Pediatric Acetabular Fracture Registry: Long-Term Follow-Up and Outcomes

Introduction

This document is a protocol for a human research study. This two-phased study will be carried out in accordance with the applicable United States government regulations and the University of Utah and Primary Children's Hospital research policies and procedures. The first phase will consist of a retrospective cohort that will be contacted for follow-up data, while the second phase will consist of the creation of a prospective database.

Background and Current Clinical Data

Pelvic fractures, consisting of the pelvic ring and acetabulum, represent less than 0.2% of all pediatric fractures. Isolated acetabular fractures are estimated to represent 9.8% of pelvic fractures, while combined pelvic ring and acetabular fractures are estimated at 20%. Notably, these injuries occur as a result of high-energy trauma, most commonly during motor vehicle-related accidents.Despite the high-energy forces involved, pediatric patients are less likely to experience fracture-induced hemodynamic instability. This is due to factors such as limited displacement of fractures secondary to pelvis malleability, pelvic ligamentous strength, thickness of the pediatric periosteum and increased responsiveness of the pediatric hemostatic system. Consequently, the patient's life is more likely to be threatened by associated cranial, abdominal, thoracic, and neurological injuries, which occur in more than 60% of cases. Overall mortality rates are estimated between 3.2% to 18%. Acetabular fractures can also occur secondary to lower-energy mechanisms, such as hip dislocations during sports activity. The rarity of pediatric acetabulum fractures has resulted in limited high-quality data regarding clinical and patient reported outcomes (PRO), but the severity of these injuries indicates further observations are necessary.

The outcomes for pediatric acetabulum fractures are reported by a few small studies. Non- surgical and surgical management has resulted in acceptable clinical and radiographic outcomes. Past investigators have reported zero nonunions, one unplanned reoperation, and full return to activity in 18 patients. However, the study is limited by a small cohort and follow-up only to one year, which restricts the ability to observe the development of long-term complications such as arthritis or dysplasia. Other investigators have reported on 21 acetabulum fracture ORIF patients younger than 18 from 2001-2018, displaying favorable functional outcomes. However, only five patients had open physes, which severely limits the findings of the study to skeletally mature adolescents. Similar to adult acetabulum fractures, pediatric patients have a risk of post-traumatic osteoarthritis (PTOA). Additional complications of concern in skeletally immature patients are leg length inequality, hip dysplasia, and hip subluxation. These are secondary to a growth disturbance of the triradiate cartilage, which occurs due to osseous bridging across the cartilage or ossification of a physeal hematoma after injury. Growth disturbance has been reported in 14% of acetabulum fractures, while hip dysplasia has been estimated at 5%. However, the strength of both findings are limited by small sample sizes. Hip subluxation and dislocation are also associated with development of avascular necrosis (AVN) of the femoral head, osteonecrosis of the posterior acetabular wall, and sciatic nerve palsy. Hip reduction within 6 hours is associated with lower rates of AVN due to preservation of femoral head blood flow. While pediatric acetabulum fractures are associated with good outcomes, they are also associated with many potential complications that have lasting consequences for the patient. These outcomes will be best observed through long-term studies of the pediatric population.