Maximum standardized uptake value of bone SPECT/CT as an indicator of pain and functional status in patients with symptomatic thumb basal joint arthritis

Purpose: Basal joint arthritis of the thumb is a common and painful condition affecting 16-33% of postmenopausal women and 5% of men [1, 2]. Although thumb basal joint morphology can be assessed by simple radiographs, the unique shapes of the trapezium and surrounding joints, the oblique orientations in both coronal and sagittal planes, and the complex shape of the articular surface make it difficult to consistently obtain optimal radiographs. In addition, radiographs may not fully reflect the severity of arthritis [3, 4]. These shortcomings are associated with the limitations of the radiograph-based Eaton-Glickel staging system, the most frequent method of staging for thumb basal joint arthritis [5, 6]. The purposes of this study were to quantitatively evaluate thumb basal joint arthritis using bone single-photon emission computed tomography/computed tomography (SPECT/CT) and to evaluate the relationship of SPECT/CT findings with patient pain and functional status [7, 8].

Methods: Findings in 53 hands of 30 patients diagnosed with symptomatic thumb basal joint arthritis between April 2019 and March 2020 were retrospectively reviewed. Visual analog scale (VAS) for pain, grip strength, and pinch power of both hands as well as patient-rated wrist/hand evaluation (PRWHE) were assessed. Thumb basal joint arthritis was classified by the modified Eaton-Glickel staging system using simple radiographs and CT scans of SPECT/CT [5]. Bone SPECT/CT imaging was performed approximately 3 hours after injection of 740 MBq (20 mCi) Tc-99m-hydroxy-diphosphonate (HDP) injection (Symbia Intevo; Siemens, Erlangen, Germany). The hand position for SPECT/CT imaging of the thumb basal joint was optimized using a specialized hand positioning device, which allowed subjects to maintain a single hand position for an extended period of time and permitted the clear visualization of all peritrapezial joints (Supplementary Figure A). This three-dimensional printed positioning device was designed to orient the hand to provide a true posteroanterior view of the peritrapezial joints [9]. Three dimensional volumes of interest (VOIs) were drawn on the coronal images of four joints, the thumb carpometacarpal (CMC), trapezium-second metacarpal, trapezium-trapezoid, and scaphoid-trapezium joints, and identified maximum standardized uptake value (SUVmax) (Supplementary Figure B).

Results: The 30 patients included 27 (90%) women and three (10%) men, with mean age of 62.9 ± 7.4 years (range, 47-75 years) and mean body mass index (BMI) of 26.0 ± 3.9 kg/m² (range, 19.1-32.9 kg/m²). According to the Eaton-Glickel staging system, 11, 17, 17, and 8 hands were classified as stages 0-I, II, III, and IV, respectively. The inter-observer reliability for determining the arthritis stage was moderate for simple radiograph (k = 0.411) and substantial for CT scans (k = 0.673). In 22 hands (41.5% of the 53 hands), the radiologic arthritis stages differed between simple radiograph and CT-based evaluations. The location of the SUVmax was mainly the thumb CMC joint, in 42 (79.2%) of the 53 hands. A binary categorical analysis (SUVmax cut-off 7.90) found that pain (p < 0.001) and PRWHE scores (p = 0.004) were significantly higher in hands with higher SUVmax. A multivariable linear regression model showed that SUVmax was the only factor significantly associated with pain VAS (B, 0.172; 95% confidence interval [CI], 0.065-0.279, p = 0.002) and with the variance in PRWHE scores (B, 1.378; 95% CI, 0.082-2.674, p = 0.038) (Figure and Table).

Conclusions: CT scans of SPECT/CT provided better inter-observer reliability than conventional simple radiographs for evaluating arthritis severity. A higher SUVmax in SPECT/CT was associated with more pain and greater functional disability of thumb basal joint arthritis. SPECT/CT may complement simple radiographs in evaluating patients with thumb basal joint arthritis.

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