110 Part I Chapter 4 Figure 8 Fifty-seven-year-old male patient with persisting pain 4 months after wrist trauma. X-ray (A) and CT (B) show ulna plus positivity and increased density of the lunate. Planar bone scan (C) and fused SPECT/CT (D) with increased uptake in the lunate (arrow) are also shown. T1-weighted MRI (E) with gadolinium shows partially missing contrast enhancement in the lunate (arrow) consisting with Kienböck’s disease. Carpal boss Carpal boss (CB) is a bony protuberance or accessory ossicle (‘os styloideum’) at the dorsal base of the second or third carpometacarpal joint. The abnormal configuration might develop painful degenerative changes with OA, associated ganglion cysts, inflamed bursa or extensor tendinopathy. Conservative treatment encompasses immobilization, nonsteroidal anti-inflammatory drugs or corticoid injections [36]. In patients with persisting pain despite conservative treatment, resection of the os styloideum or more extensive surgery with wedge joint resection, bone grafting and arthrodesis might be performed. Clarke, et al. reported that a positive stress test at the carpometacarpal joint together with a positive bone scan are good indications for a primary carpometacarpal arthrodesis [37].