Beoordeling van dikte van subsynoviaal bindweefsel in carpaal tunnel syndroom

Carpal tunnel syndrome (CTS) is the most common mononeuropathy, yet the precise mechanisms driving its pathogenesis remain incompletely understood. A common histological finding is the non-inflammatory thickening of the subsynovial connective tissue (SSCT). Gaining a deeper understanding of this thickening process and its implications for in CTS is essential, as it may facilitate the development of more targeted interventions and treatments. This research project aimed to investigate the structural characteristics of SSCT thickness in the pathogenesis and progression of CTS. Specifically, we sought to expand our knowledge on the SSCT thickness in both health and disease, and to explore the effect of treatment on SSCT thickness. In Chapter 2, we conducted a systematic review of studies investigating SSCT thickening in both healthy and CTS-affected wrists, using both ex vivo and in vivo techniques. Notwithstanding the variability in diagnostic criteria between studies, SSCT thickening was consistently observed in CTS-affected wrists. Ultrasound, the sole in vivo technique employed, demonstrated potential for assessing SSCT thickness. Given that ultrasound is inexpensive and widely accessible, and considering that CTS may be primarily a pathology of the SSCT, developing a standardized method for measuring SSCT thickness would be highly beneficial. Future research should focus on standardizing diagnostic criteria and measurement techniques to improve result accuracy and comparability. Therefore, we evaluated the value of ultrasound in measuring SSCT thickness. First, we examined the reliability of ultrasound measurement of SSCT thickness in both healthy and affected wrists (Chapter 3). The results indicated that ultrasound is a reliable tool for measuring SSCT thickness, with good to excellent reliability outcomes for both intrarater and interrater assessments. Additionally, we assessed the reliability of a thickness ratio, previously proposed by other researchers to account for variations in hand size. However, this ratio proved unreliable, and we decided not to use this parameter in subsequent studies. In Chapter 4, we examined the association between SSCT thickness and the presence, absence, and severity of CTS. We also explored associations between SSCT thickness and subject characteristics. A significant association was identified between SSCT thickness and both the presence and severity of CTS. Furthermore, sex and body mass index were observed to be associated with SSCT thickness, suggesting that these variables should be considered as potential confounders in further analyses. No association was observed between SSCT thickness and age, testing side (dominant/non-dominant), body weight, height, symptom duration, menopausal status, or work-related hand use. These findings suggest that, in addition to its reliability, ultrasound-measured SSCT thickness has the potential to serve as a biomarker for CTS status and the severity. In Chapter 5, we explored the evolution of SSCT thickness over time, including in relation to therapy. This was the first study to examine longitudinal changes in SSCT thickness. Over the 12-month follow-up period, no significant changes were observed in SSCT thickness in healthy wrists, asymptomatic wrists in unilateral CTS, or CTS wrists that did not undergo treatment. However, in the wrists that eventually required surgery, we observed a significant increase in SSCT thickness in the six months prior to carpal tunnel surgery. This increase in thickness was not accompanied by changes in patient-reported outcomes, cross-sectional are of the median nerve, or electrodiagnostic findings. Given that the patient-reported outcomes were generally worse in the surgery group compared to the untreated group, the increase in SSCT thickness may indicate a phase of disease progression. Post-surgery, the observed increase in SSCT appeared to stabilize, though it did not return to normal levels. Lastly, we explored whether pre-treatment SSCT thickness could predict surgical outcome. No association was observed between pre-treatment SSCT thickness and surgical success, suggesting that a thicker SSCT does not necessarily indicate a poorer prognosis.