Pathological Fractures of the Proximal Femur in Children and Adolescents Treated with LCP Paediatric Hip Plate.

PURPOSE OF THE STUDY Exploring the therapeutic potential of pathological fractures treatment of the proximal femur in childhood with LCP paediatric hip plate system according to the principles of AO. MATERIAL AND METHODS Six children with pathological fractures of the proximal femur and with an unicameral bone cyst have undergone surgery in our institution, in the period between June 2018 up until December 2020. All patients were young boys with a mean age of 11.83 ± 3.43 years. According to the classification of Delbet-Colonna, three of the fractures were Type IV - intertrochanteric fractures and three were Type III - basocervical fractures. ccording to the AO Trauma classification, one of the fractures was complete transtrochanteric multifragmentary (31-M/3.2.III), two were complete transtrochanteric simple (31-M/3.1.III), one was Complete basocervical multifragmentary (31-M/3.2.II) and two were complete basicervical simple (31-M/3.1.II). All patients have undergone open reposition and osteosynthesis with a 130° LCP pediatric hip plate system (DePuy Synthes Pediatric LCP Plate System). In four of the patients, one or two of the proximal locking screws pass through the growth plate, to ensure more stability. The anatomical correction of the proximal femur has been measured through the cervico-diaphyseal angle, consolidation of the fracture, the spontaneous reparation of the cyst according to the Capanna classification and cystic index, presence of avascular necrosis of the epiphysis, shortening of the extremity, and functional grading by the Musculoskeletal Tumor Society (MSTS) staging system. The Mann-Whitney (Wilcoxon W) test was used for data processing. RESULTS The mean timing of the follow-up after the surgery was 22 months (range 6-32). A radiographically supported consolidation of the fracture has occurred at an average timing of 4.8 months (range 3-6) in all patients. There is no clinical or radiological evidence of postoperative avascular necrosis in any of the patients. According to the classification of Capanna, in five of the six patients a spontaneous reparation of the cyst has occurred. In one of the cases, the reparation is classified as grade II with a pathological cystic index of 2.27. A postoperative correction of the varus fracture deformity of the proximal femur has been achieved in all children. The cervical-diaphysary angle of 112.50° preoperatively has been corrected to 137.17° (p=0.002). The achieved correction is lasting and the average value of the CDS at the final follow-up is 138.17° (p=0.794). Intraoperative correction, statistically equal to the CDA of the healthy side (p=0.942) is achieved with this operative technique. Data from the MSTS show functional correction on the third postoperative month with 38.33% of the norm (p=0.002) and 85% on the final follow-up (p=0.002). A contralateral distal femoral surgical epiphysiodesis by the method of Métaizeau has been used for the correction of the difference in the length of the extremities (with an average of 2.9 cm). CONCLUSIONS Osteosynthesis with an LCP paediatric hip plate system gives the opportunity for anatomical correction of the proximal femur with a low risk of avascular necrosis and achieving optimal functional results in pathological basocervical and intertrochanteric fractures in childhood. The use of 5mm plates and penetration of the proximal screw through the growth plate holds an increased risk of growth disruption. Key words: LCP paediatric hip plate system, pathological fracture, unicameral bone cysts, proximal femur.