(50) Is the Temporomandibular Joint Direct Joint Loading Test Associated with Arthroscopic and Histologic Findings?

Abstract:

Background: Temporomandibular joint disorders (TMD) have been estimated to affect between 12-31% of adults worldwide, with a higher prevalence in women [1, 2]. The direct joint loading test is one component of the clinical exam, often performed in attempt to distinguish intra-articular disorders from extra-articular disorders. Although the direct joint loading test is advocated for by TMJ experts, the exam remains unvalidated and is not included in the diagnostic criteria for TMD [2-4]. The aim of this study was to assess the prevalence of positive pre-operative direct joint loading tests and report the associated: diagnostic imaging, arthroscopic, and histologic findings, after TMJ arthroscopy. We hypothesized that the direct joint loading test would be positive in patients with symptomatic articular disc disorders (stages II-IV) or immune-based arthritis; and would be negative in patients with disc displacement with perforation (stage V). We expected that patients who tested positive on the direct joint loading exam would more frequently demonstrate bone marrow edema, retrodiskal synovitis, and/or effusions on their pre-operative MRI reports.

Methods: This was a retrospective study of data from our TMJ Arthroscopy RedCap Surgical Registry, which to-date included 246 patients who underwent TMJ arthroscopy by our senior author (JPM), between 2021-2022. This study included 204 patients from the surgical registry, who had documented results for direct joint loading, imaging, and serology. All records included a post-operative diagnosis, detailed arthroscopic findings, and histopathologic analysis of a synovial biopsy; obtained during their operative TMJ arthroscopy. Basic statistical analysis was conducted using Redcap.


Results: Out of 204 patients included in this study, ~50% (n=103) of patients tested positive for direct joint loading of one or both joints, pre-operatively. The most common arthroscopic diagnosis amongst direct loading positive patients was articular disc displacement, without perforation (stages II-IV) for both the left and right TMJ at 31% and 35%, respectively. Disc displacement with perforation (stage V) was the second most common diagnosis of the left and right TMJ at 29.4% and 24.4%, respectively. The direct joint loading test had poor sensitivity and specificity for articular disc displacement at 51% and 53%, respectively. The test also has poor sensitivity and specificity for immune-based arthritis, evidenced by inflammatory infiltrates on histopathologic analysis, at 57% and 50% respectively. Approximately 11% of patients with joint loading positivity were found to have bone marrow edema or effusions on MRI (n=11). Synovitis was not reported on Radiologist’s MRI interpretations, however, was a frequently described arthroscopic finding (n = 61).

Conclusions: This was the first study to investigate direct joint loading positivity and associated post-operative arthroscopic diagnoses. This preliminary investigation demonstrated that the direct joint loading test had poor sensitivity and specificity for articular disc orders and immune-based inflammatory arthritis. While we expected direct joint loading positivity in patients with symptomatic articular disc displacement, the high prevalence of positivity in patients with discal perforation was unexpected.
The utility of the direct joint loading test remains undetermined. While positivity may suggest intra-articular etiology of TMD symptoms, further studies are required to establish the clinical significance of direct joint loading positivity and to establish the utility of the test in distinguishing between intra-articular and extra-articular TMDs.

References:
1. Valesan, L. F. et al (2021). Prevalence of temporomandibular joint disorders: a systematic review and meta-analysis https://doi.org/10.1007/s00784-020-03710-w
2. Schiffman, E et al (2014). Diagnostic Criteria for Temporomandibular Disorders (DC/TMD) for Clinical and Research Applications: recommendations of the International RDC/TMD Consortium Network* and Orofacial Pain Special Interest Group https://doi.org/10.11607/jop.1151
3. Burris, B et al (2023). Nonsurgical Management of Temporomandibular Joint Arthropathy https://doi.org/10.1016/j.cden.2022.07.003
4. Hossameldin, & McCain, J. (2015). Outcome of Office-Based Temporomandibular Joint Arthroscopy. https://doi.org/10.1016/j.joms.2015.06.180

Clinical photo of direct joint loading test positivity.

Arthroscopic image of a left TMJ with disc displacement and retrodiskal synovitis.

Arthroscopic image of a left TMJ with articular disc displacement. This photo demonstrates articulation of the articular eminence with inflamed retrodiskal tissue.