Avascular necrosis after surgery of developmental dysplasia of the hip in children after walking age: incidence and risk factors

Introduction
Developmental dysplasia of the hip (DDH) is a common congenital anomaly in children. It includes a spectrum of anatomic abnormalities ranging from acetabular dysplasia to frank hip dislocation. Avascular necrosis (AVN) is one of the main complications associated with the treatment of DDH. It is a devastating problem that can lead to acetabular dysplasia and joint incongruity and cause premature osteoarthritis. The study aims to evaluate the incidence and risk factors of AVN after open reduction of developmental dislocation of the hip in children after walking age.
Patients and methods
Between the period of April 2014 and April 2019, a retrospective cohort evaluation of DDH cases was managed by surgery in the form of open reduction and pelvic osteotomy with or without femoral shortening. All grades of Tönnis classification were included. This study included 200 cases with an age range from 1 to 7 years, and the average age is 3.5 years at the time of last follow-up. The mean follow was 2.29 years, which ranged from 1 to 4 years. Plain radiography obtained in anteroposterior and frog lateral views after 1 year follow-up to diagnosis AVN as established in the literature.
Results
In this study, the mean time of intervention was 2.26 ± 0.97 years with an age range from 1 to 5 years. Twenty-six (13%) cases were managed only by open reduction and capsulorrhaphy, 174 (72.5%) cases had pelvic osteotomies, either Salter or Dega osteotomy, of whom 104 had femoral shortening and derotational osteotomy (59.77%). No AVN was reported in 159 (79.5%) cases, while AVN was evident in 41 (20.5%) cases.
Discussion
Incidence of AVN after open reduction depend on variable factor discussed in this study with total incidence of AVN 41 (20.5%) cases. This result is similar to other studies, with the incidence of AVN ranging from 15 to 30%. In the present study, the incidence of AVN increased 17 times in cases with postoperative immobilization in the hip spica more than or equal to 60° in the form of 21 cases showed AVN.
Conclusion
Postoperative hip immobilization in spica less than 60° as children with postoperative hip abduction more than or equal to 60° showed an increase incidence of AVN.