Limited angular remodelling after in-situ fixation for slipped capital femoral epiphysis

BackgroundIn Sweden, most children with slipped capital femoral epiphysis (SCFE) are operated on with a single smooth pin or a short-threaded screw, allowing further growth of the femoral neck. Using the Swedish Pediatric Orthopaedic Quality registry, SPOQ, we investigated whether angular remodelling occurs adjacent to the proximal femoral epiphysis after fixation of SCFE using implants, allowing continued growth of the femoral neck.MethodsDuring 2008-2010 a total national population of 155 children were reported to the SPOQ registry. Following our strict inclusion criteria, radiographs of 51 hips were further assessed. The lateral Head Shaft Angle (HSA), the Notzli 3-point alpha-angle, the anatomic alpha-angle, and the Anterior Offset Ratio (AOR) on the first postoperative radiographs and at follow-up were measured to describe the occurrence of remodelling. Slip severity was categorised as mild, moderate or severe according to postoperative HSA.ResultsMean and SD values for the change in HSA were 3,7 degrees (5,0 degrees), for 3-point alpha-angle 6,8 degrees (8,9 degrees), and anatomic alpha-angle 13,0 degrees (16,3 degrees). The overall increase in AOR was 0,038 (0.069). There were no significant differences between the slip severity groups.ConclusionsWe found limited angular remodelling after in situ fixation with smooth pins or short threaded screws for SCFE. The angular remodelling and the reduction of the CAM deformity was less than previously described after fixation of SCFE with similar implants. Results about the same magnitude with non-growth sparing techniques suggest that factors other than longitudinal growth of the femoral neck are important for angular remodelling.