CT arthrography of the wrist using a novel, mobile, dedicated extremity cone-beam CT (CBCT)

Purpose

To evaluate the feasibility and intra- and interobserver agreement of CBCT arthrography of wrist ligaments, triangular fibrocartilaginous complex (TFCC), and to assess the sensitivity (SE), specificity (SP), accuracy (ACC), and positive and negative predictive value (PPV, NPV) of CBCT arthrography in the diagnosis of scapholunate (SLL) and lunotriquetral (LTL) ligament tears, TFCC, and cartilage abnormalities of the scaphoid and lunate with their corresponding radial surfaces (scaphoid and lunate fossa) using a novel, mobile, dedicated extremity CBCT scanner.

Materials and methods

Fifty-two consecutively enrolled subjects (26 M, 26 F, mean age 38 years, range 18–66 years) with suspected wrist ligament tears underwent CBCT-arthrography before normally scheduled MR arthrography.An extremity CBCT was used for imaging with isotropic voxel size of 0.4 × 0.4 × 0.4 mm³. Subsequent routine 1.5 T MRI was performed using a dedicated wrist coil.Two observers reviewed the anonymized CBCT images twice for contrast enhancement (CE) and technical details (TD), for tears of the SLL, LTL, and TFCC. Also, cartilage abnormalities of the scaphoid and lunate with their corresponding radial surfaces (scaphoid and lunate fossa) were evaluated. Inter- and intraobserver agreement was determined using weighted kappa statistics. Since no surgery was performed, MRI served as a reference standard, and SE and SP, ACC, PPV, and NPV were calculated.

Results

Intra- and interobserver kappa values for both readers (reader 1/reader 2; first reading/second reading) with 95 % confidence limits were: CE 0.54 (0.08–1.00)/ 0.75 (0.46–1.00); 0.73 (0.29–1.00)/ 0.45 (0.07–0.83), TD 0.53 (0.30–0.88)/ 0.86 (0.60–1.00); 0.56 (0.22–0.91)/ 0.67 (0.37–0.98), SLL 0.59 (0.25–0.93)/ 0.66 (0.42–0.91); 0.31 (0.06–0.56)/ 0.49 (0.26–0.73), LTL 0.83 (0.66–1.00)/ 0.68 (0.46–0.91); 0.90 (0.79–1.00)/ 0.48 (0.22–0.74); TFCC (0.72–1.00)/ (0.79–1.00); 0.65 (0.43–0.87)/ 0.59 (0.35–0.83), radius (scaphoid fossa) 0.45 (0.12–0.77)/ 0.64 (0.31–0.96); 0.58 (0.19–0.96)/ 0.38 (0.09–0.66), scaphoid 0.43 (0.12–0.74)/ 0.76 (0.55–0.96); 0.37 (0.00–0.75)/ 0.32 (0.04–0.59), radius (lunate fossa) 0.68 (0.36–1.00)/ 0.42 (0.00–0.86); 0.62 (0.29–0.96)/ 0.51 (0.12–0.91), and lunate 0.53 (0.16–0.90)/ 0.68 (0.44–0.91); 0.59 (0.29–0.88)/ 0.42 (0.00–0.84), respectively. The overall mean accuracy was 82–92 % and specificity was 81–94 %. Sensitivity for LTL and TFCC tears was 76–83, but for SLL tears it was 58 %. For cartilage abnormalities, the accuracy and negative predictive value were high, 90–98 %.

Conclusions

A dedicated CBCT extremity scanner is a new method for evaluating the wrist ligaments and radiocarpal cartilage. The method has an overall accuracy of 82–86 % and specificity 81–91 %. For cartilage abnormalities, the accuracy and negative predictive value were high.