This retrospective study was approved by the local ethics committee. Written informed consent was waived due to the retrospective study design. Between August 2019 and March 2020, our institutional PACS system was searched for patients with MR arthrogram of the wrist and the corresponding medical histories were reviewed. Inclusion criteria were as follows: age over 18 years, detailed documentation of pain localization. Exclusion criteria were as follows: patients with a history of previous surgery at the wrist and bad image quality. Image quality was assessed by a radiologist (blinded) with more than 10 years of experience who was not involved in the readout. All patients were examined by experienced hand surgeons. Patients having localized radial-sided wrist pain over the STT joint were categorized as symptomatic.
MR imaging protocol
All patients had received an intraarticular injection of contrast media under fluoroscopic guidance according to our institutional standard protocol: A mixture of iodinated contrast media (Iopamiro 200 (200 mg/ml), Bracco Suisse SA, Switzerland) and gadoteric acid (Artirem (0.0025 mmol Gadolinium/ml), Guerbet AG, Zurich, Switzerland) with a volume mixing ratio of 1:2 was used. First, contrast media was injected into the distal radioulnar joint (1–2 ml) followed by the midcarpal joint (triquetral-hamate-capitate-lunate (four corner) interval) (2–4 ml).
All scans were performed using a MRI device with a magnetic field strength of 3 Tesla (Magnetom Vida, Siemens Healthineers, Forchheim, Germany). All patients were placed in a prone position, the arm extended over the head, the elbow joint in pronation and the wrist placed as close as possible to the isocenter of the magnet. A dedicated 16 channel wrist coil was used. The following sequences were acquired according to our institutional standard protocol: proton density SPACE (sampling perfection with application-optimized contrast using different flip-angle evolutions) in coronal plane (repetition time ms/echo time ms: 1000/55; flip angle 150°, voxel size 0.2 × 0.2 × 0.5 mm; turbo factor: 2, acquisition time: 5 min 12 s), T1-weighted turbo spin echo in coronal plane (repetition time ms/echo time ms: 700/12; flip angle 150°, section thickness 2 mm; acquisition time: 1 min 47 s), proton density turbo spin echo with fat saturation in coronal plane (repetition time ms/echo time ms: 3000/38; flip angle 150°, section thickness 2 mm; acquisition time: 3 min 35 s), T1-weighted turbo spin echo with fat saturation in sagittal plane (repetition time ms/echo time ms: 682/15; flip angle 150°, section thickness 2 mm; acquisition time: 4 min 23 s), T2-trufi (TrueFISP) 3D in axial plane (repetition time ms/echo time ms: 11.69/4.89; flip angle 30°, section thickness 1 mm; acquisition time: 2 min 51 s), T2-trufi 3D in coronal plane (repetition time ms/echo time ms: 11.67/4.87; flip angle 30°, section thickness 1 mm; acquisition time: 1 min 48 s).
Definition of ligaments
Four components of the STT ligament complex were identified. The rpSTL is located radial of the flexor carpi radialis (FCR) tendon and originates from the scaphoid tuberosity and inserts into the trapezial ridge (Fig. 2a–c). The ligament is best viewed and assessed in a coronal double oblique plane parallel to the long axis of the scaphoid (Figs. 3a, 4a–d). The pSTTC is located palmar to the rpSTL and forms the floor of the FCR tendon sheath. This structure is best viewed in sagittal orientation (Figs. 2a–c, 5a–d). The pSCL originates form the ulnar surface of the distal pole of the scaphoid and insert into the neck of the capitate. This ligament is best identified in coronal oblique plane parallel to the long axis of the scaphoid and in oblique axial plane (Figs. 2, 3b and c, 6a–d). The dSTTC forms a thin capsule and is best appreciated in axial orientation (Figs. 2, 5a–d).
Image analysis of the scapho-trapezial-trapezoid ligament complex was independently performed by two fellowship-trained musculoskeletal radiologists with 6 (blinded) and 13 years (blinded) of experience in musculoskeletal radiology, respectively. All sequences were available for the analyses. Both readers were blinded to any clinical information and each other’s reading results.
For each component of the scapho-trapezial-trapezoid ligament complex following features were assessed: visibility (yes/no), signal intensity (low signal intensity, increased signal intensity, striated), morphology (distinct/indistinct). Low signal intensity and distinct morphology was interpreted as normal appearance. Additionally, the presence of contrast media in the tendon sheath of the flexor carpi radialis (yes/no) and distension of the STT joint with contrast media was assessed (no distension, moderate/suboptimal distension, good/optimal distension). Overall STT joint degeneration, bone marrow edema, osteophyte and chondral defects were assessed using a four-point scale (0 = none, 1 = mild, 2 = moderate, 3 = severe).
For each component of the scapho-trapezial-trapezoidal ligament complex, the thickness was measured at the midportion of each ligament. For the pSCL, additionally, the width of the ligament was measured in the coronal plane.
Other causes for radial-sided wrist pain
Furthermore, a fellowship-trained musculoskeletal radiologist (blinded) who was not involved in the readout assessed other causes for radial-sided wrist pain based on the final MR report.
Quantitative data are given as mean values and standard deviations, qualitative data as median and range. Cohen κ was calculated to assess the interreader agreement regarding the qualitative parameters. κ between 0.0 and 0.20 was defined as poor, between 0.21 and 0.4 as fair, between 0.41 and 0.60 as moderate, between 0.61 and 0.80 as good, and between 0.81 and 1.00 as excellent agreement. Intraclass correlation coefficient less than 0.69 was defined as poor, ICC between 0.70 and 0.79 as fair, ICC between 0.80 and 0.89 as good, and ICC greater than 0.9 as high. The Mann–Whitney U test was performed to compare demographics, qualitative and quantitative imaging features between asymptomatic and symptomatic group. A p-value of less than 0.05 was defined as statistically significant. For the statistical analyses, a commercially available software was used (SPSS, Version 26, Chicago/IL, USA).