SLAC and SNAC Wrist: The Top Five Things That General Radiologists Need to Know

Wrist osteoarthritis (OA) is a common painful condition that affects the patient’s quality of life by limiting the range of wrist motion and grip strength. Wrist OA often results from scapholunate advanced collapse (SLAC) or scaphoid nonunion advanced collapse (SNAC). Early diagnosis of SLAC and SNAC is crucial because it affects treatment planning. Thus, radiologists should be able to interpret the early imaging findings. This pictorial review discusses the pathophysiology and the clinical symptoms of SLAC and SNAC and presents the imaging findings with emphasis on the proper imaging algorithm. Finally, it focuses on the treatment according to the degenerative status of each of these patterns.

Inter-Rater Reliability of Magnetic Resonance Imaging in Comparison to Computed Tomography and Wrist Arthroscopy in SLAC and SNAC Wrist

The aim of the study was to assess the inter-rater reliability of magnetic resonance imaging (MRI) in comparison to computed tomography (CT) and wrist arthroscopy in patients with scapholunate (SLAC) or scaphoid non-union advanced collapse (SNAC) as well as to evaluate a grading score of cartilage lesions. A total of 42 patients (36 male, 6 female) at a mean age of 45 years (range: 19–65 years) with a SLAC or SNAC wrist who had a preoperative MRI and CT scan as well as underwent arthroscopy of the wrist between 2013 and 2018 were included in this study. Cartilage lesions, as assessed by MRI, CT and wrist arthroscopy, were classified by two hand surgeons in three stages. Inter-rater reliability was evaluated using the Kendall Tau-b test as well as the chi-square test to analyze for trend. The correlation between cartilage lesions, classified by arthroscopy and MRI, was low. A moderate correlation between CT and arthroscopy staging was shown. The highest inter-rater correlation was found between MRI and CT staging. An additionally performed logistic regression showed that progression of cartilage lesions as shown in MRI scans correlates with a restriction of range of motion (ROM). The level of cartilage lesion may be more severely classified in an MRI than during arthroscopy. Arthroscopy remains the gold standard in detecting cartilage lesions and thus in the decision-making process of the definitive treatment in carpal collapse.

Retrospective Comparison of Capitolunate Arthrodesis Using Headless Compression Screws Versus Nitinol Memory Staples for SLAC and SNAC Wrist: Radiographic, Functional, and Patient-Reported Outcomes

Background Nitinol memory compression staples have been proposed as an effective alternative to compression screws for capitolunate arthrodesis (CLA) for scaphoid nonunion advanced collapse (SNAC) and scapholunate advanced collapse (SLAC) wrist. The purpose of this study was to compare the clinical outcomes of CLA for SNAC or SLAC wrist treatment using either compression screws or nitinol staples. Methods In all, 47 patients with CLA for SLAC or SNAC wrist with screws or nitinol staples were retrospectively identified. Primary outcome was fusion on radiographs and/or computed tomography. Secondary outcomes were hardware-related complications (HWCs) and other complications, range of motion, grip strength, and patient-reported outcome measures (PROMs), including Visual Analogue Pain scale; Disabilities of the Arm, Shoulder, and Hand score; and patient-rated wrist evaluation. Results Of the 47 eligible patients, 40 (85%) were included: 31 patients in the staple group and 9 patients in the screw group. The average age was 49 (17-80) years. There was an 89% union rate for the screw group and a 97% union rate for the staple group. Two patients had screw backout: one who went onto union after screw removal and the other who went onto nonunion after hardware removal. There were 2 (6.5%) HWCs in the staple group. One patient had staple loosening requiring revision and the other dorsal impingement requiring staple removal after radiographic union. In all subsequent cases, the staples were countersunk with no impingement. No significant differences existed between any additional outcomes. Conclusions We found no differences between nitinol staples and screws for CLA regarding HWCs or PROMs. Nitinol staples may offer additional benefits as a safe and effective alternative to compression screws for wrist fusions.

Rupture of Extensor Pollicis Longus Tendon Caused by Scaphoid Nonunion Advanced Collapse Wrist

We report the case of a 69-year-old male patient with extensor pollicis longus (EPL) tendon rupture associated with a scaphoid nonunion advanced collapse (SNAC) wrist. He could not actively extend the left thumb interphalangeal joint and visited our institution for an examination. Plain X-rays revealed advanced stage SNAC and an enlarged soft tissue shadow owing to dorsal ridge growth. The patient was diagnosed with EPL tendon subcutaneous rupture due to SNAC. During surgery, the EPL tendon was found to be absent, a proximal-type scaphoid nonunion was detected, and bone growth to the dorsal part of the dorsal ridge was observed. Considering that the EPL tendon rupture was associated with the bone growth, we performed scaphoid lunate advanced collapse (SLAC) reconstruction and extensor indicis proprius tendon transfer which needed a revision tendon surgery afterward. To the best of our knowledge, EPL tendon ruptures caused by SLAC or SNAC are considered rare and have not yet been reported.

A Reliability Study of Multiplanar Radiographs for the Evaluation of SNAC Wrist Arthritis

Background: Scaphoid nonunion advanced collapse (SNAC) is a common form of wrist arthritis, the treatment of which depends on the arthritic stage. The Vender classification serves to describe SNAC arthritis based on a single posteroanterior (PA) radiograph. The purpose of this study was to evaluate the intraobserver and interobserver agreement of the Vender classification, comparing multi versus single radiographic views. Methods: A retrospective review of patients with SNAC arthritis who underwent a proximal row carpectomy or a 4-corner fusion was performed. The included patients had 3 radiographic views of the pathologic wrist. Fifteen patients were analyzed by 5 blinded reviewers. Wrists were graded using the Vender classification first on the PA view and then using multiview radiographs. The intraobserver and interobserver agreement was determined using weighted kappa analysis. χ2 tests were calculated comparing the evaluation between single- versus multiview radiographs and determining a higher Vender stage. Results: Multiview radiographs demonstrated a higher intraobserver κw compared with single-view radiographs (0.72 vs 0.66), both representing substantial agreement. The average interobserver agreement was moderate (κw of 0.48) for single view and slight (κw of 0.30) for multiview evaluation. Evaluating multiview radiographs was 6.37 times more likely to demonstrate Vender stage 3 arthritis compared with single view (odds ratio = 6.37 [confidence interval, 3.81-10.64], P < .0001). Conclusion: Reviewing multiview radiographs more commonly yielded Vender stage 3 osteoarthritis classification. The decreased interrater reliability in the multiview analysis is likely related to the increased number of articular surfaces evaluated. Using a single PA view may underestimate the severity of arthritis present.