Figure 1

OUC grading systems. Grading of ossification according to the Ruohoniemi et al.[5] scale and a new scale developed in this study. Left side shows moderate ossification with separate center of ossification and the dotted line is the navicular bone. A separate center of ossification is generally located at a level that results in a grading of 4 or 5. Grading according to Ruohoniemi et al.[5]. Grade 0: No ossification, inclination sagittal. Grade 1: Ossification maximum to the distal - palmar level of interphalangeal joint space. Grade 2: To the level of proximal edge of the palmar distal interphalangeal joint space. Grade 3: To a level of the proximal edge of the navicular bone (dotted line). Grade 4: Extending above the navicular bone up to distal half of the middle phalanx. Grade 5: Ossification above distal half of the middle phalanx. New grading according to SLU (new): Grade 0: Ossification not extending proximal of the distal edge of the middle phalanx. Grade 1: Ossification extending between the distal edge of the middle phalanx to a level of proximal edge of the palmar distal interphalangeal joint space. Grade 2 Up to distal half of the middle phalanx. Grade 3: Ossification above distal half of the middle phalanx.