Rationale:Elbow injury in children by improper treatment or a delay of more than 3 weeks could lead to old unreduced Monteggia fracture, which are difficult to manage. Conservative or normal surgical methods usually fail.Patient concerns:Herein, we present a 6-year-old boy with sustaining injury approximately 1 month to his left elbow. Activity in his elbow was restricted, and his ability to extend his wrist and fingers was impaired.Diagnoses:Type III Monteggia elbow fracture-dislocation consisting of radial head dislocation and malunion of the ulna associated with posterior interosseous nerve palsy were confirmed, which requiring surgical treatment.Interventions:A closed reduction was performed with hyperplastic scar tissues erased and the radial head relocated.Outcomes:Follow-up 4 months later showed satisfactory recovery of function.Lessons:Forearm fractures in children may be misjudged, and that early anatomical reduction rather than conservative treatment may be required.

Rationale:Inflammatory pseudotumor has been commonly reported in patients undergoing total hip arthroplasty (THA).Patient concerns:We reported a patient who had a massive intra-pelvic pseudotumour and acetabular bone defect underwent two-stage revision THA.Diagnoses:A new surgical strategy for pseudotumor after THA is performed.Interventions:Thorough debridement intra-pelvic pseudotumour via Smith-Petersen approach, bone grafting on iliac medial surface and plate-screw internal fixation were performed in the first stage, followed by revision of the loosened prosthesis to a cementless primary prosthesis in the second stage.Outcomes:A follow-up for 5 years showed satisfactory recovery of function.Lessons:This surgical revision is less invasive than conventional methods, resulting in a stable and well-functioning hip joint after mid-term follow-up for 5 years.