) is completed, the patient is given an injection of drugs that can counter post-operative inflammation. The patient is further advised to be on a soft diet for a few days. Physiotherapy exercises for the joint motility are taught and pain killers are prescribed as needed.
Arthrocentesis should not be performed in patients who present with an abscess (inflammatory-fluid-filled cavity) or cellulitis, bacteremia, osteomyelitis, coagulopathy and malignant tumours. These conditions can make needle insertion difficult and further complicate the already existing condition.
Complications after arthrocentesis are rare but have been reported in multiple aspects. Injury to the facial nerve and blood vessels during needle injection can occur. There might be partial hearing loss, vertigo and swelling in the region of the joint space. Mouth openin might be restricted for the first few days after surgery. There may also be an allergic reaction to the drugs injected. Perforation in the disc and repeated punctures due to improper needle placement are the most serious complications. Patients in the fifth decade of their life might find the recovery time prolonged. Moreover, the ones with a habit of teeth clenching (bruxism) show a longer duration for recovery. Despite the fact that the number of complications reported are multiple in number, one should remember that these are relatively rare occurences.
Arthrocentesis is a wonderful find in the medical field that can effectively heal the TMJ and allow better mobility of the lower jaw. It is able to resolve many debilitating conditions of the TMJ and should always be preferred over any other extensive surgical approach if possible.