Association Between Power Doppler Ultrasound Signals and Chronic Pain After Total Knee Arthroplasty: A Cross-Sectional Explorative Study

Abstract

Purpose

Some patients experience chronic postsurgical pain (CPSP) after total knee arthroplasty (TKA) despite the absence of clinical or radiographic abnormalities. Postoperative synovitis as a cause of CPSP after TKA has received limited research attention. This study aimed to investigate the relationship between synovitis after TKA and CPSP.

Patients and Methods

A total of 111 knees of 85 patients, with at least 1-year post-TKA follow-up, were assessed retrospectively and cross-sectionally. Power Doppler (PD) ultrasonography was used to detect the synovial hypervascularity associated with synovitis. The knee joint was divided into 15 areas, and PD signals were graded semi-quantitatively (0–3) in each area, the sum of which was defined as the total PD score. Clinical information regarding CPSP, including the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) pain subscales, was recorded. The relationship between pain and PD ultrasonography findings was accessed. Patients were divided into two groups (CPSP+ and CPSP− groups) based on pain severity. Clinical information, including PD ultrasonography findings and other possible causes, was compared between the groups.

Results

The WOMAC pain subscale was significantly correlated with the total PD score and maximum PD grade (r=0.3977, p<0.0001; r=0.2797, p=0.0029; respectively). The CPSP+ group had a significantly higher maximum PD grade and total PD score than the CPSP− group (median [interquartile range]: 2 [1, 2] vs 1 [1, 2], p=0.0001; 6 [2, 11] vs 2 [1, 4], p=0.0002; respectively). Multiple and logistic regression analyses showed that the total PD score was an independent factor for the WOMAC pain subscale (β=0.3822, 95% confidence interval [CI]=0.1460, 0.6184, p=0.00176) and CPSP (odds ratio=1.19, 95% CI=1.01, 1.41, p=0.0424).

Conclusion

This study indicated a possible association between the total PD score and chronic pain after TKA; however, further studies are needed to corroborate these findings.

Keywords:

• chronic postsurgical pain
• synovitis
• ultrasonography

Abbreviations

TKA, total knee arthroplasty; VAS, visual analog scale; PD, power Doppler; PPTs, pressure pain thresholds; BMI, body mass index; ROM, range of motion; SD, standard deviation; MRI, magnetic resonance imaging; PROMs, patient-reported outcome measures; WOMAC, Western Ontario and McMaster Universities Osteoarthritis Index; CPSP, chronic postsurgical pain; CI, confidence interval; ICC, intraclass correlation coefficient; IQR, interquartile range; TK, Tukey–Kramer; ANOVA, analysis of variance.

Data Sharing Statement

The datasets used and analyzed during the current study are available from the corresponding author.

Ethics Approval and Informed Consent

The study procedures were approved by the Ethical Review Board of our facilities (IRB numbers: Hata Prefectural Hospital, 31-280; Kochi university, ERB-105784).

Author Contributions

All authors made a significant contribution to the work reported, whether that is in the conception, study design, execution, acquisition of data, analysis and interpretation, or in all these areas; took part in drafting, revising or critically reviewing the article; gave final approval of the version to be published; have agreed on the journal to which the article has been submitted; and agree to be accountable for all aspects of the work.

Disclosure

The authors report no conflicts of interest regarding this work.

Additional information

Funding

The study did not receive any funding from commercial or non-commercial sources.