Study design. The current research retrospectively included all consecutive patients diagnosed as anterior disc displacement (ADD) and were operated with Yang’s arthroscopic disc repositioning and suturing technique from March, 2014 to September, 2016 in the Department of Oral Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University, School of Medicine. This study was accomplished in accordance with the principles outlined in the Declaration of Helsinki, with an approval of the Ethics Committee of Shanghai Ninth People’s Hospital. An informed written agreement was obtained from all participants.
All arthroscopic procedures were performed by one senior surgeon (Chi Yang), with more than 40 years’ experience.
- Patients having at least one recent preoperative MRI (within 3 months),
- Having a minimum of two postoperative MRI scans (at least 6 months apart),
- Patients presenting with stages II-V (Wilkes classification)18,
- Patients operated with Yang’s TMJ arthroscopic disc suturing and repositioning technique,
- Adequate pre and postoperative clinical data.
Patients were excluded as study subjects if:
- Patients with septic arthritis or synovial chondromatosis,
- Psychological disorders,
- Joints operated before for any other TMJ problems,
- Insufficient or unclear MRI data,
- Missing clinical data or follow ups of patients.
The primary predictor variables. Different prognostic variables including gender, age, duration of illness, Wilkes staging, parafunctional habits, and splint/orthodontic therapy.
The primary outcome variables. Clinical outcomes [maximal interincisal opening (MIO), pain, diet, and quality of life (QOL)].
The secondary outcome variables. MRI-based radiological outcomes (disc position and condylar height).
Arthroscopic procedure13. Local anesthesia was applied in all arthroscopic surgeries that consisted mainly of four portals of entry. Following fossa portal entry, the arthroscope was introduced into the posterior recess, followed by thorough examination of the joint cavity to confirm the diagnosis of ADD. Under a complete arthroscopic visualization, the eminence portal was achieved, through which the coblation probe accessed the anterior recess for anterior release. Through a midway access point between the first two punctures, a 12-gauge needle was introduced into the upper joint space to penetrate the TMJ disc 1-2 mm ahead of the junction between the body of the cartilaginous disc and posterior retrodiscal tissue. A third transmeatal puncture was made, through which the custom-made suture needles were inserted. A specially-manufactured non-absorbable surgical suture material was passed from the 12-gauge needle and pulled out via the transmeatal portal with the help of the lasso- and hook-type grippers. Similarly, a second suture was made for better securing the disc position. A stabilizing splint was used for all patients after surgery.
Evaluation and workflow analysis of prognostic variables (Figure 1). All patients’ records including gender, age, duration of illness, Wilkes staging, parafunctional habits, and splint therapy, were reviewed and analyzed. Also, MRI data were reviewed for disc position and condylar height.
All preoperative patient data were input into a multinomial regression analysis to calculate a prognostic model for success or failure following the arthroscopic disc repositioning operations. The outcome items included:
- Maximal interincisal opening (MIO), (success ≥35mm),
- Pain scores measured with visual analogue scale (VAS), (success ≤3),
- Diet scores (success ≤3),
- Quality of life (QOL) (4 was indicative of success).
The outcomes of arthroscopic disc repositioning and suturing were categorized into four different subgroups namely, excellent, good, improved, and poor based on the analyzed postoperative data for more than two years.
An excellent outcome was confirmed when all 4 clinical parameters were fulfilled (MIO≥35, pain≤3, diet≤3, and QOL=4). A good result was defined if any of the 4 clinical parameters was missing, while if two or three items were not fulfilled, then an improved outcome was the scene. A poor outcome was defined when all the above parameters were not fulfilled.
Clinical follow-up assessment8. MIO was measured using a conventional ruler preoperatively and at 3, 6, 12, 24 months postoperatively. Pain was evaluated using a 10-cm VAS scale (where ‘0’ means no pain and ‘10’ representing the worst pain) preoperatively and at all postoperative follow-up intervals. The median VAS score at the final postoperative visit was compared with the preoperative VAS score. Diet was also evaluated using VAS from 1 (regular diet) to 10 (only fluids) and QOL assessmnt was done using a four point VAS scale from 1 (rest in bed) to 4 (ordinary daily activities) at pre- and postoperative visits.
MRI Acquisition and evaluation. MRI scans were obtained from a 1.5-Tesla imager (Signa, General Electric, Milwaukee, WI) with 3-inch TMJ surface coil receivers on bilateral sides. The parasagittal eight sections of T1-weighted spin-echo sequence scan from lateral to medial for each TMJ in the closed mouth position were first examined using a computer dataset (Y410P, Lenovo Computer, Beijing, China). The central image displaying the largest sectional area (usually the fourth or fifth slice) of the condyle was selected for tracing the reference planes and drawing the layouts of the joint structures by utilizing Adobe Photoshop CS5 (Adobe Systems, San Jose, CA). Besides, the linear measurements for condylar height and disc position were estimated by utilization of MB-Ruler estimating programming (Markus Bader, Berlin, Germany, precise to 0.01 mm). The construction of the tangent line at the posterior border of the ramus to assess condylar height was determined based on the method described by Markic et al.19 while the disc displacement distance was determined according to the method of Xie et al.20.
Assessment of condylar height. For every MRI image, three points, condylion (p), disc point (q), and incisura (G) were defined, and two linear measurements were drawn perpendicular to the tangent at the posterior border of the ramus. A tangent line (AB) was drawn at the posterior border of the ramus passing through two points, first: the most cranial and convex bulge on the back of the condyle, second: the most caudal and convex bulge on the back of the ramus. From line AB, two perpendicular lines CD and EF were drawn passing through the deepest point of the sigmoid notch (G) and the top point of the condylar head (p). The distance between lines CD and EF was defined as condylar height (Figure 2 & 3).
Measurement of disc position. Another point (point q) at the posterior most convex point of the disc was identified. A straight line drawn from point p to point q was represented as disc displacement/reposition distance relative to the condyle (Figure 2 & 3).
Statistical analysis. Data were analyzed statistically using SPSS software package version 25.0 (Armonk, NY: IBM Corp). A multinomial logistic regression was used to investigate the correlation between patient-specific factors (prognostic variables) and the surgical outcomes with the excellent outcome being set as a reference. All preoperative variables with a significant impact on the surgical outcomes were used in an adjusted regression model to address the possible confounders. Furthermore, Wilcoxon signed ranked test was conducted to analyze the association of disc position and condylar height differences as well as to evaluate the clinical outcomes pre- and post-operatively. Probabilities (p-value) of less than 0.05 were considered significant.