Risser growth plate injury in unstable paediatric pelvic fractures: a multicentre retrospective study

Introduction: Unstable pelvic fractures in children are rare but severe injuries and are associated with high-energy trauma. Unlike adults, children have open growth plates, particularly the Risser growth plate (RGP), which is vulnerable to injury. The presence of growth plates, such as the triradiate cartilage and Risser's plate, represents point of vulnerability that determines distinctive fracture patterns, similar to those seen with Salter-Harris growth plate injuries. Lateral compression fracture is the most common mechanism and results in an irreducible crushing of the sacral alae, causing a rotational deformity. Both vertical and lateral compression displaced pelvic fractures require careful evaluation of the posterior iliac apophysis-associated injury. Failure to treat Risser growth plate injury (RGPI) can lead to severe long-term problems such as limb length discrepancy and scoliosis. This study aimed to determine how commonly RGPI occurs in unstable paediatric pelvic fractures, link it to specific fracture patterns and propose a subgroup type to improve treatment. Materials and methods: This multicentre retrospective study included 40 children aged up to 12 years with unstable pelvic fractures (AO/OTA 61B and 61C). The patients were treated between 1987 and 2022 at trauma centres in Italy, Argentina and Venezuela. We reviewed patient demographics, injury mechanisms and computed tomography (CT) scans to classify fractures using the AO/OTA system and identify RGPI. Statistical analysis was used to explore links between RGPI and specific fracture features. Results: Forty children (25 males; mean age 7.3 ± 3.6 years) were included. RGPI occurred in 26/40 patients (65%), with 19/21 cases (90.4%) in AO/OTA type C fractures. RGPI significantly correlated with complex posterior fracture-dislocations (p = 0.001) and AO/OTA type C injuries (p = 0.0007). Three RGPI types were identified: type 1 (minimally displaced), type 2 (avulsed RGP with sacroiliac [SI] joint disruption) and type 3 (bilateral lesions). In total, 11 of 13 patients (84.6%) with at least 2 years of follow-up developed deformities. Discussion and conclusions: RGPI is a common and critical part of unstable paediatric pelvic fractures, especially severe ones. In patients below the age of 7 years old with displaced and unstable pelvic fractures, the Risser's growth plates and posterior iliac apophysis are involved in 50% of cases. The Tile/AO classification, adapted to include concurrent injuries of the growth plates, offers a useful framework for treatment planning. Although the Torode and Zeig classification remains the standard, it is incomplete because it does not consider injuries related to the Risser growth plate. Our findings suggest that unrecognised or inadequately reduced RGPI causes severe, progressive functional deformities, such as limb length discrepancy, rather than mechanical instability. Although further prospective validation is needed, we hypothesize that anatomical reduction of these specific physeal injuries should be considered to prevent severe growth arrest. Our proposed classification seeks to improve upon traditional frameworks by incorporating this critical structure. Level of evidence: Level 4 (case series).