For the present patients, the average age at surgery was relatively old, likely because trauma, which is common in young people, is less often an etiologic factor of TMJA, which is often caused by degenerative TMJ disease, commonly seen in elderly individuals. TMJA has been shown to occur slightly more often in males, with the same tendency seen in the present study, due to the fact that TMJA caused by trauma is generally more common in males. [14, 15] Trauma is the most common factor related to TMJA and several reports have presented cases of condyle fracture in young people. [16] In many countries, medical systems are generally in place that enable prompt surgical treatment through appropriate management in the event of trauma. That is very helpful for recovery of function, thus there were few cases related to trauma in the present study as well. In addition, widespread use of antibiotics has been effective to suppress aggravation of inflammatory diseases and it is speculated that the rate of incidence rate due to inflammation is decreasing. [7, 9]
In the present IPG cases, a TMF was mainly used as an intermediate insert. Many reports have stated that use of intermediate materials is less likely to cause recurrence of tonicity, though it is required that the material be easy to use during surgery and easily applied to gaps, as well as morphogenetic, factors that are also necessary for response to joint function without fragmentation or absorption. [17–19] Artificial materials have a risk of foreign body reaction and/or rejection, and a prior study found no significant difference in the possibility of recurrence among the different materials available8). Therefore, for the present patients, a TMF close to the surgical field that could be used during surgery relatively easily was employed. In both the GA and IPG groups, there were no cases of wound swelling or infection of the temporalis muscle during the postoperative course, thus a TMF was considered optimal even when considering situations in which it would be frequently used. An IPG procedure was found to be excellent in terms of low occurrence of relapse in this study. However, that with use of a TMF has a longer incision as compared to a GA procedure and is invasive and prone to scarring, thus GA was applied in some cases. [20–22] In recent years, the authors have tended to use IPG more because the authors place importance on the final results.
Various reports regarding appropriate gap size have been presented, among which several recommend removal of at least 15 mm of bone, thus the present cases were divided two groups based on that and evaluated. [23, 24] A larger gap allows for a better transition of the MIO as compared to before surgery, thus an operative procedure with a large gap size was found to contribute to change in MIO in the present cases. In a meta-analysis of several case reports, Junli et al. showed that inadequate resection mainly causes ankylosis recurrence or loss of range of motion. [24–26] However, several of the present cases in that group had a poor preoperative MIO, and the increase in trismus from preoperative measurement to that at 24 months after surgery showed a sufficient tendency to improve the condition. The necessity of gap size of at least 15 mm is reasonable based on previous reports as well as the present results. [27, 28]
Kaban et al. noted the importance of rehabilitation early after surgery and requirement of 12 months. [23] Consistent rehabilitation is largely dependent on patient motivation. Thus, it is important to fully explain the need for rehabilitation as well as surgery and provide appropriate support including pain control during rehabilitation after surgery to maintain a high level of motivation. For patients with low compliance, it is necessary for medical staff to devise helpful measures, such as preparation of a protocol that easily describes the postoperative schedule and rehabilitation menu, as well as an environment favorable to the patient for checking their progress. Another report noted that TMJ lavage therapy is effective when pain during rehabilitation interferes with continuation. [29] Although only 12 cases were assessed in the present study, a correlation between rehabilitation period and RMIO after surgery during a relatively long period of 24 months after surgery was found. Explanations regarding the importance of postoperative rehabilitation and effective patient education for TMJA treatment management can be major steps in this regard.
A relatively long-term clinical follow-up period of 24 months after surgery was used in the present study, which revealed that an emphasis on rehabilitation of 12 months or more leads to better maintenance of the MIO. Nevertheless, risks of occlusal changes and ankylosis recurrence remain in such cases, and it is important to use surgical and management methods that can inhibit those complications as much as possible. [27, 30–33] The present sample size was relatively small, thus it will be necessary to consider the need for a multicenter joint research project in the future. In addition, the postoperative follow-up period was 24 months, and MIO may decrease, and complications can occur after that time, making an extended observation period necessary.