This study aimed to investigate hypotheses related to critical-size bone defect reconstruction and compare the radiological parameters of Polymethylmethacrylate (PMMA) and calcium phosphate (CaP) bone materials. The research involved 36 healthy dogs divided into three groups (A, B, and C) with 12 animals in each group. Group A was treated with an intramedullary pin (IM-pin), group B was treated with PMMA in combination with an IM-pin, and group C was treated with CaP based bone graft material in combination with an IM-pin. The study assessed various endpoints at 14 th , 28 th , 45 th , and 60 th days post-surgery. The results indicate that regular radiological assessments were conducted in all three groups to evaluate fracture alignment and bone healing. On day 14 th postsurgery, all groups showed appropriate fracture alignment, with varying degrees of gap reduction. Group A (IM pin only) had minimal gap reduction, while groups B (IM pin + PMMA) and C (CaP + IM pin) showed slight gap reduction. By day 28 th , all groups demonstrated evidence of bone healing and callus formation, with groups B and C showing clearer callus formation in radiographs. In contrast, group A had considerable gap reduction due to increased immature callus formation and hyperplasia of surrounding tissues. On day 45 th , substantial bone healing and callus formation were observed in all groups. Groups B and C exhibited prominent callus formation, indicating rapid healing and gap filling, while in group A, radiographs showed growth on both sides but an unfilled gap. By day 60 th , fracture union was evident in groups B and C, while animals in group A treated with the IM pin only showed randomized luxation and an increased gap. It was concluded from the present study that radiographic results show the IM-Pin PMMA has proved to be the ideal implant material for femur bone fracture in dogs.