Degree of disk displacement as a prognostic indicator in arthrocentesis outcomes: clinical and MRI correlation
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AIMS: Multiple studies have shown that arthrocentesis is an effective treatment for internal derangement of the temporomandibular joint. However, it is not known which patient groups will respond to this procedure. It is often difficult for surgeons to preoperatively the outcome of athrocentesis. This had led some researchers to analyze and evaluate specific variables which could possibly be used as prognostic factors to predict the outcome of arthrocentesis. None of those studies used the amount of disc displacement as a prognostic factor to assess the treatment outcome of arthrocentesis. Therefore, our study objective was to evaluate the amount of disc displacement as a prognostic factor for the outcome of arthrocentesis in patients with Internal derangement of the tempromandibular joint. MATERIALS AND METHODS: The study involved a retrospective review of the treatment records of 46 patients who underwent arthrocentesis of the TMJ by a single surgeon between 2010 and 2013. A prognostic factor evaluated for its effect on the treatment outcome of TMJ arthrocentesis in this study was the degree of disc displacement. For study purposes, patients were divided into two groups: 1) Success group, and, 2) Failure group. Patients were categorized as successful if they met the success criteria prescribed by the American Association of Oral and Maxillofacial Surgeons in 1995. MRI of TMJ was performed in two steps. Initially, oblique parasagittal sections were scanned with a 1.5 T MRI machine. The amount of disc displacement was analyzed from sagittal oblique views of the MRI scans in closed mouth positions by measuring the angle between the posterior band of the articular disc and the center of the condylar head. The disc is considered to be in its normal position when the thicker portion of its posterior band lies within ±10° on the 12 o'clock position. First, the condylar head was identified, and a circle was established to describe the outline of the anterior, posterior, and superior surfaces of the condylar head; this allowed separation of the condylar head from the neck region. Second, the center of the circle was identified and a vertical line was drawn from the center of the circle. The last step was to measure the degree of displacement from this vertical line to the posterior band of the disc. Findings were compared for patients in the two groups for the following variables: age (continuous), disc displacement (continuous), and gender (female or male). P-value were calculated for differences in continuous or categorical variables using a T-test or Pearson's chi-squared test, respectively. The mean MMO, pain and diet scores were also reported in the preoperative group and 12 months postoperative group by outcome status. Statistical significance was set at p < .05 based on a two-tailed test. SPSS was used for all statistical analyses (SPSS Inc, Chicago, IL, 1997). RESULTS: 46 patients with 46 joints were evaluated in the present study. Average age of patients was 31 years with arrange of 24 to 46 years. 35 cases (76.1%) were classified as successful and 11 cases (23.9%) were classified as unsuccessful based on the criteria described earlier. In the successful group, the mean MMO score was found to be greater at the 12 months postoperative interval when compared to the preoperative examination. In the unsuccessful group, the mean MMO score was also greater than preoperatively at the 12 months postoperative group but to a lesser extent than seen in the successful group. Pain level improved more in the successful group compared to the unsuccessful group. Diet scores showed improvement in chewing ability in the successful group but remain unchanged in the unsuccessful group There was a statistically significant difference between the two groups in the degree of anteriorly disc displacement. CONCLUSION: In summary, it has been shown that the degree of disc displacement, preoperative pain level, diet score, and MMO can be used as prognostic factors for the outcome of TMJ arthrocentesis. Future investigations should more carefully evaluate the validity of other variables. Identifying prognostic factors for the outcome on arthrocentesis will help with guiding surgeons in the planned evaluation of TMJ cases. More specifically, clinicians will be able to create tailored treatment modalities based upon prognostic factors.