Evolution of the AO Spine Sacral and Pelvic Classification System: a systematic review

Abstract

OBJECTIVE The purpose of this study was to describe the genesis of the AO Spine Sacral and Pelvic Classification System in the context of historical sacral and pelvic grading systems. METHODS A systematic search of MEDLINE, EMBASE, Google Scholar, and Cochrane databases was performed consistent with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines to identify all existing sacral and pelvic fracture classification systems. RESULTS A total of 49 articles were included in this review, comprising 23 pelvic classification systems and 17 sacral grading schemes. The AO Spine Sacral and Pelvic Classification System represents both the evolutionary product of these historical systems and a reinvention of classic concepts in 5 ways. First, the classification introduces fracture types in a graduated order of biomechanical stability while also taking into consideration the neurological status of patients. Second, the traditional belief that Denis central zone III fractures have the highest rate of neurological deficit is not supported because this subgroup often includes a broad spectrum of injuries ranging from a benign sagittally oriented undisplaced fracture to an unstable “U-type” fracture. Third, the 1990 Isler lumbosacral system is adopted in its original format to divide injuries based on their likelihood of affecting posterior pelvic or spinopelvic stability. Fourth, new discrete fracture subtypes are introduced and the importance of bilateral injuries is acknowledged. Last, this is the first integrated sacral and pelvic classification to date. CONCLUSIONS The AO Spine Sacral and Pelvic Classification is a universally applicable system that redefines and reorders historical fracture morphologies into a rational hierarchy. This is the first classification to simultaneously address the biomechanical stability of the posterior pelvic complex and spinopelvic stability, while also taking into consideration neurological status. Further high-quality controlled trials are required prior to the inclusion of this novel classification within a validated scoring system to guide the management of sacral and pelvic injuries.

The Surgical Algorithm for the AO Spine Sacral Injury Classification System

“…1,2 Although many sacral classification systems have been previously proposed, most are mainly descriptive and limited in their assessment of sacral and pelvic morphology, and none have been adopted as a universal standard. [3][4][5][6] Therefore, in 2020, the Arbeitsgemeinschaft für Osteosynthesefragen (AO) Knowledge Forum Trauma published the AO Spine Sacral Injury Classification System. 7 The goal of the classification was to design a comprehensive system that could be easily and consistently applied by practitioners across different specialties to guide the treatment of these complex injuries.…”

“…Due to the anatomical location of the sacrum, which connects the lumbar spine to the pelvis, sacral fractures lie at the intersection of the fields of spine and trauma and often require a multidisciplinary team for treatment 1,2 . Although many sacral classification systems have been previously proposed, most are mainly descriptive and limited in their assessment of sacral and pelvic morphology, and none have been adopted as a universal standard 3–6 . Therefore, in 2020, the Arbeitsgemeinschaft für Osteosynthesefragen (AO) Knowledge Forum Trauma published the AO Spine Sacral Injury Classification System 7 .…”

Surgical management of lumbosacral and sacral fractures: roles of the pelvic and spinal surgeons

“…zone I = through the sacral area (50% of cases with 5.9% of neurological lesion of the lumbosacral trunk); zone II = through the sacral foramen (34% of cases with 28.4% of sacral plexus lesions); zone III through the sacral canal (16% of cases with 56% of neurological lesion with partial or total cauda equina syndrome). Further studies have shown that the rate of neurological impairment was lower with 1.9% in zone I, 5.8% in zone II, and 8.6% in zone III ( 17 ). Gibbons defined the neurological impairment linked to sacral fracture ( 18 ).…”

“…The AO defined a classification which integrates the sacral lesion and the pelvic lesion ( 17 ). This classification system introduces injury patterns in order of stability, while simultaneously taking into consideration the degree of neurological deficit; three types A, B, and C. Type A injuries have no impact on the stability of the posterior pelvic ring or spine, given their distant location from the weight-bearing axis.…”

“…The AO Spine Sacral and Pelvic Classification addresses the biomechanical stability of the posterior pelvic complex and spinopelvic stability, while also taking into consideration neurological status. Nevertheless, the AO classification has a moderate-to-strong reliability for fracture type and moderate reproducibility for subtypes ( 17 , 22 , 23 ).…”