Superb microvascular imaging in the assessment of persistent synovitis after anterior cruciate ligament reconstruction

Abstract

Objective

The purposes of this study were to evaluate the prevalence of persistent postoperative synovitis three months after anterior cruciate ligament reconstruction (ACLR) using ultrasonographic superb microvascular imaging (SMI) and evaluate the intra-rater reliability of SMI synovitis and the level of agreement with other ultrasound synovitis assessment methods.

Design

Twenty-three individuals who had undergone primary ACLR took part in this prospective, IRB-approved study (11 females, 12 males; age=28.7±9.7 y; BMI=25.6±3.3 kg/m²). Three months after surgery, longitudinal and transverse ultrasound scans of the suprapatellar recess were performed at midline, medial to midline, and lateral to the midline. In addition to Power Doppler and B mode measures of synovitis and effusion, SMI was graded on two separate occasions at least two weeks apart. SMI intra-rater reliability was assessed with weighted Kappa analyses, and Kappa analyses were also used to assess the agreement between SMI synovitis and Power Doppler synovitis and B mode effusion.

Results

Three months following ACLR, 2 (8.7%) participants had no SMI synovitis, 9 (39.1%) participants had mild synovitis, and 12 (52.2%) had moderate synovitis. SMI synovitis grades demonstrated excellent intra-rater reliability (Kappa=0.93 [95%CI: 0.80, 1.06]) but demonstrated little agreement with Power Doppler synovitis grades (Kappa=0.29) or B mode effusion grades (Kappa=0.14).

Conclusions

Persistent postoperative synovitis was common with half of patients demonstrating moderate synovitis. SMI synovitis grading was reliable, but little agreement was noted between SMI and other ultrasound grades of synovitis or effusion suggesting that the different techniques are identifying distinct features of postoperative inflammation.