Diagnostic Accuracy of Integrating Ultrasound and Shear Wave Elastography in Assessing Carpal Tunnel Syndrome Severity: a Prospective Observational Study

Figures & data

Figure 1 Plots showing (a) mean CSAu and (b) mean CSAu-CSAo of MN among patients classified by EDT findings.

Figure 2 Plots showing (a) mean Eu and (b) mean Eu-Eo of the MN among patients classified by EDT findings.

Table 1 Measurements of CSA of MN Among Studied Groups

	Groups				P-value*
	Negative (n=8)	Mild (n=10)	Moderate (n=11)	Severe (n=19)
CSAu	7.75±1.39	11.6±0.52	13±1.55	17.6±7.35	<0.001
CSAo	5.5±0.93	8.3±0.94	7.3±1	7.7±1.7	<0.001
CSAu-CSAo	2.25±0.5	3.3±0.8	5.7±1.7	9.9±6.5	<0.001

Notes: Values represent mean ± SD; SD, standard deviation; *ANOVA test.

Abbreviations: CSA, cross-sectional area; CSAo, cross-sectional area in the pronator quadratus; CSAu, cross-sectional area at the tunnel inlet; MN, median nerve.

Table 2 Post-Hoc Analysis of CSA Measurements Among Studied Groups

a. CSAu		Severe	Moderate	Mild	Negative
Severe	Mean difference	—	4.63	6.03	9.88
	P-value	—	0.098	0.016	<.001
Moderate	Mean difference		—	1.40	5.25
	P-value		—	0.089	<.001
Mild	Mean difference			—	3.85
	P-value			—	<.001
Negative	Mean difference				—
	P-value				—
b. CSAu-CSAo		Severe	Moderate	Mild	Negative
Severe	Mean difference	—	4.22	6.65	7.70
	P-value	—	0.088	0.002	<.001
Moderate	Mean difference		—	2.43	3.48
	P-value		—	0.005	<.001
Mild	Mean difference			—	1.05
	P-value			—	0.028
Negative	Mean difference				—

Abbreviations: CSA, cross-sectional area; CSAo, cross-sectional area in the pronator quadratus; CSAu, cross-sectional area at the tunnel inlet.

Table 3 Measurements of E of MN Among Studied Groups

	Groups				P-value*
	Negative (n=8)	Mild (n=10)	Moderate (n=11)	Severe (n=19)
Eu	59.9±19.37	85.5±10.1	97.3±20.1	131.8±17.8	<0.001
Eo	33.2±8.8	39.9±10	34.6±8.9	41.8±9.8	0.05
Eu-Eo	26.7±12.2	42.7±10.3	62.6±16.8	90±16.7	<0.001

Notes: Values represent the mean ± SD; SD, standard deviation; *ANOVA test.

Abbreviations: E, elasticity; Eo, elasticity in the pronator quadratus; Eu, elasticity at the tunnel inlet; MN, median nerve.

Table 4 Post-Hoc Analysis of E Measurements Among Studied Groups

a. Eu		Severe	Moderate	Mild	Negative
Severe	Mean difference	—	34.5	49.3	71.9
	P-value	—	0.001	<.001	<.001
Moderate	Mean difference		—	14.7	37.3
	P-value		—	0.252	0.007
Mild	Mean difference			—	22.6
	P-value			—	0.079
Negative	Mean difference				—
	P-value				—
b. Eu-Eo		Severe	Moderate	Mild	Negative
Severe	Mean difference	—	27.3	47.3	63.3
	P-value	—	0.003	<.001	<.001
Moderate	Mean difference		—	20.0	35.9
	P-value		—	0.029	<.001
Mild	Mean difference			—	16.0
	P-value			—	0.068
Negative	Mean difference				—
	P-value				—

Abbreviations: E, elasticity; Eo, elasticity in the pronator quadratus; Eu, elasticity at the tunnel inlet.

Table 5 Validity Data of US Findings to Discriminate Between Patients with Severe/Moderate CTS and Those with Mild/No CTS

	Cut off	Sensitivity	Specificity	PPV	NPV	AUC
CSAu	13 mm	70%	100%	100%	66.67%	0.93
CSAu-CSAo	5 mm	83.3%	100%	100%	78.3%	0.98
Eu	94 kpa	90%	88.9%	93.1%	84.2%	0.93
Eu-Eo	56.1 kpa	93.3%	94.4%	96.5%	89.5%	0.95

Abbreviations: CSA, cross-sectional area; CSAo, cross-sectional area in the pronator quadratus; CSAu, cross-sectional area at the tunnel inlet; CTS, carpal tunnel syndrome; E, elasticity; Eo, elasticity in the pronator quadratus; Eu, elasticity at the tunnel inlet; US, ultrasound.

Figure 3 ROC curve of US measurements to discriminate between patients with severe/moderate CTS and those with mild/no CTS. (a) ROC curve for the CSAu-CSAo measurement. (b) ROC curve for the Eu-Eo measurement.

Table 6 Logistic Regression of the Cutoff Points of E and CSA of the MN with the Two Proposed Groups of Patients with CTS

	Eu-Eo and CSAu-CSAo cutoff points
	≥5 mm^2	≥5 mm^2	<5 mm^2	<5 mm^2
	≥56.1 Kpa	<56.1Kpa	≥56.1 kpa	<56.1 Kpa
Negative and mild (n=18)	0 (0%)	1 (5.6%)	0 (0%)	17 (94.4%)
Moderate and Severe (n=30)	23 (76.7)	5 (16.7%)	2 (6.7%)	0 (0%)

Notes: Data are presented as the number of patients, with percentages in parentheses.

Abbreviations: CSA, cross-sectional area; CSAo, cross-sectional area in the pronator quadratus; CSAu, cross-sectional area at the tunnel inlet; CTS, carpal tunnel syndrome; E, elasticity; Eo, elasticity in the pronator quadratus; Eu, elasticity at the tunnel inlet; MN, median nerve.

Figure 4 (a) Transverse US image of the median nerve (MN) at the carpal tunnel inlet. The landmarks are the scaphoid (SC) and pisiform (PI). (b) Transverse US image of the MN at the proximal third of the pronator quadratus (PQ).

Figure 5 (a) Sagittal US image of the median nerve (MN) in the carpal tunnel. The transducer is parallel to the nerve, and the landmarks are the distal radial epiphysis (RE) and the first (C1) and second (C2) carpal rows. (b) Sagittal US image of the MN in the pronator quadratus (PQ).

Figure 6 Algorithm proposed for the therapeutic decisions of patients with clinically suspected CTS.