The onset, progress and factors influencing degenerative arthritis of the wrist following scaphoid fracture non-union.

BACKGROUND/AIMS: Scaphoid non-union causes osteoarthritis but factors associated are poorly understood. We investigated the rate of osteoarthritis after scaphoid fracture non-union, and if duration and fracture location influenced arthritis and its severity. METHODS: This retrospective cross-sectional observational study of 278 consecutive cases with scaphoid fracture non-union retrieved data on demographics, non-union duration, fracture location, dorsal intercalated segment instability (DISI), severity and distribution of wrist arthritis. Patient Evaluation Measure (PEM) and Quality of Life assessed impact on patients. Regression models investigated prediction of osteoarthritis by different variables. Time-to-event analysis investigated osteoarthritis evolution. Missing (MAR) data for the PEM and QoL was imputed and analysed. RESULTS: 278 patients, 246 males, aged 27.9 years (range 11 to 78 years), with a scaphoid fracture non-union confirmed on computed tomography (CT) scans (243) and plain radiographs (35) were reviewed. The interval between injury and imaging was 3.3 years (SD 5.9 years; range 0.1-45). The fracture was proximal to the ridge in 162, distal to the ridge in 83 and in the proximal 20% in 33. DISI (RLA ≥ 10°) occurred in 93.5% (260/278). Osteoarthritis was identified in 62.2% (173/278), and we classified a SNAC pattern in 93.6% (162/173). Of these, 100 (61.7%) had SNAC 1, 22 (13.6%) SNAC 2, 17 (10.5%) SNAC 3, and 23 (14.2%) SNAC 4. The mean duration in years for SNAC 1, 2, 3 and 4 were 2.5, 6.0, 8.2, and 11.3 years respectively. In fractures proximal to the ridge, 50% had arthritis in 2.2 years. Whereas in proximal pole, and distal to the ridge, 50% developed in 3.8 and 6.6 years, respectively. The PEM score was 42.8% (SD 18.9%) in those without arthritis and 48.8% (SD 21.5%) in those with arthritis. The mean QoL was 0.838 in patients without SNAC and 0.792 with SNAC. CONCLUSION: Scaphoid fracture non-union caused early carpal collapse, majority had osteoarthritis usually observed within a year following injury and occurred earliest in proximal waist fractures. Distribution of osteoarthritis (SNAC stage) may not always follow a distinctive pattern, as previously described.